how mant teams use CVT?

[Scania]

how mant teams use CVT?

[Scania]

how mant teams use CVT?

[Mike Macie]

The university at buffalo team uses a CVT from Gaged Engineering (http://www.gagedengineering.com). They are designed for jr dragsters. Really small, light, and easy to package. Great customer service too.

There is usually a couple teams using a cvt at every event. I would estimate 10-15 teams worldwide.

[BYFE]

Why so few?

[Hector]

Because most teams use 600 CC motorcycle engines.

Almost all of these engines have a six-speed transmission that is mounted within the engine case.

Separating the transmission from the engine is nearly impossible.

Running a six-speed AND a CVT is dumb.

That's why =)

[Drew Price]

Separating them is difficult, but removing the shift linkage and 5 of the 6 gears and locking the trans in that one gear is pretty easy, removing both weight and rotational inertia.

That being said, these cars are so light that there is usually a substantial weight penalty, plus tuning a conventional mechanical CVT is really it's own specialty - you will note that many teams who use them are in areas where the students may likely have had experience with snowmobiles. There are whole books on the subject of tuning clutches and CVT's. You need accurate dyno prints of the torque curve for your particular engine and drive configuration to really do it correctly, otherwise it might end up hurting performance more than it would help.

Best,
Drew

[stealth]

How about using an engine with CVT?

Does it cost too much for an engine with CVT?

Any team using an engine with CVT?

[JagLite]

Using a snowmobile engine that is 4 stroke will be an excellent idea. The newer Yamaha Phazer four stroke (NOT the old 2-stroke) is a beautiful engine package. Fuel injected, liquid cooled twin with a CVT. While only 500cc, it puts out 80hp stock. And with the tuning available for the CVT you can maximize that horse power at all speeds with no shifting required.

So far, no teams are using it that I am aware of. Someday, someone will and I believe it will astound people. Someday....

James

[Klementina]

hm...wpi is using one this year...

[Prohet][]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">
So far, no teams are using it that I am aware of. Someday, someone will and I believe it will astound people. Someday....
</div></BLOCKQUOTE>

I totally agree. For the current SAE format, CVT can be a perfect part in the car.

It would take dedication to set it up and you would have to be willing to take the risk but once you got a year of using it and good knowledge it will mean you would get some great results.

I have heard of teams in the past trying out CVT but as far as I know, no team has stuck to one and tried to make it a good system over a couple of years.

[TorqueWrench]

University at Buffalo ran a CVT last year and, after the results, you can expect to see it again.

I will give you guys a heads up that you need to tune your engine differently to work well with a CVT and then the CVT tuning itself can take a long time to get it dialed in correctly. Our CVT had at least 5 parts that could be changed to affect the shifting rate, engagement RPM, backshift rate, etc. To complicate matters more, each part tends to have affect at least two of the clutches' characteristics.

[cwojcik]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by JagLite:
Using a snowmobile engine that is 4 stroke will be an excellent idea. The newer Yamaha Phazer four stroke (NOT the old 2-stroke) is a beautiful engine package. Fuel injected, liquid cooled twin with a CVT. While only 500cc, it puts out 80hp stock. And with the tuning available for the CVT you can maximize that horse power at all speeds with no shifting required.

So far, no teams are using it that I am aware of. Someday, someone will and I believe it will astound people. Someday....

James </div></BLOCKQUOTE>

The WPI team for the 2009 competition will be using the Phazer power plant. We have a team member who has CVT tuning experience.

[Type Q]

I have read that more outboard motors and personal watercraft are switching to four stroke motors. Those might be an intersting place to look for powerplants suitable for using with a CVT.

The first FSAE car I worked had a CVT. Converting motorcycle engine that already had a gearbox was a major pain. It lead to a spectacular failure when our student made output shaft broke. The primary came loose, hit the frame of the car and broke into about 25 pieces, some of landed more than 20 meters away from where it failed. We were (stupidly) running the car without any belt or chain guards in place. No one got hurt, but it was a little unnerving to be standing at the edge of a parking lot while pieces of the car landed behind of us.

[JagLite]

Fantastic!

