loose center pin on 422

MossRoad · Mar 11, 2003

( this was sold as new,they have there own planes )

Ah yes, I remember now. Glad you caught it.

Anonymous Poster · Mar 24, 2003

I recently checked most joints and I'm finding the spherical ends are rotating about the "pivot" bolt because the welded tabs are "too" far apart and not "squeezing" the black sphere
pivot, even if nut is drawn up tight. Of course, Terry, said not to worry but it's my nature to worry more when I hear those words... /forums/images/graemlins/crazy.gif
He said that bolts are inexpensive compared to the spherical joint and easier to replace, I agree ,but forgot to ask, which part is longer wearing(harder)?

Charlie_Iliff · Mar 24, 2003

Bruce:
I talked to Terry about that when it first came up. I think you will find that the grease fitting is set up to grease between the bolt and the hole in the heim end, so the joint was designed to pivot on that bolt, not to turn the ball in the heim joint. The ball end is to facilitate the oscillation, not the turn, although the ball joint does allow rotation, as well. The tabs are deliberately set far enough apart not to squeeze the ball, thus also ensuring clearance between the heim end housing and the tabs in oscillation. The bolt should only be tight enough on the tabs to keep the bolt itself from turning. If the bolt turns, eventually it will wear the tabs, which are softer and would be a pain to replace.
Generally the balls in the heim ends are hard, so the bolt will wear faster unless they put in a super hard bolt. If you keep it greased, however, it will be a long time before anything wears much.

johara1 · Mar 24, 2003

bmkar,
i too had the same thing,but i was able to draw it tight. if it was made to rotate on the bolt why would they go to such a elaborate set up?the bolts are grade five,i would guess the steel is hot rolled.guess what will wear? the holes will,i would think.
with the bar out,put the bolt in the hole,check that out. now check how loose the bolt is in the ball.now the normal play in the socket,add all that up and take that times two.
if you want to get rid of some of that you can,if the gap is much to draw up,put a shim (washer) in between the ball end and the frame.
did you see the little ground grooves in the ball ends? make sure they are up,when you put it back together. /forums/images/graemlins/laugh.gif

Charlie_Iliff · Mar 24, 2003

if it was made to rotate on the bolt why would they go to such a elaborate set up? 
Jim: I haven't talked to the people who actually made the design decision, but I think it really isn't elaborate. The joint has to facilitate both articulation and oscillation, and this one does, using off the shelf heim joints, so not much fabrication is necessary. As you know, a lot of the machines' systems and components are off the shelf, which keeps our cost down.
 i would guess the steel is hot rolled.guess what will wear? the holes will,i would think.
 I agree -- that's why the bolt should be tight enough to keep it from rolling relative to the mounting tabs.
 put a shim (washer) in between the ball end and the frame.
 If you add a washer, you probably want to jack the machine and run the oscillation to its limits and make sure the joint doesn't bind. If the outer housing of the spherical rod end binds against the washer or the tabs, it becomes very high load, very fast.

bubenberg · Mar 24, 2003

i feel like charlie brown: this is deja vue once .... or whoever said that /forums/images/graemlins/confused.gif /forums/images/graemlins/grin.gif /forums/images/graemlins/blush.gif /forums/images/graemlins/wink.gif /forums/images/graemlins/laugh.gif /forums/images/graemlins/mad.gif /forums/images/graemlins/ooo.gif

Anonymous Poster · Mar 24, 2003

( you will find that the grease fitting is set up to grease between the bolt and the hole in the heim end, so the joint was designed to pivot on that bolt, not to turn the ball in the heim joint. The ball end is to facilitate the oscillation, not the turn, although the ball joint does allow rotation, as well. )

Thanks Charlie, so far so good...

( The tabs are deliberately set far enough apart not to squeeze the ball, thus also ensuring clearance between the heim end housing and the tabs in oscillation. )

Now I'm wondering if I overtightened the top-center because the ball end is "scraping" or "reaming" the flat inside surfaces of the tabs, another wear point in this design, but maybe not critical?
When I tightened the top/center, I was able to close in on the ball end and the bolt itself was not spinning--maybe I should undo what I've done...what you think?

Anonymous Poster · Mar 24, 2003

I know I jumped on this wagon after it turned the corner, but in understanding the "designed" wear pattern...

( put a shim (washer) in between the ball end and the frame. )

This should fix any of my concerns.

Charlie_Iliff · Mar 24, 2003

Bruce: As Terry told Johara1, if you tighten the tabs, with or without shim, so that the ball is clamped between the tabs, it will still allow the machine to turn, and so long as you keep the ball lubricated, it will last a long time. The the only real problem will be if the outer housing of the ball joint gets against the tab or the shim or washer before the oscillation stop. Terry told me he thought it generally would not. It's worth checking, however, because that would not be a wear problem, it would be a potential fracture. If you don't clamp the tabs to the ball, as long as the bolt won't roll, there are redundant lubricated turning joints at the inner and outer ball surfaces, and the ball itself shouldn't wear the tab(s) significantly.

Charlie_Iliff · Mar 24, 2003

I think it was Yogi Berra who talked about "deja vu all over again." Or, it might have been Casey Stengal. Casey said everything Yogi said - just earlier.