Alternative mounting of mid drive motor

[Simon Knight]

I have a Tongsheng middrive motor that I have had to remove from my recumbent trike owing to problems with my knees which I attribute to the wider spacing of the pedals and the offset cranks.

I am considering trying to mount the motor on a custom, yet to be built, mounting plate which will be fastened to the trikes boom. I would then fit a smaller chain ring of the same size as the small ring in the original triple chain set onto the motor and connect the two using a short chain.

I think that as long as the motor is securely mounted and the chain adjusted so there is no slack the motor should be able to provide drive. However, I'm sure its been tried before and I wonder how it worked out.

best wishes

S

 

[saneagle]

I have a Tongsheng middrive motor that I have had to remove from my recumbent trike owing to problems with my knees which I attribute to the wider spacing of the pedals and the offset cranks.

I am considering trying to mount the motor on a custom, yet to be built, mounting plate which will be fastened to the trikes boom. I would then fit a smaller chain ring of the same size as the small ring in the original triple chain set onto the motor and connect the two using a short chain.

I think that as long as the motor is securely mounted and the chain adjusted so there is no slack the motor should be able to provide drive. However, I'm sure its been tried before and I wonder how it worked out.

best wishes

S

Won't the chainwheel on the motor only freewheel in that case? How will it put force on the pedal shaft to operate the torque sensor? It might work if you were able to fit a normal chainwheel to the square taper if there's enough room. You might need to reverse your main crank and fit the cogs on the left side, but it still might not work the torque sensor properly.

If it were my bike. I'd fit a hub-motor on a bracket somewhere. It should be a lot simpler as the motor works as the secondary shaft. Also you could use a chain-drive like a Cyclone.

Here's what I did to use a hub-motor to drive the crank. sory about the quality. that was 2011. I made a thread about how I constructed it, but I can't find it with any search - basically just a bracket with two drop-outs clammped to the frame and a tensioner. I fitted the sprocket to the disc side because Iwanted it to drive a left side crank, but in your case an ordinary freewheel would work on the right side:

 

[Bikes4two]

An interesting idea Simon but as @saneagle says, without a 'turning force' on the TSDZ2 pedal shaft to produce a torque signal, I can't see the motor activating?

And the TSDZ2 chainwheel is not connected directly to the pedal shaft but via a sprag clutch thus turning the chainwheel has no effect on the pedal shaft.

Have a look as this TSDZ2 motor animation on YT to help you figure it out (link)

 

[Sturmey]

It might work fitting a regular right hand chainwheel crank (but with the unused length of crank ground off), leaving the chainwheel and taper intact so it can be mounted on the tsdz tapered crank. You would then have two chainrings on the tsdz, the inner chainring mounted as normal on the spider with 5 allen fasteners and the outer mounted on the tapered crank.
However, this may push the outer chainline (going back to other pedal crank) very far out so this is something to take into account.

 

[Simon Knight]

Thanks for your comments. You are all correct I had not appreciated that the motor chain wheel does not trigger the torque sensor and having looked at the trike I don't think there is enough room especially if I wish to retain the water bottle.

I will probably be better served just to buy a rear hub motor in a twenty inch wheel.

 

[Bikes4two]

Hi @Simon Knight - going back to your original post

I have a Tongsheng middrive motor that I have had to remove from my recumbent trike owing to problems with my knees which I attribute to the wider spacing of the pedals and the offset cranks.

I'm lucky enough to not have the type of knee problems that you have, but out of curiosity I'm wondering how much difference in Q factor is needed from that of the TSDZ2 to what ever the original trike chainset was, to cause you knee issues? Have you measured up the offsets between the two systems?

When I installed my first TSDZ2 I read about the crank offset issue and bought a pair of cranks used on the Bafang mid drive as they were offset less, but I only did that out of idle curiosity rather than a specific need.

Since then I've a second bike/TSDZ2 fit and use the standard TSDZ2 cranks on that and for me there is no discernible difference in feel to my riding.

It would be a shame for you to not be able to use the TSDZ2 and its torque sensing characteristics vs those of a hub, but needs must and all that.

 

[Simon Knight]

Hi @Simon Knight - going back to your original post


I'm lucky enough to not have the type of knee problems that you have, but out of curiosity I'm wondering how much difference in Q factor is needed from that of the TSDZ2 to what ever the original trike chainset was, to cause you knee issues? Have you measured up the offsets between the two systems?

