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Belleville washers: wet or dry?

Navy76

Active Member
I watched Vic Syracuse?s excellent webinar on RV maintenance this evening and learned a lot! Thanks, Vic!

I would like to see what others think about Belleville washer installation. On page 40A-07 the note on Step 2 says:

?NOTE: Belleville washers are slightly cupped and in order to function properly the outside perimeter of both washers must be in contact with each other when installed. See Figure 2. Install the washers dry.?

In his presentation, Vic recommends greasing the washers to prevent corrosion and other threads in this forum favor grease as well. I have tremendous respect for Van?s and Vic and, as a first time builder, would normally not question advice from either but it seems as though they can?t both be right.

So here?s the question to my fellow builders... Which is correct in this case, and why?
 
Here is a tiebreaker for you !

Call Craig Catto. He sells the washers and has skin in the game. I anxiously await your finding because I have two setts of washers on order.
 
The plans don't say to lubricate them. I inadvertently greased them very well when I greased the nose tube. When they were greased I couldn't get the nose wheel breakaway force to stay set. I cleaned off all the grease, reassembled, tightened, and have had great wheel performance for 80 hours.

Mine are thus lightly lubricated as I didn't super clean them, just gave them a good drying with a blue towel. But I won't be greasing them again.
 
Orientation

Belleville washers are really springs. Be sure to install them as specified by the designer. I’m not familiar with how many are used on the RV-10 landing gear, but I know first hand what can happen when Belleville washers are stacked as “washers.”

The orientation of multiple Belleville “washers” can have a drastic effect on the spring constant of the stack.

Clarification: For multiple Belleville “washers,” orientation refers to the arrangement of the cup sided face to the adjacent “washer.” They can be face-to-face, back-to-back,or face-to-back with the addition of each “washer.” Yes, it does make a difference. Don’t treat them as just “washers.”

If there ever were a misnomer, this is one. We traced a problem of 55-inch carbon electrodes in a phosphorus furnace slipping in their holders due to Tennessee good ole boys stacking assemblies of 12 Belleville washers any old way.
 
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Hmmm. Perhaps Scott wants to weigh in here, but I've always greased them and have had no problem setting the breakout force. They don't stick, and they don't rust this way.
I've had people call me with steering problems and I have told them how to clean them and put it all back together with grease, and they have called back and told me how much the steering improved.

Vic
 
In lieu of safety wire

I have used on brake caliper bolts vs safety wire without issue, greaseless. Grease is about environment, not about purpose...right?
 
They will get lubricated even if you install them dry, since grease/oil will creep from the bronze bushing onto them.

I would not install them dry.

While we're on the topic of these washers, it's also a good idea to increase the bearing surfaces somewhat (they are basically a sharp edge) as shown here, by using some emery on a flat surface or equivalent. I've not had to adjust mine in 18 years/1700 hours. The sharp edges, if not removed, can carve into the bronze bushing, which will reduce the breakaway torque.

HX8TpsEC5k3eYXzmE9v1247JbPuK1OZ9VgxOEYz1V7lVaLf7vgbnzeJASp4OkoEbWaG2xv3uXnTryZOCDZR1yILhCnZRcg636Pc6CwdV-2CoLbPWVi55Hx6cJyvHMoRZ4k7Xor8RZi-pzcl5mqUOo4A67rjtPOBFuvfihDBH453I1RzIUENtv3Y7vs7YStWZkUgCIwCsS-NRGixKbPpKZdcO7EYs_QuiIZ6XzEJsTQmIE9WocMFkCpd0CsO8WVFSyOy-aw-YrD3suo8t0_N5A-2-NgG2YnPxDuK2cPABjrDPUtdVyQrQnj4TWWoFMP_7f1I508_uhgQj9Tg42GuGsB_mR3f7iAHWyG03Edoc7RxLoCtTQ9RTHyRNe0KEy3hPS2zKTTJomv0Ix-aUrp_gQ0PXs7NwEDyP-vlWT9zLDCA4G1lGGkJb4o-MOuDXHz3GTXfOe9E54_7T7hJa50R7JT-MIqiUwtQyDZKvHpcJNNjjfIkWms4iEcTnhvCCJMmXiJ_NSsDuA4gj_Ud1b1yywZm7bGbygHUQu-ogw7wTAIU5MtsaAhgLRultF7NMp2gpKhisi3O4gYVMv-77IYX0u5dKo5njs2aKj8l6aMikUhF1j5pKs57bNlmZngIjJGEH3M7cJOiROlyNEfmyyCbILEnzMvFmRWgupcl4UcSdKXa5D3Wo9pHAJy3JnaWhPt0LdaXTa0UB6_h8MFszcmCilxAIWo9bU86DIYWzmghyIglRM9_-=w300-no
 
The Grumman Tiger/Cheetah OH manual calls out the their Bellville washers to be lubricated every annual.

Essentially it's the same design as Vans... :)
 
They will get lubricated even if you install them dry, since grease/oil will creep from the bronze bushing onto them.

I would not install them dry.

While we're on the topic of these washers, it's also a good idea to increase the bearing surfaces somewhat (they are basically a sharp edge) as shown here, by using some emery on a flat surface or equivalent. I've not had to adjust mine in 18 years/1700 hours. The sharp edges, if not removed, can carve into the bronze bushing, which will reduce the breakaway torque.