Finally, someone will use the Phazer engine. You go WPI!

I am looking forward to reading all about your design and progress. And success too of course!

I just checked (and bookmarked) your website so I can keep up with your activity.

James http://fsae.com/groupee_common/emoticons/icon_smile.gif

[jsmooz]

JagLite - there were 2 teams that used the Pahzer motor last year (08). Michigan - Dearborn was one of them. I'm an alum of the team there and tho they did not prepare the car well there is much potential from that engine. Some of that has been mentioned already. Hopefully the second iteration will be more impressive as they plan to run it again this year.

[JagLite]

Thanks jsmooz,

I will see what I can dig up on the Dearborn car. If you (or anyone else?) can remember the other team, please post so I can follow their progress too.

I am not a fan of CVT's as such but for FSAE design and the events run as well as the variety of drivers I believe it is the way to go in FSAE. And the Phazer engine is very nicely designed for the cars.

James

Edit: I just did a search and have found nothing. The website is a couple years old so no help there. Anyone know of any information on the Dearborn car?

[Guillaume Villeneuve]

Last year at Detroit, the Université de Sherbrooke used a Phazer powerplant with a a different CVT from the one that comme with it. We'll be using a phazer powerplant too at the Université du Québec Ã* Chicoutimi this year with the original CVT.

Having team members that have done snowmobile drag racing is usefull sometimes...

[Kyle Roggenkamp]

We'll be running the Phazer motor as well. Half our team (read: 3) are avid snowmobilers with tuning knowledge, so hopefully that will ease the tuning process.

If this engine could be bored out to 600cc's, it would be hands down the best engine for this competition. We ran a KTM 510 single last year, and this engine is only 2 pounds heavier than the KTM. Coupling that with the CVT (which is superior to a traditional transmission) made it a no-brainer to run this engine for us.

[overdrive535]

Kyle-

Not being a yamaha expert (Go green or go home), does the Phazer have jugs or sleeves? And has anyone checked for big bore kits for it? Anyone who's punching it out should be able to help with upping the bore and sourcing pistons.

But that is just speculation...

[Kyle Roggenkamp]

I'm not a yamaha guy either- I bleed red.

The engine does not have individual jugs though, the cylinders are one casting with sleeves.

I have looked into boring the engine. There really isn't a lot of room to bore it out. It sounds like 1-2 mm and that's about it.

There are high compression pistons and over-sized pistons available for the engine...

[overdrive535]

Then it just isn't worth cracking the case for that little gain

[Kyle Roggenkamp]

Yeah, I think it could be punched out to 534 cc's, but I don't think it's worth it... But it would look better on the design report...

[JagLite]

The design report is an interesting subject.

From what I read it does seem that different judges view the design requirements with various opinions. The design guidelines being for an affordable autocross car for the "average parking lot racer" seems to be taken strictly by some and totally ignored by others. Must be very frustrating for the teams.

However, if I were presenting my design using the Phazer engine, I would stress the advantages of using a stock snowmobile engine that the owner can simply switch to his snow machine for the winter months and then put back in his autocrosser for the summer seasons.

This would lower the cost of the car as it could be sold "less engine" for those in snow areas and make the Yamaha Phazer snowmobile a year round recreation. For those who don't want a snowmobile, the car would be sold with engine. I think the dual cost breakdown should impress the judges and gain some points for intelligent engineering.

If the judges are going by the practicality aspect of the intent of the design competition this should be a major bonus. If the judges are looking for the most complex and expensive ways of doing things, it will not mean much.

I do read of many teams building a good car only to suffer in the events from engine problems due to their own desire to complicate things and try to get more power. Why shoot yourselves down by trying to reach too high? Maybe after the first year of experience with the motor it would be worth looking into raising the performance.

But that is just my view as an active autocrosser. Cars with motor work rarely beat a similar car with stock engine that is sorted out and well driven. Often cars with more power are slower as they require a very gentle driver that can overcome his right foot's desire to spin the wheels.

James

[Geoffct]

I'm with the University of Michigan Dearborn. We have run CVT's since 2005, initially on the Briggs V-twins and more recently on the aforementioned Yamaha Phazer.

