Atlas SD-35

[johnh35]

Even the Bachmann 44 tonner can pull that much. Sumpin is wrong and it isn't the design or weight.

[Bob Horn]

After watching this go on I pulled one of my SD-35's out and hooked it to a train. 22 cars, flat layout, DCC, no problems at all. 25 cars would cause it to slip. My only thought for Dick's is the u-joint on the worm being either loose or cracked. Either was a little CA will cure the problem. Bob.

[johnh35]

After watching this go on I pulled one of my SD-35's out and hooked it to a train. 22 cars, flat layout, DCC, no problems at all. 25 cars would cause it to slip. My only thought for Dick's is the u-joint on the worm being either loose or cracked. Either was a little CA will cure the problem. Bob.

Good point, I have seen those ball couplings slip on the worm shaft. I didn't think about that part.

[Bob Horn]

I have run a 74 car intermodal train on this layout with 2 Kato ES-44's on the point. Just under a mile in length, never out of 180 degree turns. Was fun but it owned the layout.

[peteski]

Dick, PM sent. We'll get this thing figured out. 

[peteski]

I received Dick's ailing locos today. Like a kid with presents at Christmas, I could not resist them. Mmmmm... fresh meat models to be taken apart! I put all my other projects aside so I can evaluate these puppies!  I can clearly see why these are very poor pullers.  Read on.

Initial findings: Loco #1 (road # 7421)
1 gray truck (rear), 1 black truck (front).  Lots of vertical play in both trucks - might be normal for this model...
Electric pickup ok on both trucks and all wheels, but a bit intermittent. Suspect dirty contact strips between truck and chassis.

Front truck (black) is missing its idler gears!  That makes it a dummy (freewheeling) truck.  Locomotive is only  propelled by the rear truck!

Front coupler - Accumate.  Affixed with a screw and some hot-melt glue. The glue got in the coupler pocket and prevents the coupler from swinging freely.

Rear coupler - MT.  It is affixed using the Atlas stock plastic retainer and some hot-melt glue. It is very loosely mounted - has lots of vertical play.

Findings after disassembly:
Motor and the rest of the chassis drive train is assembled correctly.

The electric pickup strips for the trucks are bent down unevenly, which could cause poor electrical pickup.


Initial findings: Loco #2 (road # 7413)
1 gray truck (front), 1 black truck (rear).  Front truck has lot of vertical play. Rear truck seems not to have as much vertical play.

Front left power pickup strip is pinched under a tab in the chassis (not contacting the metal nub on the truck's sideframe).



Rear right pickup strip is pushed towards the outside of the locomotive (not riding over the nub on the truck's sideframe metal nub).  This causes poor electrical pickup.



Front truck still has its idler gears but it is freewheeling (again, a dummy truck). I suspect that the worm gear has been removed.  This locomotive is also only propelled by its rear truck!

Front coupler - MT, mounted with a screw.  Works correctly.

Rear coupler - Accumate, mounted with a screw. Works correctly.

Findings after disassembly:

The freewheeling of the truck was caused by incorrectly installed worm/spur gear.  It is flipped 180 degrees, so the spur gear part of the worm gear does not mesh with the idler gears.



It appears that in these models the worm bearing blocks are not square.  On this particular model, both inside bearing blocks were installed 90 degrees off from their correct position. Because of that, they were press-fit into the guides in the chassis. But they were not fully seated, causing the worm to be skewed, not parallel to the model's center line.



The power pickup strips for the trucks are bent down unevenly which could cause poor electrical pickup.

EDIT/Update:
The freewheeling truck on this model is also not assembled correctly.  The sideframe bearing/pickup plate on one side is not seated properly causing the entire truck to be twisted slightly.  That distortion caused the wheelsets to bind.  That creates extra drag, slowing the model down.



As far as the vertical play in trucks, this seems to be due to the worn out surfaces in the gear tower: A pivot point which in which the chassis rests and the sloped truck retainers on top of the gear tower.

The U-joints on both models are fine.

These models can be brought back to perfect operating condition. I'll just need to get some parts (gear towers and some idler gears.  Stay tuned for updates...

