 | Home > Technical > Puma rear axle casing negative camber - factory tolerance? |
 
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| Shroppy Member Since: 25 Feb 2016 Location: Shropshire Posts: 866   
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I'm hoping someone may be able to offer a more learned opinion than my own on this please;
I have a 2011 short nose 110/130 axle casing that I'm in the process of trussing etc for my 127 build. The axle was purchased as a complete unit and then swiftly stripped and sent for blasting. I didn't note anything untoward during the disassembly and I very roughly checked it wasn't bent using two straight edges and a tape measure, the readings were within a few mm so I was happy. Fast forward to today and out of curiosity and a desire to cause frustration for myself I measured the casing again. As per the sketch;  Click image to enlarge Same methodology, two straight edges (only this time held more firmly) and a tape between them. There is no discernible toe in or out, there is however some negative camber as per the sketch, to the order of approx. 6mm over a distance of 400mm (measurements taken at 200mm offset from axle CL). Now, this is the plane in which you would expect the casing to bend if the vehicle were overloaded or landed badly but, there are no marks on the halfshafts, nor were they difficult to remove. Should I be concerned? I'm trying to balance my own perfectionism with the questionable LR build tolerances and am getting nowhere. In my infinite wisdom I've also pretty much completed my work on the axle (very confident I've not caused this 'bend') so I'm not particularly eager to undo it and straighten it! I'll do a dry assembly to check everything fits together ok tomorrow but would appreciate if someone could put my mind at ease this evening.... 1985 127 V8 Build Thread Series 2 109" Series 1 80" Last edited by Shroppy on 8th Jan 2021 7:41pm. Edited 1 time in total |
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8th Jan 2021 6:35pm |
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| Shroppy Member Since: 25 Feb 2016 Location: Shropshire Posts: 866
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Pondering some more... I've calculated it to be 0.859° or approx 51' of negative camber assuming both flanges are skewed, worst case one wheel has 1.718° or 1° 43' of negative camber.
UPDATE - according to the extract Dinnu kindly shared, it seems these values aren't as far out as I feared. 1985 127 V8 Build Thread Series 2 109" Series 1 80" Last edited by Shroppy on 12th Jan 2021 1:31pm. Edited 1 time in total |
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8th Jan 2021 7:12pm |
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| Shroppy Member Since: 25 Feb 2016 Location: Shropshire Posts: 866
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Good point, I believe he did yes! The other option I'm considering is heating then quenching the underside of the casing to draw it back straight. 1985 127 V8 Build Thread
Series 2 109" Series 1 80" |
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8th Jan 2021 7:44pm |
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| DSC-off Member Since: 16 Oct 2014 Location: North East Posts: 1440 
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If the angles of the end flanges are causing concern, a friendly engineering machine shop could easily skim the minimum amount off each end face to true it up. Both ends should ideally be machined in one set up to ensure they are parallel.
This would be my preferred solution, rather than putting thermal or mechanical stress into the case to straighten it. Further load or heat in the future could cause it to bend again, possibly in an unpredictable way. |
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11th Jan 2021 7:39pm |
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| Shroppy Member Since: 25 Feb 2016 Location: Shropshire Posts: 866
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A good point re machining the faces, my concern with that would be that the halfshaft may foul the stub axle.
Following a conversation with Nige, and some more measuring I think I have determined the following; - My initial measurements were probably pretty accurate. - The trussing of the casing is likely to have cause a bit more of a bend despite my best efforts to keep the heat down. So my next steps are as follows; - Verify the long side is indeed the issue by installing the diff and halfshafts as a sort of crude centreline. - Cut through the truss above the point of max bending moment (adjacent to pumpkin). - Lay a bead or two of weld to 'pull' the casing back square, taking care not to pull it too far. - Carefully weld up the truss. 1985 127 V8 Build Thread Series 2 109" Series 1 80" |
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11th Jan 2021 9:02pm |
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| DSC-off Member Since: 16 Oct 2014 Location: North East Posts: 1440
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I've just seen the truss pictures in your build thread. -nice work!
