stunthanger.com
General control line discussion => Open Forum => Topic started by: Dennis Toth on December 16, 2016, 06:12:42 AM
-
Guys,
I am finally back working on my Barnstormer and decided I wanted to do a take-a-part for easy of travel/shipping. The last ship I did as take-a-part was a full stunter. I used Paul Walker's Impact approach and it worked fine. For the Barnstormer I realized there is one issue that the full stunter doesn't have and that is the pushrod hookup. On the full stunter you simply disconnect the pushrod at the flap horn and then from the elevator and your good. For the non flapped Barnstormer I'm wondering if anyone has a creative way to disconnect from the bellcrank?
I have thought about simply using a Z bend but am concerned that it will wear the hole. Another approach is to use a flap type intermediate horn (without the flap bends) to allow ball joint disconnect outside the bellcrank. I also thought about just epoxying a blind nut on the bottom of the bellcrank that would allow bolting a ball joint through, my concern is making sure this is a solid mount. Any other methods?
Best, DennisT
-
Sullivan makes a neat quick disconnect for a 4-40 ball link. http://www3.towerhobbies.com/cgi-bin/wti0001p?&I=LXYCH4&P=7
I have seen them used on a tricycle gear retract setup to allow using 1 servo for all 3 gear, never seen one used on something like C/L pushrods. They are easy to change out if it seemed to be wearing after a while. I'd just use red Loctite and bolt the ball to the bellcrank. Can you lower the wing enough to reach in and manipulate a disconnect like this?
-
another option I have seen, make a 90 bend in your pushrod and fit that through a brass bushing in the horn. then afix a 1/16 piano wire "whisker" on the pushrod that runs parallel with the pushrod but overlaps the end where its bent and fit through the hole. This whisker will retain the pushrod end in the bushing and is easily flexed out of the way enough to remove the pushrod from the bushing with no tools.
Also,make sure the bend faces out so that the pushrod in flight naturally is drawn into the horn in flight.
-
If you don't mind the pushrod hanging out the wing, then what Mark said, or a ball link at the elevator horn. For that matter, your flap-like idler thingie isn't a bad idea -- I'd consider putting it on the fuselage so that the pushrod isn't flapping around when you take it apart.
If you don't mind peering into little holes with a flashlight and cursing, put a threaded end on the pushrod and a ball link on the bellcrank, Then screw the pushrod in on assembly, and unscrew it on disassembly. This is how I put my profiles together, so that I can paint without having to work around a pushrod. Getting it reassembled repeatably will be a pain, though, unless you solder a jam nut onto the pushrod end or something.
Alternately, break the pushrod at around the TE of the wing, and put 4-40 couplers on the open ends. Then get a small-diameter steel 4-40 coupler from an electronics supply place (like DigiKey -- the amateur places will all have big aluminum ones) -- if the ends are screwed in tight, then you should have a strong, rigid, repeatable assembly.
-
I'd put a faux flap horn on the wing TE. Or, I'd make the canopy removable and remove the ball link rod end from the BC.
On the Barnstormer, it'd be easy enough to make a tank access hatch extend to the rear of the canopy. Remember that the "drop-out" wing is a stressed part of the fuselage while it's assembled...so should this long hatch be a stressed member...maybe 6 ea. 2-56 screws, from front to rear, three on each edge. Maybe more...not less. Howard will want to see the ciphering. VD~ Steve
-
Geez, this is a little more complicated then is seemed at first glance. If I build in a large access hatch in the center (which the Barnstormer originally has because there is no sheeting aft of the first spar) I could have access to the top and bottom of the bellcrank and just bolt through a ball joint connector. Another idea is to just have a heavy wirer go 90deg into the bellcrank with the end having small eyelets soldered to hold it in place. The bend would be above the top of the wing and allow the pushrod to simply be swung over the wing during shipping. With this one I'm thinking you would have to brace the 90deg to prevent flexing but I think this type of bracing has been done (I think Jack Sheeks used it on his high tail twin boom ships)
I guess another approach is to use a thicker bellcrank and put one of the brass threaded inserts in and bolt to that. I don't really like not having something with a nut or solder on the bottom.
Best, DennisT