Tern Link D8 Conversion

[mrail1982]

My Tern Link D8 folder, which I have used regularly and enjoyably for short-distance commuting and leisure purposes since purchase last summer, seems to be an ideal candidate for my first conversion project. My priorities for the project are threefold - it should be reasonably lightweight for a small e-bike, adding no more than 5 kg to the 12 kg of the standard D8; it needs strong and reliable hill-climbing performance to cope with the demanding moorland terrain here in East Lancashire; and finally it should not compromise the functionality and compactness of the folding mechanism.

My preference would be for a front-mounted hub motor, partly because of the ease of fitment (and removal if necessary) - the D8 already has steel forks with about 78 mm clearance between dropouts. A light, compact 250W motor kit for a 20 inch wheel (at 328 rpm) should be powerful enough for my purposes, such as the Q85:

http://www.bmsbattery.com/ebike-kits/421-250w350w-q-85100sx-motor-e-bike-kit.html

I haven`t yet decided on the battery placement, but the two most straightforward options are to use either the water bottle mounts forward of the main frame hinge or the Biologic rear carrier rack.

Any suggestions from members experienced in the arts of converting small folding bikes would be much appreciated, and it would be good to hear from fellow Tern enthusiasts with similar plans, too.
Kind regards,

mrail1982

 

[John Galvin]

Just about to start conversion on a P9. Great bike as standard.
I'm using a front hub motor and a front mounted frog battery.
I'll report on progress as hopefully I'll get a chance to start this week.

 

[Deleted member 4366]

Q85 is not very powerful. It's better than nothing, but a Q100 rear motor is much better.

 

[mrail1982]

Just about to start conversion on a P9. Great bike as standard.
I'm using a front hub motor and a front mounted frog battery.
I'll report on progress as hopefully I'll get a chance to start this week.

Many thanks for your reply. I did notice from the other threads that you were converting your P9 and I`m very interested in how you get on with the project.
Could you say a little more about your choice of hub motor and controller? Like you, I have been impressed with my Tern - the standard D8 is surprisingly fast for a 20 inch wheeled bike, lightweight, folds easily and quickly, has a wide range of gears for decent unassisted hill-climbing, and is well-specified for the price, which is significantly less than a certain well-known British brand of folders! I chose the D8 in particular because its steel forks and rear carrier rack made it a suitable donor bike for conversion.
All the best for now.

 

[John Galvin]

I looked at the British bike too and have to say I liked it, especially the neater fold. I'm in London for a few days and I see them all around.
I won't be hopping onto trains every day so for me, it didn't seem worth the extra money.
I'm extremely impressed with the P9 and was even debating whether to go ahead but the first two times I had it down my LBS, customers asked on each occasion was there a motor in it. I took it as a sign.
I went with Ciclotek, a Spanish firm, as they had a good choice of options and responded well to queries. I asked a question of one of the Chinese suppliers and they responded accurately to a completely different question. These things matter, especially for your first ebike.
I forget what revs the motor is supposed to put out, but early in the process I worked it out and it comes bang on 25 km/h.
I was going to go initially with a bottle battery, but a local e-dealer warned me that he'd seen a few of them shake themselves to bits. I was then going to mount a rectangular battery on top of the frame, but I think it would look silly there.
The frog battery has a compartment for the controller, making for a neat installation and I decided to mount it at the front as it means only the PAS wiring has to cross the fold. I didn't want to put it on the seatpost given that it's a folder.
Ciclotek have just introduced a more advanced controller, which is now sine wave so it should be quieter.
Price wise, by the time you add carriage, VAT and duty to the Chinese supplier, there's probably only €50-€100 between them and for a bit of peace of mind, I reckon that's worth it. With more experience, I would have no problem going the Chinese route, but the longer delivery time made my mind up. I got my kit in three working days so I'll be able to start work straight away.
A friend is very good with his hands so he's making up a simple bracket from box iron that we'll screw to the luggage truss treads. I'll bolt the frog to this using the existing bolts that hold the post clamp together.

I'll let ye all know how it goes. If I've missed anything here, ask away.

 

[John Galvin]

Well, I haven't seen it in the flesh yet, but here's a pic of the bracket attached to the shell of the frog battery.
I'll see how it looks on the bike tomorrow and if it works out, I'll get whatever bolts I need and a lick of paint and hopefully I'll have the battery mounted by the weekend.
I reckon that'll be the trickiest part of the conversion so hopefully all should be good.

 

[John Galvin]

Just to update on my conversion of a Tern Link P9. I'm banjaxed at the moment because my supplier sent me the wrong charger so I can't wire everything up.
The attached pic shows the motor and battery mounted on the front of the bike.
The bracket has been successful and the frog is mounted very solidly and securely. The only slight issue is that it doesn't turn with the handlebars which just takes a little getting used to.
I've tried the bike a few times with the battery mounted and it still rides well and easily even with no power. It's a little nose heavy when carrying but not too bad.
The other day, I gave it the full beans starting on a hill with no battery mounted and the front wheel bunny-hopped so maybe a bit of weight over the front won't go astray.
Hopefully I'll get the charger in the next few days and start wiring up - and yes, the wire going into the hub is pointing down as it should be.

Thanks for all the help and advice so far.

 

[Deleted member 4366]

Sorry to hear of your problem. What was wrong with the charger? Do you have to send it back? How did the supplier react when you told them about the problem?

Are there any markings on the motor?

 

[John Galvin]

Just the wrong plug - it wouldn't fit into the battery. I sent them a pic and within ten minutes they replied that they'd send me the correct one. Don't know yet if they want this one back or not. I'll sort that later.
No significant markings on the motor. Ciclotek is etched on the side but they've obviously put that there themselves. There's just a 36v 20" sticker on it and a serial -type number etched on as well. Does MX03 mean anything to you?

 

[Deleted member 4366]

Yes, MX03 is a MXUS MX03. It's similar to the Cyclotricity motor, which is the later and slightly more efficient MX07 (IIRC), which also takes a disc brake. They're nice motors. There's two versions of each. They put stronger magnets and higher grade wire in the European ones compared with the ones for the Chinese market, which gives a bit more torque. Which one you get depends on whether Ciclotek bought them direct from MXUS or from a Chinese agent.

 

[John Galvin]

That's interesting, thanks. Any way to tell from the full number stamped on it? One bit is a bit smudged but I'd be able to make it out with a brighter light.

 

[Deleted member 4366]

Not as far as I know.