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CoM, prop clearance, and BOM

A project log for GimbalBot

Gimbaled thrusters, aerospace-grade adhesives, carbon-fiber-reinforced polymers, and inertial measurement units. This is a space project!

zakqwyzakqwy 07/19/2014 at 21:242 Comments

I calculated GimbalBot's center of mass and temporarily added a bright green disk to show its location on the model:

I'm happy with that. During stabilization corrections, the craft will rotate roughly around that point. As was discussed at the beginning of the project, it's important to keep the CoM above the CoP (center of pressure). 

I also took Dave's suggestion and double-checked prop clearance by temporarily replacing the CFRP models with--you guessed it--bright green disks:

The screenshot shows the closest I get; roughly 8mm from the inner servo at 15 degrees inclination or so. I'm not worried about that. Furthermore, I verified that both axes can swing freely through 120+ degrees, so the servo's built-in 90 degree limitation will work fine for end stops. 

I also added some gussets and a model of the servo power supply. The supply (called a Universal Battery Eliminator Circuit) adds about 50g to the model; I'm still under 2kg, so I'm also not worried about that (and the weight is up top, which is great). The new brushless motors/ESCs arrived as well, so I measured 'em up and updated the model. Everything still fits nicely; sadly, the new ESCs aren't bright yellow. Boo.

I finally updated the BOM to include v08 stuff; other than weight (which I'm calculating using the CAD model), most of the bits beyond nuts and bolts are included. Everything other than the CFRP is priced, too. I'll dive in to project finances at length down the road; suffice it to say that I'm paying quite a bit extra to get the best stuff I can get my hands on (well, not the best, but still pretty good). I'm hoping that GimbalBot 2.0 includes some major cost reductions and optimizations to make the platform more accessible to the hobbyist crowd.

All of the CFRP should be in early next week, and then construction can (finally) begin!

Discussions

davedarko wrote 07/19/2014 at 21:49 point
Woohoo :) with every update there comes the urge to press a like button or give a skull which I've already did. So please take this comment as a sign of "thank you for the update and consideration of my concerns" since i cant skull logs...

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zakqwy wrote 07/19/2014 at 22:11 point
Haha! No problem man. It was a great call; I wouldn't be happy if I shredded a prop and damaged the frame on the first run due to a silly clearance oversight.

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