Could some kindly take some measurements of a tongsheng and bafang mid drive?

[mr_ed]

I’m building a mid drive ebike as a project with my 14 year old son. I’m concerned that the rear chain stays are quite wide on our frame and may foul on the outer gear housing. I’ve looked at the engineering drawings for tongsheng and bafang units but they don’t show all the measurements and radiuses I’m interested in. This picture is more helpful for the bafang unit. What I am most interested in is the 'r' measurements and the distance (vertical in this picture) from the outer point to the bottom bracket mounting face. So for r1 (46) it’d be zero mm.

I’d be very grateful if anyone could take some measurements and do a sketch or take a photo with a ruler pressed up against the bb thru-shaft and measure from it to the contact points. Both for the Tongsheng and the Bafang.

Or does anyone have a dead unit/casing I could buy for beer money, or anyone local to Southampton/Salisbury that has a unit I could slot into our frame?

many thanks!

 

[matthewslack]

I’m building a mid drive ebike as a project with my 14 year old son. I’m concerned that the rear chain stays are quite wide on our frame and may foul on the outer gear housing. I’ve looked at the engineering drawings for tongsheng and bafang units but they don’t show all the measurements and radiuses I’m interested in. This picture is more helpful for the bafang unit. What I am most interested in is the 'r' measurements and the distance (vertical in this picture) from the outer point to the bottom bracket mounting face. So for r1 (46) it’d be zero mm.

I’d be very grateful if anyone could take some measurements and do a sketch or take a photo with a ruler pressed up against the bb thru-shaft and measure from it to the contact points. Both for the Tongsheng and the Bafang.

Or does anyone have a dead unit/casing I could buy for beer money, or anyone local to Southampton/Salisbury that has a unit I could slot into our frame?

many thanks!

View attachment 45731

I have a Tsdz2 in a box, if no joy before this evening, will put up a pic after work.

Scotland, not Southampton!

 

[matthewslack]

I’m building a mid drive ebike as a project with my 14 year old son. I’m concerned that the rear chain stays are quite wide on our frame and may foul on the outer gear housing. I’ve looked at the engineering drawings for tongsheng and bafang units but they don’t show all the measurements and radiuses I’m interested in. This picture is more helpful for the bafang unit. What I am most interested in is the 'r' measurements and the distance (vertical in this picture) from the outer point to the bottom bracket mounting face. So for r1 (46) it’d be zero mm.

I’d be very grateful if anyone could take some measurements and do a sketch or take a photo with a ruler pressed up against the bb thru-shaft and measure from it to the contact points. Both for the Tongsheng and the Bafang.

Or does anyone have a dead unit/casing I could buy for beer money, or anyone local to Southampton/Salisbury that has a unit I could slot into our frame?

many thanks!

View attachment 45731

The critical point on the TSDZ2 is the chamfer on the inside of the main gear housing. I've shown distances from the outside of the axle tube in the pic: add 16.5mm for radii (half of 33mm).

So the chamfer starts 53.5mm radius from the axle centre, and as well as I can measure it is 15 degrees angle - about the same as the chain stay angle in your picture.

Photos don't show it well as the angles are distorted by the camera being closeup!

I think it will fit, but just as in your pic, the axle might not be exactly symmetrical: i.e. a few mm off centre might be needed to have clearance on the drive side. There seems to be some extra length in the axle tube to allow for that.

Any more questions, let me know. The box is out now!

 

[mr_ed]

View attachment 45740

The critical point on the TSDZ2 is the chamfer on the inside of the main gear housing. I've shown distances from the outside of the axle tube in the pic: add 16.5mm for radii (half of 33mm).

So the chamfer starts 53.5mm radius from the axle centre, and as well as I can measure it is 15 degrees angle - about the same as the chain stay angle in your picture.

Photos don't show it well as the angles are distorted by the camera being closeup!

I think it will fit, but just as in your pic, the axle might not be exactly symmetrical: i.e. a few mm off centre might be needed to have clearance on the drive side. There seems to be some extra length in the axle tube to allow for that.

Any more questions, let me know. The box is out now!

Thank you very much! I will get that drawn up and cut out of cardboard!

