Author Topic: Treadmill Dyno (Read 192002 times)

taylorp035 · « **Reply #198 on:** January 12, 2012, 04:27:37 PM »

We found out yesterday that the stock compression ratio is 6:1...... = not good. The new head calls for ~13:1, which we hope to make some chips tomorrow.

We also received some new tires

We haven't been able to mount them tubelessly, but we don't give up too easily

If our predictions are right, this set up will be the best that we have ever tested in terms of rolling resistance.

taylorp035 · « **Reply #199 on:** January 31, 2012, 06:28:23 PM »

UPDATE:

After 2 years of figuring this out, we finally managed to mount our thin supermileage tires tubelessly without leaking any air without building custom spoke-less carbon fiber rims. Considering our rolling resistance tests and the gains found by making the tubes thinner, we expect the results to be very, very good with out the tubes. Michelin claimed a 100% - 200% drop in rolling resistance in their best tires by going tubeless.... obviously, there are a lot of factors, including if the tubes are butyl or laytex (finding 20" laytex tubes is very hard) and how thick the tubes are.... there are some discontinued japanese 20" tire tubes that weigh 1/2 the weight of our lightest ones that we currently own, but at $25/each and getting them shipped over here from Japan, it may not be possible or worth it.

We also received our shipment of 6 new supermileage tires... it took significant amounts of effort to obtain these (again, 2 years of trying). Now only if we could get the radial tires..... I think there would be a North American mpg record that would be broken. Our goal this year is to set the SAE USA record, which we believe stands at ~1640 mpg. Shell ecomarathon participants from California have achieved 2800 mpg...

The other big news is that we started construction of the new supermileage car. The car body should be about ~30% as heavy as the 2011 car with less than 70% of the frontal area and a lower drag coefficient (significant amount of time was put into CFD software over the last 8 weeks.) As a bonus, the driver will get more room and the engine bay will be less cramped. Last week, we had 8 people drawing and cutting foam out for a solid 4 hours and we only got half way done (the car has 61 2" thick cross sections....), each of which required a 3 step process and 2 cross sectional drawings to be applied to each with a Sharpie Magnum

. As you can tell, we decided to skip the CNC cut mold, due to several practicality issues and the tricky part of getting a company to donate ~$20k-30k of labor and machine time to make it. Also, it would of dragged the whole process down and been more expensive on our part, due to the extra foam and fiberglass mold supplies. So, as a part of making everything fit together, we made an 8 foot long giant shish-kabob to prevent torsional misalignment and bending.

The new engine head should be assembled later this week and hopefully be run in two more weeks time. We expect it to be much more efficient and have way too much power

taylorp035 · « **Reply #200 on:** February 12, 2012, 04:44:38 PM »

The new body is moving along at breakneck speed. If you guys want a picture of it, you can PM me and I will gladly send it to you.

Else, we did some fun testing of the new components in the old car. The new timing belt worked better than we could of hoped and the ultra light engine mount didn't bend. Unfortunately, the car had less than 1/8" of ground clearance and the rock salt on the ground gave the car some problems. Hence we installed our extra large winter tires for the test to increase the ride height a bit.

The tire was spinning pretty much the whole time the engine was on, so the burnout was about 50 feet long. ~70 lbs of traction and ~40 ft*lbs of torque should break loose any bicycle tire

Our new OHV engine head should be done on Monday...

Our competitors from last year that took 1st place... they claim $48k in sponsorships.... our new car should do the same mileage for 1/10th the cost.

taylorp035 · « **Reply #201 on:** March 09, 2012, 04:32:39 PM »

http://www.youtube.com/watch?v=lp7ca1bBWOM

Better video of the burnout.

Here are the new rocker arms for the overhead valve engine

A picture of the new head...

We are still keeping pictures of the new car under wraps.... maybe in a month, you guys will get to see it

Bruce S · « **Reply #202 on:** March 13, 2012, 02:30:26 PM »

Are you seeing any weight reduction by machining your own head or ?
Cheers
Bruce S

taylorp035 · « **Reply #203 on:** March 17, 2012, 06:28:27 PM »

Quote

Are you seeing any weight reduction by machining your own head or ?

Unfortunately no, the original head was very light (a few ounces). The new one is probably 2 lbs or so.

