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Nov 04, 2017, 10:21 PM
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Origin Hobby Acro 1.1M Motor Glider

The Origin Hobby Acro is a motor glider of about Bixler size and it's an ARF made of foam, so when I won one in a raffle and need to set it up, I'm starting a discussion over here in what looks like an appropriate area. There is a thread over in Sailplane Talk that started when the Acro was new, with pictures.
Comment is dying out over there, probably because the Acro is not really a sailplane. From a distance it might look like one, but the wing isn't as big as a Radian's. At 1.1 m wing span, with area of 256 sq inches or 16.5 sq decimeters. and weighing 2 pounds or a bit more, according to the manual. it's more like my HobbyZone Valiant 1.3M. That's a fair floater so I'm looking forward to some fun with the Acro.

The Acro has a feature that some in the original thread have called a gimmick. It has a servo attached to the motor so it can be pointed left or right on command. This allows getting into some nasty looking flat spins. I've just gotten hold of a Taranis QX7 Radio, which the proficient user can program to do anything, so wiggling an airplanes nose should be no problem. I've gotten a start on that, and have already mixed that servo with the rudder as suggested in the Acro's manual. I can use a pot on the Taranis to trim the Acro thrust line for straight flight too. Some folks over in the radios area are helping me with this. They suggest I can make the sensitivity of the rudder mix variable with a pot also, to tune the "wildness" of the spins.

Like any fairly inexpensive ARF, I found a few minor things I needed to change. The clevises on the rudder and elevator push rods had screws that go through the control horns that were too big for the holes in the horns. I changed them out for 2 X 56 machine screws that fit through the holes and allowed the joints at the horns to pivot like they are supposed to. These smaller screws needed a nut and some CA to secure them from falling out of the clevises. Trading a minor problem for a major seemed fair. Now the servos won't be bowing out the push rods, because of the bind at the horn pivot.

Next thing I need to resolve is how to get the ESC, receiver and 2200 mAH 3S LiPo battery into the front hatch space and have the plane balance properly.
Any hints?
Last edited by DuPageJoe; Nov 18, 2017 at 04:44 PM. Reason: I checked again and unforunately it does weigh 2 pounds with the battery
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Nov 06, 2017, 05:00 PM
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Some pictures of my Origin Acro mods.

I weighed the parts of my Origin Acro a second time, and found it as heavy as advertised. Total weight for the airframe without battery, but with ESC receiver and servos was a little over 26 ounces. Adding a 6 ounce 2200 mAh LiPo battery brings the weight to 32 ounces, at the lower end of the weight range on the manual cover. By my calculation, the wing loading is about 18 ounces per square foot, and cube loading is over 13 ounces per cubic foot. This wouldn't make the Acro a trainer, but I'm still hoping that it will fly as well as the original purchasers mentioned on the thread in Sailplane talk.

The pictures show the replacement screws in the control horn pivot points for the rudder and elevator. Apparently, the kind of horn used for the rudder was supposed to be used for the elevator also. I could have reamed out the attachment at the rudder horn joint to take the original screw. The holes in the elevator horn were too small and too close together to do that, thus better to use slimmer screws for the pivot. Now the joints don't bind. The last picture shows the hatch area. Sliding the battery under the wing past the ESC and receiver in the hatch area is a bit challenging.
Last edited by DuPageJoe; Nov 18, 2017 at 04:53 PM. Reason: I weighed my Acro Again and it weighed 2 pounds
Nov 09, 2017, 05:31 PM
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Here is a link to my Taranis Q X7 setup for trimming the thrust vector servo and mixing in rudder into CH05 to take advantage of that feature of the Acro.
Nov 18, 2017, 05:23 PM
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I'm finishing off the programming of my Taranis QX7 to suit the Origin Acro, I put in rate switching at 50% (normal) and 75% and 100% (High) for ailerons and rudder on one three way switch, and the same setup for elevator on another switch. I found that I needed to reverse the aileron and elevator servo actions, but the rudder was OK. Normal, low rates give throws of + and - 0.4 inches (10 mm) for the ailerons and elevator, and + and - 0.6 inches (15 mm) for the rudder.

I was able to set the throttle range on the HobbyWing Skywalker 40A ESC to the -100 to +100 range of the output from the Taranis and the Delta 8 receiver it was bound to. I was helped by Miami Mike to see that this was less complicated than trying to match the 0 to 100 range mentioned in the Skywalker's instruction sheet. Other transmitters might use that throttle range convention.

I put in a throttle cut by switch using one of the Taranis' Special Functions to drop throttle to minus 100 output when the switch is set. I also was able to put in a voice warning whenever that switch was changed, also using a Special Function.

Now that everything is set up, just waiting for the weather to clear and warm up a bit.

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