Rocketry Warehouse Mongoose 54 build thread by CW

[Crash-n-Burn]

You can also Daisy chain the extensions together, I actually flew a couple weekends ago using 4. My rocket is designed to fit a pro98 6gxl and I flew it with a pro54 4g. I had to make a special centering ring for the extensions so that i could actually screw everything together. Also, if you do this you MUST make sure there is a thrust plate at the base to transfer the motor thrust into the airframe, otherwise the rods can buckle when they are that long, and bad things will happen.

Good call. I believe you are saying that all thread only serves for motor retention, not thrust. I'm going to use the all thread for motor retention only; for thrust I'll put an Aeropack 54/38mm adapter over the motor case for the smaller motors.

 

[ksaves2]

Good call. I believe you are saying that all thread only serves for motor retention, not thrust. I'm going to use the all thread for motor retention only; for thrust I'll put an Aeropack 54/38mm adapter over the motor case for the smaller motors.

As long at your motor has an aft thrust ring in contact with your airframe, that is true. The forward connection only has to be robust enough to hold the motor in place and take the transient pressure increase of ejection charge actuation. Kurt

 

[cwbullet]

I agree. Pressure changes are the true issue. Tape will work. It can be a dickens to get a motor out but it will work.

 

[Crash-n-Burn]

As long at your motor has an aft thrust ring in contact with your airframe, that is true. The forward connection only has to be robust enough to hold the motor in place and take the transient pressure increase of ejection charge actuation. Kurt

Which motors don't have an aft thrust ring? I'm really only familiar with AT and CTI (and the usual DMS suspects).

 

[Crash-n-Burn]

I agree. Pressure changes are the true issue. Tape will work. It can be a dickens to get a motor out but it will work.

So you will use tape to friction fit the motor bulkhead in place in order to counteract the ejection charge?

 

[cwbullet]

No, I am going to use an aeropack minimum diameter. I was acknowledging pressure changes can push out the motor.

 

[ksaves2]

Which motors don't have an aft thrust ring? I'm really only familiar with AT and CTI (and the usual DMS suspects).

Not common anymore but Dr. Kosdon didn't believe in thrust rings. Had to have an engine block and all thread that could take the load.

 

[mpitfield]

You can also Daisy chain the extensions together, I actually flew a couple weekends ago using 4. My rocket is designed to fit a pro98 6gxl and I flew it with a pro54 4g. I had to make a special centering ring for the extensions so that i could actually screw everything together. Also, if you do this you MUST make sure there is a thrust plate at the base to transfer the motor thrust into the airframe, otherwise the rods can buckle when they are that long, and bad things will happen.

I have the complete set of extensions from Aeropack and originally I was thinking of doing the same thing, daisy chaining them. However I decided against this as I found it much simpler to cut a single length of threaded rod, less parts.

 

[woferry]

I have the complete set of extensions from Aeropack and originally I was thinking of doing the same thing, daisy chaining them. However I decided against this as I found it much simpler to cut a single length of threaded rod, less parts.

Indeed. Less parts, and perhaps more importantly fewer places where things might start to come loose other than where you want it to. I bought the full set of M1E* extenders, but have since replaced them with lengths of a 5/16-18 rod I bought at a local hardware store. Comparing weights the single piece of rod comes in lighter than the equivalent length of Aero Pack extenders. The coupler nuts I found felt quite heavy, but the single rod saved enough weight that overall it was still lighter. And I don't have to figure out which combination is right for the motor I'm flying, each one is marked for the case/load size (and rocket) it goes with. Also means I can epoxy the coupler nut to the extender since it never needs to be re-configured to a different length.

I just wish it was easier to find aluminum equivalents, this really doesn't seem to need steel since it's not really dealing with any force. Heck, something like nylon would probably work fine also, at least provided you're not using the motor eject bypass on the AT/38mm MD parts.

 

[Wayco]

I got the full set of extenders with the Aeropac MD retainer when I built my first MD Blackhawk. I don't use either any more. McMaster-Carr sells 5/16" aluminum allthread in a variety of lengths, I usually get it in 3 ft:
https://www.mcmaster.com/#94435a342/=zpeale

The Mongoose 40" fincan tube is 5" longer than the Blackhawk tube, which gives you more room for the bulky Aeropac MD retainer, but the kit comes with a much better solution to the motor retention issue. The two short coupler pieces and CF bulkplate can be made into a nice short and light retainer. I posted pic's of mine in Kurt's thread, as he mentioned. Here it is again:

You could use both short pieces of coupler, I never thought it was necessary.
I also mentioned in Kurt's thread that I was considering doing a build thread on this rocket, but I haven't found the time to start it yet. If Chuck doesn't mind, I will add in my comments and pic's to the "committee" build here.

