Over-lubrication?

Over-lubrication?

Postby Mainliner » Sat Nov 25, 2017 11:41 am

Can 'over-lubrication' adversely affect the performance of a PCP airgun?

Since giving the cocking mechanism of my Alfa pistol a 'good squirt' of spray lubricant, it has behaved strangely. Initially, during a session, the shots fall low, and to the left. But gradually, over time, they return to on-target.

Any ideas?
Thanks.
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Re: Over-lubrication?

Postby TenMetrePeter » Sat Nov 25, 2017 1:35 pm

PCP guns use a sliding hammer block with a spring behind it. Cocking pulls back the hammer against the spring. The trigger releases the block and the spring drives it toward a firing valve. Any oil on the hammer rail, particularly silicone, will slow down the hammer dramatically. Hammer rails should be dry. That's probably what had happened.

The science - frictional (dry) drag between two surfaces is independent of velocity. Viscous (oily) drag is proportional to velocity squared. So a viscous oil will limit to a terminal velocity quickly, in this case before it hits the valve. Useful for slow close toilet seats but not guns. . As the oil seeps out it returns towards friction but with a viscous component.
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Re: Over-lubrication?

Postby Mainliner » Sat Nov 25, 2017 9:50 pm

Peter

Thanks for your input. I now have to consider how to clean the affected area. I'm thinking about using a solvent spray (e.g. brake cleaner) to 'rinse' the oil away - or will that make things worse?
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Re: Over-lubrication?

Postby TenMetrePeter » Sun Nov 26, 2017 8:15 am

If you can get to the hammer spring area with say Napier degreaser it would help but other degreasers may harm seals. At least you can ask Napier for advice .

EDIT: Napier just told me this may soften airgun seals

When it happened to my FWB I had no choice but to strip it as the pellet wouldnt even reach the 10m target
I dont have any practical knowledge of the Alpha but if the oil can get in I assume degreaser can.

You could just shoot it and see if it settles but if you used WD40 its going to get stickier.
Last edited by TenMetrePeter on Mon Nov 27, 2017 10:27 am, edited 1 time in total.
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Re: Over-lubrication?

Postby Mainliner » Sun Nov 26, 2017 4:06 pm

Peter

Thanks again for your advice. I'll certainly investigate the Napier degreaser suggestion.

Your diagnosis of the problem seems correct. The power output has definitely dropped off considerably - I can now see the pellets in flight!

I actually used 'Glide' spray to lubricate the cocking mechanism - it incorporates PTFE in the formula. I don't know whether that will be good or bad for the outcome.

But I've certainly learnt something new - I thought lubrication of moving parts was always good, but not any more.
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Re: Over-lubrication?

Postby TenMetrePeter » Mon Nov 27, 2017 10:18 am

I just got a reply from Napier. Do NOT use their rapid degreaser on airguns as it may soften seals.

I favour lighter fluid as its petroleum and is allegedly resisted by Nitrile and Viton.
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Re: Over-lubrication?

Postby Mainliner » Wed Nov 29, 2017 11:16 am

I have received the following information from Air Arms:

'The technical department has advised that spraying a degreaser of any kind is a bad idea.
The fluid may get into the mechanism and cause rust issues. The action should be stripped down, cleaned, and re-assembled with the correct lubrication.'

'The technical department has advised that the striker should be lubricated, as it is a metal-to-metal moving component.
The lightest cover of oil is best, using a high viscosity oil. A sewing machine oil could be used. All lubrication on the striker must be light. A 'good squirt' is probably too much.'


In view of the above, I have re-examined the cocking mechanism. It is possible that the slider buttons may have been set too tightly, causing some 'drag' on the striker once the trigger is pulled. So, just in case, I've slackened them off a bit and incorporated some free play as well. Hopefully, things will improve.
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Re: Over-lubrication?

Postby TenMetrePeter » Wed Nov 29, 2017 3:17 pm

Not sure about "high viscosity sewing machine oil"? It's usually very thin stuff.
I dont know enough about the Alpha and the buttons but it seems from the parts diagram to be a miniature version of the rifles - drilled cylindrical striker hammer on a cylindrical rod hammer rail?
I prefer a dry lube like rubbed-in rubbed-off pure molybdenum disulphide (MoS2) paste.
Dri-slide from USA used to be available to dropper into spaces and it was MoS2 suspended in petrol. Sort of degreaser and dry lube in one. Difficult to get now and very expensive. Brilliant for your semi auto Colt!
I paint the odd drop onto mine with a fine artist brush.
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Re: Over-lubrication?

Postby Raj » Sun Dec 03, 2017 10:05 pm

Sperm works well .... as I accidentally found out when I was caressing my S200 once. :oops:
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