The torque converter idea is going to work, but it may require a lot of work.
The torq converter tav2 30 has a ratio of 3:1, which is mostly for torque.
Since 2.7:1 ratio is for providing torque at low speeds and a 0.9:1 ratio for overdrive at high speed.
Since the honda clone 6.5HP runs at 3600 RPM, with the torque converter and a 55 tooth sprocket on the wheel and a 10 tooth on the torque converter will give an speed of 51MPH, but since there is an overdrive the actual max speed will be 56 MPH, at low speed there will be a huge torque.
I do not plan to drive the bike at 56MPH unless it feels safe, but is good to have the extra power for safety (no longer driving on the side and sharing the traffic lane with large vehicles).
The only other way go keep the bike from not going as fast would be using a jackshaft since large sprokets for rear wheel go up to 55 to 56 tooth only, or using a smaller diameter wheel, a simpler method is not to speed when not safe to do so.
I think 55 tooth is the perfect choice.
At high speed the gear ratio will be:
55/10 x 0.9 = 5.0:1 which is a very low ratio, providing very high speeds.
At low speed it will be:
55/10 x 2.7 = 14.9:1 which is a very high ratio, and will be able to climb hills with no problems keeping a good speed.
The 55 tooth sprocket is needed since the gear ratio of the torque converter is 3:1, in our china engines that ratio is 83/20 = 4.1:1, therefore a larger sprocket it is needed to compensate for the lower ratio.
Another option is to use a jackshaft but it is not needed using the torque converter and a large sprocket.
lower ratio ==> higher speed.
higher ratio ==> more torque
I just got a torque converter off ebay for $104, it about 2 weeks I will have some results, the hardest part will be mounting the engine and having clearance for the pedals.
In comparison our china 70cc engines run at about 7000 RPM at full speed.
At 7000RPM using a 36 sprocket gives 36 MPH.
since the ratio it that case is 83/20 x 36/10 = 14.9 so we have a ratio of 14.9:1
in the case of the 44 tooth sproket it is 83/20 x 44/10 = 18.3:1 and at 7000 an speed of 30
with a 55 toot 83/20 x 56/10 = 22.8:1 at 7000RPM is 24 MPH.
Here in this case we either have torque or speed but not both.
All the calculations here were using a 26" wheel for diameter.
The big difference is that the torque converter will provide a variable ratio with will let you have torque and speed, the drive chain will also be shorter since the torque converter is about a foot long.
One thing for sure 12g (2.6mm) spokes will be required or better, I have not found a source for 10g spokes (about 3mm).
So far this is the theory, when I try the torque converter I will provide some results.
Do you guys have some recomendations for heavy duty rear whelel hubs, and source for 10g spokes, and also very wide pedal crank which might be needed for clearance with the engine.?
