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Triumph TR6 - Tube shock Conversion

Hi folks,
I Was looking at pics of the tube shock conversion kit. It seems very simple.
My question is this. Is there anyone out there who happens to have the metal bracket plans for welding. Other then the shocks that can be purchased any where the brackets is what truly makes the kit.
My shop has 7 full time welders so I am sure I can whip something up.
Marcello

For your own car or for production? I got my kit from someone on Ebay for $125 with shocks. Hard to do R&D, pay a welder and buy shocks for less.
skikir

Marcello - I installed an excellent pair over 10 years ago and it would be easy enough for me take measurements and do a drawing (CAD?) for you. They are the best I have seen as they are independently strong enough to house the shocks, but have the added bonus of bolting through the wheel-arches as well. I'm sure this design also increases the tortional rigidity of the rear end as it triangulates the mounting points of the body across the rear axles. I can E you photos and if you like the look I'll do a drawing. A piece of cake to fabricate and install. I use Koni's with them.

Cheers

R
Roger H

Skikir,
For my own car, but hmmmm you just gave me an idea (rubbing my hands together...)


Roger,
That would be greatly appreciated. The moss versions are the pics I am looking at but if yours are no different and or better lets do it. CAD, SOLID WORKS, AUTO SKETCH...any of the large programs my team can read. If I can offer you something in return let me know,...maybe a spare set?
Marcello
Marcello

Marcello - could you please post a link to the Moss pics so I can compare (and also your contact details). I'll do the pics this weekend and follow up with the template if you like them.

Cheers
Roger
Roger H

Roger,
I hope this helps. Again I thank you.

Moss version
http://www.britishmotoring.net/bm0510/TubeShockConv.pdf

Moss version (here are the pics I have...page 29)
http://www.britishmotoring.net/bm0606/BM-0606.pdf

Herman van den Akker version
http://www.sonic.net/~geronimo/tr6/misc/hshocks.html

my email is:

my first name
at
wireworxdisplays
dot com

I look forward to hearing from you.
Marcello

Roger,

not so sure of the "added bonus of bolting through the wheel-arches". The stresses of the shocks is ment to be on the chassis only. I've seen several wheel arches cracked.
After seeing this I've installed the one that bolts to the standard mounting points only.
Eric de Lange

Eric – I do take your point and it is the very reason that I am happy to recommend the ones I used. They transfer almost the entire the force of the shocks back to the original chassis mounting locations via a 5mm thick steel plate. At the top of the assembly, there is pair of 150x100x3mm thick plates which are bolted inside and outside the wheel arch using 4x12mm bolts. As there is minimal lateral loading on the top mounting (my guess 5% which is absorbed by the top shock rubber anyway) there is little or no load transferred to the wheel arch.

I believe that the plate connections in the design that I have, actually strengthens the rear end of the car and helps prevent twisting of the chassis. At the rear of the car, the body and chassis are only connected via bolts through the floorpan which is thin gauge metal (1.6mm?) and rigidity of the body is reliant on the wheel arches, bulkheads with gussets at corners and some ribbing of panels.

This is a well-known problem with convertibles generally, as much of the tortional rigidity of saloons is provided by the roof structure. Almost all soft -top cars of the era which employ a separate chassis suffer from 'scuttle -shake' (twisting) of the body while cornering, particularly on uneven surfaces. There is not much opportunity to improve this in the TR6 but I think the brackets I have installed do help. While I have not seen this concept used in commercially available products, maybe Marcello could change that…!! ;-)

Best regards
Roger
Roger H

Roger,
Thanks for your pics. I do understand what you mean, and I also am concerned equally with Eric. Your version looks like most of the load is on the body, but looks can be deceiving. Am I wrong?

If this works out well I will be happy to market them and you folks get a great deal.
Marcello

Hi Marcello - almost the entire force of the shock is transferred axially/vertically (in the same direction as the shock absorber acts, through the 5mm thick steel plate) back to the two mounting points on the chassis for the original shock. There is little need for the top plate connection to the bodywork.
The top plate connection is greatly over-designed for the minimal horizontal loads it may get from the shock. The only horizontal forces are as the shock tries to rotate slightly due the trailing arm movement being 'hinged'. These are not 'coil-over' type shocks and the spring mounting is separate from the shock mount. I have installed Koni shocks (front and rear) and the threaded end fixings for these is no more than 1/4". This gives some idea of the lateral and tensile forces that the shock is designed for.