Without giving away results of the hundreds of hours I spent, this engine was quite a nightmare. There are some inherent challenges on this engine. It is very hard to reach stock power on this motor. Sherbrooke turbo'ed it and made 64hp. Ours made significantly less power at competition, and now after a summer of dyno work makes a just shy of that.

The clutches are still limited on operating range, requiring a large final reduction. By hardening our drive sprocket, we were able to use *just* a 52 tooth driven. Sherbrooke used a 75 tooth saw mill looking sprocket.

The electronics side will also be a challenge. University of Maine? used the Phazer for their clean snowmobile, they ended up extending the crankshaft outside of the engine to get usable signaling.

I would highly suggest that you prove out the engine BEFORE committing your frame to major revisions that a CVT will mandate.

Geoff

[JagLite]

Hi Geoff,

Wow, sorry to hear the engine has caused such a pain for your team. I have never worked on the Phazer engine so I have no hands-on experience to appreciate what you are dealing with. It seems like such an ideal motor for the competition. But all the engines have their own problems and situations to overcome, eh?

Did you consider using a jackshaft to lower the gearing from the CVT to the diff? Are you using the stock wiring harness and ignition system? As well as the stock F.I. system? I am big on the KISS application guidelines, For me that means changing from what works (stock) to something else, only after the engine is running at peak performance, and then start experimenting.

Here at work (Engineering) I have a motto that applies (to everything actually).

The definition of a "Quick and Easy Job" is anything someone else wants you to do because they don't know how to do it.

I hope you are able to get the engine running well real soon.

BTW, what does the Phazer engine weigh?

James

[Kyle Roggenkamp]

Geoff those problems sound like a major pain in the ass. I hope we don't run into the same ones. We'll be working on getting our engine running next week... Our sprocket is going to be in the 64 tooth range, which is freaking rediculous, but necessary.


and fwiw: The Phazer weighs 78.5 pounds. The primary weighs around 10 loaded. For reference a KTM 525 weighs 76.0

[JagLite]

WOW!!!

78.5 pounds is fantastic. I will keep watching to pick up a wrecked Phazer someday to cannibalize. My two mid '90's Suzuki 600 four engines are 200 pounds each! But, for under $400 each for the complete good running bike they were in my price range. (Extremely limited budget build)

[Wesley]

In regards to what JagLite said,

What the judges consider to be important varies largely on the competition. In Michigan, the rule about "weekend autocrosser" doesn't mean jack. They want fancy engineered widgets that cost a lot of money. They want small, lightweight, carbon everything cars that will cost 5 grand to replace a corner on.

And OU has, almost every year, built a car that is, for the most part, for the weekend autocrosser. No fancy carbon tubs, no fancy titanium outboard. And we take a design hit. But you don't have to use this stuff to engineer something well! We perform well on the track, that much is certain. It's a simple design. But it is a well engineered one.

The vast majority of engineers that leave FSAE for industry will never touch a lick of carbon or titanium in their designs.

In California, the judges look more for robustness, for a car that isn't a peaked, about -to-explode car, that is marginal in ordinary areas but has fancy widget a and carbon component B.

In the case of a CVT, it's a good idea. But how easy will this be to use on the track? To repair? To maintain? Good engineering takes all this into account, not just extracting peak numbers. And many fellow FSAE'ers forget this.

Look at industry and motorsport. How many cars, how many teams, run a CVT? Why or why don't they? It's worth looking into. It's a great design exercise, but couldn't you spend your time working on something that will be more useful?

Basically, ask yourself if you're making a design decision just to make things more complex, or if theres a true gain to be had in doing so.

[TorqueWrench]

I can clear up a couple of questions Wesley brought up concerning CVTs.

On the track, it does require a different driving style to your traditional sequential car. Staying smooth on the throttle is key to let the CVT operate how it should. You also need to learn how to trust the CVT to work how it should, which takes longer than it sounds.

In terms of repair time, its great. We were out in Toronto this last weekend and the secondary siezed on us. He finished the lap with the secondary locked at a certain engagement and placed a decent time. We took apart and repaired both clutches in under 45 minutes. We could have probably done it much faster, but I had some new members doing it with me.

