29mm Mean Machine

[gpoehlein]

I'm planning to build an Estes Mean Machine for use with an F motor - probably either a SU F20-7 or F23-7. However, the largest motor I've ever used before is an Estes E9. My question is, how long should the 29mm motor tube be, and what should I use for motor retention.

I plan to use it to fly F-Superroc at a local regional in a few months (I know it is only a bit over minimum length, but I'll be happy with flight points for the event), hence using SU motors - don't want to risk my one 24mm casing. Also, which of these motors do you guys think would be best?

 

[The EGE]

I'm planning to build an Estes Mean Machine for use with an F motor - probably either a SU F20-7 or F23-7. However, the largest motor I've ever used before is an Estes E9. My question is, how long should the 29mm motor tube be, and what should I use for motor retention.

The F20, F23, F27, and F27 Econojets are 3.28" (83mm) long.
The F25, F26, and F50 standard F motors are 3.88" (98mm) long.
All AT SU G motors are 4.88" (124mm) long.
The 29/40-120 case is 5.64" (143mm) long.

I would build the motor tube at least 6" long, so as to be able to fly up to G motors and the 29/40-120 case. All it costs you is a few inches of tube.

For motor retention, you have four options:
You can just use masking tape, which is cheap but not 100% reliable.
You can epoxy a threaded rod to the motor mount, but that might not work here because of the small gap between MMT and body tube.
You can use an Estes E motor hook and a spacer, but only for the F Econojets.
Or, you can use a commercial retainer system like Aeropack.

I plan to use it to fly F-Superroc at a local regional in a few months (I know it is only a bit over minimum length, but I'll be happy with flight points for the event), hence using SU motors - don't want to risk my one 24mm casing. Also, which of these motors do you guys think would be best?

For tracking - F20 or F23

For altitude - F42

 

[stickershock23]

I got to agree. once you go to 29mm forget the engine block. motor stops are not needed, there is a thrust ring on most 29mm's all you have to do is make sure they dont come out of the rocket!

 

[kandsrockets]

I put a 6" long 29mm motor mount in mine. I have flown mine on a few F motors. The last flight was on a F40 with no problems. I put a aeropack retainer on mine.

 

[Handeman]

Since the Mean Machine has 4 fins, you could put a loop of heavy wire (large paper clip) where the loop extends to the motor and the two legs are embedded in the fin fillets. One loop on opposite fins and use copper wire to wire the motor in place.

I used this on a altitude contest rocket I build. It worked quite well. It's light, low drag, strong and easy.

 

[kelltym88]

I used an old FSI 29mm MMT designed to be used in a BT-60 tube. I don't know how long it was, but 6" seems to be a good number. I have flown my 29mm MM on several motors ranging from F23 to G64. It last flight was on this:

 

[kelltym88]

Yep a G77 Redline. Shredded it. It was built pretty much stock, I guess I'd better glass the fins next time.

 

[gpoehlein]

Thanks for the ideas and suggestions, guys - this is exactly what I need. Keep them coming, since I don't have to build it for a few weeks yet and I've still got to order the motor tube any way.

Handeman: can you post any pics of that motor retention system? I'd like to see what you're talking about. Might be a good way to go. In any case, it sounds like I'm gonna have to order the motors so I know exactly what I'm gonna be modeling around.

If I use an F20 or F23 Econojet, should I go with the 4 or 7 second delay?

 

[Marlin523]

Are you a Rocksim user? If yes, I'd suggest running a few simulations to determine which delay is best for your rocket.

 

[kandsrockets]

Thanks for the ideas and suggestions, guys - this is exactly what I need. Keep them coming, since I don't have to build it for a few weeks yet and I've still got to order the motor tube any way.

Handeman: can you post any pics of that motor retention system? I'd like to see what you're talking about. Might be a good way to go. In any case, it sounds like I'm gonna have to order the motors so I know exactly what I'm gonna be modeling around.

If I use an F20 or F23 Econojet, should I go with the 4 or 7 second delay?

You will want a 7 delay for both.

F20-7 will give you 1900ft flight
F23FJ-7 will give you 1600ft flight

 

[gpoehlein]

You will want a 7 delay for both.

F20-7 will give you 1900ft flight
F23FJ-7 will give you 1600ft flight

Excellent - thanks for the info, Scott. Sounds like the F20-7 will be the way to go (I'm gonna have to trade model length for altitude for my score )

 

[Buckaroo]

Tha Apogee F10 is a 29mm contest certified motor, something like an 8 sec burn time IIRC...

 

[Handeman]

Handeman: can you post any pics of that motor retention system? I'd like to see what you're talking about. Might be a good way to go. In any case, it sounds like I'm gonna have to order the motors so I know exactly what I'm gonna be modeling around.

Here's the pics.

The first is just the rocket, the second is with a motor in place. I wired the motor in with a twist tie just as a demo. I usually use about a 20 - 22 ga copper wire. and snip off the extra where it's twisted.