When I installed my first TSDZ2 I read about the crank offset issue and bought a pair of cranks used on the Bafang mid drive as they were offset less, but I only did that out of idle curiosity rather than a specific need.

Since then I've a second bike/TSDZ2 fit and use the standard TSDZ2 cranks on that and for me there is no discernible difference in feel to my riding.

It would be a shame for you to not be able to use the TSDZ2 and its torque sensing characteristics vs those of a hub, but needs must and all that.

I will try and find the figures and post them. I am aware that I am blaming the TSDZ2 but the other factor is that I was riding further and often above the motor cutout speed. So my plan was to ride the original unassisted version over similar distances (forty five miles) to see if my knee issue returns. So far I have not completed enough rides but I have suffered more but different knee issues.

My initial thoughts are the TSDZ2 is offset to the right and that this non central position is what causes my knee problems. Thinking about the problem a straight Bafang crank fitted on the chainwheel side may be enough to centralise the pedals.

 

[guerney]

@matthewslack fashioned this to attach his Shimano motor to his recumbent, which might be of interest:

https://www.pedelecs.co.uk/forum/threads/new-ex-electric-soon-to-be-electric-trike-project.45221/post-681916

 

[Simon Knight]

Hi @Simon Knight - going back to your original post


I'm lucky enough to not have the type of knee problems that you have, but out of curiosity I'm wondering how much difference in Q factor is needed from that of the TSDZ2 to what ever the original trike chainset was, to cause you knee issues? Have you measured up the offsets between the two systems?

When I installed my first TSDZ2 I read about the crank offset issue and bought a pair of cranks used on the Bafang mid drive as they were offset less, but I only did that out of idle curiosity rather than a specific need.

Since then I've a second bike/TSDZ2 fit and use the standard TSDZ2 cranks on that and for me there is no discernible difference in feel to my riding.

It would be a shame for you to not be able to use the TSDZ2 and its torque sensing characteristics vs those of a hub, but needs must and all that.

Numbers numbers numbers!

I have just re-measured both the original cranks and chainwheel set, which are presently fitted to my ICE trike, and the TSDZ2 which was measured unfitted and compared with a design drawing I found on the web. Accurate measurements are quite difficult so I have to say mine are probably +/- 2mm worst case.

ICE bottom bracket shell is 68mm wide.
ICE fitted front tripple by Campagnolo:
Q or tread 167mm - this is the distance between the outside edges of the cranks at the pedal holes.
Measuring from the centre of the boom is difficult so I measured the distance from the inside edge of the cranks to the edge of the boom. Both sides measured 49mm. The boom has a diameter of 41.5 and the cranks are 15mm thick. Adding these numbers gives a Q of 169.5 which confirms the original measurement. The 167mm will be more accurate as its a single measurement.

The crank and pedals are centred on the centre of the boom so (new term) Q offset is 0mm

TSDZ2 with supplied cranks

Q or tread 213mm

Q delta (Difference between the two) is 46mm

Measuring the offset was based on the location of the flange that abuts the bottom bracket shell on the chainwheel side. Measurements were taken from the inside edge of each crank arm at the point of fit on the square taper of the axel .
Left crank 89.5mm, Right crank 44.6mm. The flange sits 34mm from the centre of the bottom bracket shell meaning the locations of the cranks on the axel are as follows. LHS 89.5-34=55.5mm ; RHS 44.6+34=78.6mm. The difference is 23.1mm meaning that the right hand side is 23.1mm further from centre line than the left.

Lastly I measured the crank curve by placing the axel end on a flat surface and measuring how much above the surface the pedal hole fell (measured to the side the pedal is fitted to). The supplied cranks measured 37mm as did the Campag' ones.

I would be interested in knowing how much crank curve the Bafang ones have as it may be an option to try a straight crank on the chain ring side to reduce how off centre the right pedal is. A more drastic option is to have a new boom made with the shell offset to the left by 23 mm.

Summary of figures:
Q original 167mm, zero offset.
Q TSDZ2 213mm, 23.1mm offset on chain side.

crank curve 37mm

I hope that the terms that I use are helpful and clear.

S

 

[matthewslack]

Numbers numbers numbers!

