megacycle
100 kW
Is it possible to mod a 250W BB drive to act as a pedal generator, so a derailer can select a chain ring to drive the rear wheel or turn the motor now generator?
BB drive to pedal generator
- Thread starter megacycle
- Start date
Er....so you wanna use the BB drive motor to turn a generator at the rear wheel? Why, exactly? (cuz you're losing potentially a lot of the energy that way...would be simpler to hook up a resistor across your battery and discharge it some without doing anything at all 
Or...are you asking if there is a way to use the BB drive motor itself as a generator?
If the latter, then I don't know of a way to do it unless you re-engineer the whole thing for that purpose, cuz the whole idea of most BB drives is to keep the pedals from driving the motor, and the motor from driving the pedals, via freewheels.
If you remove all the freewheels, then the pedals would be able to drive the motor (and the rear wheel) but not via the gears that the derailer selects. For that you'd ahve to again reengineer that section to make it possible.
Or...are you asking if there is a way to use the BB drive motor itself as a generator?
If the latter, then I don't know of a way to do it unless you re-engineer the whole thing for that purpose, cuz the whole idea of most BB drives is to keep the pedals from driving the motor, and the motor from driving the pedals, via freewheels.
If you remove all the freewheels, then the pedals would be able to drive the motor (and the rear wheel) but not via the gears that the derailer selects. For that you'd ahve to again reengineer that section to make it possible.
megacycle
100 kW
Yes mate, re-engineer as there doesn't appear to be anything electrically large enough, off shelf.amberwolf said:
Yes I wasn't sure about that because I've never seen a BB drive arrangement, such as eg a Bafang.amberwolf said:
I was hoping to derail from a the normal arrangement of the rear freewheeling ring, driven by a mid chain ring to it freewheeling as well on a mid ring as usual but the BB brushless is then geared onto the crank and connected through a 3 phase voltage tripler circuitry to charge battery as a series hybrid, so keeping the chain sprocket count low, so it basically is can be pedal assisted uphill and variably charged on the flat or DH.
skeetab5780
1 MW
There was a electric motorcycle that came out a few years ago with similar technology. I remember watching the YT video, the pedals regenerated the pack while he was cruising at 40mph with cars. The pedals did not actually drive the rear wheel at all.
megacycle
100 kW
Thanks guys for the feed back.
I know of the pure series hybrid approach.
I'm attempting to create a parallel hybrid, so a chain drive to the rear can be used to good effect and efficiency when going up hill and then yes as you mention skeetab, the bike can still be generating power by pedaling the generator while the bike is hub motoring or freewheeling along fast, topping up at at a 70-80W like an exercise bike, but maybe a schlump might do same
I know of the pure series hybrid approach.
I'm attempting to create a parallel hybrid, so a chain drive to the rear can be used to good effect and efficiency when going up hill and then yes as you mention skeetab, the bike can still be generating power by pedaling the generator while the bike is hub motoring or freewheeling along fast, topping up at at a 70-80W like an exercise bike, but maybe a schlump might do same
icerider
100 W
Are you just trying to get regen on a BB drive ?
megacycle
100 kW
Basically but not under braking or trying to pedal it backwardsicerider said:
into the controllerI was thinking of pedaling the BB drive and the output goes to a 3 phase voltage trippling or more circuit steps up from around the inverter drive voltage to 90V+ and rectified/ smoothed to battery, hopefully without too much loss, thinking around 75%.
icerider
100 W
Basically but not under braking or trying to pedal it backwards
The most efficient approach is to use pedal input directly for vehicle motion and correspondingly decrease the draw on the battery. That way you avoid all the inefficiencies of converting mechanical to electrical and back. Pedal HARD uphill to carry as much of the load as you can, continue to pedal on the flat and reduce throttle, etc. Doing that will dramatically extend your range.
with a DD motor you could have all of what you are asking for pretty simply but the overall efficiency is pretty low because of all the inefficiencies of converting mechanical to electrical and back.
