Logo 10 gets a BALL-mount!

[Hogster]

Hi all!

You all know me well enough by now to know that I'm a tinkerer, and that I don't like going for long periods of time without a project to work on :D Well, after completing the front-mount for the Logo (http://www.rcgroups.com/forums/showthread.php?t=833762) and not being absolutely 100% happy with it (had some flex in it, and visibility was poor at high altitude), I set about dreaming up a ball-mount for the Logo.

I spent the first part of the project struggling to find stockists of balls in the 8 to 10" range .... I started this thread (http://runryder.com/helicopter/t421306p1/) over on RunRyder, but in the end, I found a stockist of 8" and 10" hollow polystyrene balls .... on an eBay shop of all places! :) I bought one of each and eagerly waited for their arrival ....

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/1.jpg


It was at this point that I realised my front-mount had to change ... I couldn't see an easy way to fit one of the balls around the mount ... so the front mount was scrapped (well, taken off and put on one side ;))! I then started designing a whole new front mount, specifically to take an 8" ball.

Unfortunately I didn't take any build photos for the mount, so all you will see is the finished result ... more or less .... :) The design stage was very simple ... just a piece of A3 paper with an 8" circle drawn on it! Everything else was designed around that. With the previous mount (shown in the photo above ... do you like the new orange skids by the way? :D), even though I had tried to isolate the vibration via the soft foam pad between the horizontal brace and the Askman gimble, there was still a hard connection between the two due to the bolt that held them together. With this new mount, I wanted to isolate any vibration as close to the chassis as possible, so I looked into buying some 'lord mounts':

http://img-europe.electrocomponents.com/largeimages/RF254743-01.jpg

The ones I ended up purchasing consist of a thick cylinder of rubber, with studding bonded to plates on either end – therefore there is no hard connection between the two ends – the rubber can bend and flex as much as it wants.

With these in my hands, I could now finish the design. Lots of cutting, drilling and painting later, and this was the finished result :)

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/2.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/3.jpg


The mount itself is made from right-angle extruded aluminium section, cut and bent at 45° at two points to form the shape you see there. I filled in the gaps left by bending the angled section using small triangles of metal which I cut to size and epoxied in place. I drilled lightening holes in the top as you can see.

In this photo you can see the barry mounts in place between the helicopter's chassis and the mount.

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/4.jpg


This is how I mounted the tilt servo by the way:

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/5.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/6.jpg

I will see whether I need more resolution in practice, but that's the same gear ratio I had before and it was fine ... :)


After a lot of carving to get the polystyrene ball-halves to fit around the camera, this was the result:

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/7.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/8.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/9.jpg

Mmm doesn't look too bad! However .... there's always a however :D .... the surface of the balls was pretty bashed up by this point, and it was a VERY tight squeeze to get the camera and all the leads into and out of the ball ...... I needed something with a much thinner wall ......


Enter a Christmas-decoration specialist who stock 200mm plastic baubles!! :D

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/10.jpg

These very cheap (£5) plastic baubles are nice and strong, and other than being a little heavier than I would have liked (200g), I had a feeling this was what I had been searching for all this time!

I proceeded to carefully cut the ball in half using a junior hacksaw..... I must confess at this point that I performed all the following steps on one of the baubles, only to completely mess up the painting stage so I had to start again (it was that bad :o) .... so what you see below was actually the second ball - the colouring was due to earlier testing of the painting process .... :) Good job I bought two eh :D

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/11.jpg

As you can see, I've filled the hole where the bauble used to be hung from (not anymore :D) with car body filler - to the touch you wouldn't think a hole had been there. :) I then marked out the camera opening on one half of the ball and cut it out using a combination of a soldering iron (!) for the rough cutting and a Dremel-style sanding tool for the fine work.

Next I developed a method to hold the two halves of the ball together ....

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/12.jpg

and it's done with .....?


magnets!!

