Torque converter

evmatt · #1 (**permalink**) 04-26-2009, 06:16 PM

I was wondering if anybody here has used the tried and true Comet torque converter instead whatever problematic transmission comes with the grubee kit? I have just finished my 2 stroke 66cc motorized bike and am interested in using a 2.5hp Harbor Freight 4 stroke for the next one. I don't know any other way than using a go kart torque converter?

HoughMade · #2 (**permalink**) 04-27-2009, 10:33 AM

I think a Comet Torq-a-Verter would work on that engine as the maximum rpm is about 3600. I would like to try the Comet, but with the more commonly used Honda and Huasheng engines that rev to over 7000 rpm, the 3:1 to .9:1 reduction from the Comet is not enough. We need closer to 3.5:1 to 4:1 from the gearbox (additional reduction from the final drive). If I could find a CVT that gave about 7 or 8:1 down low and 3:1 up top....I'd give it a try.

Youngbird · #3 (**permalink**) 04-27-2009, 10:55 AM

Also keep in mind that the smallest Comet is a 3/4" shaft bore and the Honda/HS engines are 5/8" shaft. You would need to sleeve it. There should not be any problems with the setup however so long as your ratios work out right.

HoughMade · #4 (**permalink**) 04-27-2009, 12:23 PM

I have seen listings for a Comet with 5/8 shaft (340), but never found anyone who actually had one.

Youngbird · #5 (**permalink**) 04-27-2009, 12:27 PM

I dont think they are making a 5/8" shaft 340 any longer. I believe the smallest to be 3/4" unless you can find a 5/8" used. There really is no problem sleeving the crank to accept the 3/4 though.

spad4me · #6 (**permalink**) 04-27-2009, 12:35 PM

Quote:

Originally Posted by HoughMade

I think a Comet Torq-a-Verter would work on that engine as the maximum rpm is about 3600. I would like to try the Comet, but with the more commonly used Honda and Huasheng engines that rev to over 7000 rpm, the 3:1 to .9:1 reduction from the Comet is not enough. We need closer to 3.5:1 to 4:1 from the gearbox (additional reduction from the final drive). If I could find a CVT that gave about 7 or 8:1 down low and 3:1 up top....I'd give it a try.

Just a thought .
I am working slowly and cheaply on a cvt solution.
It seems that a thats dax 5 to 1 gearbox guts may fit on a cvt in place of most of the 3 to 1 geared transmission part of a cvt .
This requires a 78 mm clutch and a cvt as well as a thats dax transmission.
No guarantee you will be able to make it work at all. Just a thought.

You may be able to go from engine, to modified cvt, to dérailleur controlled multi speed freewheel.

Youngbird · #7 (**permalink**) 04-27-2009, 12:47 PM

Im looking at a Titan coupled with a scooter CVT using DAX's 10 tooth splined sprocket....Im theorizing here. Maybe coupled to a 3 sp internal rear hub.

*

* its working for LF.

Dan · #8 (**permalink**) 04-30-2009, 02:25 AM

Wondering if going from a 10T (on engine shaft), chain to 30T on the Torque converter mounted vertically behind the seat post, at low RPMs CVT is 3:1 then a 10T from CVT then to a rear sprocket of 54. Even at 10% power loss, with 26" wheel, would do over 30?

At 7000 RPM= 16.20:1 and 33.4MPH (not accounting for power loss due to slip)

At 2000 RPM=48.60:1 (has to be wrong) 3.2 MPH

I am sure I am missing some thing or folks would be building more with them.

Youngbird · #9 (**permalink**) 04-30-2009, 11:40 AM

On the Scooter CVT the ratios coming from it are 7:1 in low range and 3:1 in high range. The final drive(cvt to rear wheel) needs to be around 5:1 that wouls be a 10 tooth CVT sprocket to a 48-52 rear wheel sprocket. There is no need to add anything or customize the CVT in any way unless you just want to change the rollers or spring adjustment. Its good as it sits right out of the box. And as stated by LF...."its a bolt up, man!"

Dan · #10 (**permalink**) 04-30-2009, 12:09 PM

7:1, thats cool. Thinking of frame mounted engine with the CVT behind and remote so peddles will clear.