Atlas GP39-2 ---- my new favorite locos

[u18b]

Received my 3 GP39-2s today.   Non-DCC, non-Sound

Shell molding is good- same as always.  Now extra details (like uncoupling bars) except for the roof vent (which looks good).

The bell is half a bell and it is molded are part of the walkway piece.

Chassis has some changes.

Same trucks.
Same motor.
Same late version worm with u-joint (no need to Beardenize these).
Same fuel tank.

Two major changes are:

1.  Screwless design.  Atlas took the cue from Kato.

2.  Jumper wires have been soldered to the truck pickup shoes.  This wire then "plugs" into the chassis (press fit).  I assume this is because spotty electrical pickup does not work with sound very well.

So gone are the phosphor bronze strips the run down the sides-- though the slots in the fuel tank are there is you want to "back date" this to the old style chassis.

I would assume that these jumper wires will eventually break, but since Atlas is so great with parts, I also assume that new pickups with the wire already soldered on will be able to be bought pretty cheap in the future.

With the shell off..... this is the very most quietest 4-axle chassis I have ever seen (heard).  With the shell on, there is a little bit more noise- but hardly any.

Well, of the tree.... the REading unit has a bit more whine to it-- maybe the shell is a bit tight.    I'll have to see.

Overall, these are great locos!

[nscaler711]

Think we could get a picture of the redesigns on this please?

[peteski]

The new mechanism is likely very similar to the new Atlas SD35 which was extensively discussed (with photos) in this thread.

Mark also has some good photos of that SD35 chassis (again,  similar to what Atlas used in this loco).  See http://spookshow.net/loco/sd35ln.html

Personally I prefer the older design with screws - it to me seems to allow a more positive (and precise) way of keeping the frame halves together, and does not require 4 hands (which for example the Kato screw-less design seems to require).

Ron, in that SD35 thread I mentioned above we speculated that the pickup wires design is simply because the new frame design (with speaker mounted in the tank) leaves no place to install those usual pickup strips. To me that seems like a kluge, and a move backward (but I get chastised by some here for that opinion). Personally I would like to see a totally wire-free design.  Which is funny, because they went with a wire-free  design at the decoder (no wires to the motor or speaker), but then they added 4 wires at the trucks. 

[u18b]

Peteski is correct.  The design is the same as the SD35 overall.

Loco boxed well.  A fraction looser than the dark grey foam (which was pretty tight).   This is snug- but not too tight.



These three locos made it all the way to CSX in these schemes- amazing.  I look forward to weathering and patching them for CSX.




New 4-axle sound capable chassis.



Like the SD35, the wire "plugs" in to the frame.   I think this might make disassembly a bit more challenging.



I think this might be why the Reading unit was a bit noisier.  The shell was pinching one of the wires.



Non-sound/non-DCC version apparently comes with the speaker.



To answer Peteski, yes this could be back dated.
I happened to have a pick up strip from something (maybe a GP35 or 38).  It fits in the slots.



However, this loco apparently might have new design pick up shoes.  Notice the tab is very short.  It will not touch the strip as-is.  Would require bending.   Might be unsightly for those that want to try.


Hope the photos help.

[u18b]

A few more shots.

Board removed.




Insulator removed.


I like the chassis design- though disassembling the trucks is a little bit of a hassle.



The "Beardenizer Killer".  A wonderful u-joint to reduce noise.

I wonder if these could be inserted and used in other locos.

[peteski]

Thanks for the photos Ron. Well that blows the theory at to why they are using wires on the trucks.  Now it looks like  they wanted to increase the contact reliability between the chassis and trucks (so they used wires).  However I don't think that the original pickup strips were all the problematic. I still prefer that design.  I Also don't' like the how the wires are soldered to the pickup plates.  But that is just me being me.

Going back to the retrofit pickup strips: so once you bend them to contact the trucks and slip on the shell, everything still works properly?

[u18b]

Forgot to mention that when disassembling..... keep the motor and the worms in the right side.   It has the channels for the worms.

As shown in this shot.

[u18b]

OK Pete....  Just for you.

Disassembled.
The pick-up plug is press fit into the hole.  When the chassis is opened up, you can press it out.  You can just see where to press the plug in this photo.... the lower right edge of the right worm in this photo.



So I removed the stock trucks and wires.
I then searched my parts drawer.  I found two pick up strips and installed them. 

