mounting motors

[carson]

I've never built a rocket so it's all new to me. My question is how do you mount motors on scratch built rockets?

 

[Rocketmaniac]

Originally posted by Carson
I've never built a rocket so it's all new to me. My question is how do you mount motors on scratch built rockets?

The answer is pretty much the same way you would in a kit....... The basic motor mount is this; you take body tube and motor mount tube (ie 18mm, 24mm, 29mm etc) and two centering rings...... For Example;

You want to build a 2.56" rocket and fly it on 29mm motors

You need some 2.56" body tube and 29mm Motor Mount Tube and (2) 2.56 X 29mm centering rings, ie the centering rings fit inside the 2.56" body tube and have a inside hole that a 29mm motor mount tube will fit....... Glue (or epoxy) the centering rings on the ends of the motor mount tube and then install this unit into the body tube.........


A few things to consider.........

1. Make sure you get (or make) the centering rings to fit the brand of motor mount tube you are using.... This means get LOC centering rings to use with LOC motor mount tube.......

2. Figure out what kind of motor retention you are going to use..... The best time to install a motor retention system is during the initial assembly........

I hope I have helped some, I am sure others will jump in real with more comments.......

 

[eugenefl]

Originally posted by Carson
I've never built a rocket so it's all new to me. My question is how do you mount motors on scratch built rockets?

Well, the answer is fairly broad. There are so many types of motor configurations VS. many different sized rockets. I suspect that you are considering centering a motor tube within a larger sized body tube. In this case, you can either order pre-manufactured centering rings or you can make your own out of plywood (for mid and high power) or cardboard, foamboard, or other sturdy material (for low power). Some rockets don't require centering rings because the engine itself is the same diameter as the rocket's main body. This is referred to as "minimum diameter." These are very simple as all they require is a motor block (aka thrust ring) to prevent the motor from shooting itself through the inside of the rocket.

Tell ya what, give us an idea of what you have in mind and we can more directly answer your question.

Glad to have you at The Rocketry Forum. Let us know how we can help. Post some pics of your projects. Remember, there's no project too small to share with the rest of the world.

 

[jflis]

Once you selected your components, the assembly is fairly similar.

As Rocketmanic said you need to first select the motor size that you want to mount. The sizes that are available are:

6mm (MicorMaxx motors, **very** tiny)
13mm (Estes mini motors)
18mm (Estes/Quest standard motors (1/2A, A, B, C)
24mm (Estes Black powder and some composite motors in the C-F range)
Mid-High power after this
29mm (composite motors in the F-H? range)
38mm
54mm
75mm
98mm

For 6mm - 18mm and some 24mm, friction fitting or using an engine hook is fine. For 29mm on up it can get a little more involved and if that is your interest I would point you to some of the other folks in this group (who i am sure will pipe in) as I generally stay with the 24mm on down.

The rest of this reply *assumes* "model" rocketry and is for 24mm or smaller motors.

After selecting your motor size, you need to select your body tube size. If they are the same size, then you are building what is called a "minimum diameter" model. In that case, your best bet is an engine block and friction fitting the motor.

ENGINE BLOCK: A small ring about 1/4" long that fits inside the body tube. You use a motor casing to set it into the body tube as shown in the attached figure.

FRICTION FITTING: Wrapping the motor with masking tape until the motor fits into the body tube VERY tightly (such that the ejection charge will not kick the motor out.

 

[jflis]

If your body tube is larger than the motor size then you need to have a motor tube and a method of centering it inside the body tube. This example also uses a motor hook to retain the motor (instead of Friction Fitting).

In this case you would have a motor tube with an engine block and an engine hook. The attached figure gives a simple example of how one would go together:

 

[jflis]

Depending on the materials you use, it may be recommended to place several wraps of masking tape to secure the engine hook, as shown

 

[jflis]

After that, you need to attach centering rings to provide a centered fit inside the body tube. As said earlier, the centering ring is a round of cardboard or fiberboard with an outside diameter equal to the inside diameter of the body tube. Inside this round of cardboard is a hole with a diameter matching the OUTside diameter of your motor tube.

This figure shows a typical example of how they are attached to make your motor mount:

 

[jflis]

Lastly, mounting the motor mount into the body of the rocket. See the attached figure. You place a bead of glue inside the body tube, all the way around. The motor mount will push this glue forward as you install it inside the body tube.

After the mount is fully installed, you run a bead of glue along the bottom centering ring as shown.

The type of materials used for the motor tube, centering rings, body tube and even the glues you use really depend on the power of the motor to be used. For A-F motors i've found cardboard/fiber board rings and white glue work just fine. As you go up in power you will find that you need plywood, epoxy and other exotic techniques to hold it all together.

Hope this was helpfull even if rather long winded...
jim

and I *just* now noticed Eugenio's response to this thread. Ain't it great (and comforting) when you get the same answer from multiple sources???

 

[carson]

Ok. It all sounds simple now. Thanks for the help.

 

[astrowolf67]

Carson, if you haven't built a rocket from a kit, you need to do so. Something simple, such as an Estes Alpha, or Baby Bertha, or a Fliskits Rhino. I recommend staying away from kits with plastic fin units for a first build. They don't teach the basic skills needed to do any scratch building.