NFPA Meeting: Limited-Use Reloadables, Tribrids

[Jerry Irvine]

Originally posted by garoq
We reduced the diameter of the cases so there should be no problem fitting them in motor mount tubes,

What is the new labelless OD?

 

[Garoq]

Originally posted by Jerry Irvine
What is the new labelless OD?

The case O.D. was reduced from 1.130" to 1.125". It was enough to make a difference.

 

[BlueNinja]

Sky Ripper's "change case length to change impulse" idea comes to mind....

If you were to make a screw-in nozzle mold, would it be possible to sell different nozzle sizes with one universal grain? Seems if that was possible you could have several different motors in one case.

 

[shreadvector]

let me guess at a few things.

1) 30 grams is the mailable limit, so motors will always exist below the 80 N-s F limit just so they are mailable.

2) Changing nozzles with the same grain might make a motor go "POP" (smaller throat) or "Pfffft..." (larger throat). I'm sure the experts will correct me.

3) Longer casing would be the G casing.

Originally posted by Blue_Ninja_150
Sky Ripper's "change case length to change impulse" idea comes to mind....

If you were to make a screw-in nozzle mold, would it be possible to sell different nozzle sizes with one universal grain? Seems if that was possible you could have several different motors in one case.

 

[powderburner]

Originally posted by BobCox
Gary,
This sounds like a great idea, especially if you can do the package with 3 loads + a casing good for up to 5 firings as others have described.
I currently do not fly reloadables because of the expense of the motor hardware and the risk of losing them during flight. The other reason I don't do reloads is all the putzing required to assemble and clean the hardware between flights. A new system like you are proposing would be very appealing to me.
As others have pointed out, I hope you keep the grain weight low enough that they can be shipped without HazMat charges.

I agree with BobCox and with a whole bunch of the rest of these guys, this sounds like a great idea.

Most of the reason I quit using composites (even before the big fire) was that they were getting too expensive. I sure don't want to spend a bunch of bucks on RMS hardware (at the rate that MY rockets get lost). This idea would make it a lot more attractive to guys like me to step up to mid-power again.

 

[Art Upton]

Originally posted by garoq
The price estimate was for three F20W equivalents. But the cost savings as a percentage should be similar for the other motors.

This is a great idea to save money both for the rocketeer and save you labor costs and time. good thinking.

But, what if I had a couble of F20-4s. and I wanted to refill them ?

the only differance is a glue line at the top ?

if future SU loads also could be used as LU it might make some buy single or dual reload kits after they got tired of seeing the burned out cases on their shelf.

but heck, I have burned out AT cases from the 80s still on a shelf, why I don't know.

I did try the open it up thingy today on an F20-4 and forgot about the glue line ;-0

 

[Garoq]

Originally posted by Art Upton
This is a great idea to save money both for the rocketeer and save you labor costs and time. good thinking.

But, what if I had a couble of F20-4s. and I wanted to refill them ?

the only differance is a glue line at the top ?

if future SU loads also could be used as LU it might make some buy single or dual reload kits after they got tired of seeing the burned out cases on their shelf.

but heck, I have burned out AT cases from the 80s still on a shelf, why I don't know.

I did try the open it up thingy today on an F20-4 and forgot about the glue line ;-0

The epoxy seeps down into the threads and makes the forward closure impossible to remove without destroying it.

 

[Garoq]

Originally posted by Blue_Ninja_150
Sky Ripper's "change case length to change impulse" idea comes to mind....

If you were to make a screw-in nozzle mold, would it be possible to sell different nozzle sizes with one universal grain? Seems if that was possible you could have several different motors in one case.

Not likely. Due to the limited strength of the casing, there is a relatively narrow range of pressure that these motors can operate in.

 

[Garoq]

Originally posted by shreadvector
let me guess at a few things.

1) 30 grams is the mailable limit, so motors will always exist below the 80 N-s F limit just so they are mailable.

2) Changing nozzles with the same grain might make a motor go "POP" (smaller throat) or "Pfffft..." (larger throat). I'm sure the experts will correct me.

3) Longer casing would be the G casing.

Mailability is preferred, but not required.

You are correct about the nozzles.

There are three casings so far: a 29/60, 29/80 and a 29/100-110.