The TSDZ2 is highly configurable by those with a penchant for such things (read here for an insight into this area).

The 'as supplied' TSDZ2 run with a 36v battery will likely meet the UK pedelec requirement of 250w continuous power and which officer of the law is in a practical scenario going to be able to determine this? Said officer may check that your bike motor only kicks in when you pedal and doesn't offer power above the 15.5MPH speed limit (of which both parameters can be adjusted in firmware if you know how), but apart from that, no worries.

If in doubt, search ebay/google for "ebike motor label" and buy a 250W label and stick it on the motor casing.

Good idea about the label!

Changing the label seems a cute dodge but the reality of the situation is that UK road traffic law calls for users of bicycles with a more than 250w motor to have insurance, wear a helmet and to ride only on public roads (not cycle paths) or private land. Infringing helmet and insurance rules carry heavy penalties which may even affect any other driving licence you hold or aspire to having, yes youngsters you can be disqualified from holding a car licence before you have one.

New label   -  cool  but not clever.

Changing the label seems a cute dodge but the reality of the situation is that UK road traffic law calls for users of bicycles with a more than 250w motor to have insurance, wear a helmet and to ride only on public roads (not cycle paths) or private land. Infringing helmet and insurance rules carry heavy penalties which may even affect any other driving licence you hold or aspire to having, yes youngsters you can be disqualified from holding a car licence before you have one.

New label   -  cool  but not clever.

Best would perhaps be both to have the label and also to be compliant.  The question I have not resolved is to how to ensure the Tongsheng is working at 250W.   First step is only to use a 36V battery.  But even then, it is advertised as being both 250W and 350W, and I can't see any way to ensure that it is delivering at the lower rating.  Any ideas?

By the way, here is an excellent article, albeit very much written from an American perspective since the writer argues that his 750W restriction is unfair!

https://www.electricbike.com/tsdz2-750w-mid-drive-torque-sensing/

Stephen, Have you asked the question about ensuring only 250w on ebike specific forums like the UK Pedelec forum or the Endless Sphere forum?

I think you are up against it in terms of finding a simple solution to your requirement (of ensuring 250w max). The TSDZ2 can delivery a wide range of power that apart from the battery voltage and power rating of the controller used, is down to firmware settings. I've only read articles on the TSDZ2 firmware side of things, so no direct experience (yet), but I suspect to limited the power to 250w will require firmware adjustment.

So assuming that you (or someone else) manages to alter the firmware to limit the power to 250w, what then in terms of demonstrating UK compliance to an officer of the law - how might this be done? 

In practical terms, I can't see how such a demonstration can be done, and if not, was all the effort worth it in the first place? 

Just asking :-)

Stephen, Have you asked the question about ensuring only 250w on ebike specific forums like the UK Pedelec forum or the Endless Sphere forum?

I think you are up against it in terms of finding a simple solution to your requirement (of ensuring 250w max). The TSDZ2 can delivery a wide range of power that apart from the battery voltage and power rating of the controller used, is down to firmware settings. I've only read articles on the TSDZ2 firmware side of things, so no direct experience (yet), but I suspect to limited the power to 250w will require firmware adjustment.

So assuming that you (or someone else) manages to alter the firmware to limit the power to 250w, what then in terms of demonstrating UK compliance to an officer of the law - how might this be done? 

In practical terms, I can't see how such a demonstration can be done, and if not, was all the effort worth it in the first place? 

Just asking :-)

Hi Colin, I take your point but the 250w power limit is often deemed to be the 'maximum continuous power' - thus peak powers far in excess of 250w are often output by these motors, the TSDZ2 being one such example. (I say often, but not always - just search about pedelec/eapc law and EN15194 and see that UK gov sites don't use the word 'continuous' but sites referring to EN15194 often do - it's bit of a mess really as UK law is based on the EN law.)

And let's be clear here, there are commercial offerings for purpose built etandems and etandem conversion kits that are sold (and labelled) as 250w and from the tandem riders I've spoken with, the motors give a very acceptable level of assistance which rather underpins the supposition that peak powers above 250w are when needed, being delivered by these motors.

We all take risks of every sort in our daily lives but to me, worrying about whether the TSDZ2 motor is or is not conformant to a law that itself has ambiguities, is down there with worrying as to whether I'll get struck by lightening tomorrow.

Just my humble opinion of course on a topic widely debated on the forums I previously mention, and the Cycling UK forum and no doubt many others. 

