Athearn GP35 buzzes around corners


malibu43

malibu43

Active Member
I have an old blue box Athearn GP35 (I think from the very early 90’s, or maybe even very late 80’s). It’s always been a loud runner, even louder than my Athearn GP9. I know that Athearn engines are notorious for being loud and that there are endless pieces of information on the internet regarding how to resolve said noise issues.

However, I just noticed a very specific noise happening in a very specific situation. My hope is that someone here might be able to help me pinpoint specifically where this noise is coming from. That way I can reduce some of the trial and error and amount of time I need to resolve the issue. I have a 6 month old, so time is precious right now!

I’m running my locomotive on an EZ track oval on a 4x8 sheet of ply wood. The turns are 22” radius. When the locomotive enters the turn, I get a very loud buzzing/rattling sound. When the locomotive leaves the turn and gets back on the straight section, the noise goes away. It consistently happens 100% of the time the locomotive is on the turn and 0% of the time it’s on the straight section. This morning, I think I actually narrowed it down to being when the rear truck (or bogey…?) its on the curved section, but I’m not 100% sure. Also the frequency of the buzzing is directly tied to the RPM/Speed of the locomotive.

So, given that this only happens on when the locomotive is in a turn, I think I can rule out any general motor or gear noise. Anyone have any ideas for what I should specifically look at?

I did look at the exterior of the locomotive to see if I can see anything obvious. There is a thin metal piece (sorry don’t know what it’s called) that sits between the inside of the wheel and the truck. On the rear truck, the metal piece is touching or almost touching the inside of on of the wheels. I’m wondering if the wheel is pushed too close to this piece when on a curved rail and that results in buzzing. I may try to adjust the gap and see if that helps. It would be nice if it was that easy, but I’m not getting my hopes up. Taking the shell off is just a PIA since my plow is glued on and will have to be broken off and then eventually glued back on again. Although, I’m sure that’s probably the route I’ll have to go down…


Thanks.
 
Take the shell off and see if the noise continues. It sounds like a portion of the drive shaft is rubbing against the shell. You may even be able to see marks on the inside of the shell that will help you understand where the problem is occurring. The locomotive (a b-axle) should negotiate a 22" radius without too much problem. I would be interested to know what you see once you get the shell off and inspect the motor/drive shaft components.
 
Does it happen in both left and right turns? It sounds to me like something is off with the rear worm shaft/truck gearbox and when the loco turns the gears aren't meshing properly.

The metal strip you described would be a pickup, so having it touch the wheel is a good thing.
 
Scott135 said:
Take the shell off and see if the noise continues. It sounds like a portion of the drive shaft is rubbing against the shell. You may even be able to see marks on the inside of the shell that will help you understand where the problem is occurring. The locomotive (a b-axle) should negotiate a 22" radius without too much problem. I would be interested to know what you see once you get the shell off and inspect the motor/drive shaft components.
Click to expand...

I’ll take a look when I get a chance. I was hoping to not have to pull the shell off, but sounds like I’ll have to.

TrinityJayOne said:
Does it happen in both left and right turns? It sounds to me like something is off with the rear worm shaft/truck gearbox and when the loco turns the gears aren't meshing properly.

The metal strip you described would be a pickup, so having it touch the wheel is a good thing.
Click to expand...

Good question! I haven’t checked counter clockwise yet. I’ll do that before I start pulling things apart.

I don’t think the piece I’m talking about is the pickup. This especially wouldn’t make sense since none of the other 7 wheels are even close to touching it in the way this one was. I’ll try to get a picture so you can see what I’m talking about. I looked at an online exploded diagram of an Athearn GP35, but the part wasn’t labeled and doesn’t look to be in the same place mine is.
 
Ah, well that's different then. Does it look like a wiped though? Is there another one on that wheel? Perhaps it has somehow come loose from wherever it's supposed to be.
 
More than likely, the motor and flywheels are not lined up straight with the worms on top of the trucks, and as a result the "extra" torque needed to get the loco around the curves allow the flywheels to rub against the body.