I have just re-measured both the original cranks and chainwheel set, which are presently fitted to my ICE trike, and the TSDZ2 which was measured unfitted and compared with a design drawing I found on the web. Accurate measurements are quite difficult so I have to say mine are probably +/- 2mm worst case.

ICE bottom bracket shell is 68mm wide.
ICE fitted front tripple by Campagnolo:
Q or tread 167mm - this is the distance between the outside edges of the cranks at the pedal holes.
Measuring from the centre of the boom is difficult so I measured the distance from the inside edge of the cranks to the edge of the boom. Both sides measured 49mm. The boom has a diameter of 41.5 and the cranks are 15mm thick. Adding these numbers gives a Q of 169.5 which confirms the original measurement. The 167mm will be more accurate as its a single measurement.

The crank and pedals are centred on the centre of the boom so (new term) Q offset is 0mm

TSDZ2 with supplied cranks

Q or tread 213mm

Q delta (Difference between the two) is 46mm

Measuring the offset was based on the location of the flange that abuts the bottom bracket shell on the chainwheel side. Measurements were taken from the inside edge of each crank arm at the point of fit on the square taper of the axel .
Left crank 89.5mm, Right crank 44.6mm. The flange sits 34mm from the centre of the bottom bracket shell meaning the locations of the cranks on the axel are as follows. LHS 89.5-34=55.5mm ; RHS 44.6+34=78.6mm. The difference is 23.1mm meaning that the right hand side is 23.1mm further from centre line than the left.

Lastly I measured the crank curve by placing the axel end on a flat surface and measuring how much above the surface the pedal hole fell (measured to the side the pedal is fitted to). The supplied cranks measured 37mm as did the Campag' ones.

I would be interested in knowing how much crank curve the Bafang ones have as it may be an option to try a straight crank on the chain ring side to reduce how off centre the right pedal is. A more drastic option is to have a new boom made with the shell offset to the left by 23 mm.

Summary of figures:
Q original 167mm, zero offset.
Q TSDZ2 213mm, 23.1mm offset on chain side.

crank curve 37mm

I hope that the terms that I use are helpful and clear.

S

That's a useful bunch of measurements.

My plan was always to build a new front boom section, which can be fairly agricultural in prototype form, taking great care with diameter of the end that fits in the frame.

There is not much room for error there as not much range of adjustment and aluminium will not forgive being squeezed too much.

So far I have used a standard size tube plus a shim outside it, but not quite happy yet. When I get home it is high up my list of to do next.

 

[guerney]

That's a useful bunch of measurements.

My plan was always to build a new front boom section, which can be fairly agricultural in prototype form, taking great care with diameter of the end that fits in the frame.

There is not much room for error there as not much range of adjustment and aluminium will not forgive being squeezed too much.

So far I have used a standard size tube plus a shim outside it, but not quite happy yet. When I get home it is high up my list of to do next.

Are you tempted to finally install that TSDZ2 you've got trapped in a box? I'm curious as to why you chose the Shimano motor instead of the TSDZ2 for your recumbent. If you've had your TSDZ2 in storage for a couple of years, it's likely to be flashable with OSF?

 

[Bikes4two]

@Simon Knight

I would be interested in knowing how much crank curve the Bafang ones have

Hopefully the pic below helps in this respect (with an image taken from google for illustration purposes, courtesy of Cycling news). The crank Q factors were more difficult to measure with things in situ but I have a reasonable eye, so hopefully not too far out - let me know if any pics of my installation might help (on an upwrong bike though).



As an aside, my wife (only 5ft zero) got sore knees riding our tandem to we got custom shortened cranks which resolved the problem for her - it wasn't a cheap fix but worth it - I think we arranged the work through a tandem shop - maybe JD Tandems?

 

[guerney]

Depending on the knees, for some people it might not take much of an angle at the soles to cause knee pain? One could experiment I suppose, by cutting an angled wedge out from the inner underside of the soles of an old pair of shoes, and going for a long walk while carrying a weight, or climbing mutiple flights of stairs?

 

[matthewslack]

Are you tempted to finally install that TSDZ2 you've got trapped in a box? I'm curious as to why you chose the Shimano motor instead of the TSDZ2 for your recumbent. If you've had your TSDZ2 in storage for a couple of years, it's likely to be flashable with OSF?

I shall try both, and perhaps a rear hub motor too. I"m very comfortable with the Shimano e5000, after 22,000km of experience, so starting with that removes some unknowns. I didn't buy the spare e5000 with this in mind, it is backup in case I discover the life expectancy of the first one in my Ridgeback!

