Kato SD40-2 motor problem
#1
Hi Guys...

I've got an Nscale SD40-2 made by Kato with a rear truck that doesn't work. Let me explain...

Both front and rear wheels turn (in fwd or reverse) as long as the front truck is conducting power and touching the rails. As soon as I remove the front truck wheel set from the rails, the rear truck wheels won't turn and the rear light doesn't illuminate. I noticed this when I was trying to clean the wheels...I could clean the rear wheels on a cleaning cloth when I allowed the front trucks to rest on the rails and conduct the electricity to the motor, but when I tried to clean the front truck wheel set, the rear set didn't seem to conduct the electricity. Has anyone else noticed this on this particular engine?

I'm going to pop the shell off today and try to see if there's an obvious problem...I've already checked the wheel gauge (all the wheels were gauged properly) and if the metal conducting strips were making contact with the wheel axle point (they seem to be). I'm no motor expert, but it seems strange that the rear wheels would work only with the front truck picking up the power from the rails. I don't have any other engine like this where only one truck operates as long as the front truck is making rail contact. The rear light illuminates and the rear wheel set turns just fine (when in reverse of course) as long as the front truck is on the rails. And when the front truck is making contact with the motor running in "forward", the front light illuminates and both front and rear wheel sets turn normally.

Any ideas?

I've already tried to properly explain this condition to whomever is reading the email at Kato...but haven't heard a reply yet...so I thought I'd seek the expert advice here!
Mark

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#2
Hi Herc Driver,

I have several Kato N scale SD40's and havnt found this problem but a few ideas pop the body off and look at the contact strips running along the chassis make sure they are contacting the chassis along its length and remove them for a good clean especially on the area where the strip touches the truck pick up the best way i find is to use a glass fibre stick on the strips it cleans the gung off well ..... though do this outside and away from your clothes otherwise the fibres will itch...... blow any bits off and do the same with the truck pick ups where they meet the strip while your at it give the wheels a good clean with the stick as well reassemble the chassis and trucks without thr motor and see that the drives are connecting with the trucks, now replace the strips and bend them down a little tomake sure they contact the trucks reassemble and try the loco.

If its on DCC check the track red/black wires for any dry solder joints though if it is picking from the front truck they should be ok.

Lets us know how you go on ......... good luck Big Grin
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#3
Good ideas and I'll try them. This is a straight-DC engine for now. As far as I can tell, the electrical strips are touching correctly...but it's a challange to prove that's true even with a light and magnifying glass to see the small parts. It seems strange that power will run to the rear wheel set with the front trucks on the track (which should prove the motor turns both front and rear trucks). The engine has never been dropped (at least not while I've owned it). So I'll pop off the shell and see if there's anything not touching that should be to properly conduct the electricity. It pulls fine, and if I didn't get the idea to clean the wheels, I wouldn't have noticed there was a problem.
Mark

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Lt Colonel, USAF (Retired)
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#4
Be careful when cleaning these metal contact strips. They bend very easy. I would try using the eraser of a pencil to clean the strips. It will polish the contact strips without putting any scratches in them. Also be careful with any bends that you make, to much pressure on contact points of the truck will cause problems too. These strips are very fragile.
It sounds to me that the rear truck is not making good contact to these strips. There for, there is no power getting to the motor via the rear wheels.
When you pick up the front truck assy from the rails the motor stops working. Is the the case?
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#5
Yep, that's the case. To me the easiest explanation is the rear truck is not allowing the power to flow from the rails to the motor via the metal conductive strips. As far as I can tell, when the engine is on the tracks, the metal strips are touching the points of the contactor. The rear truck is also seated correctly. (This is the new Kato "snap in" truck assembly.) The engine isn't very old and spends its time inside the protective box. So it doesn't face the heat/humidity/cold like something just remaining on the layout all day would. But just in case, I'm going to clean the metal strips. I'm going to figure this out, probably by process of elimination, as soon as I get back home in a few days. Thanks for everyone's ideas to fix this problem...I really appreciate it.
Mark

Citation Latitude Captain
--and--
Lt Colonel, USAF (Retired)
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#6
Those strips are very touchey. Too much spring pressure from the contact strip to the truck and it will raise the truck away from the frame, too little pressure and no electrical contact. You might try using a conductive cleaner on these contact points. There is a very good product made by Areo-Lube ( I think I have that right). It is a cleaner and contact lube, works very well, I use it every day when doing DCC installs. If you need more info about it I can find you a link to a site where you can get it.
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#7
Thank you!

I wrote Kato about this and received a reply that really didn't help too much. They suggested dirty wheels are the problem or dirt on the track. Well, the wheels are definetly not dirty and the track was just cleaned, so I doubt either of those suggestions are plausible. I'm thinking it's more likely a bad electrical contact with the rear truck assembly. That's where I'll start to try and figure this out.
Mark

Citation Latitude Captain
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Lt Colonel, USAF (Retired)
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#8
Hi Herc Driver,

If you have tried the methods of cleaning suggested and still no success take the rear truck just to be sure wipe the track and put it on get a voltmeter and measure the voltage to the rails then measure the voltage to the top of the truck pickups, they should be the same or very near.

If not you have a problem within the truck even factory out of the box locos can have crud in there, another question are the wheels blackened finished if so make sure the black is removed where the wheel touches the track in the flange with any new loco i run it in on a loco tester rolling road for half an hour each direction on DC quarter throttle, it usually gets rid of the blackening on the flange essential if the loco is to be converted to DCC as contact is important.

Also it beds in the gears and results in a smoother running loco good practice for DC/DCC you may find this is the problem though the wheels are clean a film of the blackening is stopping current reaching the truck pick ups.
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#9
What sort of warranty does Kato offer, and how much can you work on the model before you void the warranty? It sounds like this is a relatively new model with very little use. It might be better to see if they will look at it if you send it back to Kato. I think it is typical for most companies to presume that the problem is dirty wheels or track since that eliminates them from fault, but they may say that because they would rather you didn't take the model apart and risk doing damage that would be difficult to repair.
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#10
Their warrenty is a good one I guess (although I have never needed to use it before). I've been getting a few emails from the staff at Kato encouraging me to open it up and look at it to see what's going on in there. I just got home, so when I get the time, I'll remove the shell and really see what I can figure out...why it won't carry power from the rear trucks to the motor. Should be simple enough...(famous last words).
Mark

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Lt Colonel, USAF (Retired)
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