In the end, this means that I may have to dismantle my windmill.
As for the ceramic bearing, yes they are very expensive. The ones we have ran $60 a piece x 6 ..... and we are not exactly sure what the advantages are. A big difference will come from the fact that last year's bearings had seals and the ceramics don't. I did some very rough calculations and came they to a 2-10% increase in mileage.
Right now I am looking into exhaust and intake tuning, which could prove beneficial. I am also looking into heating the engine up with resistors since the engine is almost always cold and engines don't like to run when they are cold. I am looking at about 30,000 J, which should be enough to heat a small briggs block by 50-80 F.
We were thinking of routing the exhaust so it would go through the fins and then out the exhaust pipe. As for airflow, there is none. The engine bay is pretty well protected. There might be a little air going through the rear wheel, but I doubt very much.
Google "North American solar Challenge". Hints about how to handle the "panic" and "mad scrambles" on race-day may also help.
A major issue that we haven't solved yet is whether or not we can actually put all of the power on the ground. The reason I say this is that we will probably have about ~60 ft*lbs of torque on the rear wheel, which is way too much. Last year's car accelerated at about 2 m/s^2 and this year's car will be a minimum of 3 m/s^2, which is like a rocket. Most of the car's there probably accelerated at about 0.5 m/s^2 or less.
Goofy thought...
Add another wheel?
One with brakes that would drop down to the ground when the brakes are applied?
8" plastic kids scooter wheel with tube tires kind of wheel?
Okay you obviously don't need me distracting you with jealous vicarious commentary so get back to work!
Maybe a throttle feedback control with optical sensors aimed at the ground and the back tire. If the slip exceeds a certain level, have a solenoid pull back on the throttle.
Are pneumatic tyres a requirement?No, but the improvements would be only better if the road was perfectly smooth. The track that we race on is meant for dump trucks, so there are some decent cracks in the pavement. Putting solid tires on a car with no suspension would be crazy. You are right that it could be better, but it would make for a very heavy tire and the tires that we use are already really good. Rolling resistance of a steel wheel would be ~0.001. Our tires are about 0.002. We own a tire that can go as low as 0.0008, but it's $200 a tire.
Sure, acceleration is great, but I'd rather save at the pump. Kept driving a 50cc scooter around for quite a while @ 90MPG for that reason. Granted, it wasn't the initial reason, but that's another thread (likely for another forum too). :(Steve;
And so the difference shows there too - 90MPG vs 3000MPG - there's more than just the aerodynamics in that. LOL Not sure, call me crazy, but the engine having to zip along @ 9000RPM continuously to keep 27MPH may have had something to do with it... ???
Steve
And so the difference shows there too - 90MPG vs 3000MPG - there's more than just the aerodynamics in that. LOL Not sure, call me crazy, but the engine having to zip along @ 9000RPM continuously to keep 27MPH may have had something to do with it... Huh
One other question about your car I can't quite make out - the O2 sensor. Don't they have to be up to temperature to provide useful information to the computer? It would seem that 2 or 3 seconds wouldn't be enough to get it hot enough to give good data... ?
Sheesh... 3000 mpg?
For the building of the frame and body using the carbon fibre , could you post some of the pics over in the transportation area too Grin
"3000 would be astounding!! "
I agree. A lot.
Hope I did it right...
3000MPG is (in US measurements) -
4 miles per teaspoon.
12 miles per tablespoon.
308 miles per (ghurd's) coffee mug.
and
NY, NY to LA, CA... with 61 teaspoons left in a 1 gallon tank.
best we could get was 105 mpg consistently, 3000 would be astounding!!
Cheers;
I'm still working out the dynamics of the 18:1 compression ratio Grin
My MB 300TD is sitting nicely at 20:1 , I know it is supposed to be closer to 21:1, but with 177K on it and taxes coming due Undecided
Even ethanol auto-ignites around 15:1? not sure of that , never had the testicular fortitude to find out Shocked .
Having too much fun working with these numbers Cool
Thanks for the info on building this with CF!!QuoteFor the building of the frame and body using the carbon fibre , could you post some of the pics over in the transportation area too Grin
Umm... I wish my school's website would be accessible to you guys. It has about 130 pictures and 20 videos... Maybe if I have more time this week end.
As for the carbon fiber, the stuff is best stuff in the world. It's easy to make and requires no skills. Basically you mix the 2 part epoxy to the directions and add glue to your carbon fiber fabric. The hard part is not to get anything stuck the to carbon fiber, so for this problem you use lots of ceran (plastic) wrap. Anything made of the same plastic will not stick to the glue (like bubble wrap). Lexan is good for making shiny smooth surfaces.
For the cost, 1 yd of 60" wide is $20-50, so it's worth it for small projects. I'm not sure how much we have in the car right now, but it is probably 30yd^2 at least.
If you want to make a beam, basically wrap C.F. around some foam (we use the pink house insulation).
As for the compression ratio, you are right. Regular gas would ignite. Hence we are provided with iso-octane, which will not pre-ignite. Hence an 18:1 ratio is possible. We don't actually have an engine that is 18:1, but there are some older engines that run at 14:1. The downside is that 100- octane gas is $200 per gallon. You could run 93 pump gas in the engines with the lower compression ratios with no loss in power. At $200/ gallon, the cost benefit doesn't exist anymore. The competition usualy gives away the extra fuel, which usually amounts to a gallon per year. We probably have ~8 gallons in storage. I hope the stuff doesn't go bad :P
You have a drag coefficient of 0.7+, a bad engine, and bad tires.QuoteI'm still working out the dynamics of the 18:1 compression ratio Grin
My MB 300TD is sitting nicely at 20:1 , I know it is supposed to be closer to 21:1, but with 177K on it and taxes coming due Undecided
Even ethanol auto-ignites around 15:1? not sure of that , never had the testicular fortitude to find out Shocked .
Having too much fun working with these numbers Cool
I'm not an expert in this field, but there are a lot of issue with the higher compression. A smaller bore diameter would definitely be required ( we have a block with a 50cc cylinder ).
I can't wait til we get the transmission in the car and we build the cooled seat. The transmission will be a single friction plate clutch. We may not have enough force on the plates, so we may have to add teeth to the plates. This would require some timing challenges between the clutch engagement, the tire rpm, the engine rpm, and the tire rpm.
