Treadmill Dyno

[SparWeb]

The previous hints would be located around page 7-8....

No way.  You never let on that you were considering a rotary intake/exhaust valving system.  That cyl head from last year had poppets just like any other.  This is totally new.  You will do away with the cam but you have to deal with sealing around the tubes against 100 atmospheres combustion pressure.  Heat is a transient problem, like you say, at least. 

[taylorp035]

Maybe I should of said just page 7, before the overhead rocker setup.  And you're right that I haven't given out too much info on this before.

You will do away with the cam but you have to deal with sealing around the tubes against 100 atmospheres combustion pressure.

Yep.... a 16:1 compression ratio is a blast to deal with.  It's safe to say that the spark timing will be fairly close to TDC, else too much pressure could develop.  Our current prediction is sitting around 7 MPa for peak pressure.  The design allows for the combustion chamber to leak excess pressure if it gets too high.

Heat is a transient problem, like you say, at least. 

Heat and seal wear are the two main issues that make this hard to put into a production car (but both are certainly manageable).  That's why it's so cool that we found an application (supermileage car) that we can effectively not care about these issues.  Design life of the engine is less than 20 hours... more likely just one hour. 

Hopefully I will have a few pictures of the components soon... the block and rotary valve have not been started yet.

These examples should keep the curious minds spinning for a while:
http://ralphwatson.scienceontheweb.net/rotary.html
http://home.people.net.au/~mrbdesign/PDF/AutoTechBRV.pdf

[SparWeb]

Awesome.
Here's to Taylor and his team bringing a very cool idea to life! 

[DamonHD]

Seconded.

And I raise my (virtual, it's a little early here) beer too!

Rgds

Damon

[taylorp035]

Here's to Taylor and his team bringing a very cool idea to life! 

I can't wait.   There is going to be a lot of attention drawn to this once it runs.

Here is the progress so far.... carburetor mount, bearing spring assemblies, large sprocket and the exhaust pipe.




It's scary to see how small the parts really are and how ridiculously stiff the springs are.... peak load on the valve from the cams will be in the ball park of 500 lbs!

[SparWeb]

And... They will hold a set of conrad bearings, which are clamped down on the turning shaft by the bolts.  Rather than pushing the conrad bearing against the bare shaft tube (which would crush it) you will have a reinforcing ring around it (not made yet).  The springs allow expansion (not that your motor will have much heat) and vibration and even leakage, like a pressure-relief valve, if necessary.  Those look like 1/4" socket-head capscrews.  Probably 60 ksi steel, so in tension only good for 1000 pounds...   ... I guess if the load is spread across the 4 of them there won't be any problems.  Again you avoid worrying about certain problems because heat doesn't build up (bearing grease, etc.).

[taylorp035]

Those look like 1/4" socket-head capscrews.

They are 5/16, with no threads where the aluminum will be sliding.  The max loads were assuming a worst case scenario for the pressure on the valve (port + seal).  We will probably try out a series of less stiff springs until it stops sealing, which of course will greatly reduce our frictional losses and make the engine run smoother (if a 16:1 compression ratio with an ultra-light flywheel at low rpms could ever run smooth.....)

Rather than pushing the conrad bearing against the bare shaft tube (which would crush it) you will have a reinforcing ring around it (not made yet).

Correct.  The valve itself has a 1/8" wall thickness, so it shouldn't crush.  The exhaust pipe on the other hand is designed to be very light weight, so it could be crushed with just your hand.

[taylorp035]

Super lightweight steering and suspension.  Everything is carbon fiber, except for the ball joints, thrust bearing, nylon bushings, and the shaft clamps.  The suspension part isn't quite done yet.







The front window is going to be thermoformed on Monday

Here is an awesome time lapse of making the body.  ~12,000 photos in total over 4 weeks.
http://youtu.be/UVbKQQ1BkuU

[DamonHD]

Good video, good teamwork, and good fun it would seem!

Rgds

Damon

[taylorp035]

We tested the power draw for our new dual spark ignition system and it only pulls 1 watt while running.  The old coil system was using up to 150W while running.   We also sorted out some low voltage cut off limits for our brushless speed controller for the starter motor, so now we can run our 1100 mah LiFE cells.  At full power, the starter pulls about 30A, which is asking a lot from those cells since the A123 cells never really did perform to their specifications.

Here is the steering in the car.  It fits just like the CAD model said it would.... with basically no clearance.  Currently, the axles rub on the outside of the body, so that will have to be adjusted a little bit.  Else, the firewall and side windows should be cut out this week.


