Clevis pins substitute?

[zoidberg]

A question for the tinkickers and mecheng'ers among us.....

I'm looking hard at my split-backstay triangular link-plates and their clevis pins - the only rigging components not yet replaced - and I'm wondering about alternatives to the clevis pins - and their cotter pins/split pins/split rings which can snag on sails, lines and fingers.

For example, this at £86 plus post, and rated at 6500kg....

Clevis pins in M12 are plentiful, from about £3 ( depending on chandlers ), and s/s plates in 5mm cut to size locally and self-drilled would be about £10.
The use of M12 s/s bolts with appropriate unthreaded shoulder would also be 'cheap as chips', and a Nyloc-type locknut could be used to advantage.

Can the assembled sage community advise on pros and contras....?

 

[Neeves]

I think key ring type split rings don't work very well in larger diameter clevis pins, the hole is straight the ring is circular. Split pins do catch sails but quite why your sails are going to get wrapped round the back stay is a question you might ask yourself . You can always wrap the plate with amalgamating tape and cover the split pins. I'm not sure that you can source stainless bolts with plain (unthreaded) shoulders of the dimension you need - but nyloc nuts do have appeal. Making your own backstay plate(s) has enormous appeal (at the price you quote). I really don't think you need a backstay plate rated at 6.5t on the yacht you are working on. If you make your own plate(s) you will need a decent and robust bench drill and some pretty decent drill bits and a lot of machining oil (been there done that). Drilling your own clevis pins is not easy - primarily because you are drilling a 'slippery' cylinder.

I'd buy some stainless plate and make your own backstay plates, I'd buy extra plate - your yacht will find a use for the extra plate . I'd use split, cotter, pins and wrap the eventual device with amalgamating tape (easily removed if ever necessary with the yacht's knife). I'd buy off the shelf clevis pins (you only need 3 - not a deal breaker.

If you don't have the kit to make your own then you would need different options (finding a sensibly priced 'off the shelf' backstay plate might not be easy).

Jonathan

 

[Boathook]

For £86 I would buy the component. Whilst I could make it I don't have the tools to give a nice finish and I have found over the years machining s/s isn't easy.

If you have nothing else to do I would for it though.

 

[Daydream believer]

You do not have to do much machining. Just buy 2 circular discs & drill 3 holes in each. There is no real reason for the shape to be triangular. Draw it out on a piece of paper to check the sizes & see how big the circle needs to be. Then go to someone like M-machine, who do not list but may have if asked & buy 2 discs. If you have a lathe then you could chamfer & re face the outer 2 faces to make them look nicer.
I have bought 4 inch * half inch 316 ss discs in the past, for rope cutter parts, but forget who from. Poss M - Machine
If you are that fussy you could cut 2 splays on the upper part of the triangle & leave the bottom part curved but it will just harden the SS & require more work to chamfer the edges. So best done after the holes have been drilled.

 

[DinghyMan]

For custom laser cut shapes we use Cut Metal Online | Custom Cut Washer, Disc, Letters and Numbers

The holes would be better reamed than just drilled, and stainless set screws would work, or better still book bolts / sex bolts / chicago screws but I'm not sure they are available in M12 - but would also question whether they need to be that big

 

[vyv_cox]

I don't know exact material specs for clevis pins but from observation I would think they are A4-50, i.e. in the unworked condition as annealed. You could bump up the strength using A4-70 bolts, minimum yield strength 700 MPa or even A4-80, 800 MPa.

 

[Refueler]

Why not replace with a 3 point block with rope system - then you have adjustable backistay and the fitting you want6 to change is replaced by the 3 point block.

 

[zoidberg]

Thanks, guys, for all the above. It's helpful to this 'bear of little brain'.

I DO have the kit to slice and dice that thickth of stainless so if I can source some suitably-sized pieces I'll likely have a go. And I do know how to 'get a start' on round, slippery clevis pins.... F'r instance, make one place not 'round, slippery' by means of a manual file.

I've determined the existing plates were of 2.5mm stuff and 'home-made'. The BlueWave product sold by JGM uses 5mm material, as shown on their online table. I suppose 4mm might suffice, but that is tabulated for slightly smaller kit. No real need to penny-pinch, so I'll happily copy the scantlings...

