Backwards Traveling Engine

[morrisf]

Dear Al,


I just now took your advice and rotated the motor as you suggested.

The unit now runs in the correct direction.

Thanks for the solution!


Morris

[TCWORLD]

I know this might sound daft, but has the shell on one of them been put on back to front (i dont know wheter they can be put on eitherway around or not, so i thought id ask).

[morrisf]

On straight DC, all engines should run in the same direction when on the same track, no matter which way the shell is on, or if it even has a shell or not.


In other words...

The mechanisms must all go the same way (follow each other as in a parade) on the same polarity; otherwise, there's something wrong with the wiring or the motor windings/terminals.

[TCWORLD]

IVe just noticed that you managed to flip the motor, which is good im glad youve got it working, i hadnt seen that before i made my last post.

Just as a side note the suggestion i made was valid, as the result of doing what i said would have meant that one of the locos mechanism/chassis would be on the rails in the opposite direction to before if you put the train on the track with so that the shell faced the same way as before (effectively flipping the chassis around under the shell,)

[James in FL]

TC,

It's polarity.
It matters not which way the shell is mounted.
It matters not which way the chassis is turned on the track.

The only way to reverse the direction of travel is to reverse the polarity to the motor.

In this case, the only way to reverse the polarity was to rotate the motor 180 degrees, not front to back, but rather roll it over.

You could have reversed the chassis on the track and reversed the body too...
They still would not run in the same direction.

; )

edit for spell check

[TCWORLD]

I understand what you are saying, but im pretty sure what im saying is correct, so ok bare with me, lets ignore the shell, and ignore that there are two trains for one second, in fact lets ignor there is a train altogether.
If you take any DC motor and connect it to a track where say the left rail is + and the right rail is -. The motor will go for wards when its + is connected to the left rail. If the + of the motor was connected to the right it would go in reverse. Basic motors, im certain you know that.
Right then the chassis of the train is basically the connections of the motor to the track (if you ignore the gearing as that isnt important). Lets say that the motor 'cannot' be rotated in the chassis, and at the moment its + is connected to the right side of the chassis. It will go bacwards like i said above. Now, in order to make it go forward, there are 3 options:
1: rotate the motor 180' that method works if you can rotate the motor, but what if you cant (which was the purpose of my original suggestion).
2: you can reverse the polarity of the track, but if there are two engines with motors connected opposite ways around, you cant.
and finally 3: if the chassis has two sides A and B. A is connected to the left, and B the right. The motor is fixed to these so that its + is joined to B (the tracks -). If you rotate the whole chassis around 180' then side B is now on the left and A the right. We know that B is connected to the motors + and now it is connected to the left rain of the track (the tracks +).
oh, now the motor turns forwards, and the chassis goes in the same direction as the second engine. finally, re-add the shell to the chassis, only putting it on the opposite way around to the way it was before. The locos go in the same directions when they are both pointing forwards in terms of how which way the shell is pointing not the chassis's.

Im sorrry that i went on for a bit then, but correct me if im wron about what ive just said (which an explanation to my suggestion earlier). If you think im wrong, I will go and recreate the problem with some locos and see if the solution works.
Thanks Tom.
(p.s. I know which the best method is which was the flipping of the motor, but i was just sharing an idea if it hadnt been possible to flip the motor)

[taz-of-boyds]

Sounds like there ain't no way.  As the other guys have posted:  as you turn the chassis around you end up with a double negative; 1, the gearing in the chassis is reversed, and 2, the polarity of the motor is reversed.  You noted the change in motor polarity, but did not realize the reversing of the gearing counts too.  The locomotive still runs opposite of the other locomotive.  So unlike my linguistic double negative, the two negatives on the loco do not accomplish the intended goal.  The motor leads need to change chassis-electrical pickup sides.  Or something like that...
Charles

[TCWORLD]

the gearing in the chassis is reversed

Good point. I have to admit i completely forgot to take into account the gearing :doh:
you are completely correct, now tats cleared up, im going to slowly back away and hide in a corner until everyone forgets i've just made a completly basic mistake