The Black Flash
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| posted on 23/10/12 at 09:42 PM |
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Disaster recovery
Hi all.
For reasons I'm not going to go into, persons, who will for now remain nameless, have drilled two BIG holes in each of my lower chassis rails.
Big as in, the full width of the box section. On the outside the holes are 21-22mm, on the inside, 11mm. This pic shows one of the holes, looking
from outside: (I've had to cut back some of the aluminium bodywork - a pain but at this point, the least of my worries). What this is for,
believe it or not, is just to take an M8 bolt.
Pretty bloody terrible I'm sure you'll agree. Obviously this is major damage to the chassis.
Now I have discussed this with Dax who made the chassis, and we have a plan to rectify it, which seems sensible to me. However given the knowledge on
here, I figured that it wouldn't hurt to get a few more opinions, or pointers for things to watch out for.
Current plan is to turn up a bushing to fit into each hole; 21mm at one end, 11 at the other. I did one tonight:
Then fit this in the hole, and weld around each end.
OK. That all seems sensible to me. I'm going to be doing some test pieces first, which I will be doing some destructive testing on as I want
to be sure. But can anyone else think of anything else I should be doing, checking, watching out for before I do?
Thanks in advance....
Andy
[Edited on 23/10/12 by The Black Flash]
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PSpirine
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| posted on 23/10/12 at 09:55 PM |
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That bush looks exactly how I'd rectify it. Just make sure that when drilling you didn't thin out the bottom or top surface of the tube -
otherwise I'd be inclined to weld a plate over those faces.
It's not the end of the world, particularly if it's not a "lightweight" chassis - there's certainly no reason it should
be any less robust than any other bolt mounting through a rail.
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britishtrident
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| posted on 23/10/12 at 09:59 PM |
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Personally I wouldn't choose weld such a heavy section component to a thin thickness member.
I would reduce the thickness on the larger end of the bush and or chamfer it this should make for a better chance of a good weld .
[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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mcerd1
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| posted on 23/10/12 at 10:18 PM |
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I'd be happy with that as long as you can get a good weld at both sides
where abouts is that on the chassis ?
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britishtrident
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| posted on 23/10/12 at 10:32 PM |
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This way the difference in material thickess of the material sections being welded isn't so great and there is less of a stress raiser at
the weld.
[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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designer
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| posted on 23/10/12 at 11:26 PM |
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I would not do that, too much stress, the proper way is to plate it.
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cliftyhanger
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| posted on 24/10/12 at 04:14 AM |
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I agree re welding the very heavy new bush to the chassis rail, it needs to be closer in terms of thickness.
I would also plate top and bottom, just to be belt and braces. The extra 100grams will not hurt you, but would be reassuring.
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Fred W B
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| posted on 24/10/12 at 05:58 AM |
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I would prefer to do it properly. Remove the body panel and section in a new piece of tube from node to node.
Cheers
Fred W B
You can do it quickly. You can do it cheap. You can do it right. – Pick any two.
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JoelP
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| posted on 24/10/12 at 06:42 AM |
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My more slapdash approach would be to either fit the bush if you need to mount a bolt in it, or just weld a plate over it. Its not ideal from a
technical point of view but a locost chassis is hardly a highly engineered thing anyway. The difference in material thickness might matter if it was a
wishbone but not here.
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welderman
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| posted on 24/10/12 at 06:57 AM |
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What Fred said 
but if its a total PITA then i would plate it
Thank's, Joe
I don't stalk people
http://www.locostbuilders.co.uk/forum/23/viewthread.php?tid=172301
Back on with the Fisher Fury R1
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mcerd1
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| posted on 24/10/12 at 07:07 AM |
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quote:
Originally posted by JoelPIts not ideal from a technical point of view but a locost chassis is hardly a highly engineered thing anyway
but this is a dax rush.....
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907
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| posted on 24/10/12 at 07:33 AM |
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OP, pic 3, looks just ripe for a TIG weld.
I would however first clean the rust from the inside and the paint off the outside.
I'd probably rig up a back purge then the resulting weld should be a flush butt on
the outside and a clean penetration fillet inside.
I have several M8 threads in my chassis consisting of a !3mm through hole with
12mm bar (threaded M8) TIG welded in both sides.
Cheers,
Paul G
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The Black Flash
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| posted on 24/10/12 at 07:44 AM |
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quote:
Originally posted by mcerd1
I'd be happy with that as long as you can get a good weld at both sides
where abouts is that on the chassis ?
That one is about 6 inches forwards of the front of the rear arch. The other is directly below the scuttle.
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The Black Flash
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| posted on 24/10/12 at 07:45 AM |
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quote:
Originally posted by britishtrident
This way the difference in material thickess of the material sections being welded isn't so great and there is less of a stress raiser at
the weld.
Now that is exactly the kind of thing I was after, thanks!
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The Black Flash
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| posted on 24/10/12 at 07:49 AM |
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quote:
Originally posted by Fred W B
I would prefer to do it properly. Remove the body panel and section in a new piece of tube from node to node.
