AT 18/20 in Estes screw-type motor mounts

[wwattles]

I picked up an Estes "Metalizer" recently, and I wanted to fly it on an 18mm RMS, but there's a problem.

This particular rocket uses the plastic Estes fin can that has the built-in motor retention screw-on ring. So instead of having a standard motor hook, it uses a screw-on thing that slips over the entire back end of the motor.

The problem is that the aft closure on the RMS casing is larger than 18mm, so it can act like a thrust ring. It also means it doesn't fit into the provided retaining ring.

Without the retaining ring, the motor doesn't get centered properly, nor is it retained at all. I think I might be able to gin something up with a big piece of spent 24mm casing that will slip into the plastic fin can to provide some form of centering control, and also serve as an anchor point for some heavy-duty friction fitting tape.

I'm really not too fond of this plan. Anybody else use an AT 18/20 in a plastic fin can?

WW

 

[BR549]

I've been pondering this same question. I want to use my 18mm RMS in the RTF X-15. Haven't come up with a good solution yet.

 

[shreadvector]

Using a metal casing motor like an Aerotech RMS will MELT your plastic rocket.

Your rocket will be destroyed.

Bad idea.

Metal motor casing gets HOT HOT HOT. Plastic rocket + HOT HOT HOT = Melted plastic rocket.

 

[Bigander]

Originally posted by shreadvector
Using a metal casing motor like an Aerotech RMS will MELT your plastic rocket.

Your rocket will be destroyed.

Bad idea.

Metal motor casing gets HOT HOT HOT. Plastic rocket + HOT HOT HOT = Melted plastic rocket.

Has anyone tried high temp paint b4??

 

[wwattles]

Originally posted by shreadvector
Using a metal casing motor like an Aerotech RMS will MELT your plastic rocket.

Your rocket will be destroyed.

Bad idea.

Metal motor casing gets HOT HOT HOT. Plastic rocket + HOT HOT HOT = Melted plastic rocket.

Drat. Hadn't even thought about that side of things. I'm so used to using more heat-tolerant materials and not these cheap plastic things that I totally forgot about the temperature aspect. I guess at that point, the entire rocket becomes a SU, along with the 18/20 casing (unless you can safely scrape the melted plastic off the outside of the casing)

Bigander:
High-Temp paints wouldn't be very effective on this, since the metal casing is going to be in direct contact with the plastic at the front of the motor mount, and unless you can get enough of a heat-sink and dissipation system in there, it's still going to be hot enough to melt the cheap Estes plastic.

WW

 

[n3tjm]

What you might be able to do is epoxy a length of BT-20 into the rear of the rocket. This may require some enlarging of the hole, but it will provide a liner which will prevent the motor from melting the rocket (I only had that problem with disposables). You can either friction fit the motor in this tube, or incorporate a motor hook.

 

[Bigander]

Originally posted by wwattles

Bigander:
High-Temp paints wouldn't be very effective on this, since the metal casing is going to be in direct contact with the plastic at the front of the motor mount, and unless you can get enough of a heat-sink and dissipation system in there, it's still going to be hot enough to melt the cheap Estes plastic.

WW

Another thought, would it throw off cg too much if a lightweight aluminum replacement nozzle was made? I know my uncle could probably make 'em for me (he's a machinist, and a very good one too!). I figured that if you're already using a higher impulse engine the little bit of extra weight shouldn't be a problem.

 

[RocketRick]

Originally posted by shreadvector
Using a metal casing motor like an Aerotech RMS will MELT your plastic rocket.

Your rocket will be destroyed.

Bad idea.

Metal motor casing gets HOT HOT HOT. Plastic rocket + HOT HOT HOT = Melted plastic rocket.

I've flown the AT D13 in an Estes Snitch on a number of occasions, and it works fine, and doesn't melt the plastic.

The secret lies, I believe, in wrapping the motor in masking tape to friction-fit it into the plastic motor mount. Not only do you no longer need to worry about the cheesy plastic motor retainer not fitting over the aft closure, you also gain some insulation between the motor and the plastic rocket.

Also, the 18mm AT motors burn out so quickly that they don't seem to have *time* to get hot enough to melt the plastic....

