Treadmill Dyno

[Bruce S]

I can now see why you kept the design under wraps !!

[taylorp035]

Last Friday, we spent a bunch of time trying to thermo-form our front window.  But all we have in terms of tools to heat the plastic (~24" x 36") is a hair dryer style heat gun (1550 W).  So we made ourselves our own oven with cardboard and high temp duct tape.  As for insulation, we used a combination of a large amount of cardboard and pink foam, but we found out that the foam melts at 240 F, well below the ~350F we needed to reach.  After 4 hours, we finally made enough improvements to our cardboard oven enough to hit 332 F with the heat gun and a 1800 W hair dryer.  Unfortunately, you need to keep the plastic above 320 F for it to be flexible and below 370F to prevent bubbles.  By the time we tore apart our oven and applied the plastic to the mould, it had cooled off too much.  We got the main curve in the window, but the 2nd axis curve (the side profile curve) did not happen.  We have a 2nd piece of plastic if we want to try again, but we may not have enough time to do so.

We also broke our steering in the front, so that needs to be fixed.  But on the plus side, we found a solution to our battery management issues to pass the rules.  We also ordered a new set of points for the engine, since we have vaporized the old ones in ~50-100 h of running it.  This was affecting our efficiency majorly.

[JW]

If you used some small gauge sheet metal instead of cardboard for the oven, then line it with fiberglass house insulation with another layer of sheet metal(with a door), you could get to your work piece out quicker using that door (without tearing apart a cardboard box) ,then the adjacent area you could use some 5/8 thick foam board and make a sauna room adjacent to the oven,(with a door also) steam it up pretty good and fashion your work piece on the mold in there.

Dry air around where your working is going to cool too quickly, and without some form of humitity control for the work area, when you fashon it to the mold it will be too cool. the mold should already be as hot as the sauna room. then when youve got it clamped down to the mold take it out of there to set.

JW

[taylorp035]

We have aluminum sheet metal, but no fiberglass insulation.  Our only insulation sources were layers of cardboard with some air pockets and the pink foam.  If we try it again, we will probably use some wood as the side walls and the support structure.   

Our cardboard over was hinged on the top so you could just open it up, but we had accidentally taped it shut while adding the various pieces of insulation.

Also, we had to make sure the edges of the plastic were not hot so we could grab it since we only had 5 gloves (and there were welding gloves, so it wasn't ideal).

You can check out the photos of it in here under the Build Photos (3):

http://behrend.orgsync.com/org/societyofautomotiveengineers22440/Pictures

[JW]

Well in that case, I would submerge it into a pool big enough for it, and use heat transfer fluid with the temp you specify.

I guess your right its not really a good conductor of heat (the work piece) so you should have what you need.

Hope it goes well, you've solved simular problems in your posts here related to the project.


JW

[taylorp035]

A big deep fryer would do the trick       Now where to find a deep fryer that we can use.....

[JW]

If you had a metal pan that would hold it(insulated outside), you could get 500°f  heat transfer fluild http://www.radcoind.com/Profile.html

You would need a pump like this  http://www.marchpump.com/809-br-brushtype  I have one of these and have heated the transfer fluid to about 345°f sustained.

The pump runs on 12 volt, and I would use a coil heat exchanger on the output to the tank.

[taylorp035]

YAY!!!!!!!!!   Finals are done for, so tomorrow will be ~17 hours of non-stop supermileage time   

Earlier this week, we finished sanding the body (a good 15 man hours) which was extended another 2 hours since we got oil on the top of the car (shown below).  One of the bolts that was on our side plate cover (about a 1/2" diameter) wiggled loose and oil sprayed out of the engine while it was running....  the oil covered my laptop, a desktop computer, my brother's hand and the top of the car that was on the ground near by (which I had just finished sanding 2 minutes earlier).  Since you don't really want to paint over top of an oily surface, I tried to wash it off, but it had stained the lid real bad.  So another 2 hours of sanding was done with a DA sander.  But at least the top is extra light weight now....



