Author Topic: Treadmill Dyno  (Read 164187 times)

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taylorp035

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Re: Treadmill Dyno
« Reply #363 on: January 20, 2013, 11:19:19 AM »
Attempt #2 of doing to top carbon fiber.  This time there was no vacuum bag.  We also used a twill weave on the visible layers, so it draped over the mold much better and we were able to eliminate all of the relief cuts.  A slight modification to the location of the middle layer was done after inspecting the stiffness of the first attempt.


DamonHD

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Re: Treadmill Dyno
« Reply #364 on: January 20, 2013, 02:17:48 PM »
I like the high-tech cellulose-based multi-legged temporary support structures (ie wooden stools)!

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taylorp035

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Re: Treadmill Dyno
« Reply #365 on: January 20, 2013, 06:03:32 PM »
I like the high-tech cellulose-based multi-legged temporary support structures (ie wooden stools)!

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LOL!

They also make handy portable workbenches.... if you run out of space to put your tools down, just grab another stool.  At one point, we had 6 stools surrounding the car with various tools, including 5 sets of allen wrenches and 3 sets of socket wrenches... that was a nightmare trying to find our single 9/64" allen key, which most of the socket head cap screws in the car used.

The stools also come in handy since we technically don't own the table in the middle of the room, so permanently putting the car on it would result in that much more space that we don't really have.

Frank S

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Re: Treadmill Dyno
« Reply #366 on: January 21, 2013, 03:36:20 AM »
 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.
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taylorp035

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Re: Treadmill Dyno
« Reply #367 on: January 21, 2013, 03:40:11 PM »
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 haven't had the opportunity to check on the body yet.... I should have an update by later tonight.  I'm curious to see how heavy this is going to turn out.  The first try only weighed 4 lbs.... this one has more carbon and will have a lot more glue in it, so if it's less than ~7 lbs, I will be happy.  I was hoping for a total body weight of less than 12 lbs, with no windows, but anything under 15 will be good.  My goal is to get the car under 70 lbs total... and there isn't that much to make lighter from last year.  We had even swiss-cheesed the fuse box, so some serious creativity will have to come into play this year to cut weight from the internal components.  I believe the body was 22 lbs last year with no windows.  I think we will save ~3 lbs on the frame, 1+ lbs on the seat belt, 1 lb on the fire extinguisher, 0.5 lbs on the windows, 50 grams on the starter ESC, 0.75 lbs on the axles......   but the tires are going to weigh an extra 900 grams.  And depending on which engine we run, it may lighter or heavier and which size starter motor we have to use. 

Based on a few team websites, it looks like a bunch of the teams who skipped last year's competition should be there this year.  I saw several teams with perfect carbon fiber bodies made with CNC cut female molds.

taylorp035

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Re: Treadmill Dyno
« Reply #368 on: January 22, 2013, 09:28:51 PM »
I'm back give an update like I said I would on the body (a day late b/c of some crazy snowfall in the last 48 hours).

The body turned out really good.  I would rate it at a 9.5/10 considering that we did a wet layup with no vacuum and probably a 8/10 overall compared to any carbon fiber job, including vacuum set ups.  There are only a handful of spots where the carbon didn't sit down flat on the mold.  Luckily, many of those spots are where the windows go, so they will be cut out anyways.  Due to the wavy nature of the fabric, some spots may need to be filled in, but mostly likely a light sanding that just gets to the fibers and a bunch of primer should get the job done.

The tricky part for this Friday will be how to clean up the glue that dripped on the lower part of the mold before adding more carbon to the bottom of the car.

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Re: Treadmill Dyno
« Reply #369 on: January 25, 2013, 01:14:00 AM »
Random thoughts:

I can't see the release film all the way around.  It's visible on the wheel "pants" but nowhere else.  Problem?

Cardboard on the floor instead of plastic sheet?  Surely you can find a few empty pizza boxes, Mister Pizza Man!

