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NeilR

Chassis stiffening

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I recently had a computer issue and lost a lot of data, including all of the pictures and information I had on stiffening Triumph chassis. Can anyone point me in the right direction - I had found a lot about adding plates to join the two center sections etc, but the search function and google has not helped my in the past two days, clearly my google-fu has deserted me!

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There was a discussion on this on the old CT forum, the general consensus was to weld a t-shirt plates between the main rails in front of the differential as on a TR6. There was also some reference to an article in the TSSC Courier about Spitfire chassis which is apparently where the t-shirt plate idea comes from. IIRC there was an excellent photo of a Spitfire chassis being tested by hanging weights off it.

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I was sent this picture (of a Herald) when I considered the modification for our Herald estate. I had questions about whether or not it would be possible to remove the propshaft (without the gearbox)... We decided it wasn't worth the effort in the end, the chassis survived fine other than outriggers catching on rocks and the front foot wells.

I started to crudely model to see what difference it made using Solidworks for FEA... Might be worth exploring. I gave up on this at some point as I wasn't really sure if the results were useful (mostly playing around!). Hopefully this is in some way useful.
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I made a typo there, I meant to say there was an article in the Courier about strengthening a Spitfire chassis, which first proposed the idea of fitting the t-shirt plate....

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The floppy part of the chassis seems to be between the front outriggers and the suspension towers. I recently found a number of cracks in that area (I reckon largely down to the fact I had partially de-seamed the top of the chassis rails) To sort the issue, I have let in sections of 3mm wall 50x75mm box section each side, that will hopefully sort it, and not just put the stresses into the point where the box section ends (beyond the most stressed areas, and angled in an attempt to stop further issues)

People have suggested bars from the main rail by the front outrigger making a triangle up to the top of the front turret. Not convinced (yet!)

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Thanks for the replies. It was a Herald chassis I was thinking of, but few seem to bother with them, whereas I had found material and images of Spitfire modifications. Since they are so similar I thought those images would be a good guide.

I had thought to box the outriggers that come out from the chassis and then replace the sill section with some RHS steel ... the thing is almost falling off anyway. Then I thought to weld a 1.6mm flat sheet steel floor across from one sill to the other.

The front turrets do look pretty flimsy.

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Is a roll cage not a possibility?    The further from the bendy bits the stiffening can be, the more effective they are.

John Thomason wrote about Stiffness in the Courier in 2003 ("Twisted!", No.273, p.54) .   His article included a small, pyramidal frame, far smaller than a roll cage, that increased stiffness by 200%!

JOhn

 

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59 minutes ago, NeilR said:

Thanks for the replies. It was a Herald chassis I was thinking of, but few seem to bother with them, whereas I had found material and images of Spitfire modifications. Since they are so similar I thought those images would be a good guide.

I had thought to box the outriggers that come out from the chassis and then replace the sill section with some RHS steel ... the thing is almost falling off anyway. Then I thought to weld a 1.6mm flat sheet steel floor across from one sill to the other.

The front turrets do look pretty flimsy.

Chic doig used to sell well made outriggers and siderails, far superior to anything else I have seen (or used). Then box the siderail, and anything else?

I remember the article John refers to. I think it was quite intrusive? so may work for a racer, but not a roadcar.

I would concentrate on the section from the front outrigger to the turret,that is where the most gains are to be had. And possibly seam-weld the edges of the main rail chassis lips. And check how thick those mainrails are (some are very thin from corrosion, that was the final nail in the coffin for my vitesse. I had a real sense of humour failure)

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I saw that in my searching in the past week - the road rules in Aust have changed and a full cage is not possible without expensive engineering. I cannot encroach into the door opening, I can make a frame to go under the scuttle that bolts to the chassis and tie the front shock towers to - this will be 'body support'. I can make the sill RHS quite a bit higher and stiffer then the original channel and tie roll hoop and front body stiffening to it.

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Zetec the main rails seem OK, having be bathed in oil for many years. I'll know tomorrow when we get the rest of the body off the chassis.

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My main rails succumbed to the pointy hammer when I was checking for soundness. The rot was about a metre each rail, on the underside. They looked perfect from just looking, and had passed the MoT each year for the 13 years prior. I hope yours are much better.

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3 hours ago, NeilR said:

I saw that in my searching in the past week - the road rules in Aust have changed and a full cage is not possible without expensive engineering. I cannot encroach into the door opening, I can make a frame to go under the scuttle that bolts to the chassis and tie the front shock towers to - this will be 'body support'. I can make the sill RHS quite a bit higher and stiffer then the original channel and tie roll hoop and front body stiffening to it.

Do you mean that a cage, in the ordinary sense of a box of tubing, bolted to the bodyshell, is not allowed?   Unless you can point me to a webpage, I'd be interested in even a brief outline of what this regulation does.

