Author Topic: Treadmill Dyno  (Read 164107 times)

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taylorp035

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Re: Treadmill Dyno
« Reply #99 on: April 17, 2011, 12:13:15 PM »
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20x1.75..standard size. I kind of expected you to be using 20x1.5 for some reason.

Wider tires have less rolling resistance.  Air drag is not a concern because we have wheel fairings.



These tires are amazing.  Radial construction (only ones you get get), no tread, and good for 102 psi.



REdiculous

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Re: Treadmill Dyno
« Reply #100 on: April 17, 2011, 02:16:39 PM »
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.

I didn't feel like there was a big difference between 1.75 and 1.5 but the 1 3/8 tires seem to roll forever in comparison. My 1 3/8 tires are about as wide as 2 pencils side by side - comparable to 10-speed tires. The 1.5 tire is about twice as wide, or about 4 pencils side by side.

102psi, wow! That's double what my tires can take and they're rock hard at that point. 8)
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Madscientist267

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Re: Treadmill Dyno
« Reply #101 on: April 17, 2011, 03:42:39 PM »
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pretty sure the opposite is true

Tending to agree here, at least in the logic department. No real world experience to back it up tho.

Rolling friction goes up with the amount of rubber in contact with the road. That's one reason the tire pressure is so high. To keep them from developing the 'flat' spot which would put 'out-of-ratio' rubber scrubbing the road as the tire rolls.

I'd think you'd want to get as close to a laser-cut razor edge as you could possibly get if you want to keep the friction as low as possible.

Sure, at some point it becomes impractical to go too 'sharp'.

Maybe the weight load on the tire comes into play, and PSI (in terms of rubber to road) gets off balance.

... trying to think of a reason to go wider ...  ???

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taylorp035

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Re: Treadmill Dyno
« Reply #102 on: April 17, 2011, 05:02:53 PM »
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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.

Several sources, including Schwable and my supermileage book (the team that got 15,000 mpg equivalent).  At the same pressure, narrow tires are worse because they squish more, which is they absorb more energy.  This is also why people say that larger diameter tires provide less resistance, but my book says this is only true because the ground is too soft (polished concrete is fairly hard).  But narrow tires can be pumped up more.  If you have too high of a pressure, the tire will actually get too bouncy, which can cause a significant amount of rolling friction.

http://www.schwalbetires.com/tech_info/rolling_resistance

Most importantly though, how the tire is constructed changes the resistance.  The tire in my picture is the only "radial" bicycle tire made that we know of.  All other tires for bikes are "cross ply".

We have run narrow tires before at 140 psi, but that's because the wheels stuck outside of the car body.



Here are the paper thin tires:



The tubing on the rear end is 1" square and the sprocket is #35 chain @ 134 teeth  for reference.  The tire is a 1.75" wide tire.  Side wall thickness is about equivalent to about 3 sheets of cheap notebook paper.  The rubber part is less than 1/16" thick.
« Last Edit: April 17, 2011, 06:04:47 PM by taylorp035 »

REdiculous

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Re: Treadmill Dyno
« Reply #103 on: April 17, 2011, 08:23:25 PM »
I kinda get the point they're making but I'm not really sold. It seems like they're saying, "at the same pressure that just so happens to favor a wider tire"...

Look at the pics they show on the right at the bottom. I've never seen a tire that flat, except for when it was actually flat and unridable. ???

edit..incidentally, I checked my 1.5 tire and it's rated for 125psi (I've been running it at 35psi). My 1 3/8 tires are rated for 45psi.
« Last Edit: April 17, 2011, 08:58:10 PM by REdiculous »
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taylorp035

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Re: Treadmill Dyno
« Reply #104 on: April 23, 2011, 05:18:27 PM »
Yesterday was a success in general.  We ended up converting an engine to run on points and a coil, which turned out very good.  It looks like the engine that we will use in the final car.  We will probably transplant the flywheel and coil stuff to our brand new engine with the new head.  The we will port and polish it and do a final dyno run.

The coil set up used a lot of power.  While running, it was pulling 80 watts, , which made the coil really hot.  We had to install a switch so it wouldn't drain our battery pack so fast.

