I am not sure on teeth count. According to Matt it is a 4:1 ratio. I will try and get a count when I am home.damcard wrote:Hey Drew, overall your setup is very similar to mine in that you have two stages of reduction, approximately the same sprockets on the second stage. I am using a 24" wheel though. I also have a 3220 on the way but a 5 turn. I know you are aiming for almost half the top speed I am. I am not looking for stump pulling torque, but high speed instead. What pulleys do you have on your drive unit? I think I see a 72t for the driven pulley. What about your motor pulley? Also, can you list out your calculations for the speed/ratios you have. I want to compare to what I am doing. I am about to order my sprockets and may order some extra pulleys. -David.
Kepler wrote:Very serious setup. I am a bit confused on how a rear cassette is added with this config though. I'm sure all will be revealed as the build goes on
Absolutely! We want to know the weakest linkliveforphysics wrote: Fix that wiring up and hit this thing with as much torque as you can, and lets see how she all holds up.
The throttle problem is what im trying to resolve for my bike at the moment like you say its just not controllable enough when pulling away or trying to do slow controlled riding. The twisting of the clamps is something that did on my bike and i overcome this like this... This is simular power I was putting through my budget freewheel hub and it did eventually brakedrewjet wrote:I got the wiring going, full throttle is available.
I AM OFFICIALLY SCARED OF IT!!!!!
Top speed is about 24 MPH. Need to hook up my CA to confirm. The throttle sensitivity of it at low throttle is too tight. You can't start from a dead stop, as it will just toss you off the back. So I peddle it a bit then ease into it. If I gun it at about 10 MPH it will power wheelie.
So far I have seen about 2800 watts, although it is hard to say for sure as looking down when the bike is trying to throw you off the back is scary.
Freewheels seem to be holding fine. I had some trouble with the adapter Thud made for me to go from Matt's drive to the 219 sprocket. It kept shearing the 2 10-32 Allen screws on the 2 flats ground into the shaft. I figured I would just drill and dimple the shaft, but it is hardened steel and laughed at my puny drill bits. So I put in 2 aircraft 10-32 screws that has a hex head on it. Tightened it down good and so far seems to be holding. I have a feeling the SRAM 3 speed wouldn't hold up to the abuse. I also don't think it is necesarry, I could just go to a smaller sprocket on the rear and have all the speed I want and I am sure it would still have crazy acceleration.
My next problem is the clamps I made. While once clamped down theydon't seem to be able to turn, but under all the pulling force of the motor it twists them around. One of the mounts is on top of the water bottle rivnut, so I drilled a hole and used a screw to try and index it. Still rotates. I haven't tightened the crap out of those mounting screws yet so I will try that next. It may take welding plates to the seat post to get it 100%.
Overall this is way cool, just need to fine tune it. Right now it is soldered up in Delta mode, I need to try in Y mode to see if a slower top speed will help out.