Two motors?

[Danny-K]

Anyway, back to the main thrust of the title of this thread. If I were to buy a 250 watt 36v/12a Alien front wheel kit and fit it to my Salisbury, and then on the toughest of hills, ran the two motors simultaneously whilst pedalling - would I be able to pedal up any hill in the UK - comfortably and with ease? I'm assuming that two motors would effectively half my weight that they would each be asked to endure.

 

[flecc]

Anyway, back to the main thrust of the title of this thread. If I were to buy a 250 watt 36v/12a Alien front wheel kit and fit it to my Salisbury, and then on the toughest of hills, ran the two motors simultaneously whilst pedalling - would I be able to pedal up any hill in the UK - comfortably and with ease? I'm assuming that two motors would effectively half my weight that they would each be asked to endure.

Perhaps not any hill, but certainly most. I think a better option would be a Tongxin Nano in the front wheel for four reasons. First is that you could choose the rpm version for optimum hill climbing power to pair nicely with the Salisbury motor. Second because of it's unique zero freewheeling resistance so it wouldn't detract from the Salisbury performance when not in use, third because of it's low weight and size, and fourth because it's a naturally good hill climber.
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[Blew it]

Why not!!

Hi Danny and all,

Yes Danny, you could fit the front motor Alien kit to the Salisbury, but, you might have to replace the front forks with a pair designed to accept a motor hub. these are currently available from Wheelcare.co.uk on Ebay at around £24. I'm almost certain they have the 110 m/m clearance needed on the drop-outs

Don't try running both motors off one battery, the combined demand would almost certainly result in enough voltage sag to trigger a low volt shut down. Anyway, the flat shaped Phylion 36 volt 10ah battery supplied with the Alien kit will easily fit on the Salisbury's rear rack.

The motor supplied with the Alien kit, is the same as fitted to the Synergie Mistral and also my Alien Lynx folder. In the latter case, with different internal gearing to suit the 20" wheels. On both of these machines the free-wheeling ability is very good. Obviously, there will be a little additional drag from the extra motor, but there simply has to be a net gain when both motors are pulling. If this extra drag became a problem on the flat, you could always give the "resting" motor a whiff of gas on the thumb throttle to even things up.

This how I think it would work.

On the flat, you could ride with normal pedelec controlled assist from the existing rear motor. When approaching a cliff face, you would then whack the thumb throttle supplied with the front motor wide open, and storm the hill with two motors pulling. Don't expect to go scortching up the hill like a half arsed astronaut, more likely the machine will slow to around 10 MPH which is the roadspeed at which these motors achieve maximum torque. The realm of fantasy maybe, but food for thought none the less.

I've just pulled a bit of a flanker on Bob at AlienOcean, I've just whacked in an order for one of the "flat" 36 volt 10 ah Phylion batteries and charger to use as an extender battery on my Synergie Mistral. The payments been accepted, so with a bit of luck it should arrive on the "dynamite" truck tomorrow(oops, today).

Dear me!. Us British just can't except that we have been rewarded with an un-written freedom to basically do as we wish, PROVIDING IT IN NO WAY IMPACTS ON ANOTHER PERSONS LIFE!. for goodness sake guys, have a bit of fun....everybody else is!!.

Best wishes to all

Bob

 

[flecc]

for goodness sake guys, have a bit of fun....everybody else is!!.

I wish they were! We used to have plenty of fun in this forum and were very lighthearted in our posting practice, but in recent months it's becoming ever more po faced.

The contrast between the forum of 2006-7 and 2008 is increasingly marked, and many of those who took part in that early easygoing period have long departed, which in itself speaks volumes.
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[Jeremy]

Don't be so sensitive, Flecc. We're not "po faced" at all in the main, it's just that some will read a textual response from someone who has chosen to take the position of forum "guru" literally, and respond accordingly. We don't have the benefit of vocal intonation or facial expression to give clues as to when a poster is being deliberately imprecise in the interest of brevity, or even when someone is being light-hearted.

