Vacuum Gage For Yong Hang Compressor

[USAFANG6799]

Is there a way to figure out how many inches of Hg Vac the Yong Hang compressor draws?
I would like to hook up a vacuum gauge so I can monitor for any vacuum leaks and if the compressor is operating at it's maximum efficiency. Can be valuable info when the compressor is new(get a base line) and after an after an overhaul.

Thanks!

Matt

 

[airgunfans]

I just check the time to fill up the gold filter from zero to 4500 psi. The has been several occurrences of the fill time getting longer than normal and all were found to be due to leakage in external connections. All could be easily detected by just listening for hissing after turning the compressor off. 

 

[USAFANG6799]

Turning off the compressor without bleeding the air first is not advised because of extreme pressure in the high output cylinder head.

I've already experienced this problem and just finished an overhaul due to this happening inadvertently.

That is why if I can monitor the vacuum from one overhaul to the next I'll be able to plan accordingly for the next overhaul.

 

[airgunfans]

Turning off the compressor without bleeding the air first is not advised because of extreme pressure in the high output cylinder head.

I can't see how the "extreme pressure in the high output cylinder head." can do any damage when the compressor is off. It is subject to that level of pressure when it is running anyway. My Yong Heng is equipped with auto stop and I have been doing it for nearly six hours of run time and there has not been any issue. I don't fill tanks but just rifles so it has gone through more than 200 on-off cycles. 

I do have heard people advising not to do that but nobody has offered a convincing reason other than saying that it's not good to let the moving parts to come to a sudden stop. I would ask which part of the compressor is subject to a higher-than-normal load when it comes to a "sudden stop". I guess it is the bearing of the connecting rod ? well, after 200+ "sudden stop", this is the amount of play which I think is normal : 

https://www.youtube.com/watch?v=JB04uqRb6S8&feature=youtu.be

I am just using cheap #100 compressor oil from China that cost 4 bucks per liter instead of anything expensive.

 

[Queequeg]

Wow I haven't taken mine apart yet but if that is normal play for an unpressurized lube system they don't put much emphasis on close tolerances.



That's loose! 

 

[USAFANG6799]

Wow I haven't taken mine apart yet but if that is normal play for an unpressurized lube system they don't put much emphasis on close tolerances.



That's loose!

No not at the price they sell them for.

To get into a compressor with tighter tolerances you'd probably have to double the price of entry.

Just a guess.

 

[airgunfans]

Wow I haven't taken mine apart yet but if that is normal play for an unpressurized lube system they don't put much emphasis on close tolerances.



That's loose!

Bear in mind that there is not any ball bearing or bushing here but just the aluminium of the rod rubbing against the steel pin of the crank shaft. I haven't checked it but I believe the fitting was more or less like this when the compressor was new. If the fitting is tighter, it may seize. Anyway, the most important thing is it is working and working well. 

 

[Eaglebeak]

Wow I haven't taken mine apart yet but if that is normal play for an unpressurized lube system they don't put much emphasis on close tolerances.



That's loose!

The play that is demonstrated in the video is perfectly normal for a big end. What's important is that there is no up and down, play. If you can feel any movement vertically, it's time to replace it.

 

[Alan_B]

Turning a compressor off when it reaches set pressure is a normal part of operation. This is what compressors do. Motor torque ceases and the load soaks up the rotational momentum as the system stops. Forces and RPM are declining during this process. Stages have one way valves which are rated to hold off the output pressure, so why would this stress anything?

A lot of stress is caused if the oil detonates. Only oil properly rated for high pressure compressors should be used. Any carbon in the compressor or output air is probably from detonation and may indicate the wrong oils are in use. 

To measure input vacuum (in a meaningful way) would require blocking the input, which would add strain to the compressor's first stage, and in any case it would not see the second stage. So it seems both dangerous to the compressor and not all that useful. Instead measure the interstage pressures, that's a normal measurement on multistage compressors to judge the health of each stage.

 

[Queequeg]

To measure input vacuum would require blocking the input, which would add strain to the compressor's first stage, and in any case it would not see the second stage. So it seems both dangerous to the compressor and not useful.

Installing an inline tee with a hose barb and mechanical vacuum gauge between the air filter and the intake hole would have absolutely no effect on the performance of the compressor. Not sure if the info gained would be of much use but it certainly won't hurt anything.

 

[Alan_B]

To measure input vacuum would require blocking the input, which would add strain to the compressor's first stage, and in any case it would not see the second stage. So it seems both dangerous to the compressor and not useful.

Installing an inline tee with a hose barb and mechanical vacuum gauge between the air filter and the intake hole would have absolutely no effect on the performance of the compressor. Not sure if the info gained would be of much use but it certainly won't hurt anything.

