Tandem Conversion: 1st questions

GreySpike

Just Joined
Sep 23, 2021
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I want to add some assistance to a 2006 Dawes Double Edge tandem, 26"x1.75" MTB style wheels with disk brakes, triple stokers derailleur and 9 speed rear cassette, as my wife and I are approaching 60 and starting to find hills more taxing, especially starting off on a hill. We generally cruise with 2 front 6/7/8 rear; 1F for uphill, 3F for downhill.

It is by far used for short local trips of up to 30 miles, but I am hoping that we might do more of longer rides with a bit of assist available, for example to visit parents 90 miles away that we used to do.

It will be UK legal, despite the kid in me wanting to max out!

Budget is limited.

First question is front, mid, or rear?

From my reading so far:
Mid would be best, but I can't think of a way of maintaining the front(stoker) derailleur and rear cassette; getting the same range with 1X set up is going to end up changing the mech and shifters, which is likely to break the budget.

Rear seems to be 2nd favourite but there are comments about having to change the cassette which I don't fully understand, and that is a lot of traction to put down through one tyre.

Front seems least favourite, but mostly because of concerns about weight distribution, handling and traction, but seems much easier to install.

At the moment front hub is at the top of my list primarily because of the ease of installation, plus I think converting a tandem mitigates the issues around weight distribution and traction somewhat, especially if I can mount the battery pack lowdown between pilot and stoker. Plus it keeps the wiring shorter.

Before I get into detailed research on front hubs, can anyone point out the obvious (to you) flaws in this thinking?
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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There are two members who have added a Woosh kit to their tandems, can't think who they are off hand. However using the search part of the forum may bring up details.
 
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sjpt

Esteemed Pedelecer
Jun 8, 2018
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I'm one of the tandem owning members Nealh mentioned; with a front Woosh XF07. 3 trouble-free years so far, rides mostly under 20 miles.

As you suggest, front hub traction is less of an issue on a tandem because of the different weight distribution. We mainly do on-road with fairly simple off-road. The front hub has helped several times going up slippy (not too steep) grass slopes; the rear wheel slipped under our pedal force, but the front motor wheel kept traction. Two wheel drive rather than the one wheel drive on mid or rear motors. (Marathon Plus are brilliant, but not good at slippery grass.)

If you go for rear wheel, as long as a rear wheel kit has a cassette and your tandem does there shouldn't be any problem swapping the cassette over. For some odd reason even though most bikes today use cassette rather than freewheel, many rear wheel kits still come with freewheel hubs; that's probably what people have suggested as the problem.

The XF07 is not ideal for a tandem, definitely underpowered. Woosh warned us before we bought, but there was no sensible legal 700c alternative available at the time. It gives us lots of help and gets us up several hills we couldn't manage otherwise, but we still need to put in a lot of work. We certainly wouldn't like to lose our bottom gears, but the motor is struggling and losing efficiency when our speed drops. We almost never use top on the front. (We average over 70 years rather than approaching 60)

Torque sensors are best for hill start with more instant power, but I understand cadence sensors are improving; some kick in at 1/4 pedal turn.
 

Jodel

Pedelecer
Oct 9, 2020
65
39
OP, we are slightly older than you and went through exactly the same reasoning for converting our tandem. My first comment would be whatever system you choose, you’ll love it. It makes life so much easier. You will find convincing arguments for all three drive systems and in fairness, all three types have their advantages and disadvantages.

I’m another Woosh customer who fitted one of their kits to a tandem. We followed the Woosh advice to go with their DWG22C rear hub motor kit and it really is first class. I think it has the highest torque output in the Woosh range of kits and it can easily cope with the mass of a tandem and crew.

We’re a relatively lightweight team at about 130Kgs. The tandem with hub motor, 48 Volt 12Ah battery and hefty Schwalbe Marathon Plus tyres (40 x 700C) is now about 35Kgs. We live in Edinburgh which has no shortage of hills or headwinds, but the motor assist means that we can go where we want rather than having to take the ‘easy’ route.

Our kit has cadence sensing and this works well for us. For example, if you are on a cycle track and baulked by inconsiderate dog-walkers / pedestrians etc and have to keep slowing down / stopping, rather than having sore knees as a result of constantly having to accelerate back up to speed, the motor just whisks you effortlessly back into the cruise in no time.

