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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.

cheers

John

Michael Holley2021-02-22 15:14:54

Thanks for your info John, very useful. 

Regards,

Mike

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.

Cheers,

Lawrence

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!

Chris

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!

Chris

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:

https://ebikes.ca/shop/electric-bicycle-parts/battery-accessories/triple-bob.html

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.

Mike

Lawrence McPhillips2021-03-09 09:31:30

Folks, a bit of an update on my experience converting our Orbit to an e-bike. I took quite a few photos during the work, but I can’t see an easy way to include these unfortunately.

 

The main reason for installing electric assist was to provide some help on the steeper hills. I had wanted to fit a mid-drive motor as from what I could gather, a mid-drive motor is a better option in this case. Fitting a mid-drive motor to a tandem does not seem to be a straightforward task, so the next best option seemed to be a rear hub motor. I had discounted a front drive hub as I had some concerns over the weight of a hub motor and the possibility of putting too much load on the forks.

 

I too bought my rear hub kit from Woosh and followed their advice to go with the DGW22C kit as the preferred option for tandems. I’m reasonably competent mechanically, so the DIY option appealed to me.

 

I made ready for a day fettling in the garage. I had already removed the rear mudguard and luggage rack for better access. The first bit of good news was that the battery unit will fit along the boom tube – more on that later.

 

As per the Woosh manual, I started off with the Pedal Assist Sensor (PAS). My favoured position was the RHS front bottom bracket. I had a brief look at the proposed layout and found that the cable supplied was just fractionally too short to reach the battery. Fitting the battery ‘back to front’ in the frame meant the PAS cable would reach but the motor wire was then too short. Woosh sent me an extension cable for the PAS – great! As part of an annual ‘major service’ on my bikes, I routinely remove the BB’s and re-apply anti-seize compound to the threads in the frame and cups, so extracting them was not a problem. It looked like the PAS would be a perfect fit on the front, but unfortunately it interfered with the eccentric shell on the front BB – this was really frustrating as it would only have to move about 1mm further out from the BB shell to clear – bugger! Ok, time for plan B. There was enough room on my rear RHS BB to fit the PAS, so that is where it is now mounted and is pretty much invisible when the crankset is fitted. I also chose to fit a throttle as hill starts on a tandem can be difficult and being able to call on instant power might prove useful. That meant installing the brake cut-out sensors.

 

I moved on to the wheel next. I didn’t bother changing over the cassette from the existing wheel, I just fitted a new one. We have three bikes in the household which have Shimano 9 speed 11 – 32 cassettes, so I had one in the spares ‘stock’ anyway. The existing cassette is a 12 – 36, but I hope I won’t miss the slightly lower bottom gear now I have the motor. I fitted a new chain too – the existing chainrings are all in good condition so they’re being kept. When fitting the wheel, a couple of issues emerged:

The hub motor has a 12mm axle and a normal Shimano cassette tool won’t fit over that size. As the tool is made from hardened steel, I didn’t think it was worth the hassle of de-hardening it then drilling it out to fit over the axle. My Unior emergency tool for roadside removal of cassettes was pressed into service and it did the job.

https://uniortools.com/eng/product/1669-4-2-in-1-pocket-spoke-and-cassette-lockring-tool#44729

Another other option would have been to use ‘farmboy’ engineering and stick a pair of needle nose pliers into the lockring, then turn the pliers with an adjustable wrench (there’s always a way!). A deeper socket style lockring tool with a ½ inch square drive would have been fine as it could fit over the axle. I’ll add one to the toolkit for future use. I believe lockrings are meant to be torqued up to 40Nm, but I’ve never had an issue with one coming loose although I only tighten them until I feel a bit of resistance and hear a couple of clicks from the lockring – that makes taking them off a lot easier too!

 

A quick test fit of the hub in the frame brought more good news – the axle was a good snug fit in the dropouts and only a few spacers / washers either side would be needed for a perfect fit. Most tandems have a larger OLN dimension than solos at 145mm. Similarly, the rim looked pretty much dead centre in the frame – great. I started off checking the disk side of the hub and found that the spacing for the disk was dead on – I’d removed the brake caliper, to make fitting the wheel simpler but it bolted back into place exactly where it had been. As the axle is a larger diameter, the disk has been moved down about about 1mm away from the caliper, but this unlikely to have a significant effect on the swept area of the brake. I may yet remove some material from the IS mount to compensate and realign the disk in the caliper.

