Pressurization & Lubricating oil

[Be OK]

Remember that internal combustion engines remove the carter vapors,in a enclosed stirling that is impossible so volatile gasses can explode if the compression temperature reach ignition temperature. A solution would be a "oil" that have no gasses that react without oxygen.

[Tom Booth]

... A solution would be a "oil" that have no gasses that react without oxygen.

Yes, of course. But what ?

So far, I haven't found any liquid lubricant that is completely inert. Avocado oil maybe ?

Ordinary vegetable oil (Soy bean oil) has appeared to be the least flammable so far, But of all the cooking oils refined Avocado oil is supposed to be able to take the most heat, up to 520°F but it must be "refined", But if the bottle says "High heat" it is probably refined, even if the bottle doesn't explicitly say so.

https://www.getwellseasoned.com/blogs/n ... at-cooking

I have yet to test it though. I did buy a bottle of Avocado oil marked "high heat",

Resize_20220923_171847_7743.jpg (164.33 KiB) Viewed 5253 times

So far though, I've only used it in the kitchen for stir fry, but I can say that it seems to have no tendency to smoke, even with the stove burner on the highest setting.

I have yet to take it over to the shop for the direct flame test.

[Tom Booth]

This is interesting, and coming from the FAA, one would think, authoritative.

But if "standard motor oils" were completely non-flammable, we wouldn't have any problem.

https://www.faa.gov/hazmat/packsafe/mor ... ?hazmat=52

Some of the other oils mentioned might be worth a try. Though, I've seen some cooking oil burst into flame on the stove if gotten hot enough.

Water is the most non flammable thing I can think of, but even that can become "explosive" with enough heat and pressure.

[Be OK]

I wonder if a oil can explode or even burn in a inert atmosphere that you would have in a helium pressurized stirling. No doubt there are other aspects to it.

[Tom Booth]

I wonder if a oil can explode or even burn in a inert atmosphere that you would have in a helium pressurized stirling. No doubt there are other aspects to it.

I think, avoiding any potential for explosion was what originally prompted research into using helium, so It is my understanding that helium is completely safe.

The problem is, helium can be expensive, at least more expensive than air, difficult to contain, and is sometimes very difficult to obtain, which is the situation currently.

I've tried a couple different suppliers, but due to the current shortage, it is just not available, At least not through welding gas suppliers.

For my purposes, which is to convert an internal combustion engine to external Ringbom type Stirling operation, a potential safety measure seemed to be to simply replace the crankcase oil with some liquid lubricant that is completely non-volatile.

Probably with no pressurization, or moderate pressurization, (maybe 100 psi) there would not be much, if any danger of explosion anyway, but I would like to increase the margin of safety as much as possible.

However, I'm not even sure at this point, if my Ringbom type conversion could actually work. I just don't want to blow myself up while trying to find out.

[Tom Booth]

I found this product (actually my wife suggested I try it), advertised as "non-flammable".

It does appear to be just that,as far as I can tell so far, using a propane torch.


https://youtu.be/owRUv97B3So


Let's see how it does on this model engine:


https://youtu.be/9OX19YRY9fM


Comments?

[Tom Booth]

There is also a product called "gunzilla", which is also non-flammable, which has lead me into another avenue of research.

Firearms require lubricants that have to work reliably under the most extreme conditions of heat, cold and high pressure.

Something called Slip 2000 Extreme Weapons Lube has a lot of recommendations and good reviews, but I haven't so far, been able to find any mention of it specifically being non-flammable.

Another gun lubricant called "Weapon shield" does specifically claim to be "non-flammable" on the website:

http://www.steelshieldtech.com.hk/Lubri ... hield.html

As well as claiming to be "the best weapon lubricant in the world"

https://youtu.be/lcBu6q61G3M

Anyway, I think the problem with the "Superzilla" on the power piston is probably not a failure as a lubricant so much as it increased compression beyond what this little engine was designed for.

I'm not 100% sure about that, but in turning the engine over in the attempt to get it going, there was a quite obvious increase in compression compared with running dry with just the graphite it had been dusted with out of the box.

I'm guessing that these various gun lubricants are very expensive. I haven't done any price comparisons, but it does seem that some are designed to continue working even after having gone dry, or after having been wiped relatively dry with a cloth, as demonstrated in the video.

[Tom Booth]

The MATERIAL SAFETY DATA SHEET for the Weapon Shield product states that it can burn if heated above the flash point, which is just 226°C there also seems to be some explosion danger from vapor left in an empty container.

Perhaps it could be used as a dry film in conjunction with the, apparently much less flammable Gunzilla, though, that is premature. I'm making the assumption that Gunzilla is just as non-flamable as the Superzilla.

[Tom Booth]

After spending some time trying to diagnose what's going on when a liquid lubricant is applied to the power piston, why it absolutely refuses to run, I've come to the conclusion that the problem is a timing issue.

My theory is, the improved lubrication, as well as the better air seal that results from using a liquid lube means there is a faster and stronger response from the power piston.

With a 90° "factory settings" timing advance which assumes an agonizingly slow response time compared with an IC engine with an advance of around 10°, combined with a more rapid response from the power piston, the "power stroke" wants to drive the piston before it has a chance to reach Top Dead Center.

