Dahon/Tern rear wheel conversion?

[Chris Maluszynski]

Has anyone converted a Dahon (I'm looking at the Speed P8 or D7) or a Tern Link C7 (or similar) with a rear motor? I'm looking for more torque (not speed) and maybe the Q100H motor would be a candidate (is that possible to get installed in a 20" rim?).

Suggestions/warnings/encourgament for such a conversion welcome.

I previously asked about a Brompton conversion with the same motor, and got loads of advice - I may still go ahead with that, but looking at alternatives. Is a rear wheel conversion much trickier? (On Brompton I understand it's impossible?)

Chris

 

[Stalkingcat]

Ive converted a few Dahon Jetstreams. Rear sus is pretty important at speed otherwise be prepared for a bumpy ride!
Going to put one of them up on ebay within the next month to raise funds for a new builds.

 

[Stalkingcat]

btw, its the most perfectly balanced and fun ride ive had

 

[Deleted member 4366]

They have 135mm rear dropouts, so choose the motor you want. 328 rpm will give about 17mph on the road. Increasing voltage from 36v to 44v (12S lipos) will get you 22mph, and a 48v battery will give about 24 mph. You can run a 36v controller at 44v, but not 48v. 48v 15A controllers are not so common.
A Q100H takes a 7-speed freewheel gear set. 8-speed is possible.
A Q100C can take any gears, but not quite as powerful.

 

[Chris Maluszynski]

Sounds good. So all of them have the same dropouts? And how hard is it to install the motor in the wheel on your own? Or will BMS do that in a 20" rim that fits these bikes?

 

[Chris Maluszynski]

oh, and can I transfer the original freewheel of say a tern c7 or do I need to get one with the motor?

 

[Deleted member 4366]

The Dahons normally have free-hubs (cassette) rather than free-wheel gear-sets, so if you want to use your existing gears, you need a free-hub (cassette) motor.

BMSBattery sell the motor already installed in a wheel, but you should consider it loosely assembled rather than ready to use. You normally have to off-set (dish) the rim a bit to get it central, and the spokes are never tight enough. The Q100C is a little wider than normal, so a bit of a struggle to get in, but I managed OK on my Jetstream.I origionally had a standard Q100 in it. Some details here:
http://www.pedelecs.co.uk/forum/threads/electric2011-dahon-jetstream-p8.10584/page-4

missing photos here:
http://s451.photobucket.com/user/d8veh/library/Dahon?sort=3&page=2
http://s451.photobucket.com/user/d8veh/library/Dahon?sort=3&page=1

 

[Chris Maluszynski]

d8veh, thanks once again for all your insights.
Looking at your Dahon project it seems like it isn't exactly a cakewalk.
I wonder if this is something a newbie like me should be engaging in. But then again, you've go to try to learn something right?
What would you say is the hardest part?

I still don't understand what "dishing" the rim means, and am not quite getting which pictures in your Dahon build refer to this. BMS say that the Q100H is exactly the same as the Q100 in size. It's the H version with higher torque I am after. The highest rmp is 260 though…

And from what I can make out on their website it says you can have it mounted in 16-28" wheels, so maybe they could do a 20" that would fit a Dahon? Or no? Or are you suggesting that if you build the wheel yourself from the original Dahon rim it will be better than the one BMS will supply?

Sorry if I'm confusing things.

 

[Nealh]

Hello Chris,
Dishing is a term to describe centralising he wheel/rim once built/trued and fitted into the drops outs. If the trued wheel/rim is off center you the have to dish the wheel to get it central so for instance if the wheel is say 6mm off central andf over to the non drive side and needs to be move 3mm to the drive side you then have to loosen all the non drive spokes the same (say 1/2 turn) and then tighten all the drive side spokes the same 1/2 turn, this will gradually pull the rim over towards the center and towards the drive side. You continue to do this until you are happy that it is pretty well central, not forgetting once you are happy to check the wheel again for true.
If you have an old wheel then dismantle it and have a go at rebuilding it, a truly satisfying way of learning. Of course you will need a trueing stand which you can buy or build your own quite easliy or some folk use the bikes forks and cable ties or a ruler tied in place.

