Author Topic: B31 rigid - broken frame  (Read 540 times)

Online KiwiGF

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B31 rigid - broken frame
« on: 03.12. 2019 22:37 »
Anyone had experience of this break happening as per pic? I5 occurred without warning, luckily at low speed. The top tube under the tank is a bit banana shaped......

I’m thinking of complete strip down (partially there already) straightening it all out, then making a solid plug to put in the two ends, then TIG or braze it, also drilling a hole thro the tube near each end of the plug and welding a sort of spot weld to ensure plug cannot move inside the tube.

Thoughts?
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1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife)

Online Joolstacho

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Re: B31 rigid - broken frame
« Reply #1 on: 04.12. 2019 06:10 »
I'm wondering if sleeving, pinning, and brazing might be a better idea?
Maybe kinder to that ancient tubing.
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Offline Swarfcut

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Re: B31 rigid - broken frame
« Reply #2 on: 04.12. 2019 09:25 »
Another frame would be best, but a repair by replacing the bent and broken tubes is also possible.

 Here in the UK, Percival Brothers and Webb, under the Chris Williams Autocycle umbrella in downtown Dudley, used to be the go to guys.
 In manufacture, the frames were pinned together, by all accounts, then brazed. Getting the pins out to separate the lugs and tubes was what defeated many would be competitors. But PB&W were the experts, using a furnace to soften the braze, pull the pins, then extract the tubes. New tubes, old but undamaged lugs, good as new.

But along with Chris Williams' other engineering interests, Alpha Bearings etc, all now sadly history.

So, a local repair by brazing in a new reinforced member may be the only option here, but as this is an area carrying all the load, road shocks and torsional forces, it needs to be engineered and executed to the highest standard.

Swarfy.
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Offline Sluggo

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Re: B31 rigid - broken frame
« Reply #3 on: 04.12. 2019 10:28 »
yes, I have.  Not on that model BSA but on several other bikes. The reason is obvious.  Triumph experienced a number of these on several different frame types. (Rather thick weren't they? You would think they would learn from the first debacles but they repeated the same mistake on several years-variants)

That type of cast in neck without a proper brace was most common on the 1960 Duplex Preunit Triumphs.. with the different design and lacking the additional brace they fractured in the same spot or sometimes on the top section just past the casting.  Its stress point.  Same with Goose neck frames on the early unit 500s and they soldiered on with bodges until redesigning an all new frame nearly the same as the unit 650s in 1966.  The original 58 and up unit 500s were using a frame adapted from the Terrier.   I have each variation and can illustrate it if desired, including the factory braces  of each version.  But getting off point,. but same types of fractures most often highlighted in racing as the 500s in the US were more common until changes in AMA racing rules.

I HAVE repaired many such frames as well as badly executed Choppers (Bad form to rake a cast headstock)

While stock appearances are important, if you do modify-repair, Consider several options to brace the headstock.  (Large triangle plates Ala 1971-> up OIF models) or horizontal cross brass.   Many people added their own cross brace to the "Widowmaker" Triumph Duplex frames but Triumph redesigned the frames and offered 1:1 swaps thru dealers for replacement frames on warranty.  This was due to several deaths of racers including I believe 2 in the Big Bear race.   ** I have one of these replacement frames for my 1960 T120 Bonneville.

Norton repeated this design fault on the 1968 initial runs of the Commandos and again earned the nickname "Widowmaker frames"  and I modified one of the earliest known commandos in the US. 

As detailed, the proper repair is a new front tube installed in the casting with the factory brazing and pins, but still , I would add a secondary brace tube and once the tank is mounted would be out of view mostly.
Done properly it should be done in a frame fixture and the whole thing done squarely and in alignment in each plane.  Some fabricators prefer the lay down fixtures but a stand up fixture is adequate if its properly secured and stabilized.   I have several friends who have fab and frame building experience.

Im attatching a pix of a duplex widowmaker and the replacement frames.

BTW,, nice thumper.  I have 2 rigids and one plunger of those early singles. Putting the plunger up for sale soon.

