Hi all have a small glitch :-( 

I have 4 x emax 2213 motors with the keyed prop mounts

so how do i turn the props upside down to do the compass mot ? 

Or do i just bolt the frame to the ground and do the compass mot

with the props the correct way up ? (just seems a little unsafe) 

sorry if its a daft question 

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I had a similar problem with my hex and decided to leave the props and tie the beast down. There are a lot of ways to do that. A suggestion is to use a piece of plywood as a base and install four eye-bolts on it. Then use a single length of stout cord looped around each arm of the quad and tied off with no slack. Finally (and importantly)  weigh the plywood down with a couple of bricks or such.

Or, Lacking eye-bolts, drill holes through the plywood and feed the cord through them,

Or you might look at the spare tire in your car - if your quad will sit on it nicely all you might need is a length of cord fed through the bolt-holes.

To be safe: use stout cord in a long single length wrapped around arms (not landing gear or other appendages), solid anchors in base, no slack, good knot, plenty of weight.

This sort of lash-up can be handy for all sorts of bench-testing, Obviously you want to stay well clear of the props.

Thanks for the prompt reply :-)

You don't have to reverse the props, just move them around one position.

As each motor turns opposite that means the copter is pushing down not up.

Turning them upside down does not do this.

If you have bullet connectors between the ESCs and the motors just switch any of the two leads and the motors will run in reverse. Because the cross section of the prop blades is variable, running them in reverse doesn't truly mimic normal flying but it might be close enough for you. That's why they recommend flipping the props and rotating them one position. It has the props turning in the correct direction with respect to their pitch to give the best calibration against current flow.

I have a quad which has difficult to remove props so I ended up just laying a heavy piece of lumber on the floor and used nylon straps and bungee cords to make sure the quad was snug to the board. Rather exciting running that at full throttle in the house.

I had my twin boy teenagers hold the hexa down while I did the procedure.  They were not real eager, but dammit, Science!

It was most impressive.  In my small den  I spun the thing up and as it tried to launch itself through the ceiling my boys bravely held on. Got up to about 80% throttle and dustbunnies started flying about, papers flew off the desk.  The cat bolted.  I felt like Dorothy in the tornado until I finally ran out of courage and chopped the throttle.

Very exciting, but in retrospect I think it might be a good idea to attach the thing to some Immovable Object instead of risking ones (suspect?) gene pool.

Rob, I'm hoping this is a joke?

Nope.  Actually did it that way.

Don't tell my wife.

Shudder! If one has ever seen an ESC or Lipo failure under high load, one would never get that intimate with them. Or for that matter a prop failure. Hanging on to or securing the aircraft may seem to be the only issue. It's not. The likelihood of a catastrophic failure? Not real high, but it happens and the consequences can be life-altering. And if injury is avoided the fun may shift to putting out a Lipo fire in the house. The wife will know about that real quick, that's for sure!



It seemed like a good idea at the time.  Not quite at the level of "hold my beer and watch this", plus the boys are strapping young men fully aware of the nature of the beastie and I carefully explained how to hold it down. But you are right, I was not taking into account the remote possibility of a blade coming apart (CF, no less), or some electronic part blowing up, or a frame failure.

So yeah, it was kind of stupid.  Won't do it again. Next time I'll strap the thing to a bag of concrete or something first. And run the test outside in case it explodes.

Clearly you are a man who practices redundancy. Much like your hex being able to continue in the event of a motor loss, with two teens you could lose one and still continue the test. Bravo! I like the way you think.

LOL, I know.  I told the boys they better hold on because one of them is the Spare kid.

Fortunately, they are used to me. Most of my crazy schemes do not result in Boy Damage.

A very handy (and cheap) thing to have is an 18 inch (or so) square of pegboard and a few small eyebolts to make a base onto which a multicopter can be lashed. You'll also need something to  weigh the board down, like a pair of bricks. Makes tests very comfortable, can easily be taken outside (and used as a helipad if desired), craft can be tied down firmly or if needed given a couple of inches of slack to test basic functioning. If your knot-tying skills are rusty make up some tethers using fishing line and keychain-size carabiners or such.   

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