# Aquiring motors for the RMX-1

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#### shrox

##### Well-Known Member
I would like some help with this. I am hoping someone can obtain the motors the RMX-1 will need, fabricate the needed air-start system, and will attend the launch of the vehicle to operate the rocket motor portion. I think delegating this task will be the best approach for this to be successful.

shrox

#### ClusterWiz

##### Well-Known Member
First we will need to know some things. What is the space you have for the motor(s). How much thrust will you need to get it moving. And approximately how long of burn do you need/want. And what will your budget allow? If we can't find what you need I bet there is always someone out there who could make one for you for allot less cost than if you bought one.

#### shrox

##### Well-Known Member
Well, I have allotted for 1 large motor for this first test with a rocket motor, but that won't be until the third or fourth flight in a few months. I'll have the specs by then, just wonder what will be involved.

shrox

#### ClusterWiz

If the rocket is about 100lbs. You want something with at least 2250N of thrust to keep the 5:1 thrust to weight ratio. So i would thing you would need a minimum of a M1939 , about 28in. long and 98mm. to be save and more impressive about it, you should go with a N2000, 98mm and 41in. long. a N2000 from most places is about $800. you must have a level 3 cert. and I am unsure if you need a LEUP at this time. If you do not have have a level 3 cert. of a LEUP have a freind that does buy and assemble the motor for you and have him make sure that you rocket is able to take the power of an N2000. Are you planning on gowing to LDRS? you wil get lots of advice from people there. good luck with the progect and keep us posted. we need more new pics. #### shrox ##### Well-Known Member Originally posted by ClusterWiz If the rocket is about 100lbs. You want something with at least 2250N of thrust to keep the 5:1 thrust to weight ratio. So i would thing you would need a minimum of a M1939 , about 28in. long and 98mm. to be save and more impressive about it, you should go with a N2000, 98mm and 41in. long. a N2000 from most places is about$800. you must have a level 3 cert. and I am unsure if you need a LEUP at this time. If you do not have have a level 3 cert. of a LEUP have a freind that does buy and assemble the motor for you and have him make sure that you rocket is able to take the power of an N2000. Are you planning on gowing to LDRS? you wil get lots of advice from people there. good luck with the progect and keep us posted. we need more new pics.
Remember, it is not launching from the ground, and it will be travelling 50 to 60 mph at about 10,000 feet when it fires. It will weigh about 60 lbs. How does a shorter, wider motor burn?

shrox

#### daveyfire

##### Piled Higher and Deeper
Shorter, wider motors will give you a long burn duration with less thrust. Longer, skinnier motors will give you a shorter burn duration with more thrust. I think you'll want to go with some sort of EX motor, since you need a rather unique thrust profile and have interesting space constraints. EXers up north are plentiful -- talk to Tony Alcocer, Geoff Huber, or any number of others. HTH!

#### ClusterWiz

##### Well-Known Member
I also think that you should use a EX motor. Ed Jacoby and Pat Gordzelic (I butchered those names) have a good track record with making large EX motors. i think you should go with a rather long burn. Have a custom case and closures with snap rings made for you. It doesnt have to be that long only 15in. or so. But make it a 150mm or a 200mm (8in.) then you can have a rather fast propellant. Make it a smokey so you can see it from 10k.

#### shrox

##### Well-Known Member
I was thinking of 4-1/2" by 20". I can adjust it within 1/2" on the diameter and several inches on the length as well.

shrox

#### ClusterWiz

##### Well-Known Member
Than I think your best bet to get feasible thrust and about the right size is a M1419. The reload is $420 from Wildman and is 98mm and 22.8in. Long. And is$470 for the needed hardware. You will be able to see the smoke plume even from 10k. The motor weighs 15.5 lbs. so its not to incredibly heavy. Should be a very neat flight and I cant weight to see some pics of it.