One more question, what is the length of the cylinder that goes through the bottom bracket both with and without the threaded portion? And (in other words) what is the maximum thickness spacer you could put between the gear housing and bottom bracket face and still be able to get the retaining nut fully threaded on the other side.

 

[mr_ed]

Ive printed the engineering drawings of both the bafang and the tongsheng and scaled them until the marked up measurements match. What is annoying is the tongsheng drawing doesn’t seem to be accurate, in particular the critical chamfer to the gear housing is not shown and is instead a simple radius. That is critical to me!

Here is the bafang top and tongsheng below:



With them overlayed, bafang on top, you can see the tongsheng is about 8mm wider in this critical area… according to the diagram at least.



Bafang on the bike



Tongsheng on the bike

 

[mr_ed]

Hmmm, doing a bit more googling for pictures of the tongsheng I think they’ve changed the design and older ones matched the drawing. Can’t find any drawings for the newer style so will modify one using Matthews measurements.

 

[matthewslack]

Hmmm, doing a bit more googling for pictures of the tongsheng I think they’ve changed the design and older ones matched the drawing. Can’t find any drawings for the newer style so will modify one using Matthews measurements.

Max length of axle tube is 82mm, excluding the recess where the bottom bracket end would sit, so about 84mm including that. The clamping nut is 6mm thick, so available length looks like 76mm without recess, 78mm with.

I'll put up a pic of my unit showing the chamber later on today.

Threaded length is 20mm.

 

[matthewslack]

Max length of axle tube is 82mm, excluding the recess where the bottom bracket end would sit, so about 84mm including that. The clamping nut is 6mm thick, so available length looks like 76mm without recess, 78mm with.

I'll put up a pic of my unit showing the chamber later on today.

Threaded length is 20mm.

Chamfer, not chamber in my previous post.

Hope that helps.

 

[mr_ed]

any chance you could measure the two blue measurements marked above? Thank you!

 

[matthewslack]

View attachment 45765

any chance you could measure the two blue measurements marked above? Thank you!

It's a 42T chainwheel, 1/2 inch chain, and the teeth are a standard depth, so about 10mm. Diameter where the chain centres are is therefore 170mm, the outer blue mark, and overall diameter is 180mm give or take a mm or two. Couldn't find the tape measure this morning!

The chain guard sits far enough out I don't think it could be a problem.

Some of the little lines on my drawing are just bad drawing rather than reality!

 

[mr_ed]

It's a 42T chainwheel, 1/2 inch chain, and the teeth are a standard depth, so about 10mm. Diameter where the chain centres are is therefore 170mm, the outer blue mark, and overall diameter is 180mm give or take a mm or two. Couldn't find the tape measure this morning!

The chain guard sits far enough out I don't think it could be a problem.

Some of the little lines on my drawing are just bad drawing rather than reality!

Sorry for the confusion, they're not arrows pointing at the chainwheel, the measurements I'm after are the thicknesses of the motor gear housing (directly above the blue lines), so the thickness with and without the chamfer. That gives me all I need to fully draw it to scale. Thank you for your help!

 

[matthewslack]

Sorry for the confusion, they're not arrows pointing at the chainwheel, the measurements I'm after are the thicknesses of the motor gear housing (directly above the blue lines), so the thickness with and without the chamfer. That gives me all I need to fully draw it to scale. Thank you for your help!

Ok, after work.

Does the length of the axle tube look ok for your frame?

 

[wheeliepete]

You may already be aware, but both those drive units will fit upto a 73mm bottom brackets, so you can fit upto a 5mm spacer on the drive side and still get the lock nut to fit. You may run into chainline issues by doing this as you frame looks like it was designed to run a small, single chainwheel close to the chainstay, hence the big offset on the BB, a common problem with alot of modern bikes. this can be counteredon the Bafang BBS with an offset chainwheel, but I'm not sure the same is available for the Tongsheng unit.

 

[peter.c]

The tsdz2 will not take a bling ring, so if the chain line is spaced out it can cause problems my personal experience with a bbs i can get the chain sorted, but the with tsdz the pedal arms also often hit the chain stay on the non drive side once you fit spacers

 

[matthewslack]

Sorry for the confusion, they're not arrows pointing at the chainwheel, the measurements I'm after are the thicknesses of the motor gear housing (directly above the blue lines), so the thickness with and without the chamfer. That gives me all I need to fully draw it to scale. Thank you for your help!