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?
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taylorp035

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Re: Treadmill Dyno
« Reply #370 on: January 25, 2013, 10:13:56 AM »
Quote
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....

Quote
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.

Quote
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


From last week, we were able to use a knife to peel off all of the messy glue drips and carbon strands that were on the lower part of the mold, so tonight we will definitely finish off the bottom of the car.

taylorp035

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Re: Treadmill Dyno
« Reply #371 on: January 27, 2013, 12:47:30 PM »
Photo Update:


taylorp035

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Re: Treadmill Dyno
« Reply #372 on: January 28, 2013, 09:11:55 PM »
Photo Update #2.    Not too bad considering our limited resources and only gravity (or lack of it in the vertical sections) was holding the fiber on.  We were seriously thinking about doing the bottom in 3 stages by rotating the car on it's shish-kabob axis every 90 degrees, but the thumbtack idea seams to have worked quite well.

Most of the bottom is only 2 layers thick of 3K twill, with 3 layers on the very bottom where the main frame rail will be.  The bottom of the wheel skirts also have at least 3 layers, due to our super special wheel skirt design and the fact that we bottom out the car a lot (go figure!).  We are concerned that if our frame/suspension/steering snaps, the car would come crashing to the ground onto the wheel skirts.... which has happened many times with our previous cars.  If that happens in this car, the wheel skirts will collapse and the wheels will rip through the inside wheel covers and the top of the car, causing some serious damage and probably scare the living daylights out of the driver before coming to a grinding halt.

I hope to make the rear parts of the tail and wheel skirt more pointy when we add the filler to the surface.  In general, I am pleased with how the shape of the car turned out, especially how the tight radius above the front wheels turned out and progresses to the round tail area.  Looking at that curve on the computer was not easy and the white drywall had very little contrast to it to see the shape.   







« Last Edit: January 28, 2013, 09:19:26 PM by taylorp035 »

electrondady1

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Re: Treadmill Dyno
« Reply #373 on: January 29, 2013, 07:43:05 AM »
the shape is vaguely orca like.
should slide through the air nicely.
congrats.

taylorp035

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Re: Treadmill Dyno
« Reply #374 on: February 02, 2013, 05:40:06 PM »
the shape is vaguely orca like.
should slide through the air nicely.
congrats.
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.


Here is a close up of the lightweight filler we put on the bottom half of the car last night.  This was after we sanded out all of the high spots and dry spots from the surface.

taylorp035

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Re: Treadmill Dyno
« Reply #375 on: February 04, 2013, 02:41:54 PM »
Round 2 of of filler, plus some side by side photos.
We measured the car this morning and it's 4" longer in length, 1.5" shorter in height, and it should be 2-3" narrower in width.




taylorp035

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Re: Treadmill Dyno
« Reply #376 on: February 10, 2013, 02:14:46 PM »
Excavation of the foam  ;D

The body is much thinner than last year, but still plenty stiff enough since we didn't sand through any of the carbon strands this time.  We don't have the nose excavated yet, but I would say the lid is at only 1/3-1/2 as heavy as last year's.  It's also a bit shinier than last time, since we didn't use plastic food wrap that gets stuck in all of the folds.  I should have an awesome time lapse video of the excavation some time soon.

Sorry for the lack of a good inside picture.... I'm sure there will be plenty of those in the future.  Also, note that there was eventually about a foot of foam chunks under the car by the time we finished.  There was also 8' long 80-20 aluminum bar running the length of the car that we had to carefully work around and pull out.











« Last Edit: February 10, 2013, 02:55:57 PM by taylorp035 »

taylorp035

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Re: Treadmill Dyno
« Reply #377 on: February 13, 2013, 10:32:35 PM »
14.2 lbs total with all of the carbon, which beats our goal of 15 lbs set by Laval.  http://alerionsupermileage.ca/blog4.php/2011/05/26/a-little-gift

Considering we used no vacuum and a wet layup and had to add filler, I would say we did a really good job.  I think the absolute limit would be close to 8-10 lbs for the shell, with approximately 5 m^2 of surface area if done perfectly.  It's certainly a lot lighter than any aluminum or steel body could ever be for the same stiffness.