You tube a good source for how to and have a read of Sheldon Brown's wheel building free on the web.

 

[Deleted member 4366]

I never use a truing stand. I just put the wheel in the frame and use a couple of cable-ties to check it. The problem is that the motor's spoke flanges are not an equal distance from the center, and they become more off-centre as your gear cluster becomes wider.

The Q100H only makes more torque than the Q100 if you put more current through it. 18 amps is a good current for it if your battery and controller can give it. This is where it becomes difficult. 15A stuff is common. The next step is 20A, which might be a bit high for the motor. Also, you need a battery capable of giving 18A, and then you have to find a place and a way to mount it. 15A might be OK for you, depending on your weight. You can get more power by running a higher voltage. The speed of the motor goes in proportion to the voltage, so you get the same speed with a 201 rpm at 48v as a 260 rpm at 36v, but you get 30% more torque and power. If only BMSB sold a 48v 15A controller.

 

[Chris Maluszynski]

Ok, thanks, I think I understand trueing now!

Re motor/torque: I only talk about the Q100H because you suggested it in an earlier thread when I was talking about a Brompton conversion. I will be pulling a two-kid trailer with the bike, which is why torque is much more important than speed. I also however am thinking of a small Lipo-battery of 10-12S 5,8ah, so maybe I won't be able to power the the H version with that anyway? What is the advantage of the regular Q100 then? Weight?
The controller you suggested was the S06S I believe.

 

[Deleted member 4366]

You can run the Q100H with lipos if you want, but you have to understand that if you want a lot of torque, you have to use a lot of battery charge. At 15A, you will use up a 5aH lipo pack in about 15 minutes and at 20A, it'll be gone in 10 minutes. Obviously, you won't be using full power all the time, but on a hill, it'll draw the maximum.12S will give 20% more speed and torque than 10S.

There's no advantage of a Q100. It's more or less obsolete since the Q100H was offered with the same speeds.

 

[Chris Maluszynski]

Ah ok. So it's still the q100h that's the way to go. But if the controller sets the max power limit, is there any point in going with 12S over 10S batteries?

 

[Chris Maluszynski]

Or maybe I should put it simpler: If I'm interested in occasional high torque (up hills with the trailer), and range, but not speed, and would like a small battery - how should I optimize the setup?

 

[Deleted member 4366]

Small batteries are OK if you only want a little bit of assistance or you don't want to go far. The only way to be able to use one is to turn down the power and/or not go as far.They're great if you want to build a light-weight bike and provide most of the assistance yourself. The advantage of lipos is that it's very easy to get more capacity or voltage because they're modular. You only have to make a connection system of some sort, but you still need a place to put then on the bike.

With lipos, there's no BMS to cut them off when the voltage drops too far, so you have to keep watching them via a wattmeter or voltmeter. With a small pack, you'll be constantly worrying about how much further you can go - not very relaxing.

So, to answer your question about how to use a small, lightweight battery: Dump the trailer, go on a diet and practice pedalling hard.
.

 

[Chris Maluszynski]

Haha, aweseome. Or maybe get the kids to pedal instead!

c

 

[patpatbut]

Chris check this out

I know you are after this

http://www.diy.com/departments/mac-allister-36v-li-ion-40ah-battery-charger/188696_BQ.prd

It is on sale again!

Pat

 

[Stalkingcat]

Has anyone used these before? Whats the C rating, could be fun!

 

[Chris Maluszynski]

There's another thread about these elewhere. I was very eager, but now I wonder if Lipos aren't better after all…? D8veh what was the verdict?

 

[Chris Maluszynski]

Here's the other thread

http://www.pedelecs.co.uk/forum/threads/small-battery-bargain.19563/