TheRailwire
General Discussion => N and Z Scales => Topic started by: carmelmodelrr on November 10, 2013, 06:15:47 PM
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I have a pair of Atlas SD-35's (DC). While these are weak pulling locos, each of the SD-35's runs nicely when run by itself (no consist). However, while one is marginally satisfactory, when I hook up the other one (solo) to almost any number of cars (3 or more), this SD-35's lights shine brightly, the wheels spin -- and it won't pull anything. I've replaced the gear cases, the wheel sets, the truck frames and the motor--all with no improved results. I'm at a loss to determine what is causing this. Any ideas?
Thanks.
Dick Wroblewski
carmelmodelrr
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Dick,
Is the shell sitting too low so that the pilots actually hit the rails? They could be lifting the chassis just enough to prevent traction. Does the loco run OK without the shell? Will it push the same cars without the shell?
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Dick,
Is the shell sitting too low so that the pilots actually hit the rails? They could be lifting the chassis just enough to prevent traction. Does the loco run OK without the shell? Will it push the same cars without the shell?
This is what I was thinking. I've noticed that I have to be careful putting the shell back on my some of my Atlas locomotives, because you can push the shell on far enough that the pilot will hit the rails. Usually when I push the shells down, I give a little tug upwards. You can feel the shell fit back into the detents on the frame.
DFF
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Are you positive that the wheels are actually spinning in place, or you are simply hearing the motor running, assuming that the wheels are spinning?
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Are you positive that the wheels are actually spinning in place, or you are simply hearing the motor running, assuming that the wheels are spinning?
It's pretty difficult for an N scale loco motor to spin if the wheels don't.
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It's pretty difficult for an N scale loco motor to spin if the wheels don't.
All it takes is for the universal joint to crack.
Jason
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Dick. You said they run fine by themselves.
Then the key question is: do they run the same SPEED?
Put them on the track next to each other but NOT coupled.
Run them slow, faster, front, backwards.
Do they run about the same speed.
I'm predicting one is much faster than the other. In that situation, an MU setup is pointless. The faster loco is DRAGGING (or pushing) the slower one and traction is actually LOWER than even one sometimes.
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In answer to the comments so far:
The wheels definitely move--the loco runs solo and when pulling a tiny number of cars.
One reason I replaced the motor was that the old motor was significantly slower than its "mate". Both now are about the same speed (some variation, but nothing much).
I checked the height of the shell on the body and it seems to be sitting right where it should be. I can feel the "click" when I replace the body.
I did try running the loco pulling about 6 or 7 cars on a wider radius track and there was more pull. It definitely pulled 6 or 7 cars with some regularity, but it was far from acceptable (to me) for a 6 axle loco. Furthermore, I had to really jack up the speed to get past the spinning at first.
I think I've covered most of the comments to date.
Dick Wroblewski
carmelmodelrr
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Dick,
see http://www.atlasrr.com/pdf/N%20EMD%20SD35%20DIESEL%20LOCO%20B.pdf (http://www.atlasrr.com/pdf/N%20EMD%20SD35%20DIESEL%20LOCO%20B.pdf) . If one or both universal ball joints at the ends of the worm shafts split, they would still allow the wheels to turn but they would start slipping under load. The loco would run but it would have very little pulling power.
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If you don't want to take the locos apart to check the universals, you might try this:
Find a metal weight that will sit on the loco without falling off. A square block or bar would be best. See how many cars the unit pulls without the weight, and make sure the wheels really are spinning when it stalls. You might take a Sharpie and make a mark on the side of one wheel in each truck to have something to look at.
If the wheels AREN'T turning when the unit is stalled, it's the drive train. If they do, put the weight on the loco, and see if it can pull more. If it can, the only problems left are lack of weight (you haven't carved the frame or anything, have you?) or too-slippery wheel treads. Weight I can't help with, as that would probably need a new frame casting. The wheels could have oil or grease on them, but that should hurt pickup, causing rough running. You might clean them with alcohol or track cleaner to be sure.
