homemade E~G motor?

Hi!
As I said on another topic, I live in south america and don't have access to 20N+ total impulse motors.
I need motors with about 45N to be able to test the stabilization I wanna do.

I guess 10~20 motors will do for first tests.
It doesn't need to be too good. I'm interested on the electronic stabilization, not on the propulsion.

Any suggestions on the safest/easiest (not necessarily cheapest) way make it?

I'm thinking on a few options (ordered from what seems to be the most safe/easy to least):
1) I have a friend going to the US soon. It's not wise to ask him to bring explosives on his airplane trip back, but an Aerotech RMS Motor Case 29mm is probably fine.
2) Something like a PVC tube with 15cm length and 3.5cm diameter (maybe too much), no nozzle
3) Trying to make a "reloadable" motor with a gilette/deodorant can (anyone tried that? I couldn't find it).. they even have a sort-of nozzle (not sure it can handle the pressure)

In any case, I'd need to do the propellant myself (I'm assuming sugar+KNO3).

Click the link here for research motor forum access: https://www.rocketryforum.com/showthread.php?17943-Research-Forum-Access

Requirements for the subforum are:
1) NAR or TRA senior member
2) US Citizen
3) High Power Certification (Level 1, 2 or 3)

If you can get D12 motors, both booster and upper stage type, then you could probably do your tests with 2 stage and 3-stage D12's.

That is what I did with Sunguidance in 1988, with a BT-60 rocket weighing less than a pound. Page about the project:

https://georgesrockets.com/GRP/RandD/Sunguidance.htm

Single and 2-stage D12's were used for most of the tests. For some final tests, an Estes Cineroc was added to get onboard movie footage. For that, it used an E20 twice, but the last time the E20 ignited badly and almost crashed. After that, the final Cineroc flight was 3-staged, D12 to D12 to D12.

Also see this movie, which includes all the Cineroc flights and some more modern onboard video (much smaller and lighter camera):

https://georgesrockets.com/GRP/video/VidFiles/Sunguidance_Web.mov

The final flight in the movie, made in 2006, was a D12-0, to D12-0, to D12-3, to D12-0, to E9-6. Yes, 5 staged, with a 3 second delay from the 3rd to 4th stage. The aerodynamic/structural first stage used for stage 1 and 2, was draggy and made the rocket fly so slow and over-stable, that the nose fins could not control the flight path until finally the 3rd stage ignited and dropped that stage 1 & 2 booster.

BTW - my Avatar is from a 2-stage flight made in 2004, it was set for a "hard ride" and overshot somewhat. Also seen in the video (SEARS launch).

- George Gassaway

Don't use pvc or a deodorant can .

Use a rocket motor case that's what they are designed for.

https://www.nakka-rocketry.net

https://jamesyawn.net

Tonimus said:

Click the link here for research motor forum access: https://www.rocketryforum.com/showthread.php?17943-Research-Forum-Access

Requirements for the subforum are:
1) NAR or TRA senior member
2) US Citizen
3) High Power Certification (Level 1, 2 or 3)

Click to expand...

It seems a bit paranoid to require all those things (I'm neither) to talk about E~G motors.

Very cool, George! How did you attach the servos to the fins? Directly or with some extension. They are not on the same height (I assume because of servos positioning), right?
I don't like the idea of multiple stages (for now) though. I think it adds more complexity that I'd like for propulsion (I like the complexity in the control, not on propulsion)

Danh said:

Don't use pvc or a deodorant can .

Use a rocket motor case that's what they are designed for.

https://www.nakka-rocketry.net

https://jamesyawn.net

Click to expand...

This would work for me. But can I easily refill them with homemade propellant?

If it's not easy, I guess the pvc+clay+sugar/kno3+clay youtube video (E45 equivalent motor) would be enough for my first tests

kavelot said:

It seems a bit paranoid to require all those things (I'm neither) to talk about E~G motors.

Click to expand...

It does seem paranoid until you realize that the same technology can be used to build much larger motors that could be used by terrorists. Since you are not in the U.S. you can't get access anyway, so there is no point in asking.