megacycle
100 kW
Yes that's what essentially I'd have with chain drive for hills with the advantage of efficiency but instead of a large mid ring, like a 80T or an expensive high speed schlump when I want to keep inputting pedalling at say 45kph+ have the BB generating some power.icerider said:
It will be a large raptor frame bike with a 5404 hub DD, so keeping up with pedaling at speeds of 50kph+
mfj197
10 W
+1 on this. Couldn't have put it better.icerider said:Basically but not under braking or trying to pedal it backwards
The most efficient approach is to use pedal input directly for vehicle motion and correspondingly decrease the draw on the battery. That way you avoid all the inefficiencies of converting mechanical to electrical and back. Pedal HARD uphill to carry as much of the load as you can, continue to pedal on the flat and reduce throttle, etc. Doing that will dramatically extend your range.
megacycle
100 kW
Maybe I'm not putting myself across properly.mfj197 said:
I want to be able to produce power when motoring fast on flat or DH when normally can't pedal fast enough to add to the bikes power output, it's either this or several hundred dollars for a schlump speed drive or a large looking 80T chain ring.
In that case, what I would do is simply replace the left side crank with a right side crank/chainring, then run a chain from that to a dedicated generator. Use a manual clutch of some sort to engage the chain to the sprocket (like using an old friction shifter lever, and it's cable move a tensioner to pull the chain up against hte generator sprocket, but otherwise have a spring pull it away). Gear it so you can get a useful output voltage under load while pedalling at your comfortable speed and force.
You could even use a brushed motor and diode(s) from it directly to the battery pack, so that the battery cannot power the generator/motor, but the generator/motor can put power back to the battery when it outputs a high enough voltage.
If you don't want ot do a clutch, you could simply use a freewheel on the generator's input sprocket so that when pedalling forward it freewheels, but when pedalling backward it engages. Then neither left nor right chain will ever interfere with teh other, as far as taking force from your pedalling to do work.
You could even use a brushed motor and diode(s) from it directly to the battery pack, so that the battery cannot power the generator/motor, but the generator/motor can put power back to the battery when it outputs a high enough voltage.
If you don't want ot do a clutch, you could simply use a freewheel on the generator's input sprocket so that when pedalling forward it freewheels, but when pedalling backward it engages. Then neither left nor right chain will ever interfere with teh other, as far as taking force from your pedalling to do work.
megacycle
100 kW
Thanks Ambo, you've given me something to think about there.
Just thought that the generator could be permanently spun on the left side now, as you say, but the gen output only connected when used, flick of switch, switches in relay to connect output circuitry to battery and there's the generation from the pedals.
Think i'd prefer brushless as even when there's no output, there would be permanent wear on brushes in this mode.
Cheers
Just thought that the generator could be permanently spun on the left side now, as you say, but the gen output only connected when used, flick of switch, switches in relay to connect output circuitry to battery and there's the generation from the pedals.
Think i'd prefer brushless as even when there's no output, there would be permanent wear on brushes in this mode.
Cheers
mfj197
10 W
I see. However surely in this circumstance you are using kilowatts of power to just maintain your speed (to take it out of the gear range of the bike), in which case adding 70-80 watts back into the battery through your pedalling isn't going to increase range that much. It will only be useful in situations which take you above the gearing of the bike, and I would have thought the complexity, hassle and weight would outweigh the limited gains. Be interesting to see what you come up with though!megacycle said:
Michael
It has been said before on this forum that pedalling at 30mph+ creates more drag than you can compensate for by sustained pedalling. As such, the most efficient option, which happily also happens to be the easiest, is to not pedal and tuck your legs in.
I haven't see any calculations or measurements to verify this statement, but it seems plausible.
I haven't see any calculations or measurements to verify this statement, but it seems plausible.
megacycle
100 kW
Thanks guys for your input.
I thought that the 150Wh or so over a couple of hours of riding, created by generation is going to be about 5% of the recharge power about the same as regeneration, totalling 10% of recharge Wh, but if drag is going to counter it, might have to go back to drawing board, it was going to double up as exercising, for when I'm flying along the stretch of flat or DH too, give the old legs something to do.
Note- I think some Stealth's use Schlump BB drives
I thought that the 150Wh or so over a couple of hours of riding, created by generation is going to be about 5% of the recharge power about the same as regeneration, totalling 10% of recharge Wh, but if drag is going to counter it, might have to go back to drawing board, it was going to double up as exercising, for when I'm flying along the stretch of flat or DH too, give the old legs something to do.
Note- I think some Stealth's use Schlump BB drives
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