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Posted: Sat May 28, 2011 10:00 am
by Alster370
yes you would. The pumps that people build here tend to be like elongated shock pumps as they usually have the same small diameter.
Posted: Sat May 28, 2011 10:16 am
by inonickname
Alster370 wrote:yes you would. The pumps that people build here tend to be like elongated shock pumps as they usually have the same small diameter.
They can be considerably larger bored than shock pumps actually. With a shock pump you're relying on strength in your arm/back muscles. With a stirrup pump you have the mass of your entire body, so you can have a much larger bore and stroke.
Posted: Sat May 28, 2011 10:27 am
by Alster370
Well for my beto shock pump , I dont see how anyone can put ~180lb of force onto that handle with one arm to get it to 400psi. Its just not practical.
It should be at least half of the size its at (So from ~12mm to 6mm) then only ~90lb would be required to reach 400psi, which is capable by pretty much anyone.
Posted: Sat May 28, 2011 11:27 am
by Technician1002
I used search to find a nice example of a member built 2 stage pump.
They have a nice annimation showing how it works.
The thread is here. This is about the best resource on manual 2 stage pumps on Spudfiles. I think someone should take that information and make a Wiki page from it.
http://www.spudfiles.com/forums/high-pr ... 18170.html
From the piston diameters given the first stage has about 5X the displacement of the second stage.
Posted: Sat May 28, 2011 11:38 am
by Alster370
Thanks for the link, the pumps great and just what I was looking for. If I wanted a 3 stage pump using this design, could you just add a third chamber with a smaller diameter that is connected to the 2nd?(And the check valve would be at the bottom of the third chamber)
Posted: Sat May 28, 2011 12:07 pm
by ramses
Yes. Then you would compress the first and third stages on the down push, and the second on the "up". Keep in mind that this will require quite a lot of force.
Posted: Sat May 28, 2011 4:11 pm
by saefroch
Alster: Doesn't matter.- That was to something on the last page. Fail. Yes, you could have a three-stage pump. That's how some PCP pumps are designed.
wyz: Correct.
Posted: Sun May 29, 2011 5:31 am
by wyz2285
saefroch wrote:wyz: Correct.
Yeah
Posted: Sun May 29, 2011 8:56 pm
by ramses
The same pressure would require the same force on the handle, but the you would get more air out because of the longer stroke. The pump would be more efficient because it would have a higher compression ratio as long as your dead volume remained the same.
You could get to a higher pressure with the longer pump before you started just compressing air into the dead volume, but it would require more force on the handle.