shd3920

What connectors are good for attaching cable pushrods to micro servos of a 1/2A scale airplane?
Ordinary pushrod connectors are too big for the small holes of the servo arms and the micro connectors are too small for the cable. Which should I do: 1)drill the servo arm holes bigger and use the ordinary sized connectors which may look alittle ridiculous OR 2)look for a thinner cable at a hardware store and use the micro connectors with the chance the thinner cable may be too flexible and not control well enough.

By the way, the cable pushrods will be used for the elevator and rudder as well as the throttle. The plane is a electric J3 schoolhouse Cub.

Thank you

BMatthews

There really isn't much out there. We small model guys have to improvise. If I was doing a cable control for a small model first off I'd be using the small wire cable and tube stuff. To connect it so that I could adjust things I'd probably use a short bit of music wire with a Z bend in one end and use a 1/16 or 3/32 wheel collar to clamp the Z bend stub and the cable together. At the other end I'd attach an L stub to the cable using a short length of small brass tubing crimped to each and possibly soldered. For a retainer I've been grinding a little dish out of the tip of the L wire and then crimping on a 1/16 length of aluminium tubing. This works great as a retainer but can be easily removed with a light twist from some small needlenose pliers. Just bring along a few extra crimps with you.

shd3920

Absolutely brilliant . . . I will try that, thank you so much. For a retainer for the L-end that connects to the control horn how bout one of the little black plastic retainers used for pushrod connectors? With a dab of epoxy if needed.

Thank you again, I never would have thought of doing it that way.

Bipe Flyer

What cable are you using? I use thin music wire and put a Z bend on each end and a V bend near one end for adjustment. The catch is that you have to put the horn onto the Z bend first, then attach the horn to the plane.

unclecrash

Thats how I do my micro planes BF it works great and light setup. Also some times use the dubro micro connector at one end. With a 90degree bend on the wire. Or sometimes I drill out the servo horn and use the little steel keeper witha set screw that the wire slides through and you can use this for the adjustment end. Dubro sells a kit it has the micro control horn the wire a sleeve for wire and I dont remember it might have the little keeper that goes on the servo horn. Here is a link to them

http://www2.towerhobbies.com/cgi-bin...?&I=LXDCT7&P=M

Bipe Flyer

Those are the ones that I use. I use the keepers on the throttle, but I prefer the Z bend for control surfaces - just in case...

BMatthews

The little black button things that usually snaps onto the pin of the Dubro style connectors? For the wire size I use on the 1/2 A stuff that button is way too large. Trust me, it's far easier to just use the little collar of aluminium tubing.

Here's a pic of the back end of my latest model. BF will recognise it. And no that's not a Godzilla thumb next to it. Just a normal sized one. So you can see that this method works for smaller models.

Oh, and on this particular tiny model I used paper clip wire straightened out for the ends. That's why the aluminium is so large since the paper clip wire is a touch larger than 1/32 so I had to use 1/16 ID tubing. If I had stuck with 1/32 music wire and used 1/32 ID tubing it would be neater looking.

Remember that the key to this is to grind or file a little hollow into the wire. On the really small stuff like this make it about 1/2 the thickness. On the larger sizes about 1/64 deep is fine.

Bipe Flyer

You're right, I do recognize that thumb.

I think that tigerdude426 was referring to the clips that come with the Du-Bro micro pushrod system. They're pretty nice, but only come 2 to a package with enough wire to do 4 models.

BMatthews

Well, he mentione epoxy so I wasn't sure.

THose are nice. What size wire are they for?

shd3920

My mistake, the Cub is the one I completed. This setup is for the Pitts Special 1/2A I am completing.

__________________________________________________ ___________________

I was going to use 1/16� diameter gold cable I have on hand with a short bit of 1/16� music wire with a Z-bend clamped together with a wheel collar for the servo ends. Then I was going to attach an L stub to the cable using a short length of small brass tubing crimped to hold the two together, and hold the L-bend into the horn with a black retainer (the black retainers shown in photo 1)

If that can not be done I was going to instead attach a straight piece of music wire to the cable with the brass tubing, then pass the music wire through a Kavan pushrod threaded connector (photo 2). Bending the music wire at the end to keep it in place in the connector, then attaching the Kavan connector onto the horn (the connector has a threaded end instead of the traditional black push retainer)

A third choice would be: I have a bunch of adjustable clevis clamps on hand (photo 3) but I think they would be too bulky on a 1/2A scale.

What do you think of my ideas?

