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.

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.

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

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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.

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

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.

In those days, it was probably a Sears Craftsman or a Black & Decker drill... :-)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.)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.

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."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.

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.

Yes, the manual hand-rammed methods in the Teleflite book could be rather involved. I was put off trying them by the first step given in the book, which was the construction of a steel plate "explosion shield."

Sugar rockets aren't quite as hazardous to make as black powder motors, and they lend themselves to core-burner grains. (It's really a necessity with sugar motors due to the propellant's lower specific impulse.)

The sulfur in the BP acts as a binder, but the MSDS I found with a case of motors indicated that a small amount of dextrin was added which would also be a binder

I have also been wrong in the past - once in 1973 and again in 1994!

We do have an expert on the subject that has firsthand knowledge on making Estes engines that is a regular here on YORF. Maybe one day he'll speak up and shed some light on our many motor questions. ;) (Note I used engine and motor in the same paragraph. heh)

Anyhow, he may also have signed some agreeement when he retired that does not allow him to speak about the manufacturing process for all I know.

Yes, I believe it was dextrin, I can't seem to find the pdf I had of that. A Google search shows that it is used as a binder in pyrotechnics.

The blast shield did discourage me from trying it my attached Garage!

Not that I could think of anyway to do it safely, other than the way it's done by manufacturers.

There is a thread or threads here on YORF in which we all contributed real or perceived manufacturing methods for the original original b16-b3-b14 and the later variations of the B14 to B8 transition, along with historical info and pics.


What follows is from memory and email conversations but the "O-O" b16-b3-b14 was actually just a B4 which has a wider core than a B6 that then had an approx. .25-.375 length cylinder shaped smaller core in it. If you look at the old Estes catalogs you will see pics of elongated cores running 3/4 "of the way up the grain; this was misinformation primarily to fool potential rival companies from copying Estes trade secrets.

So the "O-O" B14 started our life on a Mabel as a B4 and was then drilled by a machine designed invented by Vern Estes. I'm not at liberty to go into the exacting details of the size and type of drill used,etc. Let's just say it wasn't simply just a twist drill. Vern did numerous tests varying drill bit types and rpm's to get the "sweet spot"....

So the "O-O" b14 was a semi-automated 2 step process.....


This 2 step process resulted in periodic explosive events so later B14's that evolved into the B8's later were all made from fully formed mandrels in Mabels.

I think "O-O" B14 could probably be made to day fully automated, using a combo cylinder-coned shaped mandrel, but if that was true Estes probably would have already done it.

I've never been privy to how abrasive the hydraulically pressed fine black powder is on the tooling.....but i'm sure it has to be replaced or retrofitted on a more or less regular basis as the fine black powder being pressed at the pressures they are on automated runs over time had to be very abrasive, so the tooling has to be made of some pretty hard stuff.

I would guess for insurance purposes they have made the business decision to let B14's Rest In Peace.

hth

Terry Dean

I personally have original examples of late 60's/early 70's Centuri B14-7's and Estes B14-0's that have cores so narrow that they MUST have been drilled. Any pintle that deep and small in diameter would most likely break under the ramming pressure.
The drilled core is approximately .0625 (1/16") in diameter and quite deep. The nozzle appears to be a standard "B4" profile nozzle diameter and shape.

Thanks for chiming in Terry. Your post confirms my suspicions. Maybe we will see a B8-x again some day, or a C5-0, but I think B14's are gone but not forgotten.

Sulfur does not act as a "binder" in EstesBP rocket engines. There is no need for an additive binder in Estes BP engines, because they press to approx 1.7 g/cc ..at these pressures the fine particles of black powder ie KNO3/S/C undergo a plastic deformation process...ie they become somewhat plasticized and they flow freely into and with one another.

http://en.wikipedia.org/wiki/Plasticity_%28physics%29

Sulfur does act as a pyrolant in black powder ie as an ignition promoter.




As far as Dextrin being used in Estes engines, I too have seen that MSDS..... I once asked a source if Dextrin was every used in the Estes manufacturing process as a binder or anything else..... and I was told no. It may show up on the that old MSDS because it was used a a burn rate modifier in the delay train...... but it was not used in the actual propellant.

If you look at modern day MSDS from the 80's forward you will see no mention of dextrin. Dextrin is a well know binder used by some who make BP pyrotechnic skyrockets. It will also slow down the burn rate. This is favorable in skyrockets as they are have full top to bottom cores and a slower BP is required.



It is my understanding the the large FGH Rocketflite BP engines actually used a water based elastomer as a binder but this was required because of their sheer size and their large cores.... the binder made the pressed BP grains somewhat rubbery so they wouldn't crack and they would adhere better to the casings.

HTH

Terry Dean

Now that we know all about B14's, and have a good idea on the Mini-Max's, Does anyone know how FSI cored/pressed their motors?

FSI F100 and E60 motors were pressed around a large-diameter pintle.
Not sure about the D18 and D20 though as those cores were MUCH smaller.

I don't know for sure, but I know they had at least 7 rammings in the F7 and F100. They added some propellant and rammed it in, then repeated until they were done.

I have seen some later B14's that looked more like B8's - they didn't begin to have the larger cores seen on the earlier B14's. It wasn't clear to me if this was due to worn out drills, substitution (ie, selling B8's as B14's before finally getting new cert's and name changes), or mislabelling.

(I posted a pic of the various B14 and B8 nozzles somewhere, but danged if I can find it now...) [Edit: It was on my old website, but I need to upload it to my new one.]

Doug

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IIRC, that's the way some of the Chinese motors were done, creating a pulsing thrust. I havn't flown my D5's or long burn C6's yet, so I'm only going by memory of what has been posted here in the past.

I think there was a later (possibly Centuri blue or green casing era) version of B14 make with a deep tapered core rather than the core with two steps seen earlier. It was much deeper than the B8/C5 core.