My first Vitesse had fairly good looking main rails, but one had a level line of rust holes.   The drain hole in the dip under the drive shaft had blocked with underseal(!!) and the rail had filled with water, so that in store it rusted through where water and air met inside the rail!     Strangely only the inner panel was affected, and I was able to cut it out and replace.

John

Edited by JohnD

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Re. the rust, the Australian climate, on the whole, is a bit more benign from the rust generation standpoint than our own dank rock in the Atlantic.

That said...... one place to check for rust is the double skinned area where front and rear out-riggers overlap the main rails.  There can be catastrophic damage to the main rails there with just  bit of bulging showing externally.

Re chassis stiffening, the basic problem is lack of cross-links between the main rails and narrowness in the centre.  Can't do much about the latter, but the former can be addressed with extra links roughly in line with the front and rear outriggers (eg T-shirt addition as pictured above).  For Herald/Vitesse I've also considered joining the front and rear body sections permanently and creating a proper sill structure (additional to chassis side rails) and also adding a cross-member behind the heel board as used on Spit and GT6.

Nick

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Maybe it's also interesting to look at this old mailing list post (https://groups.yahoo.com/neo/groups/triumph_herald/conversations/messages/2675) from Kipping, he posted the findings from the Africa proving run. Now this will refer to the Mk.1 chassis, but a weakness was found:

Quote

Although not yet confirmed by measurement, it would appear that the fame is bending and taking permanent set directly in front of the front outriggers. In one instance a severe fractured occurred in this area on the 4-seater.

In the frame bend tests, carried out on the prototype frames, no weakness was apparent in this area. It is possible, however, that with the body fitted this weakness would be more apparent as the potential point of weakness corresponds with the point where assistance from the body would end. As it is impossible to deepen the frame at this point, the introduction of a corner gusset channel or alternatively, a frame insert may relieve this condition.

 

1 hour ago, Nick Jones said:

That said...... one place to check for rust is the double skinned area where front and rear out-riggers overlap the main rails.  There can be catastrophic damage to the main rails there with just  bit of bulging showing externally.


Thought you'd appreciate an extreme example of this. This chassis was the original for our estate - rotten and twisted. The diff area was also very bad as John mentions, due to blocked drain holes. The body wasn't as bad luckily.

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6 hours ago, zetecspit said:

I remember the article John refers to. I think it was quite intrusive? so may work for a racer, but not a roadcar.

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It would have been intrusive, but not that instrusive!  May have made a passenger a bit cramped!   So might as well go for a full cage!

John

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I don't think Gill would put up with that on the 10CR. Or even to the pub for lunch. Even Molly wouldn't fit, and she is tiny (and feisty)

Besides, that research didn't take into account the extra "stiffness" from the bodytub? I still maintain the bit to address (on a spitfire) is the section highlighted above from the factory findings. A herald/vitesse tub is floppier than a spit, so would benefit from some "extras"

And Nick, many years ago there was a lovely chappie in our local area. He wacked a box section across teh heelboard of his spitfire, and reckoned it tightened it up noticeably.  He was renowned as the go-faster chap in teh area, and I have no reason to doubt his findings. On a vitesse it would be an interesting idea, and probably worthwhile. As to sills, maybe replace the existing with 3mm wall box? flippin heavy though.

Anybody got thoughts on the idea of bracing the top of the turrets back to the main rails near where the front outriggers sit?

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We got the bonnet and coupe roof off today and more of the chassis was visible down near the gearbox. I gave it a bit of a hammering and it was sound enough - I'll know more when we get the rear tub and floor off.

Just for reference this is for the special body I have that you can see in this thread:

I have disc brake uprights from a spitfire and the swing spring as well.

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I had totally missed the other thread...

All looks very interesting,and I do love a bitza :devil: 

Yes, the better weather down under will hopefully taken much less of a toll on the metalwork. It seems to just feel damp over here most of the winter. Yesterday was very chilly, as I was fixing an old MIG in the garage. HAd to keep coming inside so my hands would work properly.

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We don't have artificial salting of the roads and in most places it is not as damp. My car sat under cyprus tress for a long time and gently rusted away - the coupe bodywork is falling apart. We lifted the roof off today without having to undo one of the bolts under the rear glass as it pulled through the tub.

I have been told that all Heralds sold in Australia had the Mk1 chassis in the export spec - supposedly this was stronger. More to learn. In any case the car has a Datsun 12A engine and four speed gearbox, which is the best thing about the car for the purpose it is being put to.

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I can't recall the exact details, but I do seem to recall that GT made mention of stiffening a chassis in the distant past?

I may well be not remembering the correct details, but did it not involve putting lots of tension onto the chassis before hard mounting the body tub? And it may have been a vitesse being discussed?

It may well be still lurking in a thread on here somewhere?

Cheers,

Phil

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