Happijac lubrication
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Forum Discussion
jjinatx wrote:
I think I figured out the dynamics of the thing, but am puzzled why it was designed that way.
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Lowering, however, the spring tightens, locking the 2 barrels together. Now the upper barrel is forced to spin against that squarish plate. The friction is apparently meant to work like a drag brake.
You answered your own question there. It's meant to act as a one-way drag brake to keep the camper from falling. There no reason for your camper to suddenly lift and very little force making the jack fall down when on the truck.
jjinatx wrote:
Curiously, the 4100 jacks do not have this drag brake mechanism.
This is probably because the camper weight cannot backspin an acme thread but can backspin the recirclating ball setup. Notice how much steeper the threads are? Steeper = easier to backspin. The drag brake adds enough extra resistance that the camper will not fall while the motors can still power it down.
