Help! 23140 Field Loco only running in reverse!

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Richard Clifton

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I recently bought an 'almost-new' 23140 Field Loco which had been pre-fitted with a 55022 MTS Decoder. I only have an Analog power source but the loco worked well, although it needed a relatively high setting on the controller before it would start to move. After several months of (infrequent) use it suddenly stopped working in the forward direction but still works fine in reverse. There is no noise at all from the motor when I try to run it forward but it sounds and run smoothly in reverse. Help!
 
Hello Richard,

The LGB Feldbahn loco's are quite 'delicate' compared to other LGB offerings, and it is easy to strain the mechanism..

It would need a higher setting, compared to analogue loco's, due to needing 5-6V to 'wake up' the electronics. - Analogue loco's tend to move at 2-3V.

I would guess that the drive-belt has stretched (possibly the gear on the driven axle is worn?) and there is just enough slop in the drive for the mechanism to lock-up in one direction.

You can (sometimes) get replacement axles from Marklin, but there is another way, though not for the faint-hearted!
Both axles have the worm-gear fitted on all the models I have worked on.
It is possible to swap the good gear to the driven axle. - You can't just swap the axles front to back, as the mountings for the rods are different.

This means you have to take the motor-block apart. - WARNING! there are tiny ball-bearings at the ends of the motor-shaft. Don't lose them.
You then have to remove one wheel and the good gear from the one axle. - Getting the wheel back on in exactly the right place.
Then remove a wheel and the worn gear from the other axle. Fit the new gear, then get that wheel back on in the right place.

Not easy, and you may well need to replace the drive-belt anyway (good practice).
Sometimes you may need to remove a wheel, and put it back on in a slightly different place, but usually moving the driven axle one-tooth one way or the other, will make the loco run more smoothly if it is a little jerky.

PhilP
 
PhilP said:
Hello Richard,

The LGB Feldbahn loco's are quite 'delicate' compared to other LGB offerings, and it is easy to strain the mechanism..

It would need a higher setting, compared to analogue loco's, due to needing 5-6V to 'wake up' the electronics. - Analogue loco's tend to move at 2-3V.

I would guess that the drive-belt has stretched (possibly the gear on the driven axle is worn?) and there is just enough slop in the drive for the mechanism to lock-up in one direction.

You can (sometimes) get replacement axles from Marklin, but there is another way, though not for the faint-hearted!
Both axles have the worm-gear fitted on all the models I have worked on.
It is possible to swap the good gear to the driven axle. - You can't just swap the axles front to back, as the mountings for the rods are different.

This means you have to take the motor-block apart. - WARNING! there are tiny ball-bearings at the ends of the motor-shaft. Don't lose them.
You then have to remove one wheel and the good gear from the one axle. - Getting the wheel back on in exactly the right place.
Then remove a wheel and the worn gear from the other axle. Fit the new gear, then get that wheel back on in the right place.

Not easy, and you may well need to replace the drive-belt anyway (good practice).
Sometimes you may need to remove a wheel, and put it back on in a slightly different place, but usually moving the driven axle one-tooth one way or the other, will make the loco run more smoothly if it is a little jerky.

PhilP
Click to expand...
Hello PhilP,

Thank you for your prompt reply. Yes, I had come across the use of the word 'delicate' in connection with the Feldbahn locos elsewhere on G Scale Central ! I was being careful (or so I thought) not to overload the pulling power of the loco - but obviously not careful enough!

I don't think that I would wish to undertake the corrective surgery that you describe just yet, at least whilst I still have the loco operating in reverse(!). It did occur to me that the decoder might itself be 'blocking' the forward motion but I guess that I was clutching at straws.

Thank you again for your advice - I will wait until I feel a bit more confident (or desperate) before attempting the repair!

Richard
 
The best way to eliminate the decoder is to unplug it & short it out. If its a faulty decoder it should run on dc both ways.
 
Hi Mike,

Thanks for your response. I did make one earlier (half-hearted) attempt to dismantle the loco and remove the decoder but I couldn't find any detailed schematics of the loco on the web. I will pluck-up courage and try again!

