Air Compressor - Vane on big end

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Fri 10 Jul 2020 14:25
Air Compressor - Vane on big end - edlithgow

This vane thing on the bottom of the big end bothers me, partly because I don’t know what its for (oil fling? retaining spring? I've never taken a compressor apart before) and partly because I cant remember which side it was on,

4000×3000 2.18 MB

I should be able to correct the latter oversight (Tsk Tsk) if I stare at the valving for a long while before furthet dismantling.

Edited by edlithgow on 10/07/2020 at 14:27

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Fri 10 Jul 2020 23:21
Air Compressor - Vane on big end - focussed

The "vane thing" is indeed an oil flinger paddle. Often seen on the big-end of splash lubricated small engines, but usually the flat surface would be at 90 degrees to where yours is, so it throws oil up the bore and all around. Just in case, as it is a compressor and not an engine, find a compressor parts diagram and check which way round it's supposed to be.

Please use loctite screw lock or equivalent on the threads of the retaining screw after degreasing the male and female threads first., if you need to change the position of the paddle.

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Sat 11 Jul 2020 01:07
Air Compressor - Vane on big end - edlithgow

Thanks.

A 90 degree shift would make sense for more efficient fling, but maybe the impacts would be too severe?

There's something similar in this video, also a Taiwan compressor, at about 9.25 coming out and 21.35 going back in, but that one is part of the con rod casting and probably roughly circular in section. Seems to be assembled to be on the outside. I'll look for more info.

Lost my Loctite when the University threw out the break-room fridge. Might risk using polythene instead.

https://www.youtube.com/watch?v=d_phoo4LTao

This junk pile compressor SEEMS just to be suffering from a sticky piston cos the oils a bit degraded. I might run it for a bit with motor or hydraulic oil to wash it out, though I understand non-detergent oil is recommended for long-term use

Edited by edlithgow on 12/07/2020 at 02:12

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Sun 12 Jul 2020 22:31
Air Compressor - Vane on big end - Big John

Seem to remember something similar on an old Suffolk Punch lawn mower engine to splash lubricate with oil.

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Tue 14 Jul 2020 04:59
Air Compressor - Vane on big end - edlithgow

How big a problem is oil getting into tyres from the compressor?

The one on campus, used by students to air-up scooter and bicycle tyres but not accessible to cars, has no inline oil filter that I can see, so I'd think some oil mist would get in and could degrade the rubber.

Probably not significant on a short life tyre, but I recently retired my Bridgestones at 15 years, so it could be an issue for me

Solutions/work-arounds might include

1. Getting / making an inline filter (tricky techno-shopping here but maybe do able)

2, Shutting off the pump for a while before aring up, allowing oil to settle out of the air in the tank.

3, Running it with brake fluid as a lubricant> I may do this as part of the cleanup but running it under load like that is perhaps too abusive,

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Tue 14 Jul 2020 10:17
Air Compressor - Vane on big end - bathtub tom

How big a problem is oil getting into tyres from the compressor?

It may help to maintain pressure. Rubber molecules are larger than air, allowing some air to escape through the rubber (so I'm told). Perhaps a coating of oil could help prevent this? The tread must experience a deal of oil picked up from the road surface.

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Wed 15 Jul 2020 03:51
Air Compressor - Vane on big end - edlithgow

How big a problem is oil getting into tyres from the compressor?

It may help to maintain pressure. Rubber molecules are larger than air, allowing some air to escape through the rubber (so I'm told). Perhaps a coating of oil could help prevent this? The tread must experience a deal of oil picked up from the road surface.

Well, oil molecules are larger than air molecules too, so I don't see the what there.

Mineral oil degrades rubber, hence the (widely ignored) strictures not to use it on brake systems.

Tis true tyres will be exposed to a bit of oil from road surfaces, but it'll tend to get worn, spun and washed off there. Not so on the inside.

Maybe 8 years or so ago I tried surface treating the outside of my tyres with sunflower oil as a potential preservative, believing vegetable oil didn't attack rubber. I now believe (based mostly on rapid softening and failure of a crunchy old rad hose so treated) this was a mistake, and may have contributed to the failure of two of the tyres at the ripe old age of 15 years, prompting replacement of the other two.

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Wed 15 Jul 2020 09:37
Air Compressor - Vane on big end - bathtub tom
Well, oil molecules are larger than air molecules too, so I don't see the what there.

Are oil molecules smaller than rubber molecules (sorry, I failed 'O' level chemistry) and if so couldn't they fill the gaps?

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Wed 15 Jul 2020 00:13
Air Compressor - Vane on big end - focussed

I would hazard a guess that the "paddle" has been bodged in the past by being turned 90 degrees to stop oil properly lubing the compressor and hence needing an oil separator to prevent oil mist coming out with the compressed air. Doing this lunched the compressor!

What a strange part of the world you live in if this is the train of logic that prevails!

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Wed 15 Jul 2020 04:07
Air Compressor - Vane on big end - edlithgow

I would hazard a guess that the "paddle" has been bodged in the past by being turned 90 degrees to stop oil properly lubing the compressor and hence needing an oil separator to prevent oil mist coming out with the compressed air. Doing this lunched the compressor!

