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Bolt recommendation


white90
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After this happened:http://forums.lr4x4.com/index.php?s=&s...st&p=303272

to a 12.9 rated cap head screw

The new thread is M12 but what rating bolt to use?

8.8 or 10.9

I'm going with Simons suggestion 12.9 may be too hard/brittle

What does Jim recommend??? The guys who make his mainshafts are quite good and should be able to advise on the best option given the type of loading it'll see.

I'd have thought a 12.9 would be a better option as it has a much higher tensile strength than the 8.8. It may just be the photo but it appears as if the failure on the old bolt was not a brittle type failure - the bolt appears to have necked before failing showing it went through the plastic phase. If this was the case all that would have happened with an 8.8 is it would have stretched a little more and failed earlier.

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John most helpful comment. ;)

It may be hard to believe, but I wasn't being sarcastic. If your winch can fail and propel you back down a climb with potentially very bad results, I'd be looking very closely at stopping it from happening again. I'd find it very hard to own a winch that could try to kill me at any moment :o

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It may be hard to believe, but I wasn't being sarcastic. If your winch can fail and propel you back down a climb with potentially very bad results, I'd be looking very closely at stopping it from happening again. I'd find it very hard to own a winch that could try to kill me at any moment :o

A good point but is there a winch that cant?

Ive had similar problems with the low line winch popping out of engagement and Milemarkers are known for the drums breaking. The superwinch Husky would probably be your best bet but but they are painful to use.

In all fairness the 12mm bolt is stronger than it needs to be so I'm happy with that.

The only time Ive had an a&$e twitching breakage was at the top of a near vertical 60 ft drop in Ireland when the rear winch rope broke just as I went over the edge :o :o

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I would've thought a better designed thing for the bolt to go into is the answer :ph34r:

FF, Quaife make the mainshafts. They are not in the habit of making stuff that isn't fit for purpose. TBH I feel much safer with a bolt than the standard circlip arrangement - if a 12.9 let go I don't think a circlip would have faired much better.

All credit to Jim he is offering an exchange on the earlier mainshafts for a very small price.

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True all winches have the potential to drop you if they really f**k up, but not many I've seen have the potential to do it so very easily.

...and I would add I'm really not after starting an argument about winches as those just degenerate. I'm just interested, engineering-wise, if there's not a way of correcting what seems to be a rather significant problem. A bigger bolt is one solution, but prevention is better than cure.

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John

I see what you mean

I've had 2 failures now with the 8274

one in standard guise brand new out of the box at West Harptree

the circlip shot off dropping me 80ft down a pretty steep slope, bit like a roller coaster ride backwards,

Then Sat Week ago the bolt snapped no hair raising moments as we were at the top of a climb, but I then had to reverse down with no means of stopping once I was over the lip, this was unpleasant in the extreme.

I could have just replaced the bolt with a better spec(Titanium) but like you say I was unwilling to use the winch in that guise again, as confidence had gone.

Steve told me of the new upgrade So I've had it done but it arrived minus the bolt so i need to source the correct one.

PS nine posts and only one recommendation from my favourite measurement GURU MrW

Please can I get some more :rofl:

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I would be inclinded to agree with Will I am afraid...

12.9 will be more brittle, but has a significantly higher breaking strain on it to start with, so will take more force before you start to see any deformation.

hth

Mark

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After this happened:http://forums.lr4x4.com/index.php?s=&s...st&p=303272

to a 12.9 rated cap head screw

The new thread is M12 but what rating bolt to use?

8.8 or 10.9

I'm going with Simons suggestion 12.9 may be too hard/brittle

12.9 are stronger than 8.8 or 10.9

12.9 might be more brittle, but deformation will occur at a much greater load, where inferior materials alreade has broken apart.

The bolt strenght code is made of two numbers separated by a dot.

