estes Short engines

[SaturnV]

Hello everyone. This is my first post but I have been checking out this site for about 6 or 7 months. Lots of good info here. First got into rocketry back in the mid 60's, then got out of it in the late 70's. Now I am back into it and am building a lot of the kits I once owned, and some I could only dream of owning in my youth. So far I have built a Gemini-Titan (PDrocketry), a saturn V (Estes), and with the help of balsa machine service a wac corporal, mini bertha, screamer, midget, skyhook, V2, etc. Now to my question. I wish to fly some of my "S" engine rockets, not with the mini-brute engines but with actual S engines. For the upper stage of my Midget I simply made a little fixture that holds the 1/2A engines and cut them on a saw to the S size. However, Estes stopped making the 1/2A or full A booster engines so I am stumped here. Way back when Estes packed their engines with a little paper cup on top to hold the ejection charge (any of you old timers remember that??) I would make my own booster engines by removing that paper cup and dumping out the loose blackpowder grains. These booster engines always worked in igniting the second stage. Am wondering if I could still do the same by removing the clay on top of current engines . Appropriate safety measures would be taken of course. Anybody ever try this? I should mention that when I was growing up everybody in the neighborhood that wanted booster engines would do as I did and simply modify regular engines. Any other manufacturer of engines besides Estes?? I am basically just re-entering (no pun intended) this hobby and cannot find anything on the web about this. Thanks to all in advance

[Green Dragon]

Well, safety code issues aside ( it is technically illegal to modify ANY motors, including cutting off the cardboard casing to 'short' specs. ) ...

cutting down a 1/2A or A engine to 1.75" short, should pose no hazards, and would fly nicely.

However, you mention pouring out the ejection charge powder and using a regular engine for a booster - although it sounds liek this would still adequately ignite an upper stage engine - the DELAY would still be in place, and would therefor NOT stage at burnout, like a true booster engine would.

I would definately NOT reccomend using a delay engine as a booster, as staging delay would lead to tip-off and non-vertical flights.

~ AL

ps: and welcome to the forum, lots of rocket crazies here, me included, will help each other out as possible, guys teach me lots.

[stefanj]

If you hunt around, you can still find A10-0T booster motors.

I plan on using them in my Firefly by gluing the motor inside of a "shorty" sized dummy casing.

[tbzep]

I will admit that I once took a D12-3 and dug out the clay cap, ejection charge, and delay train one day when I wanted to chad stage a Big Bertha and realized I was out of booster motors. (It was a private launch, BTW.) It worked exactly like a regular booster, but I was paranoid enough about a static charge igniting it while digging the stuff out that I wore my fire gear for protection (trained professional and all that stuff). :rolleyes: I only did it that one time because I've always kept a supply of booster motors on hand since then. Would I ever do it again in a pinch? I'll just take the 5th on that.

[Doug Sams]

I wish to fly some of my "S" engine rockets, not with the mini-brute engines but with actual S engines. For the upper stage of my Midget I simply made a little fixture that holds the 1/2A engines and cut them on a saw to the S size. However, Estes stopped making the 1/2A or full A booster engines so I am stumped here. Basically, your only choice is Estes, although there are a few Quest B6-0 boosters out there you might could cut down to "S" length.

If you use a cut-down Estes 1/2A6-2 in the sustainer, you should be OK for single stage flights, but for staging, you will want a longer sustainer delay. Otherwise, you're likely to get ejection while the rocket is still moving fast on the way up resulting in a zippered airframe or shredded chute and crash. I zippered my ~30yo Midget 'cause of too short a delay and was mightily bummed.

Unless you find someone willing to part with actual shorty motors, you're gonna have to roll your own. The S motors are pretty scarce. They went out of production around 1972, so they've been gone a long time.

I have a fleet of over 20 Midgets in various sizes and scales, and fly them on everything from 1/8A's to J's. The common motor combos I use with my K-40 clones are A10-0T and/or B6-0 boosters with A8-5 or 1/2A3-4T sustainers.

