Seeking ideas to repair a B72 steel frame rail. Damage was caused by using a regular 2 rail seatpost.

A butt weld repair has failed, as I thought it would.

A replacement frame from Brooks was found to be about 30 mm too short for the 40 yo well broken in cover.

I’d like to braze a 5mm ID steel sleeve over the break. Any ideas?

Original B72 chrome frame with broken RHS rail in foreground, shorter B72 black powder frame behind with original cover.

I can't see the break in the pic. EDIT: Oh, there it is... Even thought it looks like that part is under axial compression, it will still experience bending stress there.

Regardless, the rail on that one is *spring steel*, possibly different from standard rail which might be simply high strength steel. But any steel that is hardened, welding can be a big problem, unless post heat treated, or the material has sufficient "hardenability" that it rehardens from just air-cooling. Brazing might not reach sufficient temperature to be problematic. You need to talk to someone expert is joining pieces of spring steel, I don't know if this is possible.

New Brooks saddles are available as preconditioned, to eliminate long break-in time. I think that's your best and lowest cost option.

I'd go with the sleeve.

Even if all the heat treatment is lost, you are going to have twice the material.

It's worth a shot. The problem with a sleeve is then that section is overly stiff with regard to the surrounding rail, and you will then get more stress at the sleeve ends. Cessna Conquests had this problem, a part in the tail failed, they beefed it up, more failures because it was then too stiff for the surrounding structure, they redesigned the whole area and the problem was solved.

I'd look at high pressure tubing for a thicker wall on a sleeve.

​​​​​​https://www.ebay.com/itm/221894266954

Stainless sleeve and JB would be my take even given diminishing returns, a lot of work but should be worth a shot without heat and may hold up.

One plan of attack, if you would indulge me for a moment, would be for you to PM me a shipping address so I can send you a 70's vintage B-72 with chrome rails for cost of shipping. The leather is pretty sketchy but the frame is good.

Do you know they sell an adaptor for these to fit single rail seat posts?
(Single or two bolt posts)

I have a 50 year old B72 with a badly stretched leather top. If we we share the key dimensions and verify it will fit, perhaps you could just transfer your saddle top over. You’d need to buy a set of the right rivets. Ridden by my wife, who has never been an Athena. She now likes a B17 Select, but that’s on a roadish/gravelish bike. The B72 was on her 1970 Raleigh Sport.

This way you’d get a new nose tightening gizmo set and a set of additional used OEM rivets.

Just out of curiosity, was the replacement frame shorter than than the old one?

From the OP:
"A replacement frame from Brooks was found to be about 30 mm too short for the 40 yo well broken in cover."
Looks to me like it's not even the right model frame. Maybe he can return it?

I'll add to my previous message: If you sleeve the break, instead of just straight perpindicular cuts on both ends, perhaps tapering the ends like good frame lugs, may smooth the stiffness transition at the sleeve ends.

Huh. I wasn't aware that Brooks made more than one frame for the B72.

Both very generous offers! This is a large part of why I like this forum.
Shipping may present a bit of a problem since the OP is in Australia.
Brent

Yup, saw that later on. You don't see that on the mobile app, which I use at all times, unless you specifically look it up. But my offer still stands. USPS Flat rate shipping is out. I still see DHL trucks driving around here regularly, wonder if they fly there?
ETA: I see on a website called shipbob.com where they claim the USPS will do a 2 kilogram first class for 15 bucks.

There’ were other similar saddles, I think one was called B67.they could have had different dimensions. Also Brooks may have altered the designs over time

I wouldn’t put much money or effort into the B72. I have 2 and one is ripping at the nose, and the other isn’t far behind. Both are low miles with one being in at least 90% condition. I’ve read many sad tales of the tears at the nose. Besides that problem, they are great seats. I have entertained the thought of checking on cost to recover these from our resident forum member who does this job. Thicker leather would probably be used in my estimation. I would think however that it would be cost prohibitive.

Wow! Just got back from the mountains and read the messages. Thanks for such considered responses and generous offers. (Shame on me for being blind sided by such unexpected kindness!).

I think replacing the frame with an older one will be perfect and provide a better long term solution than my home made sleeve repair. I am happy to pay shipping costs of course.

The broken frame I have is 235mm from the nose plate to the middle of the rear plate. "A 80" is stamped in the rear frame plate- probably for 1980 year of manufacture.




I'll send a private message to FBOATSB and take it from there.

Reply sent, Bill.

UPDATE.

Thank you to everyone for all the helpful ideas and suggestions. I received a replacement B72 frame today from forum member FBOATSP. I am profoundly
grateful for his generosity, which will enable a cyclist to get back on her bike, doing what she loves most.








The original cover has been installed and happy days are here again! Y'all love a story with a happy ending!

"I love it when a plan comes together."