Hi Charles. The Cytronex is reasonably easyy to fit and very easy to use. I have one in a single bike that I used for several years working as a cycle instructor. It is good for about 40 to 50 mile used on the lowest setting. I am not sure that the torque would be enough for a tandem but talk to Cytronex as I believe they have different versions. It is activated by a simple freewheel or sprocket rotation sensor and is not input torque sensitive.

One thing that you need to check before buying is the compatibility with your front forks. It relies upon the tight fitting of flats on the axle into you fork ends i.e. it doesn't have a torque arm. I would be a bit worried about just relying on the hardness of the fork ends on a tandem as with the extra stress especially on hills it might end up opening up the fork ends.

You need to talk to the guy who owns the company and check about that. They might have a talk arm version by now.

Just give them a call they are very helpful.

stephen

I think that the Cytronex system uses a form of cadence sensor rather than a torque sensor.  Having ridden with a torque sensor for the last 10 years on our S&S Pino, we had to change to a different e-system this year because our old system failed and is no longer made.  The new motor (Bafang) uses cadence sensing, not torque sensing.  On the basis of this experience I would strongly advise that whatever system you buy, you get one that uses a torque sensor as this gives a much more intuitive ride.   

Having done further research recently I think that one promising system worth investigating is the CYC Photon, although I've never tried one of these.  They are quite expensive, but still cost less than we paid for our discontinued system 10 years ago.  It is a mid drive system so the power assistance can make use of the bike's gears.

I actually wrote a letter to The Times on this subject recently and was pleasantly surprised when they published it.

We do not have a Cytronex. We have been into the shop (local to us) a few times for other things and they've always been helpful.

The Cytronex kit is neat. It is very highly priced for what it is, with a very low capacity battery and low torque motor.
Any parts are likely to be expensive (eg 495 for a 198Wh battery), and may even become unavailable. 

Consider Woosh as an alternative. https://wooshbikes.co.uk/?hubkits#xf07kit 
We have had this kit for 6 faultless years on a fairly basic Viking tandem.
With a bag battery (still lowish capacity but much more than the Cytronex) it now costs £449. (ours came with a different downtube battery).
The torque is 42NM, quite low but again higher than the 35NM I believe the Cytronex has.
Neither will drive you up a steep hill on a tandem without lots of extra help from both riders.

The Woosh parts are all generic; you might not get a like for like replacement but spares will always be available.
It will be a little heavier than the Cytronex, and probably not quite as neat.

Woosh have exceptional pre and post sales customer support.
Fitting was easy, and would be with the Cytronex as well.

As in the earlier post, check your front forks are suitable. 
Steel will probably be OK. For other forks check with Cytronex or Woosh before going ahead. 

Front wheel is not  the best place for a motor, but this is not so important with the different weight distribution on a tandem.
We have sometimes (slight uphill slippery grass) even found it to help as both wheels have traction.

~~~

We've just moved on to an even more basic Ecosmo tandem; our rides are getting shorter and I was finding the crossbar a pain.

We might be selling the Woosh kit 2nd hand fairly soon; but the downtube battery might not suit.

You are welcome to try the Woosh/Viking to get an idea of what to expect. Winchester.

Hi Charles

I fitted the system on my Santana Beyond, very good system , went to their shop in Winchester, very helpful, trieda sosl with the system fitted, great !

Easy to fit

Found it not quite man enough for a Tandem, ours is Carbon and Titanium so light, after research found I had to change the forks from carbon to steel, no one would provide test info covering the torque on carbon. 

I wanted a second Battery, they we not able to provide, so added a system to link when we flattened the first one.

THEY DIDNT LIKE THIS AT ALL.

I feel the system is not powerfull enough for a Tandem better suited to a solo

Thanks for all replies. I've fitted Cytronex to my tandem, and used it today for the first time. A bit fiddly to fit but not difficult except for the safety catch mentioned below. Very good in use. I guess that we cycled about 20 miles, I had Cytronex on nearly all the time, although not necessary but just to get the feel of it. I suspect that usually we'd use it only on the hills. Given the use made of it today the battery was showing a red light when we got home. The only issue about fitting it is that I had to remove the "lawyers lugs" on the fork dropouts to get a close fit for the wheel nuts. And there is a safety catch at the bottle holder latch. Any one had any difficulty with getting this right? It's supposed to drop over the latch but I've found this very difficult to do. Thanks again. Charles.

Hi Charles re the safety catch on the cytronex battery...

My battery (bottle shaped) has a slot in the bottom which engages on the bottom of the cage. The top of the bottle is captive on the bottle cage and locks onto the battery by twisting about 30 degrees (sort of a bayonet fitting). It can be a bit stiff to lock / unlock especially with cold hands. I find that sometimes it helps to hold the battery and give it a bit of a wiggle to help the engagement process. Yours might be a different locking mechanism as mine is about 8 years old now. A picture of the battery located in the cage but not locked would help me to understand if it is the same or different.

Thanks Stephen,

Your battery and mine sound to be the same. My Cytronex has a  metal clip at the bottom of the battery holding cage latch which is meant to drop over the cage latch when it's closed and this clip acts as a safety clip. I cannot get this to engage where it should except with what I feel is excessive persuasion. And then it has to be released to remove the battery. I aked Cytronex for advice and they said to check the screws holding the cage were fully tightened with a view to pushing the clip down so as to drop over the cage latch. This I did. The screws tightened a little bit but now will go no tighter. Dropping over isn't possible, force is needed which I don't like to do, although I appreciate the wisdom of a safety clip. I attach a photo of the latch and clip. 

As I thought, that is very different from mine. Mine does not have any sort of clip at the bottom of the battery. It relies on the "tail" of the cage locating directly into a slot on the bottom of the battery. All securing is from the bayonet catch where the cables connect at the top of the battery. It is easy to use and very secure but as I said twisting the bayonet catch can be difficult with cold or wet hands.

 I can't easily get to my bike with the cytronex on right now as garage is rammed but I might be able to get a photo of mine tomorrow. I know a couple of people in the tandem club have a much newer cytronex than mine e.g. Colin and Rosie Gray. Maybe they can help .....

Thanks Stephen,

It's interesting that your Cytronex has no clip. After fitting Cytronex and when I looked at the user manual, in some photos no clip was visible and this caused me to think that this clip is perhaps a relatively recent addition. The battery seems to me to be very secure and although it weighs about twice as much as a full water bottle this doesn't seem to be a concern. If Colin and Rosie can comment that would be helpful. Very grateful to you for your input to this.

Charles.