Not much space if you're going on holiday with the family in a Renault Clio. This design fits into a 52cm toolbox with transmitter and all accessories.
Just thought I'll share my crash resistant design that has evolved through many drops and repairs. On impact it is now usually just a matter of replacing a rivet or a prop. The electronics and battery can quickly be removed for installation on another airframe.
The props are 15" RC timers and as shown I get about 23min flight time with a slightly damaged 5000mAh 4cell Lipo at 1500m above sea level, 25 deg C.
The difference in spacing between front and rear props doesn't have a noticable effect on stability and it flies waypoints very well.
I'll post basic plans if anyone is interested or if you want an airframe let me know.
Update: Plans for the airframe
Comments
I do not have the DT700, but I have run quite a lot on the DT750. And BLHeli runs it well on 4S (using demag compensation "3" or "4"). With demag comp settings of "2" and "3" it works and does not lose sync, but accelerations are slow.
I have also flashed one 40A Atmel ESC with the latest SimonK code, and in my setup (4S DT750) it fails (stutters and does not pick up speed) in accelerations. WiiESC I do not have.
I also have a "true" pancake motor, an RCTimer 630kV 4215 and it behaves very much like the DT750.
BLHeli also has a "last resort" option to alleviate demag problems: The "throttle change rate" parameter. Setting this lower will limit how fast power to the motor can be increased. Which helps demag issues, but that can of course also slow down the system.
But in a system where max power is not critical, the best is to reduce battery voltage (go down 1S or more).
Isn't it so that pancake motors are used primarily for their efficiency (many grams of thrust per watt)? And their efficiency is definitely the highest at low power levels (=voltage). For an agile, high power setup pancake motors are maybe not the best choice?
Hi!
The sync loss with BLHeli and the pancake motors caught my attention :).
In BLHeli I implemented SimonKs concept for avoiding loss of sync due to long demag time after commutation.
It is a concept that greatly helps in handling slow demaging motors. And in BLHeli there are several settings for this "demag compensation". It defaults to "1", which gives a minimum of protection. Setting it to "3" or "4" will give much better protection, however at the cost a few percent (maybe 3-4) reduction in max power.
If you have the chance, you may try this.
Thanks,
Steffen
@mdrm: Sorry, I have no idea, but I'll try flashing with SimonK when I have some time on my hands to see if there is a difference.
@Zidlov: Very nice! I'm sure those motors can drive larger props though.
Sorry, I don't know much about ESC's. I'm using standard 2012 JDrones 20A ESC's. Just had to adjust the timing to high otherwise it could hardly get off the ground, as mentioned earlier in the blog.
Curious to see the foldable Alien locust.
Sure Lee, my CG is around 30mm in front of the back plate in the photo above. Just about in-line with the back of the electronics box. My battery is a 5000mAh 4S. It will be safer to have the CG in front of the 1/2 distance point than to have it behind. It doesn't need to be that accurate, but I think you'll notice a reduction in flight time if you go more than about 45mm in front of the back plates since the front motors would be working harder.
No problem at all Andy. Looking forward to seeing it. I've been thinking about using a 3D printer for a vibration isolated pod on top that contains battery, electronics and camera. Possibly just to print the side walls with provisions for connectors then use thin Carbon plate at the bottom and semi-see-through plastic on top.
...and here is a close-up of where I mount it with velcro.
Here is a picture of the GSM/GPRS/GPS Tracker I use. Costs around $100 locally. I secure the battery cover with duct tape so it keeps on working after a crash. Weighs about 50g.
I don't think my magnetometer is defect as it flew waypoints perfectly for the first 8min, but want to try an external compass soon to see if it solves the problem. There are other options as well to experiment with such as adjusting the "compass weight" values (how much it relies on compass for navigation). First I'll just redo all calibrations and compassmot and see if the problem is still there.
@Lee: Longer rear arms sounds like a good idea. It will also give you more space to mount the batteries further aft. If I remember correctly then it is the power cables going to the ESC's that cause most interference, so it might not help to move them out. If you don't plan autonomous missions then interference shouldn't be a problem.
@Chris: The Black Mantra mentioned earlier in the blog seems nice, but has some limitations. If you are not in a hurry, I can consider making an extra frame for you when I build the next version.
Another flyaway yesterday. Again while flying longish autonomous missions in a southerly direction with a crosswind. I'm on vacation and on arrival the compass only started working after recalibration. I suspect I should also have recalculated the compassmot values as they probably also got lost since my last test flights. Fortunately I found the copter, but only thanks to all the tracking systems, especially the GSM tracker. I could track it right into the office of the game lodge manager who had picked it up! Hint: always take a child with you when collecting your copter from someone else's property.
Yes, CG midway between front and back motors and try to keep some shielding between APM and ESC's/PDB. Here is picture of copter before flight. Damage after crash from 80m: 3 rivets and 1 prop.
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