To illustrate
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Offline RDfella

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Re: B31 rigid - broken frame
« Reply #4 on: 04.12. 2019 11:44 »
My A10 had a cracked downtube, about halfway down.
I repaired it the same way that I lengthened the downtube of my M21 when fitting the vee twin engine.
First, if it’s a crack, then cut it right through. Then use a flap wheel to clean inside both ends of the tube. Then turn up a tube that just slides in the frame, walls a touch thicker than those of the frame (solid gains nothing except weight and makes it harder to braze). Make the tube about 3” long and mark halfway with a felt tip pen. Now drill a half inch hole right through the frame about an inch from the crack / join. Clean up with flap wheel. Push frame ends apart and slide in repair tube. Line up frame tubes and use felt mark to guide as you slide inner tube to bridge the join. Now braze through the holes and the join itself. Braze is best, due to its capillary action. Got pics of it somewhere, but can’t find at present.
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'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline Rex

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Re: B31 rigid - broken frame
« Reply #5 on: 04.12. 2019 12:07 »
Yep, quick easy and effective.
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Offline RDfella

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Re: B31 rigid - broken frame
« Reply #6 on: 04.12. 2019 12:13 »
herewith pics of my A10 frame repair
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'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline RDfella

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Re: B31 rigid - broken frame
« Reply #7 on: 04.12. 2019 12:14 »
see the ist pic didn't make it onto the page ...
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'49 B31, '49 M21, '53 DOT, '58 Flash, '00 Firestorm, Weslake sprint bike.

Offline mikeb

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Re: B31 rigid - broken frame
« Reply #8 on: 04.12. 2019 20:24 »
Kiwi - a guy with a plunger goldie broke his frame like that on an Auckland club run last year. got it welded up not sure exactly how by a guy i think in hamilton. pm me if you want and i'll try and find out who did the work and exactly what was done - it was someone with skills. i saw the bike on the road recently so its back together.

BTW is it time you gave up motocross on that thing yet?
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Offline Kickaha

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Re: B31 rigid - broken frame
« Reply #9 on: 05.12. 2019 05:49 »
Kiwi - a guy with a plunger goldie broke his frame like that on an Auckland club run last year. got it welded up not sure exactly how by a guy i think in hamilton. pm me if you want and i'll try and find out who did the work and exactly what was done - it was someone with skills. i saw the bike on the road recently so its back together.

BTW is it time you gave up motocross on that thing yet?

Most likely Steve Bridges at F1 Engineering
https://f1e.nz/
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Online KiwiGF

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Re: B31 rigid - broken frame
« Reply #10 on: 05.12. 2019 08:57 »
Kiwi - a guy with a plunger goldie broke his frame like that on an Auckland club run last year. got it welded up not sure exactly how by a guy i think in hamilton. pm me if you want and i'll try and find out who did the work and exactly what was done - it was someone with skills. i saw the bike on the road recently so its back together.

BTW is it time you gave up motocross on that thing yet?

Does riding the gravel roads around the Wairarapa count as motocross?  *smile*
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New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife)

Online KiwiGF

  • Last had an A10 in 1976, in 2011 it was time for my 2nd one. It was the project from HELL (but I learned a lot....)
  • Wise & Enlightened
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Re: B31 rigid - broken frame
« Reply #11 on: 05.12. 2019 08:58 »
I'm wondering if sleeving, pinning, and brazing might be a better idea?
Maybe kinder to that ancient tubing.

Thanks  *beer* ...I think you’re right.
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New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife)

Online KiwiGF

  • Last had an A10 in 1976, in 2011 it was time for my 2nd one. It was the project from HELL (but I learned a lot....)
  • Wise & Enlightened
  • *
  • Join Date: Feb 2011
  • Posts: 1506
  • Karma: 13
Re: B31 rigid - broken frame
« Reply #12 on: 05.12. 2019 09:01 »
Another frame would be best, but a repair by replacing the bent and broken tubes is also possible.