These brackets do more than just mount the shocks - they stiffen the rear of the car.

I have driven the car (125 Rear wheel HP)hard for nearly a decade and there is NO evidence of panel distortion or cracking in the wheel arches or body.

The reason I think this design is not more widely available, is that it is labour intensive to make. A CNC cutter would help things make things easier but few 'backyarders' have this luxury. For the eBay dealers, it would not sell as the price would be substantially more than inferior alternatives. You have 7 welders at your disposal so it seemed ideal for you.

No problem if you have your concerns about the design. I think it's probably the best of the few that I've seen available but the weight of it could be a concern to anyone wanting a lightweight solution for (say) a race car.

Again, I am not qualified as a structural or mechanical engineer, but the study of engineering I did at university comforts me in the decision to use them - I put my life on it!!!

Kind regards
Roger

Roger H

I am sold on it.
I also have a laser cutter in our plant so maybe that would be faster and cheaper then CNC.
One last note:
My buddy here in town owns a 72 TR6 with fibre glass fenders, I take it this won't work for his conversion..??

I look forward to your drawings.
By the way I do owe you something. I will compensate you if I get these rolling into production.
Marcello

Of the various tube shock conversions out there, the best of the bunch are the three piece per side set up as sold by Moss and the "coilover" set up from Revington TR. While the Revington kit does indeed insert the damper through the spring, it does not feature adjustable spring perches.

The advantage of the three piece set up is that it requires some careful hole drilling, but is a bolt on set up (unless like Marchello here, you intend to fabricate the brackets yourself). The disadvantage is that if you wanted to run a rear anti-roll bar, it would have to a low mount one. A fairly minor disadvantage.

The advantage of the Revington TR "coilover" set up is that it will allow use of a high mounted anti-roll bar and it is easy to set one of those up to be adjustable. The disadvantage of the Revington kit is that much more fabrication type work and modification work must be performed to install it. The upper rear cross bar must be gusseted, a reaction plate for the top damper mount must be welded into the cross bar, the trailing arm will need the hole in the spring pan enlarged somewhat and the lip cut back to accomodate the damper, six satellite holes must be drilled in the trainling arm spring pan to install the lower damper mount and a hole will need to be drilled to get to the damper adjustment screw if you wish to take advantage of that feature.

One other thing on the Revington kit, while all of the mount and reinforcement pieces are first rate, the hardware bits I felt were on the cheesy side (sorry, I shouldn't be insulting cheese like that). Things like fully threaded screws instead of screws selected by grip lengths, 90 degree counter sinks instead of 100 degree counter sinks, etc. All it took was rounding up some good hardware, but for the price and given how nice everything else was, it seemed to be something that I should not have had to do. Hardware misgivings aside, I would still recommend the Revington kit to anyone with the skills and equipment to install it.

As for the last question regarding fiberglass fenders, as long as we are talking about the fender that is exposed as bodywork it should not be a problem as the inner structure would remain steel. If he has glassed in the inner fender/wheel archs then all bets are off with the three piece set up.

SteveP

Spot-on Steve. IMHO, the brackets I have are better than the Moss ones and are certainly appear easier to instal. Another concern for anti-roll bars is also exhaust pipe and muffler locations, but that is another thread.

Marcello - I had anticipated you would have a CNC/laser so that is excellent news.

I also concur with Steve about your friend's glass fenders. Lotus (which used the TR6 front end vertical link in at least one model - Elan, I think) pioneered fibreglass monocoque bodies in the late 1950's. Creating suspension mounting points proved a bit of a nightmare, however Lotus proved that minimum weight combined with tortional rigidity was a formula which was hard to beat. Lotus still produces one of the best handling cars today. I have an in-car video of a 170hp converible Lotus beating a Porsche GT2 and keeping up with a Ferrari F50 over several laps on a racing circuit!!

