Motor Percentages

[11bravo]

OK.
You hear talk about a 60% "M", and a ___% "Q"...
How is the % figured?
Say 3 CTI Pro38 I285's; impulse of 512Ns/motor.
Total installed impulse of 1536Ns.
Puts it in the "K" range: 1280 < 1536 < 2560Ns.
Is it-
1536/2560 &#8776; 60% K
or
(1536-1280)/2560 &#8776; 10% K

Seems to me that it should be the 60% as it is the measure of the total so that probably means it's the 10%.

 

[rstaff3]

Neither. When figuring such things out, try to put in the 2 limiting cases and seeing what happens i.e. the lower range should give 0% and the full K should give 100%.


1536-1280/1280 = 20%

Now watch some show me I'm wrong

 

[jadebox]

Originally posted by rstaff3
Neither. When figuring such things out, try to put in the 2 limiting cases and seeing what happens i.e. the lower range should give 0% and the full K should give 100%.


1536-1280/1280 = 20%

Now watch some show me I'm wrong

Well, there is the matter of operator precedence.

1536-1280/1280 = 1535

(1536-1280)/1280 = 20%

-- Roger

 

[WillMarchant]

Originally posted by rstaff3
Neither. When figuring such things out, try to put in the 2 limiting cases and seeing what happens i.e. the lower range should give 0% and the full K should give 100%.


1536-1280/1280 = 20%

Now watch some show me I'm wrong

You're doing fine!

Take a look at https://www.tripoli.org/tmt/MMotors.shtml where you can check your algorithm against the TMT results.

 

[rstaff3]

Originally posted by jadebox
Well, there is the matter of operator precedence.

1536-1280/1280 = 1535

(1536-1280)/1280 = 20%

-- Roger

Egads! you're of course correct. Let me rephrase...

1536 1280 - 1280 /

 

[11bravo]

OK, so its a measure of how far over the lower class limit a motor is.
I'll buy that.

 

[cjl]

Originally posted by rstaff3
Egads! you're of course correct. Let me rephrase...

1536 1280 - 1280 /

Ahh, the joys of reverse polish

 

[rstaff3]

I love RPN...I'll cry when my old HP dies. IIRC they only have it on their more expensive calculators now and I don't need that power anymore.

 

[wildbluerocket]

.

 

[11bravo]

Kewl.
Was just wondering anyway.
RPN, mmmm, that was fun.
Dick- what HP do you have?
I have the 48G.
WAYYYY more calculator that I need now.
Or ever did actually.
But hey...

 

[rstaff3]

Originally posted by 11Bravo
OK, so its a measure of how far over the lower class limit a motor is.
I'll buy that.

Yup, where it stands as a % of the total thrust range for the given class motor.

 

[edwardw]

I've also got the 48G - I love the RPN function. So much faster and easier than my old TI 86.

Edward

 

[rstaff3]

Originally posted by wildbluerocket
The way I prefer is to call it a "1536 N-sec K855". Easy to approximate the burntime by dividing 1536/855 = 1.8 sec. The other qualifier is to say "progressing, regressive, square, with a tail, etc.". With that info, the curve can be approximated and the simulation will be within ~2% for most motors.

A lot (some? a few?) of EX people like to use that form - 1536K855. There is a precedence for that in early amateur circles IIRC.

 

[rstaff3]

Originally posted by 11Bravo
Kewl.
Was just wondering anyway.
RPN, mmmm, that was fun.
Dick- what HP do you have?
I have the 48G.
WAYYYY more calculator that I need now.
Or ever did actually.
But hey...

I have the 28C...a pic of which can be seen here: https://rocketdungeon.blogspot.com/2006/09/goodbye-to-old-buddy.html

Luckily, it wasn't dead after all. But yes, it's way more than I need too. Haven't programmed it in many years. I like the deep stack and it's constants...occasionally base conversions since I hardly can do hex in my head anymore.

I also have an old 25, the first cheap (ha, if $200 new was cheap) programmable. I now see you can get an RPN HP for about $50.

 

[11bravo]

I think mine as $120-$130 in the fall of '94.
Don't remember for sure, added it to my U-Bill.

 

[RocketRick]

Originally posted by rstaff3
Yup, where it stands as a % of the total thrust range for the given class motor.

Wouldn't that be "...as a percentage of the total impulse range for the given class of motor"?

 

[runandgun13]

anyone know of a source that has the ranges for all of the motors

 

[heada]

NAR has two lists, one for model rocketry (low/mid power) and one for high power.

https://www.nar.org/NARmrsc.html

https://www.nar.org/NARhpsc.html

If you know that 1/4A and 1/2A (why two for the same range, I don't know) is 0-1.25N you can figure out any of the others.

0.00 - 1.25N = 1/2A(1/4A)
1.26 - 2.50N = A
2.51 - 5.00N = B
5.01 - 10.0N = C
10.1 - 20.0N = D
20.1 - 40.0N = E
40.1 - 80.0N = F
80.1 - 160.0N = G
160.1 - 320.0N = H (high power level 1)
320.1 - 640.0N = I
640.1 - 1280.0N = J (high power level 2)
1280.1 - 2560.0N = K
2560.1 - 5120.0N = L
5210.1 - 10240.0N = M (high power level 3)
10240.1 - 20480.0 = N
20480.1 - 40960.0 = O (highest allowed in NAR/TRA as certified motors)
40960.1 - 81920.0 = P
81920.1 - 163840.0 = Q
163840.1 - 327680.0 = R
327680.1 - 655360.0 = S

(each one doubles the previous)


-Aaron

 

[uncle_vanya]

Originally posted by runandgun13
anyone know of a source that has the ranges for all of the motors

Tripoli

Doesn't list partial "A" motors like 1/2A 1/4A MicroMax etc.

 

[RimfireJim]

Originally posted by edwardw
I've also got the 48G - I love the RPN function. So much faster and easier than my old TI 86.

Edward

. . . Bunch of new-fangled stuff (scoff, scoff)

How about an HP41C and an HP15C, my workhorses for the last 25 years? One of my 41s (have two, one at work and one at home) started going out to lunch more and more, and now may be kaput altogether, so I use the 15C instead, though I don't like the key layout nearly as well. Great easy-to-use stats and linear regression functions, though, and fits into my shirt pocket nicely. Hope it never dies. . .

 

[FredA]

Rare and selling for more now then new.... A HP-16c

RPN on Binary, Octal and Hexidecimal ...BASE 10 TOO!

A real man's calculator.