I have one of those blue-casing motors (a Centuri B14-7, Date Code: 110 1 73). Its nozzle is *very* wide and is almost cylindrical in cross-section, rather like the "nozz-hole" orifices in the Quest MicroMaxx motors. The tapered propellant grain void looks conical (it may be cylindrical for the upper 20% or so, but the foreshortened view makes it difficult to tell).

I also have an Estes B14-5 (Date Code: 21J5), whose nozzle looks like a B4's nozzle (going from memory, as I don't have any B4 motors on hand). The nozzle is considerably narrower than the Centuri B14-7's nozzle; it is a straight-sided cone that narrows down to a short cylindrical section. The grain void beyond is almost cylindrical, being a gently-tapered cone.

For comparison, a Centuri B8-5 I have (Date Code: 10l8? [the bottom of the third character wasn't printed]) has a nozzle only slightly wider than that of an Estes B6-4 (Date Code: 10 A 10). The grain void is conical, with perhaps the upper 10% - 15% being cylindrical.

Here it is: (The dimensions are nozzle depth.)


And here's a close-up:



Doug

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Thank you for posting these pix, Doug!

I think the right most B14's in those pics are the "precursors" to the B8 motors that replaced them.
Functionally, those last produced "B14s" I theorize were actually B8's; I have some late B14-7's and I cannot tell ANY dimensional difference in them from the B8-7's from a year later even under magnified examination.

here is a theory (based on nothing but a guess):

Motor manufacturers can change a design without recertification as long as there is no major change. Often a motor is redesigned because of a change in propellant (different sources of black powder) or a change in place of manufacture. Usually the new samples are submitted for recertification, sometimes with the same motor designation (like the Quest C6-5 made in USA, Germany and China). back in the 1970's they may have tweaked the B14 design and tried to keep calling them B14's, but then either decided to recertify them as B8 on their own or after the NAR told them to do so.

I still think there was a tapered bore version (deep large hole plus deeper tiny drilled cylinder) as well as a long tapered single bore version (like a B8 bore, but deeper).

Any photos or measurements of a 196's era English units B3 motor?

product be submitted for testing.

That's kinda how I'm thinking, too.

But note one key diff: The narrow bore B14, which looks much like the B8, is still deeper, 0.75" versus 0.6". It has the same depth as the bigger bore B14's.

OTOH, it could simply be the later B14 (in the pic) was formed on a pintle that had been worn down (eroded) by too many pressings, and then drilled. Or maybe the drill bit itself, assuming a two slope drill bit, had been worn down by too many drillings. (A bit with a long, narrow tip that also includes a wider cutter up the shank, sort of a like a bit in a countersinking mount, could be used to simultaneously drill the deep, narrow core while also widening and reshaping the nozzle. Such as bit could wear faster on the abrasive clay end thus resulting in the smaller nozzle openings while still maintaining the deep bore.)

But I like the precursor idea better :)

Doug

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http://www.forums.rocketshoppe.com/...achmentid=10757

3 b3- rocket engine cores from 1967 by SEL



also found this:

http://www.forums.rocketshoppe.com/...54&postcount=62


the B.8 (old designation) was of course a B4 (new designation) Although MMI sold at as a B6......


Terry Dean

I find that picture to be very Hypnotoad-esque.

:D

My early B14 engines from '68 or '69 look almost exactly like those B3 nozzles that OBVIOUSLY have drilled cores.

They should. As I understand it, the only difference between the B14 and the B3 was the metric versus imperial units designation. 3*4.45~=14. At some point, the thin walled casings took over. Not sure how that may have affected things. But if the ID of the case is greater, then less depth of BP is needed to achieve the same volume of BP (~equating volume with impulse). So I wonder if the core had to be revamped somewhat to deal with that, to keep from breaking/burning thru too soon.

Doug

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I had B3 motors with the thick walled casing (same as used in the classic 1/4A3, 1/2A6, A5 and B4 18mm motors). I flew them. They worked.

Guys,

Can you give me an example of what you might have flown on a B14-7. I always think of the B14 as a heavy lift motor and I'm having trouble reconciling that with a 7 second delay.

Estes recommended it as an upper-stage engine for the Apogee II, and the Delta when lifting the Camroc. For the Farside and Farside-X, they recommended the -6. Yes, they made a -5, -6, and -7!

Centuri was a bit more liberal in recommending the B14-7 for its kits, listing it for their small, ST-7 (like Javelin) or ST-8 (like MX774) kits, but *not* for their multistagers!

This is an interesting question, Gus. I can remember in my first go-round with modle rocketry circa 1967-1972, that I had B14 motors........ But I really don't have any memories of actually using any. I was not (and still am not) a very good modeler, and once I figured that out (which was within the first 2-3 kits), I basically just read the Model Rocketry magazine and collected kits and engines at NARAM-12 and NARAm-13. I know for sure that I spent at least $500 each visit and brought a lot of stuff back but never built it and it sat in a strage shed until the late 70's or early 80's when my mom moved and threw it all away. She did keep the MR magazined and gave them to me years later.

In the 7th grade we had a rocketry "club: that consisted of a few people in the overall science club, and my neighborhood friends only came around to watch me launch and chase my rockets. They pushed the button sometimes but that was about it. There was no local hobby stores as I lived in a small rural town (pop. maybe 3,000) so I was basicially a lone rocketeer as a kid from 12-16.

Sorry to get carried away. I know from my memory that I had 2 rnage boxes stocked full of modle rocket engines of all types purcahsed between 67-72... I would estaimate at least several hundred easily.

Terry Dean

I flew the old B3-7 in my Centuri Javelin - what a neck snapper! Maybe that is the cause of the arthritis in my neck today :mad: