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slop between clevis and control horn

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Old 02-28-2006, 07:30 AM
  #1  
Gringo Flyer
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Default slop between clevis and control horn

I have dubro control horns http://www2.towerhobbies.com/cgi-bin...?&I=LXD932&P=7
installed with GP 2-56 clevises http://www2.towerhobbies.com/cgi-bin...&I=LXK077&P=ML and there is a great deal of play between them. With this plane I took a lot of care in getting my setup right and slop free. Then when I install these control horns with the clevises there is a ton of slop... any ideas?

I tried a 4-40 steel clevis and there is still a bunch of slop. Also I used GP control horns http://www2.towerhobbies.com/cgi-bin...?&I=LXD932&P=7 on the other surfaces with the same clevises and they fit perfect.

Of course the easy solution would be to change the control horns but I am about 800 miles from the closest hobby store so I need something of a home solution.
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Old 02-28-2006, 09:16 AM
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da Rock
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Default RE: slop between clevis and control horn

I would suggest first that you use Tower Hobbies PARTS EXPRESS service. It's cheap and fast. I usually get those orders about two days after the call. The deal is basically for the small stuff. They cut the shipping cost and seem to ship it about as fast as they get the order. And since I save sales tax, and their prices on the small stuff beats the LHS, and the LHS usually doesn't have a real wide range of that smaller stuff, and it costs me about $2.50 to drive there and back...... whatever.......
EDIT: Oh jeez, I just noticed you are in Argentina..... so Tower isn't just a phonecall and 3 days away..... oh well....... the rest still applies
If you have some smaller brass tubing, you could bush the rod/horn. Back when I was heavy into Precision Aerobatics, I used to bush the pushrod connections as standard practice. That way, there would be zero slop and infinite durability. The K&S tubing sizes overlap almost exactly. There is one size that'll fit over the rod, and another that'll fit over that one.

You can also probably get away with just placing something over the connector pin if you can find something small enough.

The tube doesn't have to fit the pin perfectly. If it'll go over it, then epoxy it over the pin. The epoxy will solve the slop problem of the tube to pin fit. The tube will probably be oversize to the hole in the horn now. (Nothing ever fits like you want.) So carefully drill out the hole in the horn to fit the tube. You'll have better wear with a larger hole anyway. Do the drilling with the bit and your fingers and you'll have excellent control of the process. If you try to drill the hole holding a dremel in your hand, the horn will most probably be wrecked.
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Old 02-28-2006, 09:26 AM
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Default RE: slop between clevis and control horn

BTW, there is nothing in the "rules of building" that says you gotta use the horns that're available.

Make your own with some plywood. It's dead simple. All you need is a drill bit that's the size of your connector pin.

The way you make the plywood wear proof is simple. After you've got the shape worked out and the placement of your connector holes, drill the holes with a very slightly oversize drill bit. Then coat the area around the holes with slow cure epoxy. Make sure you almost fill the holes. The epoxy will penetrate the plywood great. After that's cured, drill where the epoxy has filled the holes. That'll be easier since the epoxy will sort of dimple into the holes anyway.

Now you've got holes that are surfaced inside with epoxy. The epoxy will wear forever against the smooth surface of the pin. And you can cut your homemade horns to whatever shape you wish. And the plywood can be put into the aileron quite elegantly. Just slot the aileron the width of the ply and epoxy the ply into the slot. The design is lots more clean and elegant than those clunky plastic horns with their pluggy looking backers. And you won't have the soft plastic horn being held to a monokote surface by just two tiny little bolts and some compression. And since so many guys leave those two tiny screws sticking out, you won't have that either.

Making your own horns gives you a higher quality result anyway. Hey, we're modelers, we can make anything, right? and better, right?
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Old 02-28-2006, 10:03 AM
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Default RE: slop between clevis and control horn

I think on the next project I will definetly go the custom made control route but its a little late on this one.
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Old 02-28-2006, 10:37 AM
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Default RE: slop between clevis and control horn

Gringo, An easy fix would be to fill the holes with epoxy, then re-drill.
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Old 03-02-2006, 11:39 PM
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Default RE: slop between clevis and control horn

You will probably laugh at this, but for a temporary fix, this really works. Put a drop or two of medium CA on the pin, leave it connected and let it dry without moving it. When it is dry, break it free and you will have zero play. This will only last maybe a dozen flights before the vibration and such wears it back down. It's easy to clean the CA off with an Exacto blade for putting on your permanent solution later. It's a quick and easy way to get zero play to get you flying until you can apply the more permanent and excellent suggestions the others posted. Don't tell me, your laffing your ***** off, right?. Try it once and you'll see how well it really works, but for a temporary fix only.

p.s. The CA sticks to the metal pin and not the nylon horn. This makes it easy to chip off with the exacto blade.
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Old 03-03-2006, 02:21 AM
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Default RE: slop between clevis and control horn

Fill the hole in plastic with some baking soda, a drop of CA on both sides, .......... cure time .... redrill with proper sized bit. The CA sure seems to stick to the plastic nozzles of bottle and the bicarbonate of soda makes a hard filler. Took a closer look at part and believe Post #6 would be better.