We then weighed the car with the windows, top, frame, roll hoop and the body.... coming in at an impressive 31.2 lbs.  That makes it about ~6-7 lbs / m^2 of surface area.



Next up was installing the engine with the reinforced engine mount (hoping to skip the turn buckle this year).  We also finished version 2.0 of the rear wheel mounts, with our radical carbon fiber lead springs.  They are about as stiff as a plastic fork, but they should hold the axle just fine and allow for an adjustment of ~1/2" forwards and back.  The rest will be tied down with an array of titanium and some turnbuckles.  The downside to this is that there is almost no room to get your arms in the back to assemble it... definitely a "no wrist watch" zone     Before sanding the car, it is kind of like sticking your arm into the sharp needles of a pine tree....



As for space around the engine, I'll let the pictures do the talking.... note the missing carburetor (it doesn't fit right now...) and how close the flywheel is.





There are many more places where the clearance is less than ~1/8", especially around all 3 tires.

[taylorp035]

A fun photo from my CFD work on the car.  This new software that I have could work really well with designing and simulating a wind turbine.... assuming there was enough time to do so.  Autodesk Simulation CFD.

The large version link:
http://i47.tinypic.com/avg56q.png


640x480 version:

[taylorp035]

The current car     Check out the 462 kb high res photo.  1.88 N of drag @ ~15 mph.  I  need to make the wind tunnel a bit bigger so the air doesn't speed up so much around the car (currently the car is 3% of the cross sectional area of the tunnel...  should be around 1%).

High res:http://i48.tinypic.com/15hy9h3.png




Next up is to make the road move below the car   

[taylorp035]

With a bigger wind tunnel and a bit more computing time, the drag on the car went down to 1.32 N @ 15mph or a drag coefficient of ~0.14.  I think this value would be lower if I could model the road below the car.  Some photos:

[SparWeb]

Before sanding the car, it is kind of like sticking your arm into the sharp needles of a pine tree....

* cringe *

Please be careful and wear breathing masks, gloves and long sleeves!
Even go so far as make yourself the "bad guy", and police the others on the team, for their safety.

In an industrial setting, the protective gear is a given, but in the college/university shop I do worry.

I should have taken a picture, but I was a bit too busy driving to the hospital, the day I learned THE HARD WAY what not to do with CF.

[taylorp035]

We are always really careful with the dust.  We also use two large industrial air vents to pulls any particles out of the air.  Safety glasses are also heavily enforced.... especially when using a dremmel tool for cleaning the sharp stuff.  I've had my fair share of things hit me in the face to know that they are a good idea.

One of the tricky things is when you go glue more C.F. into the body using rubber gloves.  When you spread the glue on, you end up tearing holes in your gloves   


Today we plan on test driving the car for the first time 

[taylorp035]

I think we did a good job on the paint, considering we had no professional help and all for about $60.



Initial testing is coming in at ~1000 mpg with the bad tires and several other things that aren't perfect.  2,000 mpg will be a stretch but certainly doable on the test track.  Total weight = 91.4 lbs.

[electrondady1]

it looks great!
what a wonderful accomplishment for you and your class mates tayor

[taylorp035]

Thanks electrondady1!  The competition is only 11 days away     Hopefully we can beat some of the Canadians this year (much credit to their teams for doing so well).

[zap]

Looks pretty darn slippery.  Nice job to all and best of luck in the competition.

[SparWeb]

Yes, I may (grudgingly) be cheering on a non-canadian team...  We'll see who's still standing after the first day 

Checked the SAE website and wow:  32 teams.   Hurry up to be first in line at the refreshments stand or you'll miss out!

All the best good luck to you.

[Bruce S]

Very nice!!

[DamonHD]

Yes, very good indeed!  1000mpg?  Just got to convert a few SUV drivers and Peak Oil will vanish into the future again!  B^>

Rgds

Damon

[taylorp035]

Thanks everyone!  I'm so glad that so many people are following our project.  I can't wait to get some official numbers.