If anyone was wondering about the bearings, we have 6 full ceramic bearings in the three tires. Using full ceramic bearings instead of steel bearings with seals helps a lot. We spun our tires by hand, and they rotated for 16 minutes! The steel bearings only rotate for about 30 seconds. The bearing resistance is only about 1% of the rolling resistance. Hence our car should roll for about 2 minutes while coasting from 20 mph to 10 mph on flat ground. In reality, most of the course is at about a -0.1% grade, so I have coasted for 0.8 miles while going from 34 mph to 4 mph ;D The back curve on the track is about a 1% grade, which is very noticeable in these cars. We would have to fire the engine twice to get up the hill.
I keep coming back to something from the other post
I'd be willing to bet that regardless, the shortest, twiggiest guy on the team ultimately ends up becoming the driver.
While I'm on the subject, how much does driver skill play into this? Like percentage wise? Or is that a well known 'constant'?
Wondering, since it is almost an antique engine, are the antique efficiency boosters done?
(port & polish the head, intake, and exhaust, plus make sure the gaskets are not goofing up the works)
I do too, but I think there may be differences as to why. Mine is, cooling the seat is the one part of the car that I would have never bothered with. Unless we're talking extended runs here, which does not appear to be the case. Correct me if I'm wrong.
And even with extended runs (take NASCAR for example), they run for a few hours without anything like that (to my knowledge).
So why do it for this? Seems like the added weight of the water and associated electronics/components needed to cool the seat will offset your weight factor a fair amount...
You would be wrong about the nascar cooled thing. They have cold packs and various other things to keep the driver cool in the 140 degree F car. Our car is kinda of the same. I like to call it the easy bake over since it gets so hot. We did have an electric ducted fan in the nose of the car (from a model rc jet), which could produce ~50 mph winds inside of the car. Unfortunately, we had a significant crash while testing over Christmas, and it was destroyed. The run takes a minimum of 38 minutes to complete + fueling time, so you could be in the closed car for 50 minutes on tarmac on a 90 degree day.
As for the weight of the cooled seat, we are making the whole thing removable. The system may weigh 5-10 lbs, so we may remove it after we get some good runs in when we want to squeeze those last few mpg's out of the car. Last year's numbers were, in order: 650, 678, 69x, 776.59, 630, DNF. The 630 mpg was because I tried doing only 3 burns to get around the track, which meant my speeds went from 30-4 mph. The 776.59 came after we pumped the tires to 55 psi, emptied every last item out of the car, and removed the air filter. Also, the driver was the lightest of our 3 drivers, at exactly 130lbs with the helmet on... and she drove the car at a slower speed (24-10 mph). According to my excel mpg calculator, we should of been able to get ~ 850 mpg if it was driven slower.
Have you heard of, or already considered a NACA duct? It could introduce a flow of air into the cabin with the least disturbance to the external flow of air around the car. Unfortunately that would make the cooling speed-dependent, but if the bulk of the heat is coming from the engine and motors, then the sources of heat are speed-dependent too.
A reflective coating on the windshield would cut down on solar heating.
...and you're going to paint the car white, right? Tongue
Strange conflict between the '99 Olds and RP's 93 Deville... They're both in what I call the 'boat' class, particularly the Deville. It's interesting that they're comparable when feathered, but share no ground when 'dogged'. And the Olds is the smaller (and presumably lighter) of the two!
It's the one reason that even though my car is a stick, I don't kill the engine with the key during coasts. Too afraid of reduced engine life... ?Quote
I have turned my car off while coasting down big hills, for maybe 30 seconds at 40 mph. The downside is you loose your power steering and power brakes, which are nice for those white tailed deer and dodging the monster potholes...
I sometime put it in neutral, but it doesn't seem like it does much, especially since my car idles at ~1000+ rpm.
With the whole family piled in on a trip, the bmw would weigh 5500 + lbs, but you could get 31 mpg at 65 mph. At 55 mph, you can get 38 mpg.
The downside is you loose your power steering and power brakes,
Nice video... you boys are having way to much fun!
924 watts =1.2hp? How warm is the treadmill motor getting?
Once again... thanks for all the info you keep providing.
| Volts 92 89 91.2 91.2 92 65.5 77.5 78.5 78 78 63.5 63 66.7 66.5 69.8 69.2 73 71 75.9 79.5 79.5 83.5 88 87.5 92 91.6 96.7 96.4 96.5 100.8 75 53.6 62 44.7 43.7 | Amps 6 5.9 5.8 5.8 5.9 5.1 10.7 10.7 10.7 10.7 16.2 16.1 15 15 13.7 13.7 12.1 12.1 10.7 9.1 9.1 7.4 7.8 7.8 6 6 4.1 4.1 4.1 2 17.4 15 15.2 13.7 13.4 | Watts 552 525.1 528.96 528.96 542.8 334.05 829.25 839.95 834.6 834.6 1028.7 1014.3 1000.5 997.5 956.26 948.04 883.3 859.1 812.13 723.45 723.45 617.9 686.4 682.5 552 549.6 396.47 395.24 395.65 201.6 1305 804 942.4 612.39 585.58 | Gallons 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 0.007925162 | Seconds 160.22 187.64 165.05 174.87 161.79 248.25 133.57 135.47 132.11 134.76 110.2 110.32 114.58 113.97 115.81 115.24 120.11 122.76 128.84 141.81 138.94 148.97 140.75 145.64 159.05 159.74 177.1 177.94 178.76 201.2 134.77 116.5 169.59 163.75 | Joules/s 6529.280526 5575.150959 6338.208579 5982.280128 6465.920798 4213.983186 7832.00813 7722.162294 7918.562758 7762.847476 9492.933992 9482.608103 9130.051719 9178.918364 9033.082859 9077.762287 8709.69383 8521.679097 8119.538388 7376.922121 7529.302763 7022.362395 7432.478337 7182.925885 6577.311071 6548.90025 5906.952716 5879.067809 5852.099608 5199.410169 #DIV/0! 