Cheers
Fred W B
Asked Dax about that, and the advice was that that was not necessary. It's certainly something to avoid if at all possible as I'd have to
strip the car back down and remake the sides and floors...
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The Black Flash
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| posted on 24/10/12 at 07:54 AM |
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quote:
Originally posted by designer
I would not do that, too much stress, the proper way is to plate it.
Interested in this. If I plate it, which I have considered, I'll still need a 12mm bushing welding in. So I'll immediately have a 12mm
hole in my plate. Or I could do as I've shown above, and put a plate over the whole lot with just the 8mm hole in afterwards.
Edit - just thinking aloud here.
Or I could make up the plate for the outside, and weld the bushing to the inside of it on the bench, so the plate would only have an 8mm hole. Then
weld the assembly to the chassis. Would that be better than just a bushing, anyone know?
Thanks to all who've replied BTW, this is really useful.
Oh, and it wasn't me what made the hole as some seem to think. I do have my moments, but nothing this bad, yet.
[Edited on 24/10/12 by The Black Flash]
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daviep
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| posted on 24/10/12 at 08:11 AM |
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I'd be happy with your original solution or BT's refinemnet, it's maybe not 100% perfect design practice but I'm sure there
will be lots of bigger compromises made elsewhere.
Cheers
Davie
p.s it took less than 5 mins to work the why and the who
“A truly great library contains something in it to offend everyone.”
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chillis
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| posted on 24/10/12 at 09:17 AM |
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The integrity of the box section has been lost, the only safe way to repair it is either to plate each side or replace that part of the box section,
neither of which look like easy jobs.
Never under estimate the ingenuity of an idiot!
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mcerd1
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| posted on 24/10/12 at 09:53 AM |
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quote:
Originally posted by The Black Flash
quote:
Originally posted by mcerd1
I'd be happy with that as long as you can get a good weld at both sides
where abouts is that on the chassis ?
That one is about 6 inches forwards of the front of the rear arch. The other is directly below the scuttle.
ok I think I've worked out the cause of these holes too.... 
I've got the std. Dax parts for this, so mine will be mounted to the underside of the floor with big spreader plates instead
taking into consideration some of the other comments, plating the top and bottom flanges would be the belt and braces way to sort it (probably a plate
the same thickness as the tube and ~3 times the tube width long [~75mm] would sound about right to me - I'm no expert on chassis, but I do
structural steelwork design for a living so I'm assuming the principal is the same....)
but a nicly fitted and welded bushing like BT's one sould be all you need on the sides as long - as the welds are good (might be worth making a
test piece so you can cut it and check the weld penatration) TIG welding would best if you can
just watch out that you don't create an overly stiff point in the middle of the tubes, all that does is shifts the problem further along the
tube
[Edited on 24/10/2012 by mcerd1]
[Edited on 24/10/2012 by mcerd1]
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The Black Flash
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| posted on 24/10/12 at 10:30 AM |
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OK, so what about this:
I make a plate with bush welded on (left), then weld onto the chassis rail. (right) The RH side of the bush I'll just weld into the hole, the
LH (outside) will have a nice big plate.
If I did this, should I weld only the ends of the plate, or all the way around it?
ETA better pic
[Edited on 24/10/12 by The Black Flash]
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sebastiaan
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| posted on 24/10/12 at 11:12 AM |
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I'd weld all around the perimeter of the oustide plate if you go for that option. (and deliver a big bill to where it needs to go....)
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MikeRJ
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| posted on 24/10/12 at 11:17 AM |
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quote:
Originally posted by chillis
The integrity of the box section has been lost, the only safe way to repair it is either to plate each side or replace that part of the box section,
neither of which look like easy jobs.
Welding in the bush will restore the integrity of the box section. I agree with BT etc. that the outer flange should be made closer to the wall
thickness of the tube though.
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Mr Whippy
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| posted on 24/10/12 at 11:41 AM |
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tbh your orginal idea with the big boss thing is just fine, I'd put a chamfer round the edge to help with welding but it's well strong
enough, your meant to use a crush tube when putting bolts through rails anyway, that's just a mighty fine crush tube. Larger box chassis (landy
ones for example) are often full of webs & tubes to help stiffen them up, there's no reason it all has to be the same thickness throughout.
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britishtrident
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| posted on 24/10/12 at 11:56 AM |
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quote:
Originally posted by The Black Flash
OK, so what about this:
I make a plate with bush welded on (left), then weld onto the chassis rail. (right) The RH side of the bush I'll just weld into the hole, the
LH (outside) will have a nice big plate.
If I did this, should I weld only the ends of the plate, or all the way around it?
ETA better pic
[Edited on 24/10/12 by The Black Flash]
Rather than a rectangular plate it would be easier and better to start with a large washer, even a 14mm id standard industrial MS washer
should be OK as long as the welds are good but if you want you could start with a large od repair washer and trim it down with an angle grinder
after welding.
Because a washer has curve edge where it is welded to the tube it is slightly less likely to fail at the welded edges.
[Edited on 24/10/12 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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britishtrident
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| posted on 24/10/12 at 12:27 PM |
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14mm id washer
[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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