What a strange part of the world you live in if this is the train of logic that prevails!

Nice theory.

No logic prevails here, so I doubt anyone worked that one out.

I don't know if the paddle is 90 out. Its a slight angle out of vertical so would still sling some oil. I'll do some searching. MIGHT even be possible to get someone to ask the manufacturer, if still operating, since its a Taiwan made item.

Current indications are it was gummed-up due to oil degradation. I removed the piston and cylinder as a unit earlier since I don't have a ring compressor. Went back to it last night and the piston had stuck in the bore, but brake fluid freed it up eventually. Gummy rings but cleaned up nicely. Wrist pin still stiff so I'll probably take that apart next.

forumosa-12829.kxcdn.com/uploads/default/optimized...g

Lots of compacted wear metal in the bottom of the sump but I dunno if that's abnormal for non-detergent oil.

forumosa-12829.kxcdn.com/uploads/default/optimized...g

The drained oil was pretty dark but of course I don't know what colour it was straight out of the bottle.

forumosa-12829.kxcdn.com/uploads/default/optimized...g

Edited by edlithgow on 15/07/2020 at 07:38

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Thu 16 Jul 2020 05:10
Air Compressor - Vane on big end - edlithgow

Is there any reliable convention for ring end gap offset AKA "clocking"?

I didn't note where they were when I took the piston out (Tsk Tsk) and of course they got moved around when I was cleaning them up.

It (belatedly) occurs to me that if the bore is oval (Seems quite likely. All that metal came from somewhere) and I put the rings back in a different orientation they'll likely leak more and/or break.

There are the conventional 2 compression rings and an oil-control ring, though the latter may be a single unit rather than the usual spring-and-two scrapers. It has oil holes behind and below it.

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Thu 16 Jul 2020 08:55
Air Compressor - Vane on big end - paul 1963

I'd put them back with the gaps 120 degrees apart.

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Thu 16 Jul 2020 13:18
Air Compressor - Vane on big end - edlithgow

I'd put them back with the gaps 120 degrees apart.

Yeh, that makes sense if the oil-control ring is a single unit (I'll probably have to take it off to confirm that) since there are then only three gaps.

Starting where (relative to the wrist-pin axis and perhaps the direction of rotation)?

Theres an arrow on the piston top which I THINK pointed to the trailing edge', perpendicular to the crankshaft

I could mine the internyet for a majority view, I suppose. Mostly about petrol engines, though I cant see why they'd be different

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Thu 16 Jul 2020 15:13
Air Compressor - Vane on big end - bathtub tom

I'd put them back with the gaps 120 degrees apart.

Yeh, that makes sense if the oil-control ring is a single unit (I'll probably have to take it off to confirm that) since there are then only three gaps.

Starting where (relative to the wrist-pin axis and perhaps the direction of rotation)?

Theres an arrow on the piston top which I THINK pointed to the trailing edge', perpendicular to the crankshaft

I'd leave the rings where they are, unless you have a source of replacements. Last engine I re-built, I was very, carefully removing a ring to check for bore wear (it had been re-bored to the max and we wanted to get away with just new rings if possible). A colleague said "you don't need to be that careful, just open one up like this" - TING. Another colleague tried, with the same result. I wonder if they get brittle with age?

I wouldn't try overthinking where you put the ring gaps, just spread them round, evenly.

IIRC the arrow on the piston usually points to the 'thrust' side on an ICE. Probably not so critical on a compressor.

What's this compressor for and why are you dismantling it? Don't you reckon just unsticking the rings and giving it fresh oil will extend its life enough?

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Fri 17 Jul 2020 05:34
Air Compressor - Vane on big end - edlithgow

Thanks.

Did your colleages get brittle when punched on the nose?

Re"just unsticking the rings and giving it fresh oil"" that's all I'm doing really, assuming nothing else (say pressure switch) is broken.

I want the rings in the original locations (which of course I should have noted when I took the piston out) because there seems to be quite a lot of wear and I'm afraid they'll leak more or even break if re-postioned.

I tried a quick trawl of the internyet for a concensus and its all over the place, with more than one configuration being recommended even for the same engine.

Finding "the best" orientation isn't really what I want here anyway. I want it back the way it was.

Probably worth trying a query to the manufacturer before re-assembly.

Edited by edlithgow on 17/07/2020 at 05:43

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Sun 26 Jul 2020 13:26
Air Compressor - Vane on big end - edlithgow

Thar she blows!

Bubbles

I have “shop air”. Now I just need a shop. Or a shed, though “shed air” doesn’t seem to be a thing.

I don’t have much air though. It builds pressure very slowly, so slowly that I assumed the guage was faulty, and started to get nervous about explosions, since I don’t know that the pressure switch works.

Its got a substantial leak from the cylinder outlet fitting, which looks like it needs a new compression fitting olive. Soapy water didn’t find any others but the suction doesn’t seem very strong either.

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