Hinges, bearings don't turn easily

[Bearhawk535]

i am hoping someone has an easy solution to a problem I am encountering. My welded bearing points have a lot of friction. The aileron/ rudder hinges, control stick pivots, elevator bellcrank, etc have excessive friction that will result on very heavy control resistance unless I find a fix. A little lube made the aileron and rudder almost acceptable but the bellcrank for aileron is crazy tight, as is the control stick pivots.
I hope some one has an easy trick to make these swing freely.

[S Lathrop]

When I weld these hinges, I have a solid bronze or brass insert where the bearing surface is going to be or where I am going to insert a bearing. The bronze keeps the bore round and free of any scaling that will happen when the metal gets really hot.

A fix might be to machine bronze inserts and press them into the bearing bores or where the bearing surface will be. Then use a torch to heat the area to a temperature well below welding but hot enough to expand every thing.

I have found that using bronze or even aluminum inserts almost eliminates any distortion. I used this technique for all my wing steel parts and the control systems. Every thing works smoothly without honing.

I have uses this technique for 30 years building race car suspension components where I have pressed in bearings all all types in thin walled housings where different parts of the component weld to the bearing retainers.. Many with snap ring to retain the bearings.

[mswain]

I slipped a thin washer (an960-416L) between the bearing and AN970 washer on my bellcrank and it significantly reduced friction.

my elevator and rudder hinges I used a brake cylinder hone per Eric Newtons manual to clean up the inside of those hinges after welding.

[Bcone1381]

Smooth surfaces + Good Alignment makes for a smooth and easy control surface movement.

The welding process will deposit slag on the inside of a tube. This requires a builder to use a reamer to clean out the inside of a tube that makes up the bearing surface. It's gonna take some effort with the reamer!,

Afterwards, use an abrasve to polish the inside of the tube smooth. Google Bore Polisher. Guys who like guns use them to clean their barrels I think. You might try a dowel with a slit on the end that allows you to attach Emory cloth to it. Insert the Emory cloth into your tube and spin the dowel with your drill. The mating surface (the OD of the inner hinge tube) would also get polished. I like the idea of the brake hone too.

Regarding the Aileron bell rank, that is a mystery, as I envision it having ball bearings. I hope the washer trick works.

[DRLPatrol]

I just finished my aileron bellcranks and am not happy with them. Turned the large tube on the lathe to the interference fit called out on the plans, but we all know when we weld things they expand then when cool contract more than they expanded. Not sure whether it is that or just the distortion from welding but when I pressed the bearing in they do not turn very easy.

Doug

[Bearhawk535]

The problem is the slag after welding. All of these instances are parts that are welded after assembly with no way to disassemble after welding. I am thinking of rehearing them with torch and working them to slightly stretch the female portion and work the slag and grit out of the joint.

[mswain]

Doug, If I recall I had the same issue. After my precision lathe work efforts (ha) I ended up using a dremel with drum sander to open it up a bit.

[marcusofcotton]

Patient handwork with files, die grinder, sandpaper, etc. is required for such. Where the aileron bearings go, for instance, use a marker to color the mating surface that needs work. Then push the bearing in lightly and then remove it. Scratches in the marker will reveal the high points to work at.

[BTAZ]

When I built my first aileron bell cranks, I machined first and then welded which just didn't work out.

The second set I welded first and then bored for the bearings which worked better and were usable with a bit of hand work but still weren't "perfect" from a machinist's point of view because I didn't take my time to "precisely" locate the second side with reference to the first.

If doing it again,

I would weld first leaving the squarely cut center piece extra long so I would have "undisturbed" tube to work off of for the first side.
Put the undisturbed extra length in a lathe and position so it runs true, then bore for the bearing to lightly press in as well as part off the excess tube to finish off the first side.

For the second side:

Put a piece of scrap aluminum(or whatever is handy) plate in the vise.
Face it off so you know it's square to the quill.
Position the spindle close to the center and lock the X/Y table.
Drill/tap an appropriate size bolt hole to match the center hole of the bearing.
Bolt the bearing to the block using this hole.
Put the piece on the bearing and clamp it down to the block with some shims/clamps.
Then bore/face the second side.

It does require a modicum of basic machining knowledge and tooling.

[Bcone1381]

Batz, give me from feedback regarding cleanup methods on a factory bellcrank. Is the Dremel Tool method the best practice, or would you recommend something else...I am interested in learning what a machinist might think.

[DRLPatrol]

I think I got it. I turned down a piece of aluminum to slight interference to the id of the area between bearings. I laid the bellcrank on the wood stove and held a chunk of ice on the aluminum. when the bellcrank was ~300* I tapped it onto the aluminum up to the outer bearing location with a rubber mallet. When the temps equalized it was tight enough to take lite cuts with a boring bar. Then pried it off, turned it over, and did it again.
I think it is going to be good but I had to order new bearing, the first attempt was so tight I messed them up getting them out.

Doug

[BTAZ]

I guess I would expect a "Factory bell crank" to have been manufactured and finished out ready for use.

