Bolts vs clevis

[vic008]

Does anyone know why it is we use clevis pins/split pins on our rigging as against using SS bolt with castellated nuts. Would be happy using the later.

 

[sailorman]

there are no threads on a clevis pin to abraid & they allow articulation as they are not done up tight

 

[rogerthebodger]

There are a number of reasons. The main one is cost a clevis pin is cheaper to make than a bolt, nut and split pin.

As Sailorman says the thread could abraid and in any case is not at strong in shear size for size due to the reduced dia of the thread minor dia.

As far a articulation is concerned again as Sailorman pointed out if you tighten up a bolt it would stop all articulation but the current design allows too much articulation as the clevis pin should be fixed in one part and free to rotate in the other so the largest bearing area rotates spreading the ware other wise the smaller bearing area would tend to ware quicker.

Noe the cost effective design of components being value engineering is a subject of study on its own.

The clevis pins below don't even use split pins

http://www.google.co.za/imgres?imgu...4lYVaXGGMORsQSo9IEQ&tbm=isch&ved=0CB8QMygEMAQ

All kinds of designs below

https://www.google.co.za/search?q=c...niv&sa=X&ei=NolYVev_E_PlsAT3pYFQ&ved=0CBsQsAQ

 

[Alpha22]

I was once told by an MOT inspector that they were "hardened" and bolts were not..... I had them in the handbrake mechanism of my Triumph Spitfire.....

 

[PuffTheMagicDragon]

The strength of a 'pin' that is in shear depends on its cross sectional area. A clevis pin that fits an 8mm hole will have all of the area that is in its diameter whereas an M8 x 1,25 bolt will only have the core, more or less a diameter of 6,65mm only; much weaker.

Of course one can also find 'bolts' with a plain part (as distinct from machine screws that are more readily available) and have all the load supported by the plain section, but then there will be the problem of undoing the nut in a hurry if it this becomes necessary. With a proper clevis you just pull out the keeper ring, with a pair of pliers if necessary.

 

[wklein]

Often difficult to get clevis pins in or out. Trying to get a bolt out without damaging the thread would be quite difficult. Hate split pins but seem to be best solution.

 

[VicS]

The objections raised above may be valid for set screws and machine screws but surely you would not use them you would use bolts with all the loads on the unthreaded shanks, and only the nut on the threaded portion, as Puff points out

That might mean though that the bolts would have to be non standard dimensions in regard to the shank and thread lengths vs the diameter.

 

[rogerthebodger]

The objections raised above may be valid for set screws and machine screws but surely you would not use them you would use bolts with all the loads on the unthreaded shanks, and only the nut on the threaded portion, as Puff points out

That might mean though that the bolts would have to be non standard dimensions in regard to the shank and thread lengths vs the diameter.

Vic both you and Puff are correct in that bolts have a full diameter portion but I don't know if the tread length is properly standardised but when I was in Engineering design we used to use an approximation of 2 1/2 times bolt diameter as the thread length. Its not good design to tighten a nut up to the end of the thread as it will distort the thread inside the nut. The correct way to use a bolt in a clevis is to use a shoulder bolt and tighten the nut up to the shoulder. This still does not prevent the bolt turning in the clevis as described in my previous thread.

 

[PuffTheMagicDragon]

Vic both you and Puff are correct in that bolts have a full diameter portion but I don't know if the tread length is properly standardised but when I was in Engineering design we used to use an approximation of 2 1/2 times bolt diameter as the thread length. Its not good design to tighten a nut up to the end of the thread as it will distort the thread inside the nut. The correct way to use a bolt in a clevis is to use a shoulder bolt and tighten the nut up to the shoulder. This still does not prevent the bolt turning in the clevis as described in my previous thread.

I agree about the use of a shoulder bolt to retain the free movement and to avoid distortion of the thread (although one could still use a Nylock nut) but why use one in preference to a clevis? What is the advantage?
Removal in an emergency (dismasting?) would still require two spanners as opposed to a quick yank with a pair of pliers. IMHO.

 

[rogerthebodger]

I agree I would never use a bolt of any kind if emergency removal was required.

If quick removal is needed on a more regulator basis than just emergency's I would use a drop nose pin where removal does not need any tools what so ever.

I have used drip nose pins on my life raft frame that can be padlocked when in dock and removed when sailing but prevents accidental loss but easy removal without tools.

You should still prevent the clevis pin from rotating in the clevis.

 

[Avocet]

You could just make sure the bolt bottomed-out on the underside of its head against the side of the shackle (or whatever it was) before it bottomed-out on its thread. That would save any possible thread distortion problems. I don't think standard clevis pins are especially hard. I have one as a souvenir from my last car, which I broke at 248,000 miles. It was the clutch master cylinder pushrod clevis and had been "sawn" about 1/3 of the way through by the clutch pedal! Like others though, I can't really see an advantage in using a bolt. I'd still want to lock it in something like a rigging application so there would still have to be a split pin or something similar through the end that was sticking out.