David Jenkins
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| posted on 14/6/12 at 02:53 PM |
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Bend back, or replace?
As reported elsewhere, I had a mishap yesterday.
The only significant chassis damage is the upright FU2, which supports the upper suspension arm at the back. This is what it looks like at the
moment:
I now have a choice - do I try to bend it back (it's not bent much) or do I replace it?
Replacement is going to be a total PITA, and will probably involve cutting away some of the ali side panel so that I can weld properly. It will also
be very difficult to get the MIG torch in there.
My brain tells me that it should be replaced, but I don't know if I'm being over-cautious. After all, they pull tin-top chassis back into
shape using chains and winches!
All views and opinions appreciated...
BTW: This is what happened to the top ball joint!
 
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MakeEverything
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| posted on 14/6/12 at 03:01 PM |
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The difference between this and a tintop chassis, is that its tubular and normal cars are pressed panels and monocoque. If i was going to leave it in
and bend it back i think i would strip its coating, take the panel off anyway to see every angle of the metal and any potential stress areas. Then, i
suppose if youre doing that, you may as well replace it.
In short; i would replace it. It will be weaker next time (if) it happens.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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Mr Whippy
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| posted on 14/6/12 at 03:29 PM |
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yeah I'd replace that too, even with heat you'd never get it perfectly straight and would always look wrong. There are some on line steel
supply shops that will sell tube by the meter
Do get a steel rule and lay it against the other tubes once you have removed it to check that they are all straight
[Edited on 14/6/12 by Mr Whippy]
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scutter
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| posted on 14/6/12 at 03:30 PM |
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Replacement gives peace of mind that all right before you head down a twisty lane.
ATB Dan
The less I worked, the more i liked it.
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David Jenkins
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| posted on 14/6/12 at 03:31 PM |
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quote:
Originally posted by Mr Whippy
There are some on line steel supply shops that will sell tube by the meter
I think I've still got some odd bits... if you pardon the expression!
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wilkingj
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| posted on 14/6/12 at 03:43 PM |
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Its already been stressed.
Bending it back will stress it more.
I would cut it out and replace it.
You know it makes sense.
1. The point of a journey is not to arrive.
2. Never take life seriously. Nobody gets out alive anyway.
Best Regards
Geoff
http://www.v8viento.co.uk
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David Jenkins
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| posted on 14/6/12 at 04:00 PM |
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quote:
Originally posted by wilkingj
Its already been stressed.
Bending it back will stress it more.
I would cut it out and replace it.
You know it makes sense.
You're right - but I just know it's going to be a PITA to weld.
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perksy
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| posted on 14/6/12 at 04:33 PM |
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Know its a pain, but like everybody else above i'd replace it
Once its done you won't have any lingering doubt in the back of your mind
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David Jenkins
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| posted on 14/6/12 at 04:45 PM |
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OK - it looks like it's going to be a replacement...
Now - are those air-powered reciprocating saws any good? It's not going to be easy to get in there with anything else, and I'm always
looking for an excuse for new toys! 
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MakeEverything
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| posted on 14/6/12 at 04:48 PM |
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I would use an air cut off disk, for precision. IVe got both, and the recip. saw is a little coarse.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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David Jenkins
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| posted on 14/6/12 at 05:23 PM |
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quote:
Originally posted by MakeEverything
I would use an air cut off disk, for precision. IVe got both, and the recip. saw is a little coarse.
Already got one of them - I find that it stalls really easily and doesn't cut too well. The reason for mentioning the saw is because of access
space - it's a bit crowded around the base of the chassis member.
Anyway - I wasn't expecting precision - I was going to cut off close to the end and grind the remainder flat.
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MakeEverything
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| posted on 14/6/12 at 05:31 PM |
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quote:
Originally posted by David Jenkins
quote:
Originally posted by MakeEverything
I would use an air cut off disk, for precision. IVe got both, and the recip. saw is a little coarse.
Already got one of them - I find that it stalls really easily and doesn't cut too well. The reason for mentioning the saw is because of access
space - it's a bit crowded around the base of the chassis member.
Anyway - I wasn't expecting precision - I was going to cut off close to the end and grind the remainder flat.
Yes, you have to be a bit gentle with them and let the disc do the work rather than the force.
Kindest Regards,
Richard.
...You can make it foolProof, but youll never make it Idiot Proof!...
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liam.mccaffrey
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| posted on 14/6/12 at 05:33 PM |
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I cut up 2 mx5's in an afternoon with 110v dewalt recip, they are unbelievable, that tube will not last 5 seconds!!!
Build Blog
Build Photo Album
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ditchlewis
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| posted on 14/6/12 at 06:08 PM |
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your car is so good you would not feel happy in the long run if you did not do the job properly.
i,ve got one of those air saws that look like a gun. if its any use you can borrow it.
ditch
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rusty nuts
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| posted on 14/6/12 at 06:37 PM |
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Just to go against the flow, sort of , I might be tempted to straighten it out before cutting it out. At least that way the other chassis members
will be back in position if they are out now?
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MikeRJ
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| posted on 14/6/12 at 06:51 PM |
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quote:
Originally posted by David Jenkins
Now - are those air-powered reciprocating saws any good? It's not going to be easy to get in there with anything else, and I'm always
looking for an excuse for new toys!
