Need Help With 726 E-Unit

[Dampfmann]

I am restoring my father's 726 Berkshire that I believe was manufactured in 1947.  Everything looks good, but I encountered a problem when I put the locomotive on the test track.  When the transformer voltage is increased, the locomotive will begin to move forward, but then it suddenly stops.  After a few seconds the E-unit will begin humming again.  If more voltage is added to the transformer, the same thing happens.  The locomotive moves forward a few inches and then stops.  The same happens when trying to run in reverse. 

Seems like there is a short somewhere.  Is anything supposed to insulate the E-unit to keeping it from contacting the frame?  It does touch the side of the frame when the screw that holds it in position is snugged up.  I didn't see any insulating washer in the Greenberg book, but maybe I missed something.

Thanks for your help,

Martin

[servoguy]

The E Unit should be grounded to the frame to work properly.  Does the E unit cycle properly?  I have 3 736 locos.  I checked one of them a few days ago, and if I push it on the track, the wheels turn.  The friction should be low enough on any of the worm drive steam engines that the wheels will back drive the motor.  If yours won't do that, I suggest you lube it.  There are a lot of lube points on a 726/736.  Use 5W-20 motor to lube everything.  I have been using motor oil to lube my trains for 50 years.  It doesn't dry out and doesn't get sticky.

[TrainLarry]

Martin,

  The e-unit needs to touch the frame in order to ground it, or the coil will not energize.

  If you have not already, oil the wheel bearings, grease the gears, and overhaul the motor to start with. Clean the pickup rollers and wheels of any dirt, grime and crud. Inspect the e-unit contacts and drum for wear and dirt, proper alignment of contacts with the drum, and inspect for proper operation. The track needs to be clean and free of dirt and rust also.

  Most problems are solved by taking these steps.

Larry

[servoguy]

What transformer are you using?  Are you sure the circuit breaker on the transformer isn't tripping?  And if it is, is the loco drawing too much current?

[Dampfmann]

The loco is pretty well lubed.  I just oiled and greased it so I don't think that is the problem.  The locomotive does turn the motor when pushed, although I need to push down to get enough adhesion with the track to turn the wheels.

You mentioned something about the locomotive drawing too much current and that got my attention.  I am testing the loco on an oval of Fastrack using an 80W transformer.  When I first tested the loco, it ran great.  Then I decided to "load test" it and have it pull 6 passenger cars.  Come to think of it, that's when the problems started.  I just pulled all the passenger cars off the track and had the loco run light.  No problems!!

So what is going on here?  Is this a problem with the transformer?  Is it too weak to power the loco and the lights on the coaches?  Would I have the same problem if I hooked up my ZW?  I'm thinking, no.

Looking forward to your responses.  (I'll check tomorrow.) 

Thanks,

Martin

[TrainLarry]

Martin,

  If you are pulling postwar passenger cars, make sure their wheels and axles are well lubricated also. Older rolling stock (before the modern era and the introduction of fast angle wheelsets), have much more rolling friction, especially if left unlubricated. This could be putting a bit of a strain on the locomotive and transformer, but should not be enough to cause the train to stall. Try putting one car at a time behind the locomotive and see what happens.

Larry

[ADCX Rob]

Dampfmann

Is this a problem with the transformer?

Not a problem, just the design.  5 amps output and that's it, iit will go into "foldback" mode.

 

Is it too weak to power the loco and the lights on the coaches?

You are trying to draw more than 5 amps from it, that's all.

 

Would I have the same problem if I hooked up my ZW?  I'm thinking, no.

No.

Thanks,

Martin

[phillyreading]

Now that you say the engine is running good, try using a more powerful transformer like a KW or ZW. Both the KW(180 watts) and ZW(250 watts) have a lot more power than any 80 watt transformer has. Hopefully you are not using the CW-80, as it has problems with older trains needing more power.

[servoguy]

I think you may still have a lube problem with the loco.  If you have to press down on it to make the wheels turn when you push it on the track, it sounds like you have more friction than you should have.  As I said, I have three 736s and one 671 and they will all backdrive the motor when I push them on the track without me putting downward pressure on them.

BTW, if you take the loco apart again, I would suggest you remove the grease and oil the gears.  The grease is likely going to harden over the next few years and you will then get to remove hard grease.

[cwburfle]

Perhaps I scanned this thread too quickly. I did not see any comments about cleaning the motor. Perhaps the brushes, brush holders and commutators need cleaning.

As far as being able to push a worm drive locomotive goes:
Whether a worm wheel (gear) can turn the worm is dependent on the pitch of the worm.  When the worm wheel turns the worm, it's called Backdriving.
Off the top of my head, a 1947 Berk iis probably not geared the same as a 736 ir a 671, so it's backdrive characteristics may be a bit different.
Here is some information on worm gear setups and back driving:

http://www.salemcompany.com/cgi-bin/Store/pdfs/gearsClsect4.pdf

Finally, it sounds like your loco may have some binding in the mechanism. Sometimes the wheel bearings get worn, and either the backs of the wheel(s) rub on the frame, or the worm gear rubs on the sides of the cavity in which it resides. Usually only one side is affected.
Another source of binding could be wheels out of quarter, or a bent axle.  You may also have a loose wheel.