Do I correctly understand that the D8 was an 18mm motor?

That could have potential today, like on the Orion!

__________________
Craig McGraw

BARCLONE Rocketry -- http://barclone.rocketshoppe.com
BARCLONE Blogsite -- http://barclone.wordpress.com
BARCLONE Forum -- BARCLONE Forum

BARs helping BARs

SAM 0044
AMA 352635

Das ist richtig.

__________________
Scott D. Hansen
Ye Olde Rocket Shoppe - Your One Stop BAR Shoppe!
Ye Olde Rocket Plans - OOP Rocket Plans From 38 Companies!
Ye Olde Rocket Forum
WOOSH NAR Section #558

They were standard 18mm x 70mm and only available as D8-0 and D8-3, both almost filled to the top. They were really just HOT C engines with 12.5 N-sec spec and about 11 N-sec tested. They did have a core to get the peak thrust up to about 16-18 N but the average thrust was closer to 7 N rather than 8 N.

__________________
Carl McLawhorn
NAR#4717 L2
semroc.com

We are planning the "thick-walled" version as our "R" package. It was the original Estes size tube in the early 1960's. The famous A.8-3 and B.8-4 used that tube.

Retro (R) family



Old# New# Impulse Burn Time
N-sec sec
1/4A.8-0 1/2A5-0R 0.75 0.15
1/4A.8-2 1/2A5-2R 0.75 0.15
1/4A.8-4 1/2A5-4R 0.75 0.15
1/2A.8-0 A4-0R 1.56 0.40
1/2A.8-2 A4-2R 1.56 0.40
1/2A.8-4 A4-4R 1.56 0.40
1/2A.8 A4-5R 1.56 0.40
A.8-0 .6B3-0R 3.12 0.90
A.8-3 .6B3-3R 3.12 0.90
A.8-4 .6B3-4R 3.12 0.90
A.8-5 .6B3-5R 3.12 0.90
B.8-0 B3-0R 4.90 1.40
B.8-2 B3-2R 4.90 1.40
B.8-4 B3-4R 4.90 1.40
B.8-6 B3-6R 4.90 1.40
B3-0 B16-0R 4.90 0.30
B3-5 B16-5R 4.90 0.30
C.8-0 .7C3-0R 6.67 2.00

__________________
Carl McLawhorn
NAR#4717 L2
semroc.com

Bad weather here and having internet/computer problems. A power surge took out on of my router sockets. That took me three hours to figure it out.


Craig said,



Scott said,


I have the longer version which to me is 2 3/4 inches long on my American tape measure. As a carpenter I absolutely refuse the metric system.


James Pierson
NAR# 77907

Make no mistake, I want 1/2A boosters. 1/4 could be fun, too. I read about someone flying a Farside using 1/4A boosters in the first two stages, on a baseball diamond. Sounds like fun, but I'm afraid of the risk - will there be enough buyers to justify 1/4A boosters?

So, here's my take on how to mitigate the risk on this part of of the motor spectrum. Build only T motors (13x45mm). Ship each pack with one 18x70mm empty casing to be used as an adaptor. Pre-print a dashed line on the casing where the user saws it down to 45mm for use as a shorty case. One motor could be used as 13x45, 18x45 or 18x70mm. If users have a hard time making one case last for the entire pack (ie, 3 or 4 motors), then ship one empty case for each motor in the pack.

If a smaller (than T) size is deemed necessary, pre-print a cut line on it. I know 1/4A3-3T and 1/2A3-0T motors can be cut down to 1.25". I've done if before (in what else, a tiny Midget

The key here is that, for example, one motor takes the place of three. An A10-0T can also be used as an A10-0S and an A10-0 (~A8-0).

In the case of this particular motor, I'd like to see the thrust tail shortened a bit (in time). It's my understanding the better description of the motor is a 1/2A with extra powder loaded on it to keep it from bursting during the initial thrust spike. That may or may not be true, but the point is that, while a nice spike is good, the low tail is undesirable.

What all this leaves out is 13mm B motors. Perhaps those would use a longer case. I suspect there may be some serious technical challenges with these. MPC had problems. And I think Centuri did, too. And that may explain why Estes never did B-T's.

Now, if a reliable B motor can be built in a 13mm case, then the same adaptor scheme described above may apply. I have a hunch there's a certain minimum aspect ratio (diameter to length) that applies for getting high reliability. IOW, you can't put a big core in a narrow motor. So a 13mm B14 might not be possible, but I'm not an expert.

Anyway, that's my two cents on the 1/4A, 1/2A and A impulse segment of the spectrum.

Regards,
Doug

(vbg) I saw the LDRS video at yesterday's DARS meeting. Seems I made the cut. They had my 4" upscale Midget sustainer on an I285. The rocket and flight looked great; I looked and sounded like my usual hillbilly redneck self

Doug

Carl,

What market(s) are you planning to go after with your initial motor release?

1) Hobby distributors, dealers, stores

2) Mail-order only (Guys like us)


If #1, then you should make A8, B6 & C6 as they will fit in the 'other' guys rocket kits. You'll
probably have to try and beat them on price to have any hope of getting shelf space. This would not be a concern if Semroc kits are being mass-marketed as you can change your kit instructions to reflect any motor types you produce.

As for #2, I like 'em all! 13mm, 18m, 24mm, etc. As for 15mm, unless there are models that use that size motor, I'd leave it on the drawing board.

At AeroTech, we actually experimented with 15mm motors. We built and fired some for Apogee Components in the early 1990s when we were trying to get a full 'C' motor in a 13mm case. The 15mm seemed like a good compromise but it would have required Apogee to carry a whole set of additional parts for this motor size. Plus, we noticed the casings were pretty close to failing by the end of the burn.

I have one of these burned, 15mm, C20, casings in my collection.

Bob

Since the bulk of our current kits are designed around the A8, B6, and C6, it is not an option to skip them. It is probably true that very few hobby stores will carry specialty engines that Estes or Quest do not offer, with the possible exception of low impulse boosters. We are targeting the online market with the "non-standards" hoping that as they become more mainstream, the more sophisticated hobby stores will add them.
Our list is more for planning than anything else. We will be freezing the list in a few weeks. It does not mean we will do all of them, but we won't have the paperwork to do any additional ones in the near future.

__________________
Carl McLawhorn
NAR#4717 L2
semroc.com

Carl,

Don't forget about California classification for your motors.

I want to fly them!

Bob