20 replies to this topic

[dave]

hi fflach,

i came across this bit of calculation on

http://www.wolterpyr....com/?page=rppf

Optimum pressing pressures for rockets using whistle type mixes:

Core burner type rockets: 6500 PSI
End burner type rockets: 8800 PSI

Square inch area of most common rocket motor tooling:

½" diameter .196 square inches of area
⁵⁄₈" diameter .307 square inches of area
¾" diameter .441 square inches of area
⁷⁄₈" diameter .600 square inches of area
1" diameter .785 square inches of area
1¼" diameter 1.226 square inches of area
1½" diameter 1.766 square inches of area

Here is a sample calculation of how to find pressing pressures when you factor in the diameter of the hydraulic cylinder on your press along with the square inch area of your rocket tool using 6500 PSI as the desired pressing pressure. We will use a ¾” diameter tool set and a 1¾" diameter hydraulic cylinder in our calculation.

Example:
.441 square inches x 6500 PSI = 2866.
Divide this number by the square inch area of our cylinder:
2866 ÷ 2.405 = 1191 pounds actual gauge pressure to achieve 6500 pounds pressure on the propellant grain.

To calculate the area of a cylinder, multiply its radius by itself then multiply by 3.1416 (the old familiar πr²).

Example:
For a 1¾" diameter cylinder, the radius is 1¾ ÷ 2 or .875 inches.
.875 x .875 = .7656
.7656 x 3.1416 = 2.405 square inches.

hope that was useful

dave

[dave]

Yes it's a pretty old 2 ton I picked up on ebay for 35 pounds including postage, it cost about 40 pound to convert including the Lexan shield,
the bars are actually threaded into the cast iron base with nuts as well.

If you mean by cylindrical powder pellet something comparable to a comet with a binder, then no problem at all in your size range.

ok, decision made,

ive got a 3 ton arbor press coming tomorow,
just got to find some where nice and solid to put it and think about the modifications

any comments about thickness of lexan shield to use ?


dave

[Vic]

ok, decision made,ive got a 3 ton arbor press coming tomorow, :)just got to find some where nice and solid to put it and think about the modificationsany comments about thickness of lexan shield to use ?dave

I used four sheets of 5mm lexan bit of over kill, you would properly be fine with 15mm in total.
Here is an article on blast shield testing, it will give you more of an idea. Shield testing

[icarus]

the wonderful thing about a hydraulic press is you can put a long hydraulic hose on it and thentake the pump behind a wall whilst watching progress on a cheap cctv camera

[dr thrust]

good point icarus, and nice to see you again on the forums.
you know I'm sure ive seen a simple yet clever design used on space craft hulls where the engineers had to solve the problem of high speed particles/ dust tearing big holes in the said craft.
they came up with a twin wall system, two sheets of material with a air gap in between say for our purposes 25mm.
the high speed particle hit the first sheet smashing a hole in it but was unable to penetrate the second as it had lost all its momentum, so this what im thinking for my press redesign DR THRUST formerly chrism

Edited by dr thrust, 13 October 2010 - 10:19 PM.

[digger]

good point icarus, and nice to see you again on the forums.
you know I'm sure ive seen a simple yet clever design used on space craft hulls where the engineers had to solve the problem of high speed particles/ dust tearing big holes in the said craft.
they came up with a twin wall system, two sheets of material with a air gap in between say for our purposes 25mm.
the high speed particle hit the first sheet smashing a hole in it but was unable to penetrate the second as it had lost all its momentum, so this what im thinking for my press redesign DR THRUST formerly chrism

That is very similar to the way several types of tank armour are made. When I went to the national tank museum last year there was a cutaway of an early Russian tank armour that used this principle. It was amazing how thin each of the individual layers were, whilst still being very effective. This idea was then nicked and used on the allied tanks.