Newbie Advice Sought ! Dahon TR7 e-conversion

[keithy1959]

HI, I am considering converting my cobweb laden Dahon TR7 << edit 24 speed not 21 , 3 speed rear hub and 8 sprocket block >> folder into an e-bike. I am looking to do a 2x6mile commute 4 times a week, but I will also want to run a trailer for a few gardening tools now and again. My options are front hub or mid motor, and if I'm honest, pedal assist will probably be set to maximum, at least for a few months. I will be cycling through Swindon, which is quite well equipped with cycling routes. I'm not too bothered if I compromise the folding aspect of the bike.

I've come across Bafang, but I would greatly appreciate any pointers to other kits. I am confident with a bike spanner, but I would prefer a kit, rather than speccing individual components. I'd probably go for a rack mounted battery, rather than down tube.

Any help or sharing your experiences would be much appreciated.

Thanks in advance

Richard

 

[guerney]

Are you sure it's 21 speed? I can't see a "Dahon TR7 21 speed" anywhere. I converted my Dahon folder using a bbs01b, and because it's a mid drive and uses the existing 8 rear gears, it's capable of towing heavy gardening supplies up steep inclines. Make sure your bottom bracket is compatible - I wasn't aware of this forum when I converted, and took a wild gamble at the suitability of the bottom bracket (which was hell to take out), but the gamble paid off and I now have a fast powerful and light folding bike, which after programming takes no effort to ride. I just followed this video, except my battery is on the rear rack:

 

[Bonzo Banana]

You've stated front hub or mid-drive but you can get rear hubs with a freehub that would take your existing cassette. I had a google for the model and it came up with a speed TR model which has a chromoly based frame and forks which is ideal for a ebike conversion I would say.

The mid-drive motor option would mean you lose the ability to have a front derailleur and the wider range of gears but the motor will more than compensate for going to a 1x setup.

 

[keithy1959]

Just to explain the speed thing with apologies for the duff info - It's actually 24 speed - an 8 sprocket block onto a 3 speed internal rear hub, so no front derailleur, and hence the reluctance to do anything with the rear wheel.

 

[Bonzo Banana]

Just to explain the speed thing with apologies for the duff info - It's actually 24 speed - an 8 sprocket block onto a 3 speed internal rear hub, so no front derailleur, and hence the reluctance to do anything with the rear wheel.

Thats a very interesting design and with 3 speed hubs being strong it seems a very good solution to get a very wide gear range. I don't know how proprietary that setup is and how easy it is to get replacement parts i.e. for the freehub mechanism and how it fits to a 3 speed geared hub. Sounds interesting mechanically but maybe a few hard to replace components in there. Remember a mid-drive motor puts all its power through the same drivetrain as the cyclist and this could be as high as 4x as much with even a 250W motor. I.e. lets say the cyclist provides 30Nm of force on average and the motor is delivering 95Nm at the crank. You will be putting that drivetrain under a lot of additional stress and wear.

In contrast the front hub motor reduces wear on the drivetrain as you now have two powered wheels and the motor hub means far less wear on the drivetrain components. You can get up to 3x as long life out of a chain compared to a standard bike. However the front hub has its own set of issues, extra weight when steering, less weight on the front so less traction for the motor but that isn't really an issue on a low powered 250W hub motor. Also you have to sort out the cables and how they go past the hinge mechanism. If the battery is on a rear rack and the motor is at the front you need to be careful how the cables are run. It's not a big issue but you need to be careful how you do it.

Do you even need the 3 speed hub when you have all the power of the motor? Many ebikes are single gear for simplicity because the motor provides the additional power for hill climbing.

 

[Benjahmin]

I converted 2 folding bikes for my neighbour (he has a camper). I used a rear rack battery and a rear hub so that minimum wiring went across the fold. Worked well apart from a distinct tendency to wheelie. The short wheel base and the saddle position being almost over the rear wheel+ all that weight was a slightly tricky combo.
So I would say front hub and rack battery would give you a good weight spread. Front hubs can 'scrub' on loose or slimy surfaces but it's nothing a competant cyclist can't deal with. (My own bike is front hub 700c).
With battery (and controller) on rear rack there will be main power cables going across the fold. So consider that it may be better not to fold so as not to strain these cables.

If your interested, the whole conversion thread is here:

Advice for 20" hubs.

My neighbour has two 20" folders that he wants to convert. Not seen the bikes yet but he tells me they are 7 gears with caliper brakes and rear rack. First port of call was Woosh, but there site doesn't detail any 20" wheels. I realise the fold is going to be a big decider here. Looked at...

www.pedelecs.co.uk

 

[guerney]

The three gears that the OP would be left with after a mi-drive conversion with a BBSXX, really would not practically be enough IMHO. It was very important to me that my Dahon remained easily foldable - so it had to be a rear racked battery, and instead of cutting all of the electrical cables to fit the bike exactly, I left them slightly loose - looped and covered in the PC cable webbing shown in the video above. Like the man said after he leapt off a skyscraper "So far, so good!"

 

[keithy1959]

Thats a very interesting design and with 3 speed hubs being strong it seems a very good solution to get a very wide gear range. I don't know how proprietary that setup is and how easy it is to get replacement parts i.e. for the freehub mechanism and how it fits to a 3 speed geared hub. Sounds interesting mechanically but maybe a few hard to replace components in there. Remember a mid-drive motor puts all its power through the same drivetrain as the cyclist and this could be as high as 4x as much with even a 250W motor. I.e. lets say the cyclist provides 30Nm of force on average and the motor is delivering 95Nm at the crank. You will be putting that drivetrain under a lot of additional stress and wear.