While running the treadmill dyno yesterday, the key that holds the 3" pulley on the treadmill motor came out.  Unfortunately, some of the material stayed inside and jammed the pulley on the shaft.  After about an hour of trying various things (hammer, pipes, hair dryer, C- clamps), we gave up and decided to keep running the dyno.  After a few more minutes, we sprayed some lithium greese inside of it.  Once we got it up to about 4k rpm, she decided to let go and fly off the end of the shaft.  The belt didn't fly too far, but the pulley spun on the table for about 20 seconds ;D  It took about 40 seconds for the treadmill motor to stop, since it had no load at the time.

When we got it all back together, we did a couple more efficiency runs using the brand new engine, which yielded 10.1 % compared to the 9.7% for the points engine.  Both percentages were lower, probably caused by the bent pulley.

Also, we got the solenoid clutch working.  Only about 10 min more work is needed for it to be done.  It does take two 14v packs to run it, but as long as it is reliable.

I also did a careful discharge of our lipo batteries to see if they could hold 14v while under load.  It turns out that the computer actually needs >14 volts to run, but putting 26v to it would cause too much heat in the voltage converter.  I ran the 1350 mah 4s lipo pack at 4 amps.  It finally dipped below 14v after 1183 mah, so I deemed it a success.  The computer will pull less than 1 amp.

The carbon fiber for the cooled seat fan was finished and the cupholder was also worked on.

Sorry for the lack of photos.  My camera was accidentally left on and the battery was dead.  Next week, the car should be back from the paint shop and we will put everything in it --> lots of photos then.


EDIT:

I looked at the data from yesterday's dyno runs and calculated the efficiency.

Once I added the # of lightbulbs in, the numbers came out as follows:

The points engine was 10.0% efficient at 1.4 hp.  Peak power was a new record of 2.36 hp.

The brand new engine was 11.3 % efficient at 1.54 hp.

Both efficiency runs were done with the same mangled pulley, hence the lower numbers when compared to before.  The belt was jumping a quite a bit due to the pulley.


I think next week we should add the coil and points to the new engine and possibly port + pollish the intake and exhaust.  I think there is a good chance that the new engine has some differences that may increase the efficiency.
« Last Edit: April 23, 2011, 06:46:43 PM by taylorp035 »

taylorp035

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Re: Treadmill Dyno
« Reply #105 on: April 26, 2011, 05:26:06 PM »
« Last Edit: April 26, 2011, 06:08:52 PM by taylorp035 »

Bruce S

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Re: Treadmill Dyno
« Reply #106 on: April 26, 2011, 06:29:48 PM »
That second one sounded like you have something hitting? Nice response to the governor or throtttle.
 
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taylorp035

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Re: Treadmill Dyno
« Reply #107 on: April 26, 2011, 07:00:32 PM »
We aren't sure yet what the sound is yet.  It has the ringing sounds from the flywheel, which suggests that it is the gap on our cam lobe (you can't see it in my pictures) hitting the point.
All of this is on the brand new block, which makes the engine sound significantly different. Much smoother and quieter.  Probably due to the better muffler (last one was pretty much a straight pipe).

As for speed, it really accelerates.  Much faster than even the EFI engine.  Probably capable of doing 2k to 5k in under a second (almost as if it has no flywheel).  With no clutch on the shaft, the flywheel almost stops during the revolution around 800 rpm.  Our throttle didn't have a return spring, so sometimes while we weren't holding it, it would shoot off to 5k+, which is pretty scary with a homemade flywheel that is held on with essentially 1/16" thick aluminum...  Definitely need get our bicycle speed selector hooked up for the throttle cable.  Top speed is probably near 6k, but the con-rod will break.  B&S says the redline should be 4k.

This friday we should port and pollish it and throw it into the car (I hope it comes).

Unfortunately, we shorted out the Doc Wattson twice in the last week, and it looks like the second time killed it.  While we were running the engine, a wire broke off the kill switch and touched our metal table  :(






Madscientist267

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Re: Treadmill Dyno
« Reply #108 on: April 26, 2011, 09:28:27 PM »
What's your dwell on the points?