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/13.jpg


Three brackets made from L-section aluminium per half, with one face of each bracket epoxied to the inside of the ball, and the other to a strong square magnet.

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/14.jpg


And now a shot of it mounted:

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/15.jpg


Then, after 3 coats of white plastic primer, 3 coats of fluorescent orange spray, and 2 coats of clear laquer .... it's now bright orange!

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/16.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/17.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/18.jpg


The finishing touch was a black rim around the opening, painted by hand with black enamel ... purely for aesthetics you understand ;)

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/19.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/20.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/21.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/22.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/23.jpg


There are two cables that need to enter the ball, one is the lead for the shutter servo, which enters the ball via a little slot cut next to the left-hand pivot point (looking from the front). The other cable carries power to the camera, and video from the camera to the downlink. This just enters via a hole on the back of the ball (which you can just see in the photo below). The hole is positioned such that even when the camera is pointing vertically down there is still some slack in the cable.

The more observant amongst you might notice that the left hand end of the camera (looking from the front) is slightly higher than the right .... this is an attempt to counter for the natural lean of a hovering helicopter caused by the sideways thrust from the tail rotor - I will have to see if this is enough in practice ....

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/24.jpg


The ball is fixed to the camera cradle by means of this short piece of wood which is CA'd to the pivot rod. Then on each ball half there are two small cubes of wood which are CA'd (using microballoons) to the inner surface of the ball. You can probably imagine how this works without me describing it :)

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/25.jpg


I think I've finished tinkering for the time being now! :D I am interested to see how the vibration isolation works (or not as the case may be) ... unfortunately the weather is rubbish here at the moment so I'm not sure when I'll next be able to fly ...

I'm certainly very pleased with the way it looks now :) The bright orange ball should prove very helpful with orientation when flying up high ...

Hope you enjoyed this little build thread! Any comments/criticism most welcome :)

Cheers!


David :D

[robert1]

nice work once again hoggster, im just getting started on my front mount

[Hogster]

Thanks robert :)

Hmmmmmmmmmmmmmmmmmmm .....

Just goes to show that even though something *looks* nice, doesn't mean for a second that it will work :(

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/resonance_damage_1-5-08_small.jpg ( http://hogster.rchomepage.com/logo10/front_mount/ball_mount/resonance_damage_1-5-08_large.jpg)
(click to enlarge)

Just after take off there was a MASSIVE vibration which shook the ball off its mounts (breaking a hole in the back .... fixable though I think), detaching both tail-boom supports, shaking the battery loose, and breaking the hot-glue holding the receiver battery and receiver to its mount ...... Looks like those Lord mounts aren't going to work for me after all :o Ah well, back to the drawing board :(

I think I will rigidly fix the mount to the frame and isolate the vibration just around the camera ..... *thinks*


David

PS. Onboard video to follow shortly ....

[Hogster]

Ok, here's the video!

http://www.vimeo.com/962375


David :)

[Wbird]

Idea is awesome, looked great as well, I feel for you man, I hate it when that many hours of thought and work fall apart in a few seconds with no results.

On the flip side, you did do a great job and if you keep at it you will get it. I used one of the mounts you pictured (the one with a bolt sticking out each side) and it works awesome for isolation. It may have something to do with location like you already indicated, mine is only isolating the camera cage itself, not the whole mount.

Good luck.

[Hogster]

Thanks for the feedback Wbird :)

Last night I redid the attachment points for the mount, and as many people here (and on other forums) have suggested, the mount is now fixed solidly to the helicopter's chassis. :) I then redesigned the camera cradle so only the camera is isolated using the Lord mounts. See the pics! :D

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/26.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/27.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/28.jpg

That severe vibration bent my main shaft ( :o :o ), so I've now replaced that and earlier today I had a test flight without the ball ..... the video is TERRIBLE! :o :( I think there's too much flex in the mount ...... next step is to fix braces between the two aluminium brackets to hold them together .... will post photos when that's complete.

