Question about motor mount tube length

[solid_fuel]

I am planning a Estes Nike Smoke build. Kit 7247; the BT-60 body tube one. I want to put a 24mm motor mount in. what length should the MMT be?
For future builds is there a general rule of thumb for how long a MMT should be in relation to the longest motor I plan to use?

 

[LithosphereRocketry]

Are you building for blackpowder or composites?

Other than Cesaroni composite reloads (which not too many people fly due to expense and HAZMAT) there aren't 24mm motors longer than 3.75 inches. That gets you up to a midrange F in composites.

In larger diameters you typically have larger motors stick out the top of the mount. However in 24mm many motors do not have thrust rings at the nozzle so you typically use a motor block positioned for 3.75 inch motors and add a 1" spacer to fly shorter ones (e.g. C11 & D12 in Estes and E15, E30 and 24/40 loads in composites.) Such spacers are included in Estes E kits or can be made from 1" off a spent motor.

In answer to your second question I've never really learned a good rule. With BP you almost always want approx. the length of the motor but composites you can make it much shorter.

 

[rstaff3]

I would make the mount the length of an Estes D motor and use an Estes twist on connector. You can use longer motors if you leave out any hooks or blocks. Masking tape thrust rings work great. I have had two problems with longer mounts when using Estes tubes. First, composite delays tend to have an afterburn that can play havoc on the tube. Also if you use the a few Ds and then move up to Es you find the fit can be bad with built up residue. This is a down side of not using a block/spring retainer with a spacer. Just my 2¢.

Sent from my SAMSUNG-SGH-I337 using Rocketry Forum mobile app

 

[solid_fuel]

Thanks for the replies. I plan to mainly fly Aerotech composite 24mm reloads with a screw on retainer. no forward motor block needed.
I will make it about the same length as the motor case.

 

[solid_fuel]

Estes twist on connector

what is this?

 

[smugglervt]

Estes brand plastic motor retainer.

Sent from my SM-G935V using Rocketry Forum mobile app

 

[rstaff3]

It's a two part PVC retainer...look on the Estes site. They make 24mm and 29mm versions. The latter come in their PSII kits.

Sent from my SAMSUNG-SGH-I337 using Rocketry Forum mobile app

 

[rstaff3]

Oh wait...screw on is the proper description. Twisting works if you keep at it.

Sent from my SAMSUNG-SGH-I337 using Rocketry Forum mobile app

 

[rstaff3]

Thanks for the replies. I plan to mainly fly Aerotech composite 24mm reloads with a screw on retainer. no forward motor block needed.
I will make it about the same length as the motor case.

Per my earlier suggestions, said reloads come in two lengths. Don't limit yourself.

Sent from my SAMSUNG-SGH-I337 using Rocketry Forum mobile app

 

[LithosphereRocketry]

Thanks for the replies. I plan to mainly fly Aerotech composite 24mm reloads with a screw on retainer. no forward motor block needed.
I will make it about the same length as the motor case.

With no forward motor block you'll be fine with whatever length. It doesn't make much difference if your motor sticks out the top.

Sent from my LGL44VL using Rocketry Forum mobile app

 

[solid_fuel]

Per my earlier suggestions, said reloads come in two lengths. Don't limit yourself.

I would like to get this rocket back after flight

 

[Nathan]

Are you building for blackpowder or composites?

Other than Cesaroni composite reloads (which not too many people fly due to expense and HAZMAT) . . .

???

 

[LithosphereRocketry]

???

In 24mm I mean. In larger diameters I agree that CTI is pretty common.