Help with Kato/Atlas RS-1's and 3's

[peteski]

I think a skew wound motor would help. (?) Could one use a flywheeled  RS3 motor, remove them, and fit into older frame?
 Thanks,
 Joe D

There have been many word battles about straight-wound vs. skew-wound motors.  Yes, there is some advantage with skew-wound armature, but Kato still utilizes the same 5-pole straight-wound motor they used in those RS-3s, even in the most recent offerings.  They feel it is good enough.  In my experience, the number of poles (pun semi-intended  ) is more important than skewed armature. 

[joelm]

Thanks to all who responded. I plan to work on a couple of these over the weekend, and I'm hopeful of progress!

 A few things the conversation made me realize:

1) While the problem I described relates to single locos working alone, I may be mixing (MUing) the China and Japan units (not sure I considered this). Since one has a flywheel and one doesn't, there's likely to be a difference in operation. So that reminder is helpful.
2) I have broken these down before for cleaning and repair, and I have replaced the traction tire axles with all metal tread axles, and I have cleaned all the parts carefully. I have not polished the electrical contact parts, but will do so now.
3) I'll also check the axle slots for burrs and file away as needed.
4) Since two of these always run MU'd, I may permanently MU them. 
5) I will hold off on changing the decoders until I have done everything else. But that is an option.
Thanks again!

[Joetrain59]

I did clean and took a file to motor contact areas on frame halves. Result was a noticeable improvement, esp. at slower speeds.
 Joe D

[nkalanaga]

Peteski:  They didn't get the RS-3s.  The Minitrix units were nice running locos, but had been replaced with newer, better looking, Kato units.  Most of what they got was old freight cars and true junk locos, such as the early Mehano stuff.  The Minitrix units were part of the reason I put "junk" in quotes.  They were "junk" in that they weren't up to modern appearance standards, so had been relegated to storage in what amounted to a shed. 

I still have a set, with the flanges turned down to run on code 40 flextrak, and they run very nicely.  With the three wired together, they run smoother than two RS-3s.  One of these days I might dig them out, wire them to an Atlas track cleaning car, and build a real track cleaning train.  They certainly have the tractive effort for it.

[rrjim1]

The motor in these Kato made Atlas locos is a very good motor. Running at slow speeds is not an issue unless MUing with different locos.  If you are going to repower them, I would just replace them completely. The effort and expense really isn't worth it especially since the old shell fits on the new Atlas made chassis.

The Kato motor might be a good motor but it turns almost twice the RPMs at the same voltage as a scale speed motor. Seems like a waste to me to just throw them away when it would only be around $25 to get these old locos running great. They also pull much better that the new ones.

[mecgp7]

The Kato motor might be a good motor but it turns almost twice the RPMs at the same voltage as a scale speed motor. Seems like a waste to me to just throw them away when it would only be around $25 to get these old locos running great. They also pull much better that the new ones.

But it isn't a drop in fit. Major modifications to the frame would have to be done if you want flywheels. Even without flywheels, I think it takes frame modification. Then there is the drive shaft issues. It ain't easy. I thought about it, but in the end it was easier to take the $25 for a new motor and put it toward a flywheel equipped RS3 chassis. They can be found or I buy a complete loco for around $40. Sell the shell and sell the Kato chassis. It is a wash and depending on the roadname of the shell you can even make a few bucks.
That being said, I love the old Kato made RS chassis. I only swap chassis for MUing  purposes. I have a number of RS3/11s with the original chassis. Another trick is to swap out the trucks with Kato F unit trucks; the low friction ones with the bronze wipers. Truck side frames need to be changed.

[rrjim1]

But it isn't a drop in fit. Major modifications to the frame would have to be done if you want flywheels. Even without flywheels, I think it takes frame modification. Then there is the drive shaft issues. It ain't easy. I thought about it, but in the end it was easier to take the $25 for a new motor and put it toward a flywheel equipped RS3 chassis. They can be found or I buy a complete loco for around $40. Sell the shell and sell the Kato chassis. It is a wash and depending on the roadname of the shell you can even make a few bucks.
That being said, I love the old Kato made RS chassis. I only swap chassis for MUing  purposes. I have a number of RS3/11s with the original chassis. Another trick is to swap out the trucks with Kato F unit trucks; the low friction ones with the bronze wipers. Truck side frames need to be changed.

No modifications are needed when using a scale speed motor without flywheels. I don't see the need for flywheels and the new trucks or I would have parked my old ones and purchased all new. Were do you find the new version for $40, I could use a couple. 