7762.271469 8979.582197 6168.531906 6388.527181 | Est. RPM 3036 2937 3009.6 3009.6 3036 2161.5 2557.5 2590.5 2574 2574 2095.5 2079 2201.1 2194.5 2303.4 2283.6 2409 2343 2504.7 2623.5 2623.5 2755.5 2904 2887.5 3036 3022.8 3191.1 3181.2 3184.5 3326.4 2475 1768.8 2046 1475.1 1442.1 | Efficiency 0.111239789 0.123928672 0.109810208 0.116343599 0.110457667 0.10430499 0.139315282 0.143120194 0.138681466 0.141463284 0.142585278 0.140742425 0.14418838 0.142990704 0.139292074 0.137415038 0.133441756 0.132649296 0.131607495 0.129038626 0.126427098 0.115776753 0.121515039 0.125022356 0.110427465 0.110424326 0.08831475 0.088458349 0.088958176 0.051017933 #DIV/0! 0.136286748 0.138091057 0.130626919 0.120606828 | Shaft HP 0.974006656 0.926541477 0.933352465 0.933352465 0.957773212 0.589432832 1.463215615 1.482095817 1.472655716 1.472655716 1.8151461 1.789737231 1.765387064 1.76009355 1.687325371 1.672821142 1.5585871 1.515886084 1.433007293 1.276531006 1.276531006 1.090287523 1.211156103 1.204274534 0.974006656 0.969771845 0.699573223 0.697402882 0.698126329 0.35572417 2.302678779 1.418661869 1.662869335 1.080565102 1.033258728 | Notes Full Bunny, 3 Lights Full Bunny, 3 Lights Full Bunny, 3 Lights Full Bunny, 3 Lights Full Bunny, 3 Lights Partial Throttle, 3 Lights Fully Bunny, 6 Lights Fully Bunny, 6 Lights Fully Bunny, 6 Lights Fully Bunny, 6 Lights Full Bunny, 10 Lights Full Bunny, 10 Lights Full Bunny, 9 Lights Full Bunny, 9 Lights Full Bunny, 8 Lights Full Bunny, 8 Lights Full Bunny, 7 Lights Full Bunny, 7 Lights Full Bunny, 6 Lights Full Bunny, 5 Lights Full Bunny, 5 Lights Full Bunny, 4 Lights Full Bunny, 4 Lights Full Bunny, 4 Lights Full Bunny, 3 Lights Full Bunny, 3 Lights Full Bunny, 2 Lights Full Bunny, 2 Lights Full Bunny, 2 Lights Full Bunny, 1 Lights Full Throttle, 10 Lights Partial Throttle, 10 Lights Partial Throttle, 10 Lights Partial Throttle, 10 Lights Partial Throttle, 10 Lights |
What happened on the data line, fifth from last?That was our peak power on the stock engine. I had to manually hold the throttle wide open so the governor wouldn't slow the engine down, hence there is no time value for it.
Is this with or without all the engine mods you told us about last month?100% Stock, less than 1 hour of run time on the engine.
It would make more sense if we were looking at 40% (engine) X 40% (motor) = 16% efficiency of the two coupled together. (or some variation of their proportions leading to the same result).The efficiency value you see is the calculated engine efficiency, including the losses from the treadmill motor @ 76% efficient. The calculation is really more like (Watts measured / 0.76) / power in gasoline.
..... Unfortunately, we did not have a good way to measure the rpm (even the oscilloscope was tried), so obviously the mill was running slower under load
Isn't it nice to have a project like this with nobody looking over your shoulder asking "what are the sources of uncertainty?".Yeah, I just finished a Physics lab course on optics and nuclear stuff, which we spent hours and hours figuring that stuff out.
... a carbon fiber cup holder ...
How much do you think you're losing with that belt flapping like it is?
Does that engine have a cast iron or cast aluminum flywheel? If it's aluminum then that may be why the pulsation is so strong.
If you look at the belt all by itself, it doesn't seem like it would take much energy to "flop" the belt back and forth like that?
Yes? No??
Huh Huh Huh
20x1.75..standard size. I kind of expected you to be using 20x1.5 for some reason.
pretty sure the opposite is true
Who told you wider tires have less rolling resistance? I'm pretty sure the opposite is true which is why skinny 10-speed tires rule for racing.
but if thats average current, ~5A seems WAY high. Is the coil warming up?I would say that is an understatement. After 5 min of running, the coil was measured at 150F. Current was 7 amps average. I can't recall the current draw when using the 4s Lipo instead of the 4s LiFE battery on the coil, but I think I remember the meter reading 140 watts instead of the 80 watts.... When we opened the gap on the points today to about 0.1", it was reading about 62 watts and the engine was running its best. Obviously, this gap was way too big.
Your points should be open most of the time, only briefly closing just in time to open again to fire the plug.
Insert Quote
The first video... that engine seems to smooth as silk!
"Rumble with 14 Robots!" Grin
We also found out that the big 134 tooth gear that we are using isn't really 134 teeth. Turns out it was 100 teeth... which means every calculation for the last 2 years is wrong...DOH!
If you had to hazard a guess, what kinda price tag you think this thing would carry if one were to eventually be able to purchase one at say, the local "TaylorP035's Custom Super Milage Cars" franchise
When are you going to apply the golf ball dimples? Wink8)
As I write this, I envision a trip to California from Virginia for less than $20.
I love the overhead shot.I was kinda curious myself to see what the shape was. The interesting part is that none of the cross sections actually look like a teardrop, just the over head view. With no wheels or tail cone, the drag coefficient was a low 0.079. It is currently calculated/estimated at 0.103, rounded up to 0.11.
I gave up on uploading photos to otherpower.com b/c it didn't work half the time and I would have to manually re-size them in MSPaint.
Did'nt I crop and save your Avatar to the OP/Board here?
It was a custom seat cushion that my mom made last year.
Moms that sew are cool....mine owns a quilt/fabric shop so everyone in the family has a nice quilt. 8)OKAY that might be a problem, where are you located?
OKAY that might be a problem, where are you located?
Yeah, she does quilts too, handmade, not with a machine.
I took a look at the website, then told wife about it while handing her a glass of wine ;D.QuoteOKAY that might be a problem, where are you located?
We're in Oregon so probably nowhere near you. She has a site (http://www.thefabricfarm.biz/) though, complete w/ an email newsletter. ;DQuoteYeah, she does quilts too, handmade, not with a machine.
My mom uses machines but she kinda has to since she does so many. She not only quilts her own stuff but other people's as well and rents out the quilt machine from time to time. And she teaches several sewing classes and has her own line of yarn.
taylor, have you tried getting your mom to drive the car? You should totally try to get her in it for at least a lap.
