Camera Mount recommedations

ovdt

Member
Hello everyone,

I want to be short and clear :) I'm gonna shoot videos with my babies (QuadroXL and AD6-HL) and it's time to pick-up a camera mount.

After reading Ken's post about averticalview camera mount, I'm considering it.

http://www.multirotorforums.com/showthread.php?169-AverticalView-camera-mount

But Ken says, the best performing mount was HiSight II for him.

I don't want to pay lots of money to caera mounts like AV200. I don't know if it justifies the price with its performance.

I'll be using Canon EOS600D, Sony NEX5. Maybe 5D Mark II ib the future.

I'll be very glad listening to you guys..

Thanks again.
 

Macsgrafs

Active Member
If your good with carbon fibre my advice would be to make your own, they arent really that hard & can be built to YOUR specifications at 1/4 the price!

Ross
 

jes1111

Active Member
I've studied (from afar) all the mounts available on the market for large DSLRs. I quickly came to the conclusion that nothing out there would meet my own particular requirements, that most of them have glaring engineering "issues" that would prevent them from ever excelling at their role, and that (as with multirotors in general) many people skip right by the real issues and focus on the wrong aspects.

(Please excuse me if I'm sounding a bit short tonight - somebody upset me greatly and I'm still simmering ;))

The gimbal has two principle roles: to isolate the camera from vibration and to keep it pointed in the right direction as the airframe rotates about its axes. Unless and until it succeeds on the first task, its performance in the second is largely academic. The engineering profession has been dealing with vibration since forever and the techniques for controlling it are widely understood. Suffice to say that none of them involve pool noodles ;). The vibrations that need to be kept at bay involve a range frequencies between "low" and "medium". This is highly significant, since its extremely difficult to identify/apply a single solution that would cover that particular range effectively. So at least two "stages" are required. Straight away that's difficult with the currently available units since they are designed as "universal" products, i.e. there is little or no accounting for what frame they're being mounted to or the amplitude and frequency range they need to cope with. To be truly effective, the gimbal must be designed as one with the airframe.

Ask an engineer to calculate a solution for any vibration problem and their first question will be "what sort of weights are we talking about here"? Mass is extremely important - a solution that works for a 1kg payload may be completely useless for a 2kg payload. In fact, it's much more difficult to isolate a light object than it is a heavy one.

So, assuming we've managed to block any vibration from reaching the camera, its sole remaining task is to keep the camera "still" while the object it's attached to moves. The mechanisms employed in all the commercial units I've seen are, by definition, incapable of succeeding 100% in that task. Hobby servos have "backlash" (a dead-zone where the rotated mass is "uncontrolled"). This backlash means that every time the servo changes direction (which is obviously happening constantly) there'll be a jolt through the drive system which will reach the camera. The servo is (usually) driving a gear system or a belt drive, either of which also have backlash in them, so the problem is multiplied. Then there's the accuracy issue: most servos are very low-resolution devices (for this task) and they can have poor "repeatability" (i.e. ask them to move and then go back to exactly the same place and they can't).

Speed is obviously vital: speed of reaction (latency) as well as speed of rotation. If the servo doesn't react quickly enough to a position command hten it will never be "up to date" with the stream of commands coming to it 50 times a second. Once it is moving, if it can't get to the commanded position fast enough then once again it will always be behind the game. The heavier your camera is (plus the weight of the rotated parts of the gimbal) the more power will be required to get it moving (against inertia) and then accelerate it (and stop it).

So how come the "manufacturers" don't fit the best, most powerful, fastest and most accurate servos available? In fact, I've not seen one even disclosing/discussing the servos they provide, or offering any meaningful advice if they don't supply them. All the shiny carbon fibre or laser-cut logos are just bling if there's nothing to match it "under the hood".

I mentioned the command rate (50Hz) above - the rate at which the controller issues new positional commands to the servos. Most digital servos will accept a PWM command rate of at least 250Hz, and should be happy being driven at 333Hz. Doing so will make a big difference, but I don't see it being discussed. Voltage, too - makes a huge difference - your servos should be supplied from an efficient switch mode power supply (at or slightly above their rated voltage), otherwise their performance (and your results) will decline as the battery source drains through the flight. Lots of power is needed, too - a pair of powerful servos can easily pull 8A peak between them. If the supply is not up to the job (like if the servos are powered only from the controller) the voltage will dip - which may account for many unexplained FC "freak-outs".

Coming back, briefly, to the frame vs. gimbal issue and the de facto practise of hanging the gimbal under the centre of the frame: that's not a good place to put it. In fact, it's the worst place, by far. Aerodynamic drag, displacement of the vertical CG, increased moments of inertia, mechanical stresses, crash vulnerability, redundant supporting framework, compromise to the roll axis mechanism, etc. - there's a long list of reasons.

