I have a 25+ year old Sunset Third Rail (2 rail) PRR 2-10-4 J1 whose drive trained failed during an NMRA open house Saturday.   Until the incident the J1 was a smooth running locomotive - but then it started slipping/skipping at one point in the rotation of the drivers..  After disassembling the drive train  I found that the brass axel gear on #3 driver was worn to the point of not meshing with the steel worm gear.  (Note this was a very early Sunset 3rd Rail model and they subsequently redesigned their drive train).  I was aware about issues with steel worms driving brass gears but had put off upgrading the drive train due to the press of higher priority modelling projects.    

My plan is to replace the original gearbox  with a North West Short Line 23:1 Mod.6 ball bearing idler gearbox (part # 654-6) and "495-6 coupling set. Changing the gearbox will require pulling the driver and worn gear, pressing on the new gear and pressing the driver back on (in quarter).  The existing motor mount will need modification to accommodate the new drive shaft alignment.    My biggest concern was getting parts as I read the following NWSL notice:

After 60 years in business, NWSL will cease operations effective August 30th, 2019. The company will continue to take orders for in-stock products until July 1st, 2019. Closure is for personal reasons and sale of the business is not anticipated, although reasonable proposals will be considered.

I called NWSL today to place my parts order and spoke with Nick.    While it will take a month or so, he did agree to fill the order.  I post this as a heads up to other owners of Sunset J1's (2 and 3 rail) - do not delay in ordering NWSL parts if you want to do a similar upgrade.  

Ed Rappe           PRRT&HS 421

Original Post

I'm glad you were able to obtain another gearbox.  Yours is not the first Sunset "Texas" type that I've heard of with a gear failure.  I just wanted folks to be aware that this loco (the PRR J1) predates Sunset's current "Quiet Drive" arrangement, consisting of a carbon-fiber belt and a layshaft mounted low in the frame.  I believe their design and materials have improved since the J1 era, so no one should avoid their excellent products made during the 21st century because of concerns about drive failure.

Creep, coast, and pull.  We're not talking about cold fusion here.

Buying a business with a very limited market is a risky proposition.  Even if you get the tooling and some parts for free, the profit hardly covers your efforts.

Call Sunset first.  They stocked some bronze replacement gears, which enabes you to simply replace the axle gear and keep on keeping on.

The NWSL owners are/were very nice folks.  The plastic mod 0.6 gearbox needs some work.  The original dies were set up for reinforced plastic; the newer boxes were a different material and did not quite fit due to distortion.

Use a #J drill and some fine sand paper on those, making sure that the axle bearings fully fit in the assembled box.

I really miss the mod 0.6 - it is all I used at the end.  Now most of my locomotives remain unpowered.   That's ok; I can only run four at a time, and I am well over a hundred powered locomotives.

@bob2 with apologies to Ed because I'm getting a bit off-topic.  But if I wanted to buy an NWSL gearbox in the aftermarket, how could I tell whether it's an "old" or "new" one?  Also, how do these NWSL gearboxes compare to US Hobbies gearboxes?  Thanks!

Creep, coast, and pull.  We're not talking about cold fusion here.

I guess I'm one of the lucky ones, I have a petty good stash of NWSL gearboxes and parts.  I bought a bunch when Raoul sold the company to Dave & Lynda.  I always keep an eye out for their products when I attend the few shows I can make.  Instead of looking at all the shiny things I look through the junk boxes.  As an example, at OSW I found a guy selling NWSL axle sets (33" & 40") along with four or five gearboxes.  I did buy one shiny thing but I bought all the NWSL stuff he had.

I can't speak for Bob but, I'll take all the USH gearboxes I can find if nothing else than for parts.  Again, I'm lucky, I have a decent supply of them also.  I'll buy them just for parts, if I can.  Maybe this is a case of making my own luck, as they say.

