Carbon Fibre Brushless Gimbal for NEX and smaller.

I now have an RCTimer OpenSource BGC board ("Martinez") and a couple of LD-Power Gimbal Motors which are large enough for an NEX or smaller. I looked over a number of BGC frames for sale but they all seem to incorporate metal or glass fibre, both of which do not have the same strength and low weight of carbon fibre. Based on the connection system I had used on the first CF gimbal I built from scratch (servo based), I have come up with this design with the size needed for a Sony NEX and the adjust-ability to balance for any camera of that size or smaller to maintain roll balance. Also, the base plate the camera sits on is deep enough to move the camera back to balance the weight on the pitch axis due to the size of the NEX lenses.

Once I have hand crafted this design I'll post some video. From there, if there is enough interest I may get a batch of these laser cut and put them up for sale. Roughly $30 of 2mm CF board for this and whatever the rate is for laser cutting.

This specific design is for the LD-Power GM4008-57 motors which are 45mm in diameter, 21mm in depth and 85g each. Still need to work out how many poles these motors have to be able to set up the firmware correctly. If anyone knows please let me know? I was planning on using the smaller LD-Power 2208 gimbal motor which was 39g or so but the eBay seller had the wrong picture and weight in the listing.

Thickness is a large factor to the rigidity of the CF. I find the cheap CF 12mm booms with a wafer thin wall that you get all over eBay are strong to some degree but do introduce flex. If the motor / prop buzzing on the end is not close to perfectly balanced you end up with all hexacopter arms wiggling with the vibes it carries through the whole craft. I remember seeing that on my T-Rex 450 years ago when I switched to a CF boom (real not painted AL). If you have managed to track down decent 1mm wall tubes then they should be very hard to bend. And I think you meant >1mm not <1mm.

However, in this case I find the 2mm board I use to be very solid. It won't be hanging a spinning prop off it - if the craft that the gimbal is hanging off already has vibes then without any vibe isolation between the gimbal and the craft you will see the wobbles on the video. Each method of attachment for the gimbal will be different due to the many variances of craft out there so what I design as an attachment point will be very specific to the hexacopter I designed. Either way I will have some form of vibration isolation as the gyro that comes with the BGC won't like vibes.

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John Grouse June 8, 2013 at 12:00am

Slow progress on the prototype. Changed the lock tabs to closed loops for extra strength. Just needs a CF peg pushed through the hole to lock the plates in place. Feels very solid.

GoPro on this size gimbal will need to sit on a raised platform and closer to the front to balance the pitch axis.
John Grouse June 6, 2013 at 12:34am

Updated design with corner clips to increase rigidity and a new attachment method with rubber grommets around the two 12mm CF landing gear booms to help absorb vibrations.
John Grouse June 5, 2013 at 11:39pm
John Grouse June 5, 2013 at 11:38pm

Slowly getting there with the prototype...
John Grouse May 28, 2013 at 3:30pm

Thickness is a large factor to the rigidity of the CF. I find the cheap CF 12mm booms with a wafer thin wall that you get all over eBay are strong to some degree but do introduce flex. If the motor / prop buzzing on the end is not close to perfectly balanced you end up with all hexacopter arms wiggling with the vibes it carries through the whole craft. I remember seeing that on my T-Rex 450 years ago when I switched to a CF boom (real not painted AL). If you have managed to track down decent 1mm wall tubes then they should be very hard to bend. And I think you meant >1mm not <1mm.

However, in this case I find the 2mm board I use to be very solid. It won't be hanging a spinning prop off it - if the craft that the gimbal is hanging off already has vibes then without any vibe isolation between the gimbal and the craft you will see the wobbles on the video. Each method of attachment for the gimbal will be different due to the many variances of craft out there so what I design as an attachment point will be very specific to the hexacopter I designed. Either way I will have some form of vibration isolation as the gyro that comes with the BGC won't like vibes.
Developer

John Arne Birkeland May 28, 2013 at 2:49pm

Sorry for the off topic, but it's kinda related to gimbal construction in general.

R, your CF must be different from what I have. Comparing a CF and Alu plate there is no competition. CF wins every time. Especially if the plates are <1mm thick. Same goes for the tubes I have tested (22/25mm). How thick was the CF in your tubes? Mine are about 1mm.
John Grouse May 28, 2013 at 2:09pm

I'll do the smaller GoPro design once I perfect this one. Should be a matter of scaling it down.
Requests for quotes to cut CF are out so I should get an idea what I could sell these for.
John Grouse May 28, 2013 at 2:02pm

Wow, how did my blog post diverge into CF on 450 heli's? Back to my design, I have found that the 2mm CF boards at the dimensions of this design to be very solid and most importantly light, regardless of what it looks like. If I'm going to slap a Sony NEX on a 1kg frame, trimming extra weight off is going to be high on my list.
Takes a good amount of force to bend them. I may end up with AL for the connection between the gimbal and the multirotor if the rectangular CF tube introduces vibrations, but I think it should be fine. Hopefully the CF board will arrive soon so I can get cracking on it.
Cloud9Drones May 28, 2013 at 11:23am

Count me in as well
Gary McCray May 28, 2013 at 10:27am

Hi Robert,

Nice welded frame, the 4in 1 ESCs seem like a good idea too, although I's guess that isn't where you'll be mounting them.

That looks like 1" or larger square tube and the inner motors have 3 places where it interferes with the thrust, probably unavoidable.

It will be interesting to see how lift varies on your 4 inner motors versus your outer motors.

I'd actually really like to know that.

Nice welds on that thin tubing.

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