Pictured here (just the body) weighs 11.4 lbs.



SparWeb

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Re: Treadmill Dyno
« Reply #378 on: February 14, 2013, 12:00:52 AM »
Slick.

Will the driver be lying on his/her back or stomach?
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taylorp035

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Re: Treadmill Dyno
« Reply #379 on: February 14, 2013, 10:26:38 AM »
Quote
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.

If the car crashed, it would be from the nose or a side rollover.  Our 2010 car hit a solid object at ~8-10 mph during testing.... and the nose deformed in about 6" and then bounced back.  Having your feet down there in that situation would be a lot better than your head.  Hence the 4 point safety belt to keep the driver in place.  A roll over happens less that you would think.... our cars tend to drift and slide before rolling over.  In the 34 years of the SAE competition, only one car has rolled over, and I think it was because it went off the edge of the road.... a a combination of a narrow wheel base, 26" tires and a high center of gravity.  I'm not sure, but I also think that was the car that caused the "natural" steering direction rule.... turning left requires turning the wheel to the right can be very confusing.  Not to say that Behrend hasn't done this before :)
« Last Edit: February 14, 2013, 10:47:14 AM by taylorp035 »

taylorp035

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Re: Treadmill Dyno
« Reply #380 on: February 23, 2013, 10:17:05 PM »
The frame rail(s?) are now in the car, along with the roll hoop.  The entire frame rail weighs 1.76 lbs.... lighter than I bet any other team.



Here it is after the glue and C.F. was applied, along with a generous helping of gravity to bend the rails down to the body.



The only frame setup that could be any lighter would probably be a properly designed C.F. tube frame.  But spatial issues with having the frame around the driver would make this difficult and probably decently uncomfortable.  The 6" wide, 1/16" thick plate on the square tubes alone weighs 0.50 lbs.... making a hammock style seat with a tube frame would most likely be heavier, unless you very carefully used the bottom of the car as the hammock, and then use the tubes in compression to keep the car from collapsing.... just too many issues.  I like the simple 1" square tubes... if we need more stiffness, there are lots of ways to make it better without adding too much weight.

Frank S

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Re: Treadmill Dyno
« Reply #381 on: February 24, 2013, 01:41:07 AM »
Injecting high density foam into the tubing will stiffen them without much weight. High density urethane foam weighs 41 kg per m^3  2 tubes 1" by 1" by 6ft could hold only a couple of liters or about .082 KG.
  High density and low density foam injected into spars, ribs, booms & masts have been used on racing sail boats and aircraft structures for years to stiffen the members by as much as 300% in some cases depending on design shape.
 Without the use of foam in a leer jet it would need an engine from a 727 just to get off of the ground and the A380  could have never gotten off the ground no matter how many engines could have been strapped on to it   
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taylorp035

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Re: Treadmill Dyno
« Reply #382 on: February 26, 2013, 10:32:05 AM »
There is some foam under the frame rail, mainly so the driver doesn't break the top panel when they step on it.

After reading through the last 8 pages of this thread, I noticed you guys never saw a picture of my big sprocket I machined for the drive of this car.
Specs: 180 teeth, 17.98" diameter, 2.2 lbs, 7075 Aluminum, good for 600+ lbs of tension on the belt.  Used with a  12mm wide Gates carbon fiber stranded timing belt that has Teflon coated teeth.




Frank S

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Re: Treadmill Dyno
« Reply #383 on: February 26, 2013, 02:04:22 PM »
Nice!
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Re: Treadmill Dyno
« Reply #384 on: February 27, 2013, 12:13:39 AM »
That is a beauty.
Is the intent for the spokes to be in tension or in compression when the engine drives the belt?

Oh, wait.  I forgot.  The answer to that is "yes".  Poorly worded question.  Try again:

"Which way is it supposed to turn?"


