School me on convertors and clutches....

[Aaron871]

Does a "Torque-a-vert" or "Tav2" have different gears? How does it work?

Is a clutch the same as a torque convertor on a car? Or is it manuel, like a clutch on a car?

Are there different "stalls" available?

What other options are there?

How can I get low gears without using a large rear sproket?

[moto1fast]

Hello, Check out some of the earlier posts about the toque converter TAV2 there is some great info there. A clutch is automatic that engages when your RPM of the engine reaches a point higher than Idle. You can get them to engage at different RPM's. Like a Torque converter on a car/Truck. To get low gear ratio you would need to change sprockets to do that. Go with a TAV2 if you can or a Hortsman Competion clutch. The cheapo clutches will not hold up very good!! The Tav 2 is like a automatic transmition it changes gear ratio as Rpms increase so you have good low end and High end. It is the way to go on these BSR's.

[CritterBuddy]

Here's a quick link that may also help.

http://www.gokartsupply.com/comet.htm

If I remember correctly, seems like I read somewhere that a torq-a-verter's gear ratio goes from like 18:1 starting out to just over 1:1 at road speed. This allows the system to handle varying loads, road conditions, speeds, etc. better than just a centrifical clutch. Also, moto1fast is correct in that cheap clutches do not hold up well because they are either engaged or disengaged so if you go with a clutch be sure to get a very good one. By the time you buy a few centrifical clutches you could have already paid for a torq-a-verter system.

In my opinion and expereince, changing sprockets with a torq-a-verter doesn't really affect your ride very much that you'd notice or care because of it's ability to adjust itself. The one exception to this is you can increase your top end speed by going to a larger axle sprocket.

[Frozen Bohemian]

Good info on the TAV torque converter. I am planning on using one of these on the the current project.

What size rear sprocket are you guys using with this setup?
What is the front sprocket size on the units that run #35 chain?

Assuming 11" dia. rear tires and 6.5 hp motor.
I have a 66 and a 67 tooth sprocket I was planning on using, knowing I would give up some top speed (probably OK to keep it under 40mph).
I want a setup that has has a lot of low end pull.

[CritterBuddy]

Download this little program. It is great for calculating your gear ratio and top speed. http://www.gregorybraun.com/KartData.html

I don't have a BSR, have driven several, and am considering building one. My experience comes from the many Shrine parade vehicles I've worked on so can't help you with your question about the rear sprocket on a BSR.

Question? Do you realize how fast 40 mph is especially on a narrow framed BSR? The BSRs I've driven do about 18-20 mph and that's fast enough for me. Maybe I'm a coward. I'm sure others will chime in with more relavent information for you.

To use the little program listed above you need to convert your tire diameter to circumference by calculating it as: 11" x 3.14 (pi) = 34.54" This is your main limiting factor in trying to attain 40 mph.

Most small motors like Briggs, Honda, etc. turn 3600 rpms with no load. I generally use 3000 rpms in the program to allow for hauling my big asz around. If you remove the govenor from the motor like many racers do I believe it will turn about 6000 rpm. However, bear in mind this will limit the service life of your small motor so I won't use it in the following calculations.

If you use a TAV2 for a #35 chain it should come with a 12 tooth drive sprocket. If you are going to use the 66 tooth axle sprocket you mentioned then your estimated top speed will be about 17.84 mph at 3000 rpm. If you use the 67 tooth sprocket your estimated top speed will be about 17.57 mph - slightly slower but I doubt you'll notice.

To try and attain 40 mph you'll have to look at several factors. Like I said, your main limiting factor is your tire size. However, the BSR will be top heavy enough so I don't know you'll want to consider this.

To gain more top end, the smallest #35 axle sprocket I've found is 54 teeth. Putting this into the program gives you an estimated top speed of 21.81 mph.

TAV2s use a "C" type drive sprocket and as far as I know the 12 tooth sprocket is the largest they make for that type. If you're willing to do a little "engineering" to the sprocket, then you can use a "B" type sprocket with 20 teeth. This, in combination with the 54 tooth axle sprocket, will now give you an estimated top speed of about 36.34 mph. Pretty darn close to the 40 mph you mentioned.

One final comment. You mentioned that you wanted a lot of "low end pull". The beauty of a TAV2 is that it will adjust itself to whatever "load" you put on it. However, top speed and low end pull are a trade off - you can't have both. The TAV2 will give you the best low end pull with whatever sprocket combination you go with. However, maximizing the sprockets for 40 mph will negatively affect your low end pull even with a TAV2 . So the real question to ask yourself is what do you want the BSR to do, how will you use it the most, and what end result do you really want?

Good luck!

[Aaron871]

OK, I'm thinking about mounting a beer keg horizontal over my chassis for a seat (then my wifey can ride shotgun or in the "back seat":laughing: ). And it will let me mount the 11 horse engine that I've been looking at.

Question,
The tav2 says: Max 8 HP
But they have this one for 8-18 HP http://www.northerntool.com/webapp/wcs/stores/servlet/product_6970_200322170_200322170

But I don't see how ya hook it up? Where is the bracket that holds the rear pully?

[moto1fast]

That set up is designed for belt drive. No Chain! The rear pulley goes on a 3/4" axle. The engine clutch is 1" bore. The engine your looking at needs to have a 1" dia shaft! When you go over a 6.5 hp the crank shaft on engine goes to a 1" dia.. Some 8 hp still have 3/4" dia shaft. You can use that set up but you will have to remake your engine plate to fit back farther than in your plans. The Only real big problem with this is the Max axle size of 3/4". With the extra power of that engine I would not go with a axle smaller than 1" and would rather run a 1 1/4". The Only other option to make that Clutch work is to build a mid shaft setup behind the engine and run a chain and sprocket setup from the mid shaft back to your axle! A lot of work but would work great! With the room you will have under the keg you may even want to move the engine forward some to build your mid shaft setup! When you put a bigger engine than a 8 hp. you run into Drive set up problems. But nothing a little work, blood, sweat, and tears and about 2 cases of beer cant fix!! LOL

[CritterBuddy]

The setup at the Northern Tool link above is a separate "driver" and "driven" unit used for 9hp or larger motors. As moto1fast stated, they are normally used with a "mid shaft setup" (aka jackshaft) to accommodate the drive setup problems you normally encounter with larger motors. Though this setup does operate on the same principles as the TAV2, it is much harder to get setup correctly and really isn't needed for the application you guys are looking at. Keep it simple!

Stay with a TAV2 and 1" or larger axle. The TAV2 is self contained and will already have the right belt on it. The 1" or larger axle is beefy enough to do whatever you want. Trying to use a 3/4" axle is a pain.....

[Mike Bean]

Below is a link to the FAQ forum with some good discussion on TAV's.

http://barflyracers.com/showthread.php?t=774

Mike Bean