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Help me pimp my compressor

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: boyntonstu » Thu Apr 22, 2010 7:30 am

MrCrowley wrote:All the fans I have seemed to found running on commercial fridges are condenser fans, which are sort of useless for us, as this isn't a closed circuit, running cold whatever through the compressor will probably be tricky and/or expensive. I'm beginning to understand what Stu has been saying but I still have seen results using fans on my compressor without fins or coolant.


Try pressurizing the input and watch the temperature fall even more than by using a fan .

By Golly you're getting it!
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Unread postAuthor: POLAND_SPUD » Thu Apr 22, 2010 8:39 am

I am testing this thing at the moment... ohh I am afraid I won't be able to measure temperature without a fan as:
1. I don't feel like removing it
2. I don't think I have a thermometer that goes that high

it has been already running for over an hour... I'll update it once it's done

UPDATE!!
ambient temperature was 30 deg C (I keep it in a greenhouse Duhh :) )

The compressor was on for ~1.5 hour... the temperature of the casing was 52 deg Celsius

not bad but it was much warmer than usually... something tells me it isn't the best idea to keep it in a greenhouse


ohh BTW I have several kilos of copper strips... in case you don't know what I am talking about -> http://www.indiamart.com/pushpatrading/ ... erial.html

any idea if it's possible to solder it to the casing ?

ohh and finally...
boyntonstu suggested pressurising the input... it works due to the fact that air experiences compression heating in the first stage and dissipates heat through the first stage compressor and the air reservoir... thus the second stage has less heat to deal with

you can read about it here -> http://www.domnickhunter.com/technicalcentre/3.3.1


If the compressor was designed to be fan cooled in an enclosure, it will come with a fan and/or an oil cooler coil

heh what you failed to notice is the fact that fridge compressors are designed to pump refrigerant in a closed circuit, which is not the same as compressing ambient air...

How come you acknowledge that there is a thing called compression heating when you talk about pressurising air input but you claim that pumping refrigerant is the same thing as compressing ambient air?
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Unread postAuthor: MrCrowley » Thu Apr 22, 2010 5:00 pm

So about this pressurizing the input thing. I assume a constant air supply is required for the input, how demanding do you think the supply needs to be? My fridge compressor would never be portable so I may as well hook the input up to my proper 21litre air compressor. I wouldn't have guessed that it'd be a better way of cooling it.

Who else has noticed that members topics about their own fridge compressors always turn in to a forum discussion about fridge compressors? :P
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Unread postAuthor: POLAND_SPUD » Thu Apr 22, 2010 5:20 pm

it will work... but it will work better when air has more time to cool...

I wouldn't say that it is 'proper' cooling method... It's probably fills X litre chamber to Y pressure in less time and it gets less hot in the process... but I am not sure whether it gets hot faster when compared with a single stage setup

always turn in to a forum discussion about fridge compressors? Razz
lol that's the second rule of fridge compressor club.. and you've already violated rule no 1
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Unread postAuthor: boyntonstu » Thu Apr 22, 2010 5:22 pm

MrCrowley wrote:So about this pressurizing the input thing. I assume a constant air supply is required for the input, how demanding do you think the supply needs to be? My fridge compressor would never be portable so I may as well hook the input up to my proper 21litre air compressor. I wouldn't have guessed that it'd be a better way of cooling it.

Who else has noticed that members topics about their own fridge compressors always turn in to a forum discussion about fridge compressors? :P


I agree.


I didn't invent the idea, I copied it, and I was pleasantly surprised at the cooling benefit.

BTW Not only is a pressure assisted a/c compressor working easier, it works faster and therefore the duty cycle is reduced.

Remember this?