They are very useful bits of kit for these sort of situations where there simply isn't room to swing a hacksaw around. Good for chopping
exhaust sections out as well.
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Alan B
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| posted on 14/6/12 at 06:56 PM |
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quote:
Originally posted by rusty nuts
Just to go against the flow, sort of , I might be tempted to straighten it out before cutting it out. At least that way the other chassis members
will be back in position if they are out now?
I'd agree with this if it's not too bent or the walls of the tube aren't buckled especially if you can safely get some heat into the
affected area.
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bi22le
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| posted on 14/6/12 at 07:35 PM |
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quote:
Originally posted by Alan B
quote:
Originally posted by rusty nuts
Just to go against the flow, sort of , I might be tempted to straighten it out before cutting it out. At least that way the other chassis members
will be back in position if they are out now?
I'd agree with this if it's not too bent or the walls of the tube aren't buckled especially if you can safely get some heat into the
affected area.
This was my gut feeling too after the reading the OP. The member does not look too bent so have a good look in it. Any signs of fracture or
creases?
If your still not at ease after bending it back due to knowing its been bent once then reinforce it in a way thats easier to do. Then if your going
to do that or be worried about a slight weakness then where do you stop? You must be confident all your welding is 100% perfect and the chassis is
great in an impact to be worried about the potential weaknesses shown by
Does welding, applying heavy force, reheating through removal and then rewelding another bit on not just weaken the other members anyway?
Just my imidiate thoughts
Biz
[Edited on 14/6/12 by bi22le]
Track days ARE the best thing since sliced bread, until I get a supercharger that is!
Please read my ring story:
http://www.locostbuilders.co.uk/forum/13/viewthread.php?tid=139152&page=1
Me doing a sub 56sec lap around Brands Indy. I need a geo set up! http://www.youtube.com/watch?v=EHksfvIGB3I
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rusty nuts
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| posted on 14/6/12 at 08:23 PM |
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I've got an air saw thats a bit better than the pistol grip type you can borrow if you want it David but I won't be back at work until
Monday. Going to arrange to meet up with Paul in the very near future and can take it along then if thats any help
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David Jenkins
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| posted on 14/6/12 at 09:08 PM |
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Thanks Mel - but I've been thinking of getting one of these for quite a while, so now I have an excuse!
As for bending back - the only way I'm going to be able to do it without stressing other chassis members is to put a block of metal on one side
and whack it with a heavy hammer. I could hook a bar onto it to pull it back into shape but then I have to provide a fulcrum somewhere on the
chassis, which is likely to risk damage to something else.
I suppose I could put a really solid bar on the concave side and use a strong clamp to pull it into shape...
Decisions, decisions...
I'll keep thinking about it (and listening to the opinions of others) while I strip everything down ready for action. I've got a day or
two to go yet.
[Edited on 14/6/12 by David Jenkins]
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nick205
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| posted on 14/6/12 at 09:14 PM |
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Not wanting to be down beat David, but after a similar incident in my Indy I thought I'd got away with a bent lower wishbone. On full
inspection, pretty much all the tubes on that front corner had some deformation. This took a steel rule to identify properly. In my case the damage
was very minor and a replacement wishbone was easily fitted. However the front geometry was thrown out quite significantly.
I'd strip it back and check very carefully for any further damage bfore starting repairs.
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David Jenkins
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| posted on 14/6/12 at 09:23 PM |
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I've already been round with a straight edge - it's OK apart from the obvious damage, thankfully. I've still got to go over the
engine compartment with a tape measure though, in case it's gone out of shape. I still need to have a closer look at some components and welds,
just to be sure.
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iank
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| posted on 14/6/12 at 09:47 PM |
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Sorry to read about the bang, it's always a horrible feeling.
Is that powdercoat on the bent tube? If so I'd be concerned for the longer term as coming off in big sheets means it's not sticking to
the metal well enough and any water getting through a scratch/pinhole can rust silently underneath it. It will also make the repair more of a pain ;(
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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mark chandler
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| posted on 14/6/12 at 11:15 PM |
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Smashing with a big hammer is not the way to go, the secret to straightening things is to do the opposite of what caused them, pull or push in the
opposite direction.
Use a slide hammer bolted to the bracket that was pushed to deform in the first place, I think you may be surprised at how easily this may straighten
out. You may need to put in a cut with saw on the inside face and 3/4 way through at the apex of the bend so it flexes back with greater ease, then
just weld this closed and grind flat.
If this fails get some blocks of wood and arrrange on the opposite side of the chassis so you can push out with a ram or small bottle jack.
If still worried then brace across the suspension brackets, use an off cut and weld an eye on each end so you can bolt across the frame and brace to
bracket to its opposite side on the bush bolts.
Even if you decide to replace you really need to straighten in the first instance to reset the chassis.
Regards Mark
[Edited on 14/6/12 by mark chandler]
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coyoteboy
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| posted on 15/6/12 at 12:54 AM |
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I think several other tubes in that area will be bent also, personally I'd check all nodes and remove elements back to the next unmoved node
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