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Old Nov 29, 2004, 07:12 AM
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Ed Couch's Avatar
North Richland Hills, Texas USA
Joined Aug 2000
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Pogo #2, Contra-Rotating Motor

Finally got around to mounting the contra-rotating prop twin ROM motor on the new smaller version of the Convair XF-1 (Pogo). Little bird comes in at about 9 ounces with the new motor less the spinner which is in final work up. Contstruction is 4 mil Depron and carbon with a little 1/64th plywood added as necessary to hold things together. First flight indicate a nice flying aircraft with no real problems. Still working issue of both motors running on two controllers. Running on single controller works but start ups are bumpy with hesitation. Using two Phioenix 10's but programming is not same for both, need additional work on the programming. Props cut down to 7.5 inchs with aft prop being 7.5 by 8 and forward prop being 7.5 by 4.7. Forward prop shaft just extended by 3/4 inch to give more seperation of the blades but runs quite smooth on four bearings through top motors drive shaft. Lower motor mounted directly under top motor inside machined cage. All up motor with props about 48/50 grams. Can build lighter and may do so at later date but still chasing the bugs right now. Bob Wilder constructed the motor for me and did a great job but with everything we are still tinkering with it to get it right. Look forward to getting the spinner mounted and a few more test flights before calling it a success. Ed
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Old Nov 29, 2004, 10:59 AM
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indoorff's Avatar
Ladner
Joined Mar 2004
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Ed,

That is really neat! Where did you get the props? Great job.
I noticed you dont have the convair logo behind the cockpit either. I have not been able to find this anywhere. May try reproducing it from a photograph I have.


Chris
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Last edited by indoorff; Nov 29, 2004 at 11:03 AM.
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Old Nov 29, 2004, 11:30 AM
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North Richland Hills, Texas USA
Joined Aug 2000
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Props are cutdown GWS and MPI props originally 10 inch props. Left hand prop is the MPI and the GWS is the lower Gray colored prop. Again, extended inner shaft about 3/4 inch to give better blade seperation. Convair logo missing cause I forgot to order it when I had the rub on lettering done. Might get around to it at later date. Blades will be repainted when new spinner is mounted and all the bugs worked out as done on the original Pogo. Larger single prop Pogo #1 photos attached. Still flies real nice with brushless setup. Big bird will go straight up from liftoff till tired of watching it and sounds great in flight.

ed
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Old Nov 29, 2004, 12:25 PM
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'on a mountian in New Hampshire
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Ed you magnificent, pagen god!
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Old Nov 29, 2004, 07:02 PM
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North Richland Hills, Texas USA
Joined Aug 2000
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Only mortal, but have a bunch of crazy friends with many varied skills who help each other many times over. Also worshipped the Tron (Radio Control) and Hung (Free Flight) gods for many years.
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Old Nov 29, 2004, 10:50 PM
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United States, TX, Fort Worth
Joined Jun 2000
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Quote:
Originally Posted by indoorff
Ed,

That is really neat! Where did you get the props? Great job.
I noticed you dont have the convair logo behind the cockpit either. I have not been able to find this anywhere. May try reproducing it from a photograph I have.


Chris
That Convair logo is on the plastic kit decal sheet on that euro 1/72 scale Pogo Kit. Ed, I will try to scan my copy from my kit and mail it out to you and anyone else that might need it..
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Old Nov 29, 2004, 11:52 PM
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Where did you get the reverse prop?
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Old Nov 30, 2004, 10:16 AM
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North Richland Hills, Texas USA
Joined Aug 2000
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I got them in a matched set from LHS. Manufacturer would seem to be MPI the props are 10 by 4.7 cut down to 7.5 inchs for the Pogo. On contra-rotating props the lower prop is normally of greater pitch due to the pre acceleration of the air from the #1 prop and being that the standard or right hand prop (from crewstation) I used a cut down GWS 10/8 prop and it would seem to work quite well at this point in time. Always subject to change as the flight test phase (especially while hovering) is just starting to get underway. Only two flights at this stage.

It took me six months to get the Wright Flyer working correctly and near that to get the first Pogo working correctly so I'm in no hurry at this time. Always work way through one problem at a time (learned the hard way) never change two things at a time, just doesn't work. The addition of the two piece spinner will require possible prop changes as well. Number 2 motor always runs warmer than number 1 motor as thats a given and it will take time to prove out. Only require 100 percent power for short time (assent/recovery) so heating should not be problem. Should not, where have I heard that before and presume nothing. New birds are always fun to debug but the results are well worth the effort.

New subject, have been doing test flights with variable pitch prop similar to collective on helicopter. Test vehicle is basically a clipped wing Lite Stick but working on a little JAR for further testing. Vehicle is a hoot to yank the throttle/prop "aft of the notch" and watch it completely stop in midair or go full throttle with max pitch and then pull the throttle past the gate and try to recovery from 15 foot. Wonder what it will do if I have the altitude and go nose down vertical and pull full reverse? Again, Mr Bob built the unit after seeing something at a recent event go to the ceiling full bore and yank reverse just prior to impact and it stop. Interesting concept to be sure. Its a hoot to land and pull reverse and scoot across floor, totally insane! ed
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Old Nov 30, 2004, 11:05 AM
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Seattle
Joined Dec 2001
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Great accomplishment! I've been playing with the idea of a counter rotating system for a few months and here it is. I hope someone takes the idea to the production stage. In principle counter rotating props are more efficient than one so you should see lower power need /longer flights.
The variable pitch prop also sounds interesting. Lots of room for ideas on how to set up a plane, variable pitch-variable rpm, constant speed-variable power input ..
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