Is this thing televised by chance?
If you're fuel injected (and I think last count was that you were)
Uh, I am sure it was covered elsewhere, but these are 'bike size' tires right?
Oh, and I also sometimes see those over-pressured tires pop.I talked to several Laval students who went to Europe about the tires. They have the true tubeless radials over there. Even the top teams sometimes opt not to run them tubeless because one small rock will cause them to leak. They say that they pump them to 205 psi..... :o In Michigan, Laval ran tubes even though they have their own custom made carbon fiber tubeless rims. I would kill for a set of those. We could of had 2000 mpg with those with our stock engine and heavy car.
Looking at the pictures, I was surprised there seemed to be a number of vehicles with exposed tires and of those, none seemed to have "areo spokes" nor were the spokes covered in any way, such as this entry from Michigan Tech:
https://d1q9wbuypc40mm.cloudfront.net/lrdys76phdts7c_710.jpg
I see knuts at the Presque Isle (and other) time trials put 140PSI tubeless tires up to 175. Or 200. Carbon rims or not.
Can get that grade of tire for <$30 on sale.
Second car: Car from Hawaii. It got 197 mpg. You can probably guess that the squeaking as it drives by is not good.
What would your best guess be for mpg if I were to make just some quick and cheap 3 or 4 wheeler and toss your garden variety B&S on it with say... a centrifugal clutch?
Uhh, aint that called a 'go-kart'? LOL ;D
Steve
100-200 mpg if you ran the engine constantly, better of you could use a 50cc OHV honda.
... Supposedly a Crr of 0.0008 can be achieved...
Here is a video of our new flywheel dyno in action ;D Even though the stand and flywheel was already built, it took us a good 20+ man-hours to get the thing running and hooked up to the engine.
http://www.youtube.com/watch?v=IT1sqSlVmss (http://www.youtube.com/watch?v=IT1sqSlVmss)
The rpm's are in the description of the video. In general, they were between, 333 and 1000 rpm. At competition, we would shoot for about 333 rpm to 700 rpm. The loud clicking sound is from the brake rotor rubbing.
The flywheel and the correct gear ratio fairly accurately represents the load of the actual car, which should allow us to do some more testing and find out how to make the engine run the best. Starting the engine below ~400 rpm on the flywheel is a real chore (as you can see), since the starter only goes to about 230 rpm. Maybe I will kick up the voltage to 26v from the current 16v for next time.
After getting it going, we did 12 burns in a row to simulate half of the race. After crunching the numbers, the fuel efficiency came out to ~1400 mpg, which seems just right.
Are you seeing any weight reduction by machining your own head or ?
Do I see chatter on the rocker arm ends?
Guessing that you don't need cooling fins etc because the engine runs only for brief periods.
Also, Heli-coil is your friend. Use it anywhere you're threading a steel fastener into the aluminum.That's a great idea. Our smallest bolt is a 1/4-20 with over 1/2" of thread, so we should be fine, but on older blocks, we have stripped out some of the smaller threads.
When im talking with other steam folks, they dont seem to make the connection of compression ratio to volumetric efficiency.
As for salt...
Now we have 225+ psi of compression!
Tomorrow we plan on doing some dyno runs and seeing what the best the engine can do. We also want to test to see how much better the engine is at wider throttle than idle (with a mostly closed valve in carb, which hurts compression). If there is a huge difference, we can try the fuel injection to eliminate the restriction...
20,000 Views 8)Which head gaskets are you using? there are the standard ones and there used to be available (racing) head gaskets. In my younger days (when full service premium was 0.49/gal) we built them with these ultra-thin tin gaskets , if you have to stay with standard gaskets, grab one the is metal plated.
With our 0.060" head gasket, it should be about 12.3:1. 0.040" = ~13.5:1, and 0.000000" = 16:1. The compression could be higher if the volume calculations were wrong...
Before sanding the car, it is kind of like sticking your arm into the sharp needles of a pine tree....* cringe *
Let me set some things straight here....Thanks for re-posting those, with there being 9+ pages , it might be a stretch for others to go back through the earlier info.
Frank, I was confused at first, reading your comments. Are you picking up on comments made by MadScientist, in December?Sorry yes I was probably referring to a post several pages deep. and had posted it before I had checked it .
The carburetor we are using is sized for an engine in the ~15-20 hp range (my Timberwolf 250cc 4-wheeler has one just like it). Granted, the slide valve that lets the air in is much less than 25% open... at idle it's maybe 3-5% open. This proves why we should have an EFI system so we can lower the pumping losses, but this is why we try to run the car at maximum power (and the tests back it up).when you go to the EFI will it be a throttle body system of will you rework the head and opt for direct injection.
We bought a 50 cc carburetor and found that it didn't like the 148cc, even at idle. But we may use it next year on a de-bored engine
We can do anything to the engine we want, as long as we use the block in some fashion and the crank bearings stay where they are. We own a turbocharger that we may try using in the future.... You could do an Atkinson cycle too if you want. I'm not sure what a "positive pressure air induction" system is but I will look into it later today.the Atkinson cycle in such a confined engine block might be tough to achieve any benefits,
Funny you mention the Fred-Flintstone brakes... we actually tried it with our old car. It didn't really work but the thought of mounting some titanium to the bottom of the brake pad was suggested a few times to make some sparks :)
Since our starter battery is not regulated, I can put a bigger battery in the car with 2200 mah, but that will cost us another 100 grams or so and make things a bit more complicated for charging batteries (currently our accessories battery and starter battery are the same battery, so they can be swapped).No problem just don't let the driver eat for a couple of days or figure out how to have him toss his cookies after weigh in without being caught Just Kidding
Yesterday we did some more testing, even though it was dark outside and raining 8) ...
We did break our rear wheel mount yesterday....
I also found a bolt that was rubbing on our rear tire spokes....
The only thing that still worries me at this point is how much power we are using on the starter motor. ....
At the start of the 1485 run, our driver did a massive 20-25 ft burnout off the start line ;D That poor rear tire had zero rubber left on it by the end of the day,Did you get first place for best burn out as well? this ought to show the AA fuel dragster guys the you don't need 1500 HP to do a spectacular burnout.
... at next year's Supermileage Tractor-Pull.
