Fun, Learning, Friendship and Mutual Respect
START  HERE


Unregistered
Go Back   HeliFreak > R/C Helicopters > Aerial Videography and Photography


Aerial Videography and Photography Aerial Video/Photo from R/C Helicopters


Reply
 
Thread Tools Display Modes
Old 09-09-2011, 07:13 PM   #1
barrocco
Registered Users
 

Join Date: Jan 2011
Location: Norway
Default Helicam solutions stability

Hey, guys!
I have a Pro 3x from HelicamSolutions in a Trex 700. We have had 4 flights and the still images are unsharp and useless even after photoshopping. .I strongly belive that it is due to vibrations from the heli. What can I do? Can I put a gyro in it and exactly where should I put the gyro? Straight under the gimbal or some other place?

And to which servo shall I connect the gyro to?
I have a Futaba 401 with Align DS620 ready to be mounted if necessary.
I use a Canon 550D with a kit lens 18-55mm with IS on.

Are there any other things beside putting a gyro i can do? Ive tried with symetrical 710mm blades, 710mm asymmtrical blades and even with 800mm blades and RPM from 1200 to 1800. Still bad images.
Best Regards

Barrocco
Attached Thumbnails
Click image for larger version

Name:	IMG_0736.jpg
Views:	137
Size:	59.3 KB
ID:	252552  
barrocco is offline        Reply With Quote
Old 09-09-2011, 07:38 PM   #2
yeehaanow
Registered Users
 
Posts: 301
 

Join Date: Sep 2004
Location: Vermont
Default

Try raising your shutter speed to something above 1/500th.
yeehaanow is offline        Reply With Quote
Old 09-10-2011, 05:38 AM   #3
barrocco
Registered Users
Thread Starter Thread Starter
 

Join Date: Jan 2011
Location: Norway
Default Helicam solutions stability

Got to about 1/250.

But where do I install the gyro?
barrocco is offline        Reply With Quote
Old 09-10-2011, 05:56 AM   #4
Anto6ka
Registered Users
 
Posts: 311
 

Join Date: May 2010
Location: Chisinau
Default

Installing the gyro won't solve your problem. You are facing vibrations, which should be eliminated via mechanical setup (balancing everything out), and isolating the gimbal from heli.
Electronic gyros with servos are used to compensate for unwanted movements, not vibrations. Only gyro that can help you with your vibes is a mechanical one, but if your heli is electric, you should put some effort in it and make it almost vibration free, it's possible.
Anto6ka is offline        Reply With Quote
Old 09-10-2011, 11:44 AM   #5
barrocco
Registered Users
Thread Starter Thread Starter
 

Join Date: Jan 2011
Location: Norway
Default

Ok. I understand. Thank you
barrocco is offline        Reply With Quote
Old 09-14-2011, 05:40 AM   #6
Windbreaker
Registered Users
 
Posts: 1,052
 
My HF Map location
Join Date: Sep 2007
Location: Waipahu, HI
Default

Here's a method to balance main rotor blades that works very well. Instead of a steel rod I use a razor blade with masking tape over the edge to create a crisp fulcrum, and support the blade with some modeling clay.

I use a balance beam scale to weigh the blades.

This method is probably a lot more accurate than any blade balancer out there.

http://www.rchelisite.com/rc_helicop..._balancing.php
__________________
Custom quad copter, Cobra C-3525/18 motors and ESCs; APC 15x4 thin electric props. OpenPilot ControlCopter board. Futaba 8FG Super 2.4 gHz FAAST system.
Windbreaker is offline        Reply With Quote
Old 09-14-2011, 01:06 PM   #7
WMann
Registered Users
 

Join Date: Nov 2004
Location: North Carolina
Default

Quote "This method is probably a lot more accurate than any blade balancer out there". That would be a negative! The biggest problem with that system, not the only problem, is the fact that you are teetering the blades on a razor blade or main shaft or whatever. This is not very accurate at all. The rotor blades need to be spanwise corrected relative to the pivot or mounting hole in the blade. For that system of teetering the rotor blade on an object to find the spanwise CG you would first have to make the assumption that the pivot hole is drilled in the perfect location on both blades and it will almost never be that perfect.

