Two motors?

Anybody ever tried a front and rear motor on a single bike?

 

 

Maybe I should make a trike. err.. e-trike?

Anybody ever tried a front and rear motor on a single bike?

 

 

Maybe I should make a trike. err.. e-trike?

 

 

a trike with 2 motors on the back sounds more sensible.... but probably means twin batteries as well

People have; there is a picture somewhere on here of a Lafree with at least two motors on it. Unlikely to be the most efficient way to power a bike, but perhaps one high geared and one low geared motor might be a reasonable way to get hill climbing and speed from a bike. No reason why you couldn't power both off the same battery.

This is the pic I published that Frank refers to. It's a Lafree with the Panasonic chain drive motor and a Heinzmann 24 volt front hub motor, and either can be run from the Lafree battery behind the seat tube.

 

On the carrier is a tiny petrol generator which can charge the battery or which can be used to couple with the battery to run both motors at once.

 

http://users.tinyworld.co.uk/flecc/images/Two%20motor%20Lafree.jpg

Ooooh!

 

So I would be able to climb hills much easier?

 

I was thinking about adding just a small motor to the front of my Wisper and one of those small Lifepo4 batteries. I would only activate the front motor when climbing steep hills.

 

Would this be practical?

Yes, entirely practical. Obviously it's illegal to have two running at once and technically illegal even to have a bike that can do that, but no-one's likely to spot it, as the blatantly illegal one I showed demonstrates.

 

A two motor bike would murder the hills.

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Thanks, flecc!

 

I'm gonna seriously consider murdering a hill near me.

 

...before it murders me.

Yes, entirely practical. Obviously it's illegal to have two running at once and technically illegal even to have a bike that can do that, but no-one's likely to spot it, as the blatantly illegal one I showed demonstrates.

 

A two motor bike would murder the hills.

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Is it actually illegal to have two (or more) electric motors as the above seems to state? The EAPC regulations just give an average power limit, I can't see a mention of number of motors in them.

 

The older Sparc hub motor had two motors as I recall, albeit tiny model-type brushed ones, yet was legal, I think.

 

Obviously the petrol engined generator in the bike illustrated takes it outwith the EAPC rules and into the light moped class, but two (or more) electric motors with a combined average power that doesn't exceed 250W and with a power shut off speed of 15mph would seem to be legal.

 

The rules allow peak power to exceed average power by an unstated margin, so depending on how the average was calculated you might be able to argue that a bike with a high peak power from two motors could still be legal if it's average power was limited to 250W. It all hinges on the period of time over which the power is averaged, which isn't given in the regulations. If the average over 15 minutes is OK, then it would be possible to have maybe 500 to 1000W for short bursts up hills.

 

The challenge would be proving that the bike was illegal, which might well be a struggle for the authorities. If the bike were fitted with something like a Cycle Analyst, then the average power would be easy to demonstrate to anyone that inquired. An average ebike seems to need 12 to 18 watt hours per mile to run at an average speed of perhaps 12 to 15 mph. Assuming 15mph average speed, then as long as the watt hours per mile figure is below 16.7 then the bike is running at 250W average or less, so is legal.

 

It would be hard to exceed 250W average if the speed were limited to the legal assist speed of 15mph. My guess is that, with speed limiting, it would be OK to use maybe a 1000W motor and still remain legal, depending on terrain.

 

Interestingly, my big Crystalyte motor had a peak power on 48V of around 1500W, yet the average power on the short test I did with it was less than 250W by a fair margin, even though my average speed is high on the recumbent.

 

This average power law is so full of exploitable loopholes as to be fairly daft, in my opinion.

 

Jeremy

 

 

 

Jeremy

Edited October 20, 200817 yr by Jeremy

The point Jeremy makes about legality and proof is quite correct.

 

Firstly a copper has to be aware of the legislation which surrounds electric bikes, this is neither part of initial training nor specialist training for RT officers.

 

In the event you were unlucky enough to be stopped by someone who had acquired the requisite knowledge and was bent on a prosecution then to prove beyond a reasonable doubt that the law had been broken the bike would have to be seized and submitted for a forensic examination.

 

The problems would then really begin, the officer would in almost all cases have to justify to their local forensic manager (usually a DI) spending £££s sending the bike to The Forensic Science Service - UK who would then outsource the very specialist examination to an independant.

 

Frankly unless you'd run someone down and killed them the chances of a DI spending this sort of money is as likely as find Life On Mars (ok so it looks like they have).

 

I know people like this even now, watered down and older but with the spirit of Gene Hunt burning inside, there's a leaving do once a week at one WMC or another, imagine trying to get 'a request to have a push bike examined' past this guy...........

