Bent adjustable reaction plate

[288gto]

Lets hope the manufacturer has a satisfactory answer.......... To me the basic design is flawed as mentioned above, the 5/16 bolt is taking the strain that should be carried by the Reaction plate which appears not upto the job.

Which is not helped I suspect Andrew by the large, presumably "lightening", hole in the reaction plate near to where the load is being transferred.

[PeterCrespin]

Lets hope the manufacturer has a satisfactory answer.......... To me the basic design is flawed as mentioned above, the 5/16 bolt is taking the strain that should be carried by the Reaction plate which appears not upto the job.

Which is not helped I suspect Andrew by the large, presumably "lightening", hole in the reaction plate near to where the load is being transferred.

I think we're getting bit ahead of ourselves, chaps. We’re abandoning logic here in and it doesn’t do Keith any favours to reflexively circle wagons and take pot shots at vendors.

It can, and does, often require mountains of data to prove something conclusively, whereas a single confirmed observation can cause even the most persuasive theory to come crashing down, which is what seems to be the case here, herd mentality notwithstanding.

A few years ago I had the pleasure of spending time with Jason Len, hardcore motorcyclist and founder of XKs. I drooled all over his Lightweight racer that was in the shop and used many/most of XK’s performance goodies, including the adjustable reaction plate.

As anyone who has raced learns on Day One, the loads imposed on a car during hard track running far outweigh those encountered during street driving. This would be true using identical cars, but applies much more when the track car is far quicker and has massive sticky tyres, hard suspension and someone quick behind the wheel. Any suspension component that failed due to bad design after only 200 miles of road use would fail far more quickly on track. Meanwhile, one would expect that an inherently badly-designed component which failed at 200 miles might occasionally fail at lower mileages, sometimes at similar mileage and more often after greater mileages of, say, 1,000 miles or more. Such a situation would not escape the notice of the maker and/or seller.

I have no dog in this fight and have fitted a Rob Beere plate to the D, since it is obvious in advance that Jaguar’s E-type settings will not apply to an aluminium car and probably several adjustments will be needed once I install the engine. But logic is logic and statements that a design is flawed, even written in bold type, do not make sense at this stage, or possibly ever. I do accept that theoretically one design may perform as well as any other once fitted, but may encounter a higher failure rate in practice, due to a greater likelihood of incorrect fitting. Which is not to say that’s what has happened here, yet.

I haven’t seen the XK instructions (perhaps Keith can show them here?) but I imagine that the threaded adjusters are used to vary the position of the bars at full droop, before the torsion bar brackets are secured tightly by 3/8 bolts in shear, as per normal. It looks to me self-evident that the adjusters have been subjected to compression/bending loads far in excess of what they were designed for, and as the pressure point is well ‘outboard’ the plane of the reaction plate, this has resulted in a twisting/bending moment the components were never designed to sustain. The most obvious cause for that would be improper assembly/tightening of the various parts, so that forces intended for the plate are borne by the adjusters.

The Beere reaction plate cannot generate such loads because the TB brackets operate in almost pure shear at the face of the plate, as per the standard parts which also pass through the frame ears. The Beere plate needs a big Allen key and is perhaps easier to set unevenly side-to-side because it can be hard to count the flats at the low end of the range. But even if things aren’t tightened fully, or washers are omitted etc., there is unlikely to be much harm done because there remains little possibility of inducing bending or distorting forces. A badly-installed Beere version might therefore survive abuse longer than a badly-installed XKs version, perhaps with some washers or spacers transposed, yet both types perform equally well once correctly fitted.

I’m no engineer, but critical thinking and basic logic are no respecters of tertiary education. The flawed design hypothesis seems not to survive the real world failure rate test - this being the first we've heard of it - which leaves only the following:

A: Sound design, poor quality execution (incorrect material batch? Poor process control?)

B: Sound design, poor application (assembly issues, car structure issues?)

C: Sound design, good QC and application, but extreme environment (rallycross, bus jumping? )

If option B were more common than with other designs, it could be regarded as a ‘flaw’, but that would be like damning all Series 1 cooling systems or con-rod split pins, even though the problems occur from misuse years later. The scenarios I can imagine are that the adjusters were overloaded by forcing the TBs under load rather than full droop, or at nearly full droop but still with dampers connected, or that the TB brackets were not secured fully once positioned correctly by the adjusters, or a combination of both. The f
first two hopefully unlikely, since if they were enough to bend the adjusters it would happen as they were being extended and would be obvious to Keith as he worked.