The correct method or theory of how rotor blades and tail rotor blades should be balanced is this: Both rotor blades should weigh exactly the same thing and their spanwise CG should be exactly the same relative to the mounting hole. How do we achieve this: First weigh the blades in a tripple beam gram scale. Set the scale for the heavy blade. Now cut a piece of tracking tape that will make the lighter blades weigh exactly the same thing as the heavy blade. Now the question is how do we know exactly where to put the piece of tracking tape? The answer is: you use one of the old Schluter blade balancers. It was a teeter balancer for one rotor blade. Basically a threaded shaft with a blade holder on one end and a few heavy threaded weights on the opposite end, with a ball bearing teeter just inside the blade grip. You would then put the heavy rotor blade in the Schluter balancer and set the balancer for that rotor blade. Now you just put the light rotor blade in the Schluter balancer and where ever the piece of tracking tape has to go to get that blade to balance will make both blades spanwise CGs exactly the same, measured against the pivot hole, which is critical.

The one wrinkle in this system or any system is that more often than not the light blade will have a spanwise CG that is further out than the heavy blade and some times it will be enough that when you put the heavy blade in the Schluter balancer and then put the light blade in the light blade will show heavier than the heavy blade. When this happens you have to add weight to the heavy blade, at the tip, not root, as you need to make the heavy blade more tip heavy. Once you have added the extra weight you then have to go back through the process of cutting another piece of tracking tape to make the light blade weigh the same as the heavy blade and then try the Schluter balancer again.

Once you have balanced a set of rotor blades this way they are in perfect balance and assuming your head block doesn't have ten thousands run out and many other factors are in check, your model will run as smooth as my machines do.

I hope this helps


Wayne Mann
__________________
Wayne Mann
www.HeliCamHDmedia.com
WMann is offline        Reply With Quote
Old 09-14-2011, 03:33 PM   #8
Windbreaker
Registered Users
 
Posts: 1,052
 
My HF Map location
Join Date: Sep 2007
Location: Waipahu, HI
Default

The Schuler balance doesn't seem to be available anymore. So while it's useful info, it's not going to help anyone who doesn't have access to one.

Koll makes a balancer that provides both spanwise and chordwise CG measurements. Those who have worked with it have nothing but great things to say about it. At $90 it's a significant investment. Here's a copy of the user manual. If you're building your own blades this is a "must-have" tool.

http://www.google.com/url?sa=t&sourc...VsiIXlZEMtoDxQ

Unless the mounting hole of the rotor blades are radically different from one another (in which case there would be much more serious problems than just balance), the published procedure seems to work very well. I've been doing this and my vibration levels, according to vibration logs from a Skookum SK-720, have been very, very low.

Most of the higher-quality blades on the market are already well-matched. The balance procedures we're using seems to be mostly a matter of fine-tuning them.

That said, having the rotor blade pivot on a narrow edge is a very good way to find spanwise CG. Knife-edge fulcrums are what the best and most accurate lab scales use. This is an adaptation of the same idea. The tape over the edge prevents the rotor blade from slipping too much and keeps the sharp edge from scoring the rotor blade's surface.

Blade balancers that use bearings as pivots aren't worth considering in my opinion. Bearings can go bad. Slight tight spots in a bearing can adversely influence the ability to find a precise balance point. If the balancer is made of plastic, it's subject to warping and distortions from temperature changes and aging.

And the location of blade mounts, if one blade is balanced against the other, have to be extremely precise. You can't get that kind of precision from inexpensively molded plastic. The blades have to be exactly parallel with one another on a two-blade balancer. Otherwise the point of balance would be thrown off.

The procedure described in the website I noted, as well as the one below, eliminates potential problems that would be inherent in balancers such as the one made by Helimax, while allowing considerable precision.

And if someone already has an accurate scale, it could save a few bucks, too.

Here's another posting about how blades are balanced. Note "Blade Balancing Method 2": http://summer.phpwebhosting.com/~healtharts/heli/tune/balance.html

This procedure allows the blades to be balanced, as well as having the chord CG's match, while adding the least amount of weight. Makes a lot of sense.

