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Modified CS8 battery plate

Discussion in 'Cinestar Misc' started by Dave King, Apr 24, 2013.

  1. Dave King

    Dave King Well-Known Member

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    OK, you can say I've been a little focused on CG and balance of my copter for the past month. I've bee doing a lot of testing with balancing my copter with hanging it from my ceiling in the basement and doing tests with the MK tools balance feature. I can now share some results with the forum as I have had definetely enough flying time with testing.

    I would balance my copter with a pair of QC 6200 batteries on it, take it out and fly, and check the results on MK tools. What I was finding was that on the initial pair of batteries I set up in my house would have decent balance would be close ( a little off). But as soon as I went to another set of batteries it would be off. I would then get inconsistent results with CG and results through MK tools. I noticed a couple of issues that I needed to correct. Even though I had 2 velcro straps on each plate, the batteries would slide around from side to side a bit on the ends of the batteries as there was really no practical way to secure it from top to bottom. I also was having a hard time mounting batteries at the same exact spots on the plate when changing batteries on location. With my testing, even a little as 1/8 of an inch can through off the CG quite a bit with 2 batteries.

    So I machined an extra battery plate that I had and cut slots in it so that I could bolt rail guide plates to it. I also cut a slot in the middle so I could mount my receiver in the center of the hub instead of the side. The results have been very good and I'm seeing consistent CG results via MK tools and about an extra minute of flying time on average.

    Here's a picture of how it looks right now before I added velcro to the plate. I just used some very light wood for the rails during initial testing but my friend has a little bit of carbon fiber that he's going to give to me that I'm going to cut to shape on a Laser engraver. I was actually thinking of making the rail plates into an L shape so that I can consistent mounting distance (top to bottom) since the batteries hang over the plate. Right now I'm just using a micrometer to measure the distance from the end of the rail to the back of the battery.
    modified_battery_plate.jpg

    I have 10 sets of QC 6200 batteries and I have found a little variance in the width of the batteries (about 1/16") so I setup the width of the rails to the widest battery I had. Even by doing so, the batteries are much more secure and do not move around and I'm getting very good consistent results and fly times. So the batteries are being mounted consistently in the same location, and they are not moving around during flight.

    Another thing that gave me more flying time was I found my booms slide a little bit in the hub. Some moved out as much as 3/8" and some moved in as much as 1/4". After correcting the boom-motor distance and making them all the same I saw an extra minute of flying time. I now see as much as 13 minutes with the Xoar props and 2 QC 6200 batteries.
     
  2. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Dave:
    I very much doubt you'll be able to cut carbon fiber on a laser engraver. I was research that, and the general answer seems to be "don't."
    I have a 60watt CO2 laser and it makes a horrible mess. You'll need either a water jet cutter (and those are reported to cause delamination of the CF) or a mechanical cutter (either CNC or a bandsaw/Dremel) and this generates massive amounts of black dust (consider water mist?)

    Let me know how you get on. You could always just use acrylic as the rails are in compression with the weight of the batteries on them. Also consider using either Velcro or Dual Track on the rails and the undersides of the battery for more positive hold in place.

    I fret that if you ever do a hard landing (aka "landing the way I do" ;) ) has any kind of lateral movement, those screw threads will cut into the LiPo and you may have a LiPo fire on your hands. I don't enough about triggering a LiPo fire, so I encourage anyone else Who Knows About These Things to comment. :)

    Andy.
     
  3. Dave King

    Dave King Well-Known Member

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    Hi Andy

    My school has an Industrial design program and we have all of these fun machines :) I cut the slots on the plate on a CNC machine and agree that I might need to cut the carbon fiber for the rails on it as well as the laser engraver might not like it. Our shop manager was the one to actually suggest trying the laser engraver. The screws you see in the picture are 20 mm long and I have shorter screws. I would glue them on but since I very well might change batteries in the future at some point this would accomodate wider batteries. The rails are actually designed to catch the sides of the battery and not for the battery to sit on top of the rails. I see no need to be on top of the rails because its very secure the wa it is now. I'm in the process of making new rails now and the screws will be smaller and just pentatrating through it. I don't envision the batteries jumping the sides of the rails to the top of the rails. I certainly hope not :eek:
     
  4. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Dave:

    Try doing a Google search for
    cutting carbon fiber laser​
    You won't like the results. :)

    I'm more concerned with a lateral G-force causing the screw threads to cut into the side of the LiPos and thus causing internal damage.

    Andy.
     
  5. Dave King

    Dave King Well-Known Member

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    I have 12mm, 14mm, 16mm and 18mm screws so once I plan on the material and the thickness I will use the correct hardware to where it just penetrates the surface area to get 3-4 threads on the nut. Another thing I can do is make the rails a little wider so that there is ample space between the bolt/nut and the battery.
     
  6. Andy Johnson-Laird

    Andy Johnson-Laird Administrator
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    Hmmm. Won't that extra space act like a loose seat belt in a car, though, Dave?
    It will allow the battery to accelerate into the screw in the case of a hard landing with lateral component -- then it will rip into the side of the battery.

    I might be worrying unnecessarily, of course. But....
    :)

    In case of an impact, I'd want the battery to rip free of the Velcro, fly off the copter and disconnect the EC5 connectors -- then if it bursts into flames it might do so at a convenient distance from the copter.

    Andy.
     
  7. Dave King

    Dave King Well-Known Member

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    Sorry I didn't mean extra distance between the rail and the battery. I mean I would machine wider rails so that the centerline of the bolt/nut is further away from the end of the rail, and thus, the battery.
     

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