[youtube]http://www.youtube.com/watch?v=nR4lybUETqI&
playnext_from=TL&videos=wGV2T_8Xw6E[/youtube]

And mine:
Pressure Assisted A/C Compressor for Air Rifle

[youtube]http://www.youtube.com/watch?v=i1lhv18oXZk&NR=1[/youtube]


P.S. Why air condition a car at highway speed with all that air coming across the roof cooling it? The wind at 60 mph is equivalent to a huge fan.
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Unread postAuthor: POLAND_SPUD » Thu Apr 22, 2010 5:34 pm

P.S. Why air condition a car at highway speed with all that air coming across the roof cooling it? The wind at 60 mph is equivalent to a huge fan.
this really isn't the best example... if you want to see air cooling at work try riding a motorbike at 60MPH... in a t-shirt... when air temperature is no higher than 20 deg C :D
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Unread postAuthor: c11man » Thu Apr 22, 2010 9:37 pm

stu. pressurizing the input does reduce the duty cycle and the filling time but by NO means does it make the compressor run easir. it makes it pump much harder due to the fact that there is more air in the pump at the begining of a cycle so the force required to compress more volume is of course this makes it harder to compresses.

a compressor with a running for 15min with a pressurized input will be much hoter than a compressor running for 15min with a ambient air input
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Unread postAuthor: spudamine » Fri Apr 23, 2010 12:33 am

P.S. Why air condition a car at highway speed with all that air coming across the roof cooling it? The wind at 60 mph is equivalent to a huge fan


The idea with AC is to lower the temperature below ambient, which is impossible with passive cooling.

a compressor with a running for 15min with a pressurized input will be much hoter than a compressor running for 15min with a ambient air input


looks like round 2 is brewing :lol: I suspect you're right, although you wouldn't have to run the second setup for as long to reach the same pressure so both setups probably work out the same.
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Unread postAuthor: boyntonstu » Fri Apr 23, 2010 8:24 am

c11man wrote:stu. pressurizing the input does reduce the duty cycle and the filling time but by NO means does it make the compressor run easir. it makes it pump much harder due to the fact that there is more air in the pump at the begining of a cycle so the force required to compress more volume is of course this makes it harder to compresses.

a compressor with a running for 15min with a pressurized input will be much hoter than a compressor running for 15min with a ambient air input


Do you believe your eyes and your ears?

Do you trust real world data more or less than theory?

Watch and listen to this video again.

[youtube]http://www.youtube.com/watch?v=nR4lybUETqI&
playnext_from=TL&videos=wGV2T_8Xw6E[/youtube]

Do you hear the compressor with pressurized input?

Do you hear the compressor without pressurized input?

If you hear it, is it working easier or harder?

Did the compressor fill the chamber faster or slower with pressurization?

I believe in data more than theory or assumptions.
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Unread postAuthor: POLAND_SPUD » Fri Apr 23, 2010 8:39 am

yeah that's cool... but couldn't you make a video that shows how much time it takes to pump X litre tank to Y bars with and without input pressure ?

let say, 2 L tank to 500 psi ?
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Unread postAuthor: Crna Legija » Fri Apr 23, 2010 10:06 am

with 100 psi input it 1/4th the time for my 1l tank
thats too 300psi
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Unread postAuthor: POLAND_SPUD » Fri Apr 23, 2010 10:11 am

yeah but the point is to film it so that we can refer to it later.... I am still not quite sure how it works myslef and whether it puts more strain on the motor or not...

so it would be good to have it filmed... sadly I don't have a shop compressor
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Unread postAuthor: Crna Legija » Fri Apr 23, 2010 10:19 am

i think it make the motor work harder cos at 130psi input my motor wont even start to compress, i have a mini bar frigde compressor tho

i would love to make a vid of it but i have no camcorder
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Unread postAuthor: boyntonstu » Fri Apr 23, 2010 10:24 am

-_- wrote:i think it make the motor work harder cos at 130psi input my motor wont even start to compress, i have a mini bar frigde compressor tho

i would love to make a vid of it but i have no camcorder


You are confusing not starting with working harder.

If it starts, it will work easier and quieter.

If you over pressurize the input, it won't start.
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Unread postAuthor: spudamine » Mon Apr 26, 2010 2:20 pm

Back on topic (briefly), after a few days holiday I got back today and finally started the thing up and got it pumping. flow doesn't seem to be as bad as what I was expecting and it goes straight upto 600psi :D After 600 however it slows down ans stalls out, quickly followed by the thermal shutdown activating.
I think this might be because I'm pumping up only a very small volume, or it might be that's all I'm going to get. There's also quite a strong smell of burning.
I may of slipped up a bit, this is a brand new compressor, I think i've done the equivalent of buying a new car and hammering it on it's first drive :D

As for the heating, temp went up about 15C after about 10 minutes and still rising so I'll see what the fans can do tomorrow 8)
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