HELP! Lionel 728 not running smoothly

Hello friends,

Advice needed, frustrated. Lionel 728 2-8-4 Lionel Lines

Problem: Run backwards great, stalls or runs roughly and slow forward

Work so far: Rebuilt the E-Unit twice, then reinstalled new/used previously tested E-unit, no change in operation.
                      Tested motor, cleaned brushes, and commutator. No change.
                      Check and replaced some wiring. No change.
                      Checked rollers, seem fine.

Help me before I jump on the tracks!

ncng

Modeling Southern Pacific and Nevada County Narrow Gauge
Era 1937-1957 in 2 rail O Scale and On3. 

Original Post
Chuck Sartor posted:

Never heard of a 728? You mean a 726? What year,early or late?

Hey Chuck, I found a reference to it in Greenberg's.

It is a pre-war from 1916-1917.      They say it was a special one off, but not sure why they ran this number.   Maybe a special promotion set for some company?

Music, trains, boneless chicken farming
David

A few things I would check when I have a loco that likes to run in reverse, but not well forward. The motor brushes should be in good condition, proper length, end should be flat and square, they should move freely in the tube. The brush springs should have good tension and be the proper length.  The commutator should be clean and smooth.  The slots should be clean. Check the resistance from commutator segment to segment, total of three measurements.  Should be approximately equal and between 1 and 1.4 ohms. The resistance from each segment to the shaft should be checked and should be very high to open circuit. 20,000 ohms or more would be good. 

The 726 locomotives have a worm gear drive. The teeth on the worm wheel are at an angle.  This results in the worm wheel pushing the axle sideways.  One direction in forward and the other direction in reverse. This lateral force can cause wear on the axle bearings. With excess wear on the bearing the wheel can start rubbing the frame, causing the engine to run poorly in one direction. This problem usually results poor operation in the forward direction since most steam locomotives spend most time running forward.  Inspect the wheels and frame for evidence that the wheels are rubbing the frame. This will probably be seen on only one side. This can be fixed by putting a shim on the axle to keep the wheel away from the frame. This can be an e-ring, horse shoe washer, or a cut washer. The other repair is to pull the wheels off the axle and replace the bearings. 

Good luck.

David Johnston posted:

A few things I would check when I have a loco that likes to run in reverse, but not well forward. The motor brushes should be in good condition, proper length, end should be flat and square, they should move freely in the tube. The brush springs should have good tension and be the proper length.  The commutator should be clean and smooth.  The slots should be clean. Check the resistance from commutator segment to segment, total of three measurements.  Should be approximately equal and between 1 and 1.4 ohms. The resistance from each segment to the shaft should be checked and should be very high to open circuit. 20,000 ohms or more would be good. 

The 726 locomotives have a worm gear drive. The teeth on the worm wheel are at an angle.  This results in the worm wheel pushing the axle sideways.  One direction in forward and the other direction in reverse. This lateral force can cause wear on the axle bearings. With excess wear on the bearing the wheel can start rubbing the frame, causing the engine to run poorly in one direction. This problem usually results poor operation in the forward direction since most steam locomotives spend most time running forward.  Inspect the wheels and frame for evidence that the wheels are rubbing the frame. This will probably be seen on only one side. This can be fixed by putting a shim on the axle to keep the wheel away from the frame. This can be an e-ring, horse shoe washer, or a cut washer. The other repair is to pull the wheels off the axle and replace the bearings. 

Good luck.

David,

Thank you for your help on the 726. Commutator is clean, brushes and springs look good, clean, operating correctly.

But with OHM meter set to 200, I got 2.0-2.1 between two, then 2.0 between another two, then 3.6-13 between another
two poles, when I test each of the three poles to the to the motor shaft I get nothing?

Is my OHM meter set correctly?

Also when I roll the chassis back on forth on track with no motor, it seems very smooth?

Thank you for your help!

ncng

Modeling Southern Pacific and Nevada County Narrow Gauge
Era 1937-1957 in 2 rail O Scale and On3. 

Rear most driver axle bearing is worn. Look for rub marks of the driver wheel against the frame. Two repairs are replacement of the bearings or using an e-clip or cut washer on the axle to keep the worm gear centered as mentioned above.  I've done the bearing replacement, it is involved and you would need a wheel press or making some other apparatus to press the wheels back on after pressing in new bearings.  I would just snap a washer on and call it good. 

UPDATE-MORE HELP NEEDED on Lionel 726:

I have removed rear drivers, with this done the motor and rear axle run perfectly, EXCEPT it
has become obvious, someone dropped her before and the rear axle is bent, also if I put my
fingers on both sides of the axle, it wiggles all over the place (worn bearings), when the direction
change the axle moves 1/8-3/16 inch side to side. How do I remove/replace rear axle without
damaging axle gear?

Thank you,

ncng

Modeling Southern Pacific and Nevada County Narrow Gauge
Era 1937-1957 in 2 rail O Scale and On3. 

Yup. Tap axle out straight as you can through the old bearings. The worm gear will come right off in the frame. Might as well order a new worm gear. When you press the new bearings on they don't get seated all the way home. Leave about  3/32" of it sticking out of the frame.  This will limit the side to side motion of the wheel/axle assembly . The new bearings will need to be drilled/reamed to the right diameter or the axles will fit way too tight. Pressing the bearings closes their inner diameter ever so slightly. A good 3/32" spacer is a large washer of that thickness. Place washer over bearing after you start pushing it into the hole. Seat till it stops and you have perfect spacing . 

Maybe a dumb question, because I've never attempted this repair myself.  But when you push the axle back through the frame, how do you insure that the worm wheel goes on square and centered?  Does someone sell a special spacer that's designed to hold the worm wheel in position for this part of the process?

Creep, coast, and pull.  We're not talking about cold fusion here.

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