This is a 'Let's all save cwah from himself' thread :)

AndyOfTheSouth

Esteemed Pedelecer
May 15, 2009
347
4
Dear cwah

Your constant discovery of bikes of varying degrees of exoticism are a delight and please continue with them. However, I cannot be alone in worrying that you will soon buy one of them and (again?) be disappointed.

If these bikes have anything in common it is that they are all too small, too big, too heavy or come from a supplier who is too distant or too dodgy and usually all of these combined.

Yet it need not be. You have stated your requirements with admirably clarity. You live in a small flat up two flights of stairs. You do not want to leave your bike outside the flat or any shops or offices that you go in. You want something you can carry with you. You don’t ride more than 10 miles.

With these requirements, there is no puzzle and no quest because the problem solves itself. Only one bike has a fold which is compact and rapid enough, a reasonable weight and decent ride. You need a Brompton.

The only real question is which one. The answer to this depends on how hilly is your home terrain and how much you are prepared to spend. However, the guideline must be to buy the lightest you can afford, since this makes a big difference when carrying any distance.

The ideal would be a titanium version, but you can save a lot of weight by having only two gears. Do not be tempted by any additions such as bags. You can put your shopping in a rucksack. The only worthwhile addition (apart from lights, you can have those) is a slip carrier to make the Brompton look like a slightly eccentric small suitcase when you take it into a restaurant.

If you are reasonably fit and the terrain is relatively flat, don’t bother about a motor. You will save weight and money.

If you really are set on an electric version, currently the answer is a Tongxin motor and a small, detachable battery. There are a couple of companies which offer this conversion.

However, since you are keen to do it yourself, why not simply do exactly as Jerry has done? He has just what you need.

I imagine you are now saying ‘But I want a bike that will let me break the sound barrier!’ Or is it to average 30 miles an hour? It doesn’t actually matter which, since both are impossible in a electric bike that you can carry around with you.

Best wishes

Andy
 

jerrysimon

Esteemed Pedelecer
Aug 27, 2009
3,292
112
Cambridge, UK
Funny but true. I have done my best to help but much as I realise that the eBrompton is not the solution for everyone in this case I think it is.

As you say, and I have no idea how young or how fit cwah is, an unassisted Brompton might also be the answer. If more power is required than a Tongxin then perhaps a Q85 motor which I am about to test.

A second hand Brompton might help if funds are an issue.

I also think cwah might get away with a DIY battery like mine, if his trip mileage is less than 8 miles and again dependant on his trip terrain.

I am however very thank full for all cwah's posts, as for a change the forum has been dominated with small wheel bike posts :p

I have searched high and low for something similar to a Brompton but with full suspention. For me that is a Moulton TSR2 but even that does not have the same portability. The other bike I would like to see/try with a motor attached is Alan's 8.2kg Dahon hybrid.

Regards

Jerry
 
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funkylyn

Esteemed Pedelecer
Feb 22, 2011
3,172
27
South Shields, Tyne & Wear
I have to admit to a frisson of concern at buying from someone called 'con his motor'........

Lynda :)
 

Scottyf

Esteemed Pedelecer
Feb 2, 2011
1,403
-1
Poor cwah, it's the need to have every thing in one package. It's hard to get everything you want in one bike. It's no ones fault. It's just the way it is. You can only get closer to it.

I do worry about small wheeled bikes doing 30mph. That speed is fast enough on my 28inch wheeled bike. It's pretty smooth but small wheels on that would be scary.

I think a good compromise would be a portable bike of some degree, then use a lipo bag with a 250w motor and over volt it for 20mph ish. This will be a good compromise in cost and weight and reliability.

30mph is achievable but you need a heavy motor. Then you loose the weight part. It'll also eat batteries at that speed. Again adding weight.
 

flecc

Member
Oct 25, 2006
53,604
30,874
I do worry about small wheeled bikes doing 30mph.
On my 20" wheel folder I regularly reach over 30 mph for long periods down my longer hills and it's eZee motor easily takes it back up them. Steering and brakes ok too after their modifications. Before cwah gets excited though, it weighs 25 kilos, so not one for the staircase or public transport.
 