[davefoxx]

Good findings, Pete.  I had some similar problems in the SD50s that I have been tweaking recently, especially that bearing installation problem.  Mine weren't necessarily installed ninety degrees from the correct position, but they were not square and in line, i.e., not seated properly, which I believe caused some of the stalling (slowing down) that I experienced with my locomotives.

DFF

[carmelmodelrr]

First of all, I want to thank Peteski for his interest and invaluable assistance in (hopefully) getting my SD-35's back in working order.  I'm truly grateful.  However, I do want to mention that although the locos, as delivered to him, were in pretty bad condition, that condition was not the sole reason they ran so poorly.  At the beginning, when I placed these locos back on the layout after a period of inactivity, they had little pulling power (even though they had run just fine when I took them off the layout).  I began by disassembling them to determine what the problem(s) was.  Among other things, I ordered several replacement parts, including one motor, and nothing seemed to improve the running of these locos.  I estimate that over a period of 6 weeks I disassembled the locos 20 times--still no improvement. I finally concluded that these would be"shelf queens", put the locos back without any care and was ready to place them on display when Peteski's generous offer came through.  So I packed them "as is" since I was certain that he would disassemble them to determine the problem(s) and sent them off.  That accounts for most of the problems that he mentions in his post.  I am truly puzzled as to why one of the trucks had no gears in it, but other than that, I still don't know what the real problems are.  Hopefully the locos will run well after Peteski's RX.  Thanks again to Peteski for his interest and his generous offer and I look forward to having a pair of working SD35's in relatively short order.

Dick Wroblewski
carmelmodelrr

[peteski]

As far as the freewheeling trucks go, flipping the worm gear in one of the trucks could have been done very easily, and I can see how that could be done without noticing it.  Actually, that is a very handy way of disabling a truck without even removing any parts. I have to remember that trick.

But the idler gear removal can only be done when the truck is fully disassembled.  Do you recall taking the truck apart?  If not, then this really is puzzling. I suppose that it could have came from the factory like that, but if that is the case, that loco would have been an anemic puller right from the start.

I also found traces of what looks like Bullfrog Snot on some of the truck sideframes. Transparent green stuff. Did you try at some point to use that stuff?

When locomotive models sit unused for a while, they get a bit lethargic.  The lubrication can harden up, oily film can build up on the motor's commutator, the contact areas on the electrical pickup strips can develop some oxidation, etc. Sometimes just running them for a while can clear things up. But other times they need to be taken apart and cleaned.  The fact that they sat for a while probably contributed to the overall problem.   The unpowered trucks in which its wheels binding also affected the overall performance. The fact that only one truck was propelling these on the track also greatly affected their performance.

But all of those problems can be taken care of.  I'll contact Dick directly with the cost of parts.

[peteski]

UPDATE: I corresponded with Dick through email. He advised me that the misaligned truck contact strips were not part of the original problem. He simply didn't check whether they were properly seated when he reassembled the model right before shipping it to me.

[carmelmodelrr]

Some time ago I started a thread on my poor-pulling SD-35's.  After many suggestions, "Peteski" offered to look at them, do what he could, and send them back to me with just the cost of parts and postage to be paid by me.  That was an offer I couldn't refuse--and I'm glad I didn't refuse.  He determined that the only parts that needed replacement were 2 truck sideframes and one set of gears.  He also offered to replace cosmetic "problems": one cracked headlight cover and replacement of dull yellow LEDs with bright white LEDs (and capacitors).  As you'll see in the discussion, a few 00-90 screws and some 0.015" plastic washers were also used.

Here is what he did to make a startling improvement in the appearance and pulling power of the locos.

The chassis was fully disassembled.  All parts were cleaned in an ultrasonic cleaner, then lubricated during re-assembly.  All the wheelsets were properly gauged and 0.015" plastic washers were placed on each axle to prevent them from going out of gauge in the future.  The oil and grease that he used was lighter than what Atlas uses.  He also polished the ends of the flat electric pickup strips, the nibs on the truck sideframes and the motor's contact strips to improve contact reliability.  He used 00-90 screws to solidly attach the loose couplers--which were checked for proper height.

All of the above "tune-up" sure made a difference in the pulling power of the locos.  The bright white LEDs really improve the appearance of the locos, too.

Thanks to all who contributed suggestions and, obviously, thanks to Peteski for his fine work. 

Dick Wroblewski
carmelmodelrr