Multiply the left number with 100 and you have the ultimate strenght in newton pr square milimetre

The right number is an indication of the yield strengt - eg the load the bolt can be subjected to before ir-reversible deformation starts. Calculate either as a percentage - or easily by multiplying by 10 times the preceeding number.

Examples:

A 12.9 bolt has a ultimate strength of 12 x 100 = 1200 newton pr square milimetre

A 12.9 bolt has a yield strengt of 9 x 12 x 10 = 1080 newton pr square milimetre

A 8.8 bolt has a ultimate strengt of 8 x 100 = 800 newton pr square milimetre

A 8.8 bolt has a yield strenght of 8 x 8 x 10 = 640 newton pr square milimetre

The 12.9 is therefore considerably stronger in all aspects than its 8.8 counterpart

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What does Jim recommend??? The guys who make his mainshafts are quite good and should be able to advise on the best option given the type of loading it'll see.

So which one of them started off designing in the use of the M8 bolt then? :blink:

Chris

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My vote goes with the 12.9 and replace / inspect during service periods.

Exeter Wire & Rope keep 12.9 allen screws in stock .....................

A good point but is there a winch that cant?

Milemarkers are known for the drums breaking.

Indeed, but that was the early models that had a very very poor weld on the drum to cheek (motor side). The weld would break when subjected to the high side loads of synthetic rope pulling down between the wraps.

A good clean up and a decent bit of quality gluing fixes the issue.

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Tony,

I agree that the previous failure was due to lack of strength. The bolt had obviously necked as Will says before it failed. (I am assuming that was from the brake load and not over tightening! :P:ph34r: )

Going from an M8 to an M12 will give you an approximate increase in tensile area of 225% (don't have the actual threaded areas to hand)

so even with an 8.8 you would have significantly more strength.

As calculated above, an increase in material grade will give an additional increase in strength.

Without knowing the applied loads I couldn't say what grade is "enough" but I don't think there would be sufficient cycles of loading to induce a fatigue failure in the higher grade bolts. You could always replace the bolt as a service item I suppose.

Hope this helps.

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After this happened:http://forums.lr4x4.com/index.php?s=&s...st&p=303272

to a 12.9 rated cap head screw

The new thread is M12 but what rating bolt to use?

8.8 or 10.9

I'm going with Simons suggestion 12.9 may be too hard/brittle

I wonder if a bolt would be better than a screw. That screw looks as if a shank there would be better ?

mike

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Tony

FWIW I now see that the bolt mm size is bigger,

as bish says the core size means a Huuuuge increase in strength,

but,

and its a big one ....

don't then undo that strength gain by going down the 10.9 vs 12.9 bolt route.

As others have said 12 is stronger than 10 is stronger than 8, yes 12 is more brittle, but its stronger,

so when the 10 goes "ping" the 12 may be deforming a bit but will still be in one piece long after the 10 has broken,

Yes 12 is more brittle, but it would still need far more load / shock load / twist force before it breaks over a 10 bolt

Fit lightly oiled 12.9s rather than 10.8s

And I too think fridge does have a valid point, no winch should become scrap for the day due to a tiny weak design flaw / too smaller bolt :(

This upgrade does move it hugely upwards in the strength dept, as to if even this will be enough time I guess will tell

Nige

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Well now I'm in a quandary :)

I was supplied 8,8 by Jim(gigglepin)

I fitted 10.9 but have 12.9 cap head.

Should I just go 12.9 and forget 8.8 and 10.9?

The winch becoming scrap is a valid point

There have only been a couple of failures of the M8 apparently

at least Jim has sorted the issue, I'd have far rather known before travelling300miles round trip to slindon but there you go.

I heatedly recommend anyone with a Upgraded main shaft with an M8 bolt should seriously consider the move up to M12.

It could have been far worse and I had lost total confidence in the winch after the failure so in a small way I'm happy the upgrade is available

and mine is done, for the next time.

PS Will yes I'm keeping it.

I put it down to a mid life crisis hitting 40 has its downsides :)

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