Light, fastest, climbs mountains, and pretty efficient
- Thread starter prState
- Start date
I read this late last night which was a bad idea as I've been dreaming about bike possibilities half the night!
If the objective is to get a bike that does both 'fast on the flat' and 'steep hill climbs', I rather like prState's initial suggestion. The most obvious enhancement to me would be to do it all from the same motor to avoid additional weight from two motors, only one of which is in use at any one time.
I feel the way to get to the solution is to question the basic design assumptions in bikes and see which ones are done for convention or to meet technical constraints that no longer apply.
My best guess is that it could be something to do with the size of the wheels. There's no overwhelming reason why they have to be so big. They don't have to be the same size either. Wheel size is a means to achieve gearing so if you had a larger wheel and smaller wheel with the same powertrain combination capable of being switched between the two you would get two different capabilities from the same motor.
That got me thinking about having two chains - one driving each wheel - with a derailleur switching between them, but I'm sceptical that you could drive the front (steered) wheel via a chain. Woud another direct drive system work on a steered wheel? Possible, but I can't see it!
I'll keep thinking about this!
Frank
If the objective is to get a bike that does both 'fast on the flat' and 'steep hill climbs', I rather like prState's initial suggestion. The most obvious enhancement to me would be to do it all from the same motor to avoid additional weight from two motors, only one of which is in use at any one time.
I feel the way to get to the solution is to question the basic design assumptions in bikes and see which ones are done for convention or to meet technical constraints that no longer apply.
My best guess is that it could be something to do with the size of the wheels. There's no overwhelming reason why they have to be so big. They don't have to be the same size either. Wheel size is a means to achieve gearing so if you had a larger wheel and smaller wheel with the same powertrain combination capable of being switched between the two you would get two different capabilities from the same motor.
That got me thinking about having two chains - one driving each wheel - with a derailleur switching between them, but I'm sceptical that you could drive the front (steered) wheel via a chain. Woud another direct drive system work on a steered wheel? Possible, but I can't see it!
I'll keep thinking about this!
Frank
There are already a number of bikes which drive the front wheel by chain Frank, particularly recumbents and semi-recumbents. Some use seemingly crude methods of twisting the chain, some use crown gear transfer and there have been some other clever methods. As you say, two different size wheels can be used and have often been used on trade bicycles in the past, also on the current German post bike I seem to remember.
Bicycles have probably been subject to more ingenuity than any other form of transport over the years, and it's unlikely that there will be anything new and advantageous found in transmission. Current "new" ideas like the NuVinci/Swizzbee etc are in my opinion over complex and/or doomed to early unreliability, and all too often have been tried before anyway. Most things dreamed up have already been done in the past, and the past holds many good ideas which could now be utilised. One of those has particular reference to our e-bikes, but that's yet another I'm smiling about and waiting for someone to realise.
That's not part of my challenge though. I'm speaking of something which already exists, and it's that fact that has led to it not being spotted, everyone too busy looking for new ideas.
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Bicycles have probably been subject to more ingenuity than any other form of transport over the years, and it's unlikely that there will be anything new and advantageous found in transmission. Current "new" ideas like the NuVinci/Swizzbee etc are in my opinion over complex and/or doomed to early unreliability, and all too often have been tried before anyway. Most things dreamed up have already been done in the past, and the past holds many good ideas which could now be utilised. One of those has particular reference to our e-bikes, but that's yet another I'm smiling about and waiting for someone to realise.
That's not part of my challenge though. I'm speaking of something which already exists, and it's that fact that has led to it not being spotted, everyone too busy looking for new ideas.
.
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No, not automatic transmission prState. In general, completely automatic transmission systems are often less efficient. What I'm speaking of is efficient, and what's more, it's already in use, though one could say, misuse.
Now there's a conundrum!
When I reveal what it is, you'll see a simple, reliable, low cost and highly efficient way of doing what others are trying to do in less efficient, horribly complex and expensive ways. That's what makes me smile, the fact that such huge and wasted effort is expended in doing something that's right under everyone's noses already.
I should add, in saying it already exists, I mean it exists in many of our bikes already.
.
Now there's a conundrum!
When I reveal what it is, you'll see a simple, reliable, low cost and highly efficient way of doing what others are trying to do in less efficient, horribly complex and expensive ways. That's what makes me smile, the fact that such huge and wasted effort is expended in doing something that's right under everyone's noses already.