The strange angles and odd gaps are probably as much the result of the damage rather than cause, although threads don't usually undo under load, things just strip or snap. Not actually having seen the instructions also means we can't be sure. But my suspicion is that things went pear-shaped when the brackets pressed against the adjuster in use, instead of being tight on the reaction plate and loading that up instead. We know the bracket can sustain race-level heavy loads in the intended plane, but were have no comparator for lateral bending loads.

[288gto]

Lets hope the manufacturer has a satisfactory answer.......... To me the basic design is flawed as mentioned above, the 5/16 bolt is taking the strain that should be carried by the Reaction plate which appears not upto the job.

Which is not helped I suspect Andrew by the large, presumably "lightening", hole in the reaction plate near to where the load is being transferred.

I think we're getting bit ahead of ourselves, chaps. ..........

I haven’t seen the XK instructions (perhaps Keith can show them here?) but I imagine that the threaded adjusters are used to vary the position of the bars at full droop, before the torsion bar brackets are secured tightly by 3/8 bolts in shear, as per normal. It looks to me self-evident that the adjusters have been subjected to compression/bending loads far in excess of what they were designed for........

Hi Peter, my comment regarding the design being "flawed" is in relation to what appears to have happened to Keith's reaction plate. In the event of the two bolts that clamp the torsion bar "teardrop" brackets via slots in the reaction plate working loose or not clamping adequately the full load is taken by the adjuster resulting in the failure and damage seen in Keith's pictures. I personally see this as a "flaw" in the design. This would not happen on the Rob Beere reaction plate.

Just for clarity, I've bought a lot of high quality items from XKs and would certainly recommend them.

I'm also happy to accept an alternative word to "flawed" that describes the above scenario that I can go back and edit in

Instructions below that do point out the adjusters are not designed to accept the weight of the car (design flaw or otherwise.)

This would suggest that the design relies on bolts in slots to carry the weight of the car and loads from the torsion bars. Like you Peter I admit I'm no engineer, perhaps an engineer on here could comment whether bolts and slots are a good design for this application?

[mgcjag]

Hi Simon....do you have the fitting instructions as well as the warnings you posted....Steve

[288gto]

Hi Simon....do you have the fitting instructions as well as the warnings you posted....Steve

Hi Steve, as instructions go, they are pretty good and go into detail about shims, fitment issues and ensuring bolts are tight.

https://xks.com/pdf/311276

Simon

[mgcjag]

Thanks Simon....Well in my opinion the instructions are very poor.....I dont think the parts are identified very clearly and i dont really understand how you actuall adjust the height by supporting the wheel.....also to just say tighten the bolts leaves a bit to be desired....it should at least give a torque figure.....They obviously realise that if the nuts/bolts are not tightened correctly then the adjusting mechanism will be damaged by the weight of the car so they should have ensured this was not possible.....Steve

[PeterCrespin]

"Hi Peter, my comment regarding the design being "flawed" is in relation to what appears to have happened to Keith's reaction plate. In the event of the two bolts that clamp the torsion bar "teardrop" brackets via slots in the reaction plate working loose or not clamping adequately the full load is taken by the adjuster resulting in the failure and damage seen in Keith's pictures. I personally see this as a "flaw" in the design. This would not happen on the Rob Beere reaction plate."

It's partly semantics I guess, with a bit of philosophy thrown in. E.g. You could argue that the most dangerously-'flawed' and hazardous E-type design feature is the clamp bolt on the lower column, because it's often butchered, replaced with a non-spec fastener and incorrectly fitted. Many steering racks are dangerously mounted too. In both cases Jag provided fail-safes to protect us from ourselves, but sometimes you can never do enough to cover every eventuality. Is a failure to provide double-level customer-proofing a flaw? Depends on your point of view. I would posit that nothing 'happened' to Keith's reaction plate, in the sense of an accident, rather, something was 'done' to it. It's the same as the cam cover threads - people crack cam covers. I've done it. I don't blame Jag.

Jaguar even went the reverse direction when they switched from a bottom yoke integral with the steering column to a separate replaceable UJ that someone somewhere has undoubtedly screwed up (i.e. failed to screw up properly) putting themselves and the rest of us at mortal risk. Was that a design flaw?
I took your comment about holes the same way. If you believe that it's a weakness then the race cars prove it isn't - in anything resembling normal or heavy-duty use - if fitted properly. To argue otherwise is to say a two-shilling piece was flawed because it could not withstand the passage of an 0-6-0 shunting engine without deforming to the size of a half crown when placed on the track by naughty schoolboys like me in 1966. The coins were actually fine for their intended use in every respect.

"I'm also happy to accept an alternative word to "flawed" that describes the above scenario that I can go back and edit in

Perhaps 'sub-optimal' would do, in the sense of 'less than totally foolproof'. But like teaching your kids to ride a bicycle, at some point you have to let go of the saddle and risk a crash.

