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E-tandem conversion kits

Michael Holley2021-02-20 16:01:19

I am currently looking to fit an e-bike kit to our Viking Tarantino tandem and wondered if anyone had any advice. Following an earlier discussion by a member in the forum who electrified a Tarantino I have opted for a Whoosh kit, but we're having issues identifying the best place and method of fitting the pedal sensor. The clearances on the bottom brackets on our bike don't seem to be wide enough to accommodate the sensor disc without fitting an extra long pedal shaft. Any advice would be welcomed if anyone has had similar issues or has other useful suggestions.

John Spelman 2021-02-22 10:14:45

Hi Michael

I have just fitted a whoosh kit to our Thorn tandem. I used their DWG22 motor and I'm really impressed with power. I did have to change the back bottom bracket, which I've never done before but wasn't so difficult although I was glad to have an old torque wrench to undo the old one. Once I had the old one out they sent me one which would fit which cost £14 and arrived very promptly. Now on the road it certainly makes light work of hills and easier to change gear with less pressure on the chain if you're late changing down.



Michael Holley2021-02-22 15:14:54

Thanks for your info John, very useful. 



Lawrence McPhillips2021-02-28 17:14:31

Hi John - I'd like to pick your brains a little bit on your conversion if I may.

I've just ordered exactly the same kit from Woosh for our Orbit (alloy) tandem and I intend to use torque arm(s) to prevent any possible damage to the dropouts.

Did you fit torque arms to your Thorn (less of a concern with steel I know) and if so what type?  I'll probably end up making my own from 6mm steel, but I'm tempted to use an off-the-shelf solution in the meantime.

Do you find the hub motor is able to cope with steeper climbs at slow speeds without overheating?  We're a lightweight team, but we do have some pretty decent hills in my area.

Any information would be welcomed.



Chris Allen2021-02-28 18:35:46

Hi Lawrence - can you let us know how you get on? We too have an alloy Orbit and like you are a relatively light weight couple. We're in our early 70s, inexperienced two-uppers and during lockdown I've been considering an e-conversion. Your experiences and thoughts would be greatly appreciated.

Many thanks!


Lawrence McPhillips2021-02-28 19:20:04

Hi Chris,

Yes, happy to share my experiences (good or bad!) with you.  I don't think I can send you an email rather than clog up this thread, but admin may be able to forward you my email address if I ask them.

As a team, we're actually quite similar to yourselves - lifelong solo riders, but new(ish) to tandems.  Early 60's age range and getting to the point where health issues mean that a bit of help on the steeper climbs would be great.  I haven't got my Woosh kit yet, but top-of-the-head stuff that I want to consider:

Can we fit the battery on the boom-tube (with suitable shock absorbing) to keep the weight as low as possible and centralise the mass.

How far into the rear drop outs will the hub-motor axle go - they're designed for 9mm axles not the chunkier ones on a hub motor.

Torque arm - personally, a must have for me on an alloy frame.   The frame was never intended to cope with 60Nm of torque and perhaps more importantly, to accommodate the inertial shock loading of a big heavy wheel if (when) I hit a bad pothole. I may be over reacting to the possible adverse effects of fitting the hub motor without torque arms, but I’d rather do that than wreck the frame, hub motor and possibly me too!

Wheel dishing / centralising in the frame.

How slowly it is possible to run these motors without heat damage? On really steep climbs, the gearing on our tandem allows us to go as slowly as 5 mph at a cadence of 90 rpm. I would hope the new motor would help avoid speeds quite as slow as that, but is it sensible to expect a hub-motor to cope with low speed / high power without suffering overheat damage? If it means getting off and walking, I’d rather do that than ‘cook’ a motor.  As far as I know, there is no way to read the internal temperature of the motor.

Best place for the pedal assist sensor - front bottom bracket looks like an ideal place, but we'll see.  We currently have 122.5mm axle width and I'd prefer not to increase the 'Q' factor with a longer axle.

Chris Allen2021-02-28 23:22:38

Hi Lawrence,

I wouldn't worry about writing up stuff on here as I'm sure there are/will be others considering going the e route.

Thanks for putting in the brainpower too. Can't wait to hear how it goes!


John Spelman 2021-03-02 07:52:00

Hi Lawrence, I didn't fit torque arms to my Thorn tandem conversion, but I can imagine if your wheel nuts weren't tight the lug in the drop out  could damage it. Tony at whoosh seems to have a lot of experience about fitting electric motors to tandems and cargo bikes, so might have good advise. We live in Bath and so far no problems climbing up the hills, although I don't know about long term reliability. I went for the down tube battery , although I still have to attach the front mounting point. I really don't want to drill into the frame so I'm working on a cable tie as it seems pretty secure even with the back two.  The acceleration is quite addictive and I have taken to using my tandem even when riding solo!   Cheers John