(Of course it was FL that made the difference! B^>)
I guess it does get the project out on the internet if anyone was trying to search for it. There are only a handful of teams (probably less than 5), that have all of their information out in the open.
How much thought and discussion was there among the group about this? Were other team members blogging their experiences? Did others prefer to stay quiet? I'm not asking for dirty laundry, but I am wondering if the decision to write and publish your info was contentious - if so, how did you deal with it?
Jun 11
First day at the 2012 SAE Supermileage
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Good news, technical inspections and testing on the track have been completed. Early morning, we arrived at the site of the competition to prepare the vehicle for inspection. After a few adjustments, we went on an inspection, where apart from a few small modifications, all went well. In doing so, we were able to attack the track for a single round due to time constraints.
The evening ahead is dedicated to test the engine code as currently it does not achieve the desired speed for testing. We are still confident of finding the required values and thus be able to save during the tests tomorrow.
More news will follow.
Jun 12
Last day of the SAE Supermileage compétation 2012
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The final day of competition began with a vehicle preparation to go on the track: Warm up the engine, inflate tires and of course still some small problems to solve. We were finally able to make our first attempt in late noon. Air leakage through the head of the engine due to a candle that has ruined unscrewed however this test. The whole team is then lifted the sleeves and the problem was solved in time to give us a second time on the track. Everything indicated that this test would allow us to achieve superior results, but for reasons yet unknown the result was below expectations of the team. Finally, the all or nothing has been attempted in a last attempt to track that has not been successful because it is done in just two rounds to complete the competition.
The best recorded consumption of 1050 mpg combined score of the design competition has still allowed the team to get the third place in the competition. Despite the glitches encountered, the experience for our team mostly composed of new members has been most rewarding. We gratefully acknowledge the support of all our partners without whom none of this would have been possible.
Can you speed it up with a coarser mesh?The simulations would run faster with a coarser mesh, but that really isn't a big concern... it usually takes me ~3 hours to make a significant drawing change anyways, so I'm not really in a big hurry.
It's set to "auto" as I see on your full-size screen shot.
Sometimes you can sacrifice accuracy for speed when making early comparisons, then refine the winning choices later.
Inches and BTU's per second? Even the british don't use BTU's any more. ;)
Taylor is there a way you can camber the frame so that the body is stressed then when the driver's weight is added the straightens out and relieving the stress on the body.
Well, aren't some of the drag forces higher in some of the cases?Yes. I'm not sure why the turning drag forces are so high, unless they mean side loading instead. If they meant the drag forces going around a corner, my calculation figure about a 1.9 degree change between the air hitting the nose and the air at the tail (inverse tangent of 10 ft long car over 300 ft radius). I highly doubt they modeled that situation.
It seems more like they have "bought" space in the cabin at the "cost" of needing to find design changes to improve efficiency.
(sorry... gone on and on haven't I?) :-[Don't worry, I really enjoy what you guys have to say.
When you model the entire car, and run CFD simulations, do you only refer to the frontal area for Cd or do you also use the cross-sectional area in the horizontal plane, too?
| Cd Crr 0.1 0.0028 0.11 0.0027 0.12 0.0026 0.13 0.0025 0.14 0.0024 0.17 0.0021 0.21 0.0017 |
Sounds most reasonable to assume they have tabulated the forces in each of the 3 axes: One longitudinal drag, one laterally, one vertically.I think I'm going to have to go with you on this one. The 3 axis make the most sense. The weird part is that the 0 degree turning force is not zero. Unless they designed a car that is not symmetrical.... The track is only 28 % turns by distance.
If I had a 3 meter wide wind tunnel I'd love to put your car from last year inside it and try validating all the CFD you did on it!
Has a sum of all these factors been done that gives you confidence that the profile drag rules them all?
...we had the chance to drag race a v-8 powered lawnmowerLOL!
...But for now, I think we have achieved a fairly good result. ..
I was just being nit-picky on details before. I think you've achieved an EXCELLENT result!
Else, the mini starter motor was mounted, tested and broken :-\.
it would be nice if you could lay your hands on a portable coordinate measuring machine like this
Ha! At least one person here who shall be nameless (OK then, Ghurd), already KNOWS that hot glue is the solution to all the world's structural problems, and probably financial and energy problems too if we could just work out how to do it right! B^>
Rgds
Damon
My adviser feels the same way about hot glue. We even bought different grade of hot glue sticks, including some high strength stuff, that actually does seem to be stronger.
Taylor could your have used a revolve to cut feature to remove the interior volume? by creating a geometric plane 90 deg to the axis
I fear the 3D profile will have a lot to say about what happens in the wheel-well, not just a 2D profile.
Flow through spokes, (or is it on a solid disk) brake disks and calipers, that sort of stuff.
Not saying it isn't important - I'm worried about the amount of work needed to get a useful result.
Those sacrificial skirts (in your linked article) look like a funny thing to try, though. You would rather have the main skirt come down as close to the ground as you dare.I agree that their solution is not what we really want/need. Our wheel skirt is only 1/2" - 1" off the ground, depending on the tire used, inflation pressure and how much the frame decides to bend..... you can't really go any lower than 1", especially since the skirts are so long.... I can't count the number of times the car beached itself on a bump in the road/sidewalk. We have an idea where you take their secondary mini skirt frame idea/location and then take some stretchy material and cover the gap between it and the main skirt. This is something I have never seen before used on a SMV car or solar car, and I hope to prototype it in the coming weeks. The hard part is rigidly attaching the 2nd skirt/frame to the axle, which is made of carbon fiber and there is literally no clearance room for it.
I fear the 3D profile will have a lot to say about what happens in the wheel-well, not just a 2D profile.The question is "what is useful?".... getting a drag force isn't really on top of my list... especially since I can't set the car up properly and my original drag numbers from a month ago are all about a factor of 2 too high.... And yes, 2D airflows really don't serve the problem justice..... time to start wishing for a 3D hologram monitor for my laptop ;D
Flow through spokes, (or is it on a solid disk) brake disks and calipers, that sort of stuff.
Not saying it isn't important - I'm worried about the amount of work needed to get a useful result.
Where did you apply the vacuum?
A cold wet-layup with no vacuum will be heavier, and ultimately even more work than a bagged mold (done correctly) because you will be sanding sanding sanding anyway.