But to "adjust" with "old world craftsmanship", a Dremel with a sanding drum would be my weapon of choice.

First, you would need to inspect it to decide what needs "fixing". The bearings need to be parallel to each other and their centers need to be co-linear within perhaps +/-.005" or less or they will bind with the pivot bolt installed and tightened. The bores also need to be correctly machined to fit the OD of the bearings.

From a machinist's point of view, that would all be easily established by proper machining after the welding has been completed.

If the only issue is the counter bore fitting the OD of the bearing due to some localized distortion or welding scale, a bit of careful work with a Dremel with a drum sander should work out the problem. You would need to start here so at least one bearing could be installed.

If welding distortion puts the first two items out of spec, not much "hand work" could be done that wouldn't enlarge the bore to a point where the bearing(s) would be a sloppy fit. You could try putting the first bearing in the bellcrank and then passing a bolt through it. Then slide the second bearing down on the bolt and hold it against the bellcrank. That should give you a feel for where the "adjustment" for co-linearity will need to take place. You should try to make half the adjustment on one bearing counter bore and the other half on the second bore to minimize the resulting oversize of the counter bores.

Careful adjustment in the length of the spacer that goes between the two bearings should keep them parallel once the bolt it tightened down even though the OD of the two bearings might not be "perfectly" contacting the counterbore after installation.

Quite frankly, it is not possible to hold the tolerances needed to consistently put two bearings on a single shaft spaced apart any distance that won't bind if someone machines first and welds later.

As I think more on this, if the bearings fit fine in the bell crank(so the OD of the counter bores is correct) and it is easy to pass the bolt through both of them after they are installed(would mean they are co-linear and parallel), you might want to try to lengthen the center spacer a bit. If it is a little short, then tightening the bolt will definitely bind the bearings as the OD bottoms on the counter bores while the inner races are pulled too close together..

[Bcone1381]

Very Good, BATZ

[Bearhawk535]

This is one of the parts that I am trying to get to turn freely. It is welded as such that it cannot be disassembled after welding to clear scale from the bearing surfaces.

[BTAZ]

Unfortunately, that is a good bit different then my LSA(which uses a pushrod to the elevator instead of cables) so without a look at the plans I don't know if I can offer much help.

I would need to know where it is supposed to pivot on and how the part(s) are made/assembled to offer any insight.

[Bdflies]

I'm thinking that a reamer would clean it up. I learned long ago that reamers are far better, at stuff like this, than running a drill through the bore. Just my thoughts.

Bill

[Bcone1381]

+1 on what Bill Said.

I responded already in post #4. I take it your efforts from post #6 did not work.

I have not experience, so take what information I have with a grain of salt....My kit arrives in about 3 weeks. After that I expect to gain experience. For now its book knowledge. That book knowledge has set the expectation that I will too be cleaning out welding slag from the inside tubes of each hinge. I believe that I am tasked with this clean up from the manufacturing process. So, I have on numerous reamers on my list of tools that I expect I will need.

I have this expectation because of a welding video from TM Technologies that featured a man by the name of Earl Luce. http://luceair.com In the welding Video, Earl is shown cleaning up the inside of rudder hinge tube. Its hinge action acts exactly the same as your elevator bellcrank. I bet the outer tube in your hinge has .028 wall thickness. The rudder tube fit over the hinge tube. The .028 wall thickness of the outer tube gives .007 clearance between the two tubes before any welding took place. But after the welding was done the tubes it was a tight fit due to slag.

Earl is the EAA aircraft fuselage welding expert, right? He welded up that rudder pedal, then fit the pedal over the hinge tube, and it hardly budged a bit. So he takes a reamer and cleans out the inside of the rudder tube with it. It took effort with the reamer too!! Earl really had to put some muscle into it. But he get s the slag out. to a certain degree.

Then Earl cleans up the outside of the hinge tube with emory cloth I guess....i mean he polishes it. Afterwards he fits the two together, and it is still WAY too tight but better.

So I think he added abrasive lapping compound between the two pieces next. https://en.wikipedia.org/wiki/Lapping When Earl adds the abrasive compound he is twisting it back and forth repeatedly....as he does this things slowly start loosening up. All this time he is explaining that this is the normal task that we aircraft builders have to accomplish on every hinge that is welded like this. He probably tests the two pieces a couple of times adding more compound each time until he has effortless hinge action.

Anyway, Earls did not stop until the fit was such that the pedal would twirl around and around with the swing of the parts with little or no resistance.

I would also think that a Bore Polisher would be worth considering, but Earl never used one. http://www.preferredabrasives.com/pr...bore-polisher/ or look at this one. http://slugshooting.accountsupport.c....php?t=10&p=11

I am months behind you. I want to know how this works out. BTW, I happen to know that one person who frequents this site has two of those TM Tech videos. He might be willing to part with one of them. We'll see if he chimes in.

Brooks Cone
Patrol Plans #303
​​​​​​​Patrol Kit on the way.