A pig in a poke...

[Bob]

For the last few operating sessions I brought over a recently-procured SW9 eBay win sold by an un-named hobby shop. It looked like it had been run a lot but did run perfectly on my DCC test track with a Lenz decoder.

Well, it didn't run on the A&O. I finally found the root cause. Above is one of the culprits, below a replacement from a parts donor locomotive taken out of service for cracked plastic gearbox covers.



The seller failed to disclose that it was worn out. Grooves were also worn in the back of the Atlas wheels! I suspect it had run on an oval demo track at the hobby shop for months straight until it started to stall on the curves.

Hopefully this will put an end to the Morrison operator's frustrations.

[Big Train James]

Since the sw pickups are relatively hard to come by, I ended up drawing up a knockoff in cad, then having it printed by Shapeways.  The photos show the 3d print in the FXD material.  It's a nice press fit into the holes in the sw gearbox housing.










I was never much of a fan of the way Atlas executed the design, so of course I made some changes.  I also needed to account for the increased possibility of shorting, since my revised Flexicoil sideframes were going to include a good portion of the bolster, which would then need to wrap around the pickup mount.   I designed the pickups to utilize the Rod Miller etched phosphor bronze pickups, which I prefer to the wire that Atlas used.  I also originally accounted for the use of a terminal lug on the lead wire, but I've since decided that the lug may not be necessary.  The whole assembly would be held together by an 0-80 nylon screw.

Now that I've been reminded of this, I should test print some new pickups myself.  The Shapeways prints are a bit brittle, which isn't unusual for the material. 

Jim

[Bob]

Looks like a great design, James! There will be a lot less drag on the wheels than with the stiff Atlas wires. I'm intrigued by all the great work being done with 3D printers, but I just don't have the time/inclination to learn the CAD behind it all.

Please stay in touch and share your progress with us.

Should anyone be curious, here are two photos showing the context of how the wipers are installed. The first is during removal of the worn pickups, second the replacement from a donor engine.

[RickBacon]

That's a crazy wear pattern!  I'm guessing we need to check all the Atlas O Scale SWs running around the mothership.  I know the stand-alone SW unit at Millport is having sputtering issues.  I've been assuming it is a dirty wheel or dirty track issue. 

It looks like Jim's efforts are a big improvement.   

[Big Train James]

Looking at Bob's install, I think I will revert to using a terminal lug, and switch to using a straight pickup without the tab.  I'd rather have the option to detach the motor lead without having the pickup strip hard-wired to it.

The other thing I don't much care for is how the pickup covers the middle hole at the base of the gearbox, and by extension blocks access to the screw that holds the gearbox halves together.  I suppose the pickup and mount could be reshaped to wrap up and over the hole, but that would require modifying the gearbox with a new hole for relief for the screw that holds the pickup assembly together.  In reality, if you are breaking down the gearbox to the point where you need to unscrew the two halves, then it's not a quick repair job anyway.  So I don't think that mod is worth the effort.

For now, I'm happy to be able to remove the motor lead and pickup bar without having to remove the mount from the gearbox.  I'm also happy to be able to replace the pickup without having to replace the entire assembly.  Not that I expect to run enough miles to wear out pickups as in Bob's example, but better to be prepared.

Jim