In contrast the front hub motor reduces wear on the drivetrain as you now have two powered wheels and the motor hub means far less wear on the drivetrain components. You can get up to 3x as long life out of a chain compared to a standard bike. However the front hub has its own set of issues, extra weight when steering, less weight on the front so less traction for the motor but that isn't really an issue on a low powered 250W hub motor. Also you have to sort out the cables and how they go past the hinge mechanism. If the battery is on a rear rack and the motor is at the front you need to be careful how the cables are run. It's not a big issue but you need to be careful how you do it.

Do you even need the 3 speed hub when you have all the power of the motor? Many ebikes are single gear for simplicity because the motor provides the additional power for hill climbing.

Thanks for such a complete response. I was wondering about the action of driving an internal speed hub too, and being an american design of some 12 - 15 years, I don't want to take unneccessary risks with wearing parts out, and I dont want to start re-speccing the bike's drive train. I am starting to think more about a front hub option. I don't think heavier steering will be a problem - the existing wheel has a hub dynamo and as about 75% of the proposed daily commute will be on cycle tracks, I doubt traction is likely to be an issue. Swindon is reasonably flat, thankfully.

The bike design is a folding tourer, and has front pannier racks, so I am thinking these might be a good solution for the battery, and I won't have to worry too much about cable routing across the folding mechanism.

I may find a front hub a compromise if and when I attach a trailer to it, but again, it will be for reasonably short journeys only.

Are there any hub motors to recommend or avoid ?

Thanks again

Richard

 

[keithy1959]

I converted 2 folding bikes for my neighbour (he has a camper). I used a rear rack battery and a rear hub so that minimum wiring went across the fold. Worked well apart from a distinct tendency to wheelie. The short wheel base and the saddle position being almost over the rear wheel+ all that weight was a slightly tricky combo.
So I would say front hub and rack battery would give you a good weight spread. Front hubs can 'scrub' on loose or slimy surfaces but it's nothing a competant cyclist can't deal with. (My own bike is front hub 700c).
With battery (and controller) on rear rack there will be main power cables going across the fold. So consider that it may be better not to fold so as not to strain these cables.

If your interested, the whole conversion thread is here:

Advice for 20" hubs.

My neighbour has two 20" folders that he wants to convert. Not seen the bikes yet but he tells me they are 7 gears with caliper brakes and rear rack. First port of call was Woosh, but there site doesn't detail any 20" wheels. I realise the fold is going to be a big decider here. Looked at...

www.pedelecs.co.uk

Thanks, I'll read that thread now. The ride on the Dahon is very much like a tourer and with my bulk leaning slightly forwards, I doubt wheelies will be an option !! I am drawn to Front hub solution, and to start with the battery on the front panniers. I bought a folder when I commuted by car and bike, but I'm not to concerned about folding it now.

Thanks and Regatrds

Richard

 

[keithy1959]

The three gears that the OP would be left with after a mi-drive conversion with a BBSXX, really would not practically be enough IMHO. It was very important to me that my Dahon remained easily foldable - so it had to be a rear racked battery, and instead of cutting all of the electrical cables to fit the bike exactly, I left them slightly loose - looped and covered in the PC cable webbing shown in the video above. Like the man said after he leapt off a skyscraper "So far, so good!"

All the gearing is on the rear wheel - its a combined 3 speed hub and 8 speed rear deraillleur, but I'm looking at the front hub as a more sensible option for me following responses from this thread. As stated above, I have front panneir racks, so I think I'll start there, and if it doesnt work, move the battery to the back !

Richard

 

[guerney]

All the gearing is on the rear wheel - its a combined 3 speed hub and 8 speed rear deraillleur, but I'm looking at the front hub as a more sensible option for me following responses from this thread. As stated above, I have front panneir racks, so I think I'll start there, and if it doesnt work, move the battery to the back !

Richard

I think that older Dahons especially, are excellent bikes. You might already be aware of CH White for spare Dahon parts that nobody else seems to have - the owner really knows his stuff. Among other hard to find things - the new wheels I bought from them a couple of months ago, I really couldn't have sourced anywhere else in the UK:

C H WHITE & SON

We are a UK cycle shop offering a wide range of bikes, including folding bikes, electric folding bikes and e-bikes. Discover our quality selection and expert service for all your cycling needs.

foldingbike.biz

I wanted to fit 1.75 inch or wider tyres, which the existing Kinetix wheels couldn't accommodate, plus the rims were worn anyway. So they found me a double walled pair intended for Tern, which work wonderfully (after trueing, but only just a bit).

 

[keithy1959]

I think that older Dahons especially, are excellent bikes. You might already be aware of CH White for spare Dahon parts that nobody else seems to have - the owner really knows his stuff. Among other hard to find things - the new wheels I bought from them a couple of months ago, I really couldn't have sourced anywhere else in the UK:

C H WHITE & SON

We are a UK cycle shop offering a wide range of bikes, including folding bikes, electric folding bikes and e-bikes. Discover our quality selection and expert service for all your cycling needs.

foldingbike.biz

I wanted to fit 1.75 inch or wider tyres, which the existing Kinetix wheels couldn't accommodate, plus the rims were worn anyway. So they found me a double walled pair intended for Tern, which work wonderfully (after trueing, but only just a bit).

Totally agree about CH Whites - that's where I bought mine