Marcello - please don't talk about compensation - I'm only here for the love of the car and to share the passion. What goes around....etc..etc

Regards
Roger
Roger H

Roger,
All I can say is you sound like a good person. I will meet up with you one day and we will share a Fosters.

So to sum up:

A) Moss is readily available easy to install but not the best.

B)Revington sounds like a solid kit but not a charm to install.

C) The Roger version sounds just as solid but less head aches

D) No comment on the Herman van den Akker version. It remains to be the only one that is not attached to body.

There are still people out there that strongly feel that the chassis should take 100% of the load. Still concerns of cracking and folding of the wheel arches.

I will pass on the news to my fibre glass buddy, and I will ask him to check to see if it is glass outer and inner. If outer only he is good.
Marcello

OK, a few comments on the Herman van den Akker (et al ,as others offer similar setups) approach. It is not one that would care to use, but I am not adamant that people should stay away from it as it does not commit one of the cardinal sins.

It is far and away the easiest to install and does keep all suspension loads isolated in the unsprung weight to frame "box." On the other hand, it does restrict tire clearance on the back side, so going to larger tires must be given more thought. This is just a personal thing with me, but given the mechanics of deformable bodies approach, I do not care for the fact that the load path is quasi-cantilevered over that kind of span from the top damper mount back down to the lever shock mount location on the frame. Having said all of that, it is still a serviceable approach.

There is yet another approach out there and it falls in the "Just Say NO" category. That is the one where two plates sandwich the wheel arch and the damper top mount attaches to the plate in the wheel well. As previously pointed out in this thread, that sheet metal is not designed to take 100% of the loads of a damper mount (the cardinal sin alluded to above).
SteveP

Steve,
Roger states that his version (a very rare one, not to be seen in our world) does not take 100% of the load, if anything his guess at a minamal 5%.

??????

The inner wheel arch clearence issue is a new one to me. Now more to think of.

Roger, what do you think?

Does anyone out there have the Herman Van Den Akker version?
Marcello

Marcello,

I am working on a prototype like Herman's using 1.250 x .125 box tube and 3/8 plate at the base and shock mount.... folding the shock mount out of 3/16 would be ideal but I am having issues with my press. I have a CNC plasma unit and will MIG weld the assembly together. I may have this done in the next week or so and will send you a file when I get there.

Rob
Rob

Rob,
That would be kind of you. Let me know if there is anything I can do to help.
Marcello

Rob,
I was thinking.
Why use the press when you can tube bend it?
Do you have a tube bender? I have 2 if this could help.
Marcello

Hey Guys,
I have the one piece, mounted to the former lever shock mount points, tube shock conversion. It came with a KYB gas shock and all the bits and pieces. It is very sturdy. I think it came from Vicky Brit. I have no problem with tire clearence. I would recommend it highly. Later on I plan to switch out the shock to a more advanced adjustable one.
Steve
Steve Crosby

Hi Guys,

Marcello, I thought that CNC plasma cutting the top mounting plate to a simple profile then pressing to form a tapered U shape out of 8-10g plate would be fast and effective...the U would fit over top of the box tube and house the top of the shock at the other end. If you can bend 1.250 X .125 box tube to a 65 degree angle with legs of about 7.5" and 5" I think it will work... I intended to notch the tubing then weld it at 65 degrees in a jig.

The bottom mount could be improved over Herman's design by making a 1/4" back plate and a 1/8" front plate, welded and bolted through to effect a gusset which would re-inforce the lower leg reducing deflection, work hardening and cracking.

Steve, I would be grateful to have a second set of measurments to compare mine to. The angle and leg lengths would be most helpful.

As it turns out i will have the next few days free to work on this and other Tr related items so I might have a prototype before the weekend is out!

Cheers, Rob
Rob Gibbs

Hi guys,

I got one set done tonight! I fit it up with the Spax adjustable shocks and it looks good but I do not have the body on the car at this point and have just used measuments and a wire template from an original unmolested car to arrive at the point I am now at. I opted to use a section of 1.5" square box tube for the top mount... it caps over the upright leg and will be plenty strong for the job. I am going to test these on an intact car and if all is good, I will complete the reverse engineered welding jigs and be good to go... I hope. I will send pics and specs if I have an email address.

