Busted GB259d roll pin

[KL Kevin]

Just when I was starting to think I'd seen it all ...

Had a machine today that out of the blue just decided it wouldn't set a new rack. Turned out the roll pin that holds the MD/scissor latch to the D shaft was in 3 pieces.

Machine seems fine now, but I got this bad feeling I haven't seen the end of this. Anyone else seen one of these break, and a clue on what might have caused it?? Flag seems to have no binds now, although it wasn't moving right till I changed the pin.

Kevin

[Mike Wilson]

Re: Busted GB259d roll pin

I have seen it one time, was a long time ago so I dont remember if I had found a cause or not. Never saw it again so I think at the time I just chalked it up to old age.

Mike

[masternut]

Re: Busted GB259d roll pin

I have had it happen one time also...I also could find nothing to contribute to it breaking. Roscoe may have some insight to what leads up to it breaking.

Peanut

[billman]

Re: Busted GB259d roll pin

This must be a once in a lifetime thing!! I also have had it happen once, about 6 years ago. Never did find a cause and has not happened again. (knock on wood)

billman

[Roscoe]

Re: Busted GB259d roll pin

K.L.
I see it about once a year, enough that I carry a supply of them with me, as its the only pin that will work satisfactorily.
I have always associated it with a machine that has broken the MDCF shaft bolt, and allowed the cam follower to bind on the flag as it was tring to go home, thus cracking the pin, setting up a future failure. I have seen the timimg cam broken too, from this failure.
Roscoe.

[A2goldman]

Re: Busted GB259d roll pin

I have seen this twice, in 2 different centers. On the first machine, the flag was loose (almost falling off) at the 1:1 cover plate. The second machine the latch was installed backwards on the shaft and the pin was only driven thru one side of the latch and the shaft.

[KL Kevin]

Re: Busted GB259d roll pin

The little !#$@#%@#$ is back ...

Upon further review, here's what I turned up:

All shafts in the gearbox are in time, by the marks, in appropriate inspection holes. Detector is in time, both by side cover mark, and strike cam follower is in low dwell at 90, strike.

MD/scissor cam is retarded by approximately 1 tooth (slash mark on cam doesn't run through center of scissor cam follower until 4/1 is advanced about 10-12 degrees)

Seeing as the machine can't be in, and out of time at the same time, I think the 1/1 shaft itself, or the key have twisted (Cams don't rock, so keys are intact).

As weird as it sounds, the machine runs fine this way, except it likes to break one of these roll pins every couple months.

The question is ... would the cam being say 12 degrees retarded cause stress at the wrong times enough to break this pin?? Never had any other machines do this, and really would like to know the reasons:

Kevin

[Roscoe]

Re: Busted GB259d roll pin

K.L.:
Most likly a twisted key, and yes that will break the pin, as the cam is retarded while the gear driving the detector is not The result is the detector is trying to move the flag before the cam has fully moved the cam follower.
Roscoe

[junkmonkey]

Re: Busted GB259d roll pin

sounds fun!