Rocketry Warehouse Mongoose 54 build thread by CW

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Cant wait for mine to come in. It will be my first all carbon build.
 
All eyes on you, Chuck. Lots of us, including me, have one of these coming in the mail. Show us how it's done.
 
Hey guy's, ,
I'd like to ask a question. ..
I built a scratch 38 mm minimum d a couple of years ago..
used a epoxies in internal Aeropack retainer,,
with the 5/16" adapters,, flew primarily Aerotech motors..
All worked great.. Great flying rocket..
I am now interested in building another minimum diameter rocket..
I want to make my own internal retainer,, same principle.....
One big catch,,,
I now have great interest in snap ring hardware...
The forward enclosure isn't threaded into the case..
I don't want to think about getting a case bound up on the thread,, can't get it out...
the only solution I can think of is to not epoxy in the retainer,,
3 blind nuts 120 degrees apart and it's removable. ..
But I didn't want to drill the airframe, ,, didn't want to compromise, , or weaken it....
Now that I type this, I don't think it'll really weaken the airframe much..
Especially with the coupler screwed to it internally....

Thanks for listening guys.....

Teddy
 
A few screws won't compromise your airframe strength. Also with snap ring hardware you do have threaded forward closure options. Most likely would not spin when unscrewing, but if you are worried about it a strip of aluminum tape wrapped/oriented opposite of unscrewing direction will keep it in place.
 
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I picked up one of these this weekend. Thus far, I've just been running sims in OR. Holy crap! This is going to be awesome.
 
Freds method of motor retention is the way to go: https://www.rocketryforum.com/showt...e-54-build-thread-by-CW&p=1515764#post1515764

He's done this before. The aft thrust ring on the motor case imparts the load to the airframe and the
forward retention is just to hold the case in. Makes sense to me as this takes less of a load as long as the motor thrust ring touches the airframe. The "thrust-ring-less" motors made by Dr. Kosdon would take a beefier forward retention device because that's where the thrust load is imparted to the airframe. Otherwise the motor could "fly up the pipe".

IMG_20151129_091905.jpgIMG_20151129_091918.jpgIMG_20151129_091929.jpg

Case is symmetrical so doesn't matter which end is forward or aft. The internal thrust block would have to be substantial. Practically all of the commercial cases now have thrust rings of some kind so forward retention doesn't have to handle the thrust loads.

Plus, I looked quickly and the pieces are supplied with the collection of parts I received
with the Mongoose 54 and I believe they're there for retention purposes. Only need is to purchase/acquire the all-thread or screw needed to fit one's threaded closure.

Since the retention device is removeable, if one wished to use different motors that have
different threads, just drill the largest hole for the biggest screw/all-thread required and use
an insert for when a smaller screw/all-thread is needed. Of course if just using one manufacturer's case, no problem.

I like that method though haven't tried it yet. I did epoxy the Aeropack forward retention device in two 38mm projects. I have to be fastidious with shockcord protection because
once they're toasted, that's the end of life of the airframe. One was cardboard tubed so I
don't know if screws would have been workable anyways.

One technique for shockcord/harness protection besides using a nomex protector is soaking
some cardboard in boric acid/borax fireproofing solution. Let dry. Yeah it curls or "warps" a little bit but one can cut a strip and slide it down so it protects "the shockcord protector".

This is with the apogee charge located aft in front of the forward closure. The cardboard is disposable and takes the brunt of the flash and saves the pricey protector for secondary "protection".:rolleyes: How to I know? I've burned up a shockcord protector during a ground test using a too aggressive of charge.

The treated cardboard can also be used as a fireproof divider inside the airframe to help prevent harness tangling on deployment. Kurt Savegnago
 
Your 100% right,,
I was thinking about that..
If I didn't have the thrust ring seated firmly against the aft edge of the airframe
all of the thrust would be directed to the 3 screws holding in the internal retainer...
Prolly not good...

Teddy
 
I did epoxy the Aeropack forward retention device in two 38mm projects. I have to be fastidious with shockcord protection because
once they're toasted, that's the end of life of the airframe.

Why couldn't you use a long Kevlar loop as a harness expending out the airframe? If the Kevlar begins to weaken just cut it and install another by threading it through the eyebolt with fish wire of appropriate gauge. Tie off and your good to go again.
 
I will be interested the full range of ideas on this one, I have a Mongoose 54CF and a CF and FG Mongoose 75 to build.
 
I think the idea is: Eye Bolt -> Loop of Kevlar -> Shock Cord

The loop would be long enough that the shock cord attaches past the body tube opening. So you could inspect the entire loop to see when it needs to be replaced, and when it needs to be replaced you just untie/cut the loop and attach a new piece to it, fish the new piece in while you pull the old one out, then tie off the new piece to make the new loop. Sort of a giant kevlar quick-link. :) I never considered that, but it sounds like a really good idea to me. When I put the M38E in my 38mm MD I tied a knot at the end of the cord around a small quick-link, then fed the other end of the cord through the eye-bolt and then the quick-link (the quick-link is NOT attached directly to the eye-bolt), so it's secured inside but all I'd need to do is fish a hook down the tube and snag the quick-link and I should be able to pull it out, getting access to the quick-link and the end of the shock cord (in theory, I haven't tried it yet and I'm not doing motor eject, my MD retainer doesn't even have bypass holes, so there shouldn't be any reason for BP contamination at that end of my drogue bay anyhow). Similar idea, but the idea above wouldn't require any fishing, it does put a bit more shock cord in the tube though. I have a few more kits to build after this weekend, I'll likely give the above idea a shot.
 
