Chassis strengthening TR5

[dave bailey]

The TR5 rebuild is getting serious now, having prepared the outer body panels, I'm about to start rebuilding on the chassis. Although the

Chassis has been strengthened in the normal places, it's been suggested that the spring support flanges either side of the main bridge

are susceptible to cracking. Can the assembled experts tell me if there is an approved strengthening scheme for these flanges. I'm thinking of

 welding in a more or less vertical triangular section which would fill in the upswept section at the rear of the flange. I'm not sure if this would

interfere with the spring. What do you think?

Thanks. Dave. 

[jerrytr5]

I believe a couple of gussets are welded in here if you convert to damper in spring mod.

Don't believe it's a problem otherwise.

Jerry

[dave bailey]

Thanks Jerry.

I will be using a telescopic damper on the rebuild, although I don't think that will matter one way or the other. I can't understand why, when they designed the top spring mounting, they made it weak, by having a very shallow return on the rear flange, it seems to serve no purpose and makes the whole structure vulnerable to cracking. Anyway I am thinking about making a 'saddle', of three mill steel to fit over the end of the bridge where the spring locates.

Dave.

[RogerH]

Hi Dave,

 when people fit the Revington 'coil over damper'  that end of the bridge is boxed in with TRiangular fillets.

That appears to work well.

Have you fitted plates to the Diff support pins    on the top of the bridge. - and boxed in the brackets below it 

Roger

[stuart]

They do crack but thats usually due to the fitment of that shock in coil setup, Ive had to weld up a few though I believe the newer kits contain more strengthening. A bit of strengthening may not go amiss with the state of the roads these days. This one I came across a few years ago that had already been partly welded up.

Stuart.

 

[dave bailey]

Thanks Roger, Yes I have done all the strengthening to the diff pins. I will be fitting Spax dampers, but not the coil over shock system. Stuart, thanks for the photos, I misunderstood where the potential cracking could occur, ie not at the spring support dome, but further inboard. So I'm going to weld vertical plates either side of the bridge to cover that area. Thanks. Dave.  

[Malbaby]

Dave...Have you considered strengthening the chassis where the back end of the chassis flexes and twists at the rear of the T shirts.

Hard to see from the pics...have you strengthened the rear diff bridge.

The support braces for the front shock towers can also be problematic.

Edited February 3 by Malbaby

[dave bailey]

Hi Malbaby. I haven't put any additional strengthening in the area to the rear of the 'T shirts' I could I suppose triangulate the chassis members, although I'm a bit wary of welding bits in which might interfere with or be seen when the body is mounted. The thing with strengthening I guess is where do you stop? The chassis has pretty much all the normally recommended strengthening done, including extra braces between the two bridges at the top. The turret support struts are fine (replaced one, other okay). I'm tempted to say now that it's good to go, and move on to the next phase which is mounting the chassis on a home made moveable jig, and making a start on rebuilding the body on it. Incidentally, on that subject, does anybody have a rough idea of how much a full engine and gearbox weighs? Because I aim to use sandbags to weigh the chassis down to simulate these.

Thanks. Dave. 

[stuart]

1 hour ago, dave bailey said:

Hi Malbaby. I haven't put any additional strengthening in the area to the rear of the 'T shirts' I could I suppose triangulate the chassis members, although I'm a bit wary of welding bits in which might interfere with or be seen when the body is mounted. The thing with strengthening I guess is where do you stop? The chassis has pretty much all the normally recommended strengthening done, including extra braces between the two bridges at the top. The turret support struts are fine (replaced one, other okay). I'm tempted to say now that it's good to go, and move on to the next phase which is mounting the chassis on a home made moveable jig, and making a start on rebuilding the body on it. Incidentally, on that subject, does anybody have a rough idea of how much a full engine and gearbox weighs? Because I aim to use sandbags to weigh the chassis down to simulate these.

Thanks. Dave. 

I would be wary of going too far with extra strengthening unless you knew what difference it would make to stressing other parts of the chassis.

Do fit drain holes at the bottom of the turret support struts as they have a habit of rotting there.

Ive done a fair few major body off restos and never worried about weighting for engine and box. If the chassis is good then its not going to bend with the weight. Just make sure the chassis is level front to back and side to side and supported on stands at the axle points.

