Hi guys,
I stumbled across this forumn while looking for information on freewheels and things for my new motor drive design. What a great resource!
I especially liked the 71 page thread on Matt's motor drive...took ages to read through but I discovered several things and confirmed other design ideas (like using the 15mm wide GT2 pulleys and belts from the start).
Whoever found the white's freewheel from sick bike parts, high five! Perfect for my application. I didn't know before this thread that the Shimano freewheels were crap under side loads.
Anyway, on to my project. Before constructing my vehicle from the ground up, I want to add a series motor drive to an existing recombent tadpole trike, specifically an actionbent T1 (because I built one up for a few hundred $ out of several T1 factory reject bikes). It is a very comfortable style of bike to ride for hours, and with a motor to assist in hill climbing would be a total joy. But mostly I want to use this as a testbed for motor drive design.
I am going to start with a small motor, the Kollmorgen 400 watt brushless model that can be had quite cheaply (I paid $50 each, I think they used to be even cheaper). It seems to be *ok* quality, certainly the price is right. 400 watts through the gears coupled with say 200 watts of human power should pull the trike up most hills with ease, if a bit slower than the 6kW models you guys are making
I haven't exactly nailed down how best to incorporate the drive into the bike chain mechanics. I could either go with 2 freewheels and a fixed gear and have the pedals and geared down motor drive a jackshaft with the fixed gear going to the back 9 speed cassette (the T1 is a 27 speed trike). Alternatively, I could gear the motor down say 5:1, then another 6:1 driving the front pedal cranks at around 100 rpm (with a freewheel in the crank). This would give me 27 speeds of both the motor and pedals instead of 9 speeds of motor and 27 of pedals. Of course with this I have the sprockets up front always turning, even when I am not pedaling...
The things I most want out of the drive are lightweight, efficient, and durable. I do not care a great deal about going 25 to 45mph for 10 miles if I can go 15mph for 40 miles. Also, eventually I want to experiment with backdriving the motor to charge the batteries...not so much regenerative braking but more as a means to allow a constant rate and force of pedaling, even while stopped or going downhill. This would key into the 2nd feature of generation 2 of the vehicle. It is going to require a quite complicated controller, but I have some experience there.
Oh, back to the 71 page Matt's build. I like your idea of a 1.37" x 24 TPI adaptor so much I am going to try threadmilling them on my cnc mill. I am just going to grind off 3 of the sides of a 3/8" x 24TPI tap and run a helical interpolation on my mill to cut the threads into a aluminum round. Should be easy enough, and something you could also do on your cnc mill Matt. I'll let you know how it works out.
Any opinions on the series drive versus driving the pedal cranks?
Rick
I stumbled across this forumn while looking for information on freewheels and things for my new motor drive design. What a great resource!
I especially liked the 71 page thread on Matt's motor drive...took ages to read through but I discovered several things and confirmed other design ideas (like using the 15mm wide GT2 pulleys and belts from the start).
Whoever found the white's freewheel from sick bike parts, high five! Perfect for my application. I didn't know before this thread that the Shimano freewheels were crap under side loads.
Anyway, on to my project. Before constructing my vehicle from the ground up, I want to add a series motor drive to an existing recombent tadpole trike, specifically an actionbent T1 (because I built one up for a few hundred $ out of several T1 factory reject bikes). It is a very comfortable style of bike to ride for hours, and with a motor to assist in hill climbing would be a total joy. But mostly I want to use this as a testbed for motor drive design.
I am going to start with a small motor, the Kollmorgen 400 watt brushless model that can be had quite cheaply (I paid $50 each, I think they used to be even cheaper). It seems to be *ok* quality, certainly the price is right. 400 watts through the gears coupled with say 200 watts of human power should pull the trike up most hills with ease, if a bit slower than the 6kW models you guys are making
I haven't exactly nailed down how best to incorporate the drive into the bike chain mechanics. I could either go with 2 freewheels and a fixed gear and have the pedals and geared down motor drive a jackshaft with the fixed gear going to the back 9 speed cassette (the T1 is a 27 speed trike). Alternatively, I could gear the motor down say 5:1, then another 6:1 driving the front pedal cranks at around 100 rpm (with a freewheel in the crank). This would give me 27 speeds of both the motor and pedals instead of 9 speeds of motor and 27 of pedals. Of course with this I have the sprockets up front always turning, even when I am not pedaling...
The things I most want out of the drive are lightweight, efficient, and durable. I do not care a great deal about going 25 to 45mph for 10 miles if I can go 15mph for 40 miles. Also, eventually I want to experiment with backdriving the motor to charge the batteries...not so much regenerative braking but more as a means to allow a constant rate and force of pedaling, even while stopped or going downhill. This would key into the 2nd feature of generation 2 of the vehicle. It is going to require a quite complicated controller, but I have some experience there.
Oh, back to the 71 page Matt's build. I like your idea of a 1.37" x 24 TPI adaptor so much I am going to try threadmilling them on my cnc mill. I am just going to grind off 3 of the sides of a 3/8" x 24TPI tap and run a helical interpolation on my mill to cut the threads into a aluminum round. Should be easy enough, and something you could also do on your cnc mill Matt. I'll let you know how it works out.
Any opinions on the series drive versus driving the pedal cranks?
Rick