With the T motors, you take a spent 18x70mm casing (ie, standard size motor) and saw it down to 1.75". Actually, saw it to 1.8" then sand it to the exact length - you want a nice, clean, square end to tape flush to the other motor. Insert the T motor in it and add a couple drops of white or yellow glue. Voila! Home made S motors.

If you use the 1/2A3-4T in the sustainer, try to find some with the all-purple printing on the motors. These are a bit older and work great. Some of the newer ones, with the multi-color printing, have nuclear ejection charges which have been know to break the shock cords and even rupture the airframes :(

With the standard sized motors, you can, as you have stated, cut them down to length. Both the B6-0 and A8-5 have over an inch of open space you can saw off. I like to stuff a bit of flame proof wadding into the end before I begin sawing just in case the sawing produces a spark which might make things hot :) Be sure to remove the wadding before you tape the motors together. Also, make sure you scrape, eg, with a small drill bit, the sustainer nozzle to ensure it's clean and unobstructed for staging. One wrap of cellophane tape is the standard for joining the motors.

I love staging and fly lots of them besides my Midgets. (Sunday's outing was four 2-stagers and a cluster.) If you get the motors prepped well, you'll have lots of success.

Here's a shot of my 2.2X upscale Midget just coming up to pressure. That's 3 outboard B6-0's (or C6-0's) and a centerline D12-0 in the booster. I think that's the burn string falling away just below the burn stick. Or maybe it's one of the ignitor lead extensions.
http://home.flash.net/~samily/exbp/midget70.jpg

Doug

[SaturnV]

Thanks guys. I thought about using the A-10-0T engines, but my local hobby shop does not have any and I checked the Estes catalog and they don't make them anymore. Couple of other shops I can hit, will try them this weekend.
Sure wish companies would make a run of these old motors, like some gun companies do. Every once in awhile Winchester or somebody will do a quick production run of some long obsolete ammo.....just to keep their customer base (that had faith in the company and bought their firearm) happy.
I'd like to see the B-14 motors back too!!

[tbzep]

I'd like to see it happen too. However, I doubt we will ever see the B14 again because the cored motor is more complicated/dangerous/less profitable to make.

[Gus]

A10-0Ts are currently available at AC Supply. (http://www.acsupplyco.com/estes/engines.htm)

[Ltvscout]

A10-0Ts are currently available at AC Supply. (http://www.acsupplyco.com/estes/engines.htm)
There's that rocketry store down in TX that has them as well. Unfortunately, I don't recall their name. :o I'm sure Dave will pipe in if he sees this post. ;)

[JRThro]

There's that rocketry store down in TX that has them as well. Unfortunately, I don't recall their name. :o I'm sure Dave will pipe in if he sees this post. ;)
Scott, do you mean Launch Pad 2000?

Here's a link direct to their mini-engine page:
http://www.launchpad2000.com/modrocen-miniengines1.html

(I belong to the same club as Dave and Harvey, the proprietor of Launch Pad 2000, btw.)

[Ltvscout]

Scott, do you mean Launch Pad 2000?
That's the one. Thanks for posting the link, John.

[SaturnV]

Okay guys, I found some older A-10-0T engines locally. Bought all they had (4 packs). hope these work, I really didn't want to mess around modifying engines. I travel a lot and will start hitting the hobby shops looking for these now obsolete engines. Thanks to all of you.

[handeman]

Here's a shot of my 2.2X upscale Midget just coming up to pressure. That's 3 outboard B6-0's (or C6-0's) and a centerline D12-0 in the booster. I think that's the burn string falling away just below the burn stick. Or maybe it's one of the ignitor lead extensions.


Doug,

Looking at the picture and reading, what is the upper stage? Is it a single D?

I've never tried to cluster multi stages and didn't think it could be done reliably. Can it and if so, How?

[Doug Sams]

Looking at the picture and reading, what is the upper stage? Is it a single D?It's a single motor, but I'm not real sure which type. Probably a D12, but might be an E9. I've flown both.

