I don't understand this, help?

I don't get this idea with motor retention.

I'm about to start in on my first high power rockets, both BSD kits, a 3" Horizon and a 3" Sprint.

Both kits come with a motor retention system that keeps the motor from being ejected out the back upon firing of the ejection charge.

Yet neither have anything from keeping the motor from going up through the rocket on ignition. What I understand from reading the directions is that masking tape is used to friction fit the motors and keep them from going up through the motor tube.

Why is it that no one used motor blocks? I know they're looking at the ability of using multiple lengths of motors, yet both estes and AT are able to accomplish this with the use of spacers.

I don't understand why I need 15 min epoxy to keep everything together then nothing but masking tape to keep the motor in the motor tube, surely seems like it's the weakest link in the rocket, yet if it's adequate the epoxy seems like severe overkill.

From what i've researched this is a pretty standard method, can someone explain the reasoning.

Without a descent reason I'm wanting to go with a motor block in the motor tube.

Thanks

Jason

Jason...
What are you planning on using for motors? Reason I ask is, If you're going the RMS(Reloadable Motor System) from Aerotech route, the casing's aft closure will keep the motor from moving forward at launch.

Stones,

Didn't know that. Eventually and it may be months or even six months i'd like to get some reloadable casings, finances are short, shorter yet after getting these kits.

Anyway one of the reasons I got these is that they do fly on F and G single use motors, i like that for the smaller fields.

So in answer to your question, they'll probably be flown on single use and also reloadable motors.

Jason

These rockets are made for a variaty of motor lenths. If you are using Aerotech motors the aft closure is wider than the diameter of the rest of the motor and therefore when it is thrusting that keeps the motor from shooting up into the rocket. however there is nothing on the aerotech or other oads to keep them from shoot out the back of the rocket when the ejection charge goes off.
Some other types of motors do not have this and the tape will keep them in place.
One of the reasons epoxy is used is fin joints and other areas of the rocket go through the stress of flight over and over when the masking tape only does one time
Also the masking tape is just used to make the motor fit tighter but the epoxy is holding things together. There is really nothing else that could hold an area like a fin joint but epoxy
Another thing it is a better idea to use 2 ton epoxy to make the rocket more durable.

If you're using a single-use F or G motor, instead of just friction-fitting the motor, run a thick ring of masking tape around the back 1/2" of the motor (3 or 4 layers thick and trim the part hanging off the back of the motor with a hobby knife--you don't want to start a fire by torching the masking tape). This will create a thrust ring on the back of the motor that will be more than enough to keep it from shooting through the tube.

Then isn't it a pain to get the motor pushed up all the way into the tube?

I guess what i'm having a hard time understanding is that if i'm able to push it up there, then wouldn't the thrust of the motor also be able to keep pushing it up??

Don't get me wrong, I know it works and that many of you do it, just can't understand it.

On the other hand what would a motor block hurt if i put it all the way to the top and then just cut spacers to fit different motors?

Jason

"What we have here is a failure to communicate"

You're right Darien, I just caught on to what he is saying, i was thinking the top of the motor, not the bottom, now i gets it...

Actually, if you don't think you'll be using anything any larger than a G40 or G80, it might be a good idea to go ahead & glue an engine block in. That way you could dispense with the tape engine block & just use the spacers. It would simplify things just a bit.

I never ever ever put a motor block in a motor mount tube (okokok...sometimes in the 18mm Estes kits, but NEVER in a D-12 powered kit...gotta love that E-9) for the very reason that I might wanna put a longer motor in there. A tape ring motor block is always an easy thing to do in the field and I've never had one fail yet (NOTE: Don't do this for a K motor).

WELLLL... since you brought it up... I thought that I might mention that I've flown up to a Kosdon L850 (including K700F, K350S, J450F, J280S, I130CS Long Burn, and a host of others) successfully with a 2" wide tape thrust ring. So, yes, the tape is plenty strong to hold the motor from shooting forwards. And yes, you can use this technique with K motors