MEGA-Gyroc - 4" dia. 5.3x Upscale

[eugenefl]

I've nearly acquired all of the parts now. Tomorrow I'll start assembling the motor mount. The nosecone should arrive sometime next week. Once the mount is done I get to agonize over the construction of the fins.

Attached is a closeup of the rings being used in this project. From left to right: solid bulkhead (the pilot hole will be plugged with a wooden dowel), aft centering ring with dowel "keys", forward "slip" ring with holes to assist in pressurizing the lower cavity, aft "trap" ring with matching holes for aft ring.

 

[eugenefl]

Here is a simple parts layout picture. I constructed some rough tube couplers out of 4" shipping tubes. The longest of the couplers is the only coupler that connects 2 pieces of airframe. It will be fiberglassed internally for added strength. The other 2 couplers will function as reinforcement parts.

 

[eugenefl]

And for those anxious to see how much bigger this version really is, I've taken a picture of the work-in-progress next to my 2.6x upscale. This is going to be one BIG rocket!

 

[powderburner]

eugene,

Just a thought, but your forward slip ring is supposed to allow the ejection gas through, right? (It pushes the motor pod out the rear?) Why not make sure (a little more) that the gas can get through freely by making those holes a bit larger, or making more of them? Like I said, just a thought.

As far as the motor pod getting hung up and adding weight to the descending rocket; I just don't think that is going to be a problem for you. Once that motor mount moves the first inch or so, it is going to be VERY loose, and free to fall out. (The first 1/4 inch releases the back end, and the next inch or so releases the front end, and I think ejection pressure will take care of that quite handily). The only suggestion I can think of is to maybe move the forward slip ring a bit farther forward, so that the motor pod completely clears the main part of the rocket a bit sooner?

 

[powderburner]

You could eliminate the forward slip ring entirely, and seat the front end of the motor mount tube into a short piece of BT mounted on the solid bulkhead (and sealed on that blkhd). The ejection charge would have only a tiny place to pressurize, and would CERTAINLY get the motor pod moving aft. This would be a little lighter approach for the main rocket, eliminating a plywood bulkhead (that you have already constructed).

 

[eugenefl]

Originally posted by powderburner
eugene,

Why not make sure (a little more) that the gas can get through freely by making those holes a bit larger, or making more of them? Like I said, just a thought.

As far as the motor pod getting hung up and adding weight to the descending rocket; I just don't think that is going to be a problem for you. ............maybe move the forward slip ring a bit farther forward, so that the motor pod completely clears the main part of the rocket a bit sooner?

If you would reference the MMT diagram, the MMT inner area is split into 1/4 forward cavity and 3/4 aft cavity. I had considered keeping the forward 1/4 cavity sealed with the slip ring having no vent holes. Then I started to worry about the ejection charge blowing a hole in the side of the airframe or possibly eroding and weakening the area more quickly. With the holes in the slip ring, the pressure between both cavities will equalize and place most of the pressure on the actual MMT tube. Of course, a lot of pressure will escape into the aft cavity and force the aft CR out. I suppose I am trying to find a balance between protecting the forward inner airframe and maintaining rigidity in the fore slip ring.

The fore slip ring will only allow about a 1/4" of motor tube to pass through it. I think the scaling on the diagram shows a lot more tube going through it. In construction, there will be little tubing going through the fore slip CR. All in all, the MMT components will have to clear just over 1/4" before the mount is absolutely free of the flaps and clear to free fall out the back.

 

[eugenefl]

Originally posted by powderburner
You could eliminate the forward slip ring entirely, and seat the front end of the motor mount tube into a short piece of BT mounted on the solid bulkhead (and sealed on that blkhd). The ejection charge would have only a tiny place to pressurize, and would CERTAINLY get the motor pod moving aft. This would be a little lighter approach for the main rocket, eliminating a plywood bulkhead (that you have already constructed).

I had actually done this for my 2.6x upscale version. Unfortunately, after only 2-3 flights, the tube coupler and MMT tube are charred and peeling. A few more flights and there won't be much left. See attached diagram.

 

[eugenefl]

Originally posted by eugenefl
I just ordered the nosecone.

I'm still waiting on the nosecone. Either RGM doesn't have them in stock or they are fabricated upon every order. Either way, I still haven't heard from them. Based on the order date, it's been 19 days and still no word. Should I be patient or start panicking? I just hate the silence. Near 3 weeks is a bit long I'd say...

EDIT - I just sent a friendly Email inquiry and received a response right away:

"I 'm sorry not to make excuses but -- family passing and ......etc. I have lost some email switching to a temp out of town dial-up.. It's on the way..."

It is rather unfortunate to have our vendors running up on bad times. My contention is that so long as the vendor actively makes an effort to either inform the customer of the delay or temporarily suspend operations if unable to continue to provide service, they've done their part. Hopefully I will receive the cone soon.

More work WITH pictures of the MEGA-Gyroc build to come shortly!

 

[eugenefl]

FYI - Still on hold and waiting for the nosecone. It's been exactly a month now. I just hope everything is OK over at RGM.

 

[eugenefl]

So, does anyone out there remember this thread?

With the dust blown, I have decided to resume this project. One of the original things that took the wind out of my sails on this project was waiting for the nosecone. It took a VERY long time to get to me, but alas it finally had. By that time I had a lot going on that I didn't do much rocket building. So where does that leave me? BUILDING!

Here are some of the picture of the MMT.

The first shot is of the internal front "vent" CR and the aft "stop" ring.

 

[eugenefl]

I flipped the lower MMT assembly around to show the "chamber" (forward end) that will pressurize and force the MMT pod to eject out of the rear. Ahead of this "filter" or "venting" ring will be 2 solid bulkheads.

 

[eugenefl]

Here is the actual MMT or "pod" that will eject out the rear thus releasing the flaps. Notice that it has a "stop collar" and "pins" to keep the MMT from rotating freely.

 

[eugenefl]

Here's how the MMT/pod looks when assembled for flight. To finish this MMT/pod, I'll add a 38mm Aeropack retainer (or Kaplow Klips - not sure yet), flap tabs, and a recovery system for the ejected pod.

 

[eugenefl]

And here are the parts including the nosecone.


What I really need help with is constructing the fins and flaps. I know that I'll end up fiberglassing whatever material I use, but in the end it'll need to be very light. Any suggestions? All of the hobby grade aircraft ply I look at is warped.

 

[wyldbill]

Build up your own fin stock from rohacell and glass or (preferably) carbon. 51 is probably best. Use a foodsaver if you've got one to vacuum bag the stock to make sure you have a minimum of epoxy. I've build very light very rigid fins this way. Make sure too finish the edges after cutting to prevent delam.

see:
https://www.cstsales.com/CMRohacellFoam.htm

FWIW,
-bill