The brass/metal gear cog arrived today along with the dual chain ring. I’d noticed during my research that several people had complained about the stock blue nylon cog (why on earth use plastic?) wearing out quickly, especially when they pushed the motor with larger chain rings and flashed software. With that in mind I decided the easiest thing to do was just replace it from the off. I’ve no wish for one of these to fail on me 25 miles from home so let’s just get it done.
A company in China (don’t think the company is related to TengShong) spotted an opportunity and quickly produced a cog which is reportedly made from brass and certainly looks and feels to be a quality piece. It’s $39 shipped direct from China and if you’re going to follow my lead you should add that to the total price of your motor when working out what the kit will cost you all in.
I’ve seen it written that installing one of these is a breeze. I think that’s probably pushing it. This is not a plug and play installation and requires that you partially disassemble the motor and disconnect the wires. If you’re confident working with tools it’s fiddly and will take an hour or two but it’s perfectly doable. If not, find a shop to do it for you. The process is basically:
- Remove the crank arms.
- Undo the 4 bolts holding the outer casing on the left side of the motor.
- Undo the two bolts holding the bracket in place.
- Remove the outer casing and remove the 4 screws holding the electric motor in place.
- Disconnect the 3 wires (blue, yellow, green) and the metal bridge that holds them in place.
- Disconnect the two small sets of wires to the right (two white connectors)
- Remove the motor.
- Remove the gear cog.
- On the right of the cog you’ll see a hole. The washer that just came loose goes over that hole. Grease the washer and stick it back over the hole so you don’t forget later.
- Grease the brass cog and pop it back in.
- Reverse engineer the above to put everything back together again.
- Be sure to grease the crank shafts either side before remounting the crank arms or they’ll be a xxxx to get off next time. If you’re upgrading an existing install as I was, use a rubber mallet to the pedal end of the crank arms to bang/vibrate the arms loose. They do tend to get very tight and require some force to get off, especially if you didn’t grease them when installing first time round!
Be careful that you disconnect the wires before trying to remove the motor. If you accidentally disconnect some of those wires from their solders or plugs you’ll have a another couple of hours work trying to reconnect them.
Be sure to go through all the pics above. I’ve taken step by step pics so if you forget how everything was supposed to look when trying to get it all back together you can just consult those pics. I’ve left the pics unedited and full-size so if you really need to zoom in on them, you can. I have also attached a video that I found helpful to check a couple of points during my own installation.
This seller got both the dual rings and the cog to me in about a week, so quicker than normal from China and shipping was reasonable.
Why do made a nylon gear?
Answer is: it’s a poor man motor overheating protection.
When the motor’s coils get hot, magnets can be damaged. To avoid it – nylon gear.
When temperature rises too much/too often (high gear ratios, high loads, etc) nylon gear/clutch in it smelts.
That’s why when you go with brass gear you choose to install temperature sensor and program your controller to reduce power when temperature rises and cut it off, when it’s too high.
I may be wrong, but that’s why the TDSZ2 is so cheap (by avoiding expensive parts and keeping things simple).