Scottyf

Esteemed Pedelecer
Feb 2, 2011
1,403
-1
Living on the edge flecc!
 

catsnapper

Pedelecer
Following on from Jerry's comment about my Dahon hybrid, I'll be trying a Q85 on it which will take the weight to 10.1Kg. Add on 5 or 6Ah of Lipo, controller etc, should end up around 12-12.5Kg, although there is the possibility of a bit more weight skimming:)

Not as compact as a Brompton, but cheaper and lighter.

Alan
 

flecc

Member
Oct 25, 2006
53,604
30,874
Living on the edge flecc!
It certainly was before the steering and handling were sorted, then it was terrifying! Not too bad now, except just a bit edgy on the bumpy bits. I can even give arm signals at up to 30 now, something that was suicidal when the bike was in it's original form, very narrow bars, floppy steering column folding joint, dodgy riding position and nondescript Chinese fat tyres.
 

cwah

Esteemed Pedelecer
Jun 3, 2011
3,048
179
www.whatonlondon.co.uk
Thanks for this thread guys. That's true I'm going to buy another bike and maybe I'll get disapointed. I know brompton is a very good bike but I wouldn't have many choices of motors. If I get this bike I'd probably get a crystalyte 209. Problem is that from what I've seen it has a very bad efficiency. Something like 16wh/km at 34kph max speed.

So the only alternative (to reach convenient speed) is to get a bigger bike that accepts 135mm wide dropout. For security, it seems that suspension is a must, and dahon jetstream is maybe the right alternative. It would weight around 20-22kg at the end with BPM and lipo, but maybe I can accomodate because the perfect bike doesn't exist. It's a matter of compromise.

Catsnapper, what model of dahon is your hybrid bike? Is it a full sized bike?
 
D

Deleted member 4366

Guest
Cwah, It's brilliant that we have guys like you around that aren't put off at the first hurdle. When you try things, you find out facts which you can learn from. When you publish your results, we all learn. Some like to stick within all the current theories, others just like to try things, learn and move on. Keep chasing your dream: The worst that happens is that you lose a bit of money andhave o think again. You can always find a use for all the bits anyway.
 

catsnapper

Pedelecer
The folder is this one, a Dahon Uno:



A full size Dahon folder that eventually had a BPM motor is this one:



The Crystalyte 209 is discontinued and due for replacement about now. A big, heavy DD motor may not be the best idea on a small wheel folder, adds a lot of unsprung weight, and if you need to pedal one without power.......:(
It's not the heaviest DD hub, but it still adds a lot to a lightweight bike.

Alan
 
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cwah

Esteemed Pedelecer
Jun 3, 2011
3,048
179
www.whatonlondon.co.uk
Cwah, It's brilliant that we have guys like you around that aren't put off at the first hurdle. When you try things, you find out facts which you can learn from. When you publish your results, we all learn. Some like to stick within all the current theories, others just like to try things, learn and move on. Keep chasing your dream: The worst that happens is that you lose a bit of money andhave o think again. You can always find a use for all the bits anyway.
Not sure if I should take that as a compliment but yeah I like experimenting. You only know once you try it anyway.
 

cwah

Esteemed Pedelecer
Jun 3, 2011
3,048
179
www.whatonlondon.co.uk
Catsnapper, from what I understood, a new model of crystalyte 209 is going to be sold soon. The motor is not that heavy (3.9 kg for the "old" 209). Main concern for me is it's a big front motor (not stealthy at all) and the very poor efficiency. But I'll try to know more about this motor before drawing any (hasty) conclusion.

I just have the answer from AMXMA manufacturer, they took a bit of time so I thought they ignored me:


He just answered my question about dropout:


145mm dropout. Perfect for the Cute 128. It's lighter at only 3 kg. This motor is weaker than Bafang motor, but it's lighter and more stealthy. I may purchase the rear model at 328 rpm. I can then use in series 3 lipo at 18.5V8AH.

