Kato N SD40-2 Early vs. Mid-Production?

[ednadolski]

Would anyone know, what are the key differences between Kato's N scale SD40-2 'early' version and later 'mid-production' models?  I know the 'early' has the older/bulkier frame, with the chunkier underframes, larger wheel flanges, and different internal mechanisms (including lighting).  Also the couplers are different and I suspect the 'early' would be harder to convert to DCC/sound (esp. if it is anything like the 'snoot' version).   But what about other things as far as representing a specific prototype SD40-2, including fundamentals such as length, wheelbase, fuel tank, etc.?

I'm wondering if the Kato mid-produciton could be used to make a respectable representation of an MRL SD40-2XR.   I thought that the MRL prototypes were built from earlier EMD locos which were slightly smaller and had a few different features/configs than the later Phase 2 EMDs which are what the Kato mid is supposed to be based on.   In any case I am sure that some work would be needed to get things correct such as headlight/ditch light configuration, grilles, brakes, and such.

I'm in the research stages for both the models and the protos, so all info is appreciated.

Cheers,
Ed

[samusi01]

I’ll have to keep an eye on this to find out more… I always thought the difference was more external details (setting aside internal mechanism differences) than Kato specifying differences between runs… see, e.g., their different SD70 runs.

Given the shorter wheelbase of the prototype, particularly relating to the porches and whatnot, why not start with the straight SD40?

[learmoia]

OK... I think I can help..

The MRL SD40-2XR is an SD40 rebuilt with -2 electronics.  I can tell by the Flexcoil trucks, in relation to the fuel tank as well as the chicken wire radiator grills.
So.. if starting with a Kato.. you want an SD40 not either of the SD40-2s

Now for the differences in the Kato SD40-2s..

The first few runs (before the "mid-production" thing) were the older style frame.. I think the first runs were DC, and later runs were DCC Ready.
The SD40-2 Dynamic and Non Dynamic had chicken wire radiator grills, and the Snoot was only Dynamic and had the later production radiator grills.

The 'Mid Production' I think was a new mechanism (with new suspension?) and re-worked for ditchlights.. and Mid-Production also meant the later production SD40-2s.. so.. later grills brake wheels, anti-climbers..

I don't think the shells or parts of shells are interchangeable between the 2 runs..  and later runs of 'early' dash 2s still had the early DCC ready mech..
Maybe the earlier run still had the 'wide body' syndrome from the Atlas/Kato GP30/35 since the mechanism carried through to the to the first run of SD40-2s

~Ian

[nightmare0331]

actually, all of the early and snoot SD40-2's share the same drive regardless of run.  (the snoot was only run once in like 1999 or so...the early has run then and again in 2014-2015 timeframe IIRC but minus the wheels being changed to more fine scale, the couplers being changed to the current 923500 and the LED's being much improved color wise, they're the same.

They are all dcc friendly.  Earlier runs of SD40's and SD45's were not DCC friendly but could be converted with a bit of work.  Later runs of those were DCC friendly and can be converted to LokSound pretty easily.

All of the SD40-2's (early, snoot, mid) are pretty simple to convert to ESU LokSound with the 58741 board.

As for MRL, the only 'true' SD40-2 they had was 250, but it was a heavy wreck repair of a former BN unit.  It really has some odd spotting features if you look close.

Hope this helps!

Kelley.
www.dufordmodelworks.com

[Ed Kapuscinski]

Oh *****, I didn't realize the snoot is easy to get sound in.

Might be time to upgrade my 6366, which was made by cutting down one of those.

[ednadolski]

I didn't realize the snoot is easy to get sound in.

I used the 73100, I think the newer one should work but I haven't tried it myself:

https://www.therailwire.net/forum/index.php?topic=21548.msg685439#msg685439

Ed

[Albert in N]

   Late replying to original post due to "honey dos" around house and yard last several days, but finally getting some rain.  For my two cents worth, I own two mid-production Kato SD40-2s and one early production Kato SD40-2.  The oldest is the BN "white face" produced from 2006 to 2008.  The UP early production SD40-2 was produced in 2013, while the BN stripe nose was produced late 2021.  The mid-production units have ditch lights, illuminated number boards, rear brake hoses, and screwless chassis.  The early units don't have these and rely on traditional Kato screw and nut frame fasteners.  All run smoothly.  Frankly, I do not notice any size difference but cabs from mid-production have ditch lights and screwless construction so body shells will not interchange (at least for me).  Here is a link for disassembly of screwless mid-production:
https://www.katousa.com/N/SD40-2/maint/disassembly.html
Also, here are a few photos taken by my economy Fujifilm digital camera  (not the best, but at least pictures):

[peteski]

So both the screw and screw-less chassis use the same trucks and worms, or does the screw-less chassis use the new trucks with fine pitch gears (centered on the axle tubes), and the worm housed in the truck's gear tower?

[oakcreekco]

I've got 4 early and 4 mids.

Love them all, and they are all great runners.

The mid production "screwless" chassis have the sprung type trucks, unlike the early units. (The fine gears)

[peteski]

I've got 4 early and 4 mids.

Love them all, and they are all great runners.

The mid production "screwless" chassis have the sprung type trucks, unlike the early units. (The fine gears)

Thanks!  That is a major construction difference then.

[oakcreekco]

Yes it is. I can "service/clean/lube" the early style in my sleep. 😆

I haven't torn into the sprung style gear case and wheels. I did buy some spares from Kato for future needs.

IMO the mid releases are the nicest SD40-2's on the market for running quality and the underbody details. The trucks look as nice too

My mids are ATSF's, so I'm pleased with the body, detail and paint.

Kato fanboy I  guess. 😆 

[peteski]

Yes it is. I can "service/clean/lube" the early style in my sleep. 😆

I haven't torn into the sprung style gear case and wheels. I did buy some spares from Kato for future needs.

IMO the mid releases are the nicest SD40-2's on the market for running quality and the underbody details. The trucks look as nice too

My mids are ATSF's, so I'm pleased with the body, detail and paint.

Kato fanboy I  guess. 😆

So am I. 

Yes, those locos with fine pitch gears run like Swiss watches, but are also prone to picking up debris which lodge between teeth, causing rough running.

I devised a simple solution to prevent that.  Just a strip of masking tape over the gear openings.

[Teditor]

I took the masking tape approach, but in just attempting to run my SD70ACEs after a prolonged sleep, the gears were stuck to the tape, something to keep in mind.

"The locos had the prolonged sleep, not me!"

Ted (Teditor) Freeman
From The Land Down Under

[Ed Kapuscinski]

I used the 73100, I think the newer one should work but I haven't tried it myself:

https://www.therailwire.net/forum/index.php?topic=21548.msg685439#msg685439

Ed

Damn, and I bet that same approach would work on the regular SD40s too. Hmm.

[peteski]

I took the masking tape approach, but in just attempting to run my SD70ACEs after a prolonged sleep, the gears were stuck to the tape, something to keep in mind.

"The locos had the prolonged sleep, not me!"

Ted (Teditor) Freeman
From The Land Down Under

I'm surprised because in that truck design the gears do not protrude from the openings.  If anything, only the very tips of a tooth or two would contact the adhesive.  I have not noticed any problems in my tape installs.