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Revolution Models . CarbonXtreme . Midland Helicopters

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Aerial Photography and Video > My attempt at a mount
 
 
JCadwell
Key Veteran
Location: Richland WA/ Morro Bay, CA

I've prototyped this mount in aluminum, made a few changes, and cut it out of FR4 G10.

The servo is reduced 3.3:1 using Traxxas plastic spur gears out of an RC car. 6$ for both gears. The black plastic spur gear has a 24 tooth pinion underneath it, and the pot is wired back into the servo and has a 28 tooth gear on it. This allows the mount to rotate to get my desired output sweep.

All bearing blocks are delrin, and it's assembled with stainless button heads.

The microservo is for shutter actuation of my cheap digital, but I hope to upgrade sometime soon, so that mount is removable.

I still need to build the pan gearing out of the same parts as above, and build a carriage for the front of my Robbe Futura SE gasser.

Thought I'd post some pictures. Some advice or feedback about what to improve would be most appreciated.

Thanks, John Cadwell
05-12-2004 Over year old.
 
 
JCadwell
Key Veteran
Location: Richland WA/ Morro Bay, CA





Thanks, John Cadwell
05-12-2004 Over year old.
 
 
ImRich
Veteran
Location: Derry, NH USA

John,

Good job, it looks great. How is the weight.

Try to allow for a variable C/G of your camera. You want the tilt axis to be right at the C/G of your camera so a little adjustment will help if you try different cameras.

---
Rich
05-12-2004 Over year old.
HOMEPAGE  
 
 
JCadwell
Key Veteran
Location: Richland WA/ Morro Bay, CA

Right now the camera is just below CG. It is variable, as the camera is small and the mount is shimmable. I'm hoping to go with a better camera and remote shutter.

It weighs 402 grams as seen right now. A little heavy I think. I need one more servo and the associated gearing for all up weight. How much do these mounts usually weigh? I think I could go lighter if it is a problem.

Thanks, John Cadwell
05-12-2004 Over year old.
 
 
FCM
Elite Veteran
Location: Back in Blighty!

Is that a standard servo pot?

Hi John,

Looks like a real nice job you have done with your mount. I would get it finished and test fly it before making too many changes as you are bound to find some minor items that need sorting after it's first flight/shoot. Can't give you a typical weight as my system is integral with the heli and I have never weighed it! What are you going to use as a helicopter?

I would like to know if the pot you are using came out of a servo or if you are using something different.

I have been experimenting with remote pots on my mount but have been unable to find a reliable way of driving them i.e. find a drive system with no play and with good resolution.

Paul.
05-12-2004 Over year old.
 
 
JCadwell
Key Veteran
Location: Richland WA/ Morro Bay, CA

It is a 1/4 watt 16mm Philmore pot, not stock. There doesn't appear to be much lash. If it becomes a problem I could try self loading antibacklash gears.

Right now I'm fighting to mount it on the front of the airframe, but that doesn't look like it will happen without major modifications. It will probably end up under the heli in a carriage. Oh well, I really liked the front mount idea. I think it would just be too much of a CG fight.

Thanks, John Cadwell
05-12-2004 Over year old.
 
 
FCM
Elite Veteran
Location: Back in Blighty!

John,

You've got me there - what are 'self loading backlash gears' and where would you obtain them from?

Thanks for the pot info. I'm pretty much 'electronically illiterate' so I have to rely on you guys who know this stuff!

Paul.
05-12-2004 Over year old.
 
 
Greg McFadden
Key Veteran
Location: Spokane Valley, WA

https://sdp-si.com/eStore/PartDetai...095&GroupID=205

there ya go, that is an example of an antibacklash gear

The silence often, of pure innocence persuades, when speaking fails
05-12-2004 Over year old.
 
 
JCadwell
Key Veteran
Location: Richland WA/ Morro Bay, CA

The picture is as Greg put up. There is one gear face that is attached to the hub, and another that is spring loaded. You rotate the spring loaded face when you install it to preload the spring to whatever level you want. There is then no slop though there is give in the system due to the spring. If you overpower the spring you have give, but it is preloaded, so a part of the gear is always touching the face of the gear you are meshing it with.

Thanks, John Cadwell
05-13-2004 Over year old.
 
 
FCM
Elite Veteran
Location: Back in Blighty!

