General Category > The Knowledge
Dealing with rust / refinish
LittleWheelsandBig:
I don’t think Mr Oliver did FEA of his frames. The bridge adds a bit of stiffness but adding the same amount of steel to the stays is at least as efficient. The other reasons are worthwhile on their own though.
mrcharly-YHT:
--- Quote from: bobb on 26 April, 2021, 12:34:10 pm ---Hmmmm... You think it needs to go to a frame specialist for repair?
--- End quote ---
I think that you won't know until you try poking holes in it with a little screwdriver.
If it is sound, you won't succeed and will have just dug out rust.
If you do, I think it needs a framebuilder.
nuttycyclist:
Back in 2005 I stripped my old MTB and repainted it in hammerite. According to the post it was ~20 years old at that point.
http://www.nuttycyclist.co.uk/cycling/oldmtb-restore.htm
I still use that now as a shopping bike, and it looks not much worse than it did in those photos and much better than it looked before I started work.
mzjo:
--- Quote from: rogerzilla on 26 April, 2021, 06:03:47 pm ---
--- Quote from: LittleWheelsandBig on 26 April, 2021, 12:38:04 pm ---Chainstay bridges don’t do very much to strengthen a frame.
--- End quote ---
They do if the chainstays are long, making a stiff box at the back with the hub on the opposite side (according to Tony Oliver"s book, anyway). Not so much on racing bikes, which don't necessarily have one at all, if they have vertical dropouts or track ends.
The bridge actually serves three purposes:
1. Stiffness where the stays are long, as on a tourer
2. Somewhere to bolt a mudguard
3. Stops the tyre jamming when you remove a wheel with forward-facing dropouts
--- End quote ---
From personal experience I would disagree with n°3. My Gitane with forward-facing dropouts and no chainstay bridge is an absolute dolly to get the rear wheel in and out, especially compared to my other frames with bridges. The worst is the vintage Peugeot Corse which is an absolute pig. It is a racing frame so the mudguards issue doesn't come into play.
--- Quote from: LittleWheelsandBig on 26 April, 2021, 06:09:53 pm ---I don’t think Mr Oliver did FEA of his frames. The bridge adds a bit of stiffness but adding the same amount of steel to the stays is at least as efficient. The other reasons are worthwhile on their own though.
--- End quote ---
I think, depending on the frame builder, it serves only as a mudguard anchorage point; the Gitane seems plenty stiff enough and it's only a lower end industrial production racing frame. Eliminating the bridge does eliminate a potential mudtrap however, which is probably a valid arguement on a tourer - other ways can be found to anchor that end of the mudguard.
bobb:
--- Quote from: mrcharly-YHT on 26 April, 2021, 11:59:57 am ---....what would bother me more is the thin line on the BB/chainstay join in the third picture.
--- End quote ---
I'm not sure where you mean. Maybe A or B? Or something my eyes are too shit to see?!
[Big pic]
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