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Building a lightweight ebike with the Tongsheng TSDZ2

E-bikes with mid-drive motors require special frames and those frames are never particularly lightweight. However, any standard lightweight frame can be used for the Tongsheng TSDZ2 motor. Unfortunately, the Tongsheng TSDZ2 is very heavy, if the weight is reduced as described here a very lightweight ebike can be built.

Tongsheng TSDZ2 weight reduction from 3.8kg to 2.6kg

A disadvantage of the Tongsheng TSDZ2 is that it is not built lightweight at all, it weighs 3.8kg (without crank arms, cabling and display). This is much too heavy for making a lightweight ebike. For my Maxun One solar bike, I really need a lightweight mid-drive motor under 3kg. For an example of a such a mid-drive motor: the Shimano Steps E8000 weighs 2.9kg, it's one of the lightest of its kind.

I found out however that the weight of the Tongsheng TSDZ2 can be drastically reduced. To give an example of the unnecessary weight of some parts:

  • The motor support is made of a solid aluminum block. This can also be made of plastic or it can perhaps be omitted entirely.
  • The chainring guard is also made of aluminum. This part can simply be omitted or replaced with a lightweight plastic version. 

To investigate which parts can be reduced in weight, I have taken the motor apart and measured the weight of each part:

Weight reduction Tongsheng TSDZ2
Weight reduction Tongsheng TSDZ2
Tongsheng TSDZ2 holder weight 204g
Tongsheng TSDZ2 holder weight 204g

Weight reduction Tongsheng TSDZ2
Weight reduction Tongsheng TSDZ2
Tongsheng TSDZ2 motor parts weight
Tongsheng TSDZ2 motor parts weight

Tongsheng TSDZ2 small parts
Tongsheng TSDZ2 small parts
Tongsheng TSDZ2 torque sensor crankshaft crank arm
Tongsheng TSDZ2 torque sensor crankshaft crank arm

Tongsheng TSDZ2 weight gearwheel motor controller
Tongsheng TSDZ2 weight gearwheel motor controller
Tongsheng VLCD5 display weight
Tongsheng VLCD5 display weight

These parts can be easily reduced in weight

Not all parts can be reduced in weight at reasonable costs, I suggest to start with the following parts:

  • Main gear 581g > 200g. A lot of weight can be saved here by making the body of aluminum and using a stainless steel ring gear.
  • Main housing 729g > 300g. A lot of weight can be saved here by replacing the parts that do not need to be strong with plastic.
  • Motor housing 146g > 20g. Omit this part and using a thin plastic cap.
  • Motor support parts 204g > 20g. Omit these parts and use another construction of plastic.
  • Chainring guard 80g > 0g. This part can easily be omitted.

We can save about 1.2kg this way which reduces the motor weight to 2.6kg. The Tongsheng TSDZ2 is then even lighter in weight than the Shimano Steps E8000.

Further weight reductions

  • If you only use throttle control only you can omit the torque sensor of 265g.
  • Replace the crank arms of both 442g with lightweight ones.

Do you have any comments about the website? Please let me know.