Not sure exactly of the 'antics' (lack of a better word) of a doc wattson, but if thats average current, ~5A seems WAY high. Is the coil warming up?

It made me think of a story my parents told me about a trip from connecticut to florida in an old 6V beetle, where during a stop for fuel, the regulator on the generator stuck shut and fried the genny. My dad ripped a wire off the generator (details escape me) to stop the fire, leaving the system with no starting or charging capabilities.

They ran the remainder of the trip off the battery, parking at the top of hills and such to restart the engine, driving only during daylight (it apparently crapped out mid afternoon), and stopping when it rained so they didn't have to run the wipers.

How does this apply? If the average current for them was as high as what I'm seeing here, the battery would have croaked north of DC.

They never mentioned charging the battery throughout the trip (even after the short sucked some juice out of it).

Your points should be open most of the time, only briefly closing just in time to open again to fire the plug. 5 degrees comes to mind as a general rule, IIRC. The less the better, but too small and the contacts get bouncy and firing becomes irratic.

Definitely explains your excessive battery drain.

Steve
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taylorp035

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Re: Treadmill Dyno
« Reply #109 on: April 26, 2011, 09:47:43 PM »
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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.

Note:  We have to use the 1350 mah 4s Lipo  (rule says <1400 mah and 12v).

I would guess the point is open closer to 10 degrees.  This may be too long.

Quote
Your points should be open most of the time, only briefly closing just in time to open again to fire the plug.

I see what you are getting at.  Making a lobe that shape would be more difficult.

Since we are only running the engine for a few seconds in the car, this shouldn't be a problem, but things do get toasty on the table.  Quite honestly, the engine will probably overheat before the coil does (limited air cooling).  I am seriously thinking of installing the extra 0.2A 12v box fan in the engine compartment to keep things happier.  The carbon fiber will melt too if things get too hot (the engine plate, the axle mounts,....).  The tire will probably explode too.


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Re: Treadmill Dyno
« Reply #110 on: April 26, 2011, 10:40:52 PM »
Many older vehicles used a ballast resistor in series with the ignition coil to limit the current (sometimes it was bypassed during starting).  I wonder if one could help here.  Since it's a relatively low compression engine it probably doesn't need all the energy that coil can produce to jump the gap.

If you want to try this I'd suggest adding 1-2 ohms (10 to 20 watts) in series with the coil with a switch across the resistor.  That way you can make a simple comparison to engine performance with and without the resistor in circuit.

taylorp035

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Re: Treadmill Dyno
« Reply #111 on: April 26, 2011, 10:49:53 PM »
That's a good idea.  We bought some 50w 1-ohm resistors which would work well for this.  Only issue would be finding a heat sink for it.  Maybe the engine mount rail.  Would have to be careful to not leave it on for too long.  I'm think we will have to buy another Doc Wattson for sure. 

Madscientist267

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Re: Treadmill Dyno
« Reply #112 on: April 26, 2011, 10:54:09 PM »
Good call on the ballast! I totally forgot about that...

Might even be able to get by with even higher resistance. 4R7?

That would bring things into the 2-3A firing current, and if dwell is set low enough, the average current would be in the mA range instead of whole amps.

Go with as little dwell and as high resistance as possible to obtain reliable spark under all conditions (RPM, load, etc). Your power requirements will drop significantly.

Steve
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taylorp035

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Re: Treadmill Dyno
« Reply #113 on: April 28, 2011, 02:10:37 PM »
I did another test today with the coil to see how many amps it was pulling with the LiPo battery (~15v under load).  Turns out it was more than 10A, at which point my multimeter wouldn't read any higher.

After running the engine for 2 minutes, the coil was 190 F....  We will definitely have to do something about it.  Based on our engine testing, the LiPo battery should last at least 2 runs.  We have 3 LiPo batteries, so we can swap them out every run.  One of those 3 will have to run the computer and probably the brake light.  Then I will need 1 or 2 LiFe batteries for the cooled seat and the last 2 for the clutch and starter motor....  That make a minimum of 4 separate circuits, 5 to make things happy.  I hope the computer runs on 12v, which then we can have the computer, brake light, the cooled seat, and the starter motor all on one circuit.  If we can get the clutch tuned to the point where we only need 12v, then everything will be perfect.




