Hi there. I found this site in my pursuit to build an electric assisted bike.
Some backround on me: I've been into cycling/racing for the past 9 years since I was a teenager. I do a lot of road biking and some mtn biking now. I finally made the jump to tinker with an old mtn bike and strap on an electric motor, to save some gas going to work and mainly to just have some more relaxed fun.
For some of you unfamilar with power/speed requirements, I can tell you that if you get aero/lightweight, you can go 25mph or so on ~350watts. Well, that''s for a road racing cyclist. 35mph takes me about 800watts once I get up there. 6% grade uphill at 30mph = only 1400watts. I have a powertap powermeter that accurately measures watts. This is all dependant on an efficient gear ratio though. If you have a 2hp engine, it's not going to put out 2hp at lower rpms up a hill.
Point is, if you get light and aero enough, and are on an efficent machine like a road bike with high pressure tires, you can go considerably faster that what most of you are familar with. Comfort is an issue though.
Anyway, my project I am starting when the parts arrive is this. Bought 2 12v 17ah SLA batteries and a small 24v 350watt motor. With proper gearing this motor will perform better than what most people would expect.
(For example, if I put out 100% effort sprinting in a huge gear on my road bike, I might only produce 1000watts. But if I am in the correct gear, that same effort will get me 1700-1900w. With this in mind, you can see how important gearing and possible multiple gears are.)
I plan on doing a straight up circuit with an on/off switch, no controller. Since the motor is only 350watts, I really hope this is not a problem, concerning the electrics? (I have no problem with ride/speed wise with this type of on/off function.) I would think that a controller would end up soaking up power and decreasing efficiency.
My total cost should only be $150, (excluding the bike which I already have.) I going for pure simplicity and low cost on this setup. I will still pedal the bike on hills and starts, but I wanted the electric motor to take the bulk of the work on my relatively flat commute to work. I can't wait to get started on it!
Some backround on me: I've been into cycling/racing for the past 9 years since I was a teenager. I do a lot of road biking and some mtn biking now. I finally made the jump to tinker with an old mtn bike and strap on an electric motor, to save some gas going to work and mainly to just have some more relaxed fun.
For some of you unfamilar with power/speed requirements, I can tell you that if you get aero/lightweight, you can go 25mph or so on ~350watts. Well, that''s for a road racing cyclist. 35mph takes me about 800watts once I get up there. 6% grade uphill at 30mph = only 1400watts. I have a powertap powermeter that accurately measures watts. This is all dependant on an efficient gear ratio though. If you have a 2hp engine, it's not going to put out 2hp at lower rpms up a hill.
Point is, if you get light and aero enough, and are on an efficent machine like a road bike with high pressure tires, you can go considerably faster that what most of you are familar with. Comfort is an issue though.
Anyway, my project I am starting when the parts arrive is this. Bought 2 12v 17ah SLA batteries and a small 24v 350watt motor. With proper gearing this motor will perform better than what most people would expect.
(For example, if I put out 100% effort sprinting in a huge gear on my road bike, I might only produce 1000watts. But if I am in the correct gear, that same effort will get me 1700-1900w. With this in mind, you can see how important gearing and possible multiple gears are.)
I plan on doing a straight up circuit with an on/off switch, no controller. Since the motor is only 350watts, I really hope this is not a problem, concerning the electrics? (I have no problem with ride/speed wise with this type of on/off function.) I would think that a controller would end up soaking up power and decreasing efficiency.
My total cost should only be $150, (excluding the bike which I already have.) I going for pure simplicity and low cost on this setup. I will still pedal the bike on hills and starts, but I wanted the electric motor to take the bulk of the work on my relatively flat commute to work. I can't wait to get started on it!
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