Ah the joys of design evolution! ;)


David :)

[Ruud Westerhout]

Hi David,

very nice read.

Allow the probably stupid question "why the ball-view". Is this to make the whole more streamlined or something ?

Best regards,
Ruud

[Hogster]

Hi Ruud,

It's a combination of smoothing the airflow over the camera, greater visibility when at altitude and offering some extra protection in the event of a 'heavy landing' ;)


David :)

[Ruud Westerhout]

Hi David,

-smoothing airflow : ok
-greater visibility : You mean like caps seen on SLR camera's to keep the straight sun out ? or that the heli is better visible from down on the ground
-extra protection : well, I am afraid that the one You used does not help too much, I understood it was made from a "X-Mas decoration" :)

Anyway, very nice. I am not only jealous for the results You are able to produce and show here, but also for the time You seem to have to put inside this.

Regards,
Ruud

[Hogster]

Hi Ruud,

Yes I mean better visiblity when looking at the helicopter from the ground.

Hmmm, true the ball isn't particularly strong, but in the event of a crash, the ball will still provide some protection .... better to have a ball than not :D

Thanks for your kind comments! :)


David :)

[Ruud Westerhout]

Hi David,

while watching the movies You presented (through the link You gave here) I came to some other of your videos. The way how that chopper lifted and "listened" to laptop commands I got the feeling that these helis are build to just never crash.

Seeing the video of the cool "orange painted ball-mount heli" not even lifting off really crashed that feeling. Such a contrast.

Hope that does not happen again, looking forward to whatever next build-story. Maybe some time I will get to copy You :
-take the time for it
-create something for myself
from design to build
-(not forget to make photographs while I am at it)
-have fun with the result

Cheers,
Ruud

[Hogster]

Well it seems the solution was correctly identified here by Benski:

http://runryder.com/helicopter/t435196p1/

Where he mentioned that he experienced similar problems and had to fly a few packs through the helicopter before the O-rings softened up enough for the vibration to disappear ...

So I got the heli setup as best as I could, and started flying it. The vibration wasn't too bad, and after each pack the battery I noticed the vibration had reduced in intensity. It's still there at the moment, but it's much better than it was :)

Things have improved to the point where I'm finally able to show you some in-flight shots of the heli with the ball! At long last! :D

Oh, you may remember during that severe vibration a small hole was smashed in the back of the ball? Well I've repaired that :) I carefully put all the pieces back into place, thin-CA'd them there, then carefully sanded over the area until it was totally smooth.

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/30-5-08/ball_repair_1.jpg

Several coats of white primer and fluorescent orange later ....

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/30-5-08/ball_repair_2.jpg

:D


Here are the in-flight shots!

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/30-5-08/just_off_the_ground.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/30-5-08/head_on.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/30-5-08/pointing_up_left.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/30-5-08/ball_angled_down.jpg

These were taken by my Dad with my Canon EOS 40D / 70-200mm F4 IS lens at ISO1600 (it was taken as it was getting dark this evening).

And finally a ground shot:

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/30-5-08/on_ground.jpg

It was very interesting .... when test-flying without the ball, I noticed a definite change in the helicopter's behaviour when I tilted the camera. Because air is rushing down over the camera the whole time, when the camera changes its angle, the air flowing around it will obviously be affected. In this case, I noticed that when the camera was tilted down, the heli suddenly wanted to move forward (after sitting stationary in a hover)! The back of the camera was obviously directing some of the rotor downwash backward, causing the heli to move forward!

Also I was getting quite bad vibrations in the video when flying without the ball as the downwash was making the poor camera bounce around on the soft Lord mounts ....