 

[Simon Knight]

@Simon Knight

Hopefully the pic below helps in this respect (with an image taken from google for illustration purposes, courtesy of Cycling news). The crank Q factors were more difficult to measure with things in situ but I have a reasonable eye, so hopefully not too far out - let me know if any pics of my installation might help (on an upwrong bike though).

View attachment 53878

As an aside, my wife (only 5ft zero) got sore knees riding our tandem to we got custom shortened cranks which resolved the problem for her - it wasn't a cheap fix but worth it - I think we arranged the work through a tandem shop - maybe JD Tandems?

@Bikes4two Thanks for the picture and measurements. So it seems that fitting a single Bafang crank will reduce the Q and crank Q by 17mm and reduce the misalignment by the same amount. I'm going to continue with the non electric version and conduct some more longer rides so that I have a baseline of how my knees react before I refit the Tongsheng.

S

 

[Simon Knight]

I shall try both, and perhaps a rear hub motor too. I"m very comfortable with the Shimano e5000, after 22,000km of experience, so starting with that removes some unknowns. I didn't buy the spare e5000 with this in mind, it is backup in case I discover the life expectancy of the first one in my Ridgeback!

@mathewslack I was not aware that it was possible to buy a Shimano system, may I ask where you purchased it?

S

 

[matthewslack]

@mathewslack I was not aware that it was possible to buy a Shimano system, may I ask where you purchased it?

S

I have bought individual components secondhand, mainly via eBay, as and when they have come up.

I use Shimano, many would warn against on perceived reliability and unserviceability grounds, because it is the only brand I have experience of.

I have a Ridgeback X2 which got me into ebikes, realised I wanted to do longer trips so started with a second battery, only a 418Wh, but also only £225.

A spare motor seemed a good idea when my total distance went above 10,000km, as insurance against failure, and that cost only £175.

Display was another £50, and cables vary from a few quid second hand or full price when necessary.

I can't speak for Bosch or Yamaha etc, but my Shimano E5000 is only those three parts plus cables and speed sensor, just plugs together and works.

Total cost of my spare system has been £450 to get working.

Bigger batteries don't come up very often and I have never seen a cheap one, but two small ones are bigger than one of the biggest, and allow two chargers at once for winter cafe and pub touring!

Another way would be a neglected but hardly used cheap Shimano equipped bike. Then you get a full set of bits known to work together, possibly for much the same cost.

 

[Simon Knight]

I have bought individual components secondhand, mainly via eBay, as and when they have come up.

I use Shimano, many would warn against on perceived reliability and unserviceability grounds, because it is the only brand I have experience of.

I have a Ridgeback X2 which got me into ebikes, realised I wanted to do longer trips so started with a second battery, only a 418Wh, but also only £225.

A spare motor seemed a good idea when my total distance went above 10,000km, as insurance against failure, and that cost only £175.

Display was another £50, and cables vary from a few quid second hand or full price when necessary.

I can't speak for Bosch or Yamaha etc, but my Shimano E5000 is only those three parts plus cables and speed sensor, just plugs together and works.

Total cost of my spare system has been £450 to get working.

Bigger batteries don't come up very often and I have never seen a cheap one, but two small ones are bigger than one of the biggest, and allow two chargers at once for winter cafe and pub touring!

Another way would be a neglected but hardly used cheap Shimano equipped bike. Then you get a full set of bits known to work together, possibly for much the same cost.

@Mathewslack - thats a great idea. I asked because ICE, who make my trike, now fit the Shimano motor to their new electric trikes. This means that a custom Shimano friendly front boom should be available. https://www.icetrikes.co/ . Also I suspect that the Q factor is much narrower than my present Tongsheng and is therefore better for my knees.

 

[Simon Knight]

@mathewslack

"I use Shimano, many would warn against on perceived reliability and unserviceability grounds, because it is the only brand I have experience of."

I think it is very hard to gain an accurate picture of reliability based on what is on the web. I suspect that it depends on how the motor and battery have been used. Many mid drives are fitted to mountain bikes which are likely to have a hard life especially if they get washed down after every ride with a pressure washer. I am often shocked at how little appreciation people have for electro mechanical devices expecting them to just work. They fail to appreciate that a little care and maintenance goes a long way.