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I think the idea is: Eye Bolt -> Loop of Kevlar -> Shock Cord

The loop would be long enough that the shock cord attaches past the body tube opening. So you could inspect the entire loop to see when it needs to be replaced, and when it needs to be replaced you just untie/cut the loop and attach a new piece to it, fish the new piece in while you pull the old one out, then tie off the new piece to make the new loop. Sort of a giant kevlar quick-link. :) I never considered that, but it sounds like a really good idea to me. When I put the M38E in my 38mm MD I tied a knot at the end of the cord around a small quick-link, then fed the other end of the cord through the eye-bolt and then the quick-link (the quick-link is NOT attached directly to the eye-bolt), so it's secured inside but all I'd need to do is fish a hook down the tube and snag the quick-link and I should be able to pull it out, getting access to the quick-link and the end of the shock cord (in theory, I haven't tried it yet and I'm not doing motor eject, my MD retainer doesn't even have bypass holes, so there shouldn't be any reason for BP contamination at that end of my drogue bay anyhow). Similar idea, but the idea above wouldn't require any fishing, it does put a bit more shock cord in the tube though. I have a few more kits to build after this weekend, I'll likely give the above idea a shot.

This is correct.
 
This thread is making me excited to build my own Mongoose. And makes me realize I need to think about getting into snap ring cases so I can use it as the sustainer in a two stage flight. :)
 
It will do just short of 10,000 on a J135. I have started and will begin posting photos next weekend. I need some aluminum all thread and couplers to build my retention.
 
Nice build Chuck. I will be interested to see how you do your av-bay and trackers.
 
I will use and RRC3 and an RF tracker. I may use a Missileworks AV sled.
 
I think the idea is: Eye Bolt -> Loop of Kevlar -> Shock Cord

The loop would be long enough that the shock cord attaches past the body tube opening. So you could inspect the entire loop to see when it needs to be replaced, and when it needs to be replaced you just untie/cut the loop and attach a new piece to it, fish the new piece in while you pull the old one out, then tie off the new piece to make the new loop. Sort of a giant kevlar quick-link. :) I never considered that, but it sounds like a really good idea to me. When I put the M38E in my 38mm MD I tied a knot at the end of the cord around a small quick-link, then fed the other end of the cord through the eye-bolt and then the quick-link (the quick-link is NOT attached directly to the eye-bolt), so it's secured inside but all I'd need to do is fish a hook down the tube and snag the quick-link and I should be able to pull it out, getting access to the quick-link and the end of the shock cord (in theory, I haven't tried it yet and I'm not doing motor eject, my MD retainer doesn't even have bypass holes, so there shouldn't be any reason for BP contamination at that end of my drogue bay anyhow). Similar idea, but the idea above wouldn't require any fishing, it does put a bit more shock cord in the tube though. I have a few more kits to build after this weekend, I'll likely give the above idea a shot.

Ahhhhhh,

O.K. Sheeeeoooooot.:facepalm: Stupidhead here shoulda done that in the first place!!:bangpan: Makes sense. Well if the time comes, the rockets last a long time and I don't lose them, maybe I can cut off the straight attached kevlar tape as far in as I can, bend a stiff piece of thick piano wire into a "hockey stick" shape, skewer a new piece of kevlar tape and get it through the eyelet of the eyebolt. I can try to "skewer" the tail on the other side of the eyebolt with another "hockey stick" thick piano wire thingie and pull up the end to make a loop. Any of the straight remnant remaining just stuff in the bottom. Thanks for getting my brain straight. :wink: Kurt Savegnago
 
I will use and RRC3 and an RF tracker. I may use a Missileworks AV sled.

Those solutions would simplify your build and launches. Ramming a second altimeter in is a bit stressful. I am not sure how necessary a second altimeter really is.
 
I picked-up a Mongoose 54R2 from RW's Black Friday sale, and plan to use the AreoPack MD retainer, extensions, and delay/ejection adapters for 38 & 54mm motors. For versatility, I've developed RockSim models for both 38 & 54mm CTI motors.

I'm looking at using a 15" drogue (that may, or may not be used) and a 48" main chute deployed at 400' - running various simulations for high altitudes and short recovery distances.

I haven't gotten the kit yet, but am looking forward to working on it... :)
 
So far I see that MD motor retention has been discussed quite a bit. But what about launch rail guides? Is everyone going to use a 54mm fly-away guide? If not, what are you going to use?
 
So far I see that MD motor retention has been discussed quite a bit. But what about launch rail guides? Is everyone going to use a 54mm fly-away guide? If not, what are you going to use?

Well, you can get free shipping on them today... :)
 
The fly-away rail guides are very, very handy. Definitely higher rail drag than a tower, but it's so easy to just throw it on the rail. I've got a 38 set and a 54 set, but I'd just caution that they are a bit fragile. My 38 set broke on the third flight. :(
 
So far I see that MD motor retention has been discussed quite a bit. But what about launch rail guides? Is everyone going to use a 54mm fly-away guide? If not, what are you going to use?

Launch tower.

What he said, although I have a set of the fly away guides that I haven't used yet....

Since you went back and read about retention, you know that the kit comes with a bulkplate and short couplers that allow you to make your own. Not only is it cheaper, but it's also smaller and lighter than the Aeropac retainer. You do need a small u-bolt and a 5/16" nut, but that is still less expensive than the Aeropac. I also think the Aeropac extensions are a waste of money. Cut your own from 5/16" allthread, McMaster-Carr has aluminum allthread for about $7 for a three foot length:

https://www.mcmaster.com/#standard-threaded-rods/=101aqg6

I laid all this out in ksaves thread here if you want more info:
https://www.rocketryforum.com/showthread.php?129717-Hump-Day-Happy-Hour-Mongoose-54
 
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