Anyway, it's an optional method that seems to work well for some.
__________________
Custom quad copter, Cobra C-3525/18 motors and ESCs; APC 15x4 thin electric props. OpenPilot ControlCopter board. Futaba 8FG Super 2.4 gHz FAAST system.
Windbreaker is offline        Reply With Quote
Old 09-15-2011, 08:24 PM   #9
Windbreaker
Registered Users
 
Posts: 1,052
 
My HF Map location
Join Date: Sep 2007
Location: Waipahu, HI
Default

Back to the topic of vibrations...

Keep in mind that I've only been doing this for several months and am still learning more each day. So far I've been able to get my little T-Rex 450 up with a GoPro camera and avoided the dreaded "jello" problem with the camera hard-mounted on the airframe.

Every single moving part on the helicopter can induce a vibration. Figuring out exactly where the problems come from is a serious challenge. But there are many things that can be done to help reduce the "bug" hunt.

Here's what I did:

-- Install a Skookum SK-720 and convert the 450 SE V2 to flybarless. This alone eliminates a small pile of parts that can complicate the goal of getting a nicely balanced main rotor.

-- Switch from wood blades to heavier carbon fiber blades (part of the FBL conversion).

-- Replace the head, grips, main shaft (also part of the FBL conversion).

-- Install stiffer Trueblood dampeners. The dampeners in the head should be firm. No slop.

-- Replace the original swash that had become sloppy from use and abuse. The new one is solid with almost no play. Therefore blade pitch is more accurate and consistent.

-- Replace the main shaft bearings. All bearings should be in good condition. No grittiness or slop. Same with the swash and motor.

-- Observe the helicopter hovering to see if anything is vibrating. I noticed that a tail skid extension I made was vibrating a lot, so I redesigned it and made the tail fin stiffer.

-- Some who fly FBL suggested tightening up the main rotor and tail rotor grips. They should be snugger than what's usual in a flybar setup.

I'm going to try a few different head speeds to see which has the least vibration levels. Harmonics can play a big role, and certain machines are sometimes placarded against certain power ranges since they can induce excessive vibrations. Things might be just fine at 2000 RPM and at 3000 RPM, but shake a lot more at 2500 RPM because of the way a motor is mounted, a frame's natural resonance, etc.

Even if you don't have a Skookum FBL system, it's worth browsing the forum since there's a lot of chatter about solving vibration problems. I guess when you can see the vibrations clearly on a graph, it can become an obsession.

The folks on the Skookum Robotics thread talk a lot about hunting down vibration problems because the SK-720 records a wealth of data about it. It tells them the frequency, amplitude and axis of various vibrations the SK-720 senses.

Based on frequency, one can make a fairly good guess about the source of the vibrations since the frequency correlates to RPMs. Lower frequencies are related to the main rotor. Higher frequencies to the tail rotor and the highest frequencies to the motor.

Blades have to track properly. I read in a tech paper about full-scale helicopters that said blades which track well might not necessarily track in the exact same plane. Interesting. What mattered was vertical vibration in the helicopter itself. Making small adjustments in one of the blades, then taking measurements, can help with this. I'll have to try that, even though I can get blade pitch within a half-degree using a digital pitch gauge.

Tail belts should be lubed so they don't rub within the tail tube. And the tail rotor itself has to be balanced.

I just read that some scale flyers set their gyros to "rate" mode, and not "heading hold" mode. My guess is that it provides a more realistic tail motion. This gradual yaw control might provide a more stable video platform than the hard stops of a gyro-controlled heading. I'll have to try that.

Worn, or slightly distorted moving parts can cause vibrations.

Another thing I learned about shooting photos from full-scale helicopters is that they run smoother in clean air. Hovering over a stationary point can place the rotor blades into its own downwash, and the self-inflicted turbulence can shake the aircraft. Keeping the helicopter moving into clean air can help keep it stable. Avoiding a descent through its own downwash can help, too.

Hope this helps.
__________________
Custom quad copter, Cobra C-3525/18 motors and ESCs; APC 15x4 thin electric props. OpenPilot ControlCopter board. Futaba 8FG Super 2.4 gHz FAAST system.
Windbreaker is offline        Reply With Quote
Reply




Unregistered
Go Back   HeliFreak > R/C Helicopters > Aerial Videography and Photography


Aerial Videography and Photography Aerial Video/Photo from R/C Helicopters

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


Copyright © 2004-2011 - William James - Helifreak.com