Currently working on making this 2 axis head tracker gimbal. Roll is not necessary. It it optimised for FPV slope soaring (gliding). We want it to ultimately sit under an aerodynamic cowl so most of the bumpy edges are not in the air stream. Also both rotation points have their own bolts so that load on landings are not transferred through the servo mechanics as much. This design is for the Runcam Eagle Pro 2.
It’s designed for standard Corona 939MG servos, simple linkage stoppers and galvanised 1.8mm – 2mm fencing wire for pushrods.
I ordered 3 different GY-85 boards from 3 different suppliers to find that all of them had the wrong magnetometer in them. Some even advertised their product with the HMC5883L chipset on them, but when they arrived they where the QMC5883L chipset.
After all this effort to find something without the shipping cost / time from the USA I decided to just get the HMC5883L individually and attach it to the I2C bus of the GY-85 board. The individual boards is called the GY-271. I found this supplier in Chullora in Sydney:
It worked just fine and now the head tracker is working.
You’ll see in the image below that the Honeywell HMC5883L chip is defined with the markings
Where as the 6th page of the QMC 5883L manual shows the markings something like
(Also posted in RC groups)
Would like to get flight stabilization happening so it’s easier to fly FPV with the head tracker initially. At least if I balls it up I can throttle off, let go of the sticks and it will have some chance of landing flat. Would also be able to see compass headings, altitude and battery on screen through the OSD.
Think I’ll start here first and see if it works with that F3 board.
Some others to look at:
Put the motor in and re-balanced it. Flew at around 14:00ish under power with about a 30kt NNE (15.43m/s) for backup glideability. Flew so well. Only hit about half throttle with a 4s. Had heaps of lift, so I’d say I could max out at about 1kg payload with more throttle. Now onto a flight controller before sticking the head tracker in.
Flight weight – 1414g
New COG – 280mm from the L.E.
The Sentach glider worked well today at the Pat Moreton park in about 15-20kts NNE. Videos to be posted shortly.
Flight weight 680g.
COG 310mm from the L.E.
Beautifully smooth flat landings. Some wobbles as expected. The’s alot of drag points. Especially with the flat sides of the nose. Don’t think anhedral would totally fix it because of the nose as it’s obvioualy turbulating when a crosswind happens.
Crashes it once and the wing popped off nicely dispursing the impact force. Plugged it back together and went again.
The angled wingtips wouldn’t stop the tip vortex as XFLR5 shows in the sim.s. would be better to round into them like Gemot. The difference they made to Gemot was nothing short of impressive. Holding Gemots wing in one hand whilst spinning around, with and without wingtips gives a tactile feeling of the drag differnce involved.
More to come soon.
Being a bit too fried to do a proper stability analysis for Sentach, but having enough mind to sketch out the dimensions for the tip twist foil, the above shape emerged.
Designed to fit into the 50mm thick EPS sheet at 7degrees. It should kill the lift and thus tip vortex nicely. Same as Gemot, however Gemot is 7degrees and a far slower and more tolerant foil.
After watching all of the tutorial videos on XFLR5 yesterday I might do a stabilty analysis first…. Hmm maybe…. I also just want to test the head tracker and Sentach is a rough wing, not a refined design.