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Old 08-08-2011, 11:11 PM
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Tau Zero Tau Zero is offline
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Question Center of Gravity (CG) vs. Mass override

Okay, Craig, I've spent about an hour searching the forum for one of your old posts, to no avail. (heavy sigh)

I'm specifically looking for information on the non-standard placement of RockSim's "mass override" in Semroc's balsa components. I went back to 2009, but maybe I didn't go far enough.

If you can "spill the beans" again here, it'll benefit somebody else besides just me.

FWIW, I'll be away from the computer from Wednesday-Saturday of this week.

Cheers,
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Last edited by CenturiGuy : 08-09-2011 at 12:16 PM.
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Old 08-09-2011, 12:04 AM
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CPMcGraw CPMcGraw is offline
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Quote:
Originally Posted by CenturiGuy
Okay, Craig, I've spent about an hour searching the forum for one of your old posts, to no avail. (heavy sigh)

I'm specifically looking for information on the non-standard placement of RockSim's "mass override" in Semroc's balsa components. I went back to 2009, but maybe I didn't go far enough.

If you can "spill the beans" again here, it'll benefit somebody else besides just me.

FWIW, I'll be away from the computer from Wednesday-Saturday of this week.

Cheers,


If you're just looking for a one-time override, there's the "Mass override" tab (4th from left) on the component selection dialog. Check the box and fill in the new mass value.

If you're looking for an across-the-board override, it's probably in the "Materials" DB table. Been a while since I've fiddled with the DBs...

Hope this is what you're looking for, otherwise I'll be hearing from Bono...
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  #3  
Old 08-09-2011, 12:17 AM
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Tau Zero Tau Zero is offline
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Red face Further clarification...

Quote:
Originally Posted by CPMcGraw
If you're just looking for a one-time override, there's the "Mass override" tab (4th from left) on the component selection dialog. Check the box and fill in the new mass value.

If you're looking for an across-the-board override, it's probably in the "Materials" DB table. Been a while since I've fiddled with the DBs...
Actually, you were explaining that you set the location for the mass override at a certain percentage (60%?) from one end or the other of nose cones, transitions, and so on. That's what I was trying to remember, and couldn't express very well.

Clear as mud?


Quote:
Hope this is what you're looking for, otherwise I'll be hearing from Bono...
I thought it was *completely* appropriate that they filmed the video for that song in Las Vegas, Nevada...
.
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Jay Goemmer
"Centuri Guy"/"Tau Zero"
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NAR 86131


"I think about organizing things all the time. Never seems to happen. I find something that piques my interest and I'm off on a quest. Or a Centuri. "

--Bill Eichelberger, 02/22/2022


“Centuri fret buzz in an updated form.”
Bill “Wallyum” Eichelberger re: Estes Flutter-By
03 Sept 2014
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  #4  
Old 08-09-2011, 11:37 AM
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CPMcGraw CPMcGraw is offline
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Quote:
...Actually, you were explaining that you set the location for the mass override at a certain percentage (60%?) from one end or the other of nose cones, transitions, and so on. That's what I was trying to remember, and couldn't express very well...


Ahh, now I remember...

I think...

[Doesn't mean that I am, however...]

Shades of Blue...

That wasn't the mass override so much as it was the CG positioning. Since RockSim allows us to "fine tune" the balance point of each component, I used an "edumacated guess" as to where the approximate CG point would be.

Depending on the component and it's overall shape, my placement is somewhere between 60% and 71% from either the point of the cone, or the smaller side of the transition, to get the CG close to the actual mark. If you don't give this value, RockSim still calculates the CG at the 50% location, which is "good 'nuff" for most work. Moving the CG over a bit allows for a better calculation of the whole design, especially where you are trying to tweak the model for as much performance as you can.
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