Equalizer hitch failure
This was our second trip with our new Zinger 27RL and the new equalizer hitch that we purchased when we picked up the trailer. The first trip was about 20 miles each way to overnight at a local RV pa...
Forum Discussion
Teamfour wrote:opnspaces wrote:
I had some cracks in my sockets and exchanged a few emails with Progress mfg. That's how I found out about the case hardening.
What did Progress do about the cracks? I noticed a very small one two days ago in the top of one of my tubes. The ball shank is the right one, so no issues there.
This has gotten one of my interests...design forensics
Initially thought CAST IRON from the pictures...could be steel, but why
would they harden it clean through??? The break is indicative of cast
iron or hardened steel. There was no indication of ductility in the
break
Can see why hardening is necessary, as they use the friction between
the hitch head to trunnion sockets as one anti-sway component.
This is NOT "case hardened", as that meant to only harden it on the
surface down to a specified depth....to leave the core material ductile
A case hardened would have a different crystalline structure across
the break. From hard (case) to ductile (core)
Steel tubing makes sense, as to cast that thin section would have been
costly. Assume they used cold rolled, as hot rolled requires secondary
and tertiary treatments
I'd have left it cold rolled and instead of hardening for wear attributes,
have sacrificial friction material. Just like friction bars.
As for the cracks on a setup with the proper ball shank length...think
it's with the clear through hardening and the Rockwell C number they
hardened it to. Find that number out and if it is above a certain number,
then becomes brittle
Sorry, it's been decades since my last usage of this area...but...that
number can be looked up. Am guessing it should NOT be above 35...but
harder has higher abrasion resistance...an oxymoron...