 

Next was the drive side and an issue emerged here. The OD of the supplied washers was just a fraction too large to clear the cassette lockring and butt up against the cone nut. When I tightened up the wheel nuts, this washer was compressed in to the small gap between the cassette lockring and the axle and was binding slightly. I had to make up a couple of spacer washers to fit. I could have removed a small amount from the supplied washer on the bench grinder which would have worked just as well and in retrospect, would probably have been easier. As an aside, there is very little drag when freewheeling – perhaps fractionally more than a normal hub. I know geared motor hubs have clutches to allow for this – I assume they are the ‘sprag’ type.

 

At this point I deviated from the normal installation routine as I wanted to fit torque arms to the bike. I sourced a set on ebay although I probably should have asked if Woosh supply them. I had intended to use these as a stop gap and make up my own set, but they look sturdy enough so, I’ll just keep them. The Orbit frame is alloy so I thought it would be prudent to try and distribute the loads of the wheel more evenly on the frame. I used some 5mm and 3mm steel arms. They’re attached to a brake caliper mounting on the non-drive side and a mudguard mount on the drive side.

 

At the moment, I’ve used a few washers to get the correct spacing for the torque arms, but I’ll make up some spacers in due course. The motor connector plug is small enough to fit through the torque arm on the drive side. I’m happy knowing that it is now very unlikely that the hub axle will spin in the frame. I’ve added some extra hassle / additional steps to a road-side puncture repair, but that’s OK as far as I’m concerned. I have a neoprene chainstay protector which fastens with velcro and is large enough to allow it to be wrapped around the motor cable. This keeps the cable secure and avoids the need to zip tie it to the frame.

 

With the wheel now firmly bolted in place, I rechecked the alignment. I fiddled about very slightly with washers / spacers, but things were largely OK. Surprisingly, the distance between the hub flanges on the powered hub is quite a bit less than the original (tandem specific) Shimano FH-HF08 hub. The Shimano is 51mm, the new hub is only 38mm. The wheel is significantly dished on the drive side, although hopefully this is probably not an issue with 12 gauge spokes! Woosh seem to have the wheel build dead right – either through luck or judgement. Since they’ve been selling these kits for a while, I suspect the latter is the case. The wheel is laced in a twin cross pattern and was completely true as supplied. I’ll see in due course how this fares after a few miles – I’d expect a bit of twiddling with a spoke key after the wheel has seen use.

 

The rim is a ‘no name’ with a 25mm internal width (so quite wide). We tend to use wider tyres on the tandem anyway for a bit more cushioning / comfort, so that isn’t an issue. We’ve got 42mm Schwalbe Marathon Supreme fitted at the moment. They’re not as puncture proof as the Marathon Plus, but they are half the weight, comfy and roll very easily. More on tyres in due course.

 

I located the battery unit on the ‘boom-tube’ rather than the down tube as it keeps the weight as low as possible and helps centralise the mass. There are no bottle mounts on the boom-tube and I was not keen on drilling holes to fit rivnuts. Grin Technologies in Vancouver offer a useful alternative: https://ebikes.ca/shop/electric-bicycle-parts/battery-accessories/triple-bob.html

I bought one of these and it provides a very secure fit for battery unit.

 

Finally, I fitted the handlebar control unit and connected everything up. It all went together perfectly and everything worked without a hitch. It may be possible to source these kits via the internet, but I’m happy to have access to a UK supplier to call on for product support / guidance. The fact that the new wheel fitted straight off and all the electrical items worked instantly counts for a lot with me, so credit to Woosh for supplying decent stuff.

 

Riding experience:

We’ve only done a total of about 40 miles so far comprising of two 20 mile trips, but the experience is overwhelmingly positive. One steepish climb of about 1 mile, which normally requires the use of the granny gear (18.5”) and can see my pulse rate hovering between 160 and 170, was accomplished with ease. The assistance level was set at level 2 (of 5) and we just sailed up the hill at our normal 90rpm cadence. At one point during this maiden trip we got an error message 25 (brake sensor) and lost power but switching the unit off and on again cleared the fault and it has not recurred. Our first trip of 20 miles used up two (of five) of the battery charge indicators, but that included some quite steep ‘test’ climbs and a long uphill drag of about 7 miles. Most of the time we used level 1 or 2 assist. I didn’t charge the battery when we received it from Woosh, so although it showed ‘Full’, it probably wasn’t completely topped up.