 

YouTube - Gene Hunt - Bad Reputation - Life On Mars

In the event you were unlucky enough to be stopped by someone who had acquired the requisite knowledge and was bent on a prosecution then to prove beyond a reasonable doubt that the law had been broken the bike would have to be seized and submitted for a forensic examination.

 

Hi Everyone,

 

I would be a bit careful about this. There's theory and there is practice.

 

First the theory: Some of the Road Traffic Act works on a "reverse burden of proof". The authorities point the finger at you, and you have to prove you are innocent. This has survived challenge under the Human Rights Act, with a judge declaring that by taking out a driving licence you are agreeing to a different set of rules. This only applies to certain parts of the Act, but its worth reading very carefully.

 

Now the practice: Suppose the police just seize the bike. Every time you ask for it back, you are told they are still looking into it. At the very least you are put to a lot of time, trouble, possible expense and you are without your bike for a period. You never get prosecuted, you never get a chance to defend yourself, but you will have had a punishment served upon you and will be expected to be grateful it wasn't worse.

 

Nick

Tiberius you are thinking of 'absolute offences' driving without insurance being the classic example. You drove your car on a road and you have at no time been able to provide any proof that you were insured to drive the car, you were therefore uninsured and will be convicted accordingly.

 

Issues surrounding wattage, power, speed, fitment, etc would all require to be evidenced hence the requirement that the cycle is examined, only with this would would an information be laid at Mags Court which would result in the issue of a summons and then breach of electric cycle legislation would likely be an 'absolute offence'.

 

My point based on 22yrs of theory AND practice is that the chances of this happening are virtually nil unless you offend so seriously that a person is killed or seriously injured or cycle past a Police car at 30mph giving them the finger.

 

There are far too many kids in Corsas crashing and killing themselves, drunks, uninsured Eastern Europeans and speeders in X5s to keep your average traffic officer in work without having to resort to dealing with 'push bikes'.

Hi,

 

I don't know about absolute and non-absolute offences. One that is specifically listed as a "reverse burden of proof" is drunk in charge, or at least the various defences and exceptions to it - the defendant has to prove he is innocent; the prosecution only have to point the finger.

 

My point is that, in practice, that principle will get extended to other offences. In practice, you will have to show you are innocent. You will have to mount a defence, rather than twiddling your thumbs and saying "the prosecution have to prove it". The court will start with the assumption that the prosecution is a professional organisation that has done its homework. The very fact that you are there is reasonable grounds for assuming you are guilty.

 

Even if you win, you will have suffered. It is best avoided.

 

Nick

 

Is it actually illegal to have two (or more) electric motors as the above seems to state? The EAPC regulations just give an average power limit, I can't see a mention of number of motors in them.

 

 

No, but the power limit would clearly be exceeded with any two bike motors Jeremy, hence my saying two motors illegal, not to be taken literally.

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No, but the power limit would clearly be exceeded with any two bike motors Jeremy, hence my saying two motors illegal, not to be taken literally.

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Suppose, though, that you had some control circuitry that limited the average power. This strikes me as a case where you would be in compliance with the law, but could have to go to a lot of trouble to prove innocence if charged.

 

On the other hand, suppose the control circuitry was as simple as a switch that only allowed one motor at a time to be used. That would be easier to demonstrate compliance, and if one motor were geared for low speed and the other for high speed, it would be justifiable too.

 

Nick

No, but the power limit would clearly be exceeded with any two bike motors Jeremy, hence my saying two motors illegal, not to be taken literally.

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With respect, this isn't the case at all. The EAPC regulations don't restrict peak, or maximum, power at all. It would be perfectly legal to have a two motor setup that had a maximum power well in excess of the 250W average allowed in law.

 

Some countries seem to have regulations that limit maximum power to a low value, so some of the motors we have here are similarly power limited. Our regulations aren't phrased like this.

 

In practice, an ebike that's limited to 15mph maximum assist speed is very unlikely to exceed 250W average power, so just fitting a speed limiter would most probably make even a 1kW ebike, or an ebike with two 500W motors, perfectly legal.

 

Jeremy

 

With respect, this isn't the case at all. The EAPC regulations don't restrict peak, or maximum, power at all.

 

Jeremy

 

I'm well aware of that and meant the legal power limit Jeremy, two motors of 200 or 250 watt rating would exceed that.

 

Surely I don't have to go into endless detailed explanation with every post? I merely advised wibble of the illegality of having two e-bike motors running at once, and it is illegal due to the total of the ratings.