The whole rocker arm set up is much closer to being finished... it should be done by next week. Last Friday, we threaded a bunch of holes and put the valve guides in.

taylorp035 · « **Reply #204 on:** March 18, 2012, 10:29:04 PM »

http://youtu.be/ZaQUkauajjs

A daytime burnout on dry pavement. Today's problem was a loose wire in the starter motor circuit.... but on the plus side, it was 75 degrees and 7 people got to drive the car!

taylorp035 · « **Reply #205 on:** March 20, 2012, 02:50:55 PM »

SparWeb · « **Reply #206 on:** March 20, 2012, 03:26:51 PM »

Looks nice and simple. Guessing that you don't need cooling fins etc because the engine runs only for brief periods.

Do I see chatter on the rocker arm ends?

Also, Heli-coil is your friend. Use it anywhere you're threading a steel fastener into the aluminum.

taylorp035 · « **Reply #207 on:** March 20, 2012, 03:45:40 PM »

Quote

Do I see chatter on the rocker arm ends?

My little CNC machine isn't very rigid, but the other one came out good. It could be from the programming too in the CAM softare.

Quote

Guessing that you don't need cooling fins etc because the engine runs only for brief periods.

Yep... we are actually thinking about insulated the whole engine to keep it warm. When we run the car, the exhaust won't even burn your hand after 4-5 seconds. There was a team last year with a plastic exhaust pipe, but the inspectors didn't like it.

Quote

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.

Possible tomorrow night, I may get you guys a picture with the rocker's and the spark plug installed. Later in the day, I took it to my last class and set on my desk to look at during class.... learning about gears and their safety factors can get boring at 4 in the afternoon on a sunny day

taylorp035 · « **Reply #208 on:** March 21, 2012, 07:59:09 PM »

It's been a long time coming (~3 years...). The last part that it needs is the extensions on the end of the push rods (the threaded guys in the back).

JW · « **Reply #209 on:** March 21, 2012, 08:53:50 PM »

interesting thats a L-Head engine block, is the head gasket round or does it have the clearance for the old engines valves.. Also if you have managed this, have you added the extra cyl head bolt that was not originally there. I see the valve guides are not angled like a hemispherical arrangement. is this so you dont need a relief on the piston top, and what is the compression ratio with the new cyl head.

taylorp035 · « **Reply #210 on:** March 22, 2012, 11:36:36 AM »

JW,

The head gasket is not round, but rather the shape of the entire top surface, which has to seal the cylinder and the valves. As for the extra head bolt where the intake area once was, no, we did not add another bolt. The rocker parts would kind be in the way and there is not very much material to sink an extra bolt into. Also, you could loose compression through there. The valves are straight and are positioned so the engine is a non-interference engine with no head gasket (according to the drawing), but the valves are actually a bit lower, so hopefully the head gasket is thick enough to make up for this. The compression ratio will be 12.3:1 with a 0.060" head gasket, and 16:1 with no gasket. More than likely, the connecting rod would break much past 13:1... The stock engine was supposedly 6:1, which is very, very low and make a poor use of isooctane fuel (I think you can go up past 18:1 with it).

The valves, tappets, springs, and valve seats are from the original engine. Everything in the block is the same. The hard part was making sure everything was going to line up and that the head bolts were going to fit. Simplicity was a high priority. The really good teams that spend millions of dollars in Europe/Japan have hemispherical engines that are usually ~16:1 C.R. and dual overhead valves and two spark plugs on a 30 cc displacement. Ours in 148 cc's.

JW · « **Reply #211 on:** March 22, 2012, 06:21:13 PM »

I have been working on a "four cycle steam engine" for years. The engine uses a direct injection valve that uses a briggs valve spring.

Im not sure if your allowed to use direct fuel injection, but I would be willing to donate a license for your team. US 6,928,992 US 7,552,715

http://www.flashsteam.com/L912_Injector.htm

-edit- I would recommend the SO8 not the L912, for direct fuel injection, the SO8 is miniturized version of the L912. I would also be interested in (also donating) development technical support, from machining (your machine shop) to electronic control. This is a direct electromagnetic lift valve not peizo. So you would rely on lift setting for throttling, not pulse width control. but the servo does use pwm -edit-

When im talking with other steam folks, they dont seem to make the connection of compression ratio to volumetric efficiency. For the steam applications 9.5 to 1 is considered high compression when compressing live steam, before injection duration.