Thanks John and Greg, this certainly opens up some more possibilities for me to play with.

Regards, Paul.
05-13-2004 Over year old.
 
 
JCadwell
Key Veteran
Location: Richland WA/ Morro Bay, CA

Have you considered toothed belts? Timing pulleys. SDP-SI, the company Greg linked to, sells all kinds of neat stuff like that. They aren't expensive, but you would have to lay out your design in CAD and make sure you ordered all the right parts from the beginning. One shot ordering... Maybe Malaysia has a "Pulley Mart" but around here we don't have much that isn't mail order.

Thanks, John Cadwell
05-13-2004 Over year old.
 
 
FCM
Elite Veteran
Location: Back in Blighty!

John,

I think that a toothed belt would be easier to use on my mount. I can make some parts myself as I have a lathe/mill but I cannot make gears or toothed pulleys so maybe I can buy them from SDP-SI and modfiy them to fit my system.

I think I need a 2:1 reduction ratio for the pot - this is using a pot from a JR servo that I have mounted in a 'cage' as I had originally intended to use a round section rubber belt but I couldn't get this to work as it would slip and this is not what you want on a feedback system!

If it had worked, I estimated I would get 200 deg of pan (standard servo pot gives approx 100 deg if I'm not mistaken) which would be just right as any more and the helicopter comes into view on the video image (close-up of the skids - my favourite shot - NOT).

I wonder if using a pot like the one you have on your mount would enable me to use a different ratio?

Thank you for your help.

Paul.
05-13-2004 Over year old.
 
 
JCadwell
Key Veteran
Location: Richland WA/ Morro Bay, CA

The pot I used has the same value as the one in the servo. I removed the one in the servo. The hope is that the new pot is more rugged than the servo pot.

What gear reduction are you running for the servo mount from the servo?

Thanks, John Cadwell
05-13-2004 Over year old.
 
 
FCM
Elite Veteran
Location: Back in Blighty!

The gear reduction is 3:1 and is achieved with a nylon chain driven by a 12 and 36 teeth sprockets. This does give a smooth action but I have always struggled (or my cameraman has) with the non-centering action of the servos. It is my belief that if, like with your mount, you have 'return to centre' servo action then it will be much easier for a camera operator to get used to using the camera system and you could achieve more effective video footage this way.

Regards, Paul.
05-14-2004 Over year old.
 
 
JCadwell
Key Veteran
Location: Richland WA/ Morro Bay, CA

The only problem might be getting the camera stable enough and then snapping the picture. I like the panning idea, and am going to be using a couple of pancam modules I'm building. You could also just remove the pot and solder in a couple of resistors to acheive this, but that doesn't give you any limits to motion, and could let you tear equipment up.

Thanks, John Cadwell
05-14-2004 Over year old.
 
 
FCM
Elite Veteran
Location: Back in Blighty!

John,

That's an interesting point about getting the camera stable enough to take a still image.

I have been looking at this from a video point of view which is, I guess different to what you need for a still camera. With a still image you want to be able to set the position (with or without any stabilisation) and take the shot. With proportinal control you will have to 'hold' the stick at a given position which does not sound as though it would be an easy thing to do to me.

With video although the (non-proportional) system I have works okay as it is, the problem of the cameraman losing orientation due to the fast changing flight path of the heli, is a real challenge that I believe would benefit from real proportional control just like we fly with.

Looks like it would be best to run proportional for video and non-proportional for still.

Any comments anyone?

Paul.
05-14-2004 Over year old.
 
 
Greg McFadden
Key Veteran
Location: Spokane Valley, WA

with proportional, why not just map to one of the non-return to center sliders that are on most good transmitters nowadays. with a little practice you'd get a good compormize

The silence often, of pure innocence persuades, when speaking fails
05-14-2004 Over year old.
 
 
FCM
Elite Veteran
Location: Back in Blighty!

Sounds like that would work. I was thinking of using the R/H stick which is the way I have my cam Tx arranged (aileron/elevator) but I don't see why you have to use a stick at all for the camera function. Might actually be easier to use a slider - sounds like a good idea to me and worth a try if and when I achieve proportional control that is.

Paul.
05-14-2004 Over year old.
 
 
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Aerial Photography and Video > My attempt at a mount
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