Jeremy Harris
100 MW
I've stuck a 405 hub on the front of my recumbent (which works well), but have now come to realise that my "pedal power" input is very much more variable than I thought it would be. Because a 'bent tends to freewheel down even slight hills pretty fast, there are plenty of occasions where I'm not pedalling at all.
I've thought about regeneration, but this isn't really the best answer (IMHO) if, like me, you want to try and keep fit. Ideally I would like a bike that allowed me to always pedal at a comfortable rate and power, up hill and down dale, with the electric system making up for the peaks and troughs in demand.
I'd also quite like some weather protection (I live in England......) so my thoughts are turning to a very light, composite monocoque, velomobile trike. I don't want masses of speed, just enough to keep up with urban traffic, perhaps 20mph to 25mph average speed.
So, this has led to the idea of just connecting the pedals to a generator, perhaps another brushless hub motor connected as a three phase PM alternator, suitably geared up. If I pick the right motor, I should be able to get enough out of it to charge the batteries at maybe 50W - 60W average (about 80W input power from the pedals). The advantage of doing this is that the structure is simpler, as the generator can be inside a central spine, just behind the cranks, with a simple direct chain drive.
I reckon that a decent high power rear hub motor, plus a 48V, or perhaps 60V, battery pack would give the performance I need, provided that I can keep the weight down. I've experimented with a light weight composite aircraft fuselage, using strip plank balsa and epoxy glass (a boat building technique, see here: http://www.storerboatplans.com/Balsacanoe/Balsacanoe.html) and this looks like a good way to get a strong, yet light, structure. I'd plan on using a hollow composite spine and cross member to provide the necessary structural stiffness for the "pilot", wheel and crank forces. The fact that a long chain, gears etc are not needed should compensate in part for the weight of the generator.
Even though such a hybrid system is obviously of poor direct efficiency, the fact that it would allow continuous power input by the rider to top up the battery, even when careering downhill at full speed, or whilst sitting still in traffic, would make up for some of the losses. Being able to put perhaps 20% or so of the power used back into the battery all the time might make this concept as efficient as a conventional pedal direct drive/electric assist system over a long run on hilly terrain.
I'm guessing that someone has already tried this, as it's not exactly a new idea, but also suspect that many people have discarded the idea because the direct efficiency is low.
The final advantage, here in England at least, is that I may well be able to keep this "sort of" outside the registration, road worthiness test, etc rules, as I'm hoping that I can argue that it's still an "electric assisted pedal cycle" (although I'd have to perhaps keep the speed down!).
Any thoughts?
Jeremy
I've thought about regeneration, but this isn't really the best answer (IMHO) if, like me, you want to try and keep fit. Ideally I would like a bike that allowed me to always pedal at a comfortable rate and power, up hill and down dale, with the electric system making up for the peaks and troughs in demand.
I'd also quite like some weather protection (I live in England......) so my thoughts are turning to a very light, composite monocoque, velomobile trike. I don't want masses of speed, just enough to keep up with urban traffic, perhaps 20mph to 25mph average speed.
So, this has led to the idea of just connecting the pedals to a generator, perhaps another brushless hub motor connected as a three phase PM alternator, suitably geared up. If I pick the right motor, I should be able to get enough out of it to charge the batteries at maybe 50W - 60W average (about 80W input power from the pedals). The advantage of doing this is that the structure is simpler, as the generator can be inside a central spine, just behind the cranks, with a simple direct chain drive.
I reckon that a decent high power rear hub motor, plus a 48V, or perhaps 60V, battery pack would give the performance I need, provided that I can keep the weight down. I've experimented with a light weight composite aircraft fuselage, using strip plank balsa and epoxy glass (a boat building technique, see here: http://www.storerboatplans.com/Balsacanoe/Balsacanoe.html) and this looks like a good way to get a strong, yet light, structure. I'd plan on using a hollow composite spine and cross member to provide the necessary structural stiffness for the "pilot", wheel and crank forces. The fact that a long chain, gears etc are not needed should compensate in part for the weight of the generator.
Even though such a hybrid system is obviously of poor direct efficiency, the fact that it would allow continuous power input by the rider to top up the battery, even when careering downhill at full speed, or whilst sitting still in traffic, would make up for some of the losses. Being able to put perhaps 20% or so of the power used back into the battery all the time might make this concept as efficient as a conventional pedal direct drive/electric assist system over a long run on hilly terrain.
I'm guessing that someone has already tried this, as it's not exactly a new idea, but also suspect that many people have discarded the idea because the direct efficiency is low.
The final advantage, here in England at least, is that I may well be able to keep this "sort of" outside the registration, road worthiness test, etc rules, as I'm hoping that I can argue that it's still an "electric assisted pedal cycle" (although I'd have to perhaps keep the speed down!).
Any thoughts?
Jeremy