I would think, anything from Seattle would be fine.  Having said that, just last week I installed a .5 mod gearbox, from Seattle, in an old Kemtron Mogul and found the holes for the retainer were missing in the bottom of the case.  Easy to fix but even the products from Seattle weren't always perfect.


Thanks to a search by Matt Forsyth I was able to purchase a "Seattle built" NWSL 654-6 23:1 ratio 5mm axel gearbox for my Sunset J1.  I just completed installation and thought some may be interested in learning how I went about the project.  


  The first photo shows the OEM gearbox.  Note that it used a 4 spur gear tower to drop the horizontal drive train down to the driver axel gearbox.  The second photo shows the badly worn brass axel gear after it was removed from the axel.  

Sunset J1 gearbox


  I don't have a quartering jig so before I pulled the un-insulated  driver off the axel I scribed a line across the hub of the driver and the end of the axel to indicate their in-quarter relationship.   I used an assortment of common shop tools, and a piece of bar stock (slotted to go over the 5mm axel behind the driver)  to press the uninsulated driver off the axel.  A gear puller was use to pull off the worn out axel gear.   The new NWSL gearbox bearings, drive gear, and right side frame bearing were then pressed on the Sunset axel.  I found that the Sunset axel was slightly knurled at it's center (for the drive gear) and on its ends  (for the driver faces)  so some gentle force was necessary to press the parts into position.  The most critical task was pressing the driver face back on the axel in an orientation that aligned the scribed line segments.  The press was done using an inexpensive Harbor Freight bench press.  Washers were temporarily stuck to the centers of both drivers (with grease) so that the press was parallel on both driver faces (no contact with the tires or counterweights).  I made the press in small steps checking progress with a NMRA wheel gauge as I went.  Before mounting the gearbox on the axel I temporarily reinstalled the driver (and main rods) in the mechanism to make sure there was no bind or wobble.  Good fortune - no problems .  The NWSL gearbox was slightly larger than the Sunset one and required enlarging the opening in the one piece driver bearing retainer plate (I used a file).   A NWSL 495-6 universal joint kit was used to connect Pittman's 5/16" motor shaft to the 1/8" NWSL gearbox shaft.  Per NWSL instructions "D" shaped flats were filed on the ends of the shafts enabling the sets'  horned balls and slotted cups to be pressed on with no possibility of slippage.  The new drive shaft setup slopes downward so I had to fabricated a  short front motor mount.  I was able to reuse the rear half of the original Sunset motor mount by bending it to the proper angle.  To keep the gearbox from rocking for and aft (from drive train torque) I screwed a pair of brass flat stock restraining bars  to the upper face of the frame.   Overall it was an interesting project that took approximately 8 hours.  The best part is that the model now runs smoother and quieter than when it was new.  


PS - The gearbox I used was an older one made in Seattle.  Like Jay I discovered that the gearbox halves were not drilled and tapped for the cover plate screws.  Rather than waiting for a replacement I just drilled and tapped the gearbox halves using the holes in the cover plate as a guide. 





Ed Rappe           PRRT&HS 421


Photos (4)

I would have done one thing differently.  I would have very carefully soldered an extension on that worm shaft, lengthening it all the way back to the motor shaft, with 1/16" clearance.  A piece of Toyota #0 hose would connect motor and shaft.

That would eliminate noise from the horney balls, but even better, it would have eliminated chatter noise between the gearbox and the brass rotation restrictors.  The radial force on the hose and motor would be negligible, given that extremely long lever arm.  The ball bearings would resist rotation of the gearbox noiselessly.

I agree with Bob.  I just finished these two USH 0-8-0s and though the photos don't show it I replaced the 4mm shaft with as long a piece as I could and got it as close to the motor as possible (in this case about 1/16").  Running low on Toyota tubing so I went to the local auto parts store and bought 3 different sized pieces of heavy wall windshield washer tubing.  Works well.   I still use other means of coupling but for these, I think the tubing was the right way to go.  I still use the KTM gearboxes but I install ball bearings on the input shaft.  Motors were Faulhabers. The last photo shows one of the new input shafts prior to installation.  The old shafts are in the top of the photo.  I do exactly the same thing with the NWSL except it's 1/8" shaft instead of 4mm.