- Rick "One man's experience" Dickinson

 

[shreadvector]

Yes, tape helps to insulate and the snitch has a body tube that is air cooled.

Other rockets with the metal casing held inside by thin plastic webs will not have that air cooling. The suggestion to alter it by grinding away the webs slightly and then epoxying in a BT-20 tube would definitely help, but it is a lot of work to make a heavy plastic rocket fly with a nice expensive casing.

I would fly my RMS motor in a "good" rocket (that I plan to get back and that has a good method of motor retention) and use the ever-present mountain of C6 motors in the plastic rocket.

The snitches of the past *may* have been made from a differnt plastic than the current batch of plastic rockets. I have yet to see a 2007 snitch to determine if they changed the plastic.

Originally posted by RocketRick
I've flown the AT D13 in an Estes Snitch on a number of occasions, and it works fine, and doesn't melt the plastic.

The secret lies, I believe, in wrapping the motor in masking tape to friction-fit it into the plastic motor mount. Not only do you no longer need to worry about the cheesy plastic motor retainer not fitting over the aft closure, you also gain some insulation between the motor and the plastic rocket.

Also, the 18mm AT motors burn out so quickly that they don't seem to have *time* to get hot enough to melt the plastic....

- Rick "One man's experience" Dickinson

 

[DaveHein]

I like n3tjm's idea about using a BT-20 tube with an engine hook. If the Metalizer uses the same motor mount as my Chrome Domes rocket you will need to add a centering ring at the back end of the motor tube. You could make the centering ring by glueing strips of cardstock around the BT-20 tube.

If you don't want to permantly modify your Metalizer you could make an adapter as shown below. The forward end of the adapter is a short piece of used 18mm motor. The yellow parts are short pieces of 1/8" square sticks. These would slide through the "screw holes" in the fin can. Once the adpater is inserted in the rocket you may need some method to ensure that it doesn't unscrew and come out.

The adapter and the reload casing are going to move the Cg down so you may need to add some nose weight to balance the rocket.

Dave

 

[BAR0051]

I have flown my Estes Blue Ninja on E18 & F39 reloads. When I built it, I made it to take E9 mortors so when I install the 24/40 RMS motor it is recessed in the motor mount so that the twist lock cap fits over it. I cut off a peace of a used D12 case and used it to line the inside of the twist lock cap and hold the RMS case from slamming back during ejection. Has worked well so far.

 

[shreadvector]

Someday they will update the instructions page and put them on a server with a faster connection than dial-up...

https://www.estesrockets.com/instructions/2155supernovapayloader.pdf

The Blue Ninja has the same back end as the supernova payloader, does it not? If so, then it has an internal motor mouont tube made of cardboard, so it is not the same as the rockets which only have plastic buttocks.

Your modifications for the BN are excellent. How fast does it become a silver ninja with those motors?

Originally posted by BAR0051
I have flown my Estes Blue Ninja on E18 & F39 reloads. When I built it, I made it to take E9 mortors so when I install the 24/40 RMS motor it is recessed in the motor mount so that the twist lock cap fits over it. I cut off a peace of a used D12 case and used it to line the inside of the twist lock cap and hold the RMS case from slamming back during ejection. Has worked well so far.

 

[BAR0051]

shreadvector is right, the Blue Ninja has a paper motor mount tube, and the blue wrapping did start coming off
I did mod my Quest Super Eagle to take the 18mm RMS motor but it also has a paper motor mount tube and still required major surgery, removing some plastic guts, installing a centering ring, gluing the twist lock cap on and installing 2 metal "engine" hooks to make sure I did not spit the RMS case. It is impressive on a D13.

 

[Bigander]

Originally posted by BAR0051
shreadvector is right, the Blue Ninja has a paper motor mount tube, and the blue wrapping did start coming off
I did mod my Quest Super Eagle to take the 18mm RMS motor but it also has a paper motor mount tube and still required major surgery, removing some plastic guts, installing a centering ring, gluing the twist lock cap on and installing 2 metal "engine" hooks to make sure I did not spit the RMS case. It is impressive on a D13.

The wrap is now a sticker. I believe i got one of the beta ones of this because it was wrinkled up the spiral and estes sent me a new one.