Discussion of anything related to Tandems. Opinions expressed on this discussion board are those of the contributors and not necessarily those of the Tandem Club. Postings or extracts may be published in the Tandem Club Journal.
To add a response or post a new message you need to have an account and be logged in. You can get emails sent to you by enabling the Send Forum Emails tick box in your user preferences. Note you need to login to the website to add replies. See our help information here for more information.
You can add to this discussion topic using the entry box at the bottom of this page, when logged in. Login

Ancient Tandem Frame

Ian Ralls2022-10-25 23:32:21


Well, the dangers of rummaging around on EBay late at night... I've acquired an ancient, very heavy but well made tandem frame locally for not much money. Found the number ST24 under the front bottom bracket which, having done a bit of research, could suggest it's a Sun frame made in 1951. Whatever it is, it seemed like a good candidate to get back on the road, takes 26 inch wheels, so no problems there, frame and fork crown drilled for caliper brakes (no worries, we're in Cambridge and all the hills left years ago), even the rather lovely Brampton eccentric bottom bracket shell appears to take, after careful measurement, using the digital vernier caliper I finally had an excuse to buy, a 'standard' 1.37" x 24 TPI adjustable bearing cup (the fixed cup being integral with the shell) rather than the unicorn-like Chater Lea 1.45" which were often fitted to tandems back in the day, I believe. Furthermore, all of the bearing surfaces are in a fair ride-to-the-pub-but-stay-away-from-the-alps state (bottom bracket and headstock grease nipples to thank for this I think) and I can get hold of cottered axles and chainrings to make a reasonable approximation to the single sided drive I believe may have originally been fitted. All good, or so I thought, however, on closer examination with a wire brush, I discovered some bright spark has drilled a hole through one of the fork blades several inches up from the axle mount, no idea why, maybe for a drum brake reaction arm? To my mind, this makes the fork somewhat unsafe... though the hole appears to have been drilled in antiquity (several of the coats of paint appear to have been applied after it was done) and previous owners must have been quite happily hooning around on it in this state, not me however.... So, back to EBay and purchased a 'vintage tandem fork' on the off chance it might fit and miracle of miracles it does (steerer tube about an inch shorter than the original on, but this, surprisingly, wouldn't have been a problem), but, you've guessed it another (maybe the same..) bright spark had drilled a hole in one of the fork blades on this one too, his time at the top... Right, time to forget authenticity, would it be OK to use a modern decent quality mountain bike fork as a replacement? They appear to be much stronger than the delicate, graceful originals, but appearing and being are two entirely separate things.. the forks on my tandem trike are even thinner and more graceful than the holey vintage bits and yet seem to tolerate the huge side loadings the trike generates, so clearly size/thickness is not necessarily a guarantee of strength. Yes, there'll be numerous issues with steerer lengths/ threads/fork angles, bearing sizes etc to keep me out of said pub, but would mountain bike forks, in principle, be up to it? Phew, thanks for your time, off to measure some ball bearings....
2022-10-26 09:54:09

Hi Ian,

How big are the holes in the fork blades?  The original builder may well have drilled small holes (up to 3mm and possibly above) to allow for gas expansion during brazing, sometimes they left them visible, sometimes they filled them afterwards with brass spelter.  Should you be really unhappy with the holes you could silver solder a small washer around them in a similar fashion to how Tony Oliver, for example, ran internal dynamo cables.  Easyflo 2 silver solder is liquidus within the range of a fairly standard swirl flame gas torch.

You sound like a fairly handy guy, we have modified oversized FSA mountain bike headsets to fit pre-war vintage tandems, however, we have never had to resort to using solo forks of any description.  We do have a set of 1930s vintage forks and a load other spares (bottom brackets etc.) should you want them.  Free of charge, collection. (forks picture attached)

Pippa and John

(South Nottinghamshire)

Chris Beeching2022-10-26 11:43:47
I don't think I would ever advocate using solo forks on a tandem. The stresses and loads carrying, steering and stopping two people are considerably higher than for a solo. I'm sure there must be some tandem forks lurking in the sheds of the tandem club membership somewhere if you're really worried about the hole. My advice would be to strip it right back to bare metal and have a proper look. 
Ian Ralls2022-10-26 13:14:23

Thanks for the help folks, was wondering about how safe solo forks would be and now will be looking for proper tandem ones. Was suggested to me that chrome moly steel ones would 'probably' be OK, but how you tell that from 'ordinary' steel is beyond me (taste, perhaps...? lol) and 'probably' doesn't make the gutter taste any better...

I've attached a picture of the forks and accompanying hole; suspect it's a bit larger than a brazing blow-hole, definitely in the 'yikes' category,but this suggestion was my first thought too. I've counted five coats of paint so far.....

Pippa and John, thanks very much for the kind offer of the forks and other bits, unfortunately 100% bicycle atm, so picking them up would be a challenge. Happy to pay postage and a donation to charity/your time...? Hmm, me a fairly handy guy, why thank you; have hammers will travel :)

2022-10-26 14:45:39

Hi Ian,

Have just seen you photos, so obviously they are not brazing vent holes!  You might consider putting low rider braze-ons right through the holes and then silver soldering them in place.  The kind of braze-ons supplied to Blackburn racks were, by some builders, drilled through the forks.  Although we would never advocate this it does happen. 

Quite understand that you are unable to collect parts, we wouldn't consider posting them as this would certainly not be cost-effective due to weight and size.  However, if you're still struggling later on we may be able to deliver and combine it with a trip out.

Pippa and John

Ian Ralls2022-10-26 17:58:01

No... the hole(s) are a bit generous aren't they...., maybe an attempt at lightening the whole plot...., though removing some of the paint could probably have saved a couple of pounds....

Thanks for even thinking about a trip out to deliver the bits :)

Right, to EBay there's bits to locate!


Ian Ralls2023-12-04 14:36:30
Remember me....? He of the ancient tandem frame from EBay with the holey forks... Well, having spent over a year occasionally looking for appropriate forks, finally came up trumps with not one, but two sets of vintage tandem forks for the grand total of.......£3 (plus £11 postage, but that doesn't count...). Would have got them for 99p(!), but my attempt to add a minium bid of £3 to my offer led to me bidding against myself... ho hum. No holes this time, unless you count the extra (mudguard?) mounting he drilled in the crown of one of them, the only slight issue being that both of them came without crown races. Back to EBay where the fine gent (and reason for this post) who is TurfMoor1958 (Martin) came up with the correct unobtainable Brampton crown race and also threw in another one for free with the compliments of the Tandem Club. Many thanks to both him and the club for making te project viable again!