Originally Posted by JussiH
Jack, thanks for taking time to explain in such detail, I really appreciate it, and this info will be highly useful for DIY´ers. The mentioned spreadsheets would also be a very appreciated tool to have available.
The spreadsheets can be downloaded here, they are shared freely. You can run them with the free OpenOffice Calc software. It is best to keep them in the *.xls format for the easiest sharing:
Turn calculators - http://www.rcgroups.com/forums/showp...&postcount=266
As the spreadsheets are now they only go to 40 turns as that is more than enough for propellers. But the Kv numbers progress linear to the turn counts. If 17 turns gives you a1100 Kv 34 turns will give you 550 and 68 gives 275, etc.
If you understand spreadsheets (I don't) you could extend the turn count range of course. The best one to use will be the Turn Calculator 5 as it shows more winds. The entries in the yellow boxes must be from a dLRK wind and most motors are sold that way. The Simple Turn Calculator will also work if you are going to do the same wind as you happen to have. It will also need to be extended for higher than 40 turn counts.
I am currently rewinding some suppo 2208-17. As indicated that means (in this case) a 22*8mm stator with 17 turns, 12 arms. 2 strands of 0.28 with isolation. Original spec is 1100KV.
I could squeeze in 70 turns of a single strand 0.16mm on those. Star configuration in 2 layers as per Alex´s recommandations.
The KDA´s are branded 2208 but the stator is only 5mm high (meaning that its more like a 2205 motor). We got them as kits, so I cant state any original specs on those. Sebastian managed to get 80 turns of 0.16 onto those, but it took a few tries...and it seriously screwed with his Zen more than once...
We are still prototyping, but I will make some KV measurements and post the data soon.
I ran the Turn Calculator 5 for the 2211-17 using the 17 turns and advertised 1100 Kv. If that was a dLRK wind terminated Delta, the numbers should be fairly accurate. As you can see in the image of the lower half of the page 35 turns gives a Kv of 534 in cell G42 for a dLRK Delta wind and 308 for a Star or Wye wind. So your 70 turns would be half of that or 267 for Delta and 154 for Star.
Do you have a data logger that will let you see the current as the camera move and as the magnetic vectoring takes place and fights inertia? I have an Eagletree eLogger and love it for the questions it answers.
Excuse me for any confusion I may have caused in my posts here when I talk about higher and lower Kv's and turns. I seem to often get them confused in my mind and mistate them sometimes. A lower turn count is always a higher Kv and a higher turn count a lower Kv.
And if you did not know it, for the same turn count, changing Delta to Wye lowers the Kv by a factor of 0.58 and changing from Wye to Delta raises it by a factor of 1.73.
Felix is making tests with different windings, and we will also post data for that soon. I need to get past next week, before I can free up time to make new threads and write all the documentation needed. We are collecting data and photos as we go, and there is already a russian spreadsheet with results gathered so far. Alex will translate it so it can be posted here. Here is a link to the original:
I did not design the controller or the software, so I have posted your question about magnetic braking back to Alex. I believe the techique is referred to as magnetic vectoring.
You are correct (as far as I know) about more poles and arms giving more cogging steps and thus more smooth movement. Some of the Dualsky and T-motor navigator series may very well be ideal candidates for larger rigs.
Another very important thing to consider is to terminate the phases onto some really thin and flexible wire. We made the first ones with some rather stiff servo wires and struggled a bit with those inhibiting motion in one direction. Same thing goes for the IMU.
With your permission, I will link from page one to your post above?
Felix's work should be real helpful for this. I never use motors at this low a Kv or wind that many turns with a single strand so there is lot to be learned here.
You're probably right about the magnetic vectoring, I call it a brake because it stops the prop and that is the ESC setting. I think it is essential to countering movement from inertia and the camera weight. I think the gimbal is going to be in nearly constant motion, even though small and nearly nearly imperceptible sometimes, because of the motion of the aircraft.
The transition from solid to stranded wire is easier with our larger wires of course. Some type of winding terminator fixed to the bearing tube or in the backplate might be the best way to go. And from there go to a silicone sheathed stranded wire that is as small as possible. I think I've seen mention of stranded, silicone sheathed, wire that was down around 40 gauge or so. As long as it is as large or larger than the winding it would be pretty good.
In a perfect world the turns will lay side by side and layer on layer, the jamming point is always down in the bottom the "V" between the arms and when turns on adjacent arms meet. Not much you can do about it. Reducing the turn counts on succeeding layers and moving them away from the jam will let you fit more turns if you are not already doing that.
And any and all of it can be shared at any time and place, that is why it is here. I have learned so much from so many in the 5-6 years I have been dabbling with electric RC that I'm just paying back favors. And you needn't thank me again, I am retired, have the time and interest, and you are keeping me entertained for free! Thanks for that!