Author Topic: A simple question?  (Read 1118 times)

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Offline seagate

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A simple question?
« on: June 19, 2016, 06:38:20 PM »
Now then,when ever you see a video of , or some one talking about spring gun fettling,they often mention polishing the piston . I can sort of understand why, but to my mind surely there's more stiction with highly polished surface,also with say a standard weihrauch piston, they are smooth  but have a surface finish which is designed  to hold just the right amount of lube. Similar to an engine block liner having the correct finish to hold oil as opposed to a glazed liner using oil. So is it just to make the cocking action silky or does it mean more consistency and power for less spring.

Any thoughts or comments on the subject?
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Online airgunnut

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Re: A simple question?
« Reply #1 on: June 19, 2016, 11:17:15 PM »
Your right an engine cylinder is not perfectly smooth it has a criss cross patern to hold oil on the cylinder wall so it makes sense that a springers cylinder should be the same, the smoother the surface the grater the surface aria in contact. there is a massive benefit by filling those micro groves with friction reducing compounds like old fashion grease, moly and now fluropolymers but if a surface is polished smooth there is nowhere for the lubes to go so it gets rubbed off.
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Offline Gambo

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Re: A simple question?
« Reply #2 on: June 20, 2016, 01:39:59 PM »
I agree........shiney is used for 'bling' impressing purposes only. ::)

Something like a piston skirt needs to be smooth (ie. no obvious roughness, high-spots or sharp edges etc), but not so smooth as to display a 'polished' surface.

A certain level of surface marks are absolutely necessary to provide a 'reservoir' to hold the lube.


A similar comparison can be drawn to engine cylinder heads which have been 'ported'. Some tuning companies tout their wares showing highly polished 'mirror finished' intake and exhaust ports, but it has been proven it's the 'shape' of the port that's important, and not the finish on the port surface to extract higher airflow through a motor, and ultimately more power. So yet again, a highly polished finish is for 'bling' purposes only.....and completely useless for anything else!!

Offline seagate

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Re: A simple question?
« Reply #3 on: June 20, 2016, 05:54:38 PM »
A highly polished surface in the inlet tract and around the valve guide area causes drag as the mixture clings to the surface. Where as if a degree of roughness is present the flow increases. This is also evident on aircraft paintwork being textured to increase fuel efficiency.
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Offline Gambo

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Re: A simple question?
« Reply #4 on: June 21, 2016, 11:32:18 AM »
And also why golf balls are dimpled. ;)