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Old 12-29-2012, 05:01 AM   #1
granelli
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Default Balancing/CG on AP heli

How do you go about balancing the cg of an AP heli that has two 6s lipos on the boom and a gimbal hanging off of the front? Is it just normal procedure? It sits pretty level holding the blade grip perpendicular to the boom, but that doesn't fully account for an overall balance, does it?

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Old 01-01-2013, 11:30 PM   #2
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please please please show us a photo

first off that would be funny as hell to see

and second it could give us some kind of insight on what we are dealing with

i dont think the lipos on the boom would be too reliable
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Old 01-02-2013, 04:00 PM   #3
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It's an aerial photography setup, PS1 gimbal on the front with a battery mount on the boom. This is a pretty common setup.
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Old 01-02-2013, 04:01 PM   #4
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http://www.helifreak.com/showthread.php?t=258518
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Old 01-02-2013, 05:22 PM   #5
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Just simply hold the helicopter by the rotor brake disc between thumb and middle finger and see how it hangs. If you have no brake disc on top then you can turn the blades perpendicular to the copter and suspend it by the blade gips. You want to see it sit level but a couple degrees either way generally makes little difference.
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Old 01-02-2013, 05:29 PM   #6
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My heli isn't correctly balanced (goes forward)
But I just trim it out...
Other than that this setup is way out of my league
Sorry
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Old 01-02-2013, 06:39 PM   #7
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As always, thank you DJ. That's what I was thinking. I'm using a small level on the tail and on the front and holding it from the blade grips. And as you said, it seems anything within +/- 5 degrees will "work".
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Old 01-03-2013, 10:22 AM   #8
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I've been doing a lot of research into helicopter flight dynamics recently (full scale), and one of the things I've read is that it's better to heli slightly nose heavy. This is because the rotor downwash hitting the boom tends to try to push the tail down, and a bit of extra weight on the nose helps counter this.

Anybody seen anything like that on RC?
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Old 01-03-2013, 10:47 AM   #9
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Quote:
Originally Posted by Crash_Expert View Post
please please please show us a photo

first off that would be funny as hell to see

and second it could give us some kind of insight on what we are dealing with

i dont think the lipos on the boom would be too reliable
What are you going on about? Do you know anything about AP Helis?
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Old 01-03-2013, 01:12 PM   #10
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Quote:
Originally Posted by R_Lefebvre View Post
What are you going on about? Do you know anything about AP Helis?
Not helis
I've been doing a shit-ton of research on quads though
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Old 01-03-2013, 02:08 PM   #11
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Quote:
Originally Posted by R_Lefebvre View Post
I've been doing a lot of research into helicopter flight dynamics recently (full scale), and one of the things I've read is that it's better to heli slightly nose heavy. This is because the rotor downwash hitting the boom tends to try to push the tail down, and a bit of extra weight on the nose helps counter this.

Anybody seen anything like that on RC?
I've felt it first hand, I have no real data or knowledge. On my big slow AP ship, it will fly fine slightly nose heavy, but tail heavy is bad. Tail heavy equates to very exaggerated flight characteristics and an unhappy Wookong H system. I almost would say I prefer a little nose heavy with the WKH at least, it seems to fly smoother and with more predictability.
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Old 01-05-2013, 07:49 AM   #12
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Quote:
Originally Posted by Crash_Expert View Post
Not helis
I've been doing a shit-ton of research on quads though
Ok, then please sit back and read a little more here before making snide comments about other people's setups. Putting batteries on the tail boom for balance on an AP heli is extremely common.
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Old 01-05-2013, 07:52 AM   #13
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Quote:
Originally Posted by granelli View Post
I've felt it first hand, I have no real data or knowledge. On my big slow AP ship, it will fly fine slightly nose heavy, but tail heavy is bad. Tail heavy equates to very exaggerated flight characteristics and an unhappy Wookong H system. I almost would say I prefer a little nose heavy with the WKH at least, it seems to fly smoother and with more predictability.
Yes, and that's basically what they say for full-scale. You should be equally balanced, or nose heavy, NEVER tail heavy. I think it gets worse flying forward as well, because the rotor downwash hits the tail boom even more.
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Old 01-05-2013, 07:18 PM   #14
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Quote:
Originally Posted by Crash_Expert View Post
My heli isn't correctly balanced (goes forward)
But I just trim it out...
Other than that this setup is way out of my league
Sorry
When someone asks for help, Its proper to offer help. If you dont know anything about Helis or how there setup, why are you chiming in on this?

I use a boom mount for two 6cell lipos that can be moved forward and aft to adjust for CG.

I usually have someone help me lift the heli, I hold the rotorhead, partner hold heli horizontal with the ground. When released, If heli falls to one side or the other, I adjust the batteries accordingly.

Heli if all up weight. Everything I use while shooting is on the heli.

DJ I think I might have repeated you post, sorry about that.
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Old 01-05-2013, 07:25 PM   #15
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We teater ours on a dowl. Putting the dowl under the landing gear. Getting cg so that dowl is just under main shaft with a hair bit of weight forward. Seems to be most precise method for us.
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Old 01-08-2013, 06:13 PM   #16
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Quote:
first off that would be funny as hell
It's common practice.

http://aerialskycam.com/Contact_Us.php
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Old 01-09-2013, 12:20 AM   #17
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I've been trying many setups to find a quick efficient way to measure the cog, I've found my 6-8" level works great. I hang the heli with the blades both parallel and perpendicular to measure all axis's. (no longer doing left right balance/ Just on initial setup) and place the level on various places that should measure true. This is probably a much bigger issue for me or anyone using autopilot systems.


Quick question for the pro's in this thread, is there any difference between say the ps1 battery mounts and the infinity hobby mounts? The infinity creates a tray for the batt on each side. They are very similar.

Thanks for the help
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Old 01-09-2013, 11:33 AM   #18
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Quote:
This is probably a much bigger issue for me or anyone using autopilot systems.
A good autopilot system should be able to trim out for any reasonable imbalance.
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Old 01-09-2013, 07:25 PM   #19
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Quote:
Originally Posted by Crash_Expert View Post
My heli isn't correctly balanced (goes forward)
But I just trim it out...
Other than that this setup is way out of my league
Sorry
Wont just "trimming it out" wear out your swash bearing?
I made an eye bolt(bolt, washer, solder) for the brake disk bolt hole. I then hung it from my garage ceiling by some wire. I'll tell you, ever messed with a triple beam?
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Old 01-09-2013, 09:05 PM   #20
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i kept my mouth quiet for a while but i had no idea he was talking about a pro setup.
i simply thought it was some kind of diy thing

sheesh people

one second they'll help you out and the other they tear you apart like a pack of wolves....
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