It won’t turn your tandem into an electric motorcycle, but hill-starts (never easy on a tandem) headwinds, long uphill drags just aren’t a problem or an issue anymore. We still put in a fair bit of effort ourselves, but the motor takes away that feeling of ‘peddling through treacle’ which you can get on some days! We generally only use power levels 1 or 2 (of 5) but it is reassuring to know that if you are having a bad day, you can just turn up the power level and let the motor help.

Our kit kicks in power after just ¼ turn of the pedals, but the simplest way I’ve found to start off from rest is to:
1) apply the rear brake (we have power cut-off sensors on the brakes).
2) open the throttle fully
3) when the lights change / traffic clears, release the brake, the motor immediately kicks in and off you go.

It makes hill starts (or any start) much, much easier on the old legs and knees!

My installation experience is in this thread if you want to read it: https://www.pedelecs.co.uk/forum/threads/orbit-tandem-woosh-dwg22c-48v-rear-hub-kit.40584/#post-606994

Based on my (limited) experience of e-biking, I’d certainly recommend a rear-hub drive for tandem use and I actually bought another one of the same kit for one of my solo bikes too. It’s not perfect, but it has meant we use our tandem much more than would otherwise have been the case. Despite some health issues, we’ve done about 1,500 miles so far this year and there is no way we would have managed that without the electric assist.
 

GreySpike

Just Joined
Sep 23, 2021
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I'm hoping that the Bafang BPM at 50Nm will be adequate as the XF07 is rated at 42Nm.

Of course the DWG22 that Jodel fitting has 60Nm.

I am concerned about hill starts, but a couple of people have mentioned the procedure that Jodel mentions so it seems it is not an big issue in practice.

Jodel, it was reading your thread that pushing me into action a week or so ago, though I don't think I have your mechanical expertise, hence considering the front hub option as an easier job.
 

Jodel

Pedelecer
Oct 9, 2020
65
39
GreySpike, I think I'm fairly competent with the mechanical side of things, but if you are moderately capable of twiddling a spanner, I think you'd be fine with fitting a rear-hub kit.

I added some extra steps to my tandem conversion which were probably not strictly necessary. For example, changing over the rim for a Ryde Sputnik was a step which could have been avoided. The wheel that Woosh supplied was really perfectly adequate, I'm just an inveterate fiddler!

Incidentally, my 'new' hub kit which I bought for a solo bike, I ended up fitting to the tandem as a test bed. My reasoning was that if it can stand up to tandem loads, then it will be fine. That was 250 miles ago and the new hub and rim are still spot on and running true. I've no plans to swap it over to the solo which now has the 'old' wheel from the tandem on it.

Another thing to keep in mind is that you'll only go through the hassle of fitting the wheel once and you'll have to go through all the other steps with a front hub anyway:
Fitting the PAS
LCD display
Battery mounting
Brake cut-outs (I'd definitely fit those)
Throttle
Torque arms (perhaps not absolutely required, but I'd certainly fit them - or at least one - if yours is an alloy frame)

Looking at it like that, there is very little effort to be saved in going for a front hub - unless that is what you would prefer anyway. A rear hub motor shod with a Schwalbe Marathon Plus tyre is pretty much fit and forget in my (limited) experience.

Happy to share my experiences further if you want to PM me. As I mentioned earlier, whatever option you choose, I'm sure you'll be glad you did it!
 

sjpt

Esteemed Pedelecer
Jun 8, 2018
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I agree with the various comments Jodel has made. Despite making a case that front hub is not too bad, especially on a tandem, I still think that rear hub is probably (*) preferable.

(*) I've never actually tried rear hub on a tandem so I can't be sure. Almost certainly quieter for the person on the front, but noise isn't a significant issue. You need robust forks for a front hub motor on a tandem.
 

Nealh

Esteemed Pedelecer
Aug 7, 2014
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The BPM is a marked as such as 350w, so the DGW22 may be a better bet.

I think Stodd was another who converted a tandy.
 

sjpt

Esteemed Pedelecer
Jun 8, 2018
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The BPM is a marked as such as 350w, so the DGW22 may be a better bet.

I think Stodd was another who converted a tandy.
I'm sjpt here (see posts above) and stodd on Cycling UK forum https://forum.cyclinguk.org/viewforum.php?f=55

The Woosh site (https://wooshbikes.co.uk/?hubkits, search down to 'WHICH MOTOR?' shows the BPM front at 250w and the BPM rear at 350w. Both at same torque; also shows front as 'freewheel'. As many people have pointed out before, it is not uncommon for the same motor to be marked with different power ratings for different markets.
 
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