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Weldment lubrication

wirejock

wirejock

Well Known Member
This applies to several models.
The weldments like the rudder pedals and the flap weldment have bearing surfaces against the plastic mount. Delrin I think. Some are black, some are white. Is there a difference? My question is should they be installed dry or is there a lubricant appropriate to this application? I don't want anything attracting debris and causing problems.

Edit...
I didn't consider the steel might need something to prevent rust. Any thoughts apprectiated.
 
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Nothing needed.....

See post 12.....


Installed properly with the correct shims it will never need any lubrication.

After splitting the blocks, I used a spade bit to rebore to size, eliminating the spacer shim. Sand to a smooth movement.
 
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Lube on Delrin blocks

While deploying the flaps on my 7A, I'd often hear a 'crunch' when I first hit the flap switch. After removing the L/R panels on either end of the flap weldment, I witnessed a momentary torquing of the delrin blocks. Clearly, the weldment inserts into the blocks were binding on initial deployment. Recently, I removed the two bolts securing each of the blocks and spread the blocks enough to spray silicone into the inserts. Problem solved.

Jim Diehl 7A
Lock Haven, Pa
 
Try Boelube

I like to use Boelube for things like this, and screws, and hinge pins, and yada, yada, yada...

Don
 
A little light grease is always a good idea when you have a bearing like structure (rudder and flap brackets, bell crank bearings, etc.). This is also important for any metal to metal connection that you would want to disassemble at some point. The best example is bolting the gear legs into their weldments. Another area is the wing spar mating surface.

When Van's came out with the SB on nose gears, I lifted the plane up, took the nose gear bolt out and slide the gear leg out of the weldment. I heard of other grabbing a torch to loosen the rust.

I use a simple automotive white grease.

Carl
 
Carl Froehlich said:
A little light grease is always a good idea when you have a bearing like structure (rudder and flap brackets, bell crank bearings, etc.). This is also important for any metal to metal connection that you would want to disassemble at some point. The best example is bolting the gear legs into their weldments. Another area is the wing spar mating surface.

When Van's came out with the SB on nose gears, I lifted the plane up, took the nose gear bolt out and slide the gear leg out of the weldment. I heard of other grabbing a torch to loosen the rust.

I use a simple automotive white grease.

Carl
Click to expand...

That is not always the case. Grease/oil in a joint like the nose gear leg/socket can actually allow slight movement over time, leading to wear - heck that is what grease is for... :)

The Grummans use a similar arrangement for their nose gear leg and the approved assembly technique is to install with wet zinc chromate primer.

Keep the grease to joints that you want to move/slide/rotate.
 
az_gila said:
That is not always the case. Grease/oil in a joint like the nose gear leg/socket can actually allow slight movement over time, leading to wear - heck that is what grease is for... :)

The Grummans use a similar arrangement for their nose gear leg and the approved assembly technique is to install with wet zinc chromate primer.

Keep the grease to joints that you want to move/slide/rotate.
Click to expand...

Generalizing can be dangerous.....

I think the Grumman leg is constant diam.?

The RV-legs are not. There is a narrow contact point where it exits the socket, and a knob portion at the upper end where the bolt is. The rest of the leg portion that is within the socket is reduced in diam, and a small (very small) amount of deflection in this area is expected under load.

So, for rust protection, and to prevent wear, the plans recommendation is for grease at these locations.
 
All my Deleon blocks that supported torque tubes needed a little fine tuning with fine grit sandpaper to loosen up the friction a bit. I lubed mine with a little grease during final assembly.
 
For joints that rotate, like the flap and rudder torque tube blocks, I pre coat the bare steel with dry film graphite from a spray can. Several coats on the steel will provide corrosion protection, is dry so doesn't attract dirt and provides lubrication. I bake it on with a heat gun and it forms a hard coating with graphite lube properties. Works great, last a long time. Must apply before assembly however.

One example:

http://www.skygeek.com/everlube-lub...lubricant-12-oz-tube-mil-l-23398b-plbaae.html
 
Either the graphite particles are encapsulated in paint or something like that or it won't provide any significant corrosion protection. They are far apart on the galvanic series.

For a brief overview, see this.

That paint you referenced provides just that sort of system so it might work okay.

Dave
 
I believe these parts are UHMW Poly. I have a bunch of it I use for different applications other than aircraft.
By definition, UHMW poly is "self lubricating". I am not a chemist but heat build up (friction) between the surfaces produces "asperity's" that form a microscopic "film" between the two parts in contact. This not only lubricates but protects the surfaces from oxidation.
I can not imagine ever needing to lubricate these blocks or the steel weldments, before, during, or after installation. I am pretty sure the factory would have selected this material for this exact reason, but I could be wrong. (Scott will correct me if needed)

If there is too much friction, they are not aligned properly, the required spacers that take up the saw kerf where not installed, or paint or powder coating was left on the surface.
 
rvbuilder2002 said:
Generalizing can be dangerous.....

I think the Grumman leg is constant diam.?

The RV-legs are not. There is a narrow contact point where it exits the socket, and a knob portion at the upper end where the bolt is. The rest of the leg portion that is within the socket is reduced in diam, and a small (very small) amount of deflection in this area is expected under load.

So, for rust protection, and to prevent wear, the plans recommendation is for grease at these locations.
Click to expand...

Thanks for the clarification.

If the joint is protected with grease, then the need for accurate holes and absolutely no slop in the bolt mounting is essential.
 
az_gila said:
If the joint is protected with grease, then the need for accurate holes and absolutely no slop in the bolt mounting is essential.
Click to expand...

Agreed

That is why the sockets are made with an undersized hole on one side so that the builder can match drill, and why a .311 drill is specified (don't just run a 5/16" drill through since that is what the bolt size is)
 
I bought an RV-6A that had been sitting for a few years in a dry climate. The rudder and flap weldments were rusted where the paint had been taken off (including inside the bearing blocks). Had to disassemble and clean off the rust. Coated the bare steel with LPS 3 which dries to a waxy film and won't attract dirt when dry. Works well for the cowling hinge pins also.
http://www.lpslabs.com/product-details/612

Cheers, David
 
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