button bellcrank??

[Hemi Steve]

Can anyone tell me what a button bellcrank is, how they are designed and what is the advantage in using one? I thought I knew but i'm not so sure anymore.

Steve

[pat king]

I offer a control system kit for my 1/2A Mouse Racer kit. The bellcrank is an Aluminum Perfect/Fox 1/2A 2" bellcrank a pair of #4 Button Head Cap screws and a pair of round head weld nuts. Thee attached file shows what it looks like.

Pat

[Brett Buck]

Can anyone tell me what a button bellcrank is, how they are designed and what is the advantage in using one?

  I am not a speed/racing guy, but I think the advantage is getting rid of draggy connectors and leadouts by attaching the flying lines directly to the bellcrank.

    Brett

[Dave Hull]

Hemi,

I wrote a reply, but StuntHanger ate it when I attached a photo that was too large for it to swallow....


Brett is correct that the purpose of getting the line/plane connection onto the bellcrank is to get rid of some drag. Also, many racers will have the lines coming out of the same hole I the wing, so connectors there would be problematic. Note that this also gets rid of one load-bearing line connection or joint, which if done right can only help the reliability.

There are a number of construction details that result in a practical setup. Rather that recreate my prior (lost) reply, let me know if you need more details.

Note that "buttons" actually may refer to two different kinds of setups. Button bellcranks are different than speed buttons, which are similar to scale racer internal connection buttons....  What Pat has shown are some of the details of a button 'crank, which was your original question, but understanding the others may eliminate the confusion you are having.

The first use of "button" was on the monoline control unit as far as I know. This would be the Victor Stanzel mechanism instead of the Jim Walker (bellcrank) mechanism. On the end of the Stanzel unit is a brass (or steel) part that looks pretty much like an old-fashioned shirt button (loose button, not sewed to the shirt). The control line loops over it and cinches down on it. Still used today in heavier sizes. These same buttons are used on internal 2-line connections on things like AMA Scale Racers and B-TRs where getting at the bellcrank is too much hassle to use a button bellcrank. If you want pics of any of these, send me a PM with a number and I'll text it to you.

Divot McSlow

[Hemi Steve]

Ah ha,, I get it now.  I'm working on a largish (11lb) scale model with plug-in wing panels,  to remove the inboard wing panel I need to be able to disconnect the leadouts from the bellcrank.  further I want to have the leadouts off for static judging.  I will be flying it at the 2020 Nats I have a method that I'm flying with right now but it has been suggested that I might have an issue with the rule that says you can only have 2 connectors per line.  My thinking when I put the system together was that the connector at the bellcrank in in the leadouts , not the control lines.  I don't need to arrive at the Nats and be told my method is disallowed.  It was suggested that a button bellcrank would solve the problem.  Now that I know what it is I guess it could be a solution. 

Any thoughts weather a button design will scale up to a 4" bellcrank"?  Here's a couple pictures of what I'm flying with now.  I've done a 50 lb pull test...need to get a bigger spring scale to get to the proper 55 lb test load.

Steve

[dennis lipsett]

That is a nice looking Miss Los Angeles. I had built a 1/4 scale model from Walt Moucha plans

[pat king]

The button setup puts a torque on the bellcrank. I would consider the RSM 4" carbon fiber bellcrank with the button head cap screws and the weld buttons. I would suggest a test rig to test the assembly outside of an airplane. I would test it at 75 to 80 pounds pull just to feel comfortable at the required 55 pound pull. That way you will not take a chance of a failure during the NATS pull test.

Pat

[phil c]

  I am not a speed/racing guy, but I think the advantage is getting rid of draggy connectors and leadouts by attaching the flying lines directly to the bellcrank.

    Brett

The main advantage is the ease of attaching and removing lines.  Less drag is a help too.  The other benefit is that with a brass button and enough spacing between the button and the bellcrank there is very little wear.  a thirty second of an inch is plenty of space for the line. The only lube might be a tiny bit of grease in the button groove.  With the polyethylene super lines even that isn't needed.

[Hemi Steve]

Motorman
I would want to agree that the wrapped and soldered loop as depicted isn't a connector but it seems like using a connector to connect the leadouts in some opinions constitutes an additional connector in the Lines.  My opinion is that the connector is in the leadout rather than the lines but we all know about opinions.

Dennis
I'm glad you like my Miss LA.  She's also 1/4 scale from my own drawings.  The forward half of the fuselage that would have been aluminum on the prototype is molded fiberglass.  That portion also has rivet detail.  She's got a partial cockpit with a detailed instrument panel.  Motor and battery cooling air goes through the exhaust stacks and an opening under the instrument panel.

I think I have just figured out a solution that completely solves the problem.  I will open up the holes in the adjustable leadout guide slider so that the leadout eyelets can be fed through. The openings in the fuselage sides are already large enough to deal with the arc of the lines as the bellcrank moves through its arc and can clear the eyelets.  For static display I will simply coil the leadouts inside of the fuselage,  The top hatch is very large and I can easily do this.  The leadout guides are already removable for static display.  10 minutes in the milling machine will do it.  I will now be able to permanently connect the leadouts to the bellcrank and do a wrapped termination.

Thanks to everyone who gave this problem some thought and offered their ideas.  This forum is great for this kind of interaction.

Steve

[dave siegler]

combat guys that use external controls often use belcrank buttons.  I use them I run the flying wire or spectra right to the crank,  The loop is only slightly large than the button so the springiness keeps it on the button effectively. 

but for something big like that I would use something that locks


https://stunthanger.com/smf/combat/metal-bellcrank-multi-strand-lead-outs/msg530985/#msg530985