Or before attempting to make another male part on your male mold get some white shrink wrap like they use to wrap boats and escalators for shipment bag your bare male mold then heat shrink until the desired smoothness is achieved
Your channel has more views than some episodes of Top Gear (which are getting suggested by Youtube in the right-hand bar now). Congrats!Thanks! I have over 200 videos of all the fun things I do, so I guess the total should be fairly large. My most viewed video is one right after we port and polished the intake on a stock briggs engine.
How about some of the AFB's in your area for a nice long straight runway?We were thinking Presque Isle State Park, which is concrete and 13 miles around with a speed limit of 25 mph.... It would require some special arrangements.
I like the high-tech cellulose-based multi-legged temporary support structures (ie wooden stools)!LOL!
Rgds
Damon
Your top shell is looking good, but! and I'm not trying to be too critical but wouldn't a drop sheet of some sort on the floor have been a good idea? I think can see an outline of resin on the floor all around the model, that stuff is hard to get up. About the only way I have found was after it is dry is to grind it.Yep.... I used a hammer and a chisel to get the carbon strands that were glued last time. Last year, we put down a 12'x10' sheet of plastic, but all of the glue just migrated to the edge of the sheet, so there is now a clear outline of the sheet on the floor. It also made it extremely slippery (wet glue on plastic) and people fell down multiple times. A DA sander with 60 grit should take care of anything left over.... but we will hold off on that until we are done with the carbon. After the body is done, we have to glue in the frame rails, roll hoop, steering assembly, front wheel covers/stays, and possibly an engine mount (still thinking if we should go with an aluminum sub-frame or just use some 3/4" round or square C.F. tube stock.)
I can't see the release film all the way around. It's visible on the wheel "pants" but nowhere else. Problem?;D The clear spots are actually packaging tape to hold the larger green sheets on. I would say ~30% of the surface is covered in 2" wide packaging tape. The glue doesn't stick to the back side of the tape. We ended up doing the entire nose of the car with tape, since the green stuff doesn't lay down very well on two axis curved surfaces. We liked to compare it to numerical integration....
Cardboard on the floor instead of plastic sheet? Surely you can find a few empty pizza boxes, Mister Pizza Man!Maybe,.... could be a little greasy, hence still slippery. I have worked in fast food places with cardboard boxes covering the floor, and it does help some.
Will the bottom lay-up be one big piece like the top, or will you try covering the wheel fairings separately from the lower shell?Probably not. We can mostly likely get the insides of the wheel skirt, the bottom, most of the nose, and the rear wheel skirt in one piece, but the sharp edges+ curves of the wheel skirts/fairings would be impossible to drape the carbon fiber over all the way around. The lower part of the wheel skirt on the outside is going to be interestingly non-structural for this car, unlike out last car. The belly of the car and upper corners above the side windows need to be decently stiff. If it is as strong/stiff as the cardboard in a cereal box, then I say it should be good enough. Mounting the windows to a floppy surface is difficult, as we found out last year. The bottom of the car will have our pre-made frame rails laminated to it, and we are counting on the carbon fiber
the shape is vaguely orca like.Mother nature knows best. We think the new design will be ~40% more aerodynamic than last year's car. I think the design gets close, if not rivals the best cars in the European competitions. 30% of this increase comes directly from the change in shape of the body (smaller cross section, much better wheel skirts, longer body, more bluff nose) and the other 10% (estimated) comes from improvements from a better construction (correct window shape, smaller seams), a more aerodynamic exhaust pipe, spoke covers, and a lot of secret stuff in the front wheel skirt area that I have never seen in a supermileage car.
should slide through the air nicely.
congrats.
Will the driver be lying on his/her back or stomach?On his/her back. Going head first would be extremely dangerous and very hard to steer the wheels. Not to mention it being extremely uncomfortable and it would take too long to exit the car (10 s limit). Yet I get asked this question by ~50% of the people who see the car for the first time. Only the single person bobsleds do I think you go head first..... luge boarding has the person laying on their back. The feet fit better in the small area of the nose than a racing helmet.
Do not tell us how much that belt cost.It's not that bad... about $50 shipped. We have two just in case we snap the carbon strands or shred it on our clutches' bell housing. Even though the belt is good for many times more power than we can put out, we feel it's the best belt because it springs back to shape when you bend it.... aka the energy is not just being absorbed by the rubber and being lost (nylon belts don't spring back).
"Which way is it supposed to turn?"CCW, looking at the front side of the sprocket..... but I think we are mounting it backwards for the new car to get it closer to the tire.
you just got ta love those programmable machining centers with their auto selection tooling carriagesIt took 8 days to machine it, on a mill with only 12" of travel in the Y direction.... so it had to be done in two halves and lined up perfectly (there is no room for error with the teeth alignment when working with large sprockets). In total, there were 34 different g-code programs run. To make things more interesting, the sprocket shifted twice while it was being machined.... so I had to sort out how far it moved and then I had to re-draw the sprocket to accommodate the change.... hence one spoke is 1.78 degrees out of alignment.
Is the intent for the spokes to be in tension or in compression when the engine drives the belt?LOL. It's a valid question.... we tried symmetrical spokes and they didn't seem to perform as well as this design. We tried 3,5 and 6 spoke designs as well. The best performer was a thin solid disk... but I don't feel like it would be stiff enough in the sideways direction.... which is a very real concern when dealing with our set up(we proved this by mounting a GoPro camera to the roll bar of the car and pointing it towards the drive belt while the car was driving to see what was really going on... the results were scary ;D). http://www.youtube.com/watch?v=xerLzUMVG7o (http://www.youtube.com/watch?v=xerLzUMVG7o)
Oh, wait. I forgot. The answer to that is "yes". Poorly worded question.
it took 8 days to machine it, on a mill with only 12" of travel in the Y direction.... so it had to be done in two halves and lined up perfectly (there is no room for error with the teeth alignment when working with large sprockets). In total, there were 34 different g-code programs run. To make things more interesting, the sprocket shifted twice while it was being machined.... so I had to sort out how far it moved and then I had to re-draw the sprocket to accommodate the change.... hence one spoke is 1.78 degrees out of alignment.I know full well about machines not being large enough LOL
If a large enough CNC mill was used, the sprocket could be cut out in one day easily, with just one program (depending on how many lines of code it can accept...).
