Motor Retention Question

[Alex123]

Hello,

My team and I are designing a level two high power rocket with a plugged motor. One question we have is regarding motor retention.

We will be using a two-piece motor retainer so the motor does not fall out. It is our assumption that the motor retainer does not take forces from the motor, it simply holds it so it doesn't fall out of the motor tube. Is this correct?

We will also be using a thrust plate which will screw into the lower centering ring. It is understood that the thrust plate takes all the forces of the motor and transfers them to the airframe of the rocket, does this sound right? Secondly, what is stopping the motor from shooting straight through the nose cone during launch? Does it have a lip on one end?

Thank you very much for your help.

 

[heada]

Most motors have a thrust ring at the aft end of the motor. Sometimes it is part of the aft closure, sometimes integrated into the case. That thrust ring transfers the force to the aft centering ring or thrust plate or motor retainer, all depending on how the aft section is designed. It's also what keeps the motor from going through the rocket.

It is highly recommended to have an advisor that has HPR experience to consult with before getting too far into your project.

 

[Voyager1]

^^^ This!
Take headas’ advice and get an experienced HPR mentor for your team.

Just asking those questions indicates a lack of knowledge for anyone designing and building an L2 rocket that can use motors from J to K. Has anyone in the team even done this with an L1 rocket, or even a mid powered rocket? It seems that you have never used a reloadable or single use composite HPR or MPR motor before.

I don’t wish to sound harsh, but when someone posts questions like this in the Beginners section it does suggest that they might not have had sufficient experience at low and medium power design and builds to be contemplating an L2 design and build.

However, to help you answer these and other questions you will have, here are a few resources worth investigating:

Here is a video from Apogee that explains the use of screw on motor retainers:


Get a copy of one or both of these books:

https://www.amazon.com.au/Modern-High-Power-Rocketry-Mark-Canepa/dp/1412058104

https://www.amazon.com.au/Make-High...55-87cc-7a1b83a91344&pd_rd_i=1457182971&psc=1

Good luck and welcome to the forum.

 

[Alex123]

Thank you both very much for your responses. This makes way more sense now.

Voyager1, you are right. This will be our team's first ever rocket built. We are competing in the 2025 NASA Student Launch and we are very much learning on the go. Fortunately, we have two project mentors that will be able to help us. It is challenging developing a rocket with zero experience, but so far we have learned a great deal and are enjoying the process.

Thank you again to the both of you for your responses.

 

[mtnmanak]

There is a lot in this page that should help you out:

https://www.mountainmanrockets.com/index.php/hpr-primer/