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Help us identify our frame

Joseph Chant2020-09-13 12:00:15

Hi, my friend and i are currently working on building up a tandem frame we bought on a whim.

We have no real idea what it is that we've bought, nor did the guy we bought it off.

There are a few numbers that we've found but they haven't been helpful so far, perhaps someone might be able so shed some light on them

4532 - Mech Hanger

81920 - Rear Dropout (Right)

X123X - rear of fork crown, only found after it was repainted, first and last completely unreadabe, the 1 is the only digit i'm 100% sure on.

It takes a 1 1/8th threaded headset if that helps.

We'd love to know what we have, so that we could find a badge for it, so if anyone could help us out that'd be amazing.

Joseph Chant2020-09-13 16:54:56
Joseph Chant2020-09-13 16:56:21
Peter David Koch-Osborne2020-09-13 19:08:06

Regarding identifying the blue tandem frame I would guess at a 1937 Sun tandem.  Why 1937?... because this was the pre-war peak of tandem production and the frame geometry looks right for the period.  Why Sun?... well, I used to run the Tandem Club's Register for old (mostly pre-war) tandems and the only make I came across with a short piece of 'drain-pipe' (the thick bottom tube) behind the rear bottom bracket was a Sun.  In fact I had a Sun for a short time as well as my Hetchins tandem.  No guarantee of course but very interesting as I only rejoined the Tandem Club a week ago after a lapse of over 15 years!  Cheers, Peter Koch-Osborne.

Stephen Gray2020-09-14 21:34:55

I have a Freddie Grubb tandem which also has a "drainpipe" section behind the rear b/b but I think Grubb tandems have the frame identification number at the bottom or top front of the heas tube. Can't remeber which and mine is in the garage loft at the minute waiting for me to have time for the project of re- building it.


Chris Beeching2020-09-15 11:11:56

I'd also put my money on this being a Sun. Most of the other tandems of the same period had chainstays going straight into the rear of the rear bottom bracket. I only ever saw (and had) a Sun with the 'rear drainpipe' feature.

2020-09-15 15:42:05

My Sun wasp of 1950/51 has the marke on the nearside captains seat lug. RT316. I believe R is the date letter. T for tandem and 316 the serial number. The giveaway for mine is the forr pedal lug on the drainpipe.

Here's a pic from the Sun 1938 catalogue I dredged up some years ago. Can't make out whether the rear drop outs are rearward facing-not on mine.


Joseph Chant2020-09-18 09:31:14

Thank's for the help so far, here's a better picture of the rear dropout, rear facing, which is something that i haven't found an example of online.

Michael Hughes2020-09-18 11:55:55

This type of rear dropout is similar to the ones used on the roadster bicycles of my distant use. They were paired with a screw fitting which allowed adjustment to take up chain wear. I would expect to see the ends of the dropouts to be slightly thinner than the main part of the dropout

This type of droput, with adjusters was favoured  on frames for single speed fixed gear rear wheels.

I can supply a photo of the adjuster if needed. Michael