Keith Buckner

I had enough spare parts lying around to build a "midget" Hummingbird, as exhibited on Helihobby's website:
http://www.helihobby.com/html/sub-micro.html

I am waiting on a couple 6G servos, and a DD tail rotor to complete the build.
HH's site indicates it is more stable than the original sized bird.. any opinions or comments?


Has anyone done/flown the conversion?
Any hints, tips, reccomendations, or admonishments?

Thanx in advance,
KB

darkside212

My Feedback: (73)

I to tried this conversion, but it didn't produce enough lift to get it air born. I also tried another helihobby.com mod that didn't work: the swash plate binding stopper. I think I did everything right but I could be wrong. Let me know if it works for you, and good luck!!
PS Have you used the DD on your other hummingbird? I tried the gws 50 xc and it didn't work for me but you can use the piccolo high authority motor if you buy the piccolo spur gear- it fits perfectly and it has so much more power than the stock setup. I can rotate clockwise just as fast as counter clockwise!

coltech

I'm going to try this on my old Dragonfly. Think I'll cut the main blades down in stages after reading your experience!
How did you remove the tail boom to cut it down? It appears to be glued in!
If I get it to fly I'll let you know how it performs and what size I cut the main blades down to.

darkside212

My Feedback: (73)

I just twisted until the glue broke and it came right out. Definetly cut in stages, luckily the blades I cut already had damage to the tips so I wasn't out anything other than some broken blades.
Good luck!

VinceHerman

I am not sure that this is something that can be done in stages. The cut blades produce less lift. So you need a proportionally higher head speed to be able to achieve hover. (it is this higher head speed that provides the greater stability of these conversions). To get that higher head speed, you typically bump up the number of teeth on the pinion gear. I recently began experiemnting with this on my piccolo. I cut 65mm off of each blade, and went from an 8 tooth pinion to a 10 tooth pinion. I have only flowin in in the 2' by 3' uncluttered space in my otherwise cluttered basement, so it is hard to determine the difference in stability. As soon as I get the opportunity, I will fly it in a bigger room and let everyone know how I did. I even have a spare head, so I can swap back and forth, just swapping the head (with flybar and blade set attached) and the pinion, to judge the difference between the two configurations. Cutting the boom and reducing the landing gear size are more cosmetic than aerodynamic.
(and, No, I am not a good enough pilot to fly in 2' by 3', but I am impatient so I was not going to wait)

coltech

[quote]ORIGINAL: VinceHerman

I am not sure that this is something that can be done in stages. The cut blades produce less lift. So you need a proportionally higher head speed to be able to achieve hover. (it is this higher head speed that provides the greater stability of these conversions). Won't changing the head speed by changing the pinion affect the ability of the tail motor i.e. It won't be powerful enough to counter the increased torque from the head and will be difficult to hold steady?

VinceHerman

I really don't think it makes that much difference. Yes, you are turning the head faster, and that would increase the torque. But you are turning smaller main blades, so that would reduce the torque.
Actually now that I think about it, I think that there is almost no change in the resulting torque. I use a non-hh gyro and revo mixing. That means that the transmitter tells the tail how fast to spin to counter the main rotor torque at each main motor throttle setting. I had the revo mix set up for my (nearly) full sized blades and the 8 tooth pinion. When I put on the moth blades and the 10 tooth pinion, I was able to fly without any dramatic rudder input. This indicated to me that the same tail throttle settings were doing the same job. The tail was working no harder after the moth conversion than before.