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-   -   B14 motor musings... (http://www.oldrocketforum.com/showthread.php?t=7425)

blackshire 07-21-2010 05:24 PM

B14 motor musings...
 
Hello All,

While I don't expect B14 motors to make a comeback, I am curious about the details of how they were produced. This could shed light on possible new B14 production.

Were their propellant grain voids drilled out manually or by some kind of automated system? In any event, this last production step was probably less dangerous than the initial propellant grain/delay charge/ejection charge pressing operation because the (initially) loose black powder involved could have set off the entire loose powder batch in the motor production building if it had ignited. A B14 that ignited during the later void drilling step would probably have affected only that particular motor and the drill.

It would seem that an automated system (especially using today's technology) could drill out B14 propellant grain voids safely. The costs of developing such a system could, of course, make the production of new B14 motors economically non-viable, especially for making small quantities of the motors. But if the production quantities were large enough (whatever that number might be), they would be worthwhile to produce.

LeeR 07-21-2010 08:04 PM

I visited Estes Industries when I was a kid (in 1966), and remember the fantastic tour, including seeing Mabel cranking out engines. I also remember someone performing an operation on motors, and believe it was drilling out B14s. It was a long time ago, so I could be wrong. But, I am not sure why they would have to be drilled. Why not an automated process that has a pin that rises up into the nozzle prior to pressing the BP, and then is extracted, leaving a core?

I still have a few Estes B14s, and quite a few Centuri B14s, so I may try one of each this summer. I loved that motor as a kid! Only one problem I ever had -- I launched a Flying Jenny biplane glider with one, and it suffered major balsa disintegration.

Doug Sams 07-21-2010 08:33 PM

Quote:
Originally Posted by LeeR
But, I am not sure why they would have to be drilled. Why not an automated process that has a pin that rises up into the nozzle prior to pressing the BP, and then is extracted, leaving a core?
I think that's essentially the B8/C5.

My take is that for the more aggressive (steep) core of the B14, if you tried to merely ram it, that you wouldn't get the powder to pack tightly around the pintle (I think that's the right term) with the result that the core wouldn't be formed properly.

Since it's a powder being rammed (and not a liquid), you don't get true hydraulic behavior so the vertical pressures in the casing during the ram are greater than the horizontal forces - there's not enough force to pack the powder tightly around the core.

Anyway, that's only my theory - I am not a motor manufacturing expert - IANAMME :)

Doug

.

tbzep 07-21-2010 08:40 PM

Quote:
Originally Posted by Doug Sams
I think that's essentially the B8/C5.

My take is that for the more aggressive (steep) core of the B14, if you tried to merely ram it, that you wouldn't get the powder to pack tightly around the pintle (I think that's the right term) with the result that the core wouldn't be formed properly.

Since it's a powder being rammed (and not a liquid), you don't get true hydraulic behavior so the vertical pressures in the casing during the ram are greater than the horizontal forces - there's not enough force to pack the powder tightly around the core.

Anyway, that's only my theory - I am not a motor manufacturing expert - IANAMME :)

Doug

.


It would also have to be a longer and more fragile pintle, and they would likely be broken or bent often.

blackshire 07-21-2010 09:05 PM

Quote:
Originally Posted by tbzep
It would also have to be a longer and more fragile pintle, and they would likely be broken or bent often.
I believe the old Teleflite book on "roll your own" black powder model rocket motors also touched upon this issue regarding core-burning motors.

From LeeR's recollection (I wish *I* could honestly wear a "I Toured the Estes Plant and Didn't Get Blown Up!" T-shirt!), it sounds like the B14 motors were manually drilled out. An automated system using a "magazine" feeder and a relatively slow drill (with a non-ferrous metal bit) could drill out B14 motors, and the leftover black powder drill "dregs" might even be reusable (if they could be safely "re-powdered" to the required mesh size) for propellant grains in other motors.

GregGleason 07-21-2010 10:03 PM

I wonder why a binder couldn't be added so that it could be held together? Or some kind of "Swiss cheese" plastic form to hold the void, while it sits upon a form-fitted metal mandrel (of a suitable material) so that the two work together as the BP is pressed into the motor, but that the plastic part stays with the motor.

Greg

stefanj 07-21-2010 10:06 PM

I really doubt the process was "manual," in the sense of a guy with a Ryobi taking careful aim down the nozzle. I'm sure there was a hopper and a jig to hold the motor in place and an automated drill, as Blackshire suggested.

