chucko
Veteran Member
think it would be easy to take a junk yard ac system out of a car mount to a carryall and convert it to run off the PTO? Think 540 would turn the compressor fast enough to do any good?
Any one know about car type ACs?
- Thread starter chucko
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rdbrumfield
Veteran Member
what is your application, aircompressor or conditioning
at 540 you won't get much cfm. they are made to run the speed of the car engine, from 500-6000
I used a 74 celica two piston for an aircompressor on one of my trucks. It has it's own crankcase. put a master switch in the cab and an electrical shut off on the tank to kick out the compressor when up to pressure. Be sure to put a mechanical popoff in case you have an elecrical malfunction. will make the tank a bomb.
you might put a belt to it to speed it up, I would think you would want to turn it at least 2000 rpm
at 540 you won't get much cfm. they are made to run the speed of the car engine, from 500-6000
I used a 74 celica two piston for an aircompressor on one of my trucks. It has it's own crankcase. put a master switch in the cab and an electrical shut off on the tank to kick out the compressor when up to pressure. Be sure to put a mechanical popoff in case you have an elecrical malfunction. will make the tank a bomb.
you might put a belt to it to speed it up, I would think you would want to turn it at least 2000 rpm
brandoro
Platinum Member
If you are planning to use it to cool the cab of the tractor I think 540 RPM would be adequate. The AC in the car is cooling a bigger space and only runs the compressor a few seconds at a time even at low engine RPM. You will also need a fan for the condensor, I don't think you will be able to get enough speed out of your tractor for airflow
ampsucker
Platinum Member
conditioning what?
auto a/c is sized to cool a car or truck size cabin from 140 degrees F on a hot summer day down to "comfort" in a just a few minutes. you're looking at around 15,000 btu or more at a 5-15 hp draw for that ability. this is much more than a typical window sized home unit where the requirements are not as demanding (insulated walls and ceiling, less radient heat, longer to do the job).
do you really need that much conditioning power that you are willing to run your tractor wide open to get 540 rpm?
if you just want to cool a small cab on the tractor itself, i would look into finding the smallest compressor you can find and either running it electrically from the tractor alternator or rigging up a belt direct to the engine to drive it more efficiently and faster at closer to engine rpm. for that type of application, something in the range of several thousand btus whould easily be sufficient and would consume only a horse power or two.
in fact i have a cooler in my truck that operates on a danfoss type compressor on DC 12 volt and will keep the cooler frozen for less than 35 watts continuous. you could rig up something like that more easily, i would think.
amp
auto a/c is sized to cool a car or truck size cabin from 140 degrees F on a hot summer day down to "comfort" in a just a few minutes. you're looking at around 15,000 btu or more at a 5-15 hp draw for that ability. this is much more than a typical window sized home unit where the requirements are not as demanding (insulated walls and ceiling, less radient heat, longer to do the job).
do you really need that much conditioning power that you are willing to run your tractor wide open to get 540 rpm?
if you just want to cool a small cab on the tractor itself, i would look into finding the smallest compressor you can find and either running it electrically from the tractor alternator or rigging up a belt direct to the engine to drive it more efficiently and faster at closer to engine rpm. for that type of application, something in the range of several thousand btus whould easily be sufficient and would consume only a horse power or two.
in fact i have a cooler in my truck that operates on a danfoss type compressor on DC 12 volt and will keep the cooler frozen for less than 35 watts continuous. you could rig up something like that more easily, i would think.
amp
madpogue
Silver Member
Actually, a car's A/C compressor turns significantly faster than the engine, since its pulley is usually smaller than the crankshaft pulley. 540 RPM would be equivalent to a crankshaft speed of about 300-350. Of course, you could employ the same trick; use pair of differently-sized pulleys to raise the RPM.
And most modern A/C compressors don't cycle on and off, but operate at "variable displacement", meaning a valve opens and closes variable to move a fraction of what the compressor is actually capable of pumping. But it's not a small fraction, so even if you could get the compressor to turn at, say, 1000 RPM, I don't think you're gonna get a lot of output.
There are multiple other challenges. Where do you put the dryer? Or whatever they call the part that sits in front of the radiator of the car? It's usually pretty big, about the same area as the radiator. Air has to pass through it pretty quickly; that's why the car's cooling fan is programmed to turn on whenever the A/C is running.
The BIG challenge, though, is that the A/C is usually integrated in to the car's powertrain control module (the engine computer). "Weaning" it from the PCM, to run on some mechanical control, would be a project.
One thing I've seen -- I am NOT making this up -- some folks with old beater cars have come up with "ghetto" A/C units using -- don't laugh -- Igloo-type coolers full of ice or those gel ice packs, and fans. You cut an opening in the lid of the cooler and mount one or two of those 12VDC fans like you see in desktop computers (they make bigger ones, too), and wire it to the car's electrical system. I know this sounds totally "you might be a redneck if....", but it's been done, and apparently it's pretty effective.
