Originally Posted by CAT-RN
I not sure how it could be jack pads? If there would be some deflection there it would be just a one time clink?
I believe on mine it's the jack leaking back. (Very little). Or the jack pads settling into the surface their on.
And I haven't replace my pads so I know I didn't respond to your question.
Hi Russell - I never implied that the jack pads deflect. My contention is that the noise comes from the contact area where the round end rim of the hydraulic ram rests on a race-track like ring of the jack pad. At this point contact mating of the two parts, there can be a variable amount of psi (pounds per square inch) which can vary because of the weight from the RV and the angle of the jack pad (when it is tilted).
I'd just like to explain psi with an analogy. Say there is a 150 lb women wearing spiked heels. When she steps on the front of the shoe with a 2 x2 area (4 sq. in), the shoe is putting 37.5 psi on the floor. When she puts all her weight on a 3/8 x 3/8 heel (0.14 sq in), she is placing 150 lb on 0.14 sq in, which comes to 1,071 psi on the floor. No wonder that the heel leaves marks in some floors.
Now back to the motorhome. Say one of the rear jacks is supporting 9,000 lbs. That means (approximately) say the 8 x8 jack pad has 9000 /8x8, or 140 psi between the pad and ground. Even so, if the ground is not firm the pad sinks in. However at the Achilles heel, the contact area of the mating contact of the ram's rim to the pad, there might be 2 sq inches of contact. This means that there is 9000/2 or 4500 psi on the contact. However, if the pad is very tilted with say 1/4 sq inch of contact, there will be 9000/0.25 or 36,000psi.
Punch trough of the ram punching through the pad has happened to our fellow forum members. Just using common logic, I believe that the punch-through occurs after a long duration of metal fatigue weakening at the contact points of the ram to the pad. Does this weakening emit sound. Well I am not a metallurgist, but a PhD metallurgist says yes for some types. See the two links below and especially the second one.......
Fatigue (Failure Mechanism) | Metallurgical Associates
If the noise is from fretting, that is just the two surface grinding in together in knocking down the Asperities. If the noise is from brittle fracturing, I can see this leading to punch through.
On a side note, when I put boards under my old style pads, with the pads being parallel with the moho (non-tilted), I get the bolt head impression of the bolt holding the pad to the ram on the wood pad. Further more, I have no clinks because the bolt head is releaving a lot of pressure off of the the pad. Does that tell you something.
Russell; sorry I unloaded on you, but I just want to get to the bottom of thins clinking thing. I shared my beliefs and hope others chime in.