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Re: Treadmill Dyno
« Reply #114 on: April 28, 2011, 05:08:59 PM »
Would it be possible to replace the two clutch solenoids with a pair of electric lock actuator motors from a car at the salvage yard?  At least they don't require any power to hold, only to switch states.

taylorp035

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Re: Treadmill Dyno
« Reply #115 on: April 28, 2011, 05:30:07 PM »
We have a servo that will is good for 300 in*lbs, which would also work.  Maybe we could actuate the starter motor and solenoid with the same  potentiometer (it has 3 outlet ports....).  Only thing would be that the starter motor would run while the clutch is engaged... it should work.


We also got an update from the paint shop.  They said they wouldn't be done til Saturday (last day of April like the promised...).  Hopefully we can pick it up then.
« Last Edit: April 28, 2011, 05:50:09 PM by taylorp035 »

taylorp035

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Re: Treadmill Dyno
« Reply #116 on: April 30, 2011, 03:55:21 PM »
http://www.youtube.com/watch?v=M54zXwjRp_o

http://www.youtube.com/watch?v=jW8IP-6N5Lg

These are the new videos with ported and pollinated intakes and exhaust.  Just from revving them on the table, the performance is much better, especially in the top end.  We must of hit 5-6 k at less than 1/2 throttle.

The intake originally had the cross sectional area a little bigger than a sharpie marker.  Now it is around 3/4" in diameter.

We also found out that our brand new engine was pretty much destroyed, caused by a lack of oil.  We are not sure how long we ran it for with no oil, but it wasn't very long.  After tearing it apart, we would some real nasty grooves in the cylinder wall and on all of the bearing surfaces.  The engine in my two videos probably has parts from 4 other engines at this point.


Last night, we also swiss cheesed all of the components on the rear axle, probably cutting 1/4 - 1/2 pound.  Also, the wheel covers were clear coated and the cooled seat fan was glued to the air duct.

Today, we are making a new axle for the starter motor.  Having a 4-axis mill makes flat spots a breeze ;D  I should have a video up shortly on that.
I have also been hard at work finding software to make g-code out of a 3D file.  Obviously the companies who sell this type of software are very strict about free software...


EDIT:  Milling some flat spots

http://www.youtube.com/watch?v=yyepHG6iGyE
« Last Edit: April 30, 2011, 05:12:29 PM by taylorp035 »

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Re: Treadmill Dyno
« Reply #117 on: April 30, 2011, 05:11:29 PM »
The first video... that engine seems to be smooth as silk!

"Rumble with 14 Robots!" ;D
« Last Edit: April 30, 2011, 05:13:24 PM by zap »

taylorp035

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Re: Treadmill Dyno
« Reply #118 on: April 30, 2011, 05:15:00 PM »
Quote
Insert Quote
The first video... that engine seems to smooth as silk!

"Rumble with 14 Robots!" Grin

Yeah, 14 robots was a new record, the old was 8 I believe.  None of the robots were mine.

As for the smoothness, yes it was very nice.  The videos don't give the rpm levels justice.  Much more impressive in person.

taylorp035

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Re: Treadmill Dyno
« Reply #119 on: May 02, 2011, 08:57:23 PM »
Was able to do 2 efficiency tests with the new ported and polished engine + points.  Came out to 9.4% at full throttle and 3800 rpm @ 2.36 hp (new record!).  At 2/3 hp, we got 8.7% at 2800 rpm.  Not sure yet why the numbers are so low.  I'm going to triple check my excel calculator, but I feel that it is the engine.

If things work out, my brother and I will spend the afternoon messing with the timing and different power levels.

The only variable at this point that has held constant with the lower efficiencies is the extra light flywheel.  I really don't want to give that up, but there is a good chance that this is a significant factor.  Adding mass to the flywheel will be difficult at best.

In a few minutes, I will run the mpg numbers vs. flywheel mass to see if it is worth it to have a lower engine efficiency.