Doug

[Doug Sams]

I've never tried to cluster multi stages and didn't think it could be done reliably. Can it and if so, How?There are basically two configurations that work well, with minimal risk. One is a clustered booster to single motor next stage. The other is a clustered booster to clustered next stage, but the booster breaks away in pieces. That way, if one booster motor burns out sooner than the others, its separation won't force the others to separate prematurely. A single piece clustered booster is just asking for problems.

For the first case, you use a burn string. This holds the bird on the pad, releasing it only if the center motor lights and burns the string holding it. That way, it is assured that the motor that lights the next stage has indeed been lit.

Here's a pic of the burn string attachment points on my Uber Tuber:
http://home.flash.net/~samily/tuber/utboost-bottom.jpg

You can see my burn stick in the earlier pic. It mounts on the rod and projects under the center motor. The stick is coated with ablative epoxy, but can also be drilled and replaced if/when it gets too charred.

The string attaches as shown here:
http://home.flash.net/~samily/burn-string/BurnString3.gif

The transparent gif doesn't work well on the blue background. You can see it better here along with more info: http://home.flash.net/~samily/burn-string/

The second method puts a separate motor tube and fin on each booster motor. Each one falls away as its sustainer lights without need for perfect synchronization with the other booster motors.
http://home.flash.net/~samily/thridget70/thridgetp.jpg

More details here: http://home.flash.net/~samily/motor-eaters/ and a few more pics here: http://home.flash.net/~samily/thridget70/

Also, here's a shot from LDRS last summer. Dave Schaefer and I were racing similar 3-to-3 motor clustered stagers. One of mine didn't light :( Its rod speed was marginal on two, and weathercocked badly in the Texas wind resulting in a near power prang when the sustainers lit. But it might just finally make its post-repair debut flight next weekend :)
http://home.flash.net/~samily/thridget70/3-to-3-drag3p.jpg

Doug

[handeman]

There are basically two configurations that work well, with minimal risk. One is a clustered booster to single motor next stage. The other is a clustered booster to clustered next stage, but the booster breaks away in pieces. That way, if one booster motor burns out sooner than the others, its separation won't force the others to separate prematurely. A single piece clustered booster is just asking for problems.

Doug

Doug, you are the "Rocket" man. :cool:

A clustered booster to single upper stage I pretty much figured out, except for the burn string idea. Never heard of one before, but will never try a cluster to single without it. It may have occurred to me after a lawn dart to two.

The separate tubes and fins for the booster cluster also makes a lot of sense. Again, something I hadn't thought about. I probable would have figured it out, eventually, maybe.

Time to get to the workbench. It’s amazing how many ideas pop up when you get a little more good info.

Thanks

[SAABMaven]

Doug,

Thanks for documenting that so well. The burn string idea is brilliant! The pictures and diagrammes are all printed out and on my work table... for the next few weeks merely to think about.

Clusters are interesting but also complex in a staging environment. Have you (or anybody else) considered using a larger D-motor in the first stage(s) and then a smaller C-motor in the upper stage(s)? Will the smaller upper motor ignite?

The numbers say that the initial thrust of a D12 motor is 30 newtons for ~0.26 seconds, wheras a cluster of three A8 motors also thrust at 30 newtons for a slightly shorter time. Assuming the same design weight, is not the choice of a single D12 the simpler design?

Clustering on the first stage is attractive, I've got to admit. My staging experience was never something about which I could boast... the flights were unimpressive and stressful... a few metres off the ground slowly, enough for the gusty wind near the ground to have an effect and tip the rocket alarmingly off vertical before the second stage ignited. Slow flight is nice for video cameras but too mich time is spent in turbulent air.

The only other first stage clustering idea that I've been thinking about is to cluster a single D12 motor with three A-10PT (Plugged) motors for an initial thrust of 60 newtons at 0.2 seconds into the flight. The A-10 motors burn only half as long as the D12 motor, they are just empty weight; but it seems to me that the initial second of flight, so close to the ground turbulence, is critical. Your thoughts?

Cheers,
Rob in Vermont

[Doug Sams]

The burn string idea is brilliant! I can't recall where I got it - maybe from an Estes catalog back when I was a kid - but it's someone else's and not mine.

