It's been a little over two months since Goliath hovered for the first time. Here are some of things that have gone on since then.
First was a trip to the Portland Maker Faire, September 11 and 12th at OMSI. It was a lot of fun showing off the vehicle, especially now that it hovers. Thanks to everyone who came out and checked out the project. I had a lot of great conversations that weekend.
After getting back to the shop and making sure everything was in working order, it was time to get back to work. The first order of business was to finalize some of the hardware. While Goliath hovered, the center of gravity didn't seem to be in the most ideal location. In order to remedy this, all of the hardware needs to be finalized with the flight weight components, particularly the remaining steel pulleys.
This was the same process as before, but since these are idlers and tensioners, no holes are needed for bolts. The last of of these components are complete, with each saving around a pound of weight. There is now only one one steel pulley left on the vehicle, the main engine pulley.
There was also a hiccup with the battery and solenoid. The battery died, likely because it was undersized and was being deeply discharged. A new bigger battery was added with 18Ah, 80% more capacity than the previous battery, but with only 4 more lbs. Some thought was given to switching from the lead AGM type to a Lithium based battery, which would save about 10 lbs. However, the AGM has been demonstrated to work with the high vibration environments.
The solenoid failed again, the second on that's failed on Goliath. It's obvious that the stock lawnmower ones aren't built for the vibrations that Goliath creates. It was replaced with another stock solenoid as a temporary fix, but a heavy duty one needs to be sourced for the future.
Lastly, the temporary Avionics Tray was replaced with a permanent one. This time it was made from 16 gauge steel. It weighs a little more than a pound. The idea is that the added mass will help to dampen the vibrations. The tray is isolated from the frame. using rubber expansion nuts.
I'll have more details in a future log post, but the great news is that between the new engine mounts and the avionics tray have reduced the vibrations that the Pixhawk experiences low enough for it to work now.
Stay tuned for more details.