|
|
|
Thread Tools | Display Modes |
#1
|
|||
|
|||
"Continuously variable" electric transmission
My searches have not turned up anyone selling a bicycle with a
continuously variable electric transmission. I don't mean an electric scooter: I mean one in which the crank turns a generator/alternator, whose output through an electronic controller then drives an electric motor on the wheel rim(s) or in the hub(s). There would be no chain, derailleur or gears, except perhaps for some fixed-ratio gearing inside the generator/alternator or motor assemblies. A control equivalent to a shift lever sets the ratio between crank torque and RPMs, which can be varied over some wide range. The rider sets the speed by changing this ratio and/or the crank RPMs as they find comfortable. Scooter-type assist would be possible through use of an optional battery. (Earlier threads on the subject addressed mechanical CVTs and auto-shift mechanisms, not an all-electric transmission.) What's the point? Mostly geekiness, I suppose, but the effectively infinite number of "gears" while reducing the number of moving parts is appealing. Also appealing is the notion that a battery in the system would provide load-levelling (hill assist) but with the rider still ultimately providing all of the energy, unless of course the rider cheats by re-charging the battery from an external source. For non-cheaters :_ the battery need only be large enough to help climb one hill. Efficiency would not be as good as with a conventional drive, but that's not really a concern for commuters or pleasure riders. Surely by now someone must make such a thing? |
Ads |
#2
|
|||
|
|||
"Continuously variable" electric transmission
On Sun, 07 Dec 2003 21:43:10 +0000, Richard Schumacher wrote:
My searches have not turned up anyone selling a bicycle with a continuously variable electric transmission. I don't mean an electric scooter: I mean one in which the crank turns a generator/alternator, whose output through an electronic controller then drives an electric motor on the wheel rim(s) or in the hub(s). snippage *Efficiency would not be as good as with a conventional drive, but that's not really a concern for commuters or pleasure riders. Efficiency would indeed be a concern for commuters and pleasure riders if the efficiency is low enough, as I would presume would be the case. You have three separate sources of energy loss: the inefficiency of the generator, the power transmission to the motors, and the motors themselves. Do you ever notice an electric motor getting hot? That's wasted energy, and that gets worse as load increases. The engineers can give reasonable estimates on the energy losses. -- David L. Johnson __o | Deserves death! I daresay he does. Many that live deserve _`\(,_ | death. And some that die deserve life. Can you give it to (_)/ (_) | them? Then do not be too eager to deal out death in judgement. -- J. R. R. Tolkien |
#3
|
|||
|
|||
"Continuously variable" electric transmission
|
#4
|
|||
|
|||
"Continuously variable" electric transmission
|
#5
|
|||
|
|||
"Continuously variable" electric transmission
I doubt it. The loss in efficiency over a mechanical
transmission would make most any ride a real chore. A good point. Bicycles lose only a fraction of 1% in friction losses. The above proposed bike would probably be lucky to lose say 30%. Think of it this way, you are pedalling 3 gears higher then you are going. Another point is that all that stuff would weigh something. I think the proposed bike would weight considerably more then the 18 or so lbs for a good mechanical bike. A final point is all that added stuff is fairly complex and I think it would have a certain failure rate. The mechanical bikes are pretty reliable - except for flats, one sees very very few mechanical failures on bikes. |
#6
|
|||
|
|||
"Continuously variable" electric transmission
Richard Schumacher wrote
My searches have not turned up anyone selling a bicycle with a continuously variable electric transmission. I don't mean an electric scooter: I mean one in which the crank turns a generator/alternator, whose output through an electronic controller then drives an electric motor on the wheel rim(s) or in the hub(s).sure riders. ... Surely by now someone must make such a thing? I don't think you'll find anything in production but there's an article about such a thing he http://petrix.dreifels.ch/fb/images/1_wsj_shorter_1.pdf Regards, Mike |
#7
|
|||
|
|||
"Continuously variable" electric transmission
|
#8
|
|||
|
|||
"Continuously variable" electric transmission
Richard Schumacher wrote in message ...
My searches have not turned up anyone selling a bicycle with a continuously variable electric transmission. SNIP Surely by now someone must make such a thing? Search through the IHPVA archives at www.ihpva.org . I believe Andreas Fuchs was designed such a device and has built working models. Jeff |
#9
|
|||
|
|||
"Continuously variable" electric transmission
I've been thinking the same thing. But, I know of no one who makes such a
thing. Yes, I've looked. |
#10
|
|||
|
|||
"Continuously variable" electric transmission
"Richard Schumacher" wrote in message ... My searches have not turned up anyone selling a bicycle with a continuously variable electric transmission. I don't mean an electric scooter: I mean one in which the crank turns a generator/alternator, whose output through an electronic controller then drives an electric motor on the wheel rim(s) or in the hub(s). There would be no chain, derailleur or gears, except perhaps for some fixed-ratio gearing inside the generator/alternator or motor assemblies. A control equivalent to a shift lever sets the ratio between crank torque and RPMs, which can be varied over some wide range. The rider sets the speed by changing this ratio and/or the crank RPMs as they find comfortable. Scooter-type assist would be possible through use of an optional battery. (Earlier threads on the subject addressed mechanical CVTs and auto-shift mechanisms, not an all-electric transmission.) What's the point? Mostly geekiness, I suppose, but the effectively infinite number of "gears" while reducing the number of moving parts is appealing. Also appealing is the notion that a battery in the system would provide load-levelling (hill assist) but with the rider still ultimately providing all of the energy, unless of course the rider cheats by re-charging the battery from an external source. For non-cheaters :_ the battery need only be large enough to help climb one hill. Efficiency would not be as good as with a conventional drive, but that's not really a concern for commuters or pleasure riders. Surely by now someone must make such a thing? Unlike a gas fueled internal combustion motor, an electric motor's peak torque is 0 rpm, so no transmission is needed. A single gearing is used for whatever your primary speed will be. |
|
Thread Tools | |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Thread Starter | Forum | Replies | Last Post |
Should I get an electric bike? Help! | The Real Lee Casey | General | 9 | August 30th 03 09:48 AM |
Ego-2 electric bike faster than car in city commuting race | Electric Bike & Scooter Guide | General | 0 | August 9th 03 01:44 AM |