In the particular case that applies to your position, then I would assume that it's rather akin to that of a university professor. Some on here will automatically question an apparently imprecise statement from someone who gives advice from an established position of authority, as that is what we have been taught and encouraged to do in order to learn and determine the underlying facts. If one of my colleagues failed to question the accuracy or underlying basis of statements then I would be exceedingly disappointed, as it would show a lack of curiosity and a too-ready willingness to accept an answer without the reassurance of seeing supporting data - not a good trait in a scientist.

To get back to the question about two motors, the plan to use the second motor as a manually activated one that is used only on hills seems perfectly legal, particularly if the first motor is pedelec controlled, the second motor is manually controlled and the assist speed is less than 15mph. If the second motor isn't used all the time, but just on hills, then its power contribution cannot reasonably be said to be "continuous" using any normal definition of the word. It's a particular case where compliance with the law seems quite straightforward to prove.

Jeremy

 

[Mussels]

I wish they were! We used to have plenty of fun in this forum and were very lighthearted in our posting practice, but in recent months it's becoming ever more po faced.

I blame the ageing membership myself, lets take away the over generous pensions so they can't afford these toys any more.

 

[Blew it]

Oh dear Mr Mussels, Baby-boomer envy perhaps!!

 

[Hooligooner]

Anyway, this chap has gone the twin motor route by having two currie 24V electrodrives at the back so he can overvolt to 48v and split the amps between the two motors to prevent overheating. Good for near 30mph, but I'm not sure I like the battery in the trailer.

Still should be fun though!

 

[Tiberius]

On the flat, you could ride with normal pedelec controlled assist from the existing rear motor. When approaching a cliff face, you would then whack the thumb throttle supplied with the front motor wide open, and storm the hill with two motors pulling. Don't expect to go scortching up the hill like a half arsed astronaut, more likely the machine will slow to around 10 MPH which is the roadspeed at which these motors achieve maximum torque. The realm of fantasy maybe, but food for thought none the less.

Hi Guys,

I've seen this idea of a maximum torque speed on the forum a couple of times, and its not quite correct. Maximum torque from an electric motor is at zero speed. Its not quite an inverse linear relationship with speed because in most cases the controller intervenes to limit the battery current.

What does vary with speed, and in different ways, is the efficiency and the power. The power (input or output) depends on the supply voltage as well as the motor, and for a given system there is a speed at which it peaks. On a well designed system that peak power will also deliver good efficiency. At lower speeds the efficiency can drop off sharply.

In summary then, there is a speed to aim for, or a speed to keep above. But it is all to do with efficiency and not about torque. As you go slower the torque will rise and you may be able to climb the hill.

In fact, when analysing hill climbing capability, the crucial question is not can you get up a particular hill, but at what speed can you get up the hill.

Nick

 

[flecc]

To get back to the question about two motors, the plan to use the second motor as a manually activated one that is used only on hills seems perfectly legal, particularly if the first motor is pedelec controlled, the second motor is manually controlled and the assist speed is less than 15mph. If the second motor isn't used all the time, but just on hills, then its power contribution cannot reasonably be said to be "continuous" using any normal definition of the word. It's a particular case where compliance with the law seems quite straightforward to prove.

Jeremy

I still disagree with this interpretation Jeremy. The law states maximum continuous rated power, not what flecc uses on his way to the shops. Note the word maximum, not what's used but what can be used. Any two legal e-bike motors exceed the legal limit and if the rider can use them both at the same time, the bike fitted with them is an unregistered, unlicenced and uninsured motor vehicle, lacking type approval. The consequences are expensive and are very likely to include loss of driving licence.

Some motors carry their rated continuous power on them, Heinzmann for example, and If I ride down the road with two basic Heinzmanns, each declaring it's 200 watts, I'm riding equipped with 400 watts of rated power whether I'm using it or not. The evidence of those plates is more than enough for the bike to be seized and crushed.

Whilst I agree that the likelyhood of detection is low, and have posted as much above, it's not non-existent. I know of one serving and one retired police officer in this forum where this law has been extensively discussed, and with 1 in 300 of the population serving police officers, on the basis of the law of averages there may be 4 serving officer members. Many Met Police officers are cycling club and CTC members and I'm sure this is true nationally, so the number of CTC police members will be at least in the hundreds, the relevance being that e-bike law has been discussed in the CTC forum as well.