My kit arrived for me in Poland from Germany recently.  Although advertised as both 48v and 36v, the motor has a label on it, as shown, only saying 36v.  Curiously, the immaculate and never opened box stated that the contents were a Bafang MM.G250, which at first had me thinking I had been sent the wrong motor.  So maybe Bafang own Tongsheng.

In case it is of interest, I found a way to mount the motor on the front bottom bracket by cutting and filing an old quill stem to hold the motor steady.  The result is pretty sturdy and I think as good, or even better, than would be the case using the elbow provided for attaching at the rear (which I did not need to use).

I am not yet finished with the installation since I must switch the chain tensioner to the opposite side now that all chains run on the right hand side.

My kit arrived for me in Poland from Germany recently.  Although advertised as both 48v and 36v, the motor has a label on it, as shown, only saying 36v.  Curiously, the immaculate and never opened box stated that the contents were a Bafang MM.G250, which at first had me thinking I had been sent the wrong motor.  So maybe Bafang own Tongsheng.

In case it is of interest, I found a way to mount the motor on the front bottom bracket by cutting and filing an old quill stem to hold the motor steady.  The result is pretty sturdy and I think as good, or even better, than would be the case using the elbow provided for attaching at the rear (which I did not need to use).

I am not yet finished with the installation since I must switch the chain tensioner to the opposite side now that all chains run on the right hand side.

My kit arrived for me in Poland from Germany recently.  Although advertised as both 48v and 36v, the motor has a label on it, as shown, only saying 36v.  Curiously, the immaculate and never opened box stated that the contents were a Bafang MM.G250, which at first had me thinking I had been sent the wrong motor.  So maybe Bafang own Tongsheng.

In case it is of interest, I found a way to mount the motor on the front bottom bracket by cutting and filing an old quill stem to hold the motor steady.  The result is pretty sturdy and I think as good, or even better, than would be the case using the elbow provided for attaching at the rear (which I did not need to use).

I am not yet finished with the installation since I must switch the chain tensioner to the opposite side now that all chains run on the right hand side.

My kit arrived for me in Poland from Germany recently.  Although advertised as both 48v and 36v, the motor has a label on it, as shown, only saying 36v.  Curiously, the immaculate and never opened box stated that the contents were a Bafang MM.G250, which at first had me thinking I had been sent the wrong motor.  So maybe Bafang own Tongsheng.

In case it is of interest, I found a way to mount the motor on the front bottom bracket by cutting and filing an old quill stem to hold the motor steady.  The result is pretty sturdy and I think as good, or even better, than would be the case using the elbow provided for attaching at the rear (which I did not need to use).

I am not yet finished with the installation since I must switch the chain tensioner to the opposite side now that all chains run on the right hand side.

Hi Colin

It's not really clear what is "intended" for a tandem, although usually motors are on the stoker bottom bracket, I do agree.  Yes, I think it could quite easily go on the stoker bottom bracket too, and anchoring the motor would then be easier (and in that sense would be what is intended).  However, I'm keen that the torque sensor responds to my movements as captain.  Maybe the torque on both bottom brackets is just the sum of the torque from both riders, but I want maximum response to my own movements.  My stoker just follows my movements.

I think you can ride solo even with the motor at the back, given comments elsewhere.

A small benefit of having the motor at the front is that all the cabling can be standard, except perhaps for the battery cable if the battery is at the rear.  But that is not the deciding factor really.

I think chain alignment may be a little easier if the motor is at the front, since the front chain is longer.

Either way, the solution seems to me to be to have both chains on the right hand side.  If you have the motor at the rear bottom bracket, and want a chain ring either side of the motor, clearance is then a big issue on the left hand side, because the motor will foul a left hand chain ring.

So, yes, if both chains are on the right hand side, I think there are good arguments both ways in terms of whether to have the motor at the front or at the rear bottom bracket.

Neither of my bottom brackets is elliptical, but if one were, then I would put the motor on the non-elliptical bottom bracket of course.

A further point is that if your chains are already both on the right hand side, then having the motor at the front just means swapping the motor and its integral chainring for the existing single chainring at the front.  If you put the motor at the stoker position, you need to fasten a second chainring to the motor chainring.  This is doable, but it adds cost, and alignment with your rear gears may not be correct.

Also, if you have a front derailleur, it would not be effected if the motor is on the front bottom bracket.  (However, I hate derailleur gears on tandems!)

As an alternative to fashioning an old quill stem to clamp the motor to the tandem boom bar, for possible inspiration have a look at the 'P' shaped clamp here used to clamp the motor to a recumbent trike boom bar. (in case the hyperlink subsequently goes dead, the website is eco-bike.com and search for trike boom clamp)