After you remove the shell, you will see that the motor is slightly out of line. A simple twist to line the motor/flywheels up with the worms on the trucks will fix it.

If the motor still doesn't line up, after doing this, I'd have to say that the motor mounts have dried out and need replacing. These can be had from Athearn, or the LHS, if an Athearn dealer.
 
I recommend new motor mounts anyway, the new ones that Athearn uses now that have the screws are way better than those old ones. The less less your motor moves the better, and the more in line along the axis of the locomotive the better.
 
Thanks guys.

I did run the locomotive in the other direction, and didn’t get any noise. That should help me pinpoint it when I do finally get a chance to pop the shell off (hopefully this weekend).

FWIW – here is a shot of the “metal piece” I was talking about earlier. I don’t think it’s part of the problem at this point, though. The arrows point to the pieces I was talking about. The circle shows where I thought it might be rubbing.

2011-12-08065348.jpg


PS - Ignore the big mess of loctite around that coupler! I’m going to fix that while I have the shell off as well!
 
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If you have a digital video camera of some kind, a short video on Youtube showing operation in both directions with the shell on and off could be a big help in solving the problem.

I'm a volunteer caretaker for the HO scale layout at a local Children's Museum. We use Athearn blue box locomotives almost exclusively due to their reliability, simplicity, affordability, and interchangeability of parts. I was working at the museum last week, and the museum's Athearn BB GP35 was having a similar problem to what you are describing. The locomotive would run alright, but made a very loud growling/ buzzing sound. When the power to the locomotive was cut, it would stop immediately. A healthy Athearn locomotive should coast for a second or two after having its power cut because of those wonderful dual flywheels inside the locomotive.

I opened up the locomotive, and quickly found the problem. Athearn locomotives use a long metal contact strip to carry power from the trucks to the motor. The contact strip was a bit bent out of shape, which was holding the trucks at a slight cant. The locomotive would run alright on the straights, but would buzz on the curves because the contact strip was holding the trucks out of alignment, causing undue stress on the strip and the drivetrain. I removed the strip, bent it back into shape, re-installed it, and the locomotive ran beautifully.

My guess is that your locomotive's contact strip is bent, thus inhibiting the movement of the trucks. Cjcrescent's suggestion of a mis-aligned motor could also cause a similar sound.

While the contact strip does make it easier to maintain the locomotive in the future (since it can be easily removed), many people do not think it is worth the trouble, and replace it with jumpers soldered from the truck contacts to the motor contact.
 
Also a good hypothesis. I would recommend doing the hard wires when you take the shell off, but the tops of the trucks can be difficult to solder. I have also seen modifications where the top of the motor was soldered and there was a hole drilled for a 2-56 screw to hold the wire on the truck. That way when your locomotive is due for its annual you can more easily remove the motor.
 
OK. Let's try these:

The sound and video quality isn't great, but maybe it will help.

[YOUTUBE]qVMsh-IVIvE[/YOUTUBE]

[YOUTUBE]tNW3eV5YhKM[/YOUTUBE]

You can hear the grinding/buzzing noise kick in when it starts the turn and then it goes away when it leaves the turn. It still seems like it's coming from the rear truck.

I looked and for the life of me can't see anything rubbing...

Any thoughts?
 
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Here are a couple of images of the locomotive in the turn. Maybe someone will see something that looks off, although I sure can't.

2011-12-10100853.jpg


2011-12-10100805.jpg


Any advice would be appreciated!
 
Also, I just hooked the locomotive back up to the rolling stock and noticed that the buzzing sound is much more noticeable. I took a video, but the difference in sound didn't come through.

I'm not sure why the sound would be worse with rolling stock couple up...? Maybe a coupler issue?
 
Okay, after watching the videos and looking at the photos, I can see a couple things.

1). You are not getting any power from your front truck. In the side-view photo, the metal contact strip is not touching the lead truck's contact hanger.

2). The contact strip is excessively rusty, the commutator is very dirty, and the drive shafts are dry.

3). The motor is quite loud, especially when going around curves.

All this (at least to me) seems to point to one general problem: lack of maintenance.

