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Fury rebuild - chassis and engine cross bracing spider almost done, but with issues (oblig pic)

FuryRebuild - 29/7/12 at 07:52 PM

Here's a picture of my cross-bracing spider - it meets the new diagonals nicely.

I've made it with rose joints to aid location, and have used brackets top and bottom to secure each corner to the chassis. I used upper and lower brackets because:

I had thin steel handy so two brackets supported the rose joint well - not loaded in single shear
as a bonus, it gives me gussets on this part of the chassis
i needed it to be demountable so I could get the engine out

Of course, I welded thickening pieces to each plate so the locating boat had 4.5mm of bore per plate for the shank to go through.

Now, to the tricky bit. My gnawing suspicion that I'd welded myself into a corner came true.

Using top and bottom plates on all corners means I can't get it out if I put the last two plates in the final corner - with three corners in as you see them now, the spider pivots out on the top left rose joint in the plane of the spider, then when the two bottom rose joints come out, it will pivot through 90 degrees and they're all out. However, the final rose joint in, the final link bangs against the two cross members nearest to it.

My thinking on how to proceed is as follows:
either make the final link a turnbuckle (no issue) so I can just narrow it until it pops out of the top left bracket, then all is good but it doesn't look like an amazing spider all nicely fitting where it should. The final link is only tacked in. There is no weakness in the arrangement here - the turnbuckle is only loaded in compression so it's safe as houses.
or finish the tack and only put a bottom plate in for the top left and cut the bottom plate out of the bottom right. Then this gives me a spider that will pivot on the top-right and bottom-left and come out that way. However, this means I have my rod ends loaded in single shear and should probably cut the (now to be) single plates out for thicker plates (I don't have any thicker steel at the moment).
or cut a section out of the top of each bracket so the spider can be lifted out, and use bolts and a new plate to then put the section back in. Advantages - I get to have a normal looking spider, and end up with all rose joints loaded in double shear. However it's a lot of faff and I end up with bolts mounted in shear. meh.

any thoughts?

Description

sebastiaan - 29/7/12 at 08:00 PM

Can you not make the last corner top plate "bolt on" using a few crush tubes? Put the spider in, bolt on the last top plate, bolt spider to plates, done?

MakeEverything - 30/7/12 at 08:32 AM

or turn the joint through 90 degrees, and weld the plates in a "Slot in" formation to the gussets?

FuryRebuild - 30/7/12 at 08:55 AM

Dear MakeEverything

I see now that I had kept myself unnecessarily constrained to 2 dimensions. It may still mean cutting out a bracket though, and it's a pity because the welding is really neat. I find it very easy to be neat with tig on the bench, but it's far harder on the car.

DH2 - 30/7/12 at 09:01 AM

Very bling, but can't help feeling you'd be better off ensuring the suspension mounts are less floppy...

DH2

FuryRebuild - 30/7/12 at 09:11 AM

Hi DH2

I think they're fairly crucial, and if they're shiny so much the better. The fury engine bay lacks lateral strength across the bay and means the suspension struggles sometimes due to lack of front-end tortional rigidity. I've invested in anti-roll bars, new shocks and springs and I want to give them the best chance to operate. Looking at it from the top down, the forces now go where they should and don't end up in the middle of a member.

Saying that, reinforcing the front dangly corner where the rocker arm goes is on the list. It's a classic fury weak point. I've noticed the latest chassis are gusset there, but my anti-roll bar goes through that. I have some gusseting in underneath (not visible in the shot) but am looking to tie more in.

Finally, the bottom wishbone and top rocker brackets are coming off, to be replaced with height adjustable brackets on the top, and the bottom wishbone is being replaced for one with captive spherical bearings, rather than the current arrangement (LDV ball joint, 3/4UNF loaded in bending).

This will strengthen the front up to help me retain an accurate geometry.

sebastiaan - 30/7/12 at 09:57 AM

quote:
Originally posted by MakeEverything
or turn the joint through 90 degrees, and weld the plates in a "Slot in" formation to the gussets?

how would you get the bolt through if you want tho keep the spider in the same horizontal plane as the upper chasis members?

FuryRebuild - 30/7/12 at 10:00 AM

I'd still struggle unless the opposite (bottom right) bracket was also vertical.

The advantages are easy extraction - the disadvantage is that I'd lose the gusseting I've got for free (the main reason why I went horizontal in the first place).

The more I think about it, the more I think welding a pair of brackets onto the spider and then running a turn-buckle to the top left corner seems the right way. The turnbuckle can just then be loosened off, wound in until one of the rose joints pops out, and then the whole arrangement will come free as it does now. Disadvantage is aesthetic only.

FuryRebuild - 7/8/12 at 11:25 AM

Thanks to everyone who posted advice on this thread - I'm pleased to announce I've sorted the problem, and in most of these situations, the solution is really simple. It came to me when I was winkling the spider out from the three existing brackets; I had somehow got my head stuck in the idea that all the brackets had to be the same shape, and when I was extracting the spider I found that it just needed a slightly different shaped bracket to come out.

Here it is:

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The welds are fine to my eye, and looking at the blue line, I have the temperature about right - it's not burning back too far. Of course I also get the extra rigidity of the gussets in place. What isn't visible in the picture is a cross-piece in place at the front in the vertical plane to give me some tortional rigidity.

I'm doing a dry-fit before I put in an extra cross-member infront of the engine which will mean the entire front suspension is now in a proper rigid box. I also have a (narrow) route to run some 10mm tube from the bottom of the chassis to the very front left hand and right hand corners to support the rocker arm.

and here is the spider in place, all finished, waiting for the powder coating.

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