 

[Buckeye]

The Mongoose 40" fincan tube is 5" longer than the Blackhawk tube, which gives you more room for the bulky Aeropac MD retainer, but the kit comes with a much better solution to the motor retention issue. The two short coupler pieces and CF bulkplate can be made into a nice short and light retainer.

How do you prefer to secure this retainer in the rocket?

 

[Rocketjunkie]

Mcmaster-Carr carries aluminum threaded rod in sizes from 0-80 to 3/4-10. Catalog page is 3172.

 

[Wayco]

How do you prefer to secure this retainer in the rocket?

Pem nuts, search one of my build threads for more info. I also laid it out in ksaves thread:
https://www.rocketryforum.com/showthread.php?129717-Hump-Day-Happy-Hour-Mongoose-54

Mcmaster-Carr carries aluminum threaded rod in sizes from 0-80 to 3/4-10. Catalog page is 3172.

Yeah, I covered that in my previous post:

I got the full set of extenders with the Aeropac MD retainer when I built my first MD Blackhawk. I don't use either any more. McMaster-Carr sells 5/16" aluminum allthread in a variety of lengths, I usually get it in 3 ft:
https://www.mcmaster.com/#94435a342/=zpeale

 

[cwbullet]

Now, How much space did you leave from the bottom for the motor? How much of a motor? the 6G XL is 25" long.

 

[mpitfield]

Now, How much space did you leave from the bottom for the motor? How much of a motor? the 6G XL is 25" long.

The best way to line everything up is to get all the pieces then mock it all up and lay it beside the tube then measure and mark from there. When I laid out mine I screwed the motor roughly 75% into the thread on the retainer or a couple of turns backed out, this allows a bit of tightening up.

 

[Wayco]

Now, How much space did you leave from the bottom for the motor? How much of a motor? the 6G XL is 25" long.

I know some of you don't have L935's laying around, so here is where a CTI 6XL casing lines up with the Aeropac adapter and my retainer. The rear closure is butted up against the bottom of the tube for that measurement.

Sharon picked up a couple of 54mm snap ring cases, one is a Kosden 2650. It's 3" longer than the 6XL casing in that picture. Since the Mongoose has the room, I actually plan to move the retainer up for that motor on my Mongoose 54.
I really am trying to find time to do this build, but this week work in the office has been overwhelming. Self employment is not for the faint of heart. When the work is on the desk, even your weekends are compromised. Hopefully, I can start this build next week. When I do, I will post a link here and on Kurt's thread.

 

[cwbullet]

This is similar to what I plan to do. I think I am going to tap the Aeropack or Bulkhead and hold it in place with screws. I would like to be able to remove it if needed.

 

[patelldp]

Tape! It's truly adaptable with no limitations. In addition to taping the OD of the motor case, a wrap of aluminum insultation tape (from Lowes, etc.) around the aft end of the rocket and over the aft of the case will provide additional security and may aid in tracking the flight.

 

[ksaves2]

This is similar to what I plan to do. I think I am going to tap the Aeropack or Bulkhead and hold it in place with screws. I would like to be able to remove it if needed.

Chuck,

Did you get the Aeropack? I have one and it's somewhat floppy in the tube. I think the coupler arrangement would be more secure. If yours fits with
little play, you should be able to drill and tap it o.k. Kurt Savegnago

 

[cwbullet]

I have one. I need to dig it out and test it before I start building.

 

[4kids49]

Very true as long as the motor as a 5/16 thread. I chose aluminum to save weight.

McMaster Carr sells reducers so that you can go from AeroPack extensions (or your custom extension) to 1/4 inch or whatever. This is useful for going to CTI tapped motors like the K300 which does not fit the AeroPack MD retainer or extensions. You have to account for the extra space of the coupler in your motor / retainer configuration. I can dig up part numbers if anyone is interested. The couplers give maximum flexibility for your extensions.

 

[cwbullet]

Chris: I am interested.

 

[Wayco]

McMaster Carr sells reducers so that you can go from AeroPack extensions (or your custom extension) to 1/4 inch or whatever. This is useful for going to CTI tapped motors like the K300 which does not fit the AeroPack MD retainer or extensions. You have to account for the extra space of the coupler in your motor / retainer configuration. I can dig up part numbers if anyone is interested. The couplers give maximum flexibility for your extensions.

This is news to me, and I'm also interested in it. I have a forward closure for a snap ring motor with a 3/8" thread. Might be able to adapt it down to 5/16" for my retainer.

