Tube Type &Gauge For Frame Repair??

[Peter Gee]

Hi Guys,

I have to replace a section of my 57 A7SS frame..the lower  left rail  that is badly creased from a previous guy running up a rock. Luckily the engine mount  dimensions are not effected.

I know A7/A10 frames are mild steel tube and welded, not brazed. But what s the SWG or AWG thickness of the tube?

 It measures OD  30.6 mm  (1 7/32) so 30 mm modern tube will do well and be unnoticed since I will join the cut with bulled-ted inserts, grooved to take the MIG weld.

Woiuld appreciate any thoughts and thickness dimensions.

Many Thanks

Peter G

[bsa-bill]

good Question Peter, as time goes on will be needed more and an informative answer (as I'm sure is forthcoming) will help keep more of our beasts on the road

[muskrat]

As yet no one has cut through their spare frame  to check the wall thickness. I'd guess at 2mm.
Cheers

[KiwiGF]

I thought the frame was 1 1/8" o.d. X 1/8" wall?

If the o.d. Is measured near a bend it might appear to be a different size......

I'm not 100% certain of the wall thickness as I went to huge lengths with my battered frame to avoid cutting bits out, by removing dents and flattened bits using rounding "blocks", and filling any remaining imperfections with weld. The wall seemed that thick as it is so easy to weld, even with a diy arc/ stick welder.

Rocket Racer (aka Tim) on this forum will know the tube spec for sure as he built a replica rigid frame for his sidecar racer.

[Peter Gee]

Well I got 30.6~9 mm in several places which is 1" 7/32 nearest. 1 i/8th is for example  C12 C15 swinging arm guage..I know coz I have a piece and thought to use it until careful measurement showed it no be a little thinner OD.  30 mm x 4 mm should be good if one can find it. I doubt it was as thin as 2mm.