Athearn Blue Box locomotives are good, solid, long-lasting locomotives. However, they do have to be properly maintained. The locomotives that I take care of at the children's museum run well and fairly quietly, but only if I give them proper maintenance. Those locomotives run for 7 hours a day, 6 days per week, so they get cleaned, lubed, etc. once a week. Fortunately, your locomotive probably won't need that much attention.:)

Basically, in your photos, I see of a lot a dirt and very little oil. The reason your motor is so loud is because of all the friction the motor is fighting against. When the locomotive enters a curve, it gets worse because now the motor has fight the drive train and the outside rail. Add the weight of a train of cars coupled to the motor, and it's really straining.

These instructions will help guide you through the dis-assembly and maintenance process for getting your locomotive running again. http://www.mcor-nmra.org/Publications/Articles/Athearn_TuneUp.html

Have a good one, and remember, "we do this because it's fun". :):D
 
weekendrailroader said:
...

Basically, in your photos, I see of a lot a dirt and very little oil. The reason your motor is so loud is because of all the friction the motor is fighting against. When the locomotive enters a curve, it gets worse because now the motor has fight the drive train and the outside rail. Add the weight of a train of cars coupled to the motor, and it's really straining.

These instructions will help guide you through the dis-assembly and maintenance process for getting your locomotive running again. http://www.mcor-nmra.org/Publications/Articles/Athearn_TuneUp.html

Have a good one, and remember, "we do this because it's fun". :):D
Click to expand...

I have to agree with this. After seeing the video and photos, your loco needs some maintenance badly! Definitely do the tune up!
 
weekendrailroader said:
Okay, after watching the videos and looking at the photos, I can see a couple things.

1). You are not getting any power from your front truck. In the side-view photo, the metal contact strip is not touching the lead truck's contact hanger.

2). The contact strip is excessively rusty, the commutator is very dirty, and the drive shafts are dry.

3). The motor is quite loud, especially when going around curves.

All this (at least to me) seems to point to one general problem: lack of maintenance.

Athearn Blue Box locomotives are good, solid, long-lasting locomotives. However, they do have to be properly maintained. The locomotives that I take care of at the children's museum run well and fairly quietly, but only if I give them proper maintenance. Those locomotives run for 7 hours a day, 6 days per week, so they get cleaned, lubed, etc. once a week. Fortunately, your locomotive probably won't need that much attention.:)

Basically, in your photos, I see of a lot a dirt and very little oil. The reason your motor is so loud is because of all the friction the motor is fighting against. When the locomotive enters a curve, it gets worse because now the motor has fight the drive train and the outside rail. Add the weight of a train of cars coupled to the motor, and it's really straining.

These instructions will help guide you through the dis-assembly and maintenance process for getting your locomotive running again. http://www.mcor-nmra.org/Publications/Articles/Athearn_TuneUp.html

Have a good one, and remember, "we do this because it's fun". :):D
Click to expand...

Thanks for your detailed response!

That link you provided has a great detailed walkthrough for taking apart and cleaning the locomotive. I’m going to try and get it done over a couple of lunch breaks this week. Is there some other common household lubricant I can use instead of the ones listed (I’ve read about using automatic transmission fluid with Teflon)? I don’t have either one of the lubricants called out in the tutorial, and I won’t have time to get to a hobby shop anytime soon.

I re-watched my videos, and am disappointed because I don’t think the specific buzzing noise that I’m referring to is coming through in the video. While the videos may give the impression that general motor noise is increasing on the corners, in reality there is a very unique and separate noise. It’s very similar to the sound you get when one truck on a piece of rolling stock is derailed, only with a higher frequency. Or like the sound you get when you stick a soda can in your front bike fork to make it sound like a motor cycle. Anyway, hopefully that doesn’t matter and the thorough cleaning rebuild with uncover or fix whatever the problem is.

Also, just so you know, the front wheels should be delivering power. The contact spring from the front wheels doesn’t touch the contact from the motor, but it does contact the spring from the headlamp (where it’s curled under). So the power should still get to the motor. I noticed in the instructions in the link you sent that the headlamp spring is bent differently than it is in either of my Athearn locos.
 
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