# RMS numbers?

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#### TwoWalks

##### Well-Known Member
Been at this a long, long time now ... about 2 weeks and am starting to get an understanding of the numbers and meaning of SU rocket motors. Figure its time to expand my understanding and knowledge.

Is there a place that shows and explains the numbering system for RMS motors?

#### TwoWalks

##### Well-Known Member
On the RMS motor casings there is a number (first to designate dia.) then a second number (designates length) What I am not sure of is a third number:

"29-40/120 casing" 29 dia - 40/120 length does this mean there are two casing bodies of different length? or?

Thanks

#### loopy

##### Well-Known Member
The first number is the motor diameter, and the other numbers are the impulse range handled by that casing. In the example given, it's a 29mm motor casing for motors with a total impulse between 40 and 120 newtons. In the high power world, you'll see things like 29 180, 29 240...etc. These are 29mm motors handling up to 180 newtons, 240 newtons, etc. The 40-120 is a little different than the rest of them. Not sure why, though. As far as if they are different lenghts, kinda. In the HPR world, the bigger numbers tend to be longer cases, but it's related to the impulse limit of the casing.

Loopy

#### n3tjm

##### Papa Elf
Most other brands of motors also follow the same scheme. You will notice that the number is the optimum total impulse... you will rairely see a reload that has that total impulse. For example... RMS 29/360 (I love that motor) has two loads, the H268 (TI: 320) and I200 (TI: 330).

The range of impulse for the cases can vary. I have a Kosdon 38/640 case... I have some I130 loads, which have a total impulse around 550. The Kosdon loads are actually near 640, but I do not have any. I also have access to some AMW loads for this case... 660 n/s. J500 motors. I fired the last one in November...

#### TwoWalks

##### Well-Known Member
Thanks, I think I've got it ... probably not completly, but a whole lot better than I did have Sure wish one of my local clubs would have a launch pretty soon, think it will help more when I can actually see some of the motors.

Thanks again for the great input.