 

[4kids49]

Here is a link to a photo in my Space Cowboy Build thread:

https://www.rocketryforum.com/showthread.php?66281-My-Badd-Azz-Space-Cowboy&highlight=space+cowboy (see posts #8 - 10)

There are two couplers from McMaster Carr. One is a single piece unit, and one is a two piece unit.

The couplers are reducing couplers from McMaster-Carr. The one piece unit is part # 92499A154 18-8 Stainless Steel Male-Female Thread Adapter, 1/4"-20 male end, 5/16" Female end. Idea from TRF. Two piece unit is part # 98434A110 Reducing coupling nut, 1/4"-20 & 5/16 "-18 size, 1 " length, 7/16" width. The screw is part # 94355A548 Nonmarring Flat Point Socket Set Screw, 18-8 stainless steel, 1/4"-20 thread, 1" long, pack of 10. Idea from Aero Pack.

There are probably other thread sizes available from McMaster-Carr. These fit my needs to match the AeroPack MD retainer and extensions with the CTI tapped closures. On a related note, The standard AMW 2550 tapped closure does not fit the AeroPack MD retainer and extensions. One can either use a coupler, or request the non standard tapped forward closure from AMW that fits the AeroPack stuff. AMW has them for sale. I hope that this helps.

 

[4kids49]

This is news to me, and I'm also interested in it. I have a forward closure for a snap ring motor with a 3/8" thread. Might be able to adapt it down to 5/16" for my retainer.

Wayco,

The two piece coupler might work for you:

https://www.mcmaster.com/#catalog/121/3205/=zq6dep

There is a 5/16" to 3/8" female to female coupler available. Add the appropriate male piece, and you should be good to go.

 

[ksaves2]

Wayco,

The two piece coupler might work for you:

https://www.mcmaster.com/#catalog/121/3205/=zq6dep

There is a 5/16" to 3/8" female to female coupler available. Add the appropriate male piece, and you should be good to go.

Eureka! Just what would be needed to adapt motors with different thread size in the forward closure to Aeropack
or anything. Wow. Kurt Savegnago

 

[Wayco]

Wayco,

The two piece coupler might work for you:

https://www.mcmaster.com/#catalog/121/3205/=zq6dep

There is a 5/16" to 3/8" female to female coupler available. Add the appropriate male piece, and you should be good to go.

Thanks Chris, that place is amazing! I have spent hours clicking around on their website and still find stuff I never knew about.

 

[4kids49]

Eureka! Just what would be needed to adapt motors with different thread size in the forward closure to Aeropack
or anything. Wow. Kurt Savegnago

Thanks Chris, that place is amazing! I have spent hours clicking around on their website and still find stuff I never knew about.

Thanks Guys. Glad to help. If you use the two piece coupler, you might consider putting some Loctite on the male threaded rod. Parts of the coupler could get left up in the booster when you remove the motor. AeroPack told me about the two piece coupler. Someone on TRF told me about the single piece unit.

 

[4kids49]

CW, I built a MD 38mm scratch rocket and used a Slimline. I also used Aeropoxy lightweight filler to make an aerodynamic, smooth transition to the Slimline. In terms of max altitude, it consistently fails to achieve the same or similar heights as a Blackhawk 38 without an external retainer, sometimes by quite a bit. And, the fins are airfoiled, it has a VK nosecone and airframe smoothed out really well.

I built my Madcow Tomach with the Aeropack MD motor retainer. It works well, but getting everything to unscrew right is a trick, and a little temp thread locker in strategic points helps a lot in getting the assembly out. Performance is awesome--got 14.4k on a K805G first flight (also used AT tailcone aft closure).


Is the weight of your scratch build similar to the Black Hawk? I am wondering if what you are seeing is a heavier rocket going higher? Madcow Tomach is not super light eiither.

I'd recommend the Aeropack MD motor retainer, but shove that puppy as high up as the longest motor will require.

As for the 38mm option on a 54mm rocket, why? 54mm motors already range from the 54/426 I to a 54/2800 L. What would a 38mm motor add that you cannot already do with a 54mm version?

I agree with Chuck that it is nice to have 38 mm capabilities. I have a special 38 mm tailcone adapter from BaddAzz[ that screws in to the aft end. There is an additional piece that screws into the booster a little higher up to hold a 38 mm motor. These pieces screw out in order to use the AeroPack MD retainer for 54 mm. I lost my first Space Cowboy on a K300, but still have the retainer for the new one that I am building. I don't know how much out of my way that I would go to get 38 mm capabilities, but since I have them already, it is a nice option to have. /COLOR]

 

[Brent]

Just noticed that Giant Leap has a 54/38 tail cone. May not be to hard making an adapter with one of them.