Motor Length

[Faroutspacenut]

In a rocket with no engine block, is there is any guideline on how far a motor can extend past the end of the motor tube? Let's assume that the CG is still plenty far ahead of the CP in all cases.

 

[Steve Shannon]

In a rocket with no engine block, is there is any guideline on how far a motor can extend past the end of the motor tube? Let's assume that the CG is still plenty far ahead of the CP in all cases.

No, not as long as it's supported and the retention doesn't allow it to flop around.

 

[Bat-mite]

No, as long as you leave enough room for your NC shoulder, harness, chute, etc.

 

[djs]

No, as long as you leave enough room for your NC shoulder, harness, chute, etc.

And some of that stuff, you can shove down along side the motor case between the case and the body tube. I did this when I flew my 2.6" darkstar on a 7 grain K motor.

 

[cbrarick]

I stuff a K2045 in my gizmo. Sticks clear into the nose cone, flys great. Just pack the laundry around the motor tube.

 

[Handeman]

Also remember, when you use a long motor, some of that motor weight might be ahead of the CG so it acts like nose cone weight. Kind of balances things out.

 

[T-Rex]

Reading this, a question popped into my head.
When you intend to load the laundry around the motor, would it be a good idea to slide a piece of motor tube down onto the exposed motor as an insulator to protect the laundry? Since it is never mentioned in these threads, I am guessing no. It just seems like a good idea to me....

 

[Steve Shannon]

Reading this, a question popped into my head.
When you intend to load the laundry around the motor, would it be a good idea to slide a piece of motor tube down onto the exposed motor as an insulator to protect the laundry? Since it is never mentioned in these threads, I am guessing no. It just seems like a good idea to me....

It could not hurt, especially on long burn motors. Even cardboard tubing would help.

 

[T-Rex]

It could not hurt, especially on long burn motors. Even cardboard tubing would help.

Kinda what I was thinking... cardboard tube taped in place (if you can reach) so it doesn't foul the chute during deployment.
Good to know that I am not a complete idiot (though I may be a partial one)... Thanks for the reply!

 

[Steve Shannon]

Kinda what I was thinking... cardboard tube taped in place (if you can reach) so it doesn't foul the chute during deployment.
Good to know that I am not a complete idiot (though I may be a partial one)... Thanks for the reply!

We're all partially so, just in different directions. Your question/solution was a good one.


Steve Shannon

 

[Howie]

I faced this issue on my Loc 5.5" V2 - after using Rocksim and discovering a 6XL CTI case would be stable, how would I package that and the recovery items? My solution was an add-on shelf made of a piece of motor mount tube cut to the length that case extended past the kit motor mount tube, with a 4" O.D. centering ring glued to the forward end. Once I insert the case into the motor mount, I slide this over the case from the front. In this case there's sufficient room for my chute / recovery item bundle above the shelf and below the nose cone shoulder, which is wrapped in a Nomex blanket. The shelf keeps this bundle forward under boost. Since only a short run of Kevlar cord from the D-ring to the harness is outside the wrapped bundle, there has been no issues with the heat of ejection or any fouling / tangling of recovery hardware as far as I can tell.