Many areas including my own have had programs of seizures and crushing of illegal two wheelers, one seized in my area being an electric one, again showing the risk is far from non-existent.

Therefore the advice I gave to wibble was sound and safe, your contradictory advice at the very least being risky. However, I do derive some amusement from the vision of you arguing aircraft engine practice in the defence of an e-bike case in a magistrates court.
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[Tiberius]

Flecc, Jeremy,

If we may, for a moment, concentrate on the crucial phrase "maximum continuous rated power", or MCRP for short

Do you think that means the MCRP of the motor itself, or of the motor/controller/battery combination?

That would make a very important difference. For instance, a powerful motor that was limited either by controller electronics or battery voltage would be illegal under one interpretation and legal under another.

Nick

 

[Mussels]

Flecc, Jeremy,

If we may, for a moment, concentrate on the crucial phrase "maximum continuous rated power", or MCRP for short

Where would that power be measured - electrical input to the motor or kinetic output after conversion losses?

Edit:
Thinking about it how would the output power be calculated as it power = torque x angular speed. Legally on a pedelec power should decrease as the bike speed increases so using a high RPM is no good and torque drops of massively at low RMP in hub motors, so by my calculations whilst MCRP may be stamped on the side of the motor it would be largely irrelevant and unmeasurable in practice.
In the spirit of things I think power should be measured at the DC power supply as that can be easily tested and encourages efficiency, but who wants to make life easy for the authorities?

 

[flecc]

Flecc, Jeremy,

If we may, for a moment, concentrate on the crucial phrase "maximum continuous rated power", or MCRP for short

Do you think that means the MCRP of the motor itself, or of the motor/controller/battery combination?

That would make a very important difference. For instance, a powerful motor that was limited either by controller electronics or battery voltage would be illegal under one interpretation and legal under another.

Nick

In this context Nick, I don't think it matters, since most would use the appropriate controllers for the motors. There would be no point in fitting two motors which run at the same time and then limiting them to legality

As Jeremy has posted, it's up to the manufacturer to state their motor maximum rated power and that would be likely to hold sway at law. If, as in my example, my hypothetical two Heinzmanns stated themselves to total 400 watts, the law has been broken and it's demonstrable that I as the person creating that bike has knowingly broken it, leaving me without a viable defence.
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[Blew it]

Tiberius

I'm quite sure your right about the realities of two motors. To be honest, I'm more at home with lathe 'n' mill than anything electronic!. On the occasions when I have worked with electronics the results have been "interesting", (hence the forum "nick"). In defence, I should point out this was in the field of high powered RF amplifiers, I've yet to succeed in blowing anything on an Ebike....there's a first time for everything!.

Now, I'm sure this will upset a few apple carts, but the simple fact is, skinny over-pensioned retiree's such as Flecc, myself and others, will always enjoy better performance from a legal Ebike than those who admit to being "a bit overweight".

Perhaps that's the answer....shed the pounds guys and watch that bike fly!!.

INCOMING: rocket propelled skinny-envy!!!.

Ah, a big orange truck has just delivered a prezzy, Good old Bob in sunny Scotland has sent me a battery and charger without buying a kit, cheers Bob!.

Best wishes to all (honest)

Bob

 

[Tiberius]

In this context Nick, I don't think it matters, since most would use the appropriate controllers for the motors.

Flecc, I beg to disagree. It makes a huge difference. Motors and controllers generally come from different manufacturers. There is generally a choice of combinations and more than one appropriate controller.

What, for instance of the case of a motor, which the motor manufacturer declares is 300 W MCRP, and the bike manufacturer mates with a controller/battery that will only take it to 200 W MCRP?

Nick

 

[flecc]

Of course I agree with that Nick, but my point was as said, in the context that no-one is likely to controller equip a motor for less than 200 watts when they seek more performance by fitting two motors. Therefore they are certain to breach the 200 and 250 watt legal limits, since no controller combination they choose is likely to drop the motors to 100 or 125 watts each continuous rating.

In many and probably most cases as with Danny and his Powacycle proposal in another thread, an additional motor would be added to a bike that is already rated at the legal limit, so illegality would be assured with any added combination.
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[Jeremy]

This dilemma of how "continuous power" should be defined and demonstrated to a curious police officer is the root cause of the "two motor problem".

