tables "jumping"

[kryley]

This is just a question relating to a long-time problem we had at the first centre I worked at that neither myself or the Head Tech could figure out.

A few of the tables at garden city used to "jump" at zero. For example, they would go through a respot cycle say, and when the table returned to zero, it would jump so to speak. If you turned the table switch off at the backend control box while it was doing this, the table would coast down until you turned the switch back on, then the table motor would kick in and take it back up to zero.

We tried changing the table gear box and motor, but that was no good. We didn't have any spares to change the table drive assy so we ended up not worrying about it.

The only thing we could put it down to was the table contactor in the chassis was screwed (I seriously doubt it though) or the table drive assy....

I only just remembered this today, it will be interesting to get some ideas on what it was after all this time!!

Thanks....

[Pindecked]

Re: tables "jumping"

Your table drive ass'y is slopping on the drive shaft.I've had to loosen the bolt up,& insert a .005 shim & tighten the heck out of it to rid of that 'jump' on old machines.

[andy-m]

Re: tables "jumping"

If you are refering to the 82/30, that problem is caused by a loose spotting cam, and/or a worn key or keyway in the table shaft. Ran into that hundreds of times!

[Ed Fox]

Re: tables "jumping"

Sounds like your talking about 70's. Am I correct saying this?
Ed

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[Jimmy Jam]

Re: tables "jumping"

No gearbox friction

[Dutch]

Re: tables "jumping"

Kryley,
There are a lot of things that will cause the table to coast backwards.
Like Jonas said… No gearbox friction is your main culprit. Check the oil level.
If you’re running National motors, the bearings are probably dry & the break needs new carbon brushes.
A bad breaking circuit can also cause it. If the motor isn’t coming to a dead stop, it’s like rocking a car forward to get it to roll backward. If you’re using solid state switches, the switch could be bad or, more likely, the lower contacts and/or CTM-2 are bad.
The table drive assy shouldn't have anything to do with this problem. At least I've never seen it.
You can temporarily compensate for this by setting the stopping position of the table closer to 0 degrees.
Dutch

[This message has been edited by dutch (edited 12-03-2000).]

[8270king]

Re: tables "jumping"

If your combos aren't nationals, just take the bad one to the bench, put it on its side, take off the end cap, pull out the thinnest shim leaving the rest of the shims, reinstall cap with some silicone sealer, and you will have the friction you need to end the coasting in your gearbox.

king

[kryley]

Re: tables "jumping"

Sorry, I forgot to mention that the machines were 82-70s...

I think they are running Westinghouse still (remember guys this is the centre I USED to work at - I just thought of the problem the other day!!). Just before I left we checked the oil in the gearboxes but that didn't seem to help (the gearboxes are screwed which probably wouldn't have made things any better!!)

Thanks for your input.... it's still interesting even though I don't have anything to do with that centre anymore!!

Thanks...