Stuart.

 

[Tom Fremont]

My spring outriggers cracked where Stuart's photo show, and when the body was lifted off stood straight up. I had driven for years with them cracked but the rear deck apparently withstood the spring force; I thought is was non-issue when I saw them initially, the cracks having just started.

They were reinforced with plates as noted above and the pin locations reinforced in various ways, with heavy washers around the pin tops and boxed in U-channels.

The corrosion evident on the chassis at the beginning makes reinforcement all the more urgent.

TRIUMPH was assiduous in their efforts to save weight; this is a rare example of where the design fell short. RATCO's replacement frames weigh 40lbs more.

[Bfg]

Dave, if it's of interest I had my TR4A replacement chassis modified to better support the spring seats, in the way you originally suggest.  ie., triangular gusset plates up the tower legs ...and they do not interfere with the springs. . .

 

. . .more < Here > and in adjacent posts of that blog.

Pete 

 

 

 

[dave bailey]

Thanks for your input and pictures Stuart. Blimey Pete! I hadn't seen the pictures of your TR4A chassis mods before. It kind of puts my efforts to shame!. Now again I'm wondering whether I should do more. I have a scrap TR5 chassis which I could cut sections of chassis rail off in order to do some of the work you show, but my welding skills are not as good as MT Classics, and I would also be concerned, that without a chassis jig to keep things fixed, with that amount of welding, there's a good chance that I would cause some distortion. I'll have to do some more thinking! Anyway thanks, I'll let you know what I decide

Regards. Dave.   

[Bfg]

No problem Dave, I hope it's useful. 

Please be aware though ; some owners are doubtful insomuch as they fear stiffening one part of a structure unwittingly transfers stress loads to another member or intersection. That of course is true ..so some engineering thought ..and balance, regarding load paths and load extremes, is called for.  Arguably this is mostly common sense.  The counter to such cautionary objection is that thoughtfully placed triangular gusset plates and additional beams help support (minimise twist and therefore fatigue) and distribute point loads from weak spots ..particularly so on the IRS rear chassis around where its suspension arm and springs are mounted.  Others may regard the extra plates as simply adding unnecessary weight, while others still are adverse to altering the original, whether because they don't trust structural changes or for sake of resale value 

..just so you know.   

As for myself,  I'm very happy with this chassis, and so if I were doing it again - I would do the same  ..except that ; the so-called T-shirt  plate, would have been welded on rather than, as I later discovered, goo'd in place (I thereafter through-bolted it).  Additionally, I would have added the car's additional body mounts ; two more in the footwells / under the bulkhead, as indicated < here >.  These, I added to the outside of the chassis leg are a mirror of those on inside the same chassis leg.   And again I've added additional body mounts either side of the rear propshaft tunnel < here > ..close as I could to the body tub's vertical step, over the rear axle. Although they are there now, it would have been simpler to do these while the body was off.

Regarding distortion..  generally speaking, if all parts are well supported, clamped (even without a proper jig - stout beams can be used), &/or weighed down to the supports, then chassis repair distortion happens through excessive heat and subsequent weld-shrinkage ..from continuously welding on one side of a beam before the other sides are even stitch welded.  However, with good weld practice of all around tacking and then alternating localised stitch-welds ..around all sides, then everything is pinned in place and distortion is minimised*.  You'll perhaps note that where I've added a triangular gusset plate on the top face of the chassis, then there's also one on the underside face.

* I say 'minimised' because, even in production, a chassis will ping slightly as it is released from a jig.  It's all a matter of it being allowed for, and it remaining within tolerance. Even then, the suspension as well as the body mountings do  accommodate considerable deviance  ..as was evident in my car's cracked chassis which was no longer within manufacturing tolerance ..and yet it still worked, and surprisingly well.   How it might have stood up to an accident is an all together different matter     .. just one aspect I sought to address. 

Others here have long and varied experience of these cars, through professional activities of repair and restoration, &/or through on or off-road racing and hill climbs. Their combined and vast experience should be taken to heart, and balanced against my or anyone else's views.

Best regards, Pete

 

Edited February 6 by Bfg

[dave bailey]

Thanks Pete, I'm cogitating, (there's no law against it!)

[Harbottle]

Hi Dave, Hope the garage doors shut.