I should add, in saying it already exists, I mean it exists in many of our bikes already.
.
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I hope someone guesses it, or I'll be getting down to sails and rockets soon.
I'll take another stab though, the 2 or 3 chainrings that are already on the crank, turning bikes from 5/6 speed, to 10/12, to 15, 18 etc.,
Except, in this case the chainrings on the front are good enough to do the job for electrics. Is that it?
I'll take another stab though, the 2 or 3 chainrings that are already on the crank, turning bikes from 5/6 speed, to 10/12, to 15, 18 etc.,
Except, in this case the chainrings on the front are good enough to do the job for electrics. Is that it?
I'm afraid not prState. Chainwheels not involved.
As Stuart knows, it's rarely possible to guess these conundrums I set up, and this one is probably the most difficult of all, simply because it's a Eureka thing rather than something to be worked out methodically.
If no-one guesses I'll be revealing it later next week, so if anyone wants to get a manufacturer rolling on it and steal a march on the competition, they'll be free to do so.
.
As Stuart knows, it's rarely possible to guess these conundrums I set up, and this one is probably the most difficult of all, simply because it's a Eureka thing rather than something to be worked out methodically.
If no-one guesses I'll be revealing it later next week, so if anyone wants to get a manufacturer rolling on it and steal a march on the competition, they'll be free to do so.
.
A guess, but is it to do with some kind of derailleur (or does that count as a "chainwheel"? per above, I'm unsure...), say on the left side of rear wheel opposite to the chainset derailleur for gearing an external motor like a currie? I don't know if that's been done either, though I think currie motors are usually a fixed gear rear chain drive, although the gear ratio can be changed.
I was trying to follow your hints:
Am I even close?
Stuart.
I was trying to follow your hints
: Since many, indeed most bikes (except for hub or single geared) have derailleur gears, they're simpler & more efficient than hub gears as you've said before, and in a way derailleur gears are both "used", for pedalled transmission, and "misused" by not being used with an external motor (though it may have been and I'm unaware of it)?! If its possible to have a "separate" derailleur for the motor, I guess the transmission could be set up for motor & pedal gear changes to be synchronized...?flecc said:...the simple answer, which almost exists but for the failure to see that it does.
...as I've said, it already almost exists.
What I'm speaking of is efficient, and what's more, it's already in use, though one could say, misuse.
...a simple, reliable, low cost and highly efficient way...
...huge and wasted effort is expended in doing something that's right under everyone's noses already.
...in saying it already exists, I mean it exists in many of our bikes already.
Am I even close?
Stuart.
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Afraid not Stuart, sorry.
This is really one of those "kick yourself" things, though that's only true for someone who knows a little about bike transmission. My advice is that you don't treat that as a clue, since it will lead you astray.
This is why I've avoided clues this time, since they would be misleading, and in any case, I wanted to see if anyone actually twigged it rather than trying to gradually work it out. I don't think it's something that would be worked out, it's either seen or it's not. But large numbers of people in this forum have seen it, but without seeing it, if you get my meaning.
.
This is really one of those "kick yourself" things, though that's only true for someone who knows a little about bike transmission. My advice is that you don't treat that as a clue, since it will lead you astray.
This is why I've avoided clues this time, since they would be misleading, and in any case, I wanted to see if anyone actually twigged it rather than trying to gradually work it out. I don't think it's something that would be worked out, it's either seen or it's not. But large numbers of people in this forum have seen it, but without seeing it, if you get my meaning.
.
Hahaha! Yes I see what you mean flecc - NOT!!
No, I do, sort of - It occurred to me that my guess was too "worked out" rather than "twigged" or a "eureka" moment and so probably on the wrong lines... I should have asked "am I even in the right ballpark/on the same planet?".
Its possibly more fascinating to me the process by which these ideas occur to some (few, or even one) yet others cannot see it when its in front of them, as you say! It is true that many times a seemingly intuitive leap can be made from an approach which synthesises new ideas from previously unrelated concepts, when no amount of "mechanical" thought or analysis could possibly achieve it...
Even more amazing is that, the answer appears so simple, you often can't believe how you never saw it! Kick yourself indeed! Then after that you take it for granted, as it seems so simple...
Yet its virtually impossible to know, until you're informed of it... strange!
Stuart.
