Getting my pump!!!

[Pellethuntr]

Thought I would update you guys again...I have hit a minor setback...with all the parts I need it's gona cost me quite a bit more money...and I kinda drained all my extra funds on the pump, and im trying to get another predator rifle before the seasons over...sooo in short it's gona be a little while before I get back to this project

[Forum Admin]

Man, sorry it has been such a hassle to get that pump going. I'm hoping in a few days I will have a fridge compressor to play with. I'm even thinking of getting two, possibly feeding the output of one to the input of the other. In theory I should be able to achieve between 800 and 1000 psi with such a setup.

[Pellethuntr]

cool...I always wanted to try a fridge pump...keeps us posted Geo

[BoyntonStu]

Man, sorry it has been such a hassle to get that pump going. I'm hoping in a few days I will have a fridge compressor to play with. I'm even thinking of getting two, possibly feeding the output of one to the input of the other. In theory I should be able to achieve between 800 and 1000 psi with such a setup.

I am getting 550 psi with a single 8,000 BTU window A/C compressor.

At 600 PSI it overheats.

[Forum Admin]

Here's what I am wondering - Your compressor gets 550 psi relative to standard air pressure. If you increase the air pressure fed to it, could it still achieve a 550 psi pressure difference? For example, have two fridge compressors with a small tank (old CO2 cylinder) between them. Fill the tank to 550 psi, allow the first compressor to cool back down, then switch both on with the secondary taking its input from the small tank, the primary maintaining the tank pressure around 550 psi. With pressure and efficiency losses, 800 to 1000 psi should be possible. Of course, I have to keep the overall cost below $250 assuming this works. If it goes beyond that, I might as well buy a hand pump and all the fittings and be able to achieve 3000 psi. Let me know your thoughts, there is an abundance of used compressors to be had on the cheap right now.

[FighterAce]

If I had to choose between a pump and a compressor I'd go with the pump no matter what the price.
Nothing can beat its mobility and independence. What will you do if the power goes out or battery dies?
Implement mouth to... quick release? 

[Forum Admin]

I agree with the pump for mobility, but I can build the compressor setup pretty cheap if I buy a couple used refrigerators (I found two minis for $40 the other day  ). My hope is to be able to fill a couple old CO2 cylinders to 800 psi and use it to quickly fill my airgun to 400 psi in the field. Should last for five or six shots before the pressure drops below 400 psi. Then you can use the shock pump to take it to 400 psi with fewer strokes if you needed more shots. On my current airgun I've been working on, it takes about 50 strokes for 100 psi gain. 200 strokes to 400 psi. Gets a bit tiresome! lol

[FighterAce]

Well that sounds cool. All you need is a bunch of CO2 cylinders on your back. its gonna look like a flamethrower I tell ya... all you need is that hose to connect all those cylinders to the gun 

I was thinking about carrying my old pump and the shock pump at the same time. With the old one I can bring it up to around 180psi and then continue with the shock pump to 400 psi. It takes less then 5 strokes to get it up to 180, it shouldnt take more then 100 strokes with the shock pump to get it to 400 psi.
Whats the size of that airtank? 50 strokes for 100 psi sounds a lot....

btw. how heavy is one of those CO2 cylinders? I hope its not gonna feel like you're carrying a house on your back 

[Forum Admin]

Yeah, that is a good idea about using two pumps. That is actually how they used to do it back in the Lewis and Clark days. Now we have multistage pumps that do three stages in one stroke, but they are pretty expensive. The CO2 cylinders are light, they are made of aluminum and are about 12 inches tall and 4 inches wide. I've got two of those and a couple of smaller ones as well. The two bigger ones fit nicely in my backpack and you can carry them for hours without noticing them.

[Pellethuntr]

Sounds awesome Geo!!!

[BoyntonStu]

I agree with the pump for mobility, but I can build the compressor setup pretty cheap if I buy a couple used refrigerators (I found two minis for $40 the other day  ). My hope is to be able to fill a couple old CO2 cylinders to 800 psi and use it to quickly fill my airgun to 400 psi in the field. Should last for five or six shots before the pressure drops below 400 psi. Then you can use the shock pump to take it to 400 psi with fewer strokes if you needed more shots. On my current airgun I've been working on, it takes about 50 strokes for 100 psi gain. 200 strokes to 400 psi. Gets a bit tiresome! lol

From Technician at Spudfiles.

DANGER
What is the maximum inlet pressure on your compressor? Unless the inlet is pressure rated, that is a good way to blow crankcases apart and in the case of fridge compressors have the shell explode. Since the type of compressor wasn't listed, I'll mention that refrigerator compressor shells (the inlet side pressure) can fail at pressures over 300 PSI. Use a pressure relief of no more than 200 PSI on the inlet of a cascaded refrigerator compressor.

[Forum Admin]

Thanks a 200 psi increase would be better than nothing i guess. I'll have to check the inlet pressure on mine. If i recall right it is 150 psi

[BoyntonStu]

Thanks a 200 psi increase would be better than nothing i guess. I'll have to check the inlet pressure on mine. If i recall right it is 150 psi

Be careful.

I believe that 750 - 850 is doable with 2 pumps in cascade.

[Forum Admin]

I think so too, that's close enough to the pressure I'd like to achieve for filling my cylinders.