"What about the heat transference from the exhaust tube to the timing belt?" - The engine sits under an air vent, so there should be plenty of cooling. We will probably swiss cheese the living daylights out of the sprocket, so that should increase the cooling surface area.I was just wondering because a friend of mine rotary cam valved an Olds quad 4 gear drove a super charger for the intake and hung a turbo off the exhaust.
m guessing there's a slot at the "left-hand" end of the exhaust tube, over the manifold. As it turns its opening aligns with the cyl head allowing the exhaust gas out.There is a slot on the intake side and a slot on the exhaust side. It is a 2:1 ratio. The larger diameter pipe on the right is just an extension of the exhaust side, and is there so the exhaust pipe does not rotate. There are 4 bearings in the design... two of them are obvious.
The previous hints would be located around page 7-8....
You will do away with the cam but you have to deal with sealing around the tubes against 100 atmospheres combustion pressure.Yep.... a 16:1 compression ratio is a blast to deal with. It's safe to say that the spark timing will be fairly close to TDC, else too much pressure could develop. Our current prediction is sitting around 7 MPa for peak pressure. The design allows for the combustion chamber to leak excess pressure if it gets too high.
Heat is a transient problem, like you say, at least.Heat and seal wear are the two main issues that make this hard to put into a production car (but both are certainly manageable). That's why it's so cool that we found an application (supermileage car) that we can effectively not care about these issues. Design life of the engine is less than 20 hours... more likely just one hour.
Here's to Taylor and his team bringing a very cool idea to life!I can't wait. There is going to be a lot of attention drawn to this once it runs.
Those look like 1/4" socket-head capscrews.They are 5/16, with no threads where the aluminum will be sliding. The max loads were assuming a worst case scenario for the pressure on the valve (port + seal). We will probably try out a series of less stiff springs until it stops sealing, which of course will greatly reduce our frictional losses and make the engine run smoother (if a 16:1 compression ratio with an ultra-light flywheel at low rpms could ever run smooth.....)
Rather than pushing the conrad bearing against the bare shaft tube (which would crush it) you will have a reinforcing ring around it (not made yet).Correct. The valve itself has a 1/8" wall thickness, so it shouldn't crush. The exhaust pipe on the other hand is designed to be very light weight, so it could be crushed with just your hand.
Hardly ever post on this thread, but ALWAYS look!Thanks! Major changes to the car should come more rapidly over the next few weeks as we get the rear sub frame, drive wheel and engine in the car. Then we get to test drive it to see if all of our new ideas were good ones :)
To cool and great work!
Maybe (just maybe) the wheel fairings can be covered with a transparent material, which would allow much more side visibility.They were clear in the last car, and they worked quite well. The tricky part will be the new spoke covers for this year, which will probably be clear red due to a lack of choices where we bought the heat shrink material. That will have to be evaluated later.
A point of curiosity? How long would the engine last merely sitting and running? not stop /start stuff but running. Say as a stress test of the heating/cooling of the engine and components.A stock L-head, air cooled with the vent not over the fins: ~30 minutes of dyno testing. At which point the oil starts to steam out of the crank case and the head temperature reaches 425F +.... not good for an aluminum engine.
WOW! and here I am enjoying the hypermilage tricks I use to get above the 36/mpg in my 2010 Chevy :).Today, I tried my best going to work and improved my mileage by 20% over the previous day with 20.7 mpg in my Jeep.
Those foreigners at Laval might steal your technology!!
More seriously, I'm a little worried about your schedule.I say we are on schedule for driving the car around in about a week. Today, we finished the tabs for the front wheel flaps and they turned out really good, so the body will be smooth up front. Everything else is pretty much built.... just the final wiring and attaching the little things to the car. The front wheel covers should go in this Friday, along with some final body filling and sanding. The side windows were cut out last week and the front window is still being worked on, but it's looking like next Thursday for that. I think this year, we have decided to not use marine epoxy for the windows, just packaging tape on the inside.
hard to believe, this is the same motor as my 1973 snow blower !Yeah, it's a really old engine design. They haven't really changed the shape of the L-head much, but over the years, Briggs has updated the internals, like the piston and the crank bearings.
Did you also mention "Teflon" a few pages back, or am I thinking of something else? I'd examine that too.
Agree with the choice of brass. If fact, here it is in the BOM on a drawing right beside me!
Any other scoring or damage worth mentioning so far?Surprisingly no. The wear rate was very low too, considering the amount we have run it.
Correct me if I am wrong but in your application you are using the lobes of the cams to increase the sealing capability.Kind of. The cams are there mainly to counteract the changing cylinder pressure, so the valve doesn't just fly off the top of the head. Hence the actual force of the pipe on the seal is relatively low.
A friend of mine about 15 years ago was working on a rotary valve for a 4 cylinder engineInteresting. I have only seen 3 other 4-stroke engines with the valve shaped the same way as ours. And all of them utilized a split head design with beefy bearings holding it firmly in place. We obviously decided to skip the bearings and the top half of the head. This greatly simplified the sealing situation. But it also required a lot more calculations to make sure the valve was going to stay in place..... trying to accurately calculate the pressure inside the cylinder with no real world data was a lot of fun.........but a challenge I was happy to take up. Spark timing and the volumetric efficiency play huge roles in the peak cylinder pressure.
at first he tried a pure cylindrical tube valve he eventually wound up with a complex system but it worked
...oil filled brass right now - SAE841 grade...
...A serious thermoforming set up right here ;D
I've always wanted to build one of those. The world needs more curvy shaped windows.Now the world has a few more:
Congratulations! Must be nice to see all that work paying off.The competition is June 6th and 7th at Eaton's Proving Grounds in Marshal, MI.
So when are the race (s)?
it looks wicked Taylor , congratulations to you and your team.Thanks from the both of you! I hope it works out the way we planned. After last night's work session and testing, I think the aerodynamics and rolling resistance are as good as we have been planning for. The tubeless radial tires are going to work.... we were very concerned that our large drive sprocket was going to be too large in diameter, but it looks like the belt clears the ground by ~3/16" ;D Next is to make one of the 3 engines we have work better than a stock engine. Else, a stock engine will have to be fitted. We also need some more starter batteries, as we have worn out / killed off too many of the ones we own.
