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Building Tips and technical articles. => Building techniques => Topic started by: Rob Killick on April 22, 2007, 08:17:30 PM
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Hi ,
Back again ;D
I'm going to use the kit stock push rod wire on my latest project .
What I'd like to know ,is how to solder the "keepers" (washers) without damaging the nylon bellcrank ?
What do the rest of you use for a soldering tool (iron , gun or micro torch) ?
As always ...
Thanks :)
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Hi Rob,
It's my understanding that a lot of people use wheel collars that fit the wire and J.B. Weld them in place. (not the quick set J.B. Weld, but the original)
Bill <><
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While it's possible to solder the washer when using a nylon B/C, it's not an easy thing to do. My solution is to use fine sandpaper to get everything nice and bright, and grind a thin slot 1/3 of the way through the wire about 1.8" above the B/C. Then I put on a plain brass washer and then crimp another brass washer into the slot. Then a careful application of JB Weld makes everything pretty darn solid and secure.
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Rob: If you decide to solder, put a pice of sandpaper with the appropriate size hole between the washer and the bell crank. I also cut a slit in the paper from the hole to the outside edge so I can just pull it out when finished.
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Rob: I use either one of these, the gun puts out some serious heat instantly.
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I think a MUCH better (safer) solution than JB weld is the use of a flat slotted rod with a wheel collar and permanent loctite on the set screw. (or solder the screw into the collar.
The problem with JB weld in this app is that it depends on the bond to the (small) area of the wire above the washer.
JB weld rod ends like this HAVE failed and will fail again. Just a matter of time.
Permanent (red) and removeable (blue) loctite should be a part of every plane assemblers tool kit.
JMHO
Curt
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Hi Curt,
I agree that the end of the pushrod needs to have a "flat" filed/ground on it where the set screw engages. I believe that the way Tom Morris and Tom Dixon do it is fairly safe. I would definitely J.B. Weld the collar and set screw in place.
Wouldn't this function as well?
Bill <><
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Some thing else that you might consider when soldering push rods with a coupler between two rods is drill a small hole (.010") in the coupler so that the heat will have a vent and not blow out the solder when soldiering the second spot...
Did I make this as clear as mud ??? H^^ #^ n~
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Rob,
Your concerns are well founded. Soldering on push rods can damage plastic bell cranks and horns. I prefer to use wheel collars and JB Weld epoxy. In the attached photo, even though I did not have any plastic to be concerned with, my preference is still for the wheel collar and JB Weld.
A couple of details: I like to file/grind a GROOVE for the set screw, so that in the very remote chance that it comes loose, it will not be able to slide down the wire. Also, put RED Loctite on the collar set screw. To maximize adherence of the JB Weld, degrease all surfaces that will be epoxied, and also roughen all surfaces with coarse sandpaper to provide a better surface for the epoxy to grip.
Take your time and do a through job here, as the control system is one place when no failures are allowed.
The plane in the photo happens to be a 40 size Time Machine, and the flap horn, with bushing, is from Tom Morris.
Cheers.
Warren Wagner
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Hey Wareen: Is taht the Tom Dixon Time Machine ? If so how about some more pics. Even if it isn't more pics are in order Please.
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Hi Curt,
I agree that the end of the pushrod needs to have a "flat" filed/ground on it where the set screw engages. I believe that the way Tom Morris and Tom Dixon do it is fairly safe. I would definitely J.B. Weld the collar and set screw in place.
Wouldn't this function as well?
Bill <><
Hi Bill.
Not really.
Loctite is designed to hold threaded fasteners in place. JB is not. Epoxy depends almost entirely on a mechanical bond to a surface. If it is shiny and smooth (read wheel collar and piano wire) then it is just a matter of time before it will release.
I'll almost guarantee that if you epoxy a set screww in place with jb, I can unscrew it when cured.
Now, if one is careful, you can apply the epoxy in such a way that it WILL mechanically lock things in place, but by then, you've added the extra weight of the epoxy basicaaly for no reason--Loctite is the proper adhesive.
Nothing more is required.
Curt
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Hi Curt,
I agree that the end of the pushrod needs to have a "flat" filed/ground on it where the set screw engages. I believe that the way Tom Morris and Tom Dixon do it is fairly safe. I would definitely J.B. Weld the collar and set screw in place.
Wouldn't this function as well?
Bill <><
HI Bill
The JB weld is worthless trying to use it on this application, it will crack and fall off. I have seen it fail just TOO many times, same thing with people who JB Weld the bellcrank rod, the brass eyelets will get loose when the JB Weld cracks and the plane is many times crashed
Regards
Randy
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Thanks for the info, Randy! I had not heard of the J.B. Weld cracking, but I can understand that it would.
Bill <><
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I use a copper or brass tube to bush the bellcrank hole into which the push rod goes. Doing this creates a heat barrier between the rod and the plastic due to the small air gap between the push rod and bushing. Taking a damp business card as a spacer between the washer and the bellcrank when soldering the washer on is enough to make to get a good solder joint without damage to the plastic of the bellcrank; Just tear away the business card when done.
Make sure the rod and washer are bright and shiney, scour with sandpaper or steal wool. A itsy bitsy bit of solder paste does not hurt as well.
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I use a piece of the thick paper label that comes with a package of bolts. Just cut a hole in it and slip it over the end of the push rod. Have everything nice and clean. Add a little flux, drop the washer on, and solder away. I've also added a twist of copper wire above the washer to give more solder hold. I use a gun, not a torch. Never had a problem damaging the bellcrank.
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Here's my fifty cents worth..............Do it like Curt said to do it. Use Loc-Tite.
If you must solder......get rid of the plastic horn and use a metal one and use good solder like the stuff in the picture below.
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Hey Wareen: Is taht the Tom Dixon Time Machine ? If so how about some more pics. Even if it isn't more pics are in order Please.
Leester,
Yes, that is the Tom Dixon "Time Machine". It's design is influenced by the "Pattern Master", but several design changes have been made to shorten the *time* necessary to build a stunter. It was a fun build, with the "Kept Foam Wing", which builds extremely fast. The flying characteristics are superb!
It's still going strong, so if the GB Weld has cracked and fallen off, the wheel collars are still doing their job.
Cheers.
Warren Wagner
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Frank,
To your reply #15...
After using a flux type, part-silver solder like that, I clean the flux residue off carefully.
Baking soda paste in water, as many times as it takes to kill any foaming from the chemical reaction.
Wipe off with paper towel and plenty of sprayed on water.
Dry the water out with rubbing (isopropyl) alcohol.
'Grease' the working parts. Fairly heavy motor oil or white grease (e.g., Lubriplate). Only a drop or so, worked in, does it.
Wet 3x5 card between the soldered side and the horn or bellcrank keeps a lot of the flux out of the working area, and keeps things cool enough if you work quickly but thoroughly. The wet card tears out nicely after the soldering, and if any crumbs are left in, an edge of the rest of the card can work them out before cleaning.