carpmart
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| posted on 31/12/09 at 06:00 PM |
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Is there any magic way to check a chassis for cracks and stress fatigue....
...... other than getting it X-rayed?
I'm trying my best to check over my race chassis for cracks etc. Its painted black metallic which doesn't lend itself well to inspection!
(wish it was grey!)
I'm using as much natural light and florescent etc but I'm still not convinced.
Does the collective have an easy (foolproof) way of inspecting a used chassis?
Thanks in advance!
You only live once - make the most of it!
Radical Clubsport, Kwaker motor
'94 MX5 MK1, 1.8
F10 M5 - 600bhp Daily Hack 
Range Rover Sport - Wife's Car
Mercedes A class - Son's Car
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clairetoo
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| posted on 31/12/09 at 06:08 PM |
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The foolproof way of testing for cracks is to pressurize the chassis - my drag bike frames were used as the air tank for the air shift , so any cracks
meant no racing till it was fixed (not that I ever had such a failure , but you get the idea)
The downside to this is it has to be planned for at the build - all connecting tubes have to be drilled at the joint , and every joint has to be
perfect......... 
Its cuz I is blond , innit
Claire xx
Will weld for food......
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907
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| posted on 31/12/09 at 06:46 PM |
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Dye Penetrant would show up cracks.
It's a simple aerosol system.
Paul G
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britishtrident
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| posted on 31/12/09 at 06:51 PM |
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Dye pentrant and visual inspection is the only viable way --- you have to wire brush the paint off at the joints.
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907
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| posted on 31/12/09 at 06:58 PM |
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Magnetic particle works as well.
Paul G
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tommyab
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| posted on 31/12/09 at 07:18 PM |
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As Paul said, MPI is probably easiest, but needs paint to be removed first. Would probably be easiest way on the welds.
Tom
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carpmart
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| posted on 31/12/09 at 07:24 PM |
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Thanks for all the replies!
I'm not in a position to fully strip the chassis and then remove paint from welds so I guess its a good visual check this year, then full strip
down next year.
Claire - love the frame pressurisation method!
You only live once - make the most of it!
Radical Clubsport, Kwaker motor
'94 MX5 MK1, 1.8
F10 M5 - 600bhp Daily Hack
Range Rover Sport - Wife's Car
Mercedes A class - Son's Car
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alistairolsen
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| posted on 31/12/09 at 07:33 PM |
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pressurised frame is the same reason I dont mind banded steel wheels, 100% Non destructive testing cycle!
My Build Thread
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britishtrident
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| posted on 31/12/09 at 08:11 PM |
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quote:
Originally posted by carpmart
Thanks for all the replies!
I'm not in a position to fully strip the chassis and then remove paint from welds so I guess its a good visual check this year, then full strip
down next year.
Claire - love the frame pressurisation method!
Porsche used in real racing time, the Le Mans cars ran with the chassis pressurised with argon and had a pressure gauge mounted on the roll hoops if
the pressure went down you knew the chassis was broken.
The disadavantage is it will only show up a through thickness crack ie one that has already broken through both surfaces ie it is already a
fracture.
[Edited on 31/12/09 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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907
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| posted on 31/12/09 at 08:24 PM |
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When I used to make coded stuff the lifting lugs were always MPI'd. (You can't Xray a fillet)
The inspector would spray the weld area with quick drying white paint and allow to dry, then spray with the particle liquid.
The iron power magnetic field lines were easier to see on the white paint.
What you need is a white chassis.
Happy New Year
Paul G
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liam.mccaffrey
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| posted on 31/12/09 at 09:03 PM |
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MPI is the easiest.
Build Blog
Build Photo Album
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major
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| posted on 1/1/10 at 07:12 AM |
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On bikes "chalk dust" was used.
Happy New Year
marcel.
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JB
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| posted on 26/1/10 at 01:22 PM |
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First learn to indentify where cracks are likely to occur. Carroll Smiths book Engineer To Win will help.
Then you will know where to look.
I would start where the big loads go in (engine, suspension and dampers) where ever there are welds and a change in section.
Sharp edges are also a common place for cracks to start as are holes. So no drilling lightening holes!
[Edited on 26/1/10 by JB]
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