671 vs 681 Performance

Older 671's with the large motor and horizontal drive shaft (1st and 4th driver set geared) do run slower than the later 671 and 681's with the canted motor. Different gearing.

Actually I should have said my 671 and 681 look EXACTLY alike under the covers except for a small cover over a hole. I know the 681 has magnetraction but there isn’t a grade on my layout.

Your 671 might be in need of servicing.

As Chuck pointed out, the only reason a 671 might be slower is if it were the 1946 model with TWO worm gears and a driveshaft running fore-and-aft in the chassis.  The '46 model also has a "smoke bulb," which was replaced by a wound-wire smoke element when Lionel redesigned the loco the following year.  After 1947, the only other changes were the addition of Magne-traction in 1950, changing the number to 681.  Later in the '50s, a lubricator linkage was added to make the 682.  It sounds like yours is one of the redesigned 671s (a photo would confirm this.)  So if it's properly serviced and not worn out, it should run about the same as your 681, except with less traction and cornering grip.

One common problem with Turbines and Berks is that the motor is geared to the last axle.  Over time, the torque causes the rear axle bearings to wear in an oval shape.  This allows the rear wheel to rub on the chassis.  If it gets bad enough, the loco will hesitate, or not run at all.  Unfortunately, replacing the axle bearings is an expert-level repair best accomplished with wheel cups and an arbor press.  Lacking those, some people insert one or more plastic clips from loaves of bread between the worm wheel and the inside of the chassis to keep the axle centered, temporarily restoring smooth operation.  Good luck!

@Ted S,

Thanks.  I've become pretty skilled in the fundamental 1950s electro-mechanical stuff.  I'm sure that virtually all normally serviced aspects have been done properly.  Your hint on the axle bearings is something I'll look into tomorrow, as well as post a picture of its innards.  I can say it doesn't have 2 worm gears nor smoke bulb.

I had a slow running 671 once. Like you, I went through all the normal maintenance but could not correct the problem. The problem turned out to be that the commutator slots at the outboard ends had been packed with a carbon- oil mixture. This was conductive and was shorting the commutator bars. This got so hot, I could see red heat while running in the dark, that it carbonized the Bakelite plastic that the commutator was made of. Once the Bakelite turns to carbon the problem just continues to grow. Apparently the carbon had enough resistance to allow the motor to continue to run, but slowly, but low enough resistance to creat a lot of heat. Once I was on to what was happening, the problem was apparent.  There was a small round circle at the end of the slot. Working on it with a dental pick, I could pick out the crumbly carbon chunks.

The fix was to change the commutator.  This also required changing the felt pad under the commutator, as it was oil soaked. Since then I have run across this same problem several times and changed several more commutators. The commutator is pressed on the armature shaft, which is slightly knurled.   Do not start this repair until you have a replacement commutator in hand. Many commutators are either burned or cracked at the ends of the slots, and they are likely to break when being removed. The two things to watch when replacing a commutator is that the slots go back in the exact same location with respect to the armature coils and that the commutator gets pressed down to the proper location so it works properly with the brush plate. Most post war commutators started with the 226E-?? Brush plate. There are a few where the commutator segments are bonded to something like mica or plastic sheet, but I like the molded Bakelite commutators. I have seen the 226E commutator with a 2333-?? number, but I can see no difference in them. Last time I checked Jeff Kane was selling post war Bakelite commutators.

Look at the backsides of the last set of drivers on your 671. If you see a shiny wear spot on the backside, and a corresponding shiny spot on the frame, the axle bushings are worn, and that lets the driver act like a brake shoe against the frame. This problem is more prevalent in forward motion rather than reverse. In reverse, the axle shifts to the other side and the affected driver moves away from the frame. I’ve seen this happen on 671’s & 726’s with the rimmed drivers…….several options to fix, the old bread bag clip trick in the gear box, or new axle bushings, or my preferred method is the right sized stainless shim between the affected driver and the bushing. …..I agree with David, I’ve seen commutators so over saturated with oil & carbon they’re cooked…but diagnosing the issue is key, ….the tell tale for a worn axle bushing is better operation in reverse vs. forward,…..then the clues will be shiny spots on the back side of the driver, and witness marks on the frame …….

Pat

Here's a picture of the innards of my 671.  The only visible (to me) difference is the area that the (poorly drawn) white arrow is pointing to.  The 681 has a cover of some type over that, and in the 671 it's just a hole.  I did rewire it with new cloth wires as found in the original.  You might see a slender set of wires.  I took out the screw in incandescent bulb and replaced it with an LED.

I'll be investigating the above suggestions now, mote to follow.

From the looks of that chassis, that’s either a 671RR, or a 681 chassis with a 671 shell…..if it’s a non-magnetraction engine, it’s a RR ……it should fly like the wind without magnets to drag it down…..so something is amiss if it don’t have magnetraction…….

Pat

Many magnitraction steam locos have a steel plate just inside the drive wheels to conduct the magnetic flux to all of the drive wheels. If this design was used on the 681, and it is missing, I think that would nail this loco down as a RR.  Another telltale feature of the RR would be steel, rather than stainless steel, axles.

It's a RR chassis, so since the RR version is the same as the 681 chassis without the magnet in theory they should be near identical. Run it for a while and see if the motor gets excessively warm. Too many shim washers on the armature?

@Chuck Sartor posted:

It's a RR chassis, so since the RR version is the same as the 681 chassis without the magnet in theory they should be near identical. Run it for a while and see if the motor gets excessively warm. Too many shim washers on the armature?

Or perhaps the shims under the motor Chuck & Dave?….too tight a mesh?….angry growler??…

Pat

Thanks to all who provided very useful suggestions.  After some research I agree with y'all that it is a 671RR.  It is identical to my 681 except for the area I pointed to in the pic (open in my 671, a small plate covering it in the 681).  Perhaps that's the plate that @David Johnston referred to for the magnetraction?  Also, since I was born in 1952, the year the 671RR came out, it's reasonable to assume it's the one that was available for my dad to purchase.  Plus I do have the 2046W Pennsylvania whistling tender that came with it.  I no longer have the original boxes (one of the few original boxes from the 50s that must have been tossed).

Okay, back to my original issue, I didn't see any shiny spots @harmonyards, and for you and @David Johnston, I had to look up what a commutator was.  I'm familiar with the part, just didn't know the name.  Actually they look okay to me.

I stripped it apart as much as I could handle one more time.  I carefully inspected the drive wheel assemblies and it turns out I didn't do a very good job cleaning them.  I got my isopropyl alchohol, q tips, crc electronic cleaner, toothpicks, and paper towels and gave that area the cleaning it deserved.  Gunk did come out, not a lot though.  I re-greased and re-oiled the parts needing it, and put it back together.  It runs great now.  It derails at about the voltage that the 681 did (I packed away the 681 and was too lazy to get it out for a side by side comparison).  I'm guessing the grease/oil in the critical places was the key here.

Thanks once again.

My 671 RR from 1952 Christmas ran like a spotted *** ape (if I am allowed to say that).  When I double headed it with my 681 pulling my coal train it would really smoke.  However without the 681 helper it would go really fast in one spot but did not pull much.