Arrio's LMH 110 Page

LMH 110

I had the opportunity recently to help a friend with an original design electric helicopter. The design and concept of electric and small helicopters so intrigued me that I just had to have one myself. I recently came across a deal on the internet for a complete LMH outfit with extra new parts for a reasonable price, and decided to buy it. It will be on the way this week. I have read numerous articles on the internet from individuals that made a conversion from gas to electric on this LMH with striking success. Their success has not been lost on me. I hope to attempt the same in the near future. Another thing I wish to try is to put collective pitch on the LMH. There are a couple of drawings that have been floating around on the web for a couple of years now that illustrate how to do this by modifying the original pieces and very little fabrication. I'll post them here soon.

Something I have read that disturbs me, is the recommendation to "add weight" to the aircraft to bring up the rotor rpm. I feel that it would be better to trim the trailing edges of the rotor blades equally until you get the desired Rotor RPM. It may be a bit more work, but it results in a livelier ship and less work for the motor. We will see how my theory works when it comes time for me to adjust the rotor speed on my LMH.

See my LINKS page for other web sites about the LMH.

Some industrious folks have even modified the little LMH for collective pitch. The drawings describing the modifications where posted to the web and the Newsgoups in the form of GIF and JPG files. There are 3 of them. Two of them, GIFs, detail the modification itself and the third, JPG, illustrate a jig fixture to enable one to cut the slot into the main shaft. I don't know who the originator of these files is, or I would give due credit for them.

COLLECT1.GIF Illustrates the the mast and linkages.

COLLECT2.GIF Illustrates the Feathering Plate, Washout, Control Bearing/pitch slider.

SHAFTJIG.JPG Shows how to fabricate a jig fixture for your dremel tool and cutter, to enable you to accurately cut the slot lengthwise along the mainshaft.

Trials of the Electric Conversion

20 April, 00 ...... I built up a 1400ae 8 cell pack and tried it out to see how it performed compared to the 1400ae 7 cell. I got a little more umph and a bit more duration. (technical terms). But not what I was hoping for.

Well, having tried three different motors and a pinion selection from 9 to15T and the pitch range from 4 to 6 degrees, the average duration was around 2 1/2 to 3 min. The best I could achieve is 3 min and 20 sec. in a hover. The motors where the AP29BB, K-Speed Heli, and a Trinity 27x1 Copperhead dyno motor. The AP29BB always got too hot after the run. Couldn't keep my fingers on it for more than a half a second. The Trinity and K-Speed ran much cooler. you could hold it all day. I was having issues with the AP29BB because it is an adjustble timing motor. And not knowing how to determine the correct/best setting for this application, input voltage, load etc., I feel that the little AP29BB may not have delivered its best performance.

The 3 min 20 sec run was with the K-Speed, 14T pinion, and 4 degree pitch. It had real good head speed. I even had to turn the rates down a bit on the gyro. Sounded real good, like a big bee hovering in front of me. I need to get a hotter wind motor, like a 16 or 17 turn. A Cobalt would be nicer, and a Brushless even better. But I don't want to spend that much. (yet)

With the small rotor diameter of the LMH, I think it is very important to shed as much weight from the machine as possible. In most instances, when I finished my hovering flight, there is about another 1+ minutes, almost 2 minutes of power left to scoot around almost touching the ground and bouncing a bit. Just not enough to bring it up into a clear hover. That tells me that I have considerable power left , and that the aircraft needs to be lighter or the system more efficient.

I really like the Pegasus35 Speed Controller from Castle Creations. For the high current it has been taking, it barely gets even warm. After each run/flight I would put my finger against it to see how warm it got. Most cases there was no perceptible difference from before I started. It just would not get hot. It has a very good safety feature also. It won't power the motor until it senses at least 4 seconds of low stick. That way you won't see the heli rocket past your nose when you plug in the battery! :-)

8 March, 00

Here are some pics of my LMH E conversion.

The motor is a Kyosho K Speed Heli motor. It is a regular RC Car size, bushing motor.

I removed the Arlton mechanical gyro. A wheel collar holds the spider and bushing to the pitch rod.

It is difficult to see in this photo, but the pitch (fore & aft) servo has been moved to the rear of the left side former. This was to make additional room for the battery pack to lie on the right side of the crutch, and allow enough reward space for CG adjustments. The tail rotor servo now lives at the back of the chassis below the tail boom.

The battery pack (wrapped in black electrical tape) is on the right front crutch. The Arcamax PI HH gyro is just barely visible in the pic (blue box) behind the right side former next to the main shaft. The small speed controller, from Castle Creations. is the Pegasus 35. Capable of 35 amps continuous, 50 surge. Also with BEC and safety and soft startup.

In this configuration, with a 7 cell pack. 1400AE cells. It weighs at 38 ounces. There is a bit of room to reduce the weight some. About 6 inches of 14 gage wire could be removed and and I could put in an AP299BB. (which a friend graciously allowed me to borrow for evaluating) I am going to add a cell to the 7 cell pack to try as an 8 cell pack. Run time and performance was poor on 7 cells. Also, a contributing factor, was that the motor was new and the brushes not broken in/seated. A current measurement was taken using an Astro Flight Watt meter. The system was pulling 35 amps at full power. Hopefully this will come down with 8 cells verses 7.