loco runs fine in cradle, not on track

[Frankv]

A friend gave me a used f7 loco which he said ran fine when last used. It has all metal wheels, a can motor driving rear truck w/2 axles. It runs fine in a cradle no matter how power is applied. The powered truck turns over fine with one set of axles lifted off the track - doesn't matter which set, but not with all 4 axles on the track - no hum, no lights, no response to slight push. Any thoughts?

[pdlethbridge]

Is the front truck on backwards?

[Frankv]

Thanks for your response. The front truck does not appear to have any orientation.  Anyway, it is not powered, so why would it matter?

[simkon]

There could be something in the way/ obstructing it, or a problem with the contacts.

[Jim Banner]

I believe pd is right on the money.  You tell us the motor runs with either set of axles off the tracks.  To us this means one thing - both the front axles and the back axles pick up power from the track.  It does not matter that the front axles are not driven.  If, as pd suggests, the front truck is on backwards, then the front wheels that are supposed to pick up power from the left rail are picking up from the right rail instead.  But these wheels are connected to to the left rail by the other truck.  BINGO!  A dead short circuit.  Same for other four wheels.  Another short circuit.  No wonder the motor and the lights don't want to work - all the power is flowing through the short circuits.

Jim

[Frankv]

Congratulations to PD and Jim Banner - I reversed the front truck and IT RUNS!! That leaves me free to work on the other problem - a horrible grinding of gears in the powered truck, which I noticed while struggling with the failure to run on the track. I'll leave that for another day. Thanks guys for all the help.
I'm beginning to think my "friend" who gave me this loco is not really a friend.

[RAM]

Jim let me correct you on one thing.  If it picked up current on one side of the powered truck and on the side on the nonpowered truck.  If you turned the nonpowered truck around you would not have a short.  You can't have a short if you are only picking up current from one rail.  It just would not run, as was the this case.

[Jim Banner]

RAM,
If the locomotive in question were picking up from one rail at the front and the other rail at the back, what you say would be true.  But it is picking up from both rails at the front and both rails at the back.  Careful reading of Frankv's initial post says:

The powered truck turns over fine with one set of axles lifted off the track - doesn't matter which set

For it to run with one set of axles i.e. one truck off the rails, it must be picking up from both rails on the other truck.  And since it did not matter which truck he lifted off the rails, both trucks had to be picking up from both rails.  If you are still confused, let me know and I will draw you a diagram.

Now here is another thought for you, and for Frankv.  At one time, Bachmann did produce some locomotives that had a power truck at one end and a pickup truck at the other end.  Each truck picked up from one rail only.  The fact that the locomotive in question picks up from both rails on both trucks makes me wonder if it also is supposed to be driving all four axles.  If this were the case, then the grinding noise it makes could be a stalled truck being pushed along the rails.  This can happen when one drive shaft break, or when the flywheel on one end of the motor or the worm gear on top of one truck slips on its shaft.  Perhaps it is time to open up that locomotive and see what is going on inside.  If there is a motor in the middle of the locomotive, then it should be driving both trucks.  But if the motor is sitting right over one truck and swivels along with that truck, then that is the power truck and the other truck just free wheels.  If the motor is in the middle, take a close look and see why it is not driving both trucks.

Jim

[Frankv]

Gee, this is getting interesting - I'm learning a lot, thanks guys. The rear (powered) truck has a can motor. The front truck (the one I just reversed) has only wires and a post, and its wheels turn freely. In the cradle, electricity applied across only the wheels of the front truck will cause only the rear wheels to spin. Applied across only the wheels of the rear truck also causes only the rear wheels to spin. Front truck is definitely not powered, just picks up electricity from both rails. Gear noise is present when running in the cradle and comes from the rear truck. Any ideas on the gear noise? Thanks again.

[Jim Banner]

Frank,
Is the can motor mounted horizontal or vertical?
Jim

[robman]

Hi. I've just come upon  this thread and would you believe it, I have just yesterday been given a very old Bachmann loco from my brother in law to fix with what appeared to be the same problem you're encountering. First off, it only has one power truck at one end and a free wheeling truck for power pick up at the other. The powered truck does not (in this case) pick up power. The motor sits above the truck and is what I would call from my slot car days a side winder,armature across the frame. To try and get this beast to run I first did a circuit test and found that the black wire onto the pickup truck was broken, fixed that,cleaned the wheels, lubed it and got it going and what a noise. Tracked it down to a lot of use in the past and not too much future to look forward to. I don't presume you can buy gears or parts for it so I'll just park it back at his place.Cheers Rob.

[Frankv]

Jim Banner, The  motor is mounted vertically; that is, I can see the armature spinning around a pole which is perpendicular to the plane of the track. This loco isn't very old, judging by its shiny paint and general lack of wear and tear. If the noise is due to gear problems they aren't slowing it down - it is a speed demon, roaring around my layout and threatening to derail at half throttle.

[Hellhound]

I have several of those older Bachmann locomotives with one truck driven by a 3 pole pancake motor and electrical pickup on both trucks. They are all sitting on a display shelf now since they are dead or no longer run reliably. In my experience they run good for a short time when new then the gears start to go bad or the drive gears start to slip on the axles. The plastic gears will also split. Another problem with those older locos is that they have rubber drive tires on the drive truck wheels to compensate for the fact that they are too light to get good traction on just one drive truck. I have seen anywhere from one wheel with a drive tire to all four. The life span of these rubber tires can be anywhere from years to about a half hour. They will stretch and spin off or get brittle and crack with age. When the drive tires are gone they have no traction and since there are grooves in the wheels for the tires, they are going to derail, if they can move at all. Some old Tycho locomotives also used the same type of drive with plastic wheels and rubber tires on one side of the drive truck. Lifelike still uses that design since I recently purchased a new Lifelike locomotive online that has the one truck drive with rubber drive tires....I wonder how long before that one gets parked on the dead line. ...I try to avoid locos that use that design as they are nothing but trouble. They have a short lifespan and will wind up being used as scenery... or sitting on a shelf in a static display.

[Frankv]

Thank you Hellhound.  Your description fits this loco perfectly - it has traction tires on one axle of the drive truck. I'll run it til it stops or the noise gets unbearable, then on to the scenery siding. In the future I believe I'll adopt your thinking and avoid locos with this design.

[Jim Banner]

Frankv,
the only locomotive I recall as having a vertical motor was an AHM C-liner.  AHM, alas, is not longer with us, and fortunately, that particular locomotive design is gone too.  I believe they came out in the 1960's and ran with much sound and fury.  Unfortunately, their large motor equated to small pulling power.  And the metal gears in the early ones sounded like they were worn out, right from day one.    I still have one of these, long since repowered with an Athearn mechanism.  It hasn't seen much action since the Proto 1000 C-liners came out, but for a long time, it was the only model of a C-liner outside of brass.

Jim