EDIT:  After running looking at the graph, the difference in mpg between the two flywheels is 10 - 15%.  This is not quite as much as the current 20-30% less efficiency than the stock engine.
« Last Edit: May 02, 2011, 09:00:18 PM by taylorp035 »

taylorp035

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Re: Treadmill Dyno with a graph
« Reply #120 on: May 03, 2011, 09:58:18 PM »
Spent a good 6 hours with the dyno today.  Good news, we figured a good many things out that we didn't know, like the timing which resulted in some big gains.

The original image here :  http://i54.tinypic.com/vdguog.png


The blue is the stock engine and the red is from earlier this week.  The green is from later this afternoon after we replaced the curvy small diameter intake pipe with a larger straight one.  The difference is obvious.  Some adjustment in the timing also was done, but it should of stayed constant throughout the green data points.

Some more data for the green in the lower RPM range is needed.

As usual, we were fighting to keep everything from getting too hot.  By running only 10 cc of gas per run, we were able to keep the coil temp under 160F and the engine under 280 F most of the time.  Unfortunately, we did run a LiFeP04 pack down to 5v on the coil once.  I hope we didn't damage the cells.  I charged it as soon as I could (less than 30 seconds after the incident).  It help 2270 mah out of 2300 mah, so guess it is ok.



« Last Edit: May 03, 2011, 10:10:10 PM by taylorp035 »

Madscientist267

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Re: Treadmill Dyno
« Reply #121 on: May 03, 2011, 10:45:23 PM »
Gotta get that ballast in there at the very least man...

Alternately, another thought came to mind about this - Have you guys maybe considered CD (capacitive discharge) ignition instead?

Could probably trigger it optically, making tweaking much easier, and it's infinitely (ok maybe that's an exaggeration) more efficient.

Gotta be better than killing batteries in no time flat and cooking coils...  :o

Steve
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taylorp035

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Re: Treadmill Dyno
« Reply #122 on: May 03, 2011, 11:06:39 PM »
These are the parts that we have right now.  I don't see us getting new parts until next year.  Plus, a new flywheel or maybe a modified cast iron flywheel with a magneto may be an option next year.

One of our teachers today said the same thing today.  He said something about a 20-30 ohm ballast resistor.

In about 5 min, I'm going to get another doc watson and some more anderson powerpole connectors.  I then plan to also have a "Coli ON" light right in front of the driver so we don't burn the thing out.  More than likely, we will add some of our large 50 watt resistors in series to compensate for the 16 volts.  Having spark was never an issue today.

This morning, I was doing some mph vs RPM calculations based on our gearing and I figured we were hitting 4.5k rpm last year at 26 mph going around the track.  No wonder we only got 6xx mpg during those runs.  When the girl driver in our ground did her final run, she drove slower, more like 23-24 mph and got 777 mpg.  My max speed was 32 mph, which meant 5.5k rpm.... the rod should of broke by then.  While testing earlier today, we accidentally hit 164 volts on the treadmill, which is about 5.5k rpm  ;D  Good thing the lights were not hooked up.

We also hit a new max hp today, at 2.49 and held it there for 40 seconds.  The efficiency was 10.2% on that run.





Madscientist267

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Re: Treadmill Dyno
« Reply #123 on: May 04, 2011, 12:05:58 AM »
Yep limiting the current is the simplest way to fix your heat problem ATM.

5.5k RPM shouldn't be a problem for short runs.

I can't say for sure with the newer engines, but in the late 80s, a friend and I repaired lawnmowers as teens; in our infinite 'wisdom', we would hold the throttle plate completely open as a 'blow up now, not after I sell you' test, sometimes for 30 seconds or more. I don't know the actual RPM, never had any way of measuring it, but they were generally set for 3600 RPM by the governor. The pitch of the sound sometimes would be double (~7200) what it was at normal governed speed. Never threw a rod. The engines were known by HP back then, with the CC listed in fine print below. 3.5HP and (i believe?) 152cc. Its been a while.

But I know for sure the only snapped rod I ever saw on one was on a new engine run hard with no oil.