Maintenance wise, CVTs have been great for us. Very little maintenance was required on our clutches to keep them operating correctly. Main thing to do is just wipe the sheaves down before a run to get the dust/dirt off of them.

When it comes to why no teams in professional motorsports run CVTs, it could have something to do with them being banned in most racing leagues.

[Wesley]

Why did the clutches go out?

[rjwoods77]

The FIA banned CVT's when Williams F1 brought a car to silverstone in 1993 and it was much faster than the other cars. So like anything else cool they banned it. Just so you are aware the new KERS system for formula 1 that Torotrak has designed has a CVT inside of it. If it werent for the ban I am very sure that they would be the desired formula transmission.

http://youtube.com/watch?v=x3UpBKXMRto
http://hk.youtube.com/watch?v=6A9V2O5D8mc
http://www.forix.com/8w/altpower-cvts.html

There still hasnt been a team yet that has really gotten one of these setup right yet but just like anything else with some development with a smart group of people and it will cause a shift.

A couple notes for teams out there that want to use one:

A very heavy backshift is very desirable. This will limit the physical vibration of the belt and give you a very responsive feel when off throttle.

Your overall clutch setup should be for throttle response and not like a snowmobile where most of the time you are wide out. Mid throttle response is the name of the game. It is physically impossible to keep the engine spooled at some given rpm because your wheel rpm requirements vary wayyyyy too much. Some people get trapped in this thinking about perfect cvt blah blah blah. You will spend most of your time in and out. Setup for that.
Engagement should be real low. There are parts of the course that you will get dragged down real low no matter how good of a driver you are and how good your setup is. Set the engagement around 2000rpm because by the time the full engagement sets up (i.e. response time) you will end up around 3000-3500. You will get dragged pretty close to that low at times even with a high rpm engine.

That being said you need to have variable upshift control. At low speeds you actually want the cvt to hang for a little so you can make good effect of gearing for accel. At mid speeds you want it faster and at high speed you want it very fast. Multiple angle secondary ramps are the name of the game for this wether they are stepped or progressive radius.

A caged secondary helix is a must. The on/off throttle applications combined with sticky tires are much more faster reacting then a belt in snow. Without a caged secondary you will "float" the helix which will chew it up real quick.

Rollerize everything!!!

Last but not least judge validation. The first question that anyone asks/brings up is the efficiency and is it worth it. The only hard way to compare that is to do a tractive effort diagram for a cvt car vs. a shifter car to show that you get more area under the curve. ANy other explination/argument is useless. YOU NEED TO DATALOG SHIFT RATIO. You need to use a hall or vr sensor on the jackshaft and compare jackshaft rpm vs engine rpm. This combined with final drive will allow you to compare setups with each other. Just because it feels faster doesnt mean it is. The proof is in the data. More area under the curve along with a higher sustained longitudal g will give you the correct setup requirements. If you dont spend considerable time working on this you are shooting in the dark. You may be able to do this in house and show improvements but when it comes to judging they want to see that you actaully did it against data much like anything else in FSAE. Olav Aaen does it on his SSCA races and snowmobiles to get things setup best. You should too.

[TorqueWrench]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Wesley:
Why did the clutches go out? </div></BLOCKQUOTE>

Clutches went out because a roller was not properly tightened down on the secondary and it dropped off during testing. While the other two rollers could handle the added stress, the retaining pins that connect the helix to the movable pulley could not and they bent. When they bent, the clutch got jammed halfway engaged.

One thing to realize though. Even with this clutch having "failed", it was still capable of running. Driver hadn't even noticed it had happened and just commented on how he had lost a bit of power out of corners.

I'll second what Rob said about the data logging. There is absolutely no way to tune the clutches or defend using them. Tuning a CVT without some type of data acquisition is very difficult because driver feedback can be very misleading (drivers place a lack of changing RPM with a lack of acceleration). When I got asked why the CVT was advantageous to a sequential, I simply showed the design judges out data plots from an acceleration run and indicated the differences between our plot and a sequential car's plot.

[Wesley]

That's reasonable, not like we haven't fried a few ourselves.