That would not add strain to the compressor, it would primarily measure the dirt and flow restriction of the filter.

 

[Queequeg]

That would not add strain to the compressor, it would primarily measure the dirt and flow restriction of the filter.

That's right never thought of it. And a restricted filter will surely negatively effect performance.

 

[Queequeg]

Wow I haven't taken mine apart yet but if that is normal play for an unpressurized lube system they don't put much emphasis on close tolerances.



That's loose!

The play that is demonstrated in the video is perfectly normal for a big end. What's important is that there is no up and down, play. If you can feel any movement vertically, it's time to replace it.

There can't be any axial play like demonstrated without there being a significant gap between the ID of the rod end and the crank journal.



If that's what they had to do to get the design to work with aluminum on steel, so be it. I didn't expect a Daystate for the price we paid. But how much extra to use bronze bushings, which is the engineering standard. A buck?

It apparently works OK since most of the troubles people have are on the upper end.

 

[Chickenthief]

There needs to be ample room in the bottom bearing for a proper oil film.

It's the oil that does the trick not the beraing material.

Most cars and big diesels has battit (lead-tin alloy) crank bearings that is good for hundreds of thousands of miles.

If you tighten tollerances on the crank then you need to add a spiral groove in the crank (or drilled holes) or a slit in the conrod to aid oil penetration.

So a little wiggle is fine as long as there is enough oil to fill it.

 

[USAFANG6799]

Received the vacuum gauge today.

With any luck I'll have it installed to see how well my idea works.

I hope to include some pictures etc.

 

[USAFANG6799]

It apparently works OK since most of the troubles people have are on the upper end.

Given all the variables introduced by each user and operating environment the components that fail in these compressors can be pretty wide spread.

But like you indicated they are mostly in the upper end which is where my failure occurred.

 

[Chickenthief]

You're right.

Most anything execpt from carbon brakes goes for the worse at it heats up.

And the little uncooled part that heats up the most is the HP piston tip and rings.



I wonder if a water sleeve on the stainless tube from LP to HP will lower the temperature/stress on the HP piston significantly?

 

[Queequeg]

There needs to be ample room in the bottom bearing for a proper oil film.

It's the oil that does the trick not the beraing material.

Most cars and big diesels has battit (lead-tin alloy) crank bearings that is good for hundreds of thousands of miles.

If you tighten tollerances on the crank then you need to add a spiral groove in the crank (or drilled holes) or a slit in the conrod to aid oil penetration.

So a little wiggle is fine as long as there is enough oil to fill it.

If you could wiggle the rod on an IC engine that much it would fail quickly. I can't remember how many rod's I've personally installed on crankshafts, and you'll only see something that loose if it's knocking. And I've never seen a pressurized lube system that didn't have oil grooves in the crank bearings.



But it is what it is. The next time I change oil I'm going to take the cover off and see it that's what's "normal", because it's the only time I've seen that demonstrated and there other build threads on this forum in which nobody has mentioned that before. It could normal or it could be worn for whatever reason. 

 

[USAFANG6799]

Update on vacuum gauge kit: works to the point that the needle on the gauge makes an 1/8 of movement(deflection). From what I understand that means that there are no vacuum leaks in/on the YH. I won't leave it hooked up all the time for reasons I'll explain later.

Another device I hooked was a "Oxygen Flowmeter Regulator Flow Meter". You typically see them in hospitals hooked up to deliver a regulated amount of oxygen to a patient. The chrome ball in the tube offers another method/visual way to monitor the vacuum which you can set and forget on the regulator knob. Won't leave hooked up either.

Both do basically the same thing but I don't know which one is more accurate. Possibly the vacuum gauge?

I won't leave either one hooked up to monitor the YH all the time because they both restrict air intake to the YH because of the tubing,barbed connectors etc.

There is a noticeable drop in output pressure from the compressor when using either one of these devices.

I think what I'll do is every oil change I'll hook up the vacuum gauge to see if there were any changes from the last time.

 

[Queequeg]

I really think that some sort of inflow measurement is really beneficial for any compressor, especially those that operate in extremely dusty conditions. Of course I doubt that will be the case for any of ours. I'd even guess that without any restrictions the YH would fill faster. I live in the desert. Dust is a way of life here when the rains are scarce. The small filter that is provided could get clogged on a unit that is working a lot. My truck has what is essentially a vacuum gauge just past the air filter. It's a simple spring loaded piston inside a clear plastic cylinder. It shows the level of vacuum between the air filter and throttle body, indicating when to change filters. Something like this would really be useful IMO at keeping peak efficiency in any HPA, and may actually save some mechanical carnage.