Rear Ejection?

[TangoJuliet]

I saw an enlarged Estes Mosquito using the Baby Bertha for parts that used Rear Ejection. I liked the thought, especially for Spot Landing and thought I'd build one, but I've never done rear ejection and I'm not sure how to handle an internal thrust ring for the entire engine mount. Photo examples would be much appreciated.

 

[Cabernut]

Here's how I did it on mine.

Shorty-R

 

[Micromeister]

Heres how I converted several of my Mosquito's to rear pod eject micro maxx power.

The only trick is to install a long strong shockcord protected from the Exhaust gases. I usually add a 1/4" balsa block faced with two layers of Stainless Steel adhesive backed tape. 100lb kevlar shockline even on MMX power pods. The shockcord is packed into the forward end of the body, a sheet or two of loose wadding is added, then the power pod is seated with the recovery system wrapped tightly between the fore & aft power pod centering rings. OH! the pod is tied to the shockcord as usual around the motor tube behind the forward centering ring.

Recovery can be either Chute or Streamer dependent on the space between the motor mount tube & the size of the centering rings.
I've used various rear ejection set ups on lots of Rockets and Many PMC's, They work well as long as there is no binding between centering rings and the inner body tube walls, Cleaning build up residue after flights is a good way to ensure proper ejection.

 

[TangoJuliet]

Cabernut - The interior photo helped a lot. I won't have a tapered exhaust like you used for a thrust ring, so I was thinking maybe an internal coupler would act like a thrust ring against the forward centering ring on the MMT.

Micromeister - I understand the concept of rear ejection, my question was more about how to create a thrust ring that doesn't impede the insertion and removal of the MMT from the back. The V-2 image won't enlarge any more to get a clear look at what you've done there.

 

[Screaminhelo]

I have an OpenRocket file of the Estes Sizzler that may give you some ideas.

View attachment Estes_sizzler_2127_mod.ork

 

[bill_s]

I've been attaching the shock cord on the outside of the rocket, through a small notch in the rear ring. It's possible to have the cord inside but protection is critical and no I don't use all-Kevlar shock cords I'm an engineer. The motor mount mount thrust ring (not redundant there) is just a piece of coupler.

These rockets basically don't need dual deploy, they come down fast. A retired one had a bumper nose, the next one is very pointy and so far has landed on mostly dirt, providing a shock absorber, and on the last the nose cone is biggest part of the rocket and demands to be landed on (with a bomb-like shape it also looks right doing so). That second one weighs about 1 pound without motor and comes down on a 18" 6 line 'chute.

 

[TangoJuliet]

By chance, I just acquired the rear ejection Estes Sizzler yesterday as part of a "Lot" of kits I purchased. I may need to build that one as well. But I think I've got my dilemma figured out. Thank you gentleman for your input.

 

[Micromeister]

Perhaps this rear-ejection pod sketch will help a little. This one is for a minimum diameter Slip pod used in a rear ejection PMC.. It's a lot easier to use Heavy cardboard centering rings and a small section of the body tube as the "stop ring" at the bottom of the pod.

This sketched pod also required the chute or streamer to be dragged out by the ejection charge. This is tricky as too much friction will cause the recovery system to not be fully pulled out of the body causing a ballastic recovery.

Having the Chute or streamer rolled around the motor tube between the center rings is a Much more reliable deployment.

 

[MCriscione]

With this thread as inspiration, I think I'm going to go build myself a version of Cabernut's Shorty-R.

 

[Micromeister]

Cabernut - The interior photo helped a lot. I won't have a tapered exhaust like you used for a thrust ring, so I was thinking maybe an internal coupler would act like a thrust ring against the forward centering ring on the MMT.

Micromeister - I understand the concept of rear ejection, my question was more about how to create a thrust ring that doesn't impede the insertion and removal of the MMT from the back. The V-2 image won't enlarge any more to get a clear look at what you've done there.

Sorry for taking so long to fix the V-2 image. it's better now

 

[TangoJuliet]

Thanks Micro. I should have posted sooner myself. My model is complete and has flown twice in primer, with perfect results! It is now painted and awaiting a proper "Mosquito" decal from Stickershock!

 

[Zeus-cat]

I have a colonoscopy tomorrow and just drank the first dose of the prep. I'll be practicing rear ejection quite a bit tonight.

 

[TangoJuliet]

I have a colonoscopy tomorrow and just drank the first dose of the prep. I'll be practicing rear ejection quite a bit tonight.

:lol:... :eyepop:... :y:... :cry:

I hope you get good news.

 

[Zeus-cat]

:lol:... :eyepop:... :y:... :cry:

I hope you get good news.

Just one polyp and he removed it. He also said I had some "cobblestoning". I guess I will find out what that means in a few weeks when I have the follow up.

The worst parts were not being able to eat anything solid the day before and morning of the procedure. And of course, the stuff you have to drink to clean you out.

 

[TangoJuliet]

I don't know what "cobblestoning" means, but it doesn't sound nice. :eyepop:

 

[Micromeister]

I have a colonoscopy tomorrow and just drank the first dose of the prep. I'll be practicing rear ejection quite a bit tonight.

LOL! did exactly that last week! Good luck tomorrow. You'll be amazed at how quickly 8 - 8oz glassed of that stuff work LOL!