I also could not find more Blomberg trucks.   But I did find a pair of Atlas AAR trucks from an RS-1 (I think).  So I installed them.
So the only thing I notice is the rise in the pickup-- which is because I probably I bent them down too far.

[peteski]

Thanks Ron!  Good to know that the older style pickup retrofit is possible.
Oh, does the left frame half have some sort of springy assembly to put pressure against the worm bearing blocks (like in the older design chassis)?

[u18b]

One thing I notice.... (not sure when the Chinese started doing this on what Atlas locos....)

Is the balancing.   So the flywheels are not solid.  They have a little groove on the outside.  A tiny application of some kind of putty allows for balancing of the flywheels.  I think I first saw this in Fox Valley's first loco years ago.

But look at the motor.  Someone at the factory took all the trouble to NUMBER each motor pole with a Sharpie black marker (how would you like to have THAT job at the factory-  only 1,022 motor to go for my shift today!)
Then, you can also see where some of that blue stuff is applied to the motor- I assume for balancing the motor itself.

So there appears to be a good bit of extra work that goes into making these motors as quiet as they are.

As I said above.... when it is a bare chassis with no shell.... it is astounding how quiet these are.  The shell of course adds an echo chamber effect.... and would also press on the chassis slightly- thus adding some noise.

[u18b]

Thanks Ron!  Good to know that the older style pickup retrofit is possible.
Oh, does the left frame half have some sort of springy assembly to put pressure against the worm bearing blocks (like in the older design chassis)?

Pete...
Those brass springy things we first saw made by Kato almost 30 years ago are gone.  The left frame is bare.   So the tolerances are such that the frame must just touch the bearings.  And it works.  No excess noise.  The u-joint does its job.

That was the problem in the old GP30/35 design that led me to Beardenize by removing the inner bearing.  I assume that back then Kato engineers allowed a slight amount a play in the bearings to give them a micro amount of wiggle since the worm shaft was fixed and rigid.  The brass springy fingers held the bearings in place.... but noise still happened with both bearings.

This tiny U-joint (which I assume first appeared on the SD35 with the chassis redesign) is a great piece to have in the parts box for kitbashing and tinkering.   I'll probably buy a dozen or so in my next parts order from Atlas.

If Atlas adds this joint to all their 4-axle locos.... then Beardenizing a GP7/9/38/40 will be a thing of the past!

[mecgp7]

I spoke with Atlas and they confirmed that the new chassis will accept the GP38, -2, 40, etc. shells. The fuel tank is interchangeable as are the truck side-frames.

[spookshow]

One thing I noticed with my DCC-Sound GP39-2 is that it doesn't have quite as much pulling power as my older GP40-2's (21 cars vs 24 cars). I'm not sure what the deal is there since they both weigh exactly the same (2.7 oz). It might could be that the GP39-2 just needs some more breaking in (I've only run it for about an hour so far), so I'll have to see if anything changes with some more running time.

-Mark

[Ngineer]

How do you install a TCS AMD4/ASD4 decoder into a new non-DCC GP39-2 or SD35?

I assume that the 4 contacts from the motor (speaker?) have to soldered to the decoder? 

   Javier

[peteski]

One thing I notice.... (not sure when the Chinese started doing this on what Atlas locos....)

Is the balancing.   So the flywheels are not solid.  They have a little groove on the outside.  A tiny application of some kind of putty allows for balancing of the flywheels.  I think I first saw this in Fox Valley's first loco years ago.

But look at the motor.  Someone at the factory took all the trouble to NUMBER each motor pole with a Sharpie black marker (how would you like to have THAT job at the factory-  only 1,022 motor to go for my shift today!)
Then, you can also see where some of that blue stuff is applied to the motor- I assume for balancing the motor itself.

So there appears to be a good bit of extra work that goes into making these motors as quiet as they are.

The grooved flywheels, bits of blue (epoxy?) weights and numbered poles have been seen for quite some time already (on Atlas and other brand models).  My FVM Hiawatha 4-4-2 utilizes such motor.   The blue weights are used on both the motor armature and the flywheels. I don't recall exactly, but I might even have an older model with those features.

I suspect that the motors are manufactured by some contract manufacturer that makes motors for several Chinese factories, so it ends up  in various brand name models.  Or, as we now know, since the same large manufacturer makes models for multiple companies, they use their in-house-made motor in multiple brand's models.