Michael Holley2021-03-02 09:40:38

Hi all, as I started the thread I thought I may have some useful info for anyone using the whoosh conversion. We've just fitted a front wheel whoosh kit to our 10 year old Viking Tarantino after a lot of email correspondence with Andy at Whoosh, who was very helpful. We bottled out and got our local bike shop to fit the kit as he volunteered, and I'm glad I did. We didn't have enough clearance on the bottom brackets to fit the l/h pedelec sensor, so had to fit a new bracket with longer shaft supplied by whoosh. We intended to fit it to the front bracket to save disturbing the rear one with the 3 cogs on the r/h side, as our bike shop worried that if the cogs were moved outward then the gear change mechanism wouldn't have enough adjustment. The only problem after fitting the longer bottom bracket to the front pedals was that the pedelec sensor which pushes over the pedal shaft fouled the eccentric casing. The sensor supplied had the cable leaving the sensor at right angles to the disc, unlike the ones in their literature which have the cable exiting parallel to the disc. This is fine on a normal bike, but our tandem has an extra housing at the front which holds the eccentric casing which enables you to tension the front chain. The bike shop therefore tried fitting the extended bottom bracket to the rear pedals, which worked and we now have an electrified tandem, but as suspected there isn't enough adjustment to enable us to select the large 3rd cog for top gear. We have done 30 miles so far and we are very pleased with the power to get us up hills we would have walked up before, even with the lower torque front hub motor. However we are now waiting for an-in line pedelec sensor ordered on Amazon, to see if we can fit it to the front bracket and restore our top gear ring to operation. Whoosh no longer stock the in-line exit sensor although Andy did tell us where we could buy one. So I'm glad I left the installation to the bike shop as there has been a lot of faffing around and splitting of cranks, and more to come. Hope that all makes sense and is useful to someone. Picture of the right angle exit sensor on the rear bottom bracket attached. Mike.

Lawrence McPhillips2021-03-02 10:27:19

Chaps, great feedback - thank you.


John, in my rooting around for information, I came across this site in Canada - they seem to be real enthusiasts and able to deal with 'real world' issues.  I'd like to use the boom-tube on my bike for the battery if there is sufficient space.  I don't yet have my Woosh kit, so I can't check, but using a cardboard template shows that it will be very, very tight (the 'normal' mounting place on the bottle mounts will be fine though).  We have the smallest Orbit frame (18" / 14") on larger sizes I suspect the boom tube would be fine.  I don't want to drill any holes either, so this item really appeals to me:


it might be useful for you too.  Their videos are very clear at explaining things so have a look.

As I mentioned, I'd be a bit less concerned with torque arms on a steel frame, but alloy can fail very suddenly and catastrophically - better safe than sorry.  The width of the dropouts on our Orbit are only 10mm - 11mm.  Plus, I think the nominal diameter of the hub motor axle is 14mm rather than the nominal 10mm diameter of the standard set up.  That will move the axle out of the drop outs by approx 2mm (it will also move the brake disk down too, but that's an issue for another day). Having a chunk of 5mm or 6mm steel to fully secure the wheel is my plan.


Mike - my partner is from Keynsham so we're familiar with the terrain in Bath.  We're in Edinburgh, which has no shortage of hills or strong headwinds so it's good to hear that you're happy with the motor performance.  I don't know if these hub motors have any kind of thermal rollback protection built in, but I'd have thought that simply including a thermistor output from the motor to the handlebar display would have been an easy and effective way to let the rider know if the motor was about to 'cook'.

That's interesting to hear about the pedal assist sensor.  On the face of it, I thought I'd have plenty room at the front but I'll see when the kit arrives!  Looks like I may have the same issue. Both my bottom bracket axles are 122.5mm, so there is an option to go up to a 127.5mm if needs be.

I'm sure your LBS considered it, but is there no scope change the front derailleur to increase the 'throw'?  Paradoxically, I've found that the lower price Shimano components often give you more 'wiggle room' than the more expensive stuff.  For example, when I upgraded the drivetrain on my old MTB, I fitted a Deore FD - it didn't shift out far enough to engage the third chainring, but swapping it for an Alivio FD worked perfectly.  May be worth asking the question?

I have noticed a few inconsistencies in the information on the Woosh web-site and manual, but they do have a good reputation and I'd rather buy my bits and pieces from them than some anonymous internet source.  I think they are snowed under at the moment with a huge increase in demand for bikes / kits as a result of the pandemic.


I'll let you know how I get on when my kit arrives.

Michael Holley2021-03-02 12:20:44

Thanks Lawrence, I actually live in the Vale of Glamorgan but to leave our town involves steep hills in some directions, not quite as hilly as Bath. On our test rides on the flat we've been running at the lowest assistance 1 as we don't need the power and there's less whirr from the motor, then bump up the assistance when we reach a hill etc. You can hear the motor working hard when going very slowly up a steep hill at max power when we're also pedalling hard in bottom gear, I hadn't thought about overheating, until now! I may feel the motor when we get to the top of a hill next time we're out, but I assume the kit is designed for it. I'll put your suggestion of another change mechanism to our bike shop, and we'll discuss which is the easiest option when I deliver the new sensor, which should be arriving any moment on the Amazon van.