Have you (or anybody else) considered using a larger D-motor in the first stage(s) and then a smaller C-motor in the upper stage(s)? Will the smaller upper motor ignite?That's how the Estes Comanche works, staging a 24mm motor to an 18. Mine is gap staged and properly vented. It works great. And if I ever build a Farside-X clone, I'll likely do the same thing.

The numbers say that the initial thrust of a D12 motor is 30 newtons for ~0.26 seconds, wheras a cluster of three A8 motors also thrust at 30 newtons for a slightly shorter time. Assuming the same design weight, is not the choice of a single D12 the simpler design? That's a good observation. Both my one-piece clustered boosters are clustered only because a solo D12 won't do the job. Extra motors are needed.

That said, I've tinkered with the idea of playing with a cluster of A10s in a booster, although in this case, they would be three or four A10-0Ts in a multi-piece booster staged to 3/4 sustainer motors. The idea was to do a small field version of the Thridget.

The only other first stage clustering idea that I've been thinking about is to cluster a single D12 motor with three A-10PT (Plugged) motors for an initial thrust of 60 newtons at 0.2 seconds into the flight. The A-10 motors burn only half as long as the D12 motor, they are just empty weight; but it seems to me that the initial second of flight, so close to the ground turbulence, is critical. Your thoughts?The idea is to get lots of thrust without lots of total impulse. It gives good rod speed but doesn't put the bird in orbit. I've flown a D with three Bs and also with 3Cs. Three As would work, too. In my case, tho, Rocksim showed a rod speed I didn't like with 3 As, so I never tried it. It probably would have been OK, but there wasn't any extra margin in case one of the outboards didn't light.

On a lighter rocket, I'd give it a try, though.

Doug

[Doug Sams]

My staging experience was never something about which I could boast... the flights were unimpressive and stressful... a few metres off the ground slowly, enough for the gusty wind near the ground to have an effect and tip the rocket alarmingly off vertical before the second stage ignited. Slow flight is nice for video cameras but too mich time is spent in turbulent air.Rob,

It sounds like your birds were just too heavy - or the rods too short - to get sufficient speed before clearing the rod. Most Quest and Estes boosters are what I'd consider medium thrust motors. B6-0 and C6-0 motors are fine on ordinary two-stage rockets, but are gonna be grunting in the first stage of a 3-stager or in some of the heavier 2-stagers out there. The D12-0 and rare C11-0 are well suited for this, tho. The Estes Echostar, for example, is one 2-stager that looks marginal on an 18mm booster, and begs for upgrading the booster to 24mm.

Generally speaking, BT-20 (ie, minimum diameter) and BT-50 based 2-stage rockets work great on B6-0s and C6-0s. If you build really light (impossible for me) and use a long rod, a 3-stager is possible, typically min diameter. A light BT-55 2-stager can also be done, or even a BT-60 if you build really light.

So, if your staging experiences have been slow and nearly horizontal, besides clustered boosters, you can try lighter rockets and longer rods, which may in turn dictate bigger lugs. For example, all my 24mm powered stagers use 1/4" lugs so they can be flown off 6' rods.

There are lots of plans for stagers here and on JimZ that should fly great on B6 and C6 boosters.

For 24mm stagers, anything BT-55 to BT-60 works great. When you start approaching 2" diameters, you gotta be careful. It's easy to end up too heavy for the D12-0. (That's how my clustered booster Midget-70 came to be.)

For 13mm stagers, if you have a stash of A10-0T booster motors, you can have lots of cheap fun. These work great up to BT-50 for 2-stagers, and I've even flown a 3-stage Midget variant without problems (other than losing sight of the sustainer). The big thrust spike of the A10 allows it to do more than a typical A (eg, A8-0).

Staging is probably my favorite thing to do in this hobby. That "free kit" Midget Estes shipped me in 69 or 70 has made a staging monster out of me :)

Doug

[SAABMaven]

Thanks Doug!

I'll have a closer look at those plans over the next week or so. Appreciate the insights.

Cheers
Rob in Vermont