And most modern A/C compressors don't cycle on and off, but operate at "variable displacement", meaning a valve opens and closes variable to move a fraction of what the compressor is actually capable of pumping. But it's not a small fraction, so even if you could get the compressor to turn at, say, 1000 RPM, I don't think you're gonna get a lot of output.
There are multiple other challenges. Where do you put the dryer? Or whatever they call the part that sits in front of the radiator of the car? It's usually pretty big, about the same area as the radiator. Air has to pass through it pretty quickly; that's why the car's cooling fan is programmed to turn on whenever the A/C is running.
The BIG challenge, though, is that the A/C is usually integrated in to the car's powertrain control module (the engine computer). "Weaning" it from the PCM, to run on some mechanical control, would be a project.
One thing I've seen -- I am NOT making this up -- some folks with old beater cars have come up with "ghetto" A/C units using -- don't laugh -- Igloo-type coolers full of ice or those gel ice packs, and fans. You cut an opening in the lid of the cooler and mount one or two of those 12VDC fans like you see in desktop computers (they make bigger ones, too), and wire it to the car's electrical system. I know this sounds totally "you might be a redneck if....", but it's been done, and apparently it's pretty effective.
ampsucker
Platinum Member
blowing warm air over cold ice is a variation of a swamp cooler which blows warm air over water which cools as it evaporates. these types of systems work best in extremely dry climates where the relative humidity is very very low (think desert). in a humid environment, a large percentage of the perceived cooling (latent cooling) is done by drying the air relative to the ambient humidity. swamp coolers (and melting ice without a heat exchanger) beside being a very inefficient way to cool the air do nothing in helping lower the relative humidty and can actually worsen the problem by adding even more moisture to the air.
yes, it's pretty ghetto! ;-)
i would rather use a cool bandana tied around my neck then have to rig something like that up.
the "dryer" you are referring to is actually the condensor where the heat taken out by the a/c is blown up to the environment. there is a dryer component to, but it is a canister.
as mentioned in previous post, there are better (easier) and more efficient ways to do this. if nothing else, a self contained package or small window unit designed to run on DC, like the kind they use in small campers, would be a much easier install and the efficiency rating would be exponentially higher since all the engineering is already done for you.
amp
yes, it's pretty ghetto! ;-)
i would rather use a cool bandana tied around my neck then have to rig something like that up.
the "dryer" you are referring to is actually the condensor where the heat taken out by the a/c is blown up to the environment. there is a dryer component to, but it is a canister.
as mentioned in previous post, there are better (easier) and more efficient ways to do this. if nothing else, a self contained package or small window unit designed to run on DC, like the kind they use in small campers, would be a much easier install and the efficiency rating would be exponentially higher since all the engineering is already done for you.
amp
Bill Barrett
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A/C's were the car that the Cobra was made from.
sandman2234
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I studied a little bit of A/C in school back in the mid 70's for automobiles and a little more for house types in the 80's.
From what I know, running it off the pto is possible but something to consider about using a "junkyard system" is the concern that the system has been sitting open for X amount of time, possibly being damaged in an accident. Any leakage will allow the system to discharge and when it is empty, the system then pulls in air, which contains moisture. The moisture is the systems worse enemy and even if you catch the car right after it hits the yard, the moisture still has to be removed. The way to do this is to pull a vacumun on the system and hold it for extended periods of time. Worse case you may need to hold a vacumun on it for up to 24 hours. As far as running it off the pto, my question is why? Seems mounting a small compressor on a bracket and running it off the engine to get the added speed required for a compressor would be less trouble than having to mount a pulley on the pto and running fan belts to speed it up to compressor speeds. What happens when you need to run a bush hog or other pto attachment, and it is 95 degrees outside? Just removing the compressor by swinging it out of the way is a pain, but still doable.
David from jax
From what I know, running it off the pto is possible but something to consider about using a "junkyard system" is the concern that the system has been sitting open for X amount of time, possibly being damaged in an accident. Any leakage will allow the system to discharge and when it is empty, the system then pulls in air, which contains moisture. The moisture is the systems worse enemy and even if you catch the car right after it hits the yard, the moisture still has to be removed. The way to do this is to pull a vacumun on the system and hold it for extended periods of time. Worse case you may need to hold a vacumun on it for up to 24 hours. As far as running it off the pto, my question is why? Seems mounting a small compressor on a bracket and running it off the engine to get the added speed required for a compressor would be less trouble than having to mount a pulley on the pto and running fan belts to speed it up to compressor speeds. What happens when you need to run a bush hog or other pto attachment, and it is 95 degrees outside? Just removing the compressor by swinging it out of the way is a pain, but still doable.
David from jax