"Instructions below that do point out the adjusters are not designed to accept the weight of the car (design flaw or otherwise.)

Well, I would say it's nice to be vindicated by the instructions, except that I can hardly take credit for them stating the bleedin' obvious. There's absolutely nothing I wrote that couldn't have been figured out with a cup of coffee and a handful of functioning cortical neurones. I just posted before others. You could say there was a bit of 'groupthink' developing, so I opened the window for some fresh air.

"This would suggest that the design relies on bolts in slots to carry the weight of the car and loads from the torsion bars. Like you Peter I admit I'm no engineer, perhaps an engineer on here could comment whether bolts and slots are a good design? "

If you want adjustability, slotted holes are an option, like the S1 column rake adjustment that lots of owners don't even know they have. You'd just better make sure the fasteners are tight if you want to avoid surprises. You could make alternator belt adjustment secure by using shims, but slotted brackets are OK if you assemble the pivot correctly instead of snapping the ears off, and you do the slot fastener up tight.

[288gto]

Thanks Simon....Well in my opinion the instructions are very poor.....

After my reprimand from Peter I was being careful with my words
In fairness compared to some or even non existent instructions I’ve had from suppliers they do at least go into some detail.

Peter ( see his above post) has now cleared the use of “sub-optimal” so I’m happy to go with that.

Simon

[288gto]

Perhaps 'sub-optimal' would do

If you want adjustability, slotted holes are an option, like the S1 column rake adjustment that lots of owners don't even know they have. You'd just better make sure the fasteners are tight if you want to avoid surprises. You could make alternator belt adjustment secure by using shims, but slotted brackets are OK if you assemble the pivot correctly instead of snapping the ears off, and you do the slot fastener up tight.

I would hazard a guess that those components aren’t subject to the same high and continued forces the torsion bars exert on the brackets.

What regression to childhood antics of placing coins on railway tracks has to do with all this , I’m not entirely sure Peter

Poor Keith must be thinking what have I unleashed, I only posted a few pics.

I hope you get it sorted Keith.

ATB

“Sub-optimal” Simon

[keithmac]

Thanks for the illuminating inputs.
No sign of ANY instructions with my RP . Nada, nothing , not a single piece of paper. It was , however, installed EXACTLY , as I now see, they show, right down to every nut , bolt and washer.I also see now that at the very bottom of the web page there is a link for instructions. So in the future , dont order by phone ! My clamping bolts were tight.
It is now apparent that the adjuster took too much load , bending the RP. the question is why ?
Have a look at the pics. The outward tilt of the torsion bars when the suspension is on full droop pulls the silver " ears " away from the RP. Hammering did not move it one iota closer. As you can see the spacer does not make up for this in this position. So a lot of the clamping force of the two retaining bolts goes into closing this gap. Tight on the bolts is not good enough.
Bottom line is operator error. The bolts need to be CRAZY tight . Which they now are. We will see if this situation repeats in the coming month , one the snow melts here.
I must say , the European version of the adjustable RP looks a more , shall we say , fool proof design.
Cheers all
and happy motoring

[mgcjag]

Hi Keith.....from your photos you have the torsion bars already slotted into their splined sockets....the instructions as follows say to fit and tighted reaction plate then install the torsion bars....with your TB,s still connected at the front wishbones i can imagin how they are pulling the sockets out of square....when installing did you have your front wishbone balljoints seperated and the shock absorber disconnected......or was your suspension fully connected but just on full drop
5. Install the Torsion Bar Sockets in the middle of their travel. Tighten down the Torsion Bar Sockets
6. Tighten the set screws against the adjuster socket and the jam nut against the adjuster nut.
7. Re-install the torsion bars per the manufacture’s instructions.

[288gto]

Hi Keith.........the instructions.....

5. Install the Torsion Bar Sockets in the middle of their travel. Tighten down the Torsion Bar Sockets
6. Tighten the set screws against the adjuster socket and the jam nut against the adjuster nut.
7. Re-install the torsion bars per the manufacture’s instructions.

If I'm reading the above correctly this would mean removing the torsion bars each time you want to adjust the ride height to avoid overloading the adjusters? If that is the case you might as well stick with the original Jaguar set up.

Simon

[mgcjag]

Hi Simon..The instructions above are for installing the RP....the adjustment instructions are below...but they dont make sense to me..I dont understand how you can "support the wheel to relieve the pressure"....?

[288gto]

That's what I couldn't understand too Steve. By fitting a cam disc like the Rob Beere one instead of the threaded adjuster it probably wouldn't take much to convert what Keith has. Obviously put it on the other side so the torsion bar bracket is acting directly on it. You could still use all the other parts. Just a thought.

Simon