Hey everyone, Here is something cool that I have been working on that I think you may enjoy.
Variable pitch prop
So, I had been pondering how to make an inexpensive variable prop. I was thinking about using a heli head from a hk450 or perhaps a tail rotor. I eventually saw a post here, on diydrones, where a guy was using a tail rotor from a HK500 (can't find post). I got inspired and found a HK600 tail rotor has the same shaft diameter as the turnigy G10 I use on the techpod. this is what I have come up with.
20130617_183533 
I measured 15 degree max forward pitch and 12 degree reverse pitch. at 15 degrees forward pitch it drew 40 amps from a 3 cell lipo and puts out just under 5 lbs thrust.
I got the blades here and the tail rotor assembly here. I removed one side of the tail rotor plates and replaced both the shaft in the tail rotor and the shaft in the motor with one long 5 mm shaft. I had to notch it a few times for the set screws.I then made a plate to help support the rotor plate so I could then brace it with some 4-40 all thread rod and nyloc nutsI also made a custom motor mount for the techpod.
After the motor was secured, I cut out a mount for the pitch servo. Then I cut a hole in the foam so I could attach the servo mount to the techpods rear fuselage brace. I grabbed a bell crank from the local hobby shop and mounted it to the rear brace as well.
I have the techpod mostly assembled and should have the batteries for it later today. I hope to be able to start test flying over the weekend. If everything works out well, I plane on offering this as an mod kit for the techpod.

Check out this and the latest techpod news at Hobbyuav.com

Views: 3639

Comment by Rob_Lefebvre on July 3, 2013 at 5:50am

Interesting development.  What do you hope to gain from this vs. simply using FP props?  I think you may find these are less efficient, but I'd like to see what your testing shows.

Comment by Joshua Ott on July 3, 2013 at 6:50am
Throw it into beta for a short field landing?
Comment by eduardo on July 3, 2013 at 10:25am

I think reversible ESC is much more reliable.

Comment by Greg O on July 3, 2013 at 1:57pm

MORE blades... :-D It would add so much weight/complexity that the gains wouldn't be much, but the wow factor.. 

6 Blade Tail rotor - cnchelicopter.com

I'm curious if this could be used like a folding propeller, and reduce the drag when motor is not needed??

Looks cool..

Also like Josh said, slowing is down to make a short landing would be pretty sweet too..


100KM
Comment by crystal garris on July 3, 2013 at 2:45pm
The blades I have on it now are just for experimenting. I would like to find or make an APC type blade.

No the blades dont feather. They dont go to 90 degrees. I would also like to see a hollow shaft set up.that would be much more compact.

Being able to tune the pitch mid flight for climbing or cruise could lead to better efficiency.
Comment by b nevins on July 3, 2013 at 7:40pm

Maybe a curved blade like from a fixed pitch helicopter or some blades from a folding type prop could be adapted.
I honestly wouldn't expect any benefit on a plane this small/slow though.

The other issue is electric motors don't really have the power curve to benefit from a variable pitch prop.  You can have a bigger prop for more static thrust, and the load will decrease in flight.

The ability to feather them would be neat to reduce drag though.


Moderator
Comment by Brian on July 3, 2013 at 10:10pm

Wayne, I love the Techpod, wish I could buy another plane right now... (if I did the wife would...)

I wonder how it would compare numbers to say this one: http://www.hobby-lobby.com/evp_pro.htm


100KM
Comment by crystal garris on July 3, 2013 at 10:29pm
I did have a look at all the available v-props. I couldn't find any over 10 inches. Also I don't like to be limited to one particular motor. I am looking for some hollow shaft material I think the through the shaft approach would be simplest.
Comment by Andrew Rabbitt on July 4, 2013 at 3:07am

FWIW, I have replaced the shaft on one motor with carbon fibre tube.  Worked out fine for what I was doing.

Comment by Björn Geir Leifsson on July 4, 2013 at 4:21am

What is the problem you want to solve with this solution?

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