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Photos (4)

On this and one other model (a MG PRR C1 with a Faulhaber motor driving a NWSL Mod.6 gearbox)  I've found the NWSL couplings to be quiet.  With a tight clearance set on the adjustable rotation limiters I've not heard any chatter.  That said I'll  give the hose coupling approach a try on my next upgrade project.  I do have some of that hose lying around.  A couple of years ago  the guy at our local Toyota parts department just gave me a foot of #0 hose when I told him I would be using it in a  model train. 

In adition to the Sunset PRR J1 I also have a Westside one.  It is slightly finer detailed than the Sunset but the Westside's drivers are undersized and like all KTM built PRR long distance tenders is several scale feet short.  The Westside/KTM J1 exhibits some cogging running downgrade with a heavy train.  To a lessor degree I also get some downgrade cogging with Westside M1's (same KTM gearbox).  Jay - do you think installing ball bearings and thrust washers on the  gearbox shaft would mittagate the cogging?

I didn't know about Matt's west coast connection.

Ed Rappe           PRRT&HS 421


Wish I could say conclusively, but I can't.  First thing I'd look for is backlash.  Too much back & forth play in the motor or gearbox, maybe both, can cause what you're describing.  Thrust washers (I get them from NWSL) might help.  The factory KTM gearboxes have plastic thrust washers that I typically toss.  Eliminating the backlash from the gearbox should help eliminating it from both is better.  Easy to say but the motor, depending on what you have, may be a little more difficult.  If there is a torque arm back sure it's stabilizing the gearbox properly.  I've observed, the Westside gearbox, on many of the later models, is a knockoff of the KTM and may not be quite as good.  One last thing, if the coupling between the motor and input shaft to the gearbox has to much play, or is worn out, you might see the issues described.  Bottom line, think of it as "Blue Printing" a motor for your hot rod...get everything as perfect as you can.

Matt & I try to help each other out.  Great respect for him, and his talents.


....continuing with my ramblings, I use the NWSL drive shaft parts on my diesel drives but rarely on steam.  On the really heavy ones I have the plastic burned out and cast them in bronze.  Obviously, it worked out for you.  Having the gearbox and motor in, as close as possible to, perfect alignment is a biggy.  Two thoughts though, I would lubricate the ball and socket.  I've seen them wear out under heavy loads.  I would also try to stabilize the gearbox to prevent what we used to call wrap up.  When we use the longer shafting and rubber tubing we are mitigating this issue.


Jay - I installed those brass strips fore and aft of the gearbox to stabilize it, while allowing lateral movement of the flanged main driver.  There are elongated slots on the front bar's mounting holes to adjust the tolerance.  Had I used fuel hose for the coupling I would have avoided the need for the brass strips and related drilling and tapping - but at perhaps at the price of some vibration as the flanged gearbox driver shifts laterally on tight curves.    I should note that at one time Sunset offered flanged replacement center drivers for their 2 rail PRR J1.  Even with all drivers flanged it could navigate a hidden 50" radius staging loop on my old railroad.

Ed Rappe           PRRT&HS 421

My beef with the KTM box is that it shows.  I had heard of the bronze cluster - thought NWSL had made them special.

Chatter is a feature of worm drive gears.  Minimizing that involves minimizing contact with the gearbox frame and the locomotive frame.

The motor shaft and gearbox shaft do not have to be co-axial.  Their centerlines must cross at exactly the middle of the gap between them.  This is how I got the giant 9434 motors to work on Cab Forwards (I only use 8000s now).  The Toyota hose will act as a U-joint noiselessly and with very little friction loss.

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