I am very new to the world of CVTs and there is a lot of information I have to learn. Since this is my first post to SnowmobileWorld, I'll give you a little information about myself and my project. I've only ridden as a passenger on a snowmachine. ;) I live up in Anchorage Alaska...so to most that must sound pretty weird.

I found this community by searching Google for "snowmachine CVT car", and came up with the thread below:
http://www.snowmobileworld.com/forum/index...showtopic=44531 (http://www.snowmobileworld.com/forum/index.php?showtopic=44531)

The first thing that might come to you when you read about my project and what I hope to acheive is "why". :) I like building my own equipment and figuring things out. I'm also plagued with trying to save money and in the end spend more. ;)

The project is an ATV style buggy. I don't want to use the term ATV too much here because it isn't exactly what would come to your mind when I say "ATV". I don't even know where to start. It will be built with a gambler sprint car chasis, a geo metro 1000cc engine (and possibly the metro 5 speed), 45x18" tractor tires, and toyota mini-truck axles. I imagine the finished weight will be around 2000lbs.

http://www.goodyear.ca/tires/tirecatalog/TSGSize.html

The tires weigh 132lbs each, and for now we'll assume the weight is about 1000lbs from the tires and axles. I'm not sure yet what the G10 suzuki engine weighs, or the tube chasis, but 3 people can lift the whole thing (minus the tires and axles of course!).

So, with that in mind here is my project. I would like to place a CVT setup in front of the 5 speed transmission in place of the clutch. I really like the feel of my Polaris 400 Sport ATV. Thats the drive behind this effort. That, and I don't like manual transmissions. :) I would like to keep the 5 speed transmission because with the transaxle welded it could serve as a transfer case. 4th and 3rd gears could possibly serve as High and Low "speeds", and of course reverse for going backwards. ;)

I have found information on my G10 engine from a Japanese website.
http://translate.google.com/translate?u=ht...Flanguage_tools (http://translate.google.com/translate?u=http%3A%2F%2Fwww.suzuki-w.co.jp%2Fhistory2%2Fcultus%2FculAA53_spec_1.html&langpair=ja%7Cen&hl=en&safe=off&ie=UTF-8&oe=UTF-8&prev=%2Flanguage_tools)

So, the 3 cylinder Metro engine:
HP: 52 @ 5,500RPM
Torque: 54.97ft lbs @ 3,500RPM

The 4 stroke Polaris Sportsman 800 has these peak outputs:
54.8HP at 6000RPM
51.8ftlbs at 4,800 RPM

I followed the curves on the Sportsman 800 and compared it to the G10 Suziki engine:

The G10 makes 52HP at 5,500 RPM, the Polaris 800 makes 50 at the same RPM.
The G10 makes 55ftlbs at 3,500RPM, the Polaris 800 makes about 49 at the same RPM.

I did that because hopefully someone will know the specs of the Sportsman 800 as far as weights and springs goes? That setup might provide a starting point?

I would like cruising RPM to be about 3,500RPM. So I guess I would like the clutches to be at 1:1 (or lower?) by 3,500RPM???

The powertrain will be the engine, CVT, 5 speed, -possibly- a transfer case, and then the toyota axles.

I'm not quote sure what a CVT can offer for a ratio range, but I imagine its 2.5:1 to .7:1?
The 5 speed offers me:
1st: 3.416:1
2nd: 1.894:1
3rd: 1.280:1
4th: .914:1
5th: .757:1
Rev: 2.916:1

The differential portion of the transaxle provides an additional 4.388:1 to all the above 6 ratios.

The toyota differentials are geared 4.38:1.

I would like a speed of 25MPH at 3,500RPM. With a tire circumfrence of about 139" that means a total reduction 18.4:1 at full speed...

3500/(((25*5280)/60)/(139/12)) = 18.42

That isn't a "hard" number by any means. However any more agressive gearing and it will be like driving a riding lawnmower.

4.388*4.38*.914 = 17.56 for 4th gear

So hopefully the CVT can comletely compensate for the rest. In the case that it can't, or where more speed control is needed there is also 3rd gear that could provide 24.6:1.

I'm not completely sure how the weight of a 2000lb vehicle and the goal ratio of 18.5:! at 3500RPM will all fit together, but I thought you guys would be up to the chalenge of specing out a nice setup. :)

I would like to buy as manu used parts as possible from a local snowmachine salvage outfit. I'm not sure what the differences, if any, there are between a snow machine and ATV CVT. The only thing I would like that a snowmachine CVT might not provide is a little engine braking.

So, what's the deal? :)

Sounds like quite a project ya got there! Some observations take em fwiw.

Those 3cyl's really shake so build good isolation mounts. I turbo'd one for 100hp and put it on a experimental aircraft (veri-ez) and vibration was a huge problem, cracked mounts etc. Pulled it off and went suburu power.

