# Different wheel speeds in one engine.



## lightningmcnulty (Jan 4, 2015)

Hey guys.

Sorry my first post is a question but I didn't expect to run into issues so quickly.

Yesterday I got a kato n Scale loco, its the sd7 

I have a little experience with ho but since space is an issue I wanted to try n gauge.

I ran the train for the first time and it seemed like it was dragging or wheelspinning somehow, I assumed I was doing something wrong but on further investigation the front set of wheels are running at a vastly different speed than the rear.

I opened the train up (first time for me) and it looks like there are clutch/drag mechanisms on the motor outputs probably to prevent motor burn out but I guess one of them is too loose.

Is this a common issue and what is the solution.

Thanks for your help

Kim


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## Bone1977 (Jan 17, 2014)

If it was purchased new you can take it back and do an exchange, they should do it. No that is not normal. Someone else may know the fix as I'm not very mechanically inclined in that regard, but if it is new that is a problem and could be lead to other issues.


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## Brakeman Jake (Mar 8, 2009)

I've owned a few Kato N scale diesels and I've never seen any type of clutch or slip device.I'd say one of the drive shafts is stripped where it meets with its flywheel.Could you post a pic?


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## lightningmcnulty (Jan 4, 2015)

Here are the pictures, hopefully it makes sense.

The brass bit is a receiver for the plastic knuckle and inside the brass bit is a t piece that engages the knuckle.

Both of the t pieces are free to spin but one of them is much freer than the other.

any ideas

thanks 

Kim


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## lightningmcnulty (Jan 4, 2015)

sorry, to reply to your comment, I could return it but it was reduced greatly so i'd loose the deal, i'd rather fix it if possible.

thanks 

Kim


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## wvgca (Jan 21, 2013)

the drive inserts in the flywheels are supposed to be a snug fit, and should not spin easily, actually should not spin at all... they are not [imo] designed as slip clutches...an ideal repair would be to replace both of them, however the diagrams i found do not show that part available seperately, just with the motor, so i would just pull them out and use something like aileens tacky glue, or ca ..that might have been the reason it was on the reduced list... relatively easy fix ...


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## Brakeman Jake (Mar 8, 2009)

I second this...motors don't need any torque limiting device.The wheels will spin way before the motor could ever be overloaded.


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## DonR (Oct 18, 2012)

Not familiar with that Loco. My locos use a 'dog bone'
drive shaft with 2 nubs at each end that engage a slot
inside the fly wheels.

I couldn't see inside the shaft area of your flywheels, but
the pic of the shaft with a slot would indicate to me
that there should be some cross piece inside the flywheel
that would engage the slot, thus creating a slip proof
connection. Is that piece missing or broken?

While you have the loco apart you should be able to test
this easily by inserting the shaft into the flywheels and
turning gently. 

Don

Don


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## lightningmcnulty (Jan 4, 2015)

Great guys, I have glued the pieces you mentioned and everything seems to work well now, thank you.

I do have another question, whats the best (value) dcc decoder to fit to this engine?

thanks 

Kim


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## Cycleops (Dec 6, 2014)

I would advise you not to buy the cheapest decoder you can, they may be older ones which do not have the up to date features, for instance you may not get 128 speed step motor control. I have just put a Digitrax one in a Kato diesel and it's great. Any of the premium makes like TCS, EsU or NCE will be fine. If your Kato chassis is the same as mine replacement is a very simple matter. The old one slids out and the new one slips in., the clips from the board are retained for soldering to the new one. Just make sure the clips don't touch the chassis which is live, and put some Kapton tape under the new board in case it makes contact with the chassis ( some have it in place already). Good luck.


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## lightningmcnulty (Jan 4, 2015)

Awesome, I just brought a digitrax one.

thanks for everything guys 

Kim


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## lightningmcnulty (Jan 4, 2015)

on further inspection I found that the front truck assembly is running poorly, it seems like one of the gears is damaged and that is what took out the drive knuckle.

I just spoke with steve at atlas (i know I said kato earlier, my mistake forgive me i'm new!!) and he is sending me a new truck assembly and the drive knuckle. 

thanks for everything guys 

Kim


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## Big Ed (Jun 16, 2009)

Was it new when you bought it? :dunno:


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## lightningmcnulty (Jan 4, 2015)

yeah it was but i'd guess it had been on the shelf a while because it was discounted by about 50%


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## Cycleops (Dec 6, 2014)

If it's an Atlas they're a bit more challenging to fit the decoder. I'd advise looking at the instructions on the PDFs you can download from their website, the pics are are clearer than the printed ones.


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## lightningmcnulty (Jan 4, 2015)

Ok I will, thank you


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## Fire21 (Mar 9, 2014)

The Kapton tape that cycleops refers to is a special insulating tape that is needed when installing a decoder in the loco. I searched electric suppliers and couldn't find any. So I went online. Here is a link that has very well-priced rolls. You will want the ¼-inch stuff. One roll will last your lifetime.

I used it on my Kato PA locos.

http://www.kaptontape.com/1_Mil_Kapton_Tapes.php


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## lightningmcnulty (Jan 4, 2015)

great, I will order some, which pieces do you need to isolate? I think I brought a direct replacement piece to go into my loco?!


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