Cycling UK Forum

I have a c1966 short wheel base, kiddy back, lugless, Claude Butler tandem. It has kiddy cranks fitted and I want to change to adult cranks. Does anyone have some advice on this. I think I need left and right cottererd cranks with five pin spider. I might also need crank shorteners. Please see photos attached, thanks
Oliver Brookes
Edinburgh

you would possible be best advised to get a new bottom bracket bearing/axle and fit a square taper crankset - await the expert advice (from Brucey et al)

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Hilary Stone has some vintage cottered cranks here. You could also ask the Tandem Club.

Thanks for the help. The tandem does have a front changer, and I was hoping to keep the feel of the vintage set up, so I am reluctant to swop all the kit and go to taper square bottom bracket. It looks like the Hilary Stone site might have the answer, there are a couple of cranksets that looked right. I'm not sure about crank length though, I guess I might need some crank shorteners, they do look a bit clunky though. Any more thoughts very welcome, Oliver

the way that drive is configured, you will have to change the chainline on something in order to get it all to work, I'm not sure quite what the best way ahead would be there. You won't be able to retain the same timing chain chainline and retain the original rear BB, for example.

There are (were) several types of steel cottered cranks that accept TA chainrings; if you are very lucky you will find a set that you can use. However if not, the knock-ones might be that as well as a new rear crankset, you might need a new front crankset, new BB axles... basically the whole shooting match.

Note that vintage tandems can run weird chainlines and weird BB shells too. You may well find that the BBs that you have are very difficult to replace now.

BTW I have an idea that if the front crankset runs the correct chainline for the timing chain, you might be best off to swap that into the back (BB and all) and use that as a rear crankset; hopefully there should be enough room on the inside for the new timing chain position. You might be left with a 1x drive to the rear though.... if you want a 2x or 3x drive to the rear then I would suggest a crossover drive instead.

Since cotterless cranksets were available in 1966 you could fit those quite legitimately....

cheers

Both Stronglight and Milremo sold cottered cranks to take 5 pin TA chainrings. They come up regularly on ebay and also on Retrobike. If you are interested in originality then either of these are probably your best bet.

Cotterless cranks of that period would probably have been TA or Stronglight 49D. Either would be in keeping with the Claud Butler.

If you have a non-standard bb, check the tandem club who sell shims to resize to modern bb.

LollyKat wrote:Hilary Stone has some vintage cottered cranks here. You could also ask the Tandem Club.

This link from LollyCat shows some five pin Milremo cranks that look like they might do the job, Robc02 suggests they will fit, hopefully I can keep the same set up with all the drives on the same side. Thanks for all the helpful advice, Oliver

OliverBrookes wrote:.... hopefully I can keep the same set up with all the drives on the same side....

I am not at all sure that you will be able to do this, not without compromise/more work; at the moment that timing chain position would clash with any RH rear crank (if there was one) on that BB spindle. To my mind this may leave you trying to fit the timing chain inside the rear drive chain (and then it won't line up with the front...?) and even if you do this, it may also deny you two rear chain chainrings/front mech etc.

If you have a plan to avoid this, great. If not, do post some photos and maybe someone will have a good idea.

cheers

So you think the RH crank will foul the timing chain and ring, it does look pretty close, but I might be able to save 1mm with a change of washer so I think I'll take a punt on the Milremo cranks. Not sure what to do if that doesn't work, probably put the kiddy cranks back on and wait for my daughter to have her own kids, thanks again Bruce