Disappointed in parts quality

[lowact]

Thx Andrew and Steve. I’m not sure if:
You are believing that the new mounts that SNGB (and everybody else) sell are accurate reproductions of the original Jaguar product and that the difficulty of fitting them is just one of those things and that once fitted there will be no detrimental consequences.
Or alternatively, you are saying that whether or not these new mounts are accurate reproductions and the difficulty of fitting them is due to this inaccuracy is irrelevant because they are all we’ve got, so just do whatever is necessary to make them fit, to hell with the consequences?

Hammering in a 5/16 UNF, how is that acceptable practice? How do you think Jaguar did it?

Have you considered that, if new IRS mounts were the same dimensions as Bill’s NOS (new, old stock, authentic original Jaguar) there would be no hammering or distorting required, that IRS installation could be exactly and as simply as the procedure in workshop manuals, no special tools?

Now the 6 million dollar question: what do you imagine SNGB’s insurers would have to say if they found out that SNGB were knowingly selling versions of manufacturer's designated safety items that were non-compliant leading to increased risk of failure? I’d guess the same as your insurers …

[mgcjag]

Hi Colin...this is my take on it.....we have a choice....we can use the best parts that are currently available and do what's required to make them work....or we can make or have made our own parts..or you can pursue a supplier to change the design of their existing parts....in a post above Julian has said that these particular parts will not be re engineered......over the last 10 or so years iv fitted about 8 irs.s with new mounts...most have gone in quite easily with just the use of a podger to line up the holes..a few needed a bit more effort...iv never needed to use a tool like Rory shows above..and I would never even consider hammering in a bolt....as iv said previously you can spend a lot of time thinking about how difficult a job on an E type is going to be...but once you get starrted it's normal not that difficult....Steve

[Fuel.inj]

I think you have summed up the comments very well Steve. We are very fortunate to have a supplier such as SNGB who do take note of customers feedback and stock enormous amount of parts for our beloved E-Types.

[angelw]

Steve Wrote:

we have a choice....we can use the best parts that are currently available and do what's required to make them work....or we can make or have made our own parts..or you can pursue a supplier to change the design of their existing parts....in a post above Julian has said that these particular parts will not be re engineered

Hello Steve,
Its been mentioned in many Threads relating to parts quality, that Jaguar enthusiasts are lucky to have suppliers of parts for their cars, conversely, these businesses are fortunate that there are enthusiasts wanting parts. Although the owners have a passion for the marque, it's a business and if the parts weren't selling, you can bet your bottom dollar that the supply would halt.

What confounds me, is why the After Market parts aren't simply made to the same specifications as the original parts. There is no design requirement, all that development has been completed decades ago, only the capability to measure and copy existing parts that worked in the past is required.

Early in this Tread, I showed an accurate measurement comparison between an original NOS, rear cradle mounting bracket and an After Market part. Because of the angular interface between the Chassis Legs and the IRS cradle, any difference in the separation of the mounting holes in the bracket caused by the height of the rubber is going to have an effect on the alignment of the holes in the bracket and those in the cassis legs and IRS cradle; that is confirmed by simple trigonometry. This forces the rubber to be distorted to allow attachment to be made and will lead, without doubt, to premature failures when force is applied to a part that is already under load that is not a design feature. I suspect that the design of this bracket was to have infinitesimal, or no load when initially assembled and a load catered for in the design when the car is sitting on its wheels.

Another part that pops up regularly on various Forums, with complaints relating to dimensions, is the standard ball joint system for the upper wishbone. The Ball Pin and Cup are among the easiest parts one would get to make on a CNC Turning Centre, with cutting tool wear being very predictable and to get either of these parts wrong, the manufacturer either has no QC, or just doesn't have a clue.

The following picture is of axles I manufacture for another company. I've made thousands of these parts with not one, not even the first off the machine years ago, being out of the specified tolerance of the drawing. Like the Ball Pin and Cup, tool wear is very predictable, and QC is conducted by the operator, who, rather than lean up against the machine picking his nose while the next part is being machined, is measuring the part just completed and making digital Offset adjustment as the measurement of critical diameters approaches either limit of the tolerance range.

This axle is a much more difficult part to machine than a Ball Pin or Cup, as there is severe interrupted cut to deal with during the early stages of roughing. With the Ball Pin and Cup, the two components would be machined from round bar with a diameter close to the large diameter of the parts.





Regards,

Bill

[Phil P]

Thank you Bill.
That's the best explanation as to why the parts we buy should fit and work properly. Proof that properly understood and controlled processes will yield the right results without extra cost.
Yours,
Phil

[lowact]

I asked JLR about the original design, they provided the following drawing extract:

JLR could read that it was last updated in 1974, they don’t know what this change was. However I note that the drawing uses the std method of notating changes and that there is no notation on the critical 2-5/8” dimension that is from the base of the mount to the centre of the frame fixing holes. This suggests that this dimension has always been 2-5/8” (66.7 mm).
There is no tolerance shown. QA might allow what would round to 2-5/8”, i.e. 2-9/16” > 2-11/16” (65 > 68 mm). Means, even with the most generous tolerance allowance, SNGB’s offerings (>69 mm) are not in accordance with Jaguar’s retained specification.