 Here in the UK, Percival Brothers and Webb, under the Chris Williams Autocycle umbrella in downtown Dudley, used to be the go to guys.
 In manufacture, the frames were pinned together, by all accounts, then brazed. Getting the pins out to separate the lugs and tubes was what defeated many would be competitors. But PB&W were the experts, using a furnace to soften the braze, pull the pins, then extract the tubes. New tubes, old but undamaged lugs, good as new.

But along with Chris Williams other engineering interests, Alpha Bearings etc, all now sadly history.

So, a local repair by brazing in a new reinforced member may be the only option here, but as this is an area carrying all the load, road shocks and torsional forces, it needs to be engineered and executed to the highest standard.



Thanks, that makes sense, I think I can see a pin, I’ll post pics.

By a massive fluke I found a frame section on the local equivalent of eBay and hopefully it’s on its way to me now, main difficulty in using it is the frame number is in 5his part, and in my case that’s where the VIN plate was attached a couple of years ago when it was re registered  *sad2*
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New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife)

Offline mikeb

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Re: B31 rigid - broken frame
« Reply #13 on: 05.12. 2019 09:03 »
Quote
Does riding the gravel roads around the Wairarapa count as motocross?
it depends how you ride Kiwi  ;)
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'61 Super Rocket  - '47 B33 -  '18 Triumph Street Triple RS

Online KiwiGF

  • Last had an A10 in 1976, in 2011 it was time for my 2nd one. It was the project from HELL (but I learned a lot....)
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Re: B31 rigid - broken frame
« Reply #14 on: 05.12. 2019 09:03 »
yes, I have.  Not on that model BSA but on several other bikes. The reason is obvious.  Triumph experienced a number of these on several different frame types. (Rather thick weren't they? You would think they would learn from the first debacles but they repeated the same mistake on several years-variants)

That type of cast in neck without a proper brace was most common on the 1960 Duplex Preunit Triumphs.. with the different design and lacking the additional brace they fractured in the same spot or sometimes on the top section just past the casting.  Its stress point.  Same with Goose neck frames on the early unit 500s and they soldiered on with bodges until redesigning an all new frame nearly the same as the unit 650s in 1966.  The original 58 and up unit 500s were using a frame adapted from the Terrier.   I have each variation and can illustrate it if desired, including the factory braces  of each version.  But getting off point,. but same types of fractures most often highlighted in racing as the 500s in the US were more common until changes in AMA racing rules.

I HAVE repaired many such frames as well as badly executed Choppers (Bad form to rake a cast headstock)

While stock appearances are important, if you do modify-repair, Consider several options to brace the headstock.  (Large triangle plates Ala 1971-> up OIF models) or horizontal cross brass.   Many people added their own cross brace to the "Widowmaker" Triumph Duplex frames but Triumph redesigned the frames and offered 1:1 swaps thru dealers for replacement frames on warranty.  This was due to several deaths of racers including I believe 2 in the Big Bear race.   ** I have one of these replacement frames for my 1960 T120 Bonneville.

Norton repeated this design fault on the 1968 initial runs of the Commandos and again earned the nickname "Widowmaker frames"  and I modified one of the earliest known commandos in the US. 

As detailed, the proper repair is a new front tube installed in the casting with the factory brazing and pins, but still , I would add a secondary brace tube and once the tank is mounted would be out of view mostly.
Done properly it should be done in a frame fixture and the whole thing done squarely and in alignment in each plane.  Some fabricators prefer the lay down fixtures but a stand up fixture is adequate if its properly secured and stabilized.   I have several friends who have fab and frame building experience.

Im attatching a pix of a duplex widowmaker and the replacement frames.

BTW,, nice thumper.  I have 2 rigids and one plunger of those early singles. Putting the plunger up for sale soon.

To illustrate

Thanks, I’m not not feeling so unlucky now! I may not reinforce it as I don’t think this type of failure is common, and I intend to fix it very well!
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New Zealand

1956 A10 Golden Flash (1st finished project)

1949 B31 rigid “400cc hot rod” (2nd finished project, + favourite bike)

GL1800 Goldwing, well, the wife likes it

KTM 950 ADV, cos it’s 100% nuts

1952 Armstrong Siddeley Whitley for rainy days (with wife)