In essence, the onus is on the bike manufacturer to define a continuous power rating and appropriately placard this on the bike. There is a well-proven precedent in law for this being the case - motorcycles are required to have a data plate that states the power, and, in the case of mopeds, the design speed. If you modify a motorcycle (as I have just done) then you are required to amend the data plate accordingly.

There is also a precedent for determining who the vehicle manufacturer is in law. In the case of a home constructed, or significantly modified, vehicle, the "manufacturer" is the person who creates the finished vehicle. Again, I've direct evidence to support this, as I have had to take responsibility for being the new "manufacturer" for my modified motorcycle.

This leads inevitably to the conclusion that someone who converts a pedal cycle to an electric bike is almost certainly the individual who has to set the maximum continuous power rating. There is a clear logic to this; continuous power is a system rating, not a motor rating, nor a battery or controller rating. One reason for setting a lower continuous power rating for a system than any of the individual components can tolerate might be heat dissipation. Whilst a complete system (motor, controller, battery, cables and bike) might be able to deliver high power levels for short periods, a builder/manufacturer might, quite reasonably, wish to set a lower "continuous power" rating to avoid damaging heat build up in some of the components.

This is obviously what most (perhaps all?) commercial electric bike manufacturers do, as most (all?) of those available in the UK have a real maximum power that is greater than 250W. The many tales of battery cut-outs, blown controllers etc indicate that peak power levels are fairly high for many ebikes.

Jeremy

 

[Tiberius]

There is a clear logic to this; continuous power is a system rating, not a motor rating, nor a battery or controller rating.

Hi Jeremy,

This is the question I was driving at, but it got sidetracked by the two vs one motor point.

If you follow the logic through of basing the continuous power rating on the motor alone, then almost every e-bike could be shown to be illegal. From the engineering point of view it only makes sense as a system parameter.

I don't know how one would deal with the curious police officer who kept pointing to the label on the motor and saying "but that's a 500 W motor" or "but those are two 250 W motors".

Nick

PS. I think I ought to take the 406 sticker off my Crystalyte in case someone thinks its the power and not the model number.

PPS. We seem to have got off the two motor question, so apologies to the original poster, but it is an important discussion and not entirely irrelevant.

 

[Danny-K]

I think a better option would be a Tongxin Nano in the front wheel for four reasons...

Thanks for your suggestion Flecc. I agree with you on the Tongxin Nano - but they're practically unavailable to the end-user direct from the Chinese manufacturer of Tongxin. Tony Castles is the only easily orderable source in the UK of the Nano motor that I know of.
About £300 without the battery.

Whilst the Alien kit, not only has a potentiometer with which the owner can choose to derestrict, if they so desire, the 15 mph max cut-off point all the way up to 20 mph,
- BUT also comes with a 36volt 10 amp battery, (plus rear rack for the nicely designed battery), and comes in at £439 or thereabouts. In effect the Alien motor, on it's own is seriously cheaper than the Nano.

I also like the care that the Scottish AlienOcean retailer has gone to on his eBay site numbering all the wires to make things as simple as possible etc., However, if the Nano is the best choice, then eventually it would tell after the initial cost of the Alien had fallen from memory, and freewheeling motor capabilities became bothersome. My thinking is, with the initial cost of my e-bike plus the additional motor kit, I would have a bike to suit me for a final spend of £800- £900 all-in, whichever motor I chose.

Also, if ever I decided to sell the Salisbury, I would refit the original wheel and use the motor kit on one of my other pushbikes, (or what about this - fitted to a Kalkhoff, if a Kalkhoff was my choice in 2009 that is, whatever, my next e-bike MUST be from a manufacturer that offers a range of frame sizes).

Was talking it over with a friend at lunchtime today, raised eyebrows were the order of the day with the advice I should get my fitness level back to its previous level before making any further purchase decisions. Tend to agree with that - but that's what an e-bike is for, those occasions where your fitness is well below par, many have posted on here to going back to enjoying there pushbikes once again now that their e-bike has tuned up their fitness levels. So the two-motor option is on the back-burner for the moment; but what an opportunity - If I pay around or well over the £1k mark next year for THE bike of my final choice, a second motor fitted will be out of the question, it's now or never, what with my current cheapo second-hand e-bike, obtained for barely more than the price of a new battery.