No, I do, sort of - It occurred to me that my guess was too "worked out" rather than "twigged" or a "eureka" moment and so probably on the wrong lines... I should have asked "am I even in the right ballpark/on the same planet?"
.Its possibly more fascinating to me the process by which these ideas occur to some (few, or even one
) yet others cannot see it when its in front of them, as you say! It is true that many times a seemingly intuitive leap can be made from an approach which synthesises new ideas from previously unrelated concepts, when no amount of "mechanical" thought or analysis could possibly achieve it...Even more amazing is that, the answer appears so simple, you often can't believe how you never saw it! Kick yourself indeed! Then after that you take it for granted, as it seems so simple...
Yet its virtually impossible to know, until you're informed of it... strange!
Stuart.
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In fact that would be the ideal prState, and I believe that might be the ultimate pedelec system. Matching the constant rotation of an electric motor to the pulsed power of a human is fundamentally flawed.Bionic legs!
Your suggestion has some relevance to this conundrum, and in due course you'll see why when I reveal the answer. Once again though, not a clue as it could be very misleading.
.
The plot thickens... .
Ok then, going out on a limb ('scuse the pun on bionic legs - nice one btw prState!)... digital motors!
.Ok then, going out on a limb ('scuse the pun on bionic legs - nice one btw prState!
)... digital motors! One idea that has often occurred to me is 2 or 3 speeds incorporated into the hub motor gearing, it wouldn't be too difficult to design such a system based on the same principals as a 3 speed hub which after all is not dissimilar from the planetary gears used in hub motors. Such a system could be linked so that the lower ratio could be selected when the normal gears were at their lowest. It would need to be incorporated at the design stage of the motor though so not a DIY job. (Unless you have an engineering factory in your kitchen )
)As an afterthought: on our bikes, literally under our noses and already in use is the crank, which for those of us with a regular cadence & using gears has a fairly narrow range of spin speeds: a crank "motor" does almost already exist - our legs & pedals, innit?!
Could a "crank motor" be fitted, with spinspeeds within the same narrow range as our (individual) pedalling cadences - possibly individually adjustable, so that little or no gears are required for the motor - giving a highly efficient & simple solution, plus excellent low & central weight distribution...
Again, I'm no mechanic, but you already said this is feasible flecc, and its simpler now with little or no motor gears needed...
After that its either bionic legs or a digital (non-analogue) motor...
Stuart.
Could a "crank motor" be fitted, with spinspeeds within the same narrow range as our (individual) pedalling cadences - possibly individually adjustable, so that little or no gears are required for the motor - giving a highly efficient & simple solution, plus excellent low & central weight distribution...
Again, I'm no mechanic, but you already said this is feasible flecc, and its simpler now with little or no motor gears needed...
After that its either bionic legs or a digital (non-analogue) motor
...Stuart.
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OK Ian. you're close enough, though you haven't actually said it exists already.
The missed opportunity I've referred to is that of the designers of direct drive hubs, who having made that choice, dismissed the idea of keeping the orbital gears. That essential of the best designers, the child-like inquiring mind that says "What if?" was missing, as was the close knowledge of cycle systems which would make them see they were looking at a three speed hub as well as an orbital drive.
You've said similar, but in fact the existing orbital gears in a hub motor aren't just similar, they are a three speed hub (except for the anchored annulus), merely not used. Of course they can't be used for two different purposes, but if the motor design is treated as a direct drive, the existing orbital set is freed for gears use.
Linked with this is how I've shown elsewhere that an e-bike motor only needs two gears, with peak torque centred on 6 mph and 10 mph for a Euro legal model and perhaps 7 mph and 13 mph for a 20+ mph model. Either would give a flat enough torque availability to handle all cycle circumstances efficiently.
This means that the annulus (ring gear in the hub shell) can stay in place with just the sun and planet cage pinions used for one gear and direct drive the other. Since the one weakness of direct drive motors is low speed power, the reduction gear should be the first gear allowing an early spin up to speed, with direct drive in use most of the time in normal riding for the higher speeds from around 9 mph, leading to very high reliability. Gearing in this way enables the direct drive motor designer to more accurately focus the power, rather than trying to spread it over the whole range, thus still further increasing power and efficiency. This simple and reliable system would be superior in every way to existing motor gearing systems
I've expressed elsewhere the undesirability of a motor driving though the same gears as the rider in the fashion the Twist uses, the requirements of both being totally different. Here's a summary of some of the reasons:
1) Riders need a number of gears, and as shown, motors don't.
