Czx7 Posted August 24 Posted August 24 I have pressed a few whistle motors with my woodys cohete tooling and I decided to go with 6000psi. Do you guys have any other recommendations.
DavidF Posted August 25 Posted August 25 Did you fly them? What size? I'm assuming you used benzoate propellant rather than sali? Increment size? Do the outsides look smooth rather than wrinkled? There's not much anybody can say without more info. Most folks press whistles at a higher pressure, more like 7500psi or more. The only thing I'd suggest to you is to make sure they are working correctly before you make a whole bunch of them. And know, it's possible for whistle rockets to CATO when they are stored for a while. Quite a few pyros have complained of this.
Czx7 Posted August 25 Author Posted August 25 (edited) Thanks for the info. I have only made around 2. For the increment size I have been doing a half of teaspoon to a teaspoon (Im working on a more accurate way of doing it ). Yeah, I am using benzoate fuel. The motors look good I am assuming because of the use of a tube support. For the size of the tube its woodys cohete tubes that are 5/8 id and 4in long. Im not planning on storing them to be honest. I tested them and they flew ok. I am going to take you advice to press a little harder to 7500psi. My main question is that with a smaller tube like the cohete tubes do I need to use more or less force? Edited August 25 by Czx7
DavidF Posted August 25 Posted August 25 You mentioned using Woodys PtoF gauge. Just to clarify, for 6000psi your gauge would read 1840 pounds, and for 7500psi on that size motor your gauge would read 2300 pounds. The psi of loading pressure doesn't change with the tube size, but the force applied does. As the square inches of surface area being pressed increases, the force being applied must also be increased. Your 5/8" motor has a surface area of .307 square inches. .307 X 7500= 2302.5 (round to 2300) pounds. A 3/4"motor has a surface area of .441 square inches. To press it to 7500psi your PtoF gauge would read .441 X 7500= 3307.5 (round to 3300) pounds. I hope this answers your question. Your whistle propellant might not be ideal if they only 'flew OK'. On that spindle they should be pretty zippy. The benzoate needs to be really fine for them to fly fast and whistle loudly. If your motors look nice and smooth, I assume your tube support is a nice snug fit on the tube. If the tube has wrinkles on the outside, it may be a bit loose in the support, or the increments could be a bit too large.
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