Here is another photo for you guys, this time from the inside.  Note the awesome steering tiller/handle.  I'm really proud of how lightweight and compact the steering and brakes are.  In this photo, the wheel skirts are muddy from us test driving it (from the tons of road salt dumped on our parking lots every winter...).  When clean, you can can see right through the wheels for better visibility.  Everything is very carefully planned out.  The seat cushion and seat belt carefully hides the ~3" tall cross member between the kingpins and the tie-rod (many people are confused that we don't have a rack and pinion steering box).  But the most amazing thing is that everything fits considering that the whole car was laid out by hand... no cnc work here 

For sizing... those are 20" bicycle tires and the frame rails are ~12 3/4" wide (this car is much more comfortable for narrow people).

[Frank S]

Taylor I apologize if I seem to hi-jack your thread for a second.
 But Steve; low RPMs is not always the best solution to higher mileage.
 If the vehicle you have in question wanting to drop the RPMS to 1200 or thereabouts is a diesel then by all means it is worth a try however even  most diesels torque curve works out higher than 1200.
1200 on a gasoline engine except for some 50 gallon piston monsters is far below where automotive engines develop their sweet spot, which is usually near the middle or as low as the 30% mark where the curve goes dead flat
 an example My wife used to own a 91 ford ranger pickup 5th gear on flat ground @ 70 would not get her any better fuel economy than  4 th gear @ the same speed. usually it was much lower millage as she had to push a lot harder on the pedal to maintain 70MPH.
 Last year while on holiday I rented a VW polo diesel for 2 weeks then the same model car with a gas engine I was traveling in Spain lots of mountain driving. 5000 Kilometers on each car the diesel averaged 30% better fuel millage over the gas. I had to constantly down shift even into lower gears to maintain speed with the gas engine where as with the diesel I might have to drop into direct occasionally on the worst climbs for highway driving.
 Taylor I am trying to visualize 18 to1 comp on an engine like you have and I am wondering just how lean the air fuel ratio could go with the fuel injection system before destructive forces take over.
 I know that the model airplane engines can achieve an absurd A/F

[SparWeb]

Frank, I was confused at first, reading your comments.  Are you picking up on comments made by MadScientist, in December?  I can find that on page 8 of this story.  It's helpful to other readers (not to mention Steve himself) if you click the "quote" button on a particular comment before following up on it.  That preserves the context and saves any other reader from scrolling back pages to find an old comment.

As for the comments you make now, Taylor's car isn't a diesel and 90% of the time its engine is off.  Hard to make comparisons with your Polo.  I don't think this car needs much speed range, either - it drives at the same speed around the track the whole time.  So far as I gather, at least.

[taylorp035]

Let me set some things straight  here....   The operating range for the engine is to run for about 3 seconds going from 1500 to 3000 rpm (basically doubling our speed from 10 to 20 mph or so).  We have tested our engine over the various rpm ranges and have found the efficiency stays fairly flat in that rpm range.  Much higher, say 4000 rpm, efficiency starts to go back down.  Interestingly enough, the speed at which the car drives is even a stronger relationship than the curve of the engine efficiency, so it's in our best interest to drive it at the right speeds.

Our compression ratio is currently about 13:1, which is just fine considering we are using iso-octane fuel.  The only hard part is that this puts more stress on the starter motor, especially with our super light weight flywheel.  If there is no load on the engine, the engine will spin up as fast as you could imagine an engine doing so.

Our engine isn't particularly efficient... based on our somewhat crude testing, we figure ~15-17 %, compared to maybe 25-30% for a normal car engine.  At stock engine that we start with is somewhere around 12-14%, depending on AFR (lawnmower engines run way too rich for supermileage use).

The major trick to getting good mileage is not running the engine the whole time.  If we just idled our way around the track, we might get 200-300 mpg.  If I wanted to keep the car going at a steady 15 mph, we would need about 50 watts or so, plus a boost of 1/2 hp for going up a 1% grade.

We are using a carburetor on our engine this year because it's simple, lightweight and effective...... we have an EFI set up, but have found it unreliable and not as efficient (10% for our testing, but it wasn't running very good).