As soon as I started flying with the ball on, both of these effects were negated :) ... and the heli looked cooler too :D


As well as working on this vibration issue, I've also redesigned my tilt servo mechanism. Initially I just had a 1:1 link from the tilt servo to the camera cradle / ball. This meant that the tiniest movement on the tilt slider on my transmitter would force the servo to start the whole camera/ball moving, and then stop it immediately! This was causing the whole camera/ball/servo unnecessary stress. In search of a solution, I started this thread:

http://runryder.com/helicopter/t434896p1/

... and Tomas hit the nail on the head! By removing the potentiometer from the servo and somehow connecting it directly to the camera cradle, it wouldn't matter what gearing you used between the servo and the cradle, whether it was 1:1, or 1:50, so long as the servo was modified so it could rotate continuously. It wasn't quite as simple as this however, as after dismantling the servo I discovered that the potentiometer formed the bearing for the output shaft! :o Fortunately I had another of the same servos, so I nicked the pot from there, dug out the pot's innards so it could rotate 360° and put it back into the tilt servo. I then extended the wires from the circuit board back to the original pot, which I hooked up to the camera cradle using two output gears (one from the same servo I nicked the pot from, and one from ANOTHER servo! :p) ....

Hmmm, P = 1000W ;) .....

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/30-5-08/tilt_servo_with_feedback_pot_1.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/30-5-08/tilt_servo_with_feedback_pot_2.jpg

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/30-5-08/tilt_servo_with_feedback_pot_3.jpg

It works SUPERBLY! :D I'm currently using a ratio of 1.5 to 2 using two gears I found, but as mentioned above, this technique will work with whatever gear ratio I choose :)

So now it's on with more flying to soften up those O-rings :) It's also been suggested that a higher headspeed might help ....

Will keep you posted! I'm so glad I've finally got the ball in the air! :D

Cheers for now,


David :)

[Hogster]

Hmmm not sure what's wrong with the hosting for those pictures :(

After swapping the blades over yet again the heli is now flying VERY smoothly!! :D The vibration that is present is getting less noticeable in each flight. So much so that I managed to get some successful shots at 1/200s earlier - I've very rarely gone below 1/400s so I'm most chuffed! :D

http://www.horizonimaging.net/rcgroups/aerial_photos/200th_second_shot.jpg

More progress as it happens! :)

Cheers,


David :)

[Wbird]

Great work David, Glad you didn't get discouraged when your 1st one was destroyed. I must admit, I have never been a fan of AP ships without the canopy. Something about your setup has me eyeing up my logo without a canopy. I still have one of my rex's here minus a few electronics. Hmmm.... Possibilities.

Keep it up.

[Hogster]

Thanks Conway :) It makes a big difference to me (even at low altitude) having the ball on there :)

I managed to source some pulleys and belts so I've now converted the tilt mechanism to use pulleys instead of gears. This has increased the ratio of servo-to-gimble from 1:1.5 to 1:2.5 meaning more torque and slower rotation :)

http://hogster.rchomepage.com/logo10/front_mount/ball_mount/4-6-08/pulley_drive.jpg

I ordered them from here:

http://www.rapidonline.com/Electrical-Power/Fans-Motors/Accessories/Toothed-timing-pulleys-and-belts/71294

I drilled the lightening holes in the big pulley which saved me about 10g (down from 55 to 45g), and I modified the small one to screw to the output shaft of the tilt servo. :)

Cheers,


David :)

[Wbird]

Yet another great upgrade. Those Aluminum pulleys look great on there. BTW your servo sensing mod is great.

I might have to see how they are shipping to Canada. Tilt is an option I will be adding once I get a different radio. When I built my mount I had it in mind for a future upgrade.

[Hogster]

Thanks Conway :)

There are other stockists mentioned in this thread which might be worth looking at first:

http://runryder.com/helicopter/t431741p1/

There are some much lighter pulleys around but they mostly seem to be in the US ... which is why I ended up going for the ones above :)

Cheers :)


David

[carguy84]

Wow, that is some serious tinkering! Well done!

I think, if it was my setup, the only thing I'd probably want to change is the inside color of the ball. I'd probably spray paint the inside of it matte black so that there was less of a chanve of getting funning light readings or weird flare rings.

Probably not really an issue, but just something that caught my eye.

Chip-