4 Place gear strut service

[kestrel]

My mechanic has my gear struts apart to replace worn seals.

- How much oil should be put back in?
- What type?
- Any other pointers on how to service these?

Hmmm... My gear struts are not "standard". They were custom built with longer travel. That may impact the advice that I'm looking for.

Since these are not "oleo" struts, should they be "filled"?

Thank you in advance for any advice!

[Battson]

What do you mean by "not oleo struts"?

Hard to comment if you have a non-standard setup, but as a rule you need maximum fluid inside the strut for them to work most effectively.

Longer travel sounds like potentially a bad thing, Bob said the dimensions are critical and the loads go up exponentially as the gear travel outwards. Therefore I assume that if the gear travels too far, design loads could be exceeded.

Mine have done almost 700hrs from memory, and the seals are still fine. I am interested to know what caused the wear and tear.

[kestrel]

They are not Air(nitrogen)/oil struts. They have a metal spring instead of a nitrogen charge.

https://en.wikipedia.org/wiki/Oleo_strut

Bob is aware of how this one was built and it was considered as a change to the plans. He may have fabricated them? He had a hand in some of the other modifications to this plane. From what he said, the change wasn't made to the plans because it wasn't clear to him that it was an improvement, not because it was a problem.

There is nearly 700 hrs on this one. When I first bought it, it was quite unforgiving of hard landings. The gear was "firm". After spending some time learning to fly it, I noticed that the gear seemed much softer. There may be other explanations like different tire pressure, pilot technique or pilot expectations, but I'm suspicious that the struts were "stuck"(?) when I bought from not "getting used". Perhaps the rods were dry? I definitely put the gear to use while learning to put the Bearhawk down where I wanted it. I have little to compare to as this is the only Bearhawk I've flown. Esp. now that they are soft, I often make "good use" of the struts doing things like stopping the descent with the tailwheel just abive the ground and the mains well above the ground and then lowering the nose to land on the mains. The result is reasonably gentle, but does exercise the travel of the struts.

You say, "maximum fluid". Does that mean fill them full?

Thanks!

[Battson]

Right I am with you... semantics around the definition of oleo.

Bearhawk "shock struts" should be filled with as much fluid as possible. But don't get too worried about leaving a little air in there, i.e. you don't need to remove the struts to refill them, it will be OK.

Some will leak out of the grub screw threads if they are FULL, unless you use a thread sealant.

We said "oil" before, but I think we both mean ATF (automatic transmission fluid).

[Mark Goldberg]

Tyson, your mechanic called today and I gave him some guidance. I can send new orings next week if they are needed. Mark

[kestrel]

Thank you for the help. :-)

[jaredyates]

Ken made a nice video about shock struts, so we added a link to it in the Kit Builder Manual article on the same topic:

https://bearhawk.tips/2501

[AKKen07]

I think I omitted anything about adding the fluid though, unfortunately. I only recorded assembling the parts...