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This is right on. I posted about this issue some years ago but I imagine the pictures are gone with the demise of my photo host. It's not the only issue. The weldment that is the fork travel stop was not made well in my kit. The central tube was proud of the stop plate which made a very small bearing surface area for a quite high load. I have since changed things to provide steel for the belevilles to bear upon.

I lube my washers because they will get greasy on their own. Lubing at install keeps breakout constant. Did it dry at construction but that was 850 hrs ago. Lots learned since then.
 
They will get lubricated even if you install them dry, since grease/oil will creep from the bronze bushing onto them.

I would not install them dry.

+1
Although I installed mine dry, after a while I found they had grease between them anyway, and the breakout force had diminished. I then deliberately greased them (wiped off excess with a finger) and re-set the breakout force.
 
Nose wheel breakout for RV6A?

I also viewed the VANS maintenance webinar and this was my first exposure to the "nose wheel break-out" topic. I own, but did not build, an RV6A so as a non-builder, I have much to learn. Can someone provide a link to an article that explains the background on the topic? I assume this is similar to a tailwheel breakout mechanism.
 
They will get lubricated even if you install them dry, since grease/oil will creep from the bronze bushing onto them.

I would not install them dry.

+2 I started off with a dry installation but as the grease from the bronze bushing seeped onto the washer it significantly reduced the breakout force which resulted in nose wheel shimmy. Finally I greased the washer and set the breakout force which remained constant and the problem was cured. At my last annual I didn?t even have to adjust my greased washer breakout force....it remained constant and correct. No corrosion either.
 
I also viewed the VANS maintenance webinar and this was my first exposure to the "nose wheel break-out" topic. I own, but did not build, an RV6A so as a non-builder, I have much to learn. Can someone provide a link to an article that explains the background on the topic? I assume this is similar to a tailwheel breakout mechanism.

Tom - this is really good stuff in here. Realizing you have a lot to learn is an extremely good attitude to have!
 
There seem to be two separate issues here: effective torque at installation time--which can double with lubrication--and corrosion protection in the future.

If the designer specifies dry torque for installation, then that advice should be followed. If the torque is not set correctly, the spring's function can be diminished or defeated entirely. If the breakout force seems wrong or changes over time, then the stack-up ought to be revisited rather than eyeballing the torque. Grease later entering or leaving the already torqued assembly doesn't change the spring force.

For corrosion protection, how about spraying on some zinc primer after torquing dry?
 
There seem to be two separate issues here: effective torque at installation time--which can double with lubrication--and corrosion protection in the future.

If the designer specifies dry torque for installation, then that advice should be followed. If the torque is not set correctly, the spring's function can be diminished or defeated entirely. If the breakout force seems wrong or changes over time, then the stack-up ought to be revisited rather than eyeballing the torque. Grease later entering or leaving the already torqued assembly doesn't change the spring force.

For corrosion protection, how about spraying on some zinc primer after torquing dry?

The grease changes coefficient of friction. Breakout will go down if initially installed dry even if spring force remains constant.
 
The grease changes coefficient of friction. Breakout will go down if initially installed dry even if spring force remains constant.

After re-reading the -14 instructions, I think I understand the problem now.
The torque specified is not the belleville nut clamping torque, but the fork turning torque. The variation is caused by using the top surface of the top washer as a bearing for the wheel fork insert. It is this friction (well, stiction) that lubrication (and lapping/abrasion) changes over time.

My instructions do specify "Grease the bore of the fork and the spindle surface" as well as "Install the washers dry" in the next paragraph. My morning logic tells me the instructions should be fixed. ;)

So, I'll change camps and settle on: doesn't matter if the nut is dry or lubed, tighten by breakout force but make sure the top washer surface contacting the fork insert is lapped and lubed. An even better solution, as hinted by rzbill below is to insert a proper bearing surface between the belleville and the fork insert.

This thread is timely. Thanks guys!
 
Nose Gear Lessons Learned

You're right, this is really good stuff and helps a lot. Many thanks... On a typically nose gear, many actually snap/lock into a center position. On the VANS nose gear, is it correct to conclude these B-washers simply provide tension to keep the nose gear from flopping around more so than locking into a "center position"?
 
Avoid nose wheel shimmy!

You're right, this is really good stuff and helps a lot. Many thanks... On a typically nose gear, many actually snap/lock into a center position. On the VANS nose gear, is it correct to conclude these B-washers simply provide tension to keep the nose gear from flopping around more so than locking into a "center position"?

Absolutely! I don't think any of the posts mentioned this important purpose -- reducing nose wheel shimmy. I had a Grumman Tiger for 30 years and have had -A model RVs now for almost 20 and nose shimmy is a possibility for both of them. Do what you want with lubrication but realize that the purpose of the Belleville washers is to create enough friction that during landing roll out the nose wheel does not swing back and forth, sometimes violently (!). I have seen 45 degree oscillations to each side.

FWIW on my -14A, I set the breakout force at about 16 pounds with no lubrication of the washers because the next castellation is in excess of 26. This has worked fine for me.
 
Shimmy Shimmy Bang Bang....

Thanks Bill, all of this helps to put together a clear picture of what we should be trying to accomplish.
 
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