Light weight folder

[mwood]

I'm just getting exposed to the idea of an electric bike and am thinking about converting my folder for commuting. I recently picked up a Dahon mu sl which I take with me on the train. It’s a little bit awkward on the train but at 8.7 kg. w/o pedals (19.1 lbs) it’s more than manageable and it’s a lot of fun to ride. I fold it up on the train platform and just drop it in the top luggage rack as I board the train or in the over head bin above my seat.

I had never heard of an ebike when I bought it. But, I ran into a young fellow a few weeks ago who was riding one – What a wonderful idea! Poking about the internet, it appears I have an opportunity to fashion a very light weight folding ebike, which is key if it is to be manageable on the train. The battery would go in the backpack and the bike should be below 14 kg (~30 lbs). My hope would be to extend the range for a half hour ride from about 6 miles to 9 – 10. This would require the electric motor to drive the bike up hill at speed at least 15 mph. Do you think this kind of weight and power is feasible?

I’m finding it frustrating to evaluate products the specifications appear limited and unclear and I have no idea how to relate watts and amp hours to bike performance. I’ve been looking at cyclone and rabbitttool. They seem to make the most sense to me at this point - A cyclone motor kit with a rabbittool NiMH battery pack. Looking closely I find the cyclone does not support a 9 gear cassette or the frame for this bike. They encourage inquiries for special adaptations. So I sent an email inquiry but have not gotten a reply. I’m sure I can adapt a bracket to mount the motor, but does anyone know what the issue is with a 9 gear cassette? Will the 500 watt motor go up hills at speed? What size battery do I need?

Any Comments or Suggestions are welcome!

Thanks
Mike

 

[flecc]

Hello Mike. A to B magazine specialise in electric bikes and folders, and they've searched for years for a viable portable solution. They seem to have cracked it this month with a Brompton fitted with the fairly new Nano motor, a tiny front hub motor, very light and able to use quite light batteries.

It's well worth you getting a copy of that latest June issue to read the long test of the system, here's their contact page.

Give them a ring to buy the issue or subscribe. There's also a list of bike shops stocking the mag on their site.

The nano motor kit you can get from Electrodrive on this link. where you'll find plenty of information, video etc.
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[JohnInStockie]

Brompton with Nano

I must say, A to B are well impressed with that Nano motor on the Brompton. I think they are of the opinion that its the best e-bike they've ever seen, and it does indeed have some amazing test results. No chance of bias though is there..

John

 

[flecc]

There is a bit. A to B have been teasingly called the Brompton owners magazine, since they've always been Brompton fans, and in this case had a small involvement in the development of the Nano version.

However, there's no commercial interest involved, and in fairness they have warned about the possibilities of availability and reliability issues with this new product. Nonetheless, it's technically in the lead at present where electric folders are concerned.
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[JohnInStockie]

Yes just teasing a little I think that it does seem to be a considerable breakthrough, although I am a little sceptical personally. I dont understand how they can have such results with known technology, technology which the Q bike itself uses too, but with far more pronounced results. I have a feeling that the rider of the bike was maybe not as heavy as the 'average' rider. Too good to be true IMHO

 

[flecc]

This is what lies behind it John.

The Nano-Brompton A to B magazine test hailed it as a breakthrough electric folder, with an achieved range of 47.9 miles on a 266 W/hour battery. However, read the following six sentences from the review:

1) The silent waft of power keeps coming in until just over 14 mph, when assistance suddenly ceases.

2) Most riders will go faster if conditions allow, but when the next hill approaches, you simply reopen the throttle.

3) Maximum assisted speed is barely more than 14 mph (13 mph as the battery approaches empty).

4) Our ten mile commute takes 37 minutes ( My added note, that's an average of 16.2 mph)

5) Our commuter route is largely flat

6) We should put our figures in perspective because if you don't pedal the Nano-Brompton, you might see less than 20 miles, and if you pedal with limited enthusiasm, you might see only 30 miles.

You can see that the bike was actually being ridden much of the time beyond the motor contribution speed, and the tester won the Presteigne race in year one and was podium placed the second year, so is a very powerful rider.

It's weight is good but not unique, at least two others matching it, but my reading of all this is that the breakthrough is largely illusory. If any bike's motor is internally geared to stop contributing at below the speed a rider can cycle it, that too will give a very long range. But that's a test of the rider and the cycling qualities of the bike, not of the motor.

I had, after all, already done this on my Q bike. Derived from the Quando, it's cycling qualities improved out of all recognition more than doubled it's range as a result, while still retaining motor drive to over 17 mph, far faster than the Nano. If I'd put the motor into a 16" wheel instead of it's 20", reducing it's assisted speed to just under 14 mph, that would again multiply the range due to the rider.
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[JohnInStockie]

Thanks for pointing that out clearly Flecc. I note that 'with limited enthusiasm, you might see only 30 miles' comment would make it the best electric folder in the world wouldnt it, the original Quando only advertising a range of 15 - 20 miles for reference. I dont understand how a similar bike with similar designs can do so much more, unless it really is the rider and not the bike, in which case there isnt anything there that doesnt presently exist, apart from the fact that it is a Brompton.

