Motor Tube Question

[Scott Chase]

I've posted the Open Rocket screen shot. I'm trying to decide how close the motor tube can be to the bulkhead without damage.
I searched the web but didn't find any standard for MMT length vs distance to bulkhead. Any suggestions?

 

[neil_w]

Looks like you've got tons of space there. Are you thinking that might be too close, or do you want to shorten it up? Just make sure you have adequate room for the recovery materials.

Two minor notes:
1) you don't need all that extra tube at the front of the motor mount; it's not accomplishing anything.
2) The motor should extend out the back a bit so you can grab it. You can set the overhang value in the motor mount tab. It'll affect CG a bit, so it is good to set it correctly.

 

[Scott Chase]

Looks like you've got tons of space there. Are you thinking that might be too close, or do you want to shorten it up? Just make sure you have adequate room for the recovery materials.

Two minor notes:
1) you don't need all that extra tube at the front of the motor mount; it's not accomplishing anything.
2) The motor should extend out the back a bit so you can grab it. You can set the overhang value in the motor mount tab. It'll affect CG a bit, so it is good to set it correctly.

Neil
In your first note you stated that the extra tube up front is not accomplishing anything. I've had problems with some high speed deployments. So I was thinking that I could lengthen the motor tube towards the bulkhead creating more pressure on the bulkhead. Thus insuring a better ejection of the payload bay. So am I totally incorrect? and if so can you tell me why?
Thank you
Brian Johnson

 

[neil_w]

In your first note you stated that the extra tube up front is not accomplishing anything. I've had problems with some high speed deployments. So I was thinking that I could lengthen the motor tube towards the bulkhead creating more pressure on the bulkhead. Thus insuring a better ejection of the payload bay. So am I totally incorrect? and if so can you tell me why?

In my opinion, that is not an overly large interior volume to pressurize. However, if you to increase your safety margin by reducing that volume, then put another centering ring at the front of the motor tube to seal off the compartment.

 

[Scott Chase]

In my opinion, that is not an overly large interior volume to pressurize. However, if you to increase your safety margin by reducing that volume, then put another centering ring at the front of the motor tube to seal off the compartment.

Neil
Are you saying it would be safer to add an extra ring at the front of mmt to seal off the compartment?

 

[neil_w]

I dunno about "safer", but I think there should be a centering ring at the front of the motor mount tube just on general principles.

 

[tsmith1315]

Less volume to contain the gases=> higher pressure

 

[JoePfeiffer]

Neil
In your first note you stated that the extra tube up front is not accomplishing anything. I've had problems with some high speed deployments. So I was thinking that I could lengthen the motor tube towards the bulkhead creating more pressure on the bulkhead. Thus insuring a better ejection of the payload bay. So am I totally incorrect? and if so can you tell me why?
Thank you
Brian Johnson

Extending the motor mount tube, by itself, doesn't increase the pressure and so doesn't increase the force. You need that front centering ring to seal off the compartment and reduce the volume to do that.