Has anybody attempted to make their own e-type frames out of weldadable round and square tubing ???
No idea, but it would be a lot of work to set up the jigs, do precision cuts on the tubing and weld everything together. The jigs, ensuring everything is properly aligned for welding, would be the biggest headache, IMHO.
What John says: itâs doable, but given there is almost endless degrees of freedom, plus the fact that the suspension, bonnet, and engine all have to be in fairly precise alignment in 3 dimensional space, itâs alllllll about the jig.
Cutting and welding the tubes is the easy part.
You could use an old pair as a jig to build⌠the jig!
You will probably find that the rectangular tubes are hard to come by, at least in small quantities. My research, years ago, indicated that Jaguar âfurnace brazedâ the frames, which if I understand it, the frames were assembled in a jig, the joints loaded with brazing material, and the entire frame heated in a furnace to a temperature that allowed the brazing material to flow. Followed by controlled uniform cooling, one would expect the frames to come back to the correct shape when cold. When you try and weld one joint at time, this is much harder to achieve. Iâve done some roll cage fabrication and it is tough to do without warpage.
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Sooo I went to the local metal merchant he had all the tubes in light gage steel including the rectangular shapes all of it free welding with little distortion using Tig welding.
The joints would have to be shaped and cut for perfect fits and the sleeves that jaguar used would not be necessary. I have fabricated go kart racing frames as well as roll cages all these have to have tremendous strength. the only drawback would be they would not look exactly like the originals, they would weigh a few pounds more, and they would be over rated for crush ability. The steel plates and fittings would be laser cut for an exact fit and all the holes would be laser cut as well. When the jigs are built the time for fabrication would be approx 20 hours, raw material is about $88. and laser cutting of all the pieces another $75. this could be about $1,000. This is for all 3 frames, left, right,
and the picture frame ! Add a profit to that and I wonder how many people would buy them.???
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True: when installed roll cages, a good griend who built 4130 cro-mo sprint car chassis taught me a trick: do a small section on one corner, then move to an opposite corner, then just keep switching positions, âstitch-welding,â until all joints were finished.
Untill you could guaranter a very close fit, on a few different chassis, just one.
Also, do you think youâd be prepared for the liability, if a frame failed, during driving, or an accident?
I think I could do the work, but to do a proper FEA on a set, plus indemnification through a corporation?
No, thanks.
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But are these light gauge steel tubes the same strength as the original materials? How many sizes would you have to go up to get the same strength?
Is that 20 hours just welding? If it were me, itâd be about 20 h just cutting the tubes - that after Iâd spent 200 hours designing a jig to hold the tubes at the correct angle while cutting them.
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Hello Harvey,
Never, ever where the frames furnace brazed. You only have to look at the braze fillets of the frames to determine that. However, when the cars were not that long out of production, I had a visit to the factory, saw the jigs and spoke to one of the workers who actually brazed the frames. They were all hand brazed.
Steve wrote:
You could use an old pair as a jig to build⌠the jig!
If you were to construct a jig from an existing assembly the resulting product from that jig will not be the same dimensions (tolerance taken into account) as the original. The reason is shrinkage of the heat affected zone. The Jig has to be reasonably solid and unyielding so that the component parts are in the correct relationship when loaded into the Jig. As there is nowhere for the expanding metal to go during the brazing op, the plastic state of the material allows for compaction. When cool, the length of the member is slightly shorter.
This can be easily observed by clamping a short piece of steel bar in a vice (axis perpendicular to the vice jaw) with the force applied by the vice just sufficient to hold it. Heat a narrow band in the centre of the bar to a bright cherry red. Now go make yourself a cup of tea, or coffee and by the time you have finished and returned to the vice, the piece of bar will be either in the bottom of the vice, or on the floor. This the same principle at work when Hot Shrinking a full are of a body panel.
Without the benefit of drawings, you could:
- made a jig using a pristine set of frames as the model
- assemble and braze the components of a new frame using the current jig
- measure the finished frame and compare with the original to determine the degree of shrinkage.
- modify the jig with the benefit of the known shrinkage
- try again and repeat 3 and 4 if/where required.
Regards,
Bill
Oven brazing is an old âironworkingâ process from the blacksmith era before electric or lmaybe even gas welding became common. It is used for lug and tube construction where an item such as a frame can be assembled on the bench by placing each tube into its lug hole with the slivers of braze applied. The assembly effectively holds itself together so that when all the overlapping joints between thick lugs and thin tubes reach the right temp together, the braze is drawn by capillary action into the joints and disappears except for a just-visible rin at the tube entry point. The lugs effectively support the structure and âguaranteeâ the geometry as well as normally providing the attachment points for powertrain, steering/suspenion etc
Lugless construction is lighter because there are no thick lugs or overlapping parts. But that means the pile of tubes would just fall in a heap unless held in a sturdy jig. Even if you were happy to toss a large jig in the oven and found a way to hold the braze to each joint, the braze would dribble down the frame in the absence on deep capillary draw spaces and would not puddle to form the smooth fillets of extra metal that give tube-and-jig lugless frames their strength.
Do you think whoever makes the new ones now has the liability on their product?
Phil
Well, I stand corrected about the furnace brazing bit. Iâm pretty sure I read that somewhere but thatâs the internet for you. Thanks Pete and Bill.
Well, if they do not, a simple âcontract of adhesionâ isnt going to do much for them, in the case of catastrophic failure.
Iâm guessing that, in our tort-crazy world, they have some indemnification process, and/or solid engineering specs on which they can depend, if the structral quality and Suitability of the product was called into question.
Hereâs hoping you continue to have little or no professional dealings with lug and tube construction Harvey, given that your engineering work involves nuclear power plants!
Yes, thatâs right Pete, when Iâm at work I hold myself to the highest of standards, not wanting to be âthat guyâ responsible for a problem in such a critical industry. No lugs in sight.
Regarding the OP, for myself, with Etypes becoming so valuable in the market, I try to use either the original part or an exact replica. My Etype Fabs frames that I bought a few years ago before the price went up are a beautiful example of a replica frame.
I believe that the tube was some high tensile stuff specially specâd up for the job, not the common or garden mild steel stuff you might find in a DIY store.
Its a Chrome Molybdenum tubing. The difficulty with regards to the material is getting it in the correct cross section (if youâre going to mimic the original exactly).
The after market frames of today use a different grade than the original and is more forgiving with regards to effects of heat in the brazed areas and the subsequent requirement of heat treating. Robey frames are made from T45 (Bs4T45-Bs4T100) steel tubing.
Regards,
Bill
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Having seen some of the stuff youâve build, Derek (the Terminator was out of this world) I think you could pull it off, though I also think your time estimate is a tad low - when I tell my kids how long it will take me to do something they ask âis that in real time or in Dad-time?â Regardless, I donât think youâd have too many customers. Most enthusiasts who set out to restore their Es are anal about whatâs right and subframes that detract from the original design would be a hard sell. And there is, as already mentioned, the question of liability. I personally knew a welder who fabbed custom trailer hitches as a sideline and who, after having made and sold several, was paid a visit by the Ontario Provincial Police after one failed on the highway. In addition to being liable for the damages he had to pay to have every single one of the others inspected and certified and not all of them passed. Pretty much bankrupted him. Short story, I wouldnât go there if I were you.
Got that '70 on the road yet?
Iâve always wondered, who supplied the frames? W ere they built in house or outsourced? Do you recall the name?