Fast forward a week of self-isolation with three small children and, after scraps of time building it up in the evenings and a solid two hours yesterday, I finally took the Sutra on a lap round the block with the assist running smoothly1and, admittedly, only a single brake, and that controlled by the wrong lever. I live in the sticks; it was a considered risk….
Now feels like a good time to talk through the build.
How hard was it?
I was planning on making this a full “how to install the Tongsheng TSDZ2 motor” guide, but it’s not necessary. If you’re planning on retrofitting the TSDZ2 to a bike, the actual electrical install will be easier than a lot of other stuff you need to consider, and if you’re comfortable doing that, you’ll be fine. For example:
- If you’re happy taking off your existing bottom bracket, installing the TSDZ2 is the same process in reverse (and easier, given nothing in the new motor is seized in place…).
- Because the new motor sits under the bottom bracket, you’ll need to reroute any existing gear or brake cables that run under there (which will probably involve full-length housing for both, because you won’t be able to use the frame cable stops to maintain tension). If you can do that, keeping the electrical cabling tidy is a doddle2although if you have an aversion to cable ties, this project may not be for you. Seriously. Buy a big bag..
- If you can follow some basic Ikea/Lego instructions, you’ll be able to follow the Woosh Bikes instructions for connecting up the battery, motor, screen, remote, and speed sensor. Everything has the relevant connectors pre-installed—follow the words, look at the pictures, plug stuff together.
There is a single step that would be unusual for the moderately competent home cycle mechanic, and that’s drilling holes in your downtube in order to fit the additional “rivnuts” to secure the battery. Given I regard myself as somewhat-less-than-moderately competent, I really didn’t fancy doing that (although by all accounts it’s straightforward if you have a sharp drill bit). Therefore I cheated, and used the delightfully named Zefal Gizmo Universal3best said with a strong French accent.
Two packs give you four mounting points secured by robust cable ties. Use three for the battery mount, and a final one to brace up the bottom of the battery mount (which is a little flexy when the battery isn’t installed, so some extra support makes it easier to slide the battery in).
A final point before I cover some details; if you haven’t gone with Woosh’s kit, you’ll have to install matching connectors between the battery and motor, and you won’t have their instructions (or help at the end of a phone/email). You’ll probably be fine, but it does make life easier.
Some pointers if you are using the Woosh kit
Excellent as the Woosh kit is, as with anything, there’s a couple of steps where the author’s way of describing something doesn’t quite match up with your mental view of the world. These are the steps that I had to think about a bit.
The first isn’t related to Woosh at all, but still. Having slid the motor through the bottom bracket shell, there’s a plate you secure over the far end, which is itself secured by two bolts into the motor itself, and then a final big nut snug against the bottom bracket shell. Something in there was slightly out of tolerance, and I had to add the skinniest washer I could find to get all three to tighten down. See delicate illustration below.
Point two. The instructions say something along the lines of “plug the yellow socket from the motor into the speed sensor cable”. The latest model of the speed sensor cable has a y-shaped connector, both bits look identical. As far as I can tell, it doesn’t matter which one you pick (the other is apparently used to power any rear lights you might fancy adding in). This does leave you with an open socket that I ended up covering with electrical tape; it’d be nice if the kit came with a rubber cap or something.
Finally, the connections between the battery and the motor could be better4actually, a bonus pro-tip. When you connect the cables from the battery mount to the motor, do it without the battery in the mount. Otherwise you get a big spark as you plug them together, which can be alarming to the low-of-confidence (including myself). Based on my limited electric knowledge, it’s better if the connectors are not directly alongside each other but staggered – it reduces the chance of them shorting against each other, and makes it a damn sight easier to get heat shrink over them. Furthermore, the bullet connectors Woosh have installed have chunky plastic shielding, so much so that I couldn’t actually get the supplied heat shrink over the top.
In the end I used lashings of electrical tape, but I’m not convinced that is the most waterproof of solutions. I suspect some kind of junction box might be best; it’s certainly something I’ll look into.
Anyway, that’s it. Nothing really significant.
Photos of the build
I don’t want to comment much on the motor performance until I’ve got the brakes sorted5I bought a “pre-bled and ready to use” kit, which would be true if I was in Europe and was used to the front brake being on my left hand. Although I was tempted to just live with it, Deore hydraulics are really very good at stopping, and I felt that not switching them over would inevitable result in Amusement down the road when I grabbed a handful of what my muscle memory was convinced was rear brake, and launched myself over the handlebars. I’m waiting on new olives to arrive before I swap the cables round. and I take it up a hill (but from that quick lap of the block it’s remarkably quiet, and the assist is smooth yet powerful). Therefore I’ll finish with a couple of other photos from the build so far.
Firstly. Bottom brackets that have been in for ten years are not easy to get out, even with the old “seatpost lever” trick:
However, if you happen to have a friend who maintains an old land rover, an overnight soaking in WD40 followed by a short blast with an impact driver sorts the problem.
The anti-torque bar from the motor braces just behind the bottom bracket, above the chainstays. This is one area to check for clearance on your frame. It also means you can’t use a centre-mount kickstand:
The lock on the battery drives this metal plug down into a matching hole in the battery mount. I had to slightly expand this with a circular file, as the plug was catching on the top edge:
Here’s a photo from behind the motor looking forwards, showing the cables exiting from the drive-side. I then routed them all up into the handy gap in front of the chainstay bridge:
Connecting the battery and motor is the horlicks-of-a-job I did with electrical tape. At some point I’ll do this properly, maybe with a weatherproof junction box if I can find one small enough.
You can tell from the photo above there’s a good number of cables to control. After a bit of playing around and many snipped cable ties, I felt the best option was to snug the electrical and rear derailleur cables up into the battery mounts, and leave the cable guides under the downtube for the hydraulic hose to the rear brake (not yet installed)
Talking of the rear derailleur, here’s the routing I went for from the back to the crank:
Whilst the back was on the stand, I took the opportunity to re-tension6ie loosen the mount, and tighten it again a little further down the downtube. the stabiliser for the front wheel. These are highly recommended if you have a front rack or a kickstand – they stop the front wheel flopping about when you’re off the bike:
And finally, here’s a picture from the saddle during that inaugural lap. Really liking the Surly Moloko bars—so much space!
Hopefully by next weekend the brakes will be sorted and I’ll have been able to fully test it out on a run to the shops. Stay tuned…