 

When we returned from our first trip, as I was putting the bike in the garage, there was a bang (like a gunshot) and the rear tyre deflated. The inner tube was shredded and had obviously pushed the tyre off the rim. The tyres are 40mm Schwalbe Marathon Supreme. These are folding type tyres and were a very loose fit on the rim when I mounted them. On the tandem, we tend to inflate the tyres towards the upper end of the limits. I then tried a 38mm Schwalbe Marathon Plus on the rim and even the Marathon Plus (a notoriously difficult tyre to fit) slipped on the rim with only light finger pressure. When I started to inflate the type, I got the same ‘bang’ at about 75psi and bits of tube scattered round the garage! I fitted another tube and dropping the pressure to 60psi was fine. For the avoidance of doubt, as far as I know I fit tyres correctly. I put in about 10psi and work my way round the rim squeezing the tyre to ensure the tube is not trapped and that the beads are fully seating in the rim, I do the same check at 20psi before inflating to full pressure. In decades of cycling, I’ve never experienced this before. In fairness to Woosh, I would not expect them to supply a top quality rim for the amount they charge for the kit, just a pity my rim is clearly at the small end of 700C size tolerances. I’ll probably change it out for something like an Andra 30 or a Sputnik built with Sapim Strong spokes in due course.

 

Before our second test run, I had fully charged the battery and we set off to climb some steep hills and some long uphill drags. The extra assistance from the motor is excellent and we just romped up hills that we would have either avoided altogether or dropped right down to the granny ring. Again, we only needed level 1 or 2 assistance. One thing which is very useful is having the motor power when pulling away from rest (sometimes an awkward task on a tandem) or when constantly slowing down / stopping for inconsiderate pedestrians / dog-walkers on shared cycle paths. We covered just over 20 miles and the battery display was still showing ‘Full’. For our pattern of use, the anticipated range will clearly be much greater than we expected. We bought the kit to help, not to replace, our own efforts on hills and headwinds. Most of the time we were above the speed limit for level 1 and 2 assist, so the battery was not being used much. Still, both the power and the range are better than I expected.

 

Our tandem weighed 21Kg as delivered, 23Kg by the time a suspension seatpost and other bits were added. In current trim, with the motor, battery and so on it weighs 32.5 Kg. Riding without the motor assist feels like you would use 1 gear lower than a ‘normal’ machine – perfectly acceptable to me.

 

If you have been considering such a conversion and have been swithering, I’d say go ahead and do it. The fear of headwinds and hills disappears and it certainly opens up more options for getting out and about.

Michael Holley2021-03-11 10:50:09

Just to finish off my contributions as I kicked off this forum string, our Viking Tarantino is now electrified and we're pleased with the riding experience. The assistance from the front wheel motor kit supplied by Whoosh allows us to pedal up hills we would previously walk up. It's early days but it seems the kit is a success. As per previous posts once the correct pedelec sensor with cable exit in line with the disc arrived from Amazon I took it back to the local bike shop, who fitted it as intended to the left side of the extended front bottom bracket supplied by whoosh. The original rear bottom bracket was fitted to the rear crank which restored the gears to what they were. So there was some extra work due to having the wrong sensor supplied by whoosh, and I have told them about this when supplying kits for tandems. Piccy of the final installation attached. Mike

Lawrence McPhillips2021-03-11 11:23:28

Thanks for the update Mike.  I agree that the extra oomph from the electric assist makes a big difference.  It's well worth doing the conversion in my view.

I took lots of photos during my work, but I can't find a way to insert them :(

I put the battery on the boom tube rather than the down tube as I wanted to keep the extra weight as low as possible, plus it make the 'normal' mounting point available for a second battery if range becomes an issue!

I've decided to relace the rear wheel with Sapim Strong spokes and a Ryde Sputnik rim as the supplied one is just too small for my liking.  I've done a bit of internet browsing and the issue I mentioned of 'loose' tyres has cropped up previously.

Finished conversion:

 

Michael Holley2021-03-11 14:05:55

Thanks Lawrence, I'm very impressed with your ability to respoke a wheel and get it true, I think I'll leave that to the professionals. By the way the tyre on our new front motor wheel also blew off while standing in the bike shop, no damage and it was refitted but nearly gave the owner a heart attack, although he has had other ones blow off in his career. I have informed Whoosh that they may like to consider a heavier duty rim for tandems.

Happy pedalling, Mike

Lawrence McPhillips2021-03-11 16:08:28

Hi Mike,  I cannot tell a lie - I have a good wheelsmith at my LBS.  He'll be the one respoking the wheel, not me!  He trued up my previous rear (unpowered) wheel and it was good for many miles, with just minor adjustments from me.

