Isolation of motor brushes: 0-10-0 switcher

[tstage]

Greetings all -

I ordered a Loksound Select Micro and speakers for my H20-44 this evening so I'm waiting for them to arrive in the mail before proceeding on with that project:

http://cs.trains.com/mrr/f/744/t/260785.aspx

In the meantime, I decided to tackle my other DCC installation project: A brass NYC M-1 0-10-0 switcher:

Even though I've been working on the H20-44, this is new territory for me.  So, I looking for any expertise and wisdom you are willing to impart in my direction.  I just want to make sure that I don't miss anything important.

I removed the shell from the frame, which came off easily after removing one large screw on the underside of the boiler and two tiny screws at the back of the cab:

I used my trusty multimeter to probe all around the frame.  As is common on these older brass steamers: Power is picked up from the engineer-side drivers then travels through the gear box, drive shaft, motor wiring, draw bar/draw bar pin, before exiting out the trucks on the fireman-side of the tender.

Here is the view of the motor and draw bar:

If I disconnect the motor wire from the 2 'o clock position terminal, this isolates the motor from the brass plate on the front side of the motor, where it receives power from the drivers via the gear box and drive shaft.  If I disconnect the motor wire from the 8 'o clock position terminal, this isolates the motor from the draw bar.  No surprise, in either case.

At this point, is the motor completely isolated from the rest of the frame?  Or, is there anything else I need to test or check before proceeding on?

In the event that I install a decoder in the tender, my plan is to replace the uniform-color motor wires with orange and gray wire.  (Or, perhaps black so that it will be less conspicuous between the cab and tender.)  Is there any way to determine which brush terminal is positive (+) and which one is negative (-)?

For track power: Can I use the brass plate on the front of the motor housing for the right rail and the draw bar pin on the underside of the tender for the left rail?

Am I forgetting anything important?  Thanks for the input ahead of time.

Tom

[richg1998]

All my experiences have shown the right rail, drivers side is positive for forward on the locomotive with DC. That would show the motor terminal, 2 o'clock, in the photo is the positive one. Connect a nine volt battery to prove I have read in other forums about a motor that is not marked.

 

Rich

[tstage]

richg1998

Connect a nine volt battery to prove...

Great suggestion, Rich!  Should have thought of that one myself.  Will try that right now...

Tom

[Edit: Worked like a charm, Rich.   In fact, the spacing between the battery terminals and motor brush terminals lined up perfectly so all I had to so was span the gap with the 9V battery.

And, you were correct: Right rail (+) was the 2 'o clock position terminal.  Thanks again!]

[richg1998]

Glad to help. Actually read that quite a few years ago in an old Model Railroader magazine. Did that a few times with a custom motor install.

Time's fun when you are having flies.

Rich

[hon30critter]

Hi Tom:

tstage

At this point, is the motor completely isolated from the rest of the frame?  Or, is there anything else I need to test or check before proceeding on?

Once both wires are disconnected from the frame the motor is fully isolated. The term 'isolating the motor' is a bit misleading. What needs to be isolated are the brushes, not the motor case (or the motor body to use a different term). It doesn't matter whether the motor casing is isolated or not as long as none of the wires come in contact with it.

With can motors, isolating the brushes is simple, but I believe it can be somewhat more problematic with some older 'Pitman' style open frame motors.

Dave

[gmpullman]

tstage

Great suggestion, Rich!  Should have thought of that one myself.  Will try that right now...

[Edit: Worked like a charm, Rich.   In fact, the spacing between the battery terminals and motor brush terminals lined up perfectly so all I had to so was span the gap with the 9V battery.

I believe you DID think of it, Tom... 

_{From your H20-44 post of 1/21/17 1:02 PM}

tstage

For a quick 'n dirty I guess I could try powering it with a 9V battery?

That's a sharp looking M-1 

Good Luck,

Ed

[tstage]

hon30critter

Once both wires are disconnected from the frame the motor is fully isolated. The term 'isolating the motor' is a bit misleading. What needs to be isolated are the brushes, not the motor case (or the motor body to use a different term). It doesn't matter whether the motor casing is isolated or not as long as none of the wires come in contact with it.

With can motors, isolating the brushes is simple, but I believe it can be somewhat more problematic with some older 'Pitman' style open frame motors.

Dave

Yes - understood and implied, Dave.  My main concern was to make sure that current wasn't sneaking in some other way that would eventually fry a decoder.

gmpullman

That's a sharp looking M-1 

Good Luck,

Ed

Thanks, Ed.  I'm having fun learning about brass locomotives and DCC installations.  It's not as complicated as I had originally envisioned.

My only experience isolating motor brushes previous to this was a Proto 2000 S-1 and Walthers SW1 switcher.  The former was nicely formatted by Randy (rrinker) using a pictoral he put together on his website and the latter I read about on another website, which I turned into a step-by-step "how-to" on my website.  This is the first time I've tackled the issue without having some sort of "map".  It's fun!