2) Rider power is pulsed, motor power is continuous, the two not matching. every Twist rider knows the rhythmic pulsing sound of the motor as they pedal, and that's no way for an electric motor to run, being inefficient. Panasonic only get away with it due to the low power of their motor.
3) Using the same gear system means that all drive is lost when changing gear, which is irrational. If the motor is free to continue to drive while the rider changes gear, kinetic energy isn't lost by slowing, especially important on steep hills with a slow acting hub change where forward momentum is quickly lost.
4) The world of cycling is aware of just how bad riders are with gear selection, most riders operating at quite low efficiencies. Those riders usually won't know their motor's optimum gear requirement either at any one time. The chance of them choosing the optimum compromise gear for both themselves and their motor in any circumstance is zero.
5) Cycle gear systems aren't made to withstand combined rider and motor power, but rider power only, so reliability can often be affected.
That's just some of the reasons only, but more than enough to show the undesirability.
The system I propose removes half that problem. As Ian has said, shifting between the two motor gears is readily coupled into the cycle change as ranges, and the system could even be supplied as a kit since there aren't many different changers needed. SRAM and Shimano are compatible, and Sunrace Sturmey are the only other one worth bothering with in e-bikes. Since the number of gears only means a detent change in the control, about four or five exchange control options are all that's needed.
Alternatively, the range change could be made automatically based on spin speed, either mechanically or electrically, and I think I favour one of these for operational simplicity, transparent to the rider.
I think bikes with this motor would just take over the market, since they could use less power giving more range for any given performance, while still being capable of anything met in terms of hill climbing.
Nor is it restricted to hubs. A centre mounted motor could have the drive exiting via a small sprocket and driving a left hand chain onto the rear hub at the left, a system that has been successfully used in other contexts, thus not interfering with the rider gear drive. With either front or rear hub or centre motor, control could be either throttle or pedelec.
All we want now are manufacturers to produce this low cost high performance system to make our bikes much better.
.
The missed opportunity I've referred to is that of the designers of direct drive hubs, who having made that choice, dismissed the idea of keeping the orbital gears. That essential of the best designers, the child-like inquiring mind that says "What if?" was missing, as was the close knowledge of cycle systems which would make them see they were looking at a three speed hub as well as an orbital drive.
You've said similar, but in fact the existing orbital gears in a hub motor aren't just similar, they are a three speed hub (except for the anchored annulus), merely not used. Of course they can't be used for two different purposes, but if the motor design is treated as a direct drive, the existing orbital set is freed for gears use.
Linked with this is how I've shown elsewhere that an e-bike motor only needs two gears, with peak torque centred on 6 mph and 10 mph for a Euro legal model and perhaps 7 mph and 13 mph for a 20+ mph model. Either would give a flat enough torque availability to handle all cycle circumstances efficiently.
This means that the annulus (ring gear in the hub shell) can stay in place with just the sun and planet cage pinions used for one gear and direct drive the other. Since the one weakness of direct drive motors is low speed power, the reduction gear should be the first gear allowing an early spin up to speed, with direct drive in use most of the time in normal riding for the higher speeds from around 9 mph, leading to very high reliability. Gearing in this way enables the direct drive motor designer to more accurately focus the power, rather than trying to spread it over the whole range, thus still further increasing power and efficiency. This simple and reliable system would be superior in every way to existing motor gearing systems
I've expressed elsewhere the undesirability of a motor driving though the same gears as the rider in the fashion the Twist uses, the requirements of both being totally different. Here's a summary of some of the reasons:
1) Riders need a number of gears, and as shown, motors don't.
2) Rider power is pulsed, motor power is continuous, the two not matching. every Twist rider knows the rhythmic pulsing sound of the motor as they pedal, and that's no way for an electric motor to run, being inefficient. Panasonic only get away with it due to the low power of their motor.
3) Using the same gear system means that all drive is lost when changing gear, which is irrational. If the motor is free to continue to drive while the rider changes gear, kinetic energy isn't lost by slowing, especially important on steep hills with a slow acting hub change where forward momentum is quickly lost.
4) The world of cycling is aware of just how bad riders are with gear selection, most riders operating at quite low efficiencies. Those riders usually won't know their motor's optimum gear requirement either at any one time. The chance of them choosing the optimum compromise gear for both themselves and their motor in any circumstance is zero.