Zeus-cat said:

It does seem paranoid until you realize that the same technology can be used to build much larger motors that could be used by terrorists. Since you are not in the U.S. you can't get access anyway, so there is no point in asking.

Click to expand...

Sure! Chemistry and physics classes can be dangerous. Guns and ammo too. But trying to control information (and some products) never worked (specially when these information can already be found in books/internet).

Anyway, I'm ok with people being paranoid with some things.

The only reason they are being "Paranoid" is because ITAR doesn't like discussion in open forums. It's just a liability issue.

kavelot said:

It seems a bit paranoid to require all those things (I'm neither) to talk about E~G motors.

Click to expand...

Dangerous is dangerous. Explosions that can main or kill you do not care whether the propellant being mixed is intended for a J motor or a bunch of less-than-H motors.

Far too many forget this hobby came into existence in large part due to the "basement bombers" of the mid 1950's. People trying to make their own rocket motors using steel pipe or loading certain high energy things inside of empty Seltzer cartridges, which often went off like bombs or grenades, throwing shrapnel. Burn injuries, lost fingers, lost hands, lost eyes, or just plain dead.

So the hobby began with commercially made engines to get rid of that danger for the rocket builder / flier.

And yes, several people working for rocket companies such as Estes, Cox, Quest, and Aerotech HAVE DIED in accidents related to making rocket engines for the rest of us to fly safely. And those were PROS!

And sadly enough people still injured/killed making their own, after this hobby started, because they were ignorant of the hobby, ignorant of safety procedures, ignorant of the law (or not giving a "darn"), or ignorant of the risks even if they know procedures, and/or had "bad luck".

A few did it to save money, and some of those either lost a LOT of money due to their injuries, or lost their lives. What great "savings".

- George Gassaway

kavelot said:

Very cool, George! How did you attach the servos to the fins? Directly or with some extension. They are not on the same height (I assume because of servos positioning), right?

Click to expand...

Wish I had pics to show. But basically there is a structural assembly inside that is sort of like a model airplane fuselage, two long side pieces. For say the pitch axis, the two pitch control surfaces are mounted to a common shaft that rotates around a bearing in the "fuselage". The bearing is nothing more than brass tubing. A plywood control horn is attached to the shaft, sort of like how a model plane control horn is attached to a control surface, and a pushrod going to the one servo that controls the pitch axis. And again the model plane fuselage analogy, the servo mounted inside the fuselage. For the Yaw axis, same ting. Except that the Yaw axis is mounted about an inch away (fore or aft) from the pitch axis, to allow for a practical fit.

So, the body tube slid over the fuselage. And the nose fins were attached using some square cross section brass tubing, that friction-fit inside of the next larger size of square brass tubing. Since brass can bend easily, there was a full length "spar" of music wire (1/16" OD) running across both of the pitch nose fin pairs, and same for the yaw nose fin pairs.

kavelot said:

I don't like the idea of multiple stages (for now) though. I think it adds more complexity that I'd like for propulsion (I like the complexity in the control, not on propulsion)

Click to expand...

Wait, you are talking about making your own rocket engines having never done that before, and you're thinking that staging D12's is what would be too complex? ? ? :y: :grin: :wink:

First though, can you confirm whether ot not you can get D12-0's and D12-3' or D12-5's? If not, then its moot. But if you can, it is SO easy to stage.

What I did with my model, except for that crazy 5-stage flight, was something called "CHAD" staging (Cheap And Dirty Staging). No lower stage airframe at all. For a 3-stage flight, I would securely mount the final D12-5 in place, then using one wrap of masking tape, wrap to secure a D12-0 underneath that D12-5. And then for the first stage, use another wrap of masking tape to secure the first D12-0 to be the first stage engine.

Now, the rocket was over-stable, so that despite the tail weight of the two D12-0's, it was still stable enough aerodynamically. If it had not been over-stable, and if it had needed some lower stages with fins, I'd have done the same sort of prep where it was engine taped to engine

Key for the staging is having a tape wrap, so that when the lower stage first has its hot gases pop thru to ignite the upper stage, te tape holds the stages together until the upper engine really does ignite and causes the tape to break free. Otherwise, some staged models sometimes fail because the lower engine's initial burst of hot gases forward, can cause the stages to pop apart before the upper stage engine ignites. I had that happen a couple of times, before I finally started using the tape method.

