TRUNNION WEAR PLAY

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TRUNNION WEAR PLAY

Post by Dennis Nicholas » Mon May 27, 2019 4:04 pm

Just hoping to perhaps clarify and get a consensus on acceptable amount of play between trunnion and vertical link. To experienced/professional engineers it is probably fairly easy to decide what is and what is not acceptable play in mechanical moving joints and for non experienced it is often quite obvious when wear is excessive......measurement is perhaps a good way of determining a boundary between ok and reject? (just as in workshop specified end-float tolerances for example). I think I am right in saying the trunnion and vertical link threads are ACME...ie they are squarish threads rather than sharp peaked as in UNF, METRIC, WHITWORTH, etc.(so if your threads have sharp peaks then definite reject)

Using the set up in the picture I have taken measurements of play of various combinations of trunnion and vertical link.
Link/calliper mounting plate held firmly in vice and DTI magnetically sat on calliper mounting plate.
Trunion fully wound on then backed off to working position.
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Dennis
Last edited by Dennis Nicholas on Mon May 27, 2019 5:53 pm, edited 1 time in total.


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TRUNNION WEAR PLAY

Post by Dennis Nicholas » Mon May 27, 2019 4:10 pm

below the picture I set out the info in 3 columns with spacing between headings - Trunnion, vertical link and movement with corresponding info under each heading but the preview and post have removed the spacing between columns and I can't get it to columnise......why??
First line would read new under trunnion, new under vertical link and 0.001 under movement


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Post by JoeySully » Mon May 27, 2019 4:39 pm

I'm also interested...
post #2 here https://www.triumphexp.com/forum/spitfi ... y.1340614/

says ...
I rocked the trunion back and forth gently on the threaded part of the spindle to see what the play was - with the dial indicator on the edge of the trunion. The specs were in the service manual, .002 - .006.



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Post by Old and Slow » Mon May 27, 2019 5:15 pm

Dennis,
That is very useful info, thanks for posting it.
Perhaps tabulating the data in Word or similar and pasting it like a picture would make it clearer.


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Post by Dennis Nicholas » Mon May 27, 2019 5:21 pm

Old and Slow wrote:
Mon May 27, 2019 5:15 pm
Dennis,
That is very useful info, thanks for posting it.
Perhaps tabulating the data in Word or similar and pasting it like a picture would make it clearer.
I thought it came out ok columnised the first time I did it and looked at a preview but went off to do something before finishing and posting and when I came back I had been logged out or something and when I logged back in "poof" my post had ALL vanished....choice words uttered!!!!


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Post by David Tew » Mon May 27, 2019 5:22 pm

Dennis Nicholas wrote:
Mon May 27, 2019 4:10 pm
preview and post have removed the spacing between columns and I can't get it to columnise
A peculiarity of the forum software.You can do it with BB Codes but it's often easier to insert a JPG. :wink:
Is this what you were after?:
Trunnion play.JPG
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Post by scimjim » Mon May 27, 2019 5:38 pm

The other way to tabulate is to use dots - although the page will resize to different screen sizes, so what works on your desktop may look awful on a phone screen.


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Post by Dennis Nicholas » Mon May 27, 2019 5:58 pm

David Tew wrote:
Mon May 27, 2019 5:22 pm
Dennis Nicholas wrote:
Mon May 27, 2019 4:10 pm
preview and post have removed the spacing between columns and I can't get it to columnise
A peculiarity of the forum software.You can do it with BB Codes but it's often easier to insert a JPG. :wink:
Is this what you were after?:
Trunnion play.JPG
That is exactly what it should look like. Is there any way to edit my post and make it look like that??

Regret I have no idea what BB code is or how to use :(

Dennis


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Post by David Tew » Mon May 27, 2019 6:06 pm

Dennis Nicholas wrote:
Mon May 27, 2019 5:58 pm
David Tew wrote:
Mon May 27, 2019 5:22 pm
Dennis Nicholas wrote:
Mon May 27, 2019 4:10 pm
preview and post have removed the spacing between columns and I can't get it to columnise
A peculiarity of the forum software.You can do it with BB Codes but it's often easier to insert a JPG. :wink:
Is this what you were after?:
Trunnion play.JPG
That is exactly what it should look like. Is there any way to edit my post and make it look like that??

Regret I have no idea what BB code is or how to use :(

Dennis
Hi Dennis,

The easiest way is to cut the JPG from my post and insert it in your original. I will send you the file in any case.

:D


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Post by scimjim » Mon May 27, 2019 6:10 pm

I’ve done it for you Dennis.


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Post by Dennis Nicholas » Mon May 27, 2019 6:39 pm

THANKS Jim.


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Post by JoeySully » Tue May 28, 2019 12:27 pm

I wonder if the measurement you took really matter when the upright will be secured at the top by a balljoint so the movement you are measuring will not be there at all when in use. If you grabbed hold of the upright when attached and pulled it in and out the movement would be much less.

Should the real play\endfloat be measured vertically on the threads? i.e. the distance the trunnion moves up and down on the upright threads. ?



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Post by Old and Slow » Tue May 28, 2019 1:21 pm

During the MOT my man uses a long bar to lever somewhere around the upper ball joint and the wishbones to take the weight off the trunnion, so he can feel the play. (At least I think that's where he stuck it, wasn't watching too closely). Anyway, he found "almost excessive" play in the lower spigots, which being TR4 trunnions are only lightly torqued in, with castellated nuts.
For me, just a matter of tightening up the nuts either end of the spigot.
I hope this helps explain - I think different MOT men will check different things, but worn trunnions are a well-known area for potential failures (on the road) so my man checks these carefully for me.
Next time I strip the trunnions I'll get the DTI out and do some measurements; thanks for the suggested approach Dennis.


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Post by Dennis Nicholas » Thu May 30, 2019 9:49 pm

JoeySully wrote:
Tue May 28, 2019 12:27 pm
I wonder if the measurement you took really matter when the upright will be secured at the top by a balljoint so the movement you are measuring will not be there at all when in use. If you grabbed hold of the upright when attached and pulled it in and out the movement would be much less.

Should the real play\endfloat be measured vertically on the threads? i.e. the distance the trunnion moves up and down on the upright threads. ?
More measuring then. The movement of the trunnion along the vertical link length: (this is the up and down wear movement the ends of the lower wishbones will experiance
NEW NEW 0.0005 TO 0.001 INCH
NEW OLD 0.002
OLD OLD 0.006 AND FEELS LOOSE.

There if anyone can add those figures and explanation to the table......I tried and failed :(


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Post by Steve_S » Fri May 31, 2019 7:11 am

I take it you know theirs a thing called "Tolerancing of Screw Threads"
So all threads will have a built in play.
Its just deciding what is excessive


http://www.boltscience.com/pages/screw8.htm

http://www.roymech.co.uk/Useful_Tables/ ... d_tol.html



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