Richard
 
The decoder is normally just behind the front buffer beam. - Though I suppose Marklin might have moved it?

Only a couple of screws to get to it.

PhilP
 
Here you go :
IMG_20230820_112958.jpg
You can see the chewed-up gear at the top, a good gear at the bottom, and the two screws to get to where the decoder normally sits, either side of the gold sticker.
:nerd::)

PhilP
 
Hello PhilP and Mike,

Thank you both very much for your help and advice yesterday. I first followed Mike's suggestion to eliminate the decoder - which was located behind the front buffer beam, as per PhilP's photo. The loco now runs happily in both directions.

For my future reference: is it necessary to remove the five small screws from the bottom plate to separate the two halves of the motor assembly? I removed the three larger screws but my confidence faded at that point! The photo which PhilP sent of the chewed-up gear wheel is certainly worrying and I shall be doubly careful not to overload the Field Loco in the future!

regards,
Richard
 
Hi Richard,

(this from memory)
But yes, five screws to remove the bottom plate from the motor-block..

PhilP
 
Did I read somewhere that LGB in the US refused warranty claims on locos that had been used to haul more than two wagon?
 
PhilP said:
Here you go :
View attachment 323544
You can see the chewed-up gear at the top, a good gear at the bottom, and the two screws to get to where the decoder normally sits, either side of the gold sticker.
:nerd::)

PhilP
Click to expand...

I have two field locos, a diesel and the steam version. I run the diesel sparingly on my outdoor layout. I have only run the steam loco on a test track. It's been so long since I opened the bottom of the gearbox on the diesel that I don't recall seeing gears on both axles. Was that LGB's way of providing preventive maintenance ?
 
Madman said:
I have two field locos, a diesel and the steam version. I run the diesel sparingly on my outdoor layout. I have only run the steam loco on a test track. It's been so long since I opened the bottom of the gearbox on the diesel that I don't recall seeing gears on both axles. Was that LGB's way of providing preventive maintenance ?
Click to expand...
I can't comment on the diesel, but the several steam outline I have had to work on, have all had the gear on both axles.
BUT.... You can't just swap the axles, as the bosses for the motion are different lengths on each axle.

I think it is just 'easier' to have one axle (with gear) to pick in manufacture? - Less inventory, and less for the production line to get wrong.

PhilP
 
One of the Malletts that I bought s/h had a idler gear chewed up like that in the front and an idler gear for a different locomotive in the rear truck. :rolleyes:

The gears in that are readily available and the seller agreed to pay for the parts so it was an easy fix.

For your one it looks like they sell a quartered assembly to replace that. Obs check it's rihgt before you buy. ;)

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Hello Craig,

Thank you very much for your reply. I have looked at the website that you mentioned, which appears to be a 'treasure-trove' of LGB spares. I may well order one of the axle assemblies that you spot-lighted, just as a precaution for the future, although at the moment the Loco is operating OK - albeit in Analogue mode only - as I will explain.

My original Post resulted in a number of ideas and pieces of advice. I took the simplest of these; to remove (or, at least, short-out) the decoder. As I have (still) not committed to going fully Digital this was - and has been - a suitable compromise. As the Loco runs smoothly in both directions in Analogue mode, I am, for the moment, content.

Due to external time pressures, I have to admit to having 'parked' any further investigation of the original issue. If and when I can report a proper resolution of the problem, then I will update this thread accordingly. In the meantime, thank you again for your interest and advice.

regards,
Richard
 
Richard Clifton said:
My original Post resulted in a number of ideas and pieces of advice. I took the simplest of these; to remove (or, at least, short-out) the decoder. As I have (still) not committed to going fully Digital this was - and has been - a suitable compromise. As the Loco runs smoothly in both directions in Analogue mode, I am, for the moment, content.
Click to expand...
Late to the show as usual but could that be a dodgy decoder if the loco is okay without it? Before buying a new decoder if you decide to go DCC do you have anyone who could test the current decoder for you? If so you will be able to tell if that particular decoder is fit for recycling or if the decoder is okay then leave the loco as analogue only.
 
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