5) Cycle gear systems aren't made to withstand combined rider and motor power, but rider power only, so reliability can often be affected.
That's just some of the reasons only, but more than enough to show the undesirability.
The system I propose removes half that problem. As Ian has said, shifting between the two motor gears is readily coupled into the cycle change as ranges, and the system could even be supplied as a kit since there aren't many different changers needed. SRAM and Shimano are compatible, and Sunrace Sturmey are the only other one worth bothering with in e-bikes. Since the number of gears only means a detent change in the control, about four or five exchange control options are all that's needed.
Alternatively, the range change could be made automatically based on spin speed, either mechanically or electrically, and I think I favour one of these for operational simplicity, transparent to the rider.
I think bikes with this motor would just take over the market, since they could use less power giving more range for any given performance, while still being capable of anything met in terms of hill climbing.
Nor is it restricted to hubs. A centre mounted motor could have the drive exiting via a small sprocket and driving a left hand chain onto the rear hub at the left, a system that has been successfully used in other contexts, thus not interfering with the rider gear drive. With either front or rear hub or centre motor, control could be either throttle or pedelec.
All we want now are manufacturers to produce this low cost high performance system to make our bikes much better.
.
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Just seen your last post Stuart, but as you see above, Ian has got close enough. prState and Peter in his comment on his post got close, but didn't identify what I was looking at and how it could be used, and also were referring to rider gearing, not the motor.
Given that derailleur gears can be very close to 100% efficient, there's no future in looking for improvements there, and especially not in going backwards as in the NuVinci.
It's the motor gearing where separation from the rider and improvement is needed.
.
Given that derailleur gears can be very close to 100% efficient, there's no future in looking for improvements there, and especially not in going backwards as in the NuVinci.
It's the motor gearing where separation from the rider and improvement is needed.
.
Apologies if my lucky guess got you to reveal your idea prematurely Flecc, but it was your clue about needing some knowledge of bicycle transmissions that gave it away. Admittedly I was thinking of the arrangement used as part of an existing geared hub motor but your idea of using the epicyclic gears to gear what would otherwise be a direct drive motor makes more sense. An extension to the idea could be to link a freewheel lockout to one of the brake levers to enable regenerative braking whilst retaining the free coasting from the freewheel.
There is another idea, not entirely my own as I think it has already been done, of using an electrical way to achieve a similar result. A switching arrangement is provided that can connect adjacent armature poles in parallel, effectively halving the number of poles, doubling the rpm and halving the Torque giving a similar effect to a 1:2 mechanical ratio. I'm fairly sure I've seen a 2 speed hub motor advertised somewhere. The principal of pole switching has been used to produce 2 speed (1500/3000 rpm) induction motors and I believe also synchronous motors which are a close cousin of brushless DC motors.
There is another idea, not entirely my own as I think it has already been done, of using an electrical way to achieve a similar result. A switching arrangement is provided that can connect adjacent armature poles in parallel, effectively halving the number of poles, doubling the rpm and halving the Torque giving a similar effect to a 1:2 mechanical ratio. I'm fairly sure I've seen a 2 speed hub motor advertised somewhere. The principal of pole switching has been used to produce 2 speed (1500/3000 rpm) induction motors and I believe also synchronous motors which are a close cousin of brushless DC motors.
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I thought that might have given it away Ian! No apologies needed though, since you'd clearly considered it already so had seen the possibility. I'm not a fan of regeneration on bikes since I don't think the available mass makes it worthwhile.
You have seen two speed motors I'm sure, advertised on Team Hybrid's site, they're Crystalite I think. That's another thing I wouldn't consider though, since one mode will always be wasteful and consume inordinate amounts of power. In fact Mark Higgons of Team Hybrid warns of just that, advising restricted use of the low speed/high torque mode due to it's consumption.
I don't think anything could beat a two speed gear modern motor for efficiency in an e-bike. Just a pity there isn't one on the market!
.
You have seen two speed motors I'm sure, advertised on Team Hybrid's site, they're Crystalite I think. That's another thing I wouldn't consider though, since one mode will always be wasteful and consume inordinate amounts of power. In fact Mark Higgons of Team Hybrid warns of just that, advising restricted use of the low speed/high torque mode due to it's consumption.
I don't think anything could beat a two speed gear modern motor for efficiency in an e-bike. Just a pity there isn't one on the market!
.
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