Some little clues:

There's a late-60ish Model Rocket News article giving a tour of the factory. There's an overhead shot of the plant.

The accompanying text says, paraphrasing: "Series II and III motors are brought to building X for further processing."

Series II motors are B14s. Series III are shorties.

Chances are the shorties started out with normal sized casings and were cut short. Easier than making a new Mabel to accomodate the shorter casing.

blackshire 07-21-2010 10:38 PM

Quote:
Originally Posted by stefanj
I really doubt the process was "manual," in the sense of a guy with a Ryobi taking careful aim down the nozzle. I'm sure there was a hopper and a jig to hold the motor in place and an automated drill, as Blackshire suggested.
In those days, it was probably a Sears Craftsman or a Black & Decker drill... :-)
Quote:
Originally Posted by stefanj
Some little clues:

There's a late-60ish Model Rocket News article giving a tour of the factory. There's an overhead shot of the plant.

The accompanying text says, paraphrasing: "Series II and III motors are brought to building X for further processing."
Interesting...was this building as far away from the main plant as the motor production buildings? (If it was closer, that suggests that the B14 drilling step and the Series III "case chopping" step weren't considered as hazardous as motor filling operations.)
Quote:
Originally Posted by stefanj
Series II motors are B14s. Series III are shorties.

Chances are the shorties started out with normal sized casings and were cut short. Easier than making a new Mabel to accomodate the shorter casing.
I don't know one way or the other, but the statement in the article text certainly suggests that. If that was the case, what (if anything) might Estes have done with the cut-off excess lengths of motor casings? They weren't ones to waste materials. If nothing else, it would seem that 1/8" or 1/4" thick rings cut from the "waste" motor casing pieces could have been used as heavy-duty BT-20 thrust rings for high-thrust motors such as the B14.

blackshire 07-21-2010 11:00 PM

Quote:
Originally Posted by Doug Sams
I think that's essentially the B8/C5.

My take is that for the more aggressive (steep) core of the B14, if you tried to merely ram it, that you wouldn't get the powder to pack tightly around the pintle (I think that's the right term) with the result that the core wouldn't be formed properly.
Yes, that's the most common term (pintle) for it that I've encountered, although in the book "All About Rockets & Jets" by Fletcher Pratt, the section that describes and illustrates Skyrocket motor pressing calls it a "thorn."
Quote:
Originally Posted by Doug Sams
Since it's a powder being rammed (and not a liquid), you don't get true hydraulic behavior so the vertical pressures in the casing during the ram are greater than the horizontal forces - there's not enough force to pack the powder tightly around the core.
Indeed--up to a point, as long as it is tapered and not cylindrical (as was the pintle used in the B8 & C5 motors, as well as the conical thorn often used for pressing skyrocket motors), the pintle or thorn can apply sufficient vertical (bottom-to-top) pressure to the black powder grains to force them together into a solid mass when the grain is pressed.

jdbectec 07-22-2010 07:01 AM

Quote:
Originally Posted by blackshire
I believe the old Teleflite book on "roll your own" black powder model rocket motors also touched upon this issue regarding core-burning motors.

From LeeR's recollection (I wish *I* could honestly wear a "I Toured the Estes Plant and Didn't Get Blown Up!" T-shirt!), it sounds like the B14 motors were manually drilled out. An automated system using a "magazine" feeder and a relatively slow drill (with a non-ferrous metal bit) could drill out B14 motors, and the leftover black powder drill "dregs" might even be reusable (if they could be safely "re-powdered" to the required mesh size) for propellant grains in other motors.



While I can't comment directly on the B14, Lee Piester told me the old Mini'Max core burners were drilled, IIRC, using some kind of fixture and a horizontal boring machine. He also mentioned one would occasionally ignite! This prompted the move to Enerjet composite motors, much safer.

Using a pintel requires more than one ramming head, no big deal using the Teleflight methods, but not suitable for "Mable" type machines.

Terry Dean or Fred Schecter should chime in, as they are more knowledgable about this than I.

For the record, I BELIEVE, some type of binder is used in BP motors to ensure they form a good grain, something I remember from a MSDS(?) I read.

Of course I'm no expert either, and I could be wrong about all of this, I've been wrong before.


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