ANOTHER question: Can I replace the micro servo arms with standard servo arms to better accommodate the 1/16" wire and cable?

I would really like to use what I already have on hand as money is super tight right now.

Bipe Flyer

They're for .030" wire. See the link unclecrash posted above.

Bipe Flyer

tigerdude426,

I prefer as few connectors as possible to minimize the chance of one coming loose. I don't care much for the stranded flex cable because it is heavy and requires ends to be attached. I prefer a straight piece of thin music wire, which will flex around gentle curves, however, if that's all you have to work with, then go ahead and use it - I'd probably use the adjustable clevis clamps you have in picture 3.

Have you considered using a pull-pull setup? It can be done with fishing line and is smooth, light and strong.

If the horns fit the servos, then there's no reason not to use them.

shd3920

I guess I have two choices of what I will do
1)This is my first choice: Is use the 1/16� diameter gold cable (that's all I have for cable) with a short bit of 1/16� music wire with a Z-bend clamped together with a wheel collar for the servo ends. Then I will attach a Z-bend stub to the cable at the horn end using a short length of small brass tubing crimped to hold the two together. That way the Z-bend at the horn end will slip right into the horn and the adjusting will be done at the servo end with the wheel collar. OR . . .

2)Instead of the cable I do have some nylon pushrod tubing and use regular nylon clevises and threaded studs.

As I said I would really prefer to use the cable as it flexes more and I believe will be smoother and neater, but I will play around with both ideas and choose the best route to go (although I really love the adjustable wheel collar, I have that hookup in my electric cub and I think it can be done with the Pitts)

Thank you all for your ideas.

BMatthews

The 1/16 cable is definetly on the large side for 1/2A. And while I may be nitpicking a bit it's not the lightest stuff around by a long shot.

The smaller servos will need smaller wire for the arms. I don't know of any micro servos that won't need to be driffed to take 1/16 wire. Try smaller sizes like .045 or 1/32.

shd3920

OK will look around for what I got. As I do want to keep it as light as possible but yet don't wanna spend any more money if I really don't need to. I will probably go with the nylon pushrods then to keep it lighter.

EDIT: Did someone say I can use just plain 1/16 wire instead of the cable?

Thank you.

Bipe Flyer

You can use 1/32 wire and it's less than a dollar. Make sure that it is supported so that it can't flex when pushing. If it is too thin for the holes on the elevator and rudder horns, drill a new hole that fits the wire.

combatpigg

My Feedback: (3)

A 3 foot length of .055" music wire costs $1 and will give more positive control in both pull and push mode than a stranded cable. Always test your final set up in push mode with reasonable hand pressure against the flap, it is always best to find out if the installation is stout enough before the first flight. .055" music wire should be supported every 6 inches or so and if you poke it out through the fuselage with a fairly tight fitting hole, that counts as a support. To make exact fitting holes for this diameter wire, cut a short length of it off and use it for a tool to drill the control horn and servo arm. You can also sharpen the wire to a point, heat it and melt through the attachment points.

rrragmanliam

My Feedback: (1)

TD,

You can also z bend the cable, I've done it for throttle applications but I don't think it's your best solution here. Bend the cable with about an extra 1/4 " hanging off the end, then once the bend is made harden it by appling solder to the the bend. You can then neaten up the bend and trim the end. The solder hardens the cable, holds the bend and prevents the cable from freying. It sounds a little strange but it works.

Darren

shd3920

This is what I did, with the rudder control:

I used a thin music wire (don't know if it's .055" or 1/32) for the application. I did a Z-bend at both ends, with the horn end simply passing through the horn (see photo 2), and the servo end attached with a wheel-collar to a shorter piece of music wire that has the Z-bend (see photo 1). The other pics are where I am at with my Pitts 1/2A scale. Alot of sanding yet to do, the tailwheel assembly and the leading edge of the bottom wing is not rounded yet. Then I can start covering it finally. The blue pushrod tube was already glued in so I had to use it, supports the music wire real well.

Can not do the elevator, I did not have enough music wire. And I only had one wheel-collar the proper size.

combatpigg

My Feedback: (3)

TD426, plane is coming along nicely! Test your rudder hookup by pressing against the linkage, if there is any give the plane will fly like a fish swims. A pivot point that is 3/4-7/8" up on the control horn will also give the system good leverage and stability. 1/32" wire is about .034" which is as small as I've ever used on a 1/2A plane, it needs a lot of supports. The one method for making control linkage that I've never tried is using hard balsa sticks with wire ends attached....there are those who swear by this method, even on .40 sized models [it is totally old school ].