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Flecc,

 

I don't mean to be at all awkward, but do like to see accuracy. We all know that the maximum power limit for an EAPC isn't 250 watts, that limit is an average power limit. Many motors (probably most) have a maximum power output of well over 250 watts. A quick glance at some controller ratings will confirm this - 250 watts implies a 24V controller that's limited to just 10.4 amps, or a 36V controller that's limited to just 6.9 amps.

 

As I posted earlier, if the maximum assist speed is limited to the legal limit of around 15mph, then even with two (or more) powerful motors the bike is unlikely to exceed the 250 watt average power specified in the regulations.

 

It's the power demand of the bike, not the motor, that will effectively set the average power if speed is limited, just as it is with a car or any other vehicle. For example, if a car is fitted with an engine with twice the original maximum power, it still doesn't use any more power to travel at a given speed than it did originally.

 

Jeremy

Edited October 20, 200817 yr by Jeremy

I know that considerable licence is taken by manufacturers on the basis of the assumption that it's average power as you've stated Jeremy, but the law doesn't say that. It's continuous power, not average power, and many of our motors are easily capable of continuous outputs well in excess of the stated limit:

 

Department for Transport - Electrically Assisted Pedal Cycles in Great Britain

 

Maximum continuous rated power output of the motor shall not exceed

 

- bicycle: 200W

- tandem bicycle: 250W

- tricycle: 250W

 

That's me being even more accurate, but to what end? I just try to post responses in a way that's straight forward and helpful with minimum complexity as I think that's what most enquirers welcome, but of late it's become increasingly difficult to do that without challenges.

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Please don't get offended by challenges, Flecc, it goes with the role you've established for yourself.

 

Continuous power as a legal definition is even more subject to questionable interpretation than average power. Here's an example:

 

In the aircraft world, engines have a rating known as MCP, maximum continuous power. Several key performance factors can be linked to MCP, nowadays the most likely figure is specific fuel consumption. This rating can also have legal implications for things like certification.

 

One easy way for a manufacturer to make his product seem more attractive in these fuel-efficiency focussed times, or to allow it's fitment to an airframe that would otherwise not legally be able to take it, is to just arbitrarily adjust the MCP figure down a bit. This will have no practical effect on performance, but will reduce the SFC figure that he can quote in advertising, or, perhaps, allow the engine to be fitted to a type that might otherwise have not had enough spare empty weight to use the engine.

 

What's this got to do with ebikes I hear you all asking? Easy, all a manufacturer needs to do in law to comply with the "continuous power" rule is print a placard that states what it is. In practice this is what many ebike manufacturers do. Just look at the motors that are advertised as being rated at 200 or 250 watts. Do their controllers limit current to the low values I mentioned above? Of course they don't, most controllers allow motors to absorb at least 500W, many will supply far more power than this to a motor.

 

Even the tiny little Tongxin motor that I'm running has a placarded power limit on the motor - it reads "rated power 160W". The label on the equally tiny controller, however, reads "36V, 15A", meaning that the motor can actually take 540 watts. I know from personal experience that the motor will take 15A at 36V for long periods of time without getting warm. It's obviously got a practical continuous rating that's a lot greater than the stated 160 watts, but only the manufacturer can stipulate what the continuous rating really is.

 

If I were a motor manufacturer, then I might want to be very sure that my motor would not overheat if it was operated in temperatures of, say, 45 deg C (typical mid-summer temperatures in some middle east countries). I might well build in a safety factor to the rating to allow for this. The motor would then, accidentally, be capable of operating at a very much higher continuous power level in temperate climes, but would this render it illegal?

 

The EAPC law is so full of ambiguities and loopholes that I don't think there's the slightest chance of anyone being successfully prosecuted purely on the basis of the power limit. The same can't be said about the maximum assist speed though, as that is relatively simple to check. As I posted before, it's quite easy to show that if speed is limited then the "continuous" power is as well, in effect.

 

Jeremy

Edited October 20, 200817 yr by Jeremy

I agree on the questionable interpretation Jeremy, and also with your previously stated view on the daftness of this continuous/average law.

 

As for the challenges, it's not so much a matter of being annoyed but of the effect on my activities. The problem is that when I'm challenged with someone saying in effect that what I've posted is wrong, I'm then left with two options. Either ignore the challenge and give the impression to our many visitors and new members that I haven't a clue on the subject, or spend time, as in this thread, endlessly discussing or arguing the point.

 

The first option isn't palatable of course, and the second is not what I come in here for, that being merely to give help where possible in a simple, clear and straightforward manner. Of late the frequency and irksomeness of the challenges has led to me often not giving an opinion in answer to a thread question just to avoid the inevitable nit picking responses , and that leaves me feeling increasingly uncomfortable in this forum.

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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.

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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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

Edited October 21, 200817 yr by Blew it

 

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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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