I don't mean to be discouraging here. I guess its a question of managing ones expectations. In spite of some brutal price tags, there is no acknowledged "reference" gimbal, a standard to which all others are compared. I find that significant - it confirms an immature market were neither suppliers nor buyers are yet confident enough to pronounce a clear leader. In my opinion, no clear leader will emerge as long as we're locked on to the current pattern.

In terms of what to buy now, the "usual suspects" are known to this group and there's plenty of discussion about how to make them actually deliver what they promise. But I'd tend to agree with Ross - build your own, at least for now. That's what I'm doing - the new CNC router arrives in 3-4 weeks ;)
 
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Bartman

Welcome to MultiRotorForums.com!!
jes1111, regarding the placement of the camera mount under the heli, i'm not quite sure i agree anymore with the position that it's the worst possible place. I think mounting it the way they've been mounted is prone to creating some unsolvable control problems but I'm starting to think it's not all bad. Look at a single rotor heli, the entire airframe is below the rotors and they're the gold standard for aerial video, full scale and models. I think the mounting is critical and I've got a few ideas of my own that I'm pursuing so we'll see how things work out. One thing I'm doing is adapting DennyR's use of model car shoack absorbers since they are the go to mechanism in engineering for controlling vibrations or oscillations. I had planned a mount using them in one of the first threads I posted when the forums opened but what I'm doing this time around is more in line with Denny's design. What's interesting is that it'll be similar but so so different that it should, at the very least, provide some information for DennyR to reference against his own design efforts.
All good stuff for conversation and learning.
Bart
 

baker55

Member
I have a pro-mount 200. The more I use it the less I like it. I need to adjust the roll about every 5-6 flights. There is a hoky flat washer on the roll potimetre that covers a hole that seemed to be machined too large. It comes loose all the time and needs to be adjusted and tightened. This is my first mount so I don't have anything to compare it with. I carry a Canon 7d sometimes so I thought I needed it. Is there something else out there that works better?
 

jes1111

Active Member
Helicopters have their blades above the fuselage for obvious practical reasons - getting on and off the aircraft would be a bit hazardous if they were anywhere else ;). Plus there's a flexible joint between the two, so tilting the rotor doesn't need to fight the inertia of the fuselage. I'd agree they are "the standard", but only because until recently they were the only available way to position or move a camera in 3D space. Multirotors are emerging as a new and more accessible way to do it on the small scale stuff, but I reckon they need to progress to the next generation before they firmly displace model heli's for anything but the heaviest lifts.

In terms of "the physics", the underslung weight of gimbal and camera compromises the control capability of an MR. We can use 4, 6 or 8 fixed pitch blades to do what previously needed a very large and complex heli head because the centre of thrust (and therefore the centre of rotation) is (roughly) coincident with the centre of gravity, minimising the differential forces required to effect manoeuvres. Move the centre of gravity away (and increase the moment of inertia on the pitch and roll axes) and you "dull" the capability of the craft to stay level (against wind displacement) or manoeuvre with agility. Think of a really exaggerated case: fix the gimbal on the bottom end of a stiff (but weightless) 10 metre rod. You can imagine how hard the motors/props would have to work to correct errors or move to your commands and it's obvious that it would be really slow to do anything.

A much better scheme would be to mount the gimbal on a universal joint (with some appropriate damping), so that it could remain level independent of the airframe above it. There'd be an obvious problem of getting the blades in the shot when travelling, but from a controllability viewpoint it should be much easier. Maybe somebody will try that soon.
 

DennyR

Active Member
One thing that I should mention is that those car shocks don't have any oil in them. I usually remove the piston as well and rely on the friction cap that compresses an O ring. and that provides enough dampening with light lubrication. A fully operational damper will transmit vibration.

Denny
That's an interesting point. I figured I'd have to open up the transfer holes and use really light oil to keep the damping light enough but I hadn't considered using something that dampens vibration with just friction drag alone. That has the potential to simplify things a lot and I can probably make something in the basement rather than spend $30 to $80 on shocks although I don't think I can return the $30 set I've already bought and opened.
Thanks,
Bart
 
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Macsgrafs

Active Member
Denny
That's an interesting point. I figured I'd have to open up the transfer holes and use really light oil to keep the damping light enough but I hadn't considered using something that dampens vibration with just friction drag alone. That has the potential to simplify things a lot and I can probably make something in the basement rather than spend $30 to $80 on shocks although I don't think I can return the $30 set I've already bought and opened.
Thanks,
Bart

I have been flying an askman mount with shocks for nearly 3 years & it does need to be full of oil, without it the sudden bottoming of the shocks causes terrible judders.
I turned it from an underslung mount to a front mount as it made orientation a lot easier at altitude.