At 11.5kg bike + 3 kg motor + 3 kg lipo + 1.5 parts and accessories = About 19-20 kg bike. Not too bad.

Top speed would be lower than expectation, but this bike don't really seem strong and because it's 7005 aluminium frame, I fear it may break.

Price wise:
- 300 USD bike
- 270 USD shipping cost
- Probably 15-30 USD conversion charge
- Probably 50 USD customs charge

Around 650 USD all included, so 420 GBP.

Worth it? Or shall I stick with the Bafang+ (or get another bike?)
 
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jerrysimon

Esteemed Pedelecer
Aug 27, 2009
3,292
112
Cambridge, UK
That looks more like 128mm dropout spacing the way the tape measure is positioned. Drop out spacing is always measured between the two inner faces of the frame drop outs not the outer faces.

Note with customs duty and VAT you may find yourself paying more than 50USD.

I agree its great to see people considering the many different alternative donor bike options. I just don't see you carrying any of these bikes into shops, except maybe the Dahon hybrid. They will require locking up outside which is fine. Yesterday I took the Brompton into the Postoffice to post parcel and then to the Chemist to pick up a prescription. However I agree if you are set on getting a rear motor the Brompton is not the right choice.

PS what does it mean by neutral gear ?

Regards

Jerry
 
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NRG

Esteemed Pedelecer
Oct 6, 2009
2,592
10
Yep, 128mm...d8veh bought a cute motor I think but I'm not sure if he's posted on how well it goes, freewheels etc....would be interested myself...
 

catsnapper

Pedelecer
As Jerry says, the dropout looks approx 128mm, no doubt meant to be 130mm, a bit narrow for a rear motor that might exceed the nominal 135mm.

I'm not sure it makes sense to pay more for shipping and taxes on a bike of unproven quality, when the same money will buy a better product locally.

Proven bikes with an excellent reputation like the Xootr Swift Xootr Swift Folding Bicycle : Xootr Urban Transport would probably be more suitable for a rear motor.
Combined with a 393rpm rear Bafang BPM, wheelies would be a real possibility:)

Alan
 

Scottyf

Esteemed Pedelecer
Feb 2, 2011
1,403
-1
Even on 15s lipo this is going to give you a max rpm of 600 (about 30 ish mph in a 20inch wheel). Which is going to be spinning the wheel fast.
To the point where to get smoother running it will be best to use Hall sensors on the cheaper controllers.

Even then you run the risk of melting them if the amp's on the controller are high.

I like the idea of having a fast, small, lightweight bike. An i set out to keep my bike as much of a bike and light as possible. But even being back to unassisted riding its so different to Electric power.

30mph is very quick. a comfortable speed should be around the early 20mph. This is also fast enough to keep up with alot of traffic and out perform most average roadies.

I like the idea of you using 3x 5s lipo. Its about as light as it can be with the current Battery tech and will offer something quick.

The only way to get more speed with smaller motor is to not use a hub motor but something more bespoke with gearing.
 

cwah

Esteemed Pedelecer
Jun 3, 2011
3,048
179
www.whatonlondon.co.uk
JerySimon, the neutral gear is a gear you can "unplug" once folded. So when you move the bike backward the pedal doesn't move at all. Quite interesting concept. Why couldn't I move this bike into shop but it would be possible with the Dahon hybrid? What's the main difference?

I've seen Xootr has really good feedback online. However it doesn't fold that well. I've found this deal on ebay: XOOTR SWIFT FOLDING BIKE | eBay
At 400 GBP is it still a good deal?

Themutiny, this bike is really heavy, and it has a tiny battery (28.89V 6AH = 174 wh approximatively)... No way I'll ever get this bike.

Scottif, I'll see why I cycle at what speed it would be the most comfortable for me. I'm thinking about 3 speed switch (maybe a cycle analyst can do that?) so if it's too fast, I can still set the speed lower. I'm doing that with my actual bike now.

So maybe the best choice for now are either the jetstream or the dahon speed?