boyntonstu wrote:I finished building my new hand pump .and she work nice

the highest pressure i get from this pump is 700 psi

the cylinder is 20.7mm in diameter

Nice work.

A question about 20.7 mm and 700 psi.

20.7 mm is about 0.8" and that works out to about 0.5 sq in.

To get 700 psi out of 0.5 sq in you need to apply 350 pounds of force.

How do you apply 350 pounds of force?

How many cu in are in your chamber and how many pumps does it take to fill it?

I am following in your footsteps and I want to get it right.

BoyntonStu

Well done.. Double checked the math. Got the same answer. about .5 sq in.. So how do you get 700 PSI?