So before the flywheel has a chance to round the bend in preparation for the power stroke, the power stroke has already started, but instead of driving the piston with the momentum of the flywheel, the flywheel is being driven backwards. The engine comes to a stop because the timing is causing the engine to work against itself.

The solution of course, If my diagnosis is right, would be to reduce the advance. Instead of 90° , try 85°. If that doesn't work, try 80°, 75°, 70°, whatever it takes, all the way down to zero if necessary, possibly even further, so the power stroke doesn't begin until just after TDC.

With such high compression, a larger power piston and larger bore could be in order, or alternatively, given the limitations of the little engine, much less heat should need to be applied.

Anyway, the adjustment should be very easy. I just need to find the right size Allan key to loosen the flywheel


https://youtu.be/KBwdKPJKGvs

[Tom Booth]

Just spent, maybe 2 hours trying every possible timing position with no change.

I took the piston out afterwards and cleaned off all the liquid lube and put it back together. It ran as well as before.

So, there goes that theory. Probably.

In taking the engine apart to clean off the "Superzilla", I did notice what seems like the unnecessarily long piston.

Resize_20221004_141742_2593.jpg (214.64 KiB) Viewed 5202 times

The piston, infact, is as long as the power cylinder:

Resize_20221004_141743_3416.jpg (162.81 KiB) Viewed 5202 times

That much surface area could certainly result in a great deal of viscous "drag".

I suppose such a long piston is necessary to form a relatively decent air seal when using graphite lubricants, but using a light oil (or whatever the stuff is) is just too much drag. Maybe.

I still wonder about the increased pressure, which seems real enough, and what effect that has, and also the throw.

The piston doesn't really seem to want to move far with the liquid lubricant. Like it wants to return sooner, and with considerable force, but again, for a relatively short distance. Like maybe it would do better with less throw. A shorter traveling distance for the piston, though I'm not sure exactly why that would be.

Possibly the "supper lube" is just not a good lubricant.

I may just try a bit of avocado oil or 3 in 1 or something before doing any radical modifications.

[Tom Booth]

The two oils were even more heavy and viscous than the Superzilla, which is almost water consistency.

Neither of the two allowed the engine to run. Again, though, the air pressure was very high, or I should say, the air seal.

The good news, I guess, is that there were no explosions. I ran another flame test on the two oils before trying them on the engine.


https://youtu.be/KOV6jQSmDGY


Each time with the oil cleaned off, except perhaps for a residual film, the engine ran fine. Maybe just as well or even better than with graphite.

Both the piston and cylinder are glass and with extremely close tolerances, maybe just too close to tolerate the addition of any oil.

[Tom Booth]

Here is an interesting statistic:

Eighty percent of the friction in a reciprocating piston engine stems from the piston rings, depending on which study your read. What’s more, The highest percentage of the drag in a given cylinder comes from the oil ring.

This little engine has no actual tight fitting rings, but in a way, the entire power piston IS one enormous tight fitting oil ring.

The same article goes on to relate the potential gain in horsepower from just using THINNER rings to reduce surface area.

“We can apply that to these older engines and get significant increases in power. It’s amazing, the difference,” he said. “You’re talking 20, 30 horsepower gains depending on ring sizes and how many cylinders it is, from the old ring packs compared these new ring packs.”

https://nasaspeed.news/tech/engine/redu ... -friction/

Comparatively speaking, the piston design of this little engine results in, I am guessing, about 40X more drag than a comparatively sized IC engine with piston rings.

I'm thinking that probably the piston could easily be shortened by 1/2 or more and all but a 1/16 in. "ring" could be ground off to provide more clearance and reduce friction further.

If this were an IC engine, such a modification, to each piston in all cylinders might realize a gain of about 1000 horse power

In other words, if a 1001 horsepower IC engine were built the same way, (big long tight fitting pistons with no rings) the drag from the pistons would reduce the power output down to a mere 1 horsepower.

[Tom Booth]

According to this chart, the Slip 2000 gun oil IS NON-FLAMMABLE

https://slip2000.com/blogs/news/how-doe ... 1e87&_ss=r

Also listed are a couple more non-flammable gun oils.

[Tom Booth]

Unfortunately, listing or advertising a lubricant as "Non-Flammable" generally only means it does not burn readily at normal room temperature and pressure.

Once I find some lubricants that are NOT obviously flammable, more testing will be necessary to see if that is still true under all conditions

Drop it on a piece of red hot metal, (like the hot end of a high temperature displacer chamber), aerosolize it, or put it under high pressure and what may be Non-Flammable under "normal" conditions could possibly become explosive.

What might be relatively safe for some things I have in mind, like to put it in the cold crankcase of a Ringbom type IC conversion engine, will not necessarily be safe in some other engine.

[skyofcolorado]

This is an engine meant to run at an internal pressure equal to (on average) to local atmospheric pressure. If you seal it tight with lube, heating it will pressurize the inside resulting in it being unable to retract the piston. It needs a pinhole somewhere so equilibrium can be established as it runs. That's my experience anyway. Maybe you tried that already, but I saw no mention of it in this thread.

Edit: Crap, I think I'm on the wrong thread. Didn't you have an engine that quit when you lubed the piston?