Do not tell us how much that belt cost.
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Frank S

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Re: Treadmill Dyno
« Reply #385 on: February 27, 2013, 12:41:34 AM »
you just got ta love those programmable machining centers with their auto selection tooling carriages
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taylorp035

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Re: Treadmill Dyno
« Reply #386 on: February 27, 2013, 08:39:18 PM »
Quote
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).

Quote
"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.

Quote
you just got ta love those programmable machining centers with their auto selection tooling carriages
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.

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...).

Quote
Is the intent for the spokes to be in tension or in compression when the engine drives the belt?

Oh, wait.  I forgot.  The answer to that is "yes".  Poorly worded question.
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
« Last Edit: February 27, 2013, 09:30:26 PM by taylorp035 »

Frank S

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Re: Treadmill Dyno
« Reply #387 on: February 28, 2013, 02:23:42 AM »
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.

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...).

I know full well about machines not being large enough LOL
  Once I made a proto type injection mold for a special tire. The rubber company didn't want to spend the $100k for a mold for their production machine and the tool & die maker would not consider making a mold to fit a 60 year old machine. I could lathe out the inner mold parts but for the main cavities I had to use my Bridgeport mill and a turn table.
 The 2 mold halves  had to mate up to .0005" not easy on a 40 year old 3 hp Bridgeport with a 12 x 60" table
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taylorp035

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Re: Treadmill Dyno
« Reply #388 on: March 04, 2013, 03:04:38 PM »
I think it's finally time for the world to see the new engine design (two years in the making).  It is in the process of being machined right now and should be up and running in 2-3 weeks.  The only description I will give you right now is the left side is the intake.  We probably have 800-1000 hours of time into this so far.

« Last Edit: March 04, 2013, 03:08:42 PM by taylorp035 »

Bruce S

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Re: Treadmill Dyno
« Reply #389 on: March 04, 2013, 03:11:30 PM »
Ah, double over-head cam with timing belt:).
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taylorp035

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Re: Treadmill Dyno
« Reply #390 on: March 04, 2013, 03:31:40 PM »
But no poppet valves   ;D

Frank S

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Re: Treadmill Dyno
« Reply #391 on: March 04, 2013, 03:45:50 PM »
What about the heat transference from the exhaust tube to the timing belt? 
 Or am I looking at it wrong?
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taylorp035

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Re: Treadmill Dyno
« Reply #392 on: March 04, 2013, 07:23:20 PM »
"What about the heat transference from the exhaust tube to the timing belt?" -  Yes... it can happen.  But the engine runs for only 5-10 seconds during normal operation, so the exhaust pipe hardly gets got.  On our testing dynamometer, it is designed to run for 2 minutes straight..... we bought two belts, so if one fails, at least we will have an idea of what we can and cannot do.  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.

Frank S

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Re: Treadmill Dyno
« Reply #393 on: March 05, 2013, 05:56:12 AM »
"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.
 over 900 hp on the dyno but the entire exhaust side would get glowing red.
 but he was only looking at power out versus displacement for a few seconds of engine life.
 I only saw it run once for a few seconds and never saw it run up to full power or RPMs, but it sounded like a small turbo prop engine. but others were getting 900 to a 1000 hp using conventional valves. I always thought a pair of de-tuned quads to 500hp each would make an excellent  twin engine  light aircraft
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Re: Treadmill Dyno
« Reply #394 on: March 05, 2013, 02:56:11 PM »
I'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.  Counting teeth from crank to exhaust sprocket, I'd say it turns 1/2 as fast as the crank, just what you'd expect in a 4-stroke with 1 exhaust stroke every 2 revolutions.

I'll have to scroll back about 10 pages to see how this compares to the hints you were dropping last year.
No one believes the theory except the one who developed it. Everyone believes the experiment except the one who ran it.
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taylorp035

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Re: Treadmill Dyno
« Reply #395 on: March 05, 2013, 04:37:16 PM »
Quote
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....
« Last Edit: March 05, 2013, 05:03:47 PM by taylorp035 »