So, I'm long overdue for an update.
I went to visit Matt (recumpence) last week to check out his workshop. He put together one of his drives for me with all the parts.
But I'm now faced with a few more obstacles. I need to now mount the drive to my frame, probably using the clamp mounts very similar to the ones that Miles drew up in Alibre.
My next obstacle is clearance for my rear sprocket. My motor constant is 215 Kv (experimentally verified), rear wheel is 26" dia., and my battery voltage is ~40v. Matt's drive is 5:1. The smallest freewheel that will fit Matt's drive without modifying the freewheel adapter is a standard ISO thread 16 tooth. Doing the calculations to figure out what size driven sprocket I need to achieve a reasonable top speed comes out to about 56 teeth.
Correct me if I'm wrong, but I believe that the diameter of a 56T sprocket at 1/2" pitch can be calculated by multiplying the number of teeth by the pitch to get the circumference (28") and dividing by pi. So that would be about 8.9". That's pretty big. A lot bigger than disc brakes.
Well, to check if that sprocket would clear my chain stays, I cut out a cardboard circle about 9" dia. and stuck it where the sprocket would go.
No good. It's hard to see from the picture, but it definitely does not clear.
So now I have a few options:
1) Use a smaller sprocket
2) Sell the bike and buy a new one with wider chain stays
3) Use one of those motorized bike kit sprockets
Option one sucks because that means I'll have significantly less acceleration, a stupidly high top speed, and the motor will probably burn up. Option two sucks because it's just kind of a hassle. I don't have any particular emotional attachment to this bike but if I can avoid selling it second-hand for peanuts and shelling out even more cash for a decent replacement, I'd rather. Option three, then, seems to be the best bet.
Those sprockets mount to the spokes with a set of fiber washers on either side of the spokes holding it in place. This is how most of the cheap 2-stroke engine kits drive the rear wheel. The advantage is that this would allow me enough clearance to fit the large sprocket as it's a lot closer to the spokes, thus further from the chain stays. The disadvantage, though, is how difficult they are to install and center properly. I also don't like the idea of squishing the spokes like that. But a lot of people use these kits and seem to have no problem.
What do you guys think I should do?
I went to visit Matt (recumpence) last week to check out his workshop. He put together one of his drives for me with all the parts.
But I'm now faced with a few more obstacles. I need to now mount the drive to my frame, probably using the clamp mounts very similar to the ones that Miles drew up in Alibre.
My next obstacle is clearance for my rear sprocket. My motor constant is 215 Kv (experimentally verified), rear wheel is 26" dia., and my battery voltage is ~40v. Matt's drive is 5:1. The smallest freewheel that will fit Matt's drive without modifying the freewheel adapter is a standard ISO thread 16 tooth. Doing the calculations to figure out what size driven sprocket I need to achieve a reasonable top speed comes out to about 56 teeth.
Correct me if I'm wrong, but I believe that the diameter of a 56T sprocket at 1/2" pitch can be calculated by multiplying the number of teeth by the pitch to get the circumference (28") and dividing by pi. So that would be about 8.9". That's pretty big. A lot bigger than disc brakes.
Well, to check if that sprocket would clear my chain stays, I cut out a cardboard circle about 9" dia. and stuck it where the sprocket would go.
No good. It's hard to see from the picture, but it definitely does not clear.
So now I have a few options:
1) Use a smaller sprocket
2) Sell the bike and buy a new one with wider chain stays
3) Use one of those motorized bike kit sprockets
Option one sucks because that means I'll have significantly less acceleration, a stupidly high top speed, and the motor will probably burn up. Option two sucks because it's just kind of a hassle. I don't have any particular emotional attachment to this bike but if I can avoid selling it second-hand for peanuts and shelling out even more cash for a decent replacement, I'd rather. Option three, then, seems to be the best bet.
Those sprockets mount to the spokes with a set of fiber washers on either side of the spokes holding it in place. This is how most of the cheap 2-stroke engine kits drive the rear wheel. The advantage is that this would allow me enough clearance to fit the large sprocket as it's a lot closer to the spokes, thus further from the chain stays. The disadvantage, though, is how difficult they are to install and center properly. I also don't like the idea of squishing the spokes like that. But a lot of people use these kits and seem to have no problem.
What do you guys think I should do?