Tom

[rrinker]

 By the looks of the motor, you should be good. Verification would be checking the continuity from each motro brush to the loco frame with that wire removed. As long as it's all open circuit, you're good to go. I'd also check the condition of the insulating bushing in the drawbar mount, even if you are going to add a wire harness for the decoder - the tender frame is likely hot witht he left rail, if the loco frame is linked to the right rail. A fault here will cause a dead short across the rails, probably NOT blow up the decoder since it won't feed in to the motor output, but then again...

 The whole thing is similar to an Athearn, with the chassis directly connected to one rail - complete opposite of those P2K S1's, with the motor grounded to the frame and the pickups isolated. In one case (the former, like this loco) is fine as long as the motor brushes are then isolated from the frame, the latter (the S1) is bad because a derailment can get track power connected to the motor output which is instant death for a decoder. Which is why the S1's need rewiring, and Athearns just need the tab and some tape on the bottom of the motor (at least in 50% of the time based on my RS-3's - one needed all new wiring from the pickups to the decoder to make it reliable, the other one worked right off just plugging the decoder in).

                               --Randy

 

[DigitalGriffin]

tstage

At this point, is the motor completely isolated from the rest of the frame?  Or, is there anything else I need to test or check before proceeding on?

If you disconnected both wires, and touch both motor power points to the frame once at a time, and the resistence on your meter reads infinity, then you are good to go.

BTW: Beautiful engine

Edit: Never mind.  Seems I'm late to the party again.

[tstage]

I appreciate the input, fellas.  I'd rather double-check and find out that I'm right than make a wrong assumption and pay the price (of a new decoder).  I'll try a spare decoder in her this evening and report back.

Tom

[tstage]

Well, I hooked up the TCS M1P to the 0-10-0 and it works.  It appears that it will need a good cleaning & lube though.  It ran fine (initally) in forward but not so well in reverse - a lot of hesitation and stopping.  After a few back 'n forths forward then developed more hesitation.

For those of you with older brass steamers: Does the gear box generally have a bit of lateral (side-to-side) play to it?  (This one seems to have at least 1/16")  There's some front-and-back slop, as well, but not to the extent of the lateral movement.  Could this also contribute to the poor running in reverse? 

As an experiement I decided to try moving the center drivers (which the gear box is attached to) laterally with my fingers.  Viewing it from the top, the gear box seems to float freely on the driver axle.  Is that normal?  Or, is that something that could be remedied by placing some 1/32" spacer washers on either side of the gear box?

I've read that brass steamers are/can be more finnicky and need more fine-tuning than brass diesels.  I guess I'll be learning more about brass ownership through this experience.

Tom

[DigitalGriffin]

The slop (play) in the gear box usually shows up between the worm gear and the idler gears.  I've had situations where going backwards causes the work gear to buck up and back a little.  This causes the meshing of teeth between the worm and idler to fail.  

If you can mount the shaft a little lower it might help.  Or press lightly down on the shaft to see if it helps.  Brass worm gears have a tendency to wear down as well.  Another suggestion: Some people like putting bushings at the front and rear to prevent the worm gear slop.

Unfortunately this is where I usually stop and hand it over to an experienced professional builder because the wheels will have to be pulled, and a new gear box put in (NWSL) if I can't get the gear tower to work.  

I do not like messing with the running gear and requartering.  I tried it once on a simple 0-4-0T...never again.

The good news is some people claim the delrin gears are both quieter and might actually last longer than the old gear towers.  I find this claim dubious given my bachmann steam. But I digress.

[gmpullman]

I only have a quick minute for a reply, Tom. Take a peek at this site and you can get a few ideas for re-gearing:

http://shastasprings.com/

Go to the "Guide to repowering" section.

One of the primary causes, I believe, of the directional differences in running is having too much play in the input shaft and to a (slightly) lesser degree the axle side play.

Worm and axle gears have a "sweet spot" where the gears mesh at the optimum back-lash. Too much slop and the mesh is no longer in this sweet spot.

The trick is to provide enough thrust washers to minimize the play but still allow free turning of the shaft. This is more important on the input shaft. Larger gearboxes will have ball-thrust bearings here. I have had some luck with using Kadee truck spacing washers to help take-up a little worm shaft slop. Red #208s are .015 and gray #209 are .010". They are much easier to install than trying to pull the wheels to shim the axle slop. 

Another good idea is to be sure there is a "torque arm" to help keep the box from transfering radial forces on any of the shafting or universals or even the motor shaft itself.

Good Luck, Ed 

[tstage]

Don & Ed,

Thanks for the feedback, info, links, and suggestions.  Ed, I have the "Guide to Repowering and Regearing" link bookmarked.

Apart from the gears, the motor runs very smoothly.  For now I think I'll start with a good cleaning and lube then proceed from there.  Eliminate one thing at a time, as any good troubleshooter knows...

Tom