Yes Danny, you could fit the front motor Alien kit to the Salisbury, but, you might have to replace the front forks with a pair designed to accept a motor hub. these are currently available from Wheelcare.co.uk on Ebay at around £24. I'm almost certain they have the 110 m/m clearance needed on the drop-outs...

Thanks for that advice Bob; I have seen that eBay listing previously. Measured the forks on the Salisbury at the time and I think they'd j-u-s-t lose out a smidgen, but not for the Nano motor.

Don't try running both motors off one battery, the combined demand would almost certainly result in enough voltage sag to trigger a low volt shut down. Anyway, the flat shaped Phylion 36 volt 10ah battery supplied with the Alien kit will easily fit on the Salisbury's rear rack...

And here you get right to the nub of the matter. I'm not enamoured of pre-calculating every journey to the last mile to see if I can make it back home with enough battery power still available to do so. I want to go off and clock up 40, 50, 60 miles and not give it a second's thought; just like on my 'tourer'. So the obvious solution, like so many others would be to purchase a second battery - £209 at present for the Salisbury, (24v/10.5amp). So... if I fitted a second motor, then that second battery, (about the same price as the Salisbury battery), would always be there and available for back-up duties to the salisbury's motor where the worst of the hills have it whimpering and running for cover. Wouldn't that be great? I reckon if either the Alien or Nano could give similar to the Salisbury's battery which currently allows me 27 miles per charge, I could expect 50 mile outings with power to achieve that minimo, AND 'cliff-face' climbing ability on tap, to boot! Yes?

...Obviously, there will be a little additional drag from the extra motor, but there simply has to be a net gain when both motors are pulling. If this extra drag became a problem on the flat, you could always give the "resting" motor a whiff of gas on the thumb throttle to even things up.

This how I think it would work.

On the flat, you could ride with normal pedelec controlled assist from the existing rear motor. When approaching a cliff face, you would then whack the thumb throttle supplied with the front motor wide open, and storm the hill with two motors pulling. Don't expect to go scortching up the hill like a half arsed astronaut, more likely the machine will slow to around 10 MPH which is the roadspeed at which these motors achieve maximum torque. The realm of fantasy maybe, but food for thought none the less...

Yes, that's how I envisaged it, otherwise the two batteries would effectively only last the lifespan of one battery. Expensive, if both used uneccesarily at the same time. (Well 25% of the front motor's battery would be used at the same time as the rear motor's battery when called upon for 'hill duty').

As to motor drag; that's a point that made Flecc choose the Nano motor, it's ability to freewheel better than most. Would the drag from both the Alien and the Salisbury motors hinder badly if/when I had to pedal home with two exhausted batteries I wonder?

 

[flecc]

This leads inevitably to the conclusion that someone who converts a pedal cycle to an electric bike is almost certainly the individual who has to set the maximum continuous power rating. There is a clear logic to this; continuous power is a system rating, not a motor rating, nor a battery or controller rating. One reason for setting a lower continuous power rating for a system than any of the individual components can tolerate might be heat dissipation. Whilst a complete system (motor, controller, battery, cables and bike) might be able to deliver high power levels for short periods, a builder/manufacturer might, quite reasonably, wish to set a lower "continuous power" rating to avoid damaging heat build up in some of the components.

Jeremy

But as I've observed Jeremy, many if not most would be adding a kit motor to an electric bike which already had a stated continuous rating at or about the limit. With the kit also having a defined manufacturer limit, I can't see this "vehicle creator" argument standing up in any court. It would merely be adding additional power to an existing e-bike rather than creating an entirely new vehicle from a bicycle. It would be a pairing of two of the complete systems you mention. Your heat build up mention seems to me to be just clutching at straws, since we are speaking of previously defined maximum continuous ratings of known systems, by definition not subject to damaging heat build up.

I don't think most people would want to place themselves in the position of having to argue the tortuous and unproven case that you make for legality, based as it is on motor vehicle legislation which e-bikes are outside of. My advice therefore remains that two legal e-bike motors on one bike are illegal, this being the safe position, and I believe the correct one.
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