If the trucks don't fit right, or the pilots are too low, the extra weight will actually make things worse, by pushing the body down, which should be very noticeable. Since you've replaced the trucks, I doubt that they're the problem, although I've seen some with damaged latches that would sit too far into the loco, or would actually push the loco UP under power, disengaging the worm and worm gear.
The original motor problem sounds like you got two runs, the old "high speed" motor, and the new "scale speed".
"I did try running the loco pulling about 6 or 7 cars on a wider radius track and there was more pull. It definitely pulled 6 or 7 cars with some regularity, but it was far from acceptable (to me) for a 6 axle loco. Furthermore, I had to really jack up the speed to get past the spinning at first."
That sounds to me like two issues. First, binding in the worm/worm gear due to the sharp angle on tight curves. I've seen that before. Second, slick wheels, where the unit slips due to higher train drag when starting. Once the cars are moving, they need less tractive effort to keep moving, and the unit can handle them. It also takes more effort to pull cars on sharp curves, and you may simply have too tight a curve for long trains and 6-axle locos. That would also be prototypical.
The marks on the wheels? Some railroads used to paint white marks on tender and passenger car wheels to make sticking brakes easier to find.
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I tend to agree with the slipping under load school of thought. I had a similar problem with an SD-7 and noticed that while the wheels on one truck were spinning, the other truck's wheels were not. It was a cracked universal. With that said, i changed the flywheels to the type with a female hex from a donor engine and went with the older Atlas/Kato driveshafts. I wish they would get rid of those universals. If you do find the universal joint to be bad, be aware that they are designed to be installed in on direction (I.D. bevel toward the motor).
Edit: Forgot that you have an SD-35. I don't think they have the donut with ears (universal), do they?
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I've taken the latest suggestions and added weight to the loco. That helped considerably. One additional question, though. If I add lead wherever I can on the body, is lead an electrical conductor? Stated differently, do I need to be concerned about separating the lead on the left and right sides of the loco?
Additionally, I denatured-alcohol-cleaned the wheels and ran a bright boy over my track (which I almost never do because the track appears clean). That, too seemed to help.
Thank you for all your suggestions so far. (BTW, this loco does not have the donut with ears universal).
Dick Wroblewski
carmelmodelrr
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... One additional question, though. If I add lead wherever I can on the body, is lead an electrical conductor? ...
Yes. Maybe not as good as copper, but conductive nonetheless. Think electronics solder, which is roughly 40% lead.
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One final question. The SD-35 does not have traction tires. To improve "pull", would anyone consider putting Bull Frog Snot on the wheels of one axle? Since the wheels don't have the groove for traction tires, I'm not sure if I should consider this.
Thanks again.
Dick Wroblewski
carmelmodelrr
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Dick,
this problem has me really stumped. The SD-35 should be able very easily to pull more than 7 cars on a level track (ore even on some grade). Would you be willing to send this loco to one of the experienced loco-teardown modelers (like me) to see if we can figure out what is wrong with that model?
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Even the Bachmann 44 tonner can pull that much. Sumpin is wrong and it isn't the design or weight.
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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.
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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.
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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.
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Dick, PM sent. We'll get this thing figured out. :)
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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).
(http://i1068.photobucket.com/albums/u449/peteski7/Railwire/DickW_SD-35_01_zps344b846c.jpg)
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.
(http://i1068.photobucket.com/albums/u449/peteski7/Railwire/DickW_SD-35_02_zpsfa7db2ea.jpg)
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.
(http://i1068.photobucket.com/albums/u449/peteski7/Railwire/DickW_SD-35_03_zps4546f6eb.jpg)
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.
(http://i1068.photobucket.com/albums/u449/peteski7/Railwire/DickW_SD-35_04_zps2008481c.jpg)
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.
(http://i1068.photobucket.com/albums/u449/peteski7/Railwire/DickW_SD-35_05_zps1f52302b.jpg~original)
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...
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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
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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
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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.
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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.
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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