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Crank pin torque

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Crank pin torque

Post  Gary B on Wed Dec 20, 2017 4:01 am

Hi guys
Can anyone give me a torque value for the crank pin nuts on a villiers 17A motor..thanks

Gary B

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Torque settings

Post  piston 197 on Wed Dec 20, 2017 5:39 am

I have never seen any figures for the crank pin nuts, the Flywheel torque is around 62Ft/Lb though, achieved by holding the flywheel with a flywheel strap, or using a Villiers "hammertite" spanner and beaten with a hammer until it will no longer go any tighter !

When we used to build 350cc and 500cc four stroke big ends we used to use a long handled socket bar with a 3Ft length of tube slipped over the end, one nut was held in a socket on a piece of square bar in a vice and the other one was pulled up as hard as we could with the bar and tube, Never stripped a nut and never had one come loose.
Not scientific, but it worked, none of the Villiers or FB book by JH Goddard ( FB Service manager) quotes any figure and states this job is best left to industry specialists ?

JH
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Re: Crank pin torque

Post  Gary B on Wed Dec 20, 2017 5:45 am

Thanks John I will tighten them up and see how they go.

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nuts!!

Post  john87 on Wed Dec 20, 2017 9:09 pm

What thread and size are they??

john..

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Re: Crank pin torque

Post  Gary B on Wed Dec 20, 2017 9:21 pm

Hi John
They are 5/8 x 20 tpi

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Crank pin torque

Post  kerabo on Wed Dec 20, 2017 10:27 pm

I just done a quick search. For that size and thread it's going to depend on the quality of the steel used.
128ft/lbs is a middle value.

You can do a lot by feel!

Ken

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nuts!!

Post  john87 on Wed Dec 20, 2017 10:38 pm

Me too!!

The nearest i could find was for 5/8 UNF which is only 18TPI and for what i take was mild steel it was about 82 ft/lbs..

No idea what the crankpin is made of, but at a GUESS i would say case hardened mild steel, as this would give a tough centre and a very hard case..

So, hard to say, as Ken said, you can do a lot by feel...

If the engine sprocket thread is 1/2 [from memory] [and that is 80 ft/lbs or round there somewhere] the flywheel nut is 62 ft/lbs, then i would guess your crank pins are going to be about 100 [or a bit] I presume they have a taper on either end??

john..

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Re: Crank pin torque

Post  kerabo on Wed Dec 20, 2017 11:27 pm

john87 wrote:Me too!!

The nearest i could find was for 5/8 UNF which is only 18TPI and for what i take was mild steel it was about 82 ft/lbs..

No idea what the crankpin is made of, but at a GUESS i would say case hardened mild steel, as this would give a tough centre and a very hard case..

So, hard to say, as Ken said, you can do a lot by feel...

If the engine sprocket thread is 1/2 [from memory] [and that is 80 ft/lbs or round there somewhere] the flywheel nut is 62 ft/lbs, then i would guess your crank pins are going to be about 100 [or a bit] I presume they have a taper on either end??

john..

Have you fitted one before? I know it can be difficult to align. I have only done one of that type and I was a teenager then on an AJS 250. It went pop after couple of hundred miles. I did press back in and align my 20T pin with good results after it moved.
If your lucky it may be keyed

Ken
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Crank pins

Post  piston 197 on Wed Dec 20, 2017 11:43 pm

Personally i have done hundreds, if pressed pin ,non shouldered measure width before pressing up, if shouldered pins ,or tapered pins with nuts ,it is less of a problem,modern crankshafts for Yamaha RD twins used to be splined location and are easy, Villiers twins are a lot more tricky and have to be aligned very carefully and checked for width, ideally in a jig, Ariel arrow ones are basically 2 single cylinder ones, joined together with a taper and an allen bolt.

If unsure job is best left to the professional, nowadays without access to decent trueing and pressing equipment i hand mine over to those better equipped, but at the very least a decent press of at least 2 tons will be needed for pressed pin types like Villiers, and a decent set of wedges and a press for taking them apart .

A friend of mine bought an Ariel engine from South Africa and was assured there was a new big end in it, but stripped it anyway, There was indeed a new big end in it and there was no play and everything felt fine, but didn't look like the guy who fitted it had the proper tooling.There were lump hammer marks in the flywheels where it had been trued, and chisel marks in the crankpin nuts where they had been "tightened", but fair dos to the guy it would have ran OK , so anything is possible
JH
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nuts!!

Post  john87 on Thu Dec 21, 2017 12:42 am

I would agree with all that.. I have trued a few cranks, but never split one.. Anyway, i have a press and a large surface plate and vee blocks and dial test indicators and the like, so it is no big deal to me.. If you do not have this sort of stuff i would not even try and do it..

john..


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