I know this is apples and oranges to what your doing with the super milage.

taylorp035 · « **Reply #212 on:** March 23, 2012, 12:23:03 AM »

We are allowed to us direct injection, but basically, the engine needs to be a 4 cycle combustion engine.... so I guess no steam. Some people talk about 6 cycle engines too, but I guess that would go against the rules of "4".

Here are the relatively simple rules if you want to see them:
http://students.sae.org/competitions/supermileage/rules/

Quote

When im talking with other steam folks, they dont seem to make the connection of compression ratio to volumetric efficiency.

Is it because there is a larger change in temperature after the power stroke, so the cylinder sleeve is cooler, thus more air can come in the next cycle? I can see that the higher compression ratio would raise the cycle efficiency....

I sure do seem to find a lot of interesting people on this forum

You never know who you will run into with these creative types of people....

SparWeb · « **Reply #213 on:** March 23, 2012, 10:48:19 PM »

Hi Taylor,
Another thought: Are your pushrods sliding through bare aluminum holes? If so, a brass sleeve would reduce the friction, and allow tighter tolerances (sliding clearance) so there would be less noise vibration etc. Getting the right press-fit to keep the brass sleeve in place is a bit of a chore on a "one-off". Enough suggestions from me that make more work for you!

taylorp035 · « **Reply #214 on:** March 24, 2012, 06:12:35 PM »

Sparweb,

We now have brass sleeves in there. The some of the stock engines had no sleeves from the factory, just aluminum valve guides.

SparWeb · « **Reply #215 on:** March 25, 2012, 08:21:54 PM »

Ah just one step behind you!

taylorp035 · « **Reply #216 on:** March 31, 2012, 07:31:11 PM »

The day you guys have been waiting for, the new engine now runs and I have pictures of the new car

EDIT: Some more photos of the SAE supermileage car....

electrondady1 · « **Reply #217 on:** April 01, 2012, 10:26:00 AM »

it looks fast
after you win the mileage contest , maybe jack it up a bit, and take it to Utah?
it would look good with salt on it.

taylorp035 · « **Reply #218 on:** April 01, 2012, 12:49:54 PM »

With the stock engine, the numbers suggest that you could hit about 100 mph on 3 hp

But the tires are rated only for about 40 mph.... Previous supermileage cars have been known to go past 50 mph

From personal experience, much past 35 mph is really scary on 3 wheels and your limited visibility becomes a factor. Surprisingly, the car is quite stable, so it will usually understeer in a corner instead of rolling over.

As for salt, we loaded our old car with salt after driving it around in the slush around the school.... took all week to clean out of the engine bay and driver's compartment.

ghurd · « **Reply #219 on:** April 01, 2012, 07:54:47 PM »

Quote from: taylorp035 on April 01, 2012, 12:49:54 PM

As for salt...

Oh boy... Kids these days.
The salt flats? In Utah?

If you were NOT just messing with E-Daddy, I may have to drive up there and smack you with a perfectly flat salt block!

G-

taylorp035 · « **Reply #220 on:** April 01, 2012, 09:20:17 PM »

No, I wasn't.... note the original burnout in the dark... the road had an inch or two of slush with salt mixed in it. The driver had salt all over him when he was done.

electrondady1 · « **Reply #221 on:** April 01, 2012, 10:10:11 PM »

this is the place.

they bring things there to go fast

look familiar?

electrondady1 · « **Reply #222 on:** April 01, 2012, 10:15:38 PM »

taylor i like your machines shape
it got me thinking, there is probably a scta category for briggs powered streamliners

taylorp035 · « **Reply #223 on:** April 02, 2012, 09:34:29 PM »

A rear wheel steering setup can reduce your total frontal area by lowering the area needed for the front wheels. I would also consider trying out so of the Solar Challenge tires, since they are wider and would have super low rolling resistance and since they are designed for higher speeds. I bet you could get the drag coefficient down to ~0.08 or so if you tried. I don't know what the Cd is for my new car or old car, but many other teams come in at 0.12 - 0.15 for the decent teams and 0.075 - 0.1 for the really good teams. The frontal area for the best cars is less than 0.3 m^2 (extremely small). My old car was 0.444 m^2 and the one before that was 0.75 m^2.

Of course, driver space is critical when designing these things.... as you will find that many of the top supermileage cars have less than 14" of width for the driver, if not 13" or even 12" where they sit between the front wheels. A small driver though can fix many of these problems.

