Bonnet striker puzzle

[Ducati750cc]

Originally Posted by COLVERT

Not sure about that. The threads have a force in one direction induced by the spring. Any minute vibration will have a tendency to unscrew the bolt due to the uni-direction force generated by the angle of the thread.

I have often discovered loose screws in electrical plugs and sockets after several years use. ( Thermal expansion and contraction makes them slowly unscrew. )--This same force of hot and cold will cause those bonnet screws to undo unless firmly locked by the associated lock nut.


Just my observations though I'm happy to be proved wrong if that's the case.

Probably why thread lock is popular.----

Thermal expansion and contraction can't provide a turning motion to ' unscrew ' the screw, can it , especially in such as a household socket not subject to vibration !



Loose screws in such electrical static situations, wall socket, are usually caused by a combination of things, cold flow or slump of the copper, the correct way to tighten new assembly electrical screwed connectors is to initially tighten the screw, then go round and re-tighten a few mins later you will usually find you can get up to an extra half a turn or more, even when using the same torque, this is due to the copper being subject to cold flow as it settles, but not many do this, more prominent on soldered tails.



So it isn't loose because the screw has turned, its loose because of the cold flow properties of copper.


The then, not 100% connection, generates heat due to micro arcing, this increases the poor connection and the cycle goes on till greater arcing anneals the copper which flows a little more, more arcing and heat damage to the insulation etc.


This is why I.E. regs state that where terminals / connections may be inaccessible, that only maintenance free connections are allowed such as pressure crimping, or the live spring type such as Wago which can compensate for cold flow of the copper tail, think of a jubilee clip, or the spring type of hose clip, the spring type is always applying pressure as the hose ' settles' over time, a jubilee clip need physically tightening.


An odd thing about loose terminals is that all three conductors are equally subject to it, but for various reasons it is more frequent on the neutral terminal especially on plugs, but this is a discussion for another day.









next time you get a lose screw in a plug or socket pull the conductor out and check the

[SD1too]

Originally Posted by clf

The gap is visible.in image 2. It only would need to be 'just cracked' if the thread is being wound out.

I thought that someone would say that! For my explanation, please read on.

Steve has labelled image 2 as illustrating loosening with an open ended spanner but the photograph doesn't show that. This process is actually shown in image 3 which was taken one minute later. There is therefore sufficient doubt whether or not the nut had been loosened in image 2.

Regarding the point about the nut only needing to be "just cracked", this exercise was to demonstrate that the nut was a locking device which can be released. It is therefore essential to show clearly in any photograph that the nut has been separated from the plate. Image 2 doesn't provide sufficient clarity in my view.

Steve has been very generous with his time, venturing outside to wield tools and take photographs at the same time, then assembling it all in a post for my benefit. I am not criticising him in the slightest. His photographic guides are always brilliant. It was slightly unfortunate in this case that image 2 didn't quite come up to scratch. However, it doesn't matter because I got the message and have now succeeded with my task thanks to Steve's assistance.

Simon

[Arctic]

Hi Simon.
photos 1/2/3 all show the nut cracked and thread showing.
1

2

3


Photos 4/5 show during and after re-tightening.
4

5

None if makes any difference anyways because apparently i am dume and using mole grips adds to ( actually increasing the torsional forces within the metal of the spring, not reducing it...)

This is according to some (post 9 )
https://www.the75andztclub.co.uk/for...d.php?t=316619

Makes you wonder sometimes why you bother, as the mole grips can also be used to turn the pin in the same way as a flat bladed screw driver in the end slot.

[Typhoon190]

Originally Posted by Arctic

None if makes any difference anyways because apparently i am dume and using mole grips adds to ( actually increasing the torsional forces within the metal of the spring, not reducing it...)

This is according to some (post 9 )
https://www.the75andztclub.co.uk/for...d.php?t=316619

Makes you wonder sometimes why you bother, as the mole grips can also be used to turn the pin in the same way as a flat bladed screw driver in the end slot.

Hey Steve.

Don't ever doubt the huge amount of help you have offered, and continue to offer to every member on this forum. A lot of cars would have been moved on or scrapped long ago if it weren't for people like yourself, and fortunately this forum has a considerable number of members that go over and above to help others out.

I believe the majority of us are enthusiastic novices when it comes to maintaining and repairing every aspect of these cars. There are often many ways to tackle each task. Better ways often found by learning along the way after others have tackled tasks themselves. Of course there are those that may be professional mechanics/engineers, and this is also a huge benefit to the club but everyone's efforts should be valued in my opinion.

I'm sure no one meant to insult you.

Ben.

[SD1too]

Originally Posted by Arctic

... apparently i am dumb and using mole grips adds to ( actually increasing the torsional forces within the metal of the spring, not reducing it...)

This is according to some (post 9 )
https://www.the75andztclub.co.uk/for...d.php?t=316619

Thanks very much Steve for re-posting your photographs with the very helpful graphics.

In the other thread, post 9 is purely academic and doesn't offer an alternative way of moving the very powerful spring away from the nut so that a spanner can be used. Don't be deterred Steve! I haven't found a better method than using slim-jawed grips.

Simon

[Arctic]

Originally Posted by SD1too

Thanks very much Steve for re-posting your photographs with the very helpful graphics.

Simon.
I would have used these on the bench to show you but could not find them in the shed, i had flattened the edge to help in the case of the bonnet not opening, they need to be dressed and painted but never got round to it back in 2020.

I have done another mod to stop that, one which i would not have to remove the wheel arch liner and cut my hand to get to the cables.

1

Also makes no difference if you use mole grips on the spring or just and open ended spanner pushed between the spring to crack the nut, the same amount of force to turn the nut is required which is not a lot to be honest, mole grips just made it easier for the nut to be seen in the photos.

[KWIL]

[QUOTE=COLVERT;2911126]

I have often discovered loose screws in electrical plugs and sockets after several years use. ( Thermal expansion and contraction makes them slowly unscrew.)

More likely the trapped wire flows due to pressure of screw with repeated hot/cold cycles..

[JohnnyBG]

Steve (Arctic) your posts have been such a help. I think without the help from this forum I doubt I'd have kept the Rover Connie CDTI Tourer or bought the ZT-T Tourer.

Keep going!

JohnnyBG

[dave lincs]

Arctic is a great help to this forum with his excellent how too do it pictures and detail

[MSS]

Well done gents, I have never experienced so much agreement and harmony on the forum.

Shall we discuss KV6 cambelts next?