Different colour pen for new measurements.

I also noticed the fishing of the chainwheel, which puts it as close to the motor as possible without overlapping.

Edit: that should read dishing.

 

[mr_ed]

Thanks guys, has taken me ages to reply because no electricity yesterday and still no broadband today! Anyway gave me plenty of time to make a cardboard template based on Matthew’s measurements.



Its a 73mm bottom bracket and as pictured above there wouldn’t be enough thread to get the nut on the other side. I think I saw you can get a 100mm version of the tdsz but the chain line would be poor. I think I read tdsz2 takes a standard sprocket so a dished version may be sourcable. Alternatively, I’ve thought about modifying the frame; the chainstay just needs cutting at the bottom bracket end, bending over 6mm or so and rewelding. It’s a 6061-T6 heat treated frame so not straightforward. I’ve got the number of a local coded welder so I might call him up to see what it says. May not be economically sensible either as the frame was only £125 new.

I can see this being a more common problem with modern frames, designed for a 1x10 - 1x13 cassette, 148mm rear axle and silly wide tyres. I know a revised tdsz is due soon but don’t know if it will be any different in dimensions.

Anyway, the bafang would fit with only a small spacer as pictured above and gives a better chain line too so much as I prefer the tdsz characteristics that might be the more sensible option.

 

[peter.c]

The 100/120 mm version of the tsdz2 has a design fault in the shaft and will snap off at the circlip see the long thread on endless sphere ,
The standard non drive pedal arm will be very close to the chain stay with the 73mm version and if you fit spacers to the drive side it will touch
Recently converted a voodoo wazo with plus size tyres 27.5 x 3.0 took a machine shop and spacers and several dry fits and a non standard pedal arm the tsdz2 would not fit

 

[mr_ed]

Found a nice site lastnight that has printable templates for the bafang units. They have a video on chainstay intrusion and the example frame is almost identical to ours.

Their solution is to fit the 1000w bbshd. I’ve printed the template and sure enough it does fit better than the bbs02 or the tongsheng. Suspect it is too much power, but can probably be limited.

Bafang USA fitting wizard.

The taper of the bbshd gear casing seems a perfect match for our chainstay and it has more thread the other side than the bbs02.

Their templates show all the gear options and the rightmost one is a 42T bling ring which would be ok for us. It’ll need limiting otherwise it’ll do 50mph.

 

[wheeliepete]

Found a nice site lastnight that has printable templates for the bafang units. They have a video on chainstay intrusion and the example frame is almost identical to ours.

Their solution is to fit the 1000w bbshd. I’ve printed the template and sure enough it does fit better than the bbs02 or the tongsheng. Suspect it is too much power, but can probably be limited.

Bafang USA fitting wizard.

The taper of the bbshd gear casing seems a perfect match for our chainstay and it has more thread the other side than the bbs02.

Their templates show all the gear options and the rightmost one is a 42T bling ring which would be ok for us. It’ll need limiting otherwise it’ll do 50mph.

View attachment 45801

Looks to be a very nice fit, chainline may still be a bit off in lower gears, but with the HD you are unlikely to need the first 2 unless you are climbing vertically. The Bling Rings are well made, but expensive, if you look on Aliexpress there are cheaper copies witch I think have the same offset.

38.5￡ |Sprocket Wheel Crank | Chain Wheel Integral | Bbshd Chainring 42t | Bbshd Chain Wheel - New - Aliexpress

Smarter Shopping, Better Living! Aliexpress.com

www.aliexpress.com

 

[mr_ed]

This arrived today:


This is how it looks:




It would need about 6mm of spacer on the chain side, which means not enough thread on the clamp nut side. I could shave 5mm off the bottom bracket face to improve that.

I think the options are:

A. Shave a mm or two off the chainstay and a mm off the motor casing and a few mm off the bottom bracket opposite face.

B. Cut 5mm off the chainstay and weld a reenforcement on the back of it.

C. Bafang HD 1000w

I’m going to investigate what the chainline would be with A. Can you get an offset/dished chain ring for the tongsheng? 40 teeth or less.

The cardboard model from Matthews measurements was pretty accurate.