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Old Jul 26, 2015, 04:53 PM
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Quote:
Originally Posted by kpinnc View Post
I was actually looking at the same thing- but will use a 12mm CF tube and multirotor mounts. That way, you can adjust the angle to whatever amount of down force you need. Also, you will gain clearance for very large props- so you can use more efficient motors.
Nice design! Sounds like we're on similar tracks. I just picked up a 16mm CF boom with multi rotor motor mounts from a friend.

This is going to be fun
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Old Jul 26, 2015, 05:05 PM
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Quote:
Nice design! Sounds like we're on similar tracks. I just picked up a 16mm CF boom with multi rotor motor mounts from a friend.

This is going to be fun
Well, I always thought the idea of down force on anything that is fighting to provide lift in the opposite direction is just plain silly. I've got some bearings that will fit over my tubes as well, so I'm going even sillier than just two motors...

Boats use outboard trim for getting up off the water, and then adjusting thrust for efficiency afterwards. I'm thinking of something similar on the Ranger. Tilt the motors up 5-7 degrees for takeoff, but rotate back to 0 for efficiency after takeoff.

It might not work, but there's one way to find out...
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Old Jul 26, 2015, 05:47 PM
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Goooo!!!! Get to da choppa!!!!
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Quote:
Heat loss.
Power = I squared R = Heat loss

All motors are inefficient so the power that is not used is wasted in heat.
Also if you use 2 ESC's then each one will generate heat, and therefore more power lost.

The advantages might be;
Smaller motors,
smaller props.
less current
big 3s batteries

It sounds like a fun experiment.
I'm curious to hear about the results.
All things being equal, I would agree. The limiting factor of the Ranger though is how large the prop can be, so that is where the problem is.

Also, I'm working with what I currently have- rather than an open budget. I have oodles of motors, so I'm gonna make what I have work the best I can.

I have several 4s batteries that I can hook up in pairs:

4 each 2700mAh
4 each 4500mAh
4 each 3000mAh

I also have lots of SunnySky 22xx and 28xx motors, and ESCs ranging from 20-70 Amp. This is why I have to pick from.

My strongest motor makes over 7 pounds of thrust with a 1247 prop, but draws 57 amps at 100% throttle.

By comparison, my most efficient motors make 4 pounds of thrust EACH with the same prop, but at 18 Amps at 100% throttle. In essence, two of these would make more thrust (while cancelling each others torque) while only using about half of the current draw. I doubt very seriously that a 12mm round carbon rod will create enough drag behind the flaps to null out the added power.
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Old Jul 26, 2015, 06:37 PM
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Quote:
Originally Posted by kpinnc View Post
Boats use outboard trim for getting up off the water, and then adjusting thrust for efficiency afterwards. I'm thinking of something similar on the Ranger. Tilt the motors up 5-7 degrees for takeoff, but rotate back to 0 for efficiency after takeoff.

It might not work, but there's one way to find out...
Brilliant!

So to have counter rotating motors, do I need (say) a 10x5 pusher prop and a 10x5 tractor prop on a reversed motor? The PNP motor spins a 10x5 and I'd like to stick with what I know works, and I just so happen to have 2 of the PNP motors.
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Old Jul 26, 2015, 07:41 PM
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Brilliant!
Well, we shall see LOL.

Quote:
So to have counter rotating motors, do I need (say) a 10x5 pusher prop and a 10x5 tractor prop on a reversed motor? The PNP motor spins a 10x5 and I'd like to stick with what I know works, and I just so happen to have 2 of the PNP motors.
Yes, but don't use "slow fly" props like multirotors use. They are more like ceiling fan blades than airplane props. They're designed to hover in still air, not for maximum thrust in air moving 50 miles per hour.

APC and any other decent prop maker sells tractor and pusher sets.
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Old Jul 26, 2015, 07:59 PM
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Originally Posted by kpinnc View Post
Well, we shall see LOL.



Yes, but don't use "slow fly" props like multirotors use. They are more like ceiling fan blades than airplane props. They're designed to hover in still air, not for maximum thrust in air moving 50 miles per hour.

APC and any other decent prop maker sells tractor and pusher sets.

Gotcha. Thanks!
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Old Yesterday, 06:23 PM
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This should do the trick! (tractor prop has been ordered)

Now I just need to find a good mount to hold the boom and screw into the original Ranger motor mount. I'm thinking the mount in second picture should work. Hopefully I won't need to add so much weight to the nose that she won't fly..
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Old Yesterday, 10:49 PM
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Has anyone else bought the airoscar pitot mount from Shapeways ?

Bit disappointing. It doesn't fit. Completely the wrong size. Maybe i have the wrong airspeed kit ?

I have the HK Digital airspeed sensor.

http://www.hobbyking.com/hobbyking/s..._Tube_Set.html

Edit:

Yup, looks like I need the 3DR pitot tube.

Anyone know where I could buy the tube seperately? I can only find the complete airspeed kits.
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Last edited by mrfirkin; Yesterday at 11:19 PM.
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Old Today, 04:30 AM
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The airoscar pitot mount is the ducks guts bytheway. Way cool !

http://www.shapeways.com/product/NTA...ionId=56183701

You NEED one of these if you have a FC with airspeed sensor.

They even supply a small template to mark the cutout in the fuse.
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Last edited by mrfirkin; Today at 04:35 AM.
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