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Old Feb 06, 2013, 07:05 PM
ilektron is offline
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With the battery, it is less than 16oz, which is less than 500g. I recently got my hands on some depron, which is lighter than the dt foam w/paper. Also, the point of it being a cube is that it is a flying cube. I've considered a tube, but for some reason I want to make something, that looks like it shouldn't fly, fly. In addition, I wanted a lot of surface area to allow it to get more flight time.

I like the idea of flipping the motor over. I'm close to getting this one built, so I'll probably finish it and determine what changes need to be made for the next one.

I'm working my way through the Japanese ball thread, just a lot to get through.
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Old Feb 07, 2013, 05:30 AM
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One thing you might want to try to get more yaw control is to split the longer control surface in two and add a small wedge between them, to fix some yaw correction in. This should weight less than adding another servo and should not alter the mixing rules you already use.
Old Feb 07, 2013, 12:11 PM
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Quote:
Originally Posted by Brandano View Post
One thing you might want to try to get more yaw control is to split the longer control surface in two and add a small wedge between them, to fix some yaw correction in. This should weight less than adding another servo and should not alter the mixing rules you already use.
Brandano,

That's a great idea, simple and light weight. The off-set needs to be fix into place after testing is completed, during testing the vanes will require off-set adjustment, instead of a wedge, two strips of soft steel cut from a used tin-can glued on each side of the severed vane will allow for tweaking .
Old Feb 07, 2013, 01:53 PM
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I actually really do like the idea of spittle the longer control surface. I'll have to figure out some sort of rig, like mentiond by corocopter, that will allow me to make the split adjustable.
Old Feb 07, 2013, 02:35 PM
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You can cut a tin can with a good pair of scissors, cut strips about 1/4 inch wide by 3 inches long, wrap the strip around a broom handle to set a radius in the middle, straighten out the ends. Epoxy one strip on each side of the severed vane, with the loop-side outward, this will allow for slack in the strips to facilitate the adjustment of the vanes. Before you glue the first strip on, off-set the vanes at least 25 degree.

Kelly
Old Feb 07, 2013, 03:44 PM
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In addition you can also slightly offset the other surfaces as well. This should give you lower overall drag and recover some trim range.
Old Feb 07, 2013, 05:36 PM
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While on the subject of trim, weight trim is extremely important. All single copter VTOL's need to have lateral weight trim set to zero, that is, while hanging on a string un-powered from the center of the motor; the device must hang exactly level. I.e. remove the prop and place a round or square plate in place of the prop, this surface must be perfectly level in static, un-powered conditions.

I use a "paint stir-stick" with a bulls eye bubble level stuck on one end, a large amount of the stick extends beyond the mounting hole to exactly counter balance the bubble.

Using this leveling system allows me to move the battery, servos etc around using carpet double stick tape to find the correct placement of the radio gear. This is the real secret to making a vtol fly correctly and is often overlooked. BTW this works great on 3-D fun-fly airplanes if the plane is balanced using this system, they hang perfectly vertical in a powered hover, making these planes perform extremely well. I've resorted to mounting the battery on a stick extending upward over the cabin area to get things to balance out correctly. I looks odd, but who cares it make the device fly perfect.
Last edited by corocopter; Feb 07, 2013 at 05:44 PM.
Old Feb 07, 2013, 07:36 PM
ilektron is offline
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What are the symptoms of lateral imbalance?
Old Feb 07, 2013, 08:39 PM
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What are the symptoms of lateral imbalance?
Good question.

The craft will tilt off-axis to the vertical plane of the center of the earth (local surroundings) thus it will drift to and fro making it very difficult to hover. You do not want to deflect a control vane to maintain a stable hover, thus the term lateral trim applies to a vtol in hover flight.

This applies to a non-tilting rotor(s) or props. (non-rotor head design) Think simple single-copter design.

Remember that the plane of rotation of the prop needs to be perfectly level for the craft to hover in calm conditions. This is extremely important and is a major factor in the design criteria of military vtols ships. They have special software to tract the weight of all components and the associated "moment arms" (weight X distance).

You have to build your airframe and then move the components around to meet you needs.

Thus you have to match the normal cg location we all know about plus the lateral cg location.

No one said vtol design was easy that has built a successful device...!
Old Feb 08, 2013, 12:56 PM
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Shoot. Looks like my weekend is filled and I will probably have to wait another week to try to get this thing in the air.
Old Feb 13, 2013, 01:07 AM
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Found some time this evening to finish the construction. Just have to run wires and tighten some screws and the construction is complete - for now.

Hopefully this week I'll get my autopilot worked out and running. Can't wait to try to get this thing to fly.
Old Feb 16, 2013, 01:52 AM
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My autopilot is close. Just have to add elevons and it should be ready for flight with just rate controls. I got it to read all 6 channels from the HK 6ch RX batter line, which is awesome. Only have to have a singe cable from RX to autopilot.

Tomorrow, I'll be testing out the control in a controlled environment. Here's hoping I don't destroy it before it takes off.
Old Feb 16, 2013, 02:50 AM
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Quote:
Originally Posted by ilektron View Post
My autopilot is close. Just have to add elevons and it should be ready for flight with just rate controls. I got it to read all 6 channels from the HK 6ch RX batter line, which is awesome. Only have to have a singe cable from RX to autopilot.

Tomorrow, I'll be testing out the control in a controlled environment. Here's hoping I don't destroy it before it takes off.
Good luck with the testing. You can do it tethered with a horizontal cord so you can test fly/ tune with no chance of damage
Old Feb 17, 2013, 12:05 AM
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Holy cow, I think this thing might actually fly. It is late and dark, but I was itching just to do a quick test to see if I'm on the right path. I took it out into my back yard and just did some quick tests. I spun up the motor until it was almost neutral in lift. I gave it some hands free tosses, and it didn't go crazy; it seemed almost stable.

Hopefully tomorrow I'll put some markings on it for orientation and try some tethered flights or something. Planning for possible backyard videos tomorrow.
Old Feb 17, 2013, 02:27 PM
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I'm happy to hear your making progress.

May I suggest some tuning points for PID, I think others may also have some suggestions too.

String it onto a horizontal wire (clothes line).

Turn off the D term, you will not need this feature, do to the high speed oscillations aspects of your craft with its short coupling

Turn off the I term temporally.

Now test run, adjusting in the P term on the pitch axis until you start to get high speed oscillations and then back off a touch, then adjusting in the I term until slower speed oscillation appear, then back off until the oscillation disappear.

Set the roll axis up the same as the pitch setting.

Then you can dial in the yaw axis to off-set the motor torque using only the P term. later you can add I term settings if you want to have a heading hold feature, but leave that out until later.

Good luck and please post some before test flight photos.

Kelly


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