[TRier]

Hi Dave, I reinforced that front diff bridge. I had the same concerns as yourself, although I fabricated a new chassis I chose to retain the top part of that bridge and it was quite heavily pitted and I intend to have the facility to use telescopics so I had concerns about those two ends. I havent completed my restoration yet so I cant say how well the mods work but I'm confident they'll work well, in any case you can take anything useful from the photos or reject the concept as you see fit. 

Personally I think 3mm might be bit excessive, these are in 2mm and its more than enough. I did mock up with the spring in place before I finished forming and fixing these in place, like I said not drop tested in anger yet but definitely enough clearance for the springs in static condition at any rate. I'll post some photos of the mocking up process in a min.

[TRier]

As promised here is some photos of the mock up with spring clamped in place to ensure clearance. Hope its clear.

[Dave McDonald]

Dave, this is the reinforcing plate over the potential front bridge crack area where it sits on the upright box sections. 
Not a great photo but best I could get on finished car. 
Dave McD

[Dave McDonald]

Dave, another photo of whole new CTM chassis now under TR5 restoration which, if you blow it up, shows the similar reinforcement on back of front bridge over possible crack ares. 
Dave McD

[dave bailey]

Hi TRier. That's an interesting solution to the problem. Looks effective and makes you wonder why Triumph didn't do something similar when they designed the bridge! Hi Dave McD. I've actually done exactly what has been done to your CTM chassis, and might leave it at that,(although I'm tempted to do something similar to TRier's.) I see that you have joined the front and rear bridge in the same way as you did on the one you sold me. Having finished my cogitating I've, cooked up a scheme to reinforce the chassis a bit more, I'll put some pictures on when it's done. Dave.

[Tom Fremont]

A friend in his 9th decade with (3) TR6s, one with Eaton S/C producing over 200BHP at the wheels uses a block of wood stuffed into the RR differential mount to prevent the stud from upward movement when reacting the torque of the engine multiplied by (4) in 1st gear. He prefers cheap tires and relishes spinning the wheels on takeoff, the usual culprit in diff mount breakage ( an American specialty as this market always " knew " the TR6 was good for more than the emissions cars delivered ). The spring outriggers are another matter; not sure he's done anything with these apart from fitting stiffer, shorter springs which, if anything, ought to raise the prospect of cracking them. He does employ Toyota transmissions and Nissan differentials.

[TRTOM2498PI]

21 minutes ago, Tom Fremont said:

A friend in his 9th decade with (3) TR6s, one with Eaton S/C producing over 200BHP at the wheels uses a block of wood stuffed into the RR differential mount to prevent the stud from upward movement when reacting the torque of the engine multiplied by (4) in 1st gear. He prefers cheap tires and relishes spinning the wheels on takeoff, the usual culprit in diff mount breakage ( an American specialty as this market always " knew " the TR6 was good for more than the emissions cars delivered ). The spring outriggers are another matter; not sure he's done anything with these apart from fitting stiffer, shorter springs which, if anything, ought to raise the prospect of cracking them. He does employ Toyota transmissions and Nissan differentials.

That sounds a rather entertaining car.  Any pictures ? Does it still run the original TR6 diff ?

Cheers.

[BlueTR3A-5EKT]

3 minutes ago, TRTOM2498PI said:

That sounds a rather entertaining car.  Any pictures ? Does it still run the original TR6 diff ?

Cheers.

The diff is probably one that is done as a kit

https://www.goodparts.com/product-category/drive-train/differential-upgrade-kit-and-driveshafts/

[Tom Fremont]

Hi Tom,

He uses Nissan LSDs in at least (2) of his (3) TR6s. I don't have pictures; ought to get some. He also builds Nortons and has set at least one speed record with one.

My engine builder, a mutual friend refers to him ( John ) as " the Bert Munro of TRIUMPHs ". John would rather be known as the Bert Munro of Nortons .

[TRTOM2498PI]

51 minutes ago, BlueTR3A-5EKT said:

The diff is probably one that is done as a kit

https://www.goodparts.com/product-category/drive-train/differential-upgrade-kit-and-driveshafts/

Thanks, & yes, I have seen them.  I still run a TR6 with Quaife ATB, on my Ford RS Cosworth powered TR6 actually.