What kind of weight for engine/transmission combination are you guys seeing?

[ccsharry]

Aston University in the UK used CVT on their 08 car. Heard they wasn't too happy with the heavy flywheel or something like that in their brake test... may be it worth contacting them if you want to find out more!!

[rjwoods77]

Primary is 5bs. Secondary is 2.7 lbs. Engine with everything I think is about 90lbs. But there is about 10 more lbs to come off due to a huge ass flywheel that needs to be replaced still. UB can get a more exact number next time they have it out and will post it up here.

[TorqueWrench]

Yeah, that steel flywheel is getting pulled off this week to do some testing with an aluminum one. I will get you guys an exact weight number for the whole engine/transmission package then.

[rjwoods77]

What are you going to do about the charging system if you are running the aluminum flywheel?

[Kyle Roggenkamp]

5 and 2.7 lbs? Are you running gaged clutches?

We are planning on running stock yamaha primary and a TEAM secondary... Big, but they will work well and tuning parts are available everywhere for them.

[TorqueWrench]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kyle Roggenkamp:
5 and 2.7 lbs? Are you running gaged clutches?

We are planning on running stock yamaha primary and a TEAM secondary... Big, but they will work well and tuning parts are available everywhere for them. </div></BLOCKQUOTE>

Yes, those are gaged clutches.

Rob, we are right now simply testing with the Al Flywheel to see what difference it makes. Our electrical team is looking into still utilizing a stator with smaller magnets or simply a slightly beefier battery. We tested the car the other night on the steel flywheel with no stator connected and managed 3 restarts with 20 minutes of driving in between before the battery did not have enough power to crank the engine over.

[y.o]

Does anyone interested in Honda Silverwing's? It's 600cc parallel twin with CVT, but probably a heavy engine. Several years ago I saw a Japanese Uni used it.

[TorqueWrench]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by y.o:
Does anyone interested in Honda Silverwing's? It's 600cc parallel twin with CVT, but probably a heavy engine. Several years ago I saw a Japanese Uni used it. </div></BLOCKQUOTE>

I just went and lifted the Silverwing that is sitting in our shop. It probably weighs 100-120lbs and that doesn't include the cooling system.

[rjwoods77]

Total loss electrical systems are extremely risky to use for comp. Especially if you have weak injector voltage compensation which is the case for us since. Actually all the sensors/hardware are voltage compensating so I would plead with you not to go without a stator. We go through this almost daily at Delphi when it comes to problem solving hardware issues. I would advise highly against it and shoot for a battery that doesnt run down (i.e charging system). The biggest difference will be the loss in weight for your goals this year. Other than that testing will show power wise but it should free up some losses and present less interia to get the motor revving up faster. Be sure to have someone read the flywheel section in "Design of Machinery" that Ian had. It will provide you with insight about how heavy the flywheel should be and the effects of power pulsations on the crank. I have always wondered the question about what effect the primanry has as a flywheel mass since it is a flywheel. Variable flywheel at that. If you do use the stock stator, which i highly recommend since you can always get a new stator and/or regulator for cheap and quickly, then you can figure out your magnet to stator gap in terms of a radius from crank centerline, measure the ID of the flyhweel where they would go and then model that in solidworks and have someone wore EDM the magnets out of a chunk of appropriate material. Then find an appropriate epoxy to bond them in.

[rjwoods77]

Pay attention to Brian Lewis from PE Engine Management's comments

http://fsae.com/eve/forums/a/tpc/f/125607348/m/43410336...10446621#93810446621 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/43410336621?r=93810446621#93810446621)


http://fsae.com/eve/forums/a/tpc/f/125607348/m/59710949...10949441#59710949441 (http://fsae.com/eve/forums/a/tpc/f/125607348/m/59710949441?r=59710949441#59710949441)

Remember this is a customer vehicle before it is a race car.

[TorqueWrench]

Rob, that was pretty much what we plan on doing. The stock stator is just too convenient not to use it and we should be able to get some smaller magnets made for the flywheel without too much of an issue. I'll get the guys who are working on the flywheel to read that section.

[rjwoods77]

By the way give me a call. I lost your number.