Fixing a pesky 151 Semaphore

there is a plunger in a tube inside the 151. goo, grease, oil that has dried up, can fowl up the plunger. the spring cant overcome it, if its binding up in the tube. if you want, you can take apart the 151 and clean these parts with rubbing alcohol. it should work good anywhere from 12-14v. also, check shaft alignment, making sure the post is nice and square so the shaft isn't trying to move in some awkward motion.......hope that helps! 

I cleaned up the plunger and tube inside the coil really well and checked it's motion before I reinstalled it.  I appeared to be working well.

was there goop inside the tube? does the coil appear to have been overheated? the evidence of that would be the coating from the coil all gummed up in the tube.....check rack alignment to the gears where they mesh, maybe the rack is trying to saw into the housing, if you know what I mean...also while you had it apart the flag should really be nice and free, no binding spots on the little pin it rides on

The 151 has a pretty well known reputation for being finicky. Even with a thorough cleaning, the tension has to be just right for it to throw the arm down properly.

Check the flag to make sure the teeth on the gear aren't worn.   If they are, drop Jeff Kane at The Train Tender a line, and he can fix you up.

I"ve had a couple where the lamp wire was rubbing against the operating shaft inside the post.

Another source of friction is the aluminum rod. The rack gear on the rod will sometime bind on the cut out on the pole. Make sure the top of the pole is not bent out of kilter. Is the Semaphore arm original or been replaced? If the arm pivot pin as been removed, it must be replaced perfectly square or it will bind in the hole in the casing.

I won't have time this weekend, but I'll take it apart again next week and see what I see and report back.  Thanks for all the things to look for!

I was able to take it apart and do some more inspection.  It looks like the issue is slop in the gear - not worn teeth but wobble - like the post securing it isn't tight enough.  I'm concerned if I try to tighten it, I'll get too much friction.  Has anyone seen this before?  Any ideas?  Thanks!

John Fuller posted:

I was able to take it apart and do some more inspection.  It looks like the issue is slop in the gear - not worn teeth but wobble - like the post securing it isn't tight enough.  I'm concerned if I try to tighten it, I'll get too much friction.  Has anyone seen this before?  Any ideas?  Thanks!

If memory serves from when I last overhauled a 151, the post will bottom out without binding the arm.  Tighten away!