9 replies to this topic

[DFord]

This is a desperate call for help to anyone that knows,
I've completed the de-seaming process on my project roadster for uni, in my write up i need to justify deseaming the body and comment on the technical aspects of the process, not just the process itself.
My common sense tells me that the deseamed shell will be stronger/ more rigid? than a shell that has the original seams.
because the load will be spread across the whole of the panels, not just concentrated around the spot welds on the orig seams..but i need to prove this.
does anyone know where i can find the info that i need (if you can decipher my ramblings)

Thanks very much
Fordy

[Dan]

That depends entirely on how well you've done it. The Works bodshells were seam welded, this improved rigidity but don't know about strength. The Mini has as many spot welds as Jack Daniels and his slide rule thought were adequate, not as many as the computer deems essential like modern cars have (compare the crash performance of the Mini and Metro for evidence, the flat panels of the Metro don't help but the paring down of welding and reduction in the number of overlaps and seams to the bare minimum coupled with that makes it dangerous). So it's quite a strong shell really. Even when it does pop at the seams, there is an argument that tearing that many welds absorbs a lot of crash energy.

As for technical reasons for doing it, it reduces the front cross section by a huge amount and improves the drag performance of the body dramatically. There are numbers published somewhere, can't remember where just now though.

[Ethel]

Vizard tallies up the sq inches in "How to modify yer Mini" & I think it may also be in the race 'n rally source book. I suspect deseaming makes the shell weaker and less rigid, but that would have to be balanced against more weld holding the bits together and there are likely circumstances where the external seams would fair worse as well as those where they'd be an asset.


you could look at...

Rigidity of a flat butted join versus a flanged, spot welded one - wouldn't be hard to knock up a few test pieces to pull 'n twist to the point of failure. The 3D section of a flanged joint suggests it's a foregone conclusion, but a flange can also be a lever.

A tensile strength comparison - pi x diameter means you can get a greater length of weld interface using spots along a panel joint than with a continuous seam.

Exposure of the seams to impact and folding in a collision.

[sonikk4]

I think purely from a personal point of view to make a really nice strong joint here i would place a strip of metal behind the seams to be welded to ensure a good base for seam welding. This will also help to prevent cracking.

With regards to the pro' and con's for de seaming if done properly and lead filled to finish then it will look really good and should last. With flange's like previously mentioned there was no real consistency to how many spot welds were applied to them when joining and as to crash testing,well it does not take much to turn a standard mini into a much smaller parcel. Plus they seem to attract rust especially the later models.

Each to their own here really, if done well by a competent welder using some common sense then there is no real reason to think why a de seamed car would be weaker than a non de seamed vehicle.

The only way to test properly would be to use Euro NCAP testing of a standard built mini and a de seamed one to see what would happen. Will this happen, no but it would be interesting to see the results.

[lapider]

there was an article in mini world some years ago that went through the different stages of aerodynamic tuning for the round nose . they found out that all the exposed body seams amounted to an a4 sheet of paper in drag terms.

[Bungle]

is that end on or flat ?

[Jayme 1275]

not really a structural advantage but the deseaming make the cars more aero dynamic as it reduced their frontal are for resistance

hope that some use to you

[DFord]

Thanks for your help guys, notes have been taken and both sides of the sides have been discussed well, this is good!
thank you so so much!

[somecrapname]

There is an article on the Carbon Weezel website where they took a hillclimb mini to wind tunnel, one of the results was for de-seaming:

Tape was applied to the gutters and seams at the front in the hope that drag might be reduced. And there was a very small reduction of 0.004 on the drag coefficient but also a small increase in positive lift. A similar, possibly greater effect might be expected from de-seaming a shell.

Source: http://www.carbonwee...sting_mini.html

[DFord]

There is an article on the Carbon Weezel website where they took a hillclimb mini to wind tunnel, one of the results was for de-seaming:

Tape was applied to the gutters and seams at the front in the hope that drag might be reduced. And there was a very small reduction of 0.004 on the drag coefficient but also a small increase in positive lift. A similar, possibly greater effect might be expected from de-seaming a shell.

Source: http://www.carbonwee...sting_mini.html

Nice find!