Yes, that will explain why it's bent. The majority of the weld is next to the diff, so where most of the distortion will be. Sounds like you have the right plan to fix it. |
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11th Jan 2021 10:20pm |
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| Supacat Member Since: 16 Oct 2012 Location: West Yorkshire Posts: 11018 
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Out of curiousity, why didn't you use the centreline as your datum?
You could have picked a point either side of the diff and isolated each flange, and if you wanted to top and bottom separately? The two distances you have measured could be the same but the flanges might not be square to the centreline. |
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12th Jan 2021 7:21am |
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| Shroppy Member Since: 25 Feb 2016 Location: Shropshire Posts: 866
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Good question, at the time I didn't have the diff and halfshafts handy to form a centreline, and given the construction of the casing didn't fancy picking a point to measure from other than the mating flanges. That said I could have used the diff mating face I suppose.....
Unless I'm misinterpreting your point? 1985 127 V8 Build Thread Series 2 109" Series 1 80" |
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12th Jan 2021 11:55am |
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| Supacat Member Since: 16 Oct 2012 Location: West Yorkshire Posts: 11018
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I'm probably over complicating it ~ but your query is a good one to mull over.
Other thought was to stand axle on end and drop plumblines through the boltholes and see the variance as you go around. |
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12th Jan 2021 12:39pm |
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| Dinnu Member Since: 24 Dec 2019 Location: Lija Posts: 3469  
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Found this table on a manual.
I think the ' symbol means minutes, which is a fraction of a degree. I know that there are 60 minutes in 1 degree (same as time), so that means the tolerance would be 1/6 of a degree, or 0.1667 degrees. I cannot guarantee if I am correct though. Click image to enlarge 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing 2012 90 CSW, 2.2TDCI, Santorini Black |
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12th Jan 2021 1:14pm |
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| Dinnu Member Since: 24 Dec 2019 Location: Lija Posts: 3469
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Sorry.. I missed the +/-45', so the tolerance is actually 55'
That is almost 1 degree, or to be exact 0.9167 degrees. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing 2012 90 CSW, 2.2TDCI, Santorini Black |
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12th Jan 2021 1:16pm |
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| Shroppy Member Since: 25 Feb 2016 Location: Shropshire Posts: 866
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A good point re plumb lines through the bolt holes, this is how the axle currently looks in the workshop sat on a perfectly horizontal surface;
Click image to enlarge I struggled to determine the side at fault with the plumb line, after about 30mins of looking from all sorts of different angles and flipping the axle over I'm reasonably confident the long side is the issue, hopefully bolting the diff in later will verify this. Dinnu, thank you, that is a very interesting extract. There is an understandable preference for negative camber in those values and it certainly confirms that the flanges may not have been parallel from the factory! I'm going to proceed with attempting to straighten it out as my OCD won't let me leave it alone, those values will be a big help. 1985 127 V8 Build Thread
Series 2 109" Series 1 80" |
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12th Jan 2021 1:19pm |
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| Dinnu Member Since: 24 Dec 2019 Location: Lija Posts: 3469
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I was looking for those values for myself too, as had a concern over front axle camber, especially because of the many reports (and JLR recalls, mine was not recalled) of swivel housing flange parting the rest of the axle.
I have not yet measured mine, but found that a bad toe in made it look very bad when I reverse it into my garage. pheww. 1988 90 Hard Top, 19J Diesel Turbo, Shire Blue - Restoration ongoing 2012 90 CSW, 2.2TDCI, Santorini Black |
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12th Jan 2021 1:32pm |
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| blackwolf Member Since: 03 Nov 2009 Location: South West England Posts: 17544 
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You are correct, 1 minute is 1/60th of a degree (and actually 1 second is 1/60th of a minute, so 1/3600th of a degree if you need that level of accuracy). The spec for camber is therefore -10' +/-45', so anywhere in the range from -55' to +35'. It is on the face of it a bizarre specification, proportionally the same as defining a linear measurement to be 1/4 of an inch, plus or minus 1 inch. |
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12th Jan 2021 6:09pm |
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