CVT Anyone Using A Comet Torq-A-Verter?

[graucho]

This is not my diagram but ive found it helpful in the past.

A quick reference guide to the most popular sprocket ratios. In each row choose the number of teeth on your clutch. In the subsequent numbers, the first number is the number of teeth on your rear sprocket. The second number is your final drive ratio. A higher second number would provide more torque on hills and for heavy riders. A lower second number will provide higher top speeds. ie: 8.00:1 will be better on hills and 4.15:1 will provide more ground speed. In general, a ratio of 5.00:1 is suitable for street use while a ratio of 6.54:1 works very well on trails.

EXAMPLE SHOWN IN BOLD: 12 TOOTH CLUTCH - 60 TOOTH REAR DRIVE SPROCKET = 5.00:1 FINAL DRIVE RATIO

CLUTCH 09 TOOTH | 54 - 6.00:1 | 60 - 6.66:1 | 72 - 8.00:1 | 80 - 8.88:1

CLUTCH 10 TOOTH | 54 - 5.40:1 | 60 - 6.00:1 | 72 - 7.20:1 | 80 - 8.00:1

CLUTCH 11 TOOTH | 54 - 4.90:1 | 60 - 5.45:1 | 72 - 6.54:1 | 80 - 7.27:1

CLUTCH 12 TOOTH | 54 - 4.50:1 | 60 - 5.00:1 | 72 - 6.00:1 | 80 - 6.66:1

CLUTCH 13 TOOTH | 54 - 4.15:1 | 60 - 4.61:1 | 72 - 5.53:1 | 80 - 6.15:1

 

[DetonatorTuning]

thanks graucho. the pic is esp. helpful, i didn't realize the output sprocket is between the driven assembly and the backer plate on these.

i'm working with the pocketbike CVT's and they have a basic internal reduction which the belt system builds on.

in the case of the PB CVT's the overall present at the output shaft is 6.58:1- 3.15:1 before you start adding your final drive sprocket.

steve

 

[Nuttsy]

I'm working on a CVT project. It's not the Torque-A-Verter brand but it's alot cheaper and works great with some modification ( a 41 chain sprocket instead of the 25 it came with). I'm using a 12 tooth to a 44. Don't have to even pedal to get going! Don't know the top speed yet. Still tweaking and solidifying the mounts and need to install a chain idler. Also have a 14 tooth sprocket to try later for higher top end.
I'm liking it alot so far. Don't know why more people aren't using these. This particular one is for a GoPed and cost < $70 shipped. It's linked up to my Subaru Robin 35.
WC

 

[mlcorson]

Nuttsy:
That looks sweet...where did you source the CVT from?
-Mike

 

[DetonatorTuning]

Nuttsy, start up a thread about your build, it's going to get LOTS of attention.

good looking rack,although the cross members might be too close to the final chain as it wears in and lossens up.

 

[loquin]

The .9:1 is the high end ratio. Meaning, at .9, if the mnotor is running at 5000 rpm, the output shaft of the CVT is at 5555 RPM.

2.5:1 at engagement. When the CVT engages, it's at 2.5"1 reduction, therefore assuming the engine was at 5000 RPM, the output shaft runs at 1/2.5th of this, or, 2000 RPM.

Low end max ratio is 3.16 to 1. This tells me that, after the belt engages, the ratio could go even higher, if the load necessitated it. Again, if at 5000 RPM engine speed, the output shaft would be at 1582 RPM.

If you stepped the rpm down another 5:1, you'd have a rear wheel spinning at 316 RPM. Meaning that, on a 26 inch wheel, you would be running at 24.5 MPH. Ideally, if you wanted a top end of 30 MPH (388 RPM on a 26 inch wheel) at 6000 RPM engine speed, (allowing a little wiggle room for these small engines to wind out a bit more if needed) you would need a total reduction of 15.5, engine to rear wheel, and accounting for the .9 ratio on the high end of the CVT, you would need a total reduction after the CVT of 17.2. You would really need either a jackshaft or a gearbox after the torque converter to step it down. (Personally, I would like a freewheel sprocket on the final drive sprocket, and the smallest that I've seen is 17 teeth. 18 is more readily available.) A 54 tooth sprocket & an 18 tooth freewheel would give you 3 of the 17.2 total. Meaning that you still need another 5.7 reduction . A timing belt jackshaft would be very handy, I would think. A 1" belt would work nicely for this, between CVT and final drive sprocket.

Of course, you could modify a Staton gearbox, feeding the output of the TC directly into the input of the gearbox, and have a hub mounted freewheel. (1:1 from the top sprocket to the hub sprocket ) This would provide about 29 MPH at 6000 RPM for a top end, and under load, 9.1 MPH at 6000 RPM... That would really be a hill climber!

 

[5-7HEAVEN]

My 6hp engine is limited to 3600 rpm; no intention to remove governor at this time.

I don't believe TAV-2 and Staton gearbox will work together.

All I need is maximum 6:1, using jackshaft to centralize engine location.

The combination of sprockets to arrive at 6:1 ratio will be considered as soon as rear wheel arrives.

TAV-2 equipped w/10t sprocket was purchased on ebay today. I saved $43 by comparison shopping.

 

[Gungatim]

Nuttsy: Please post a link for the CVT if you can, I think a lot of folks would be interested in a small unit for that price. What kind of power can they handle?

I could have used one like this for my scooter build. The plans from the '50's called for a variable belt clutch made by V-Plex. I scoured the internet for a source, but all I found was a comet belt clutch that wasn't variable. Apparently V-Plex went out of business in the '60's. That CVT you used would have been the ideal replacement.

 

[wcocc]

5-7,
what type of bike are you running a 6hp motor? how heavy is the motor?

 

[5-7HEAVEN]

"The Iron Dragon" is a 2008 Raleigh Retroglide 7, men's model with 7 speeds. It is awaiting 203mm "downhill racer" disc brake and suspension fork.

The engine is a 6hp Robin overhead cam engine. It weighs 32 lbs and will be installed in a B.O.B. offroad trailer.

"BOB" trailer is being engineered to push "The Iron Dragon" to 40mph max speed, thus keeping up with commuter traffic.

The trailer weighs 13lbs before modification and carries a 70lb payload. With TAV-2 unit, new wheel, sprockets and reinforcing for engine and jackshaft, the completed push trailer should weigh 65lbs.