Same thing with the diameter of the clevis pins. The existing ones are 12mm - but perhaps that's what was available to the original owner/maker. I'd like to use the same size as per the table in JGM's website, for I know no better. And I'll try to find some suitable A4-70 bolts....

 

[rogerthebodger]

Some time ago whe I was rigging my current boat I made similar plated to connect the for and aft lowers to the mast.

The original like you were too thin and caused the clevis pins to ware grooves due to the thinness of the plate and the fact that the clavus would rotate in the plate.

I mad mine from 6 mm stainless cut and shaped using and angle grinder. these days I would get it laser cut including the holes smaller than needed so I can drill then out.

The pins I would now use a tab on one end with hole the is bolted to the plate to hold it in without a split pin and to prevent the pin rotating

Bolt through the hole in the tab

 

[justanothersailboat]

The holes would be better reamed than just drilled

ok, that's interesting. You have more engineering experience than me. Are the holes pivot enough and the pins close fitting enough for that to matter? (does that mean that mine is not good enough because it's not that close a fit?)

 

[zoidberg]

Ah, 'rogerthebodger'. Thanks for that.

With that name, we must be related somehow....

 

[Neeves]

Ah, 'rogerthebodger'. Thanks for that.

With that name, we must be related somehow....

Its a big family.

 

[rogerthebodger]

Its a big family.

The world over and the advantage of a big family is that we do have different knowledge and experience to draw from

 

[rotrax]

The world over and the advantage of a big family is that we do have different knowledge and experience to draw from

One of the cleverest men I ever knew invented Pub Optics for accurate drink measurement.

He also sponsored me with a racing motorbike.

He told me "An Engineer is a bloke who can make for a tanner wot everyone else buys fer a quid!"

I think he was right!

 

[rogerthebodger]

One of the cleverest men I ever knew invented Pub Optics for accurate drink measurement.

He also sponsored me with a racing motorbike.

He told me "An Engineer is a bloke who can make for a tanner wot everyone else buys fer a quid!"

I think he was right!

I know value engineering can be a dirty word, but it does have its uses when a manufacturer makes lots of a single item.

An example is pivot / clevis pins that can be made several ways

1) machine the bar to the required dis leaving a head to hole the pin on one side with a hole drilled in the other end for a split pin.

1 machining operations on 2 different machines plus waste metal on the pin Dia

2) cut off a pin of the required diameter and drill a lobe in each end to the split pins to retain the pin

3) nut and bolt that require threading both the nut and bolt, the bolt head can be upset and the thread rolled but the nut needs cutting off an at least tapping the thread.

4) a clevis pin with akeep plate in a milled slot in the pin to hold the pin in place. the keep plate needs 2 holes drilling in the keep plate and a holes / tapped in the fixed item the pin passed through and 2 set screws of bolts and nuts

5) the pin I posted the pic of with a welded tab on one end that located the pin and prevents rotation using a tab with one hole in the tab for one hole to fix it to the fixture and one bolt and one hole / tapped hole.

6) A simple pin wit circuip grooves in end for a circlip of a E clip

Pick the one you like all can do the job and there could be others with spring clips or quick release of drop nose pins I have used all kinds during my engineering design work

 

[zoidberg]

Pick the one you like all can do the job

I just want one that a flapping sheet can't flick free or a meandering errant sail can't tear itself on...

 

[rogerthebodger]

I just want one that a flapping sheet can't flick free or a meandering errant sail can't tear itself on...

For that application I would go for No 5 or No 6 as the least likely to damage sails or lines and are very unlikely to be flicked free.

 

[penberth3]

The pins I would now use a tab on one end with hole the is bolted to the plate to hold it in without a split pin and to prevent the pin rotating

Bolt through the hole in the tab

That's the sort of thing you see on excavator buckets etc. It's a very clumsy solution for 12mm pins. The securing bolts will be tiny and need a threaded hole in the plate which is more hassle.

 

[Daydream believer]

For that application I would go for No 5 or No 6 as the least likely to damage sails or lines and are very unlikely to be flicked free.

I would certainly never go for an e clp in that situation. E clps are Ok for the use on shafts to locate bearings etc where the side forces are not great. However, the backstay could work to one side of the unit- even by a very small amount- due to the necessary play required for fitting etc. This could put an undue force o the end with the E clip leading to failure over time. They do fail and the fitting against which they sit do tend to make them shear off, or shatter in the grouve. I have seen this.

 

[Daydream believer]

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