Triumph Sports Cars

engine swaps and other performance upgrades, plus "factory" V8s (Stag and TR8)

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Richard/SIA
Richard Brengman
No. Nevada
(361 posts)

Registered:
01/17/2014 07:47PM

Main British Car:
1969 Triumph GT6+ 225" Buick V6

TR6 frame strengthening?
Posted by: Richard/SIA
Date: August 26, 2020 01:35AM

With all the modified TR6's here I expected to find a "Sticky" for frame reinforcement.
Have to repair a bent one and looks like a body-off job.
So if I'm going to be into it that far I want to upgrade while I am at it.
"Upgrade" not a new blank check frame.

I know I've seen mention of "Weak" area's around the diff mount and trailing arms, others?
Details on reinforcing the weak spots?


88v8
Ivor Duarte
Gloucestershire UK
(804 posts)

Registered:
02/11/2010 04:29AM

Main British Car:
1974 Land Rover Lightweight V8

Re: TR6 frame strengthening?
Posted by: 88v8
Date: August 26, 2020 05:01AM

The whole frame is rather flexible, but the classic failure point is the diff mounts. The open box format was weak and suffers from stress cracks . Very hard to see with the diff in place.
The solution is to box them in by welding in little plates to close the box, ideally leaving a small gap in each corner to allow a tiny bit of flexibility, and let the water out. Can be done by a good welder with the body on, but easier off.
Moss have a kit that includes new studs. [www.mossmotoring.com]
This actually shows the mounts fully boxed including the corners, which just creates a future rust point, better I think to leave the bottom corners slightly open and include them in the routine wax treatment.

Mine was done many years ago and I can't recall from whom I bought the kit, the UK TR6 forum will be up to date on that, or of course 6-Pack.

Here's an ancient discussion of some more extensive reinforcement, some of the links may be bad.[www.mg-cars.net] but it will give you the flavour if you want to go that far.

Trailing arms... two problems, first that the studs that fasten the hubs to the trailing arms are UNF, 5/16 iirc, and strip very easily even at the correct torque. Solution is to tap them 3/8 UNC. [www.pattonmachine.com]
The other problem is chassis rot in the outriggers that hold the trailing arms. Replacements are available, not worth patching them.

You may also find rot on the tops of the inner chassis rails, the cruciform itself, the top breast plate and perhaps the tops of the outer chassis rails. Hopefully not!

If not already fitted I would recommend Richard Good's adjustable t/a brackets which are a much better method than the factory shims [www.goodparts.com]

Hope this doesn't turn into an epic.

Ivor


IaTR6
Dennis Costello
Central Iowa
(169 posts)

Registered:
12/29/2007 02:53PM

Main British Car:
'73 TR 6 '97 Explorer 5.0

Re: TR6 frame strengthening?
Posted by: IaTR6
Date: August 26, 2020 11:54AM

Richard,
I will add what I have done to all the information out there.
The differential mounting points are a definite area for improvement, but don't add to chassis stiffness. I have added a 1/8" plate along the chassis rails on each side, from the differential bridge upright to forward of the trailing arm chassis section attachment. I added gussets to the chassis outer rail to trailing arm mounting connection. I constructed a "roll bar" that is essentially a chassis stiffener that mounts to the differential bridge, and the trailing arm chassis mounting
sections. The hoop going from side to side on the differential bridge has a diagonal brace, and two legs that extend through the floor to the trailing arm chassis section. These forward braces have a bolted web just above the parcel shelf floor to tie the hoop and diagonal braces together.
I am neither an engineer, nor have I had an analysis done to see if any of this helped, but I can jack up the rear of the car under the T shirt and still open
and close the doors without an issue. I can also jack either wheel off the ground and also still open either door without issue. So, I guess my "shade tree"
design may have helped. Look under project journals, and scroll down to Dennis' TR6 project, and in the pictures you will find what I'm describing.
The tubing is 1018 1 3/4" DOM, and a local race shop did the bends for me.
Dennis


Richard/SIA
Richard Brengman
No. Nevada
(361 posts)

Registered:
01/17/2014 07:47PM

Main British Car:
1969 Triumph GT6+ 225" Buick V6

Re: TR6 frame strengthening?
Posted by: Richard/SIA
Date: August 26, 2020 09:32PM

Well I do have my own tube bender.
Looking into buying a complete used chassis.
That would let me do the mods before taking the body off so should allow a much faster rebuild.
As I have read the shallow U closing the frame is only tack-welded. So it would seem time with the MIG welder to fully weld the seams would also be an improvement?


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