We don't have the same problem as the larger companies. We already have more items online than they have combined. Are there enough buyers to justify a BNC-10A nose cone? No, but there are enough buyers for a wide selection of parts as long as each one does not require capital investment and large inventories. We look at engines the same way.
The original Estes engines were the same ID (.406") as current 13mm engines. They changed to .5" ID for "manufacturing reliability." Their C.8-0 was a 2.25" slug of BP. It was packed in about 6 different steps. You can only pack one charge a depth of roughly the diameter of the tube, so the .5" ID made for fewer steps, just like shortening the length of the 13mm "T" engines.

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Carl McLawhorn
NAR#4717 L2
semroc.com

We will have that! They can't be contest certified without it either.

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Carl McLawhorn
NAR#4717 L2
semroc.com

Carl,

Have you ever asked Vern or Ed Brown about the run of mini-motors they made in glassine covered spiral-wound tubes (or did *you* ever try making motors like that?) The ones I have (two A3-0T and one 1/2A3-0T) are marked 6M171 and 6M271. I can't remember for sure, but I think I got them at NARAM-13. Maybe they were test motors that somehow got out in the wild. I think I flew a few of them, but don't remember if I just had boosters or if there were delay ones made. I certainly don't remember the flights or if they had any problems due to the spiral.

Knowing what little I know now about the motor making process, I could see a few problems starting with manufacture (could the tube survive the pressure needed for pressing) to operation (did the pressure on the slurry force propellant into the groove enough that there was no way for the flame front to propagate up it?).

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Roy
nar12605

I never knew that!The Micro-Max II engines are spiral wound fishpaper like coupler tubes. Looked like a great idea for 10mm and 13mm since fishpaper is about eight times stronger than kraft. The walls could be much thinner. Unfortunately, fishpaper burns through much faster and the spirals, unless very tight, form a "fuse" of black powder around the delay. The spiral fills up with black powder so the delay gets bypassed.

I have tried glassine covered spiral tubes for DECAPS. It holds together for nine seconds, being a much better insulator and does not deform as bad as I thought it would under pressure. The difference in cost between high-pressure kraft and the spiral tubes is very small so the parallel kraft is probably better..

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Carl McLawhorn
NAR#4717 L2
semroc.com

Checked the 2006 Estes catalog and online, the 1/2A6-2 is still listed.

How large of a list?

A full line of 18X70, the "R", "S", and "T" series. Including low power boosters and core burners.

Is there any reason the "R" series could not be made in a thinner walled 13X70mm tube as well as the heavy wall 18mm?

A 13mm (or 18mm) B3-x with a 1.4 sec burn, more fun stuff!

How about the 10mm for the contest folks.

As complete as possible for at least the first year.

The "R" series is the "Retro" series modeled after the original from the early 60's. Also the early A5 engines used the thicker walls.

The 13mm B is there, but the long burn in the 13mm tube may not be feasable.
That is definitely in there!

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Carl McLawhorn
NAR#4717 L2
semroc.com

I checked an Estes B6-4 with a depth gauge, 1.2" of headroom above the cap. How much clearance is needed for manufacturing?

The Estes B6-4 is only about 4.3 N-sec. We are trying to get closer to the specified limit. Then it might be close.

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Carl McLawhorn
NAR#4717 L2
semroc.com

Are "core burning" and "port burning" the same thing?