The first attempt at the front windshield did not work out very well, so a bigger thermoforming machine and a larger piece of plastic will be tried next week.  The hard part is obtaining the plastic in the first place since it is so thin.  This is turning out to be a very expensive proposition to get this thing made.... three orders for plastic and three nose molds have had to be made and resurfaced multiple times    But it will be worth it to have a properly curved windshield, both for looks and aerodynamically.

[taylorp035]

Picture of the wheel skirts cut out, along with the giant areas for our wheel flaps.  There will be doors that cover the holes when the car is driving straight.  Tire changes will be a lot easier than last year, with it taking only about 10 seconds vs. 1/2 hour.



I guess the rest of the new stuff is still not ready for pictures, like our paint scheme and the visibility from inside the car.  The rotary valve engine should be assemebled by late next week.

Here is a video of the suspension being tested.
http://youtu.be/K-E2IrESWnA

[bart]

   Hardly ever post on this thread, but ALWAYS look!
To cool and great work!

[taylorp035]

   Hardly ever post on this thread, but ALWAYS look!
To cool and great work!

Thanks!  Major changes to the car should come more rapidly over the next few weeks as we get the rear sub frame, drive wheel and engine in the car.  Then we get to test drive it to see if all of our new ideas were good ones

And I decided that you guys could see our visibility situation and show you why a taller driver like me isn't going to drive.  As you can't see, my knees are directly in my line of sight forwards LOL!


Things will be much brighter inside once the very long side windows are cut.

[SparWeb]

Maybe (just maybe) the wheel fairings can be covered with a transparent material, which would allow much more side visibility.

[taylorp035]

Maybe (just maybe) the wheel fairings can be covered with a transparent material, which would allow much more side visibility.

They were clear in the last car, and they worked quite well.  The tricky part will be the new spoke covers for this year, which will probably be clear red due to a lack of choices where we bought the heat shrink material.  That will have to be evaluated later.

Here is what it looked like last year.  Obviously there is issues with everything getting dirty and reducing our visibility.
https://orgsync.com/22440/photos/albums/22949/photo/446349

Two years ago, it rained and our windows became very foggy, reducing visibility to almost zero..... the RainX and anti-fog wipes didn't help.

[taylorp035]

Shell Ecomarathon was just completed and it looks like Laval has raised the bar yet again with a spectacular finish of 3587 mpg, breaking the old record set at SAE supermileage of 3169 mpg.  I would also like to note that they did this on a track that in my opinion is worse for fuel mileage than at supermileage.

I think our car will be able to match theirs, since I think our aerodynamics will be better and we should weigh about 20 lbs less.  I would say they will probably have the more efficient engine, but we will have to see how the rotary valve engine does by the end of this week once we get it running.  Everything else should be equal, but who knows..... some of the finer details can be very important, of which I'm sure they are well aware of.

[Bruce S]

WOW! and here I am enjoying the hypermilage tricks I use to get above the 36/mpg in my 2010 Chevy .
A point of curiosity? How long would the engine last merely sitting and running? not stop /start stuff but running. Say as a stress test of the heating/cooling of the engine and components.
Awesome stuff! 
Bruce S

[taylorp035]

A point of curiosity? How long would the engine last merely sitting and running? not stop /start stuff but running. Say as a stress test of the heating/cooling of the engine and components.

A stock L-head, air cooled with the vent not over the fins: ~30 minutes of dyno testing.  At which point the oil starts to steam out of the crank case and the head temperature reaches 425F +.... not good for an aluminum engine.
A stock L-head with no oil: ~30 minutes before the cylinder lining and crankshaft surfaces are completely scored and ruined.  Then the rings will break....
Last year's OHV rocker 12.3:1 C.R. engine: about 1 minute at full  throttle (~3.3 hp) and it was up around 270F from room temp.
This year's rotary valve: ?  I'm guessing maybe 30-60 seconds.  The teflon in the exhaust bearing will melt first when it gets up above 500F.  The graphite port seal should  hold up well.  The piston will probably melt first due to the very high combustion temperatures and lack of cooling.... of which may be compromised if we decided to eliminate the oil in the crank case.  The new engine will also probably have all of its fins cut off and wrapped with insulation to keep it warmer ( as if a 150F engine compartment with no airflow wasn't enough...).  I think we should study the effects of a cold air intake by putting our 1500W heat gun up to the carb.....

If you had a stock engine with it just sitting, running say at 1 hp, then it would probably run forever until the oil turned into sludge or the spark plug gets fouled or dirt gets into the carburetor jets.  Or in our case last year, the points wear out b/c we were running the ignition on 16v and 150W for a single spark plug.

WOW! and here I am enjoying the hypermilage tricks I use to get above the 36/mpg in my 2010 Chevy .

Today, I tried my best going to work and improved my mileage by 20% over the previous day with 20.7 mpg in my Jeep.


We ran into yet another problem with thermoforming the windshield.... this time, we put the plastic sheets in a dryer to get the moisture out over the weekend and when we opened it up today to use it, the plastic was all melted together in a big mess.  So, attempt #3 with mold attempt #4 will be tried this Thursday.  On the plus side, the rotary valve head should be done, so I hope to personally assemble it tomorrow afternoon.

Here is the rotary valve


And the unfinished assembly as of late last week:

[SparWeb]

Are you sure you want to be showing pictures of the top-secret DARPA-sponsored ITAR-restricted engine valve?     Those foreigners at Laval might steal your technology!! 

More seriously, I'm a little worried about your schedule.  The engine's almost ready, but any dyno testing to tune it will take time, and exams are on about now.  Installing the engine, finishing the assembly, and shipping off to the racetrack all in the month of MAY is going to take some overtime shifts.
They're gonna call you Mr. Coffee Man by the end of this.

[DamonHD]

But universities *are* places for converting coffee into technology, yes?

Rgds

Damon

[electrondady1]

hard to believe, this is the same motor as my 1973 snow blower !
keeping my fingers crossed for successes .

[taylorp035]

Those foreigners at Laval might steal your technology!! 

Good luck trying to sort out all of the problems in just a month and then test it.  Let alone trying to obtain the parts that went into it.

Today, we glued in the port seal and the rest of the machining should have been finished... last I saw, the head was getting milled down to thickness and all that was left was the spark plug holes... of which are not going to be fun.  It's really cool to be able to see light through the inside of the carburetor   Before the engine runs, it will need some pins in the cams and a belt tensioner will need to be designed/made.

More seriously, I'm a little worried about your schedule. 

I say we are on schedule for driving the car around in about a week.  Today, we finished the tabs for the front wheel flaps and they turned out really good, so the body will be smooth up front.  Everything else is pretty much built.... just the final wiring and attaching the little things to the car.  The front wheel covers should go in this Friday, along with some final body filling and sanding.  The side windows were cut out last week and the front window is still being worked on, but it's looking like next Thursday for that.  I think this year, we have decided to not use marine epoxy for the windows, just packaging tape on the inside.

hard to believe, this is the same motor as my 1973 snow blower !

Yeah, it's a really old engine design.  They haven't really changed the shape of the L-head much, but over the years, Briggs has updated the internals, like the piston and the crank bearings.

[taylorp035]

Update:
The engine is almost ready to run.  The belt tensioner is halfway done and we received two new sets of springs to play with that are a 2-3 times less stiff to keep the valve in place.  We also installed the larger starter motor for initial testing (obvious reasons ), with plans to run the super mini starter later.  The rotary valve seems to be holding compression to some amount, so that's good news, which also must mean the head gasket and spark plugs are sealed.


On the rest of the car, the supports for the internal front wheel covers were installed, along with some work on the front steering and the rear tail light windows.  The computer for the car should be done this week too.




I was doing a little math, and it looks like we only need 1.2 hp at 20 mph to get the acceleration that I was looking for and still be at approximately half of the available traction on the rear wheel.  The cool thing is that the calculations suggest about 1.2 hp at 3k, so let's hope they are right.

[taylorp035]

The day has finally come!

EDIT:
More info will come once we put a load on the engine and get some numbers out of it.  It took us 3 hours today before it even kicked once.  I was surprised by how smooth and quite it was.  It sounds just like a normal engine... I was thinking the hollow pipe would make a funny sound, but it didn't.

[bart]

   Sweet!

[taylorp035]

Video #2 from today, with some more rev's this time around and  visible tachometer (x10 scale) on the right that works 30% of the time.

It was going well initially today and then it decided that it didn't want to start anymore.  So after 2 hours of cranking it over, we ripped the whole thing apart and found this:


The graphite seal should reach all of the way to the top of the aluminum head.... hence we had a giant vacuum leak.  The graphite was only 0.025" thick there and it was the leading edge, so I was actually surprised it lasted this long.  A new seal will be made from oil impregnated bronze ASAP, but until then, we filled in the gap with some JB Weld, so it should run tomorrow.  Then it should get hooked up to the dyno for some WOT runs

For scale, the head is about the size of a deck of cards, maybe a touch longer.  This picture was after we had cleaned the vast amounts of oil and graphite dust off of it.

[taylorp035]

The JB Weld and a combination of super glue worked for about 30 seconds for the 3 times we made it run today.  But then the JB Weld would crack and we would have a vacuum leak.  A bronze seal should be made tomorrow.

Here is today's video, with even higher rev's and a view from the backside and up close.

[SparWeb]

Did you also mention "Teflon" a few pages back, or am I thinking of something else?  I'd examine that too.
Agree with the choice of brass.  If fact, here it is in the BOM on a drawing right beside me!

Any other scoring or damage worth mentioning so far?

[Frank S]

in looking at your design I think I understand the idea of using a cam action on your rotary valve. Correct me if I am wrong but in your application you are using the lobes of the cams to increase the sealing capability. If this is the only reason for having them then it appears you are creating a percussion effect on your seal which if this is the case any material with a density substantial enough not to be effected will create  higher friction and cause wear.
 would it not be better to reduce the lobe height and round out the apex of the lobes to a larger smoother radius?
 A friend of mine about 15 years ago was working on a rotary valve for a 4 cylinder engine
at first he tried a pure cylindrical tube valve he eventually wound up with a complex system but it worked

[taylorp035]

Did you also mention "Teflon" a few pages back, or am I thinking of something else?  I'd examine that too.
Agree with the choice of brass.  If fact, here it is in the BOM on a drawing right beside me!

We did mention teflon.  We could still use it, but I was worried that it would wear too fast.  I would also have to check for thermal and bending stresses.  And the operating temperature is a little on the low side.  We are making a seal out of oil filled brass right now - SAE841 grade.

Any other scoring or damage worth mentioning so far?

Surprisingly no.  The wear rate was very low too, considering the amount we have run it.

Correct me if I am wrong but in your application you are using the lobes of the cams to increase the sealing capability.

Kind of.  The cams are there mainly to counteract the changing cylinder pressure, so the valve doesn't just fly off the top of the head.  Hence the actual force of the pipe on the seal is relatively low.

A friend of mine about 15 years ago was working on a rotary valve for a 4 cylinder engine
at first he tried a pure cylindrical tube valve he eventually wound up with a complex system but it worked

Interesting.  I have only seen 3 other 4-stroke engines with the valve shaped the same way as ours.  And all of them utilized a split head design with beefy bearings holding it firmly in place.  We obviously decided to skip the bearings and the top half of the head.  This greatly simplified the sealing situation.  But it also required a lot more calculations to make sure the valve was going to stay in place..... trying to accurately calculate the pressure inside the cylinder with no real world data was a lot of fun.........but a challenge I was happy to take up.  Spark timing and the volumetric efficiency play huge roles in the peak cylinder pressure.

I think I can also safely say that this engine is the highest compression ratio of any rotary valve engine at 16:1.  We might even try to go higher, but the calculations don't seem to support higher efficiencies.  Doing a rotary valve diesel engine would be interesting.

EDIT:
Thermoforming attempt #4 went a little better today.  The results were a windshield that was free of bubbles and about 70% formed in terms of shape.  The vacuum on the machine didn't get sealed around the plastic, so we had to make some modifications to the machine.  I have high hopes that it will work when we make the window early tomorrow morning.  We are also hoping to finish making the new port seal tonight.

EDIT2:
A serious thermoforming set up right here 
https://d1q9wbuypc40mm.cloudfront.net/jx51e2zfzmsipf4.jpg

[SparWeb]

...oil filled brass right now - SAE841 grade...

That could crack under the action of the cams, too.

I was thinking of 36000 or 54400 grades (the "free machining" kind).

...A serious thermoforming set up right here 

I've always wanted to build one of those.  The world needs more curvy shaped windows.

[taylorp035]

I've always wanted to build one of those.  The world needs more curvy shaped windows.

Now the world has a few more:

The final product turned out halfway decent.  It's the right shape, but there are a few marks from the mold and it's slightly fuzzy due to a million microscopic bubbles.  I would give it a 7.5/10.  But from a functionality standpoint, it meets all of our requirements, including being super lightweight.

[taylorp035]

This morning we managed to get the engine to run once with the dyno hooked up and it put out ~0.9 hp at 4100 rpm for about 5 seconds.  It was not at full throttle, and we have no idea what the AFR was.  But, if you scale the the stock honda gx-35 performance at 4k of 0.6 hp *53cc/35cc = 0.9 hp.  So we must be doing something right.

In this video, I would say the peak RPM was about 5,000.