[Bruce S]

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.
Slick looking paint job too!
Bruce S
 

[Frank S]

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 .
I used to have a little neighbor kid that had a mini bike with a 3 hp Briggs his carb was really messed up from him constantly tapping on it to un-stick the float One day his dad brought it to my machine shop along with a carb off of a Honda 90 and asked me if  I could adapt it to fit and make it work.
 I explained to him that the brigs was a lot larger displacement but lower overall HP and not to expect any miracles but it did run, and also ran just fine it even ran over twice as long on a given tank of gas.
 this was 30 years ago and no power curve or any other testing was done just a very happy 8 year old terrorizing the neighborhood on half the fuel. 

[taylorp035]

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).

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

[Frank S]

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).

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

when you go to the EFI will it be a throttle body system of will you rework the head and opt for direct injection.
 I can see merits for either system But anything that significantly reduces the droplet size for a better fuel air mix allowing the air ratio to be increased should yield good results   
  Does the rules in your "class" allow for positive pressure air induction. I was thinking that the  "car-PAC II" (I think that was its name)  that holds the 12K + record was forced air as well.
 I like your thoughts on the Fred-Flintstones brake simple enough to have  section of the floor with a layer of dense  rubber  that is forced to the ground  not sure about the rules on that though

[taylorp035]

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.


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 

[Frank S]

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.


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 

the Atkinson cycle in such a confined engine block might be tough to achieve any benefits,
  Positive pressure air induction could be done with a retractable or pair of retractable scoops on the side or near the front of the vehicle they would need to close and be perfectly harmonious with the rest of the surface area when the engine was not running other wise it would create drag. you could wind tunnel the machine to determine just how much actual pressure could be obtained before the advent of added resistance out weighed the flow the engine was receiving
  Since your engine is only operated for such short periods of time by the time enough exhaust gas flow would be created to spool up the turbo to raise the intake to a positive you would be shutting off the engine. For this reason I thought of the positive induction the slipstream air would be diverted directly into the engine. your engine has to get intake air from somewhere why not use a couple of magnetic solenoids to actuate an induction scoop . you might not get full positive due to the low speeds of travel but theoretically better than having to suck every CC of air into the engine.

[taylorp035]

That's a very interesting idea that could be done fairly easily, since the electrical circuit is already there for a solenoid.  I have seen similar setup on solar cars for when they need to turn..... their wheel skirts open up to make more room for the front wheels to turn.

[Frank S]

It might warrant a simplified mock up model tunnel tested before any modification to an actual car, a whole lot cheaper to scrap a few pieces of curved panels and duct work connected to the engine on your home grown dynamo than screwing up a car if the tests didn't pan out

[taylorp035]

Yesterday we did some more testing, even though it was dark outside and raining     The pulled off an official 773 mpg but it equals ~1150 mpg due to the hill it was driving up, which isn't too bad considering the lack of traction (smooth bike tires on asphalt), the windy conditions, and the fact the testing place is only about 0.35 miles in one direction.

I did a few calculations based on the real performance on last year's car at the proving grounds, and I figure this car should do at least 1850 mpg and no more than ~2,600 mpg, plus or minus a 100 mpg or so for the uncertainty caused by the different tires.

We did break our rear wheel mount yesterday, but no worries, we fixed it so it won't be going anywhere   The part that came loose is a 3/8" thick titanium rod that's 6" long.... we were tempted on replacing it with an aluminum rod of the same size, but after a few calculations, we decided that it wouldn't hold up to the ~500 lbs of load that is caused by the running engine.

 I also found a bolt that was rubbing on our rear tire spokes.... good thing I caught it, else there could of been a bad breakdown at the track.

The only thing that still worries me at this point is how much power we are using on the starter motor.  Last year's car only used 300 mah, but during 3 miles of testing, this year's car used 1,000 mah, and we need to go 9.6 miles on ~1200 mah (ideally 1000 mah or less).  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).