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Is it true Ford of England refused an air ministry request to build Rolls Royce Merlin engines under license because the tolerances Rolls Royce allowed were looser than Ford was willing to work with?NOT EXACTLYI have worked in engine overhaul shops and overhauled engines since the 1970s.It seems the original RR Merlins were balanced and blueprinted type engines. I have worked on factory Jaguar engines which had multiple different fit pistons in cylinders that were all standard bore. They were not interchangeable. I have balanced and blueprinted engines fitting parts to the minimum clearance. Pistons were knurled for the best fit to a particular cylinder. They were not interchangeable. Rod and main bearings fit to between .0005- .001 inch clearance. Such was the case with original RR Merlins. The precise machining of parts eliminates the need for gaskets or makes gaskets very thin sometimes just a piece of silk thread or paper.Standard assembly for mass production requires looser tolerances for assembly. Any piston goes in any hole. Bearing clearances become .001-.003 inches so they all work no special fitting to tighter tolerances. Crankshafts are then ground to a size that allows this. Instead of tighter tolerances there are actually looser tolerances for assembly but tighter tolerances for acceptance of parts which allows bigger clearances. These tighter tolerance for acceptance are to make parts more interchangeable by making them a looser fit. Gaskets become more common and thicker so less precise machining is required to prevent oil leaks. Thicker Paper and Cork gaskets become common.So yes they had to re design the specs to tighter tolerances. Instead of having a crank journal that could measure as example 2.1245–2.1285 +-0.0005. Mechanic assembles to 0.0005–0.001 clearance for bearing.They tightened up the specs to 2.126–2.128 inches +-0.001 now everything is interchangeable and can be assembled by anybody. Assemblyman assembles to 0.0005–0.0035 clearance for bearing. No fitting allowed.We lose a bit of power, smoothness and life. However we can now crank out way more engines with unskilled labor.It would be interesting if somebody had the original specs from RR and the revised specs for the other companies so they could be compared.There is your answer Charlie.

The first precaution that you must undertake is the careful visual examination of the parts that are to be mated to one another to ensure that any fit profiles/splines etc. are indeed compatible. Also, even if you are re-assembling original components it is advisable to take and record accurate measurements of the inside dimension of the fit within the coupling, and the outside dimension of the fit area on the shaft, in order to either assess the magnitude of the reassembly task at hand or to eliminate the possibility of any mismatch of, or manufacturing error with respect to the parts with which you have been provided. These measurements can be readily determined with a simple Vernier caliper, most if not all of which make provisions for taking accurate, repeatable inside and outside dimensions with accuracy well within plus or minus .0005 inch (*five, ten thousandths of an inch) graduated in Standard units, or .01 millimeter (*one one hundredth of a millimeter) for metric measuring tools. Familiarizing oneself with the use of a Vernier should not present a challenge to anybody who is also undertaking the disassembly/reassembly of the steering system on their vehicle. (In the event that I am wrong here on this point, it should justify a reality check as to whether to proceed at all, or to delegate this project to the professionals.) .Mistakes and mixups do happen - and if you have parts in your hand whereby an excessive interference fit will result if attempts are made to assemble (shaft too large/coupling bore too small) it is a virtual certainty that no amount of force will be sufficient to assemble the parts by any means, that doesn’t result in the effective destruction of both in what for you and your DIY maintenance project will amount to a quantum leap backwards. Any incompatibility issues must be resolved in order for you to move forward.In situations where automotive parts that are likely to be assembled and disassembled to remove from the car during the life of the vehicle, authentic “interference fits” (in which examples the male part is actually larger than the female at similar temperatures) are rare in my experience, presumably because they become virtually impossible to disassemble without having to cut them out with an acetylene torch. It is likely therefore that the fit between your steering shaft(s) and universal joints are more along the lines of “tap” or “sliding” fits, whereby - given perfect cleanliness and alignment (after eliminating the aforementioned possibility of a misfit somehow) - and light lubrication of the interface between the parts with Never-Seize or automotive grease, and after careful alignment and indexing of any spline or “D-shaped” profiles, can be assembled to one another by light taps with a hammer - by way of a hardwood or high density plastic drift.If you dimensional checks do reveal a closer fit than might be easily assembled with parts at similar temperatures, assembly can be eased somewhat by manipulating the temperarture of the parts somehow to exaggerate the clearance that exists at the moment of assembly. If practical to achieve, the female coupling can be warmed in the oven on a cookie sheet just prior to assembly, and/or the shaft placed in the freezer. Have your Vernier close by for comparative measurements just before assembling. If you are able to create another .001 inch or so of clearance (.025 mm) you will greatly ease the process of assembly. However, and to reiterate, if you are dealing with engaging splined components (typically the case with steering input linkages) it is not typical that one would need to resort to such measures in the routine process of assembly/disassembly. These are normally assembled and disassembled using hand tools, with all parts at ambient temperature.As well as cleaning, inspection, lubrication and alignment of parts in preparation for assembling, ensure also that any setscrews provided in the design - quite commonly used in splined steering shaft and coupling applications - are first removed, then reinstalled and tightened firmly once assembly is complete.

I'm not sure what you mean by normalizing. If you assume that by normalization you mean standardizing, ie transforming into a z-score with mean 0 and standard deviation 1, then this is a generally good practice for several reasons:(1) In theory regression or other statistical techniques are scale free. That is, if you multiply your 3rd explanatory variable by 1000 and rerun your regression then your new beta 3 should be 1000 times smaller than the old beta 3. Unfortunately, your computer works on doubles which do not have infinite precision. The condition number of your design matrix is a bound on the numerical error, and the condition number of your matrix is greater than the ratio of the maximum column or row norm divided by the minimum column or row norm. Put another way -- if you multiply your 3rd column / explanatory variable by 1000, you increased the condition number by sqrt 1000.(2) While plain old regression is scale free, regularized regression isn't at all.(3) When reporting coefficients in an explanatory study, I prefer to see standardized scores because, well, it's not that interesting if my largest beta is 1000 if that explanatory variable only ranges from .0001 to .0005.(4) (related to 3) Putting things on the same scale just makes them more comparable.