Chris, I have no direct experience of fitting to a tandem, about to fit a Swytch kit to a solo bike, so have done some digging before we bought it.

You do not say if you have already bought the wheel or planning to do so.

If you are still in the planning purchase stage in on of the Tandem Club magazines in the past 4 years there was some discussion, one of the contributors mentioned Cytronex as a supplier . Their website has a kit building page and specifically mentions a tandem wheel as part of the build, it may be worth contacting them.

If you already have the wheel it would be worth contacting Thorn for advice.

Whilst looking into the Swytch kit, most of the discussion about the good and bad was around the size of the hub motor to ensure that it would fit into the drop-outs and between the forks.

from one Gray to another I hope this helps,.

Seven years ago we added a Sunstar ibike SO3+ mid drive motor to our Pino tandem - see attached article.  A mid drive motor doesn't affect the handling of the tandem in the same way as a motor within the wheel.  We are well pleased with our choice.  The Sunstar is no longer made but there are a number of alternatives on the market now, generally less expensive.  You might want to research these before finally deciding what to do.  A point to watch out for is the wattage - some kits like the Bafang exceed the legal 250w limit for a pedelec.   It would be worth consulting an expert like Eddie Kehoe of Electric Bike Sales in Cambridge who fitted our Sunstar, to see what he now recommends.

Peter Mynors  

Thanks for the information guys. I don't think the Swtch is powerful enough for a tandem. Currently looking at a cheap option Yose but compatibility with the forks is a problem or Cytronex, at least their technical information is good. The alternative would appear to be a Pendix mid drive. Pretty expensive and proffessional fitting is recomended. Also not sure about subsequent problems of tightening the chains with the eccentric bottom brackets after adding a Pendix.

Colin

Hi

I have fitted a Yose front wheel kit to a Solo bike, quite a powerfull front motor & a choice of Battery Sizes. Would suggest a 15Ah battery for a Tandem.Good software to enable a user selected set up. Total cost about £400 .

N.B. a friend had a Cylotrex unit but found that the Battery Size was too small!

Tony

Hi Colin

we are just in the process of getting a Bafang motor fitted to our Bob Jackson custom built orbit. I have a cyctronex on a single bike. It is good on that but the range is pretty limited as the battery is not very big.

You can get a Bafang motor that is 250W but it is a 36v model. The Bafang 48V models will give greater range. You can have them configured to deliver maximum continous output of 250W (via limiting maximum current] You can get a 48 volt 22 amp hour battery which should give a really good range.

We know someone else who went the Bafang route on a Thorn and was really happy with it. We do not yet know whether there will be sufficient chain tension adjustment for the Rohloff from the two eccentrics once the motor is fitted to the front BB but have a backup plan of fitting a chain tensioner to the rear dropout to take care of rear chain leaving the rear eccentric to adjust the timing chain. If you can wait a couple of weeks, I will be able to let you know how all that worked out and send some pics. You can probably fit a Bafang system yourself and I was tempted to do that but the guy who is doing it for me has done it before and has all the right contacts for getting compatible chainrings to sort out chain line etc.

Steve (and Jill)

> Our tandem is Rohloff fitted and there are eccentric BB's front and rear.

> I have fitted 4 TSDZ2 motors to solo bikes and the clearance on the BB shell on a standard bike frame is around 4 mm between the motor casing and shell, so not a lot and usually requiring the removal of derailleur cable guides

> I believe the Bafang has similar limitations too, so I'm thinking that an adapter in an eccentric BB shell to accept either of these motors would make the fitting of a TSDZ2 definitely out of the question and probably the Bafang too (but that's a guess regarding the Bafang).

I would recommend that you consult/join the pedelec.co.uk and Cycling UK forums to post your question(s) there. I have seen numerous posts on people converting tandems and those forums are also good places to 'sound out' customer support from different companies (Swytch and Cytronix get a few mentions in this respect).

Whilst forums disproportionally attract posts about 'it's broke, how do I fix it' type of  questions, none the less you can glean a lot of useful information. 

In our local tandem group there are three Cytronex tandems and all owners have expressed their happiness at the fit (but who would say otherwise if you'd just spent £1k on something!), and of course whilst the battery is only 198Wh (watt hours are the amp hours multiplied by the nominal battery voltage), if you're only cycling small miles (20?) with little assist, then that battery will be fine. 

Bigger batteries come at greater weight but give you greater range (and not just because your motor is 48v rather than 36v as suggested up thread - power delivery is a product of the current available from the battery via the settings on the motor controller, and the battery voltage, as in P=I x V.).

And then there's the whole question of the '250w continuous power' issue **, - many people are entirely comfortable using motors rated higher than this - a personal choice of course.

** - the 250w continuous power question - first of all, note the use of the word 'continuous' - even motors legally set to 250W from the likes of Bosch, Yamaha and Shimano, have peak power outputs of more than double this - entirely legal.

Further, the 250w continuous power figure relates to the power output of the motor rather than the input power, and if you read BS EN 15194, it describes near laboratory conditions to be able to measure this.

Any officer of the law will not likely be doing this but they can however very quickly determine if the motor assist goes beyond the 25KPH (15.6MPH) limit and determine if the motor is only activated by the pedals being turned. 

We thought a Yose might be a good option as its cheap so I ordered one. The axel would not fit any of 3 pairs of forks, the crank was too close to the bottom bracket for the pedal sensor to work and the brake levers were so flimsy I would not trust them as a safe option on a tandem. I was also advised by a local bike shop that all cheap Chinese motors provide a very sudden impulse when you start peddling which can damage the front wheel dropouts. Bearing in mind the large mass of a tandem plus two people that's potentially dangerous. Yose are also a dreadful company to deal with. Took ages to get them to reply to my e-mail regarding return and then told me to send it to Germany at enormous cost. Also this was impossible as no carrier would accept it so eventually they provided a UK address. Return carriage was still nearly £30.

In the end we ordered a Cytonex conversion kit. Excellent customer services and its well designed. When you pedal the power is applied smoothly so no impulse problems in the dropouts and the bike rides perfectly. At low power you are hardly aware of the assistance except it's easier to pedal. 

I am aware that it has a relatively small battery. We did 21 miles on Saturday using a range of battery powers on 69% of the battery. Since we are needing 'e-assist' rather than an excuse not to pedal very vigorously I am sure we could easily get 40 miles, or more, out of a single charge with intelligent use of the power modes.

We also ordered a fast charger and can carry that with us on longer rides.A decent cafe stop should allow for some recharging. If all else fails and we need more support as we get older the battery is so light we could carry a second battery. At 1.5 kg and £500 for a second battery that would still be a fair bit cheaper than over£2000 for a Pendix conversion.   

Hi Colin

wrt " ..... I am sure we could easily get 40 miles...", my experience of electric bikes and tandems is that the last 1/3 of battery power disappears remarkably quickly so I'd be a little on the cautious side of 40 mile expectation. We have a 20A battery on our tandem and get 63 miles pedal assist.

Happy e-t-ing!

Chris

Hi Colin

We too fitted a Cytronex system and found we flattened the battery so asked for a second one only to be told they would not supply because that would harm their complete systems as they were so short of batteries. I went down the route of getting an e bike specialist in London to help. He took off the top of the battery bottle ( which has the management system ) and linked it to a bigger battery.

However the system was too clever and although we have a bigger battery the management system still thinks its the bottle as before so no extra supply. We now have managed to get Cytronex to supply a second battery and are running with both , a little Heath Robinson but it works. Would have been simpler if they had supplied 2 in the first place !!!

John