[Carolina Northern]

I've had success putting a LifeLike/Walthers RS2 chassis under my RS-3's. This also makes them DCC ready.

Don

[mecgp7]

No modifications are needed when using a scale speed motor without flywheels. I don't see the need for flywheels and the new trucks or I would have parked my old ones and purchased all new. Were do you find the new version for $40, I could use a couple.

Cool that the motor is a fit without flywheels. Good to know. I have spare motors if I ever need to make the swap. I may try it just to see the difference. I used do the chassis/shell swap-o-rama using eBay all the time. You can get lucky with cheap locos/chassis. I just sold an Atlas Classic RS3 for $45.00. I wasn't happy, but someone got it for less than 50 bucks.
Don's idea to use LL units is a great one too. They are even cheaper than the Atlas.

[rrjim1]

I have spare motors if I ever need to make the swap. I may try it just to see the difference.

I still have two RS11s (same chassis as the RS3), with high speed motors, they do have the lower gear set from the U25B. With 12 volts regulated DC feeding my DCC system the one I tested starts at speed step #1 at 14 smph.  One of my RS11s with the lower gear set and a Atlas scale speed motor start at around 1 smph. Something I just found out was these old upgraded locos run almost exactly the same as my brand new Atlas RS3s, but the old ones pull much better.   

[mmyers]

The only trouble I have ever had with my Atlas?Kato RS3's is the truck to frame contact area. That design does not have the newer truck to brass wiper that most of today's engines use to transfer power from the wheels to the motor. Instead it depends on the truck contact rubbing the bottom of the frame halves. Cleaning and burnishing the contact area of the frames should get the engine running again like it did when new. Humps and bumps in the rails will also cause the trucks to have intermittent contact as there is little or no flex in the frame to truck contact. If it ran well on the layout previously the track work should not be an issue.You may have to do it again especially if the engine is not used frequently.
Martin Myers

[peteski]

installed U25 gearing, and replaced the old Kato high speed motor with a Atlas scale speed motor.

Are you talkign about the original Atlas/Kato trucks?  The ones which use metal gear case?  Could you provide some more details of exactly what was done (I don't own any U25s)?

In order to change the gear ratio of a pair of directly-coupled gears, one gear will have to get smaller (fewer teeth) while another will have increased diameter (more teeth).  The distance between the gear centers does remain the same.  But there could be clearance problem around the gear with increased diameter.  Or if the worm gear was the one with increased diameter, it would have to be located farther away from the worm.

In those trucks the worm gear (it is a double-gear) couples with the worm (the larger gear), and the smaller gear couples with idle gears which then couple with the gear on the wheel-sets.  Since the idler gears are involved, I don't  see an easy way to just replace some gears to change the gear ratio.  That's why I'm curious about how you did it.

[joelm]

Hey Guys: Fascinating discussion, mostly beyond my technical abilities at the moment. One question- why would it matter if the motor runs faster than necessary? (I'm thinking in a DCC world, you can control the top speed). Is this a DC issue? Thanks.

[peteski]

Hey Guys: Fascinating discussion, mostly beyond my technical abilities at the moment. One question- why would it matter if the motor runs faster than necessary? (I'm thinking in a DCC world, you can control the top speed). Is this a DC issue? Thanks.

We covered this recently in unrelated thread. See my post: https://www.therailwire.net/forum/index.php?topic=45529.msg589980#msg589980
Bottom line is: Higher gear ratio and/or lower motor rpms = more torque and smoother running quality at low speeds.

[rrjim1]

Are you talkign about the original Atlas/Kato trucks?  The ones which use metal gear case?  Could you provide some more details of exactly what was done (I don't own any U25s)?

In order to change the gear ratio of a pair of directly-coupled gears, one gear will have to get smaller (fewer teeth) while another will have increased diameter (more teeth).  The distance between the gear centers does remain the same.  But there could be clearance problem around the gear with increased diameter.  Or if the worm gear was the one with increased diameter, it would have to be located farther away from the worm.

In those trucks the worm gear (it is a double-gear) couples with the worm (the larger gear), and the smaller gear couples with idle gears which then couple with the gear on the wheel-sets.  Since the idler gears are involved, I don't  see an easy way to just replace some gears to change the gear ratio.  That's why I'm curious about how you did it.

The easy way is just to replace the complete truck, but after checking out the u25b truck design it was plain for me to see what was changed. Replace the Gear case/ with pins(9445011), 2-idlers(9445014) and drive gear(9445013. You also need to open the hole in the truck for the larger idler gears to clear. The Kato GP38 also used the same design and the gears were changed when the GP50 was released. Same can be done to the GP38 if one could find the parts.