Here is our team site with all of our photos that we are now letting the public view.

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

taylorp035 · « **Reply #224 on:** April 08, 2012, 09:29:52 PM »

We put our new engine on the dyno last friday and even though it only was running at about a 6:1 compression ratio right now (head gasket is blown), we recorded several run north of 15.5% efficient! Previous runs with the equivalent set up with the L-head were about 13-14% efficient. Once we get our new spark plug and electronic ignition set up and a new head gasket, I think we can boost the efficiency a few more percent.... hopefully getting to 20+%. If we could get much past that, I would say we could make a serious run at the North American mpg record

The exhaust note is really cool, kind of like a hit and miss engine and the popping sounds they make. This week, we will get a new head gasket, hook up the AFR gauge, add the ceramic bearing faceplate, and add the high performance spark plug.

We also made sure our new car is going to fit in the van we plan on taking to competition.... at 118" long, we knew it was going to be a tight fit to get it into a mini van...... to make it fit, we had to move the driver and co-pilots seat up a few notches

The arm rests may end up being removed too on the front seats.

We also had all of the members try and fit inside of the new car. Turns out that the new car is surprisingly spacious when compared to the last car, as my 6' 1" frame fit side with out cutting my feet off... Visibility seems good enough to drive @ 15 mph on a 2-3 lane track with a car that is 24" wide $:-\$

You can see how little space we have.... the carburetor doesn't even fit pointing towards the tire, so it's going to go towards the firewall.

taylorp035 · « **Reply #225 on:** April 17, 2012, 12:57:15 PM »

Things have moving along quickly in the last few days. The front windows have been cut out and the front wheels mounted. We were pleasantly surprised by the amount of reward visibility that we have. The front wheels fit well too, especially considering that we have less than 1/4" of clearance in about 10 spots around the the tires and that everything is hand made

We also figured out that you should open the throttle all the way open while doing compression tests.... that way the air can get in the engine

Definitely felt stupid after figuring that one out. Now we have 225+ psi of compression!

Next up is thermoforming the front windshield. Unfortunately, the big machine that our school has to do such things woln't work for our application. But we do have a 1800 watt heat gun and 3450 W of light bulbs, so maybe we can make something work. Looks like we need to get it to around 310-350 F and keep it below 370F.

SparWeb · « **Reply #226 on:** April 17, 2012, 02:14:59 PM »

Taylor,
20,000 views!

Quote

Now we have 225+ psi of compression!

Do I read right, comp ratio = 16:1 (or 15:1 if that already includes atmospheric pressure)
Either way, Nice Job.

taylorp035 · « **Reply #227 on:** April 17, 2012, 11:19:13 PM »

20,000 Views

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...

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...

SparWeb · « **Reply #228 on:** April 17, 2012, 11:59:58 PM »

Quote from: taylorp035 on April 17, 2012, 11:19:13 PM

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...

Here we go with the graphs again!

Bruce S · « **Reply #229 on:** April 18, 2012, 09:12:47 AM »

Quote from: taylorp035 on April 17, 2012, 11:19:13 PM

20,000 Views

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...

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.
I will go out on a limb here and say I 'm sure you've already lapped the head and body top to be ubber-smooth?
Nice vehicle!! you're ahead of Chrysler :-) they're now using CF the lighten their Vipers!

taylorp035 · « **Reply #230 on:** April 19, 2012, 01:45:04 PM »

Bruce,

Our head gasket material is has metal in it. With the 0.040", the gasket makes up about 25% of the total compressed volume.... the chamber is only 9 cc.

I was wrong about the head gasket dimensions from last time... we are currently running 0.040", which makes it a 12.3:1 ratio. I was thinking of the numbers for next year's engine

We did lap the valves and the head / block were both face milled at one point.

We were hoping to make the whole body less than 15 lbs, but it came out to 22 lbs due to several mistakes caused by our inexperience..... it would be nice to have access to a professional shop and use their equipment like some of the other teams do. With the frame, engine mount, wheel mounts, and windows, we will be at about 35 lbs, which compares to about 52 lbs in the old car or ~100 lbs from 2 years ago.

Visibility is better than ever! You can also see how nice the shape is

I bet this new car has half the air drag of last year's. It's also a bit more cozy in terms of space that is left over for components (engine, fire extinguisher, steering, electronics).

News:

Author Topic: Treadmill Dyno (Read 192002 times)