Ross
 

Macsgrafs

Active Member
A much better scheme would be to mount the gimbal on a universal joint (with some appropriate damping), so that it could remain level independent of the airframe above it. There'd be an obvious problem of getting the blades in the shot when travelling, but from a controllability viewpoint it should be much easier. Maybe somebody will try that soon.

The problem with a UV coupling is that centifugal force causes it to swing out madly in a turn!
 

Bartman

Welcome to MultiRotorForums.com!!
A much better scheme would be to mount the gimbal on a universal joint (with some appropriate damping), so that it could remain level independent of the airframe above it. There'd be an obvious problem of getting the blades in the shot when travelling, but from a controllability viewpoint it should be much easier. Maybe somebody will try that soon.

This is exactly the scheme I was referring to in my original Son of Okto posts in the build thread area. Four point stabilization with shocks and gravity working on a universal joint to keep it level. Simple and unbeatable response times. The challenge is to make it with adequate movement and then fly strictly within that limit. I'd guess a bunch of trial and error would be involved to get it optimized. I've got the frame started for that project and the plans are pretty well developed in my head so maybe this winter I'll finally have the time to bring it to life.

Bart
 

Bartman

Welcome to MultiRotorForums.com!!
The problem with a UV coupling is that centifugal force causes it to swing out madly in a turn!

it would have to be a CV type joint to constrain rotational movement. i've got the hardware picked out already, just haven't had the time to or money to work on it.
bart
 

DucktileMedia

Drone Enthusiast
You are giving me ideas. When i was trying to make a cable cam (pre-heli days) I had a similar idea of making a simple gyro under the camera that would just add enough inertia to smooth out motion. The camera would hang from a universal joint and be free floating. I like this idea for making a real "flying" sensation from the video. If the camera is "locked" in position it doesn't have that superman flying feeling. I look forward to trying this soon. The question is, can I get a motor to spin an aluminum disc fast enough and still be light weight enough to fly?
 

Bartman

Welcome to MultiRotorForums.com!!
that would be for gyro stabilization, as in spinning gyro, right? hadn't thought of adding that but it makes sense if it's heavy enough to resist moving out of its plane in which case it impart a lot of additional movements
 

jes1111

Active Member
@windhorny: this chap - http://www.myresearch.lt/blog/onboard_camera/onboard_camera.phtml#Anchor-Positionin-41640 - has done a lot of trials with mechanical gyros.

@bart: thinking about it now, there's four possible approaches (that I can think of). You could:

1 - regard the total system as a 5 axis (like the commercial Cineflex-type units): the "damped gravity-driven" CV joint acts as the "outer" roll and pitch axes, giving a "conventional" gimbal (the "inner" system) less work to do the final little corrections that the "crude" outer system misses
2 - have a fixed camera platform and use the "damped gravity-driven" CV joint as your only stabilisation.
3 - have an "active" CV joint, driven by linear actuators, with a conventional gimbal "inside" that (as #1 above).
4 - have the active CV joint (as #3) with a fixed platform (as #2).

My gut feeling is that #3 would give the best results, but it's obviously going to be heavy and complex. Not sure how well the passive versions would work - passive dampers might not be "tuneable" to cope well with the full range of angular accelerations you'd experience. And there's still the problem of encroaching props when travelling at speed. Fun to think about, though.

@Denny - what can I say? :cool: I didn't mention your excellent machines in my post because I didn't think you were going to go "commercial" with them. I bet the price-tag on that mega-mount will be beyond the reach of smaller operators, but I'm intrigued and await further announcements.
- what happened to your original post? A glitch in the machine, me thinks.
 

ovdt

Member
Thank you guys for those great information you gave! I would build my own but I've never seen a camera mount so I need to have one to see the weaknessess so I can build a better one. I think I'm gonna buy something used to save money.
 

DennyR

Active Member
Jes I have been so flat out recently that I have not had the time to check out the posts. I do have a new machine that I think you guys will like. I just wish I could get my hands on a couple more CC boards. Any news when?
 


DennyR

Active Member
Getting back to the dampers, The Panny 900 is a very difficult camera to mount. and I know many people have given up with this. If you have a heavy camera like a 5D then you need the dampers to be fully operational to gain any effect. However the Panny is much more sensitive to vibration and I found that the damping was Too strong and it was starting to jellow etc. during hard movements. Hence the softer option was a complete cure.
 

DucktileMedia

Drone Enthusiast
The Panasonic 900 you are referring to is the tm900, right? This would be great info to have asap as i was just about to order this. After trying one in my hand I was pretty sure the unit would be ideal for AV. But if you are saying the OIS is too much then I am all ears. Do tell more.
 

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