Did you due a rolling distance ? how far after the engine is turned off does it roll even on standard roads?Well, on the test track, you drop 4 feet in elevation, starting at ~21 mph down to 10 mph, the car rolls for about 1.2 miles, but that could be farther with the new tires and aerodynamics.
Sounds wicked too!
I like seeing the blue flame from the exhaust. ;D
you call it "the sea cow" ?Yes, it's nickname is the sea cow, since it looks like a manatee when it's upside-down.
Great job and congratsWe used last year's 12.3:1 CR rocker push rod engine with the stock 148 cc block. The rotary valve and our mini OHC engine did not run well enough to be put into the car.
did you use your rotary valve engine or the conventional head design?
would be interesting in reading about an after race tear down evaluation
Thanks; Will you be involved again next year or is it time for you to pass the torch onNo, I graduated a few weeks ago, so no more supermileage for me. There are lots of great students who will have the chance to do even better.
... We are still trying to upload all of the photos, of which me with the trophy is not up there yet...
So you never mentioned your major through all this - M.E. I assume? ...or EE? IE? CE?I am a mechanical engineer. About half of the team is also M.E. We also had a few E.E.'s and computer engineers. The club used to be almost entirely MET's, but that stopped around when I started 4 years ago. I think the MET's valued more the high horsepower tuned engine designs than the now tiny, fuel efficient engines we put in the car today (the cars used to weigh 200-400 lbs). It was a very strange shift, because the adviser is a MET faculty member. In my opinion, the MET's are just as capable as the ME's when it comes to making a car.
Then you may be facing the work-place soon. Totally different set of challenges. Good luck to you there, too.I landed a full time job 3 months ago at the place I wanted to work. My good grades, the supermileage car and several good references inside the company made things easier (but by no means a walk in the park). A 3.9 or 4.0 GPA does not get you into the company I work for.... they were looking for a particular type of person/engineer.
I landed a full time job 3 months ago at the place I wanted to work.
Is it once again for school competition?Nope. Personally funded and no rules to go by ;D
Welcome back, TaylorThanks! It's been a while since I have had the luxury to play with a windmill. A new generator will have to be procured for double duty as a dyno and a windmill again. I might go the extra large brushless outrunner motor route since I own a lot of large scale RC equipment. I'm thinking of a motor doing double duty as a starter motor and generator, all while being controlled by a radio controller. That way I can hook up a servo to the throttle on the carb and vary the load without standing too close to the engine... as well as being really cool.
i see one port in the head
i see one diagonal port in the rotating valve.
does this one angled port do both intake and exhaust?
looking forward to seeing the intake /exhaust manifold perhaps that will enplane
oh. ok. so the gasses enter/exit through the ends of that rotating shaft.That would be how it is done works fine for a single cyl engine on an engine with more cylinders it would require a separate
Any thoughts about a lubrication system?For right now, we just drip a bit of 5W-30 on the valve to get it wet. If it needs more, then we might bevel the leading edge in the aluminum head a bit to hold more oil. We could also essentially have an oily brush that gets dragged on top of the valve (slightly dangerous with the possible exhaust flames being present....). My senior design project just had a graphite block with some tiny cross drilled holes and an oil reservoir. That actually worked really well. If all of that fails, then some tiny grooves in the surface of the half pipe or even pressurized oil could be done. I don't think it will a huge problem given our experience with the first design. Then again, we used 6061 for this head instead of the QC-10 aluminum, so it's a lot softer.
...we couldn't seem to get the spark plug to fire, even though it would shock you if you touched it.
Any thoughts about a lubrication system? I know that it's meant to run sporadically, but if wear starts to show up (presumably on the half-pipe channel first) do you have a plan to lubricate?After the initial runs today, just having the valve wet was enough for it to run for the 80 seconds without any signs of things getting dry. I'm thinking a slightly heavier oil than 5W-30 will improve sealing. Maybe some 80W-90 gear oil would be more appropriate as we get the engine up to temperature (what ever that turns out to be). After 80 seconds, the exhaust and center of the valve was only 105-110F according to my IR temp gun. Granted, it was probably 40-50 F when it started, so.....
The pipe is more complicated than I thought. How hard is it to make?
Is it machined as one piece? Can the machining of each path be completed from the port side, or do you have to do some tricky things at the bottom of the hole bored into the bar? Now that I see the way the passages are separated, I wonder if maybe an insert that pushes in from one end would be easier to make.
You have too many files open Taylor.That's nothing. Running CFD, I pushed my laptop to 59 Gb of RAM used (16 Gb actual ram). A solid state disk drive helps in that endeavor. At work, at times I have had 40+ applications open at once (I do a lot of data mining across different programs) and it only has 4 Gb of ram and the motherboard tends to only allow me to use 2.2 Gb of it... the rest of it gets swapped to an encrypted disk drive, which is really slow.
If I did that on my computer, Inventor would crash!
:)
Are you still working on the valve port geometry?The new inserts should be the final answer. It's now down to adjusting the advance of the valves relative to the crankshaft and ECU tuning.
"I don't remember everything you came up with to make a solid seal "- There's 4 parts to sealing this. Two rotary shaft seals. The half-pipe floating seal is pushed up during the combustion event for increased contact pressure. And a spring loaded top seal so the vacuum from the intake manifold isn't lost when the intake port on a particular valve is up above the half-pipe shape. In addition, we also made some silicone pieces to cover the whole head to help reduce the smoke that escapes from all the joints.
Do you have any estimate how much power this sucks from the engine, compared to a cam/valve system you took off?- Not on this engine, but the one we did in college on a Briggs and Stratton, yes. There has been other people who have estimated that the rotary valve system takes less to drive than a camshaft, but I think that's probably if everything is working well. It's not too bad, so I would say the savings or penalty isn't large.
Have you worked on any methods to advance/retard valve timing?- Yes, there is a taper fit #40 chain sprocket coming out of the bevel gear box that is adjustable within ~2 minutes. This is an important part of the design since you can really tell the difference depending on where you have it set or if it slips.
How much does brass like being a cylinder head?- Haven't had any issues yet with the brass. It holds up well to the rotating surfaces. I've had the engine fairly hot with no coolant flow and also I've driven it ~ 8 miles straight without stopping. So far it has about 105 miles on it over the last 5 years. Hopefully that number goes up here now that we have it back together and it's stopped snowing.