Solution required for seat bracket placement challenge

[Mark B]

So, does the seat bracket not fit down onto the tubing? The tubing doesn't look to be that fat that the bracket shouldn't suck right down on top. The bracket is plenty strong, if that's your concern.

Regarding the cables, you will only need one of those; the brake. The rear derailleur cable will now route down the fork. You can run the brake cable housing right through the seat bracket. Is the cable housing or cable stops what is keeping the bracket from going down any further?

Mark

 

[Mark B]

I think if it were a high-end aluminum frame, where the tubes are paper thin, you might have an issue. If your frame is anything like mine, that aluminum tube is probably thicker than the bracket you're clamping to it. I wouldn't worry about it. As long as your seat is solid and doesn't rock side to side, you should be good.

Mark

 

[MrSteve]

I'd carve a wooden adapter/spacer out of boxwood.
Or maple: I'm used to maple.
Anyway, that way the steel seat bracket would be seated perfectly in the wood
and, the frame tube would be solidly socketed in the wood.

But that's just me.

An easier solution would be to 'bed' the steel seat bracket onto the bike's frame,
exactly like a rifle barrel is bedded into it's stock.
Use fibreglass to do this; use plastic film as a mold release.

I don't like the idea of the steel bracket riding on the curved aluminum
top tube on only two points either!

Hope this, at least, gives you a few ideas.

-Steve

 

[John Tolhurst]

Mark B wrote: I think if it were a high-end aluminum frame, where the tubes are paper thin, you might have an issue. If your frame is anything like mine, that aluminum tube is probably thicker than the bracket you're clamping to it. I wouldn't worry about it. As long as your seat is solid and doesn't rock side to side, you should be good.

Mark

The bracket is soft alloy, the frame will be heat treated 6061 or 7005. One one of my conversions I cut along the saddle of the bracket from each end, one or two times each end, then talked it into place with 'gentle persuader' - my nice heavy metal working hammer. Put a block of wood on it, hit that, put some rubber underneath, get an old tube, cut it up.