The Black Flash
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| posted on 24/10/12 at 02:46 PM |
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OK, so I'm basically back to the bushing then, which is fine. I can easily chamfer the edges so that's no problem.
The reason I'd like to use a turned bush rather than a simple crush tube + washer is so that I can tap a thread on the inside of the bush. Then
I'll bolt straight into that (with locktight) and not have to have nut + bolt sticking into my footwell.
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T66
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| posted on 24/10/12 at 05:20 PM |
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Your second idea works better for me.
Personally I would plate all four faces of the chassis, well beyond the hole, however my fabrication is always belt & braces.
Reflecting on it, if you want belt & braces without removing the body, slip over a 3 sided box over the lower of the chassis, get the side plates
as high up the hole as you dare, and weld everything.
4x2 box with the top cut off might slip over, and would be simple.
[Edited on 24/10/12 by T66]
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coyoteboy
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| posted on 24/10/12 at 06:37 PM |
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Personally I'd replace the member and find a better solution rather than supporting something requiring a chuffing great bush mid-span if at all
possible.
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T66
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| posted on 24/10/12 at 07:06 PM |
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quote:
Originally posted by coyoteboy
Personally I'd replace the member and find a better solution rather than supporting something requiring a chuffing great bush mid-span if at all
possible.
The whole member doesnt need replacing, that is a large clean hole in a otherwise clean chassis, if the access for welding is workable, theres no
reason why a nice tight fitting U section couldnt be welded ontop. Bear in mind you could have it 30cm either side of the hole if space/shape permits.
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coyoteboy
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| posted on 24/10/12 at 07:25 PM |
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Doesn't NEED to be, no, but it's a bit of a botch to plug it. I just like a neat clean solution rather than a patch that'll probably
take more work to do than doing a direct swap.
[Edited on 24/10/12 by coyoteboy]
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T66
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| posted on 24/10/12 at 07:56 PM |
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I dont think my suggestion is a botch, its a solution. By the time its painted most wont notice it. ....
The classic car guys repair far worse than that
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coyoteboy
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| posted on 24/10/12 at 08:25 PM |
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I do. We disagree. Not the end of the world though, I don't disagree it would work but it introduces lots of issues (vastly different wall
thicknesses being different stiffnesses, harder to weld together properly (getting enough heat into the larger part to get good penetration) etc.
Plated it'll stand proud so the bodywork around it won't fit as well. Just loads of little reasons I'd replace it fully rather than
fix, but I'm a bit perfectionist.
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The Black Flash
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| posted on 24/10/12 at 08:35 PM |
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quote:
Originally posted by coyoteboy
Doesn't NEED to be, no, but it's a bit of a botch to plug it. I just like a neat clean solution rather than a patch that'll probably
take more work to do than doing a direct swap.
[Edited on 24/10/12 by coyoteboy]
Well, the guy who designed the chassis said that a welded bushing would be "quite a nice solution" and that replacing the whole member was
really not required.
If it were, I'd do it. But at this point, to do that I'd have to remove the floor, scuttle, and arches, which would all probably come
off ok. But then also probably the inside rear panels, which would also mean the rear bulkhead panel, and the inner & outer side body panels.
Removing these would be destructive or damaging and I'd probably have to replace some or all of them. I could really do without that scale of
setback if possible.
Having trouble to muster the enthusiasm to do any work on it at all at the moment, it's gutting to be chopping bits out 
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T66
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| posted on 24/10/12 at 08:40 PM |
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quote:
Originally posted by coyoteboy
I do. We disagree. Not the end of the world though, I don't disagree it would work but it introduces lots of issues (vastly different wall
thicknesses being different stiffnesses, harder to weld together properly (getting enough heat into the larger part to get good penetration) etc.
Plated it'll stand proud so the bodywork around it won't fit as well. Just loads of little reasons I'd replace it fully rather than
fix, but I'm a bit perfectionist.
Boring world if we all agreed
but in respect of you being a perfectionist, I am most definitely the opposite 
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mcerd1
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| posted on 25/10/12 at 08:50 AM |
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quote:
Originally posted by The Black Flash
Well, the guy who designed the chassis said that a welded bushing would be "quite a nice solution" and that replacing the whole member was
really not required.
can't argue with that, he's a first class old school engineer 
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The Black Flash
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| posted on 25/10/12 at 11:22 AM |
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Made some test pieces last night from smaller tube, and tested them against normal tube and tube with big holes drilled in it via the extremely
unscientific method of a large hammer. I was pleased to confirm that a welded bush doesn't seem to noticably weaken the tube, (unless the weld
is crap of course.)
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daviep
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| posted on 25/10/12 at 11:31 AM |
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quote:
Originally posted by The Black Flash
Made some test pieces last night from smaller tube, and tested them against normal tube and tube with big holes drilled in it via the extremely
unscientific method of a large hammer. I was pleased to confirm that a welded bush doesn't seem to noticably weaken the tube, (unless the weld
is crap of course.)
Good stuff, looks like you are making are nice job of the build.
Cheers
Davie
p.s. I'm sure some of our more theoretical builders will be along to tell you that your test results are not valid as the problem will be
"cyclic stresses" or something else with bigger words.
“A truly great library contains something in it to offend everyone.”
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Minicooper
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| posted on 25/10/12 at 11:37 AM |
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Just weld it up, easy, 10 minutes and your done.
Cheers
David
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mcerd1
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| posted on 25/10/12 at 12:03 PM |
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quote:
Originally posted by daviep
p.s. I'm sure some of our more theoretical builders will be along to tell you that your test results are not valid as the problem will be
"cyclic stresses" or something else with bigger words.
translation: hit it lots of times with a smaller hammer and see what happens 
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sebastiaan
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| posted on 25/10/12 at 06:54 PM |
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quote:
Originally posted by mcerd1
quote:
Originally posted by daviep
p.s. I'm sure some of our more theoretical builders will be along to tell you that your test results are not valid as the problem will be
"cyclic stresses" or something else with bigger words.
translation: hit it lots of times with a smaller hammer and see what happens
No, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no,
no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no,
no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no, no,
no!
You NEVER use the smaller hammer
On a more serious note; if you are comfortable with the welded in bush solution AND you did a succesful test then go for it. Our contraptions are
actually quite crude in design, lots and lots of stress raisers and "incorrect" spaceframe constructions everywhere (well, on a locost at
least; I'd assume a DAX is not THAT much better) yet we see very few chassis failures. Just keep an eye on the repair at regular intervals and
it'll be fine.
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The Black Flash
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| posted on 25/10/12 at 09:36 PM |
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quote:
Originally posted by daviep
quote:
Originally posted by The Black Flash
Made some test pieces last night from smaller tube, and tested them against normal tube and tube with big holes drilled in it via the extremely
unscientific method of a large hammer. I was pleased to confirm that a welded bush doesn't seem to noticably weaken the tube, (unless the weld
is crap of course.)
Good stuff, looks like you are making are nice job of the build.
Cheers
Davie
p.s. I'm sure some of our more theoretical builders will be along to tell you that your test results are not valid as the problem will be
"cyclic stresses" or something else with bigger words.
Oh, I'm under no illusions that it's a valid reflection of the real stresses in a frame. But it made me feel better because it seems as
resistant to bashing as an undamaged tube, which I can assume will translate to reasonable strength elsewhere. Plus I got to bash something
Off for the weekend, but one side now stripped, so I'll get to welding it next week. Thanks all for the help, if nothing else it's been
good to talk about it.
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