Athearn RTR SD50 grinding on curves

Model Railroader General Discussion (Model Railroader)
1

Hello all,

Recently I purchased an Athearn RTR SD50 at a train show… The locomotive (I believe) was new in the box, but it has a quirk that’s really getting on my nerves… My layout features 18" curves, and whenever this locomotive rounds such a curve, it produces a noticeable grinding sound… On tangent track it runs very quietly, however… When it makes the grinding sound on a curve, there is no noticeable drop in speed, and I’ve checked the trucks to make sure they swivel freely (they do)… I know it may have something to do with running such a large locomotive on tight turns such as those, but I also have another Athearn SD50 and an Athearn SD60, and neither of these units makes a grinding sound on my curves… I’ve searched and searched for possible solutions, and nothing cures it… I’ve lubricated the gears, gone over them multiple times to make sure they’re not cracked or broken, removed the driveshafts one at a time to see if it was one of them producing the sound, and have also tried removing the shell to see if the noise disappears… Everywhere I look, when someone else has posted this problem, removing the shell seems to be what cures it… Not for me; regardless of whether or not the shell is off or on, it still grinds on curves…

So did I just happen to purchase a lemon, is it simply refusing to take the 18" curves quietly, or is there another problem? To anyone with any sort of suggestion, you’d be helping me out a lot; I’m completely stumped here…

Thanks in advance,

Matt Florack

2

im keen for the answer on this as well. My athern gp40x does the exact same thing.

3

I have an Athearn Dash 9 unit that would do the same thing on 18" radius curves. Once I got rid of those sharp curves and put in broader curves (22-26" radius), that cured the problem.

I think the drive shafts’ universal joints were binding, but I am basing that on theory. There also could have been some rubbing on the shell from the trucks.

4

I also believe that the problem is in the universal shafts. On an 18" curve those trucks are swung about to the maximum. With the shell off, move the truck and see where the most play is in the coupling. Labelle #106 may help. Altering/ filing the shafts may help, just don’t want to increase the play though. This may be only a quick fix and the problem may return. Any way to loose those tight turns?

5

With the shell off see if the universal shaft is rubbing against the truck electrical pick up bracket that goes to the motor. These get bent and will rub against the shaft.

Also check the truck side frames. They get pushed in to far and will rub against the outside surface of the drive wheels… This will also cause gear noise on curves sometimes.

Bob

6

One of mine did the same thing. Wheels gauge where just a tad to wide, (NMRA gauge said they where OK) it would track fine but the noise bugged me. Made the gap just a tad tighter and sound went away.

Cuda Ken

7

Features? That would be a limitation.

Your issue is the curves, not the loco. To fix you would have to change out the entire power mechanism.

If you want to run large locos, you will need larger curves. If you are stuck with small curves, then you need to look at smaller locos.

David B

8

I have an RTR GP35 that does the same thing( 24 to 26 inch curves). It has the “hex drive” system and I’ve gone over it several time to clean, check for flash on the gears and universal joints and re-lube with no luck. I finally oiled the motor bearings and the problem went away. I hope this fix lasts. Got to love those Athearns.

Joe

9

All right everyone,

I’ll look into these suggestions and will let you know what I come up with… Thanks very much!

Matt F

10

I think I may have figured out what’s causing the grinding sound…

The SD50 giving me the problems is in Conrail paint… Since a lot of people suggested it was a bad U-joint on the drive shafts, I removed both drive shafts from the Conrail SD50, and in their place, I put in the two drive shafts borrowed from my other SD50, which wears DRGW paint (you’ll recall I said earlier this unit does not make the grinding sound on curves at all)… After reassembling the CR SD50 with the DRGW SD50’s drive shafts, the noise miraculously disappeared… To further confirm it, I put the suspected junk drive shafts from the CR unit into the DRGW unit; when I reassembled that, then it started making the grinding noise…

So I think I can safely assume it’s the drive shafts making the noise in the CR unit… I’ve given the DRGW unit its original drive shafts back, and I intend to begin searching for replacement shafts for the CR unit…

Thanks again, everyone! Really appreciate the help…

Matt F

11

Matt, since you plan to replace them anyway, why not try some filing fitting and reassembly w/ Labelle 106 to see if it may have been a distortion or flashing problem. Unless the shafts were bad molds or had some serious distortion, this may work. I would also like to know just what causes this phenomia. Athearn Elves, Gremlins or??

12

I’ll certainly look into it… I’ve already ordered new parts for it, but if I can get the “junk” ones in good order, I guess I’ll have a nice set of spares then… [Y]