I use heavy duty paper clips and bent the arms in a slight zig zag pattern, thinking a straight piece could pull out of the epoxy with enough force. I'm now thinking that would probably never happen, especially if I roughed up the arms of the wire loop. That would have made neater job of it.

BTW, this rocket was for an G altitude contest that required a 54mm minimum diameter somewhere on the rocket and positive motor retention. I build it like a baseball bat and put the lower rail button on a short fin. The other button is at the widest part near the nose cone. I got almost 3,400 ft on a G motor and won, so it didn't work to bad.

 

[barstoolmike]

I have one & cut the flange on two 6-32 T nuts to fit between the mount & body tube, tight fit but they fit. Glassed the rocket w/ a layer of 4 oz & put a bay & Missile Works RRC in it. Flew it on a G64, next planning on a small H.

Mike

 

[kandsrockets]

I have one & cut the flange on two 6-32 T nuts to fit between the mount & body tube, tight fit but they fit. Glassed the rocket w/ a layer of 4 oz & put a bay & Missile Works RRC in it. Flew it on a G64, next planning on a small H.

Mike

Mike do you mind posting pictures of your e-bay. I am going to build another MM but use 38mm motor tubing and want to make it DD.

 

[Thorn]

Mike do you mind posting pictures of your e-bay. I am going to build another MM but use 38mm motor tubing and want to make it DD.

I'll second this request. Mike's rocket sounds a lot like what I have planned.

I also commonly use 6/32nd T-nuts with one side ground to fit close to the motor tube. I then make clips from AL strips to use as motor retention. Works great!

 

[barstoolmike]

I'll see if I can get a couple photos when I get home from work today.

Mike

 

[barstoolmike]

Ok here are some photos of my altimeter bay.









Mike

 

[barstoolmike]

Being that it would only let me upload 5 at a time, here are some more.









Mike

 

[Thorn]

Ok here are some photos of my altimeter bay.

Thanks! That looks cool.

How long is the bay? It looks like it is about 9" down below the body tube section. Is there any reason you didn't use a longer section of body tube and shorter coupler tubes?

I've been worried that with one all-thread, the eyebolt would unscrew on the way down. Do you do anything special to stop that? (edit: I assume the eye bolt screws into the end of the all thread, right?)

 

[kandsrockets]

Thanks for the pictures.

 

[barstoolmike]

Thorn,

The bay is about 10" total length, 2" switch band & 6" lower coupler section. The switch band was postioned that high because it was about the only place to put the switches in that tight of a bay. The 6" coupler was more for support. With the length of the upper section & weight of the chute & recovery harness. If I shortened the lower coupler that would also put the weight of the altimeter above the top of the lower tube. (Just personal prefrence). As for the unscrewing of the eyebolt, The lower bulkhead is epoxied in place along with the allthread. Yes the upper eyebolt screws into the threaded coupler at the top of the allthread, but if you look at the photo of the forward bulkhead you can see a small eyescrew next to the eyebolt. After installing the eyebolt I use a zip tie from the eyebolt to the eyescrew to keep it from unthreading on the way down.


Mike

 

[Thorn]

Mike,

Thanks for the info, I hadn't thought the zip tie to keep the eyebolt from unscrewing, I like it. Now, I need to figure out how to get a Hi-Alt 45k working in that area...

Thanks for the info!

 

[barstoolmike]

My pleasure, glad I could help.
Good luck with yours.
Mike

 

[Neutronium95]

Cool Stuff! My venerable Mean Machine was destroyed last weekend when the parachute stripped. I hope to get building on a 29mm version soon.

 

[qquake2k]

I got to agree. once you go to 29mm forget the engine block. motor stops are not needed, there is a thrust ring on most 29mm's all you have to do is make sure they dont come out of the rocket!

Excuse my ignorance, but what do you mean "there is a thrust ring on most 29mm's"?

Jim

 

[TheAviator]

Excuse my ignorance, but what do you mean "there is a thrust ring on most 29mm's"?

Jim

Some of the 29mm single use motors and all of the 29mm reloadables have a thrust ring built into the motor, or a ring on the end of the motor that is larger in diameter than the motor itself. This is so that you can use different length reloads in a given rocket without adapters and so forth.

 

[qquake2k]

Some of the 29mm single use motors and all of the 29mm reloadables have a thrust ring built into the motor, or a ring on the end of the motor that is larger in diameter than the motor itself. This is so that you can use different length reloads in a given rocket without adapters and so forth.

Oh wow, I never knew that!

Jim

 

[gpoehlein]

Well, the regional contest with F-Superroc Altitude was this weekend - got to fly my 29mm Mean Machine today. I beefed it up a bit - put a baffle in the first coupler, covered the fins with label stock filleted the fins with epoxy. I put the break at two lengths of BT-60, so the rocket was two 18" lengths.

I flew it today on an F20-7 - the boost was arrow straight and the flight was perfect. It got a bit over 400 meters altitude and gave me second place in the contest. Unfortunately, it came down somewhere in the middle of a stretch of woods so the model is now lost.

Once again, thanks for all the suggestions - they really helped!

 

[ScrapDaddy]

Congrates on the win/loss!