New Camera Mount Design Advice Please

[jes1111]

btw - sorry, I forgot to mention before - if you can find the way to attach your choice of pulley to a servo spline, the pulley/belt profile you want to go for is not MXL but "Powergrip GT" in 2mm (or maybe 3mm) pitch. MXL is a square-toothed design - lots of backlash - whereas the GT series has round teeth (designed for less backlash).

A profile very similar to the Powergrip series is available (in aluminium) from Misumi (link in suppliers list), called 2GT and 3GT.

 

[Borneoben]

Sorry for the late reply

Thats an intersting point Jes.

The problem is i cant find any pulleys that would attach direct to a servo that are of the power grip profile you mentioned.

With a tensioner on the belt do you think the backlash will be an issue?

 

[Droider]

Very interesting design but what about wind? The flat landing gear looks like it would be prone to wind affecting the rest of the copter?

Dave

 

[Borneoben]

Vibration Isolators

Hi Guys

I have another change to teh design regarding vibration isolators.

How about using Squash Balls cut in half?
Like this

I spoke to the guys at Gelmec and they didnt have any of the stud type isolators that would work in the weight range i wanted. 1-2kg Plus they were expensive at roughly 20 bucks a piece!

Squash balls are availabel anywhere and are availabel in several different firmness.
The Blue dot balls are teh hardest and teh Orange dot are the softest with 4 more in between.


I would epoxy the base of teh Half squash ball onto the frame and then screw into teh squash ball from above with small wooden block inside.

So what do you guys think?

Should I lay off the crack pipe?

Cheers

Ben

 

[Borneoben]

Very interesting design but what about wind? The flat landing gear looks like it would be prone to wind affecting the rest of the copter?

Dave

HI Dave

Yes i know..

I am struggling with a suitable landing gear design that will fit in with my fabircation / manufacturing aproach.

I am trying to minimise the materials and different suppliers as much as possible.

Plus keeping the weight down and strength in the right places.

If you have some ideas i would love to hear them!

Cheers

Ben

 

[Borneoben]

Hi Guys

I am struggling with this design a little i have been trying to work out a decent power system and have realised a few things

I have also been working on my frame design and realised that my weight estimates were a little out! I am now estimating that the AUW ready to fly with camera is more like 5.6Kg's!!!

I have also been doing more research into off the shelf frame kits from teh likes of Droidworx and Cinestar etc to compare my frame weights.
They are in a different league! I dont know why I thought I could build something similar for alot less money!

Will have to search for a reasonbly priced machinist and change my design to suit carbon fibre then maybe i could build something with similar performance.

OR

I could just buy a kit of the shelf and get on with flying instead!!

Which is what I will probably do!

I dont want to spend all this time and effort and end up with a system that doesnt work very well. I guess i should just pay someone else for all the R&D work and buy a Cinestar or something!!

Anyway

Thanks again for all of your help and advice.

I think i may just shelve this project for the time being

Ben

 

[jes1111]

Like I've said in the other thread - don't be discouraged!

In many ways you actually want the craft to weigh as much as possible. Since you won't be flying inside an enclosed aircraft hangar, wind is the enemy. Every disturbance to the craft's attitude/position, requiring correction by the electronics/motors, comes from the wind. So if you can minimise the amount by which the aircraft is disturbed, you'll get smoother flight. One HUGE factor in how much a craft is disturbed by a given wind is how much it weighs! Heavy is good! Light is bad!

As Dave points out, unnecessary wind resistance (particular in your side profile) is also undesirable since it will allow the wind to affect the aircraft more.

 

[jes1111]

Squash balls - interesting idea! Try it!

Not sure you were asking the right question at Gelmec. They certainly have both silicone and wire rope isolators to suit this weight range - but I agree they ain't cheap! The wire rope isolators are €40 a pop!

 

[jes1111]

Sorry for the late reply

Thats an intersting point Jes.

The problem is i cant find any pulleys that would attach direct to a servo that are of the power grip profile you mentioned.

With a tensioner on the belt do you think the backlash will be an issue?

Nobody ever said this was easy, did they?

Given that you shouldn't be using the servo's shaft to support the radial load imposed by the belt's tension, the solution to that provides the solution to the attachment issue, too. A shaft, mounted on two ball bearings, either one each side of the pulley or spaced on one side with a cantilevered shaft. The servo should be mounted so that it has no radial load on it. You clamp the servo to the shaft with one of these. Bearings, bearing blocks, shafts, etc. from Misumi (in suppliers list).


Belt tension has little effect on backlash. The problem with MXL (and its like) is that the square tooth profile means there's only the leading face of the belt tooth in contact with the trailing face of the pulley tooth. There's a gap between the trailing face of the tooth and the leading face of the next tooth. So when the servo reverses, that gap is the backlash. A round-toothed profile means there's no gap (effectively), so when the servo reverses the belt tooth can "roll" within the pulley profile and take up the drive in the opposite direction "almost" seamlessly.

This is a definite example of the 80/20 rule. The last 20% between "okay" and "excellent" will definitely soak up 80% of your time/budget

 

[Borneoben]

Hi Jes111

You seem to be becoming my Multirotor Mentor!!

And i dont even know your name?

You have given me the encouragement i need to carry on with my project.

SO

I have incorporated most of your sugestions into my camera mount.

See the images attached
These are rough designs and not finished still needs much more thought for the smaller details.

Like you said with this arrangement i am not limited to pulleys that fit a splined servo shaft and i can choose the belt tooth profile to suit our needs better.