They were tough little engines back then, and from what I can tell, they haven't changed very much at all. The biggest differences I see (without taking a newer one apart) is that the governors are no longer available as the 'air vane', and the EPA apparently got their grubby mits in the mix, because there's no more mixture needle on the carbs anymore either.

I'm not saying it's a good idea necessarily to open them up like that, but every briggs I've ever abused in that manner took it like a timex. ;)

Man, I gotta quit aging myself hahaha

Steve
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taylorp035

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Re: Treadmill Dyno
« Reply #124 on: May 08, 2011, 03:25:34 PM »
As expected, the paint shop missed the deadline yet another time.  Monday....

We did wire up a 1 ohm resistor in line with the coil.  The coil was about 1.5 ohms, so a 1 ohm resistor would bring the coil voltage down to 9v or so and the total current should drop by 1/3 - 1/2.  We even got some thermal paste and a small block of aluminum to help get rid of the ~35w.


The dual action clutch actuator was also finished:
http://www.youtube.com/watch?v=YSGXKcXsJDM


The engine was also tested some more, now with the iso-octane.  Peak power jumped from 2.49hp to 2.92hp.  Treadmill motor was pumping out 118v at ~18 amps ;D  The intake pipe was also cleaned out a little more and the hole where the old fuel injector sat was covered over.  Efficiency was also calculated at about 12.3%, with the peak closer to 3000 rpm.  Some more work on the timing is in store.

Some calculations on the free wheel were also done.  Looks the torque caused by the bicycle clutch was about 0.18 in*lbs, which amounts to 1300 Joules over 9.6 miles, or about 1/3 of a burn, or about 1-2% of our mileage.  Therefore, the added weight of the hydraulic clutch has about the same negative impact on the mileage.

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... and that our highest possible gear ratio will now be a 8.33, which doesn't bode well with a higher rpm from the engine efficiency.


zap

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Re: Treadmill Dyno
« Reply #125 on: May 09, 2011, 11:24:16 AM »
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!

Bruce S

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Re: Treadmill Dyno
« Reply #126 on: May 09, 2011, 12:10:10 PM »
On the bright-side, it was found out now not the day of the race  ;D
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taylorp035

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Re: Treadmill Dyno
« Reply #127 on: May 09, 2011, 07:40:30 PM »
I saw the car with the whites of my eyes today.  Looks like they started painting it today....  Said it would be ready tomorrow.  It looks like they did a little body work.  The color at this point will be 100% white.

Bruce S

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Re: Treadmill Dyno
« Reply #128 on: May 10, 2011, 09:46:19 AM »
Nothing like coming down to the wire.
A kind word often goes unsaid BUT never goes unheard

taylorp035

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Painted Supermileage Car Photos!
« Reply #129 on: May 10, 2011, 08:37:48 PM »
The day finally came :)   :P 

Here is a walk around the painted car in HD ;D  (sorry for the bad camera work...)
http://www.youtube.com/watch?v=v71qYfvcudw

I took 91 pictures.... I chose 4 for you guys.  If there is a particular angle you want to see (I think I got 'em all, minus a shot under the car), just ask.

You can see the tear drop design quite clearly, especially from above.  Not to bad for a first car.












electrondady1

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Re: Treadmill Dyno
« Reply #130 on: May 11, 2011, 11:12:28 AM »
that is a very cool machine.
congratulations to all

Madscientist267

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Re: Treadmill Dyno
« Reply #131 on: May 11, 2011, 08:42:06 PM »
Agreed. ;)

Hopefully the demons in the power plant and drive train will work out in the entire team's favor.

Very nice job. You have all clearly put some serious work into this machine.

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?  ;D

As I write this, I envision a trip to California from Virginia for less than $20. This of course takes into account the currently astronomical $3.79/gallon down at the local 7-11, and allows the car to make well under 1000 MPG. The figure that came to mind was the "777", 3x my lucky number. ;)

Anybody ever considered it as an extracurricular activity once the official race is over? I would bet that the mountains would pose a significant problem, but a little bit of hybrid thinking might help with that... I know I would pay to see it! Or even help with that part of the design... ;)

Steve
The size of the project matters not.
How much magic smoke it contains does !