The two issues with the Woosh wheels that I can see is that they seem to come up quite small in size and are wide at 25mm internal width.  That means you really don't want to fit a tyre any narrower than about 38 - 40mm.

Not a problem for you with your front hub motor , but the rear wheel hub motor I have is only 38mm between flanges and this requires a lot of dish for the drive side.  Accordingly, the non-drive spokes have to be really rather slack.  I've not checked it yet, but I think the ratio of tension between drive side spokes and non-drive side is around 90% versus 10%.  Not exactly a great balance.

A wider flange rear hub (but not 'fat bike' wide) would be better for tandems, but we're such a small market, I doubt that will ever happen.

More power to your elbow - or pedals :)

 

Lawrence

Lawrence McPhillips2021-03-16 16:14:02

Mike - I was looking for bits and pieces for another bike and stumbled across this adapter.

If you have not yet resolved your issue with the front derailleur, this might be just the job.

https://www.sjscycles.co.uk/gear-spares/thorn-eccentric-front-mech-shim-286-to-349-black-plastic-hand-finished-split/

Lawrence

Michael Holley2021-03-17 08:39:11

Thanks Lawrence, the gears work fine now that the longer bottom bracket and correct pedelec sensor were fitted to the front pedals, and the original bottom bracket fitted to the rear pedals which restored the gear rings to their original position. However thanks for the suggestion and it may be useful to someone else doing a similar conversion. No stopping us now, makes a change to overtake other bikes going uphill, it used to be the other way round.

Mike

Chris Allen2021-04-19 23:40:20

Having recently taken ownership of a very similar bike to Lawrence's (Orbit) and reading his comprehensive e-bike conversion selection process, installation and encouraged by his emails, I finally decided to follow his lead. Reading his and others' assessments on the Internet and watching dozens Youtube videos about the pros and cons of hub vs mid-drive motors I came to the conclusion that there really isn't a 'better one'. Both types have strengths and weaknesses. So I went for what felt would be best for us; a mid-drive. My main justification was that being very new to tandems and with limited experience, if we subsequently decided that it wasn't for us, I'd be able to re-install the motor on my solo bike and whiz around on my own. Hardly the best technical reason I know, but it reduce my anxiety about spending £600+ on an old bike. In fact, I did install the kit first on my solo bike to gain experience, before installing it on the tandem.

The good news - it's working!. We went out on our first proper ride today (27 miles around Richmond Park and Wimbledon Common - the full gamut of hills, traffic, quiet cycleways, people, animals and tracks).

The bad news - it so nearly didn't. Unlike ready made electric tandems, an e-kit motor (TongSheng TSDZ22) fits in the stoker's bottom bracket (sounds slightly kinky!) which, of course has a chainset on both sides, between which the motor has to sit. I hadn't measured the width of the motor before I bought it. The motor slots very simply through the right side of the BB, but when I came put the left hand chainset back onto the spindle, it wouldn't sit fully back on as the motor was 3mm too wide. My heart sank! But after carefully grinding (2mm from the inside of the chainset) and by adding a tiny shim to the crank, to move the LH crank out by about 1mm, I managed to get enough clearance between the motor casing and the chainset to allow the pedal to rotate. Phew!

You'll see from the photo that we've got a large battery (20AH) and to be honest I've over spec'd it. It's excellent but bigger than we really need. Judging by today's trip we should be able to do 100+miles on one charge. I painted it silver to make it less conspicuous.

Like Lawrence and others have said, the riding experience is a delight. Its a torque drive so the motor kicks in whenever the stoker puts pressure on the pedals. Getting away from a standing start is such a breeze now.

Thank you Lawence for all your encouragement, and I'd say to anyone considering e-converting your tandem - do it and if you go for a mid-drive, make sure the motor will fit between the stoker's chainsets before you buy!

Lawrence McPhillips2021-04-20 08:58:18

Hi Chris - that's great news about your installation.  Well done for sorting out the problems you encountered with the mid-motor conversion.  I agree with you that there isn't really a 'better' option for the type of motor as they each have their individual strengths and weaknesses.  In my view though, any of them are better than human power alone.

 

In my opinion, the aftermarket kits have now reached a level of maturity such that they offer a real alternative to the ‘proper’ factory produced versions. In the case of your conversion Chris, I’d be surprised if spending several £000’s on a new e-tandem would give you a significantly better machine than you now have.

 

If anyone is contemplating fitting a conversion kit, I would say go ahead – you’re unlikely to be disappointed.