Etype bonnet alignment MAJOR problem

That’s the square tubed frames: the picture frame and the triangle frames are mild steel.

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Is that true? we cut up a perfectly good 531 race bike for nothing, when any old tube would do! I hope your wrong!!

Nope, Paul’s right. Only the engine (side) frames are Reynolds 531 alloy, the picture frame and “trapeze” are made from mild steel. The Renolds tubing will not handle welding as it makes the steel brittle and will eventually crack, and even re-brazing it won’t work for long.

Cool nick, I have a spare bonnet frame that was waiting for a donor bike to come along, ebay mild steel tube £3.60 a length. will be fixed by the weekend!

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I sure see a lot of bicycle frames and front ends cut extended and welded. Do you mean heat treated to make the tubing harder? Seems to cut like mild tubing to me.

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While it may cut like mild steel it isn’t mild steel, it’s a manganese-molybedenum material that reacts poorly to the heat of welding. In the E-Types it was brazed, bicycles were usually silver soldered. It won’t fail immediately, but it will fail if welded. Or so I’ve heard.

I’ve read the critical temperature for the material is around 1,750F. Heat the material beyond that and you’ve weakened the metal. Welding, of course, involves localized temperatures much higher than that. Further I was told the brazing they used was accomplished somewhere around the 1,300F.

AFAIR, all that is correct. Reynolds 531 CANNOT be welded, by any conventional method.

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If I learned one thing in life many have an opinion based on hearsay. But no experience. ie. you mention heat treating after low temperature brazing??? Wouldn’t all the brackets fall off into the furnace?

We taklin’ bikes, or Jags?

:stuck_out_tongue_winking_eye:

Within that link, this bit caught my nerdist eye!!

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IMHO, as often as this topic gets beaten around, there must be some credibility as to the nature of the alloy that was used in the front framework. Having just taken mine down to bare metal, at least with my Series 3, I can affirm that it appears to have been brazed with bronze or similar rather than traditional welds.

My take is that I don’t want to risk any chances weakening the front structure from the picture frame backwards. Now forward of the picture frame, I don’t think that there would be much of an issue modifying the bonnet hinge framework as it doesn’t participate in controlling the torque from the engine or suspension forces.

Just my take as a non expert.

You are correct, and, done properly, mods and repairs can be performed on the picture frame, too.

The side frames were oven-brazed, and CANNOT be joined or repaired otherwise.

I had saved some old frames, and I was able to make a decent join, using eutectic bronze flux rod: that said, I would never put it to the test.

Whats the difference?

Between…which? Im gettin’ lost!!

Yours is probably the most honest answer so far. To many experts. But many are extremely intelligent. The structure Jag designed from the cowl forward is extremely high tech and designed for extreme racing under all conditions. Very simple, but still overbuilt…Study the design.
They also made it foolproof for the worst scenario unexperienced bodymen and hacks worldwide that have a torch in they’re hand. I have never read any horror story’s of bad welding, modifications to the structure or crash and burn from those who used the WRONG welding techniques of those who put an engine in one of these cars that wasn’t designed for…Chevy’s and Fords along with the transmissions.
In other words. Jaguar took into consideration all factors and was very successful making them idiot proof. Worst case scenario of my modifications on the front bonnet mount may let it fail and scrape on the ground.

Between a Jag and a bicycle?

Big difference: differing structures, radically different stresses.

Bottom line, both Jag and the bike frame makers know precisely how to successfully join 531 tubing to itself, or to frame lugs.

Yeah, maybe your right. Bicycles see extremely higher stresses then the the
Jag ever will (spindly frames jumping curbs with no suspension whatsoever).
plus where did I mention joining any 531 on my car anyway? I believe I
brought up an alignment issue before my welding experience came under
attack.
Like I said earlier, I see kids welding bicycle front ends to extend them
and they hold up better then welding something unforgiving like bedframe.