I am a little concerend about the tilt servo being so exposed like that but those mounts are off the shelf from servo city and work very well for this application.

The next important thing to incorporate into the design is the mounts for the VR Potentiometers that need to be mounted on the end of the roll and tilt axis for servo positioning.

Do we need them on both axis or just Tilt? I am not sure how much roll angle we need in total.

First i need some recommendations for the pots them selves then i can think about how to mount them on the shaft etc.

I am aiming for 90 degrees each way with roll and for tilt, up 30degrees and down 120 degrees.
What do you think?


All shafts will be 6mm BTW.
Will try and find some Carbon Rods at 6mm to keep the weight down as opposed to hardend steel.

Thanks again Jes111
I appreciate your feedback and encouragement.

Cheers

Ben

 

[ovdt]

Bernoeben,

Check out this topic: http://rc.runryder.com/helicopter/t431741p1/

If you're having hard time to find timing pulleys and suitable belts check this store :

http://sdp-si.com/eStore/

The specs are so detailed so you can choose items easily.

 

[Borneoben]

:udate:

Hi Guys

Just thought i would update you all on the current status of my Camera Mountand airframe.

Well I think the deisgn is now finished. I am pretty happy with it at the moment but please feel free to make suggestions.

I have also included a BOM and links to all the suppliers for the parts.

Basically if you include shipping costs i think you could build this set up including a Wookong M FC for 3000usd

When you compare this to buying a cinestar frame and camera mount with the same motors, esc, batteries and FC you will spend closer to 5K.

Specs features are as follows
Airframe
Built from 1/8 aircraft ply laser cut, cheap light and should help absorb vibrations
Carbon Tear Drop Shape arms to reduce vibrations from prop wash
RCTiger Motor MT2826 with 14x4.7 props
RCTiger 40 amp ESC
Wookong M FC
4s 5000mah Turnigy Nanotech flight packs in Parralell
Flight deck where all electronics are mounted is connected to camera mount and isolated from main frame using half squash balls (filled with silicone if needed)

Camera Mount
Built from 1/8 aircraft ply laser cut, cheap light and should help absorb vibrations
Any full size servo can be used
Bearings are all 6x12x4 flanged
All shafts are 6mm diameter
Drive pulleys are full supported so servo does not take any side loads it was not designed for
Timing pulleys and belts use Powergrip GT2 profile to minimise backlash
Gear ratio is 2:1 but there is space for larger driven pulleys to make this greater (just need to change drive belt length)
Roll axis is adjustable side to side +/-20mm
Pitch Axis is adjustable up down +/-10
Roll axis total available movement is +/-30 degrees
Pitch axis total available movement is +30 degrees -120degrees

Total all up weight RTF with Canon 550D estimated to be 5.5Kg
The specified power system should give 10.5minutes of flight time according to eCalc

One possible area of savings could be the FC system I am hoping that the new Open Pilot Pro/INS boad will be significantly cheaper than the Wookong M. Fingers crossed!

I have hit another bump in the road meaning i am not sure if i will build this or not.
Although my wife is very supportive of my hobbies she pointed out that i work 12hours a day 6 days a week and have no free time to have this kind of money tied up in a camera ship
She is absolutley right im not sure i canjustify this outlay at the moment. For once in my life i can afford it but i just cant justify it at the moment!!!
I got out of RC Helicopters as i had allot of money tied up in them and no time to fly and now i want to build something twices as expensive!!

Oh well lets see what happens.

Thanks for all the support and advice i have recieved from you all here it has been most appreciated.

Ben

 

[Borneoben]

More pictures for you

 

[Borneoben]

Last Pictures for you

Please feel free to comment and make suggestions

I am willing to make all the designs open source for anyone else to build it them selves.

I have AutoCAD drawings and I have 3D Sketchup Files

Cheers

Ben

 

[Borneoben]

Bernoeben,

Check out this topic: http://rc.runryder.com/helicopter/t431741p1/

If you're having hard time to find timing pulleys and suitable belts check this store :

http://sdp-si.com/eStore/

The specs are so detailed so you can choose items easily.

Thanks Man

After spending what seems like days going through the Misumi SDP and BBMAN websites i finally found what i needed at SDP for reasonable prices.

Cheers

Ben

 

[jes1111]

Great work! There's some very innovative thinking in this design - and it should be a very effective AP machine. I'd look at launching it with a CopterControl board (if you can get one) - that drops $1000 off the price straight away. The Pro/INS will definitely be MUCH cheaper than a DJI, but don't hold your breath for its release.

 

[Borneoben]

Thanks for the kind words Jes1111

I already have 2 CopterControl boards (one is waiting for repair) so as you suggest that will knock a big chunk off the cost.

Will have to think about what to do....

Cheers

Ben

 

[ovdt]

Hi Ben,

Nice design. Do you think 2mm fiberglass (G10) material will be rigid enough for the camera mount?

 

[Borneoben]

Hey ovdt

Yes i think it would work quite well.

although you will have allot of filing to do!!

The design is based around laser cutting as it allows you to have nice square corners for the tabs to slot into.

CNC routing will work well but the corners will be a pain to file square.

Unless you over cut the slots to creat a kind of T shape??

What do you think?

Ben

 

[ovdt]

Yeah, I have problems creating sharp corners with CNC cutting. They all go round. I have some laser cutting machines in the neighbourhood but they claim that laser can't cut fiberglass. Is that true?

I don't now f T shape will work but I'll give it a try, good idea. Thanks!