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Hydraulic anti foam additives

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Hettric
Join Date: Mar 2004
Posts: 133 MA
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2010-10-13          174547

I am involved with a team that has a hydraulically powered catapult for "Punkin Chunkin". The questions we have -
Is there a anti foam additive we can add to the fluid?
Can we thin (cut)the oil viscosity with something? the oil we have is a mix of 10 weight and 15 weight. Other than the pump, used for a few minutes to build up to 2800psi, there is nothing to worry about damaging. We use less than 2 gallons for a shot.
Thanks


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Hydraulic anti foam additives

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2010-10-13          174564

Hettric,

Yes, anti-foam is widely available, any good hydraulics shop should have it.

Again, yes you can thin the fluid, but I fail to see what advantage that might give you. You should be using an accumulator to build a reserve of pressure, a pump is a poor choice for sudden bursts of big power.

If it was me, I'd be looking at using a tiny hydraulic system to pressurize a big pressure accumulator. Then just release the pressure to fire.

From a purely engineering point of view however, I think you will have problems with getting sufficient flow, at high enough pressures, to do what you want. Air is a better choice for a lot of reasons.


Best of luck. ....

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Hettric
Join Date: Mar 2004
Posts: 133 MA
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2010-10-13          174569

"If it was me, I'd be looking at using a tiny hydraulic system to pressurize a big pressure accumulator. Then just release the pressure to fire"

Thanks Murf, just how it works.
What can we use to cut the oil? Kerosene? ....

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2010-10-14          174578

The problem with using anything other than straight hydraulic fluid is that you run the very real risk of having seals disintegrate, or at the very least be affected enough they won't hold pressure.

IMHO you should try draining the entire system and refilling it with straight AW10 fluid.

Some people advocate using something like Dexron II transmission fluid, and while it certainly is chock full of anti-foaming additives, etc., it's also only at it's minimum viscosity of ~7.1 at about 100° C. (212° F.), at temperatures still as high as 40° C. (104° F.) it still has a viscosity of about 37.

Again, IMHO, if AW10 still isn't thin enough, then you have a design problem or other system issue that needs addressing.

What is the problem you're trying to solve in all of this?


Best of luck. ....

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Hydraulic anti foam additives

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Hettric
Join Date: Mar 2004
Posts: 133 MA
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2010-10-14          174581

Thanks again, We are just trying to get the max out of what we have. This effort is all self financed so major redesigns are out of the question at this point. The machine has evolved over 12 years, many things have been learned indicating some areas are certainly not the best they can be, but as I said, we have to work with what we got. 10 weight sounds like the best oil, but last year I was unsuccessful finding it in 5 gals at a reasonable price.
We get some air/foam hence the anti-foam question. ....

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
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2010-10-14          174582

There's no reason to do a 'major redesign' at all.

But air entrainment is a sign of a problem, and one that is usually a simple one to fix. There is almost always going to be air in hydraulic oil, especially when it's in motion in a system, but there's lots that can be done to minimize it.

The first thing is to limit the rapid depressurization of the fluid. Things like a cylinder moving unequally, that is way more pressure on one side than the other, can cause air to literally be sucked into the fluid.

The next is to be sure you have a big enough reservoir. An old propane tank makes a good one for almost nothing. The longer the fluid rests, the more air comes out of it.

Others include avoiding sudden plumbing size changes, limiting bends, valves, etc.

There's a long list of information out there on the 'net for free, make a list and have at it.


Best of luck. ....

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Hettric
Join Date: Mar 2004
Posts: 133 MA
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2010-10-14          174584

Quote:
Originally Posted by Murf | view 174582
[QUOTE=Murf;174582] avoiding sudden plumbing size changes, limiting bends, valves, etc.

Yep, we got all of them - even "tees" not sure what they were thinking back then. As for "rapid pressurization" I'll let you decide-------
http://vids.myspace.com/index.cfm?fuseaction=vids.individual&VideoID=3559893 ....

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Murf
Join Date: Dec 1999
Posts: 7249 Toronto Area, Ontario, Canada
TractorPoint Premium Member -- 5 Tractors = Very Frequent Poster  View my Photos  Pics

2010-10-15          174596

It's pretty hard to see anything of the system in that video.

The tower does give me one idea though. Try using a piece of pipe, fairly tall but smallish in diameter. For instance, a 6" diameter pipe, 60" tall holds ~15 gallons. If you have the outlet at the bottom, and the return at the top, it will do a lot to reducing both the heat (lots of surface area) and the air (lots of oil at the bottom, with air rising).

Best of luck. ....

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