I can identify with the need to have home fixes. Also have a some of those horns GP brand and they have tight fit to all clevis in inventory . Had to order just to get an up close look.
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Old 03-03-2006, 02:39 AM
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Default RE: slop between clevis and control horn


ORIGINAL: mikenlapaz

The CA sure seems to stick to the plastic nozzles of bottle...
I guess it depends on the type of plastic. It seems to just flake off the nylon horn. When I pull the clevis off after I do the CA thing, it all is pretty much stuck to the metal pin. Of course, the cured CA can pop off clean from the bottle with a screwdriver tip or pliers, but once the plastic gets roughed up, then it doesn't like to come off. I like the baking soda idea for a more permanent fix. I bet roughing the surface up would make it even better maybe.
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Old 03-03-2006, 04:18 AM
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Default RE: slop between clevis and control horn

I was thinking more permenant with this use of the combination. The control horns I got are a good example of poor design and or quality control. But it got bucks out of my pocket, but only once.
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Old 03-03-2006, 08:07 AM
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Default RE: slop between clevis and control horn

I agree its poor design. It seems more logical to start with the smallest possible hole that could be needed and allow the user to drill them out. Thats the logic behind all the props we buy, they always have to be reamed out.

I would guess that the vast majority of us are using 2-56 and 4-40 sized hardware on most of our stuff and these control horns are sloppy with both.

I guess the lesson learned is to buy the Great Planes version rather than the Dubro

Thanks for the advise guys. I agree the CA seems strange but it would have been an easy fix at the field.
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Old 03-03-2006, 01:11 PM
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Default RE: slop between clevis and control horn

If you wanted to drill out larger for a 2-56 ball link: http://www2.towerhobbies.com/cgi-bin...?&I=LXD912&P=0
It would put the load force off to side, but the slop should disappear.
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Old 03-04-2006, 03:20 PM
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Default RE: slop between clevis and control horn

I am using ball links on the servo side. I considered putting ball links on both sides but I wonder if there might be some problems with it trying to twist the control horn bc it is pushing off center.
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Old 03-04-2006, 03:34 PM
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Default RE: slop between clevis and control horn

In my experience, ball links coming off the side of anything plastic always end up twisting under load. I have been using Sullivan metal horns when I use a ball link on them. But I still see a very small amount of twist even in those under load. It really needs to be thick metal to stop that. I'm sure a metal servo arm would keep it from twisting. They are usually quite thick.
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Old 03-04-2006, 07:59 PM
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Default RE: slop between clevis and control horn

Not very much nylon bewteen linkage hole and the vertical bolt. You did not mention the size plane and surface area you have them mounted on. Suspect on a small control area it might just try to rotate the nylon on the bolt. Nylock nuts next to nylon would stop any rotation. You probably need more tail weight anyway.
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Old 03-05-2006, 12:50 AM
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Default RE: slop between clevis and control horn

I'm sorry. You lost me on that, or were you replying to Gringo. Anyway, I have my metal horns mounted on my FuntanaS 90 and Big Stik 60. I usually use good clevises at the servo arm such as the Dubro Safety Lock Kwik Link. Ironically, in my case, I prefer the nylon servo arm to flex a little to accomdate any slight skewing of the rod from the arc of the control horn. I Gringo was talking about the servo arm twisting under load if he used a ball link on it since the force applied will be offset and not in the plane of the servo arm. And it will twist if it's a typical nylon arm. A metal arm will probably eliminate any twisting. Also, if I read you right, a ball link shouldn't be tight enough to rotate the ball stud in the first place. They are usually quite free.
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Old 03-05-2006, 01:37 AM
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Default RE: slop between clevis and control horn

I am using ball links on the servo side. I considered putting ball links on both sides but I wonder if there might be some problems with it trying to twist the control horn bc it is pushing off center.
Not very much nylon bewteen linkage hole and the vertical bolt. You did not mention the size plane and surface area you have them mounted on. Suspect on a small control area it might just try to rotate the nylon on the bolt. Nylock nuts next to nylon would stop any rotation.
ArCeeFlyer: A look at the picture http://www2.towerhobbies.com/cgi-bin...?&I=LXD932&P=7 should help clarify my statement.

The alignment to the servo arm would be handled by ball link.
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Old 03-05-2006, 04:21 AM
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Default RE: slop between clevis and control horn

Oh geez. I see. I missed clicking on the first link (no pun intended) in the first post. I was thinking standard type horns. Yes, a ball link on those stud type horns would be making it double jointed and you definitely would want to lock the adjustable horn in place, like you said, with a nut so only the ball link will do work, actually so it will work period. That would be like driving a car with half a steering wheel of slop in it. Could be exciting though. Funny how one little misplaced concept makes one wonder what the heck I'm talking about. lol I get to skimming these posts and miss the main point sometimes.
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Old 03-05-2006, 08:53 AM
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Default RE: slop between clevis and control horn

And adding another nut to those control horns is just getting to be a little much for me. The whole idea is simplicty and effectiveness.

I have metal control horns on all surfaces with ball links at the servo end. I have standard clevises on all the control arms.

To me a ball link on both ends is uneccesary bc at the control surface end the clevis only needs to rotate one direction. If properly setup there would be no reason for vertical mobility on a clevis. On the servo end you would need both horizontal and vertical mobility to account for the arc of the servo arm and for the up and down movement of the control surface. At least this is how it looks to me

BTW this is the setup on a CA Models Epsilon 90. With the above mentioned setup all linkages are smooth and without slack minus the dubro control horns. I filled them with epoxy and we will see how it holds up.
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