- George Gassaway

You can cluster as well as stage, if you can get enough motors. BP clusters weigh more than a composite for their performance, but not as bad as a "crude" motor would be.

If you were to try to make motors, be very serious about it, namely I wouldn't be trying some kind of advanced rocket building such as stabilization at the same time. It's a whole seperate project at least.

bill_s said:

You can cluster as well as stage, if you can get enough motors. BP clusters weigh more than a composite for their performance, but not as bad as a "crude" motor would be.

Click to expand...

True, he could use a cluster. But for a rocket guidance project, as long as there is enough thrust to safely take off, a longer burn is generally better for testing the guidance system, and generally "looks more cool" to see a slower-boosting rocket correcting itself for several seconds rather than a fast boost.

So, lacking a single long burn motor like an E6 or F10, or G12, then staged D12's (and E9's on top) are a pretty good second choice..... if the rocket mass allows (my sunguidance rocket was light enough to be able to fly on an E6. A later gimbaled engine rocket was heavier, an E6 was too low of thrust, so it usually flew on an F10).

- George Gassaway

OK, I got out my old model, and took some pics of the mechanics for the nose fins and servos.

Assembly with the pitch axis set of fins not attached. Note the square tubing inside the pivot bearing that they plug into. And the 1/16" music wire spar that is inside one of the nose fins and slips inside of the other one , when both are plugged into the bearing assembly.



Two views with the nose fins all in place.

Two big problems in this video.

PVC is a terrible choice for motor cases. I know you keep mentioning using PVC for the body of the rocket, but please, please, please do not use it for the motor case like this guy did. If a motor fails, and even commercially made motors like Estes will fail on rare occasions, the propellant can explode. I have seen a number of Estes motors fail. Since the Estes motor case is paper it doesn't shatter. If a motor inside a PVC case fails, the case will shatter and small pieces will fly in all directions - some of them towards you! The best motor cases are made from aluminum. Aluminum is light weight, very strong and best of all, it will not shatter. Aluminum rips when it fails. There is no shrapnel like you would have from a PVC case (or a steel case).

And since PVC is a terrible choice for motor cases you can also see one reason why it is not a good choice for the body of the rocket; especially the part of the rocket with the motor in it. If the motor fails the rocket could be damaged and send shrapnel flying towards you.

There are two large rocketry organizations in the U.S. The National Association of Rocketry (known as NAR) would never allow the motor this guy made to be used at one of their launches. For safety reasons, NAR only allows commercially made motors, like those made by Estes and Aerotech. The other organization, Tripoli, allows sugar and other homemade motors, but only if the member is at least level 2 high-powered certified. Becoming level 2 certified is not an easy thing to do, so only very experienced people are allowed to make their own motors and fly them. I do not belong to Tripoli, but I believe they would not allow the motor used in the video to be used at one of their launches because of the PVC case.

Also PVC won't be easily spotted in x-rays.

Tripoli allows "sugar" at their research launches but not sucrose (table sugar). The only allowed sugars are dextrose, sorbitol, and erythritol


Just because it's on YouTube doesn't mean it's a good idea...

For a motor case look here:

https://lokiresearch.com/secure/store.asp?groupid=5520031443530

The 38/120 will get you close to where you want to be. Maybe a little more.

Danh said:

Tripoli allows "sugar" at their research launches but not sucrose (table sugar). The only allowed sugars are dextrose, sorbitol, and erythritol


Just because it's on YouTube doesn't mean it's a good idea...

For a motor case look here:

https://lokiresearch.com/secure/store.asp?groupid=5520031443530

The 38/120 will get you close to where you want to be. Maybe a little more.

Click to expand...

What about the PVC motor case? As I said in my previous post, I do not belong to Tripoli so I don't know.

No they don't allow pvc cases.