BTW, I think that the shock action is much more pronounced at the swing arm end, the stock mount position, and is therefore the ideal shock mount position... coilovers may look cool but they have much less travel and are thereby less effective.

Cheers, Rob
Rob Gibbs

Marcello,

The reason that the set up Roger descibes and the similar Moss set up does not transfer appreciable loads into the sheet metal is due to transfer of loads along the load path. The load path for the upper mount initiates where the damper is attached. That is a vertical compression load on the upper mount that is then translated into the intermediate mount located near the fuel tank by means of the bolts loaded in tension that connect the upper mount and the intermediate mount together, sandwiching the sheet metal of the inner wheel well. Nothing is perfectly rigid (the premise behind "DefBods") and there will be some insignificant shear loading into the sheet metal, but it can effectively be ignored in all but the most exacting calculations as the grip length of fasteners is rather short. All of this is working on the assumption that every was carefully fitted up and aligned when holes were being drilled and that fasteners are properly installed and torqued. Don't forget to use your Loc-Tite even with locking nuts. If the fasters between the mounts come loose, that is no good. Even more so at the top mount joint as then you will transfer shear loads into the sheet metal since the load path has been interupted at that point.

This load is then turned yet again to transfer from the intermediate bracket through the floor of the fuel tank area to the bottom mount on the underside of the vehicle. This bottom mount attaches to the intermediate, again by means of bolts loaded in tension, but since there is no turnng of the load path from the intermediate mount to the bottom mount any shear laoding into the sheet metal is even more insignifigant than it would be for the previously described joint.

The bottom mount in turn translates the laod into the frame through the original mount locations for the stock lever shocks. Here, you have a more complex load case for the fastener. The fasteners themselves are installed with a tensile preload, but the suspension load transfer is in single bolt shear at the mount/fastener joint. While I am a firm believer in keeping threads out of the grip length for fastener installations, it becomes critical when the fasteners are loaded in shear and even more so when that loading is single bolt shear. Bottom line, use good hardware with selectable grip lengths such as AN/MS hardware for these types of critical applications. I would also use AN/MS hardware for the mount joints too if it were me, but it is not as critical there as it is for the bottom mount to frame joint.

You may want to go to a library and see what they have in the way of engineering reference or text books and look at what they call Free Body Diagrams. It's one of the first things they pound into your brain as you start the Engineering Science and Mechanics portion of the curriculum with a class usually known as "Statics."

Robb,

There is no loss of suspension travel (unless of course one has fitted shorter springs) with the Revington set up. It is not so much the specific location of the damper as it is the valving, the viscosity of the internal fluid of the damper and the ability to dissipate any heat build up that will determine the efficacy of its function as it travels along its stroke.

SteveP

Steve,

It was not the suspension travel but rather the telescopic shock travel that I was refering to ... comparing the Remington (which i do like for sway bar mounting reasons) setup to a stock trailing arm mount position, I would expect a GIVEN shock to perform better at the stock position: it is forced to "work" that much more as it actuates on a larger radius at the stock position than at the spring pocket.
No, I am not an engineer so I may be talking out of turn here.... in which case I only ask for quiet and reservered snickering at my ignorance. :o)

Laughter to ALL, Rob
Rob Gibbs

Steve,
Simply. I will produce one type. and that one type will need to be suited to my TR and my buddy. His has fibre glass fenders. There fore I will need to lean to a system that has 0 body contact, even if min stress is applied the fastening issue for the fibre glass racer will be a concern. Do you agree?

Rob I am very interested in your results, I was hoping you could take records or templates as you went along. Do you feel you can translate proper numbers for a repro?

Roger,
How are your cads coming?
Marcello

Marcello - emailed Saturday afternoon (our time) and have not had it bounce back..??

I'll re-send now with a different subject line in case your sytem trashed it.

R
Roger H

This thread was discussed between 05/07/2006 and 18/07/2006

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