Try to get the max primary clutch shaft speed in the 7500-8500 range, maybe shoot for 8000. So if your spinning the 3cyl at 5500 use your gears to get the primary clutch to 8000. This will give you the belt speed and flyweight force for "typical" cvt operation using avaible parts.

Typical cvt is aprox 3.8:1 at engagement and 1:1 to .8:1 full shift, so those are the ratios your working with.

If you plan on using your reverse you'll need a secondary clutch and helix that is cut for reverse otherwise it'll be pretty clunky.

2000 lbs is alot of weight for a snowmobile belt to haul around unless you have some major gear reduction behind it.

If you plan on using your reverse you'll need a secondary clutch and helix that is cut for reverse otherwise it'll be pretty clunky.

2000 lbs is alot of weight for a snowmobile belt to haul around unless you have some major gear reduction behind it.
[/b]

I intending to put a manual transmission after the CVT to act as a range box and reverse gear. Here are some more of my random thoughts, as well as the belt killing tires. I want to have at least 18.5:1 (for "high" gear after the CVT)

I built those rims from scratch too. Go to this link for a bunch of good pictures. ;) The good ones are towards the end...
http://www.alaska4x4network.com/showthread.php?t=11129

I'm leaning towards an ATV clutch setup. They seem to be set to kick in at a much lower RPM and allow for a greater RPM range? I'd like to make an adaptor for the flywheel and hook the primary directly to the engine.

http://media.diywelder.com/images4/060405-06-me_on_axle_3121.jpg

http://media.diywelder.com/images4/060405-07-axle_side_3117.jpg

Hmm..sprint power.

Back in 2000 at Haydays/Minneapolis, I seen a guy have a 3cyl sprint engine in what i remember was an Indy 500 chassis.
The engine had a stub on the crankshaft tapered for a yamaha primary clutch then stock polaris secondary clutch.

The flyweights he had were custom 80 gram and chose a primary spring that would push the sled good with correct rpms. At 5000 rpms the sled would do around 85~90 mph.

I watched the engine idle, could barely hear it, very smoooth. He did not run the engine up.

....neato! :thumbsup:

For flyweights heavy enough I would contact Gerrard Karpik at http://www.teamfast.com/index.php?main_pag...=3&static_nav=1 (http://www.teamfast.com/index.php?main_page=infopages&pages_id=3&static_nav=1)
I chat with him about some flyweights he made for his Harley Davidson powered snowmobiles. He made some tungsten polaris style flyweights that were up to 120 gram - and this could be the ticket for proper flyweight.

tungsten = $$$ = Ugh price! :dazed:
.................................................
With a primary clutch on the end of a transmission that means even in 5th gear at 3500 engine speed, this will only turn the clutch to 4600 rpms.

I think it may be hard to find a flyweight mass / spring force combination that will provide enough push with that low of rpms. If there is a way to overdrive the clutch more to spin er' up around say 8000~8500 rpms for engine speed of 5500, I think you'll have something that will be easier to tune and because of the higher belt speed the load will be reduced on the drive belt. [torque is lower]

WOW!

I admire your enginuity!

However for reliability and parts availability reasons I would skip on the CVT addition.

Have you seen alot of the recent rock buggies built for competition? They will use a front wheel drive car drivtrain like you are planning and just turn it sideways. Then build some custom driveshafts and use the differientials for the gear reduction....

Just a thought towards something a little more simple...

Good luck!

Thanks. :) I've seen those, and that's how I planned on doing it at first, but I don't like manual transmissions. :) I like the tiny light engine. I guess I would like to do it for a learning experience...and hope it turns out good. :)


WOW!

I admire your enginuity!

However for reliability and parts availability reasons I would skip on the CVT addition.

Have you seen alot of the recent rock buggies built for competition? They will use a front wheel drive car drivtrain like you are planning and just turn it sideways. Then build some custom driveshafts and use the differientials for the gear reduction....

Just a thought towards something a little more simple...

Good luck!
[/b]

I bought the primary and secondary EBS clutches for a 1997 Sportsman 500. I also bought the PTO crank piece and the transmission input shaft. Those two items will save time and money when adapting them to the engine.

What causes cracks in the clutches? Excessive slipping of the belt? getting a clutch wet when its hot? How many belts can you go through on a clutch setup before the sheves need to be replaced?

Cracks can be caused by poor design (AC clutches...), no maintenance, bad engine vibration etc...

The sheave life can be a long time, you can remachine the faces to get them back to spec angle if needed... You can't really say that after "X" number of belts, the sheaves are shot. Other variables like offset and center to center, running conditions etc. are a factor in belt life...

So really heavy primary weights would help the transmission downshift at lower RPMs? Is the primary clutch mostly RPM sensing and the secondary clutch mostly torque sensing?

That is correct...one the clutch functions anyway...

Check on the web and their should be some really good info on design and theory out there...

It may be almost impossible to find a weight and spring combo that will work with this....