John

 

[flecc]

The Quando only has a single 70" gear which limits the pedalling to below 15 mph for most riders John, but it's motor drives to 17 mph. Therefore it's the opposite to the Nano Brompton where it's the rider who is the faster.

Therefore the Quando is effectively only on motor drive so has the shortest range, but as I said, if it's motor was put into a 16" wheel so it drove below the rider's speed, the range would leap up, since the motor would be idling always on the flat. And that's what the Nano does of course.

In fact if that Nano Brompton was used in a more mixed territory than flat central Dorset, ridden by an average rider, I think 25 miles would be more likely the best it achieved.

So we are speaking of a trick here. If a motor, any motor, is limited to below the comfortable riding speed for a bike, in flat conditions it will have a huge range, the motor only in use on hills. But the range is only high because the rider cycled it along the flat and downhill, not the motor.

However, it's not a deliberate bit of cynicism on the Nano Brompton producer's part, it just arises from the highest speed hub available being used in the Brompton wheel that's a touch too small, so only giving assist to barely 14 mph.
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[mwood]

This is some good information and discussion. Sorry for the delayed response but we've been on holiday. At any rate, this idea of assist on the hills is exactly the kind of thing I’m looking for with the addition of the flat in a head wind.

I’m not afraid of peddling. I find a leisure peddle for me averages 13 ¼ mph, and if I push it really hard maybe 15mph tops. I have a ten mile trek at one end of the train and six on the other. So I catch I ride on the ten and peddle the six. It keeps the old man in shape – well kind of. My expectation for an ebike conversion, is to hybrid peddle both. For this to be realistic, the peddle has to be about ½ hour tops, 10 miles in 30 minutes or 20mph. That’s the legal limit hear in the states. Approaching this will require climbing hills at speed, power assist in the head wind and peddling like the dickens otherwise. I wonder if a 17mph goal is unrealistic that would put the ten mile trek at 35 minutes and the six at just over 20 minutes. Ya! That would do it

From what I read, peddling is in the 150 watt range. So I just can’t imagine that a motor could do this unless it’s 2 to 3 times the power (300-500 watts continuous) with some type of controlled gearing.

Looking at the nano motor, the size and weight is good, but I’m concerned about the power. The actual spec is 180 watts continuous - “powers you to 15mph” and “helps you climb hills ~14%”, which reinforces the concerns raised about the high end peddler. I just don’t think this will cut it. I suspect a more powerful motor maybe 350 watts continuous, geared and a similar weight class might prove a bit more interesting for my expectations.

Rabbittool also makes a geared hub motor. I can’t seem to find specific weight or power for the motor. But judging from what I see it’s in the same range as the nano.

I came across this JV Bike -- Dahon + BionX ... it looks really nice, as near as I can tell, though the bionx is a gearless hub. What’s up with that, I just can’t imagine that it could maintain a descent speed up hill without the gearing. Is this correct? And the price – Wow!

I really like the hub idea, but I’m just not finding a geared hub motor with the weight and power. Then there’s the issue of shifting which seems to be illustrated quite nicely in this discussion. So I guess I’m still looking at the cyclone; does anyone know what the issue is with the cyclone kit and a 9 gear cassette? Is it 9 gear chain angle possibly being too acute for the cyclone motor sprocket?

Thanks
Mike

 

[Ian]

does anyone know what the issue is with the cyclone kit and a 9 gear cassette? Is it 9 gear chain angle possibly being too acute for the cyclone motor sprocket?

Thanks
Mike

Just a guess Mike, but it could be that the sprockets are designed for use with wider 6 speed chains rather than the narrower 9-10 speed types. This would make sense as the chain carries the motor power in addition to the rider input, and with the high power kits this would put a considerable strain on the chain.

 

[flecc]

Yes, agreed with Ian on that difficulty, but there's another aspect to the Cyclone as well, particularly with a small wheel bike.

The Cyclone drive sprocket and nylon idler sit to the rear of the chainwheel and shorten the distance to the rear sprocket cassette. Now subtract that from the already shortened chain length on a small wheel folder, plus the width of the nine sprockets and you can see that there's some extreme angles involved. It's possible that a chain couldn't cover that range of angles, and the nylon idler edge guides might also not cope with such chain angles.

I don't know of a suitable motor to give the performance that you're looking for offhand, though the Crystalite front hub motor range has some powerful models. The range should be sufficient then with a viable battery weight, but there's also the question of the motor fitting into the fork width.

One thing I can say with certainty, to have a bike with that performance at under 14 kilos is right at the borderline of what's possible and would demand a very light bike like yours. Here's a US site which has the Crystalite motors shown, click on each for details. The bottom one we know in the UK as the Puma motor in a 400 watt version.

motors kits
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