motor max lift off weight chart?

[Adam Selene]

i'm designing an oddroc and need to determine what motor mount to build it around. I'n looking for a chart that lists the max lift weight for motors. i've tried thrustcurve and aerotechs web site, no luck. i could look at each individual spec sheet from thrustcurve or take the impulse and do the math but I AM LAZY! so, anyone know where i can easily get this info? I put this in the mid power forum because that is primarily what i'm interested in. I know estes lists it in their catalog but i'm looking for mid and/or hpr.

thanks in advance!

 

[Zippy]

Here's one I have for the 29/40-120 case. I allso have some for longer 29mm cases if you need them.

 

[astrowolf67]

Here is a formula, cut and pasted directly from Red Arrow Hobbies web site.


Will the motor lift my rocket?
When buying a rocket kit, use the manufactures recommended motors.
Use this rule of thumb when scratch building your own design.
To figure out if a particular rocket motor can safely lift your rocket, divide the number between the letter and the dash by 4.48. This will convert the average thrust from newtons to pounds. You will need at least 6 times the amount of thrust as your rocket weights with the motor included.
Example: E9-6
9 divided by 4.48 = 2.01
2.01 divided by 6 = 0.33 Lbs

Your rocket should weigh no more then .33 Lbs or 5.33 ozs.

 

[Stymye]

go here


https://www.info-central.org/index_search.html

click on resources
than click on thrust/weight
there are 2 charts you can print out

for some reason I can't link directly

 

[DynaSoar]

Originally posted by Adam Selene
i'm designing an oddroc and need to determine what motor mount to build it around. I'n looking for a chart that lists the max lift weight for motors. i've tried thrustcurve and aerotechs web site, no luck. i could look at each individual spec sheet from thrustcurve or take the impulse and do the math but I AM LAZY! so, anyone know where i can easily get this info? I put this in the mid power forum because that is primarily what i'm interested in. I know estes lists it in their catalog but i'm looking for mid and/or hpr.

thanks in advance!

Many motors are made with a hard early boost and a low sustain, so they can lift more than the 5:1 "rule" suggests. Frinstance, and Estes C5 will lift more than a "stronger" C6.

Use the flight simulation program under "Tools" on EMRR. Plug in your weight and diameter and pick engine types. It calculates from the thrust curve whether the rocket will get up to stable speed fast enough.

 

[Adam Selene]

Originally posted by Zippy
Here's one I have for the 29/40-120 case. I allso have some for longer 29mm cases if you need them.

Zippy, that's perfect! it looks like it was something printed by Aerotech, was it?

Do you have similar charts for the 29/120, 29/180 and 29/240 cases? (i know that will be getting above mid power)

or might you have a link to even more charts?

THANKS!!!

chuck

 

[Adam Selene]

Originally posted by stymye
go here


https://www.info-central.org/index_search.html

click on resources
than click on thrust/weight
there are 2 charts you can print out

for some reason I can't link directly

useful site and charts, i didn't know about that one. thanks!

 

[Zippy]

Yes the 29/40-120 chart was made by Aerotech. These other charts I mostly made myself using Aerotech data.

 

[Zippy]

29-240

 

[Zippy]

29-360

 

[Adam Selene]

Originally posted by Zippy
29-360

this page doesn't have lift weights.

the other pages are great, thanks again!

i notice on the 20/40-120 page that the max lift weight varies greatly by delay length. which seems strange to me. can anyone explain that? i'm assuming that the charts for 29/180 and 240 are for the standard medium delays?

 

[Stymye]

Originally posted by Adam Selene
useful site and charts, i didn't know about that one. thanks!

I have an excell spreadsheet that goes up to 38mm if your interested it also makes a great motor inventory list, ( print it and pencil in the quantity on hand in the far left column) .. it has the max lift off weight along with propelland weight and dimensions the "r" symbol indicates "reloadable" I havent started on the 38mm and up section but it's a good start


just print it out in the "landscape" setting

hope it does the trick

 

[Stymye]

the reason that max lift off weight decreases with delay time is because it takes into consideraton the time allowed for the chute to deploy in a rocket of that weight range on that motor.

it actually has nothing to do with the propellant weight or motor composition as many people might think,,
in other words....it's simply a guideline determined by expected altitude on that motor/delay combo and still allowing an ontime chute deployment.

 

[Zippy]

Ooops, the 29-360 chart is something I saved to work on and never did. I didn't use delay times in the calculations for any the charts I made. On the 29/40-120 chart I allways just pick a motor by it's max lift off weight for a short delay and then use intuition or rocsim to help pick an appropriate delay. They change the max weights for differant delays becouse a heavy rocket with a long delay might hit the ground before it deploys basically. There's a better explanation in the Estes catalog if I remember correctly, along with a detailed chart for their motors.

 

[Adam Selene]

Originally posted by stymye
I have an excell spreadsheet that goes up to 38mm if your interested it also makes a great motor inventory list, ( print it and pencil in the quantity on hand in the far left column) .. it has the max lift off weight along with propelland weight and dimensions the "r" symbol indicates "reloadable" I havent started on the 38mm and up section but it's a good start


just print it out in the "landscape" setting

hope it does the trick

Wow, did you just save me a lot of typing!
i was going to make a spreadsheet just like that.

THANK YOU!

 

[Rocketmaniac]

Originally posted by stymye
I have an excell spreadsheet that goes up to 38mm if your interested it also makes a great motor inventory list

Nice work Stymye!!! If I get some extra time, I might add more of the 38mm motors and some 54mm.....

 

[Stymye]

I only went thru the 29-120 and a few are missing here and there, like some quest motors, and some are almost non-existant motors but it's a good start.

feel free to use, just send or post any updated versions please.
because it took a good part of a day to do I'm fairly new to excel

 

[Mister Rogers]

Styme,
thanks for the excel spreadsheet, it is excellent!

 

[Thrasher]

Here is the thrust / weight chart that I use. It's for small rockets.