Need help in finding a bind in Lionel 726 rr

Two things to look for in the old Lionel steamers. Usually if the drivers are out of quarter it will bind in both direction.   When going from forward to reverse the armature will move in and out (fore and aft in the frame) If you leave thrust bearings/washers out it can bind up in one direction or the other.  Some time the smoke unit linkage will cause binding but that usually occurs in both directions also.   j

FYI - thought I would post 681-100 motor diagram form Service Manual (from Olsen's library) in case you needed it. Marked thrust wshers @JohnActon mentioned in his post.

Thanks for your suggestions. I do have that diagram in my Greenberg Repair Manual. I did not disassemble the motor that far to observe the thrust washers, etc. but I may have to. Since it moves freely in both directions with the motor out I don't think it is either in the valve gear/side rods or smoke mechanism. My guess is it's the play in the armature.

John

The motor is geared to the last axle through a reversible worm and worm wheel.  Power is transmitted to the other axles through the drive rods.  After a period of time, the bearings that hold the rear axle in the chassis tend to wear in an oval pattern.  If one side of the axle can move back and forth, it subtly changes the spacing of the driving wheels, causing the rods to bind in operation.  Axle movement may also allow a wheel to rub on the chassis, or on an adjacent wheel.  Unfortunately replacing the worn bearings is a difficult repair.

The Lionel service manual advises folks to let the engine "run in" for a while after motor or worm wheel replacement, to help eliminate any tight spots.  Personally I question this advice (and a lot of other things about the post-1946 redesign of the Berkshire!)  Many people love them, but for mechanical reliability I would rather have a 773, or even a spur-gear driven 2046.

Sometimes there’s shims under the motor....I believe even the factory shimmed some of them and repair shops certainly would shim them chasing a binding problem....I think there’s an old TSB from Lionel about this???.......I’ll let Ted or John chime in on that....it’s been a long time since I messed with a Berk....seems though I recall adding or subtracting shims on some of them to get the pitch just right........Pat

My money is on the rear drivers. one or the other is rubbing the frame. Caused by wear of the axle bushing. Also check that the worm wheel gear is not rubbing the inside of the casting. Pretty much what Ted S. said. You can pull the driver that is binding and add a thin spacer washer that should pull the drive wheel away from the frame. Or you can go head-on and replace the axle bushings.

Wondering if you pull the motor and useing alligator clips run the motor by itself in reverse for a while varying the speed and see how it responds. Perhaps that may narrow it down some if motor run by itself runs fine varying the voltage to it.

There are great suggestions here in thread .Please let us know what you find as it may help others.

Chuck Sartor posted:

My money is on the rear drivers. one or the other is rubbing the frame. Caused by wear of the axle bushing. Also check that the worm wheel gear is not rubbing the inside of the casting. Pretty much what Ted S. said. You can pull the driver that is binding and add a thin spacer washer that should pull the drive wheel away from the frame. Or you can go head-on and replace the axle bushings.

This is what I typically find.  The side thrust on the worm driven gear drives the back of the wheel into the frame.  The back of the wheel may be shiney from rubbing on the frame.

Pulling wheels and replacing these bearings is a difficult repair best left to experienced techs with the proper tools (a puller and an arbor press with the proper wheel cups.)  Because power is transmitted to the other axles exclusively through the side rods, re-installing the wheels "in quarter" (i.e., 90 degrees out from the wheel on the opposite side of the axle)  is critical to smooth operation.  The service manual does refer to shimming the motor.  But if your loco ever ran OK without the shims, it shouldn't need them now.  Most likely it's a worn bearing and the axle has too much play to permit smooth operation in reverse.

If you're going to do postwar restorations a service manual is a great investment.  But in the meantime have a look at the section on the 736 (same as yours but with MagneTraction) in the Olsen Toy Trains Service library:  http://pictures.olsenstoy.com/cd/locos/loc736p1.pdf

Hope this helps!

This is kind of a long shot but if the rear wheels are indeed rubbing on the chassis you may limit the side play with a couple of washers made out of a plastic jug such as a gallon antifreeze jug.  I like the fact that they have a nice flat area to cut the washers from. I like to make jug washers on my drill press.  I will find brass tubing the size of the hole in the middle, cut a section of it about three inches long chuck it in the press and turn it on, hold a jewelers file against the bottom and bring it to an edge it won't matter if it is a little rough on the bottom it will cut a nice clean hole in a stack of plastic from your jug.   I usually tape several layers of plastic to a board and clamp the board down on the drill press, cut the center hole then find a piece of copper pipe the diameter I want the outside and do the same procedure I used for the center hole.  The heat of cutting through the stack will fuse the layers together but you can pick them apart with a knife.  Now you cut through one side of your washer so that it can spread around the axle on your loco. If you have a fat axle you can make two cuts to form a C clip. You might want to put one of these on each side of the drive axle to center the worm wheel.  One quart oil jugs also work well and are thinner a combination of thick and thin or whatever you need to center it up and yet turn free. If indeed the rear drive axle is rubbing on the frame casting. There was a discussion on the forum about plastic spacer washers for axles on a couple of other occasions and I posted some photos of the smaller plastic washers I made using the brass tubing technique.    j

Or use some 671M-23 thrust washers.

Thanks Chuck,

I may pull the motor shaft and replace all the thrust washers (if they are all there) and even the bearings there. I am fairly sure the bind is in the worm/worm gear.

John

No, I didn't make myself clear. Nothing to do with the motor. You need to determine if the left or right rear wheel is rubbing on the frame, then you are going to half to pull the wheel off the axle and add a shim washer to the axle then replace the driver in the frame. This isn't a project that the average hobbest has the tools for. If the problem persists after you have tried the other suggestions, should take or send it in to a competent repair shop. 

The wheels are not rubbing. The bind is in the area of the worm gear and worm wheel. 

I had the same problem with one of my 736's.  Ran in reverse fine but had a bind going forward.  Drove me nuts for a while.  Then I found that the worm gear was a little off center and the worm would catch on the edge of the gear.  I moved it over a smidge (technical term) to where it was centered and have not had a problem since. Good luck with it.

Orrin,

Can you please describe the steps you used in "moved it over a smidge". That gear is awfully tight on the axle in mine. it does move from side to side as you change directions and binds when I put it in reverse. 

John 

Because the axles move slightly left to right or right to left, I put a wedge on one side of the worm gear and used a punch and hammer to drive the axle into it a little at a time. Maybe a 32nd of and inch at a time.  Call me tonight when I am home and I will try to walk you through it.  Number is in my profile.

Someone asked that I post the solution I found so here goes. It uses ideas from various posts and is very simple. When the engine went into reverse, the side thrust pushed the gear to the left side and caused binding with the worm and, as many suggested, put the right driver against the frame which added to the problem. The wheel didn't show excessive wear and wan't really shiny so I believe the main problem was in the gear/worm area. I don't have the tools to pull wheels so I took a small steel washer -- about the size that a 3/16" bolt would go through and cut a "gap" in it that would just allow it to slip over the axle beside the main gear inside the frame. It turns with the wheel but there is not enough room in the bottom of the frame for it to fall off. I discovered pretty quickly that it would take another washer to mostly fill the gap between the gear and the frame so I put in a second washer and it now seems to run well.  Thanks to all for your suggestions!

JThut

I am glad that you got it solved.  Thanks for letting us know.