Changing out wheel sets?

Hi Chris I did an AC44, they might be the same idea.

I've done quite a few.  I can offer a few tips.  

I also have two sets of high-rail wheelsets from mth premier SD70ACE's if anyone wants to trade me them for the 2-rail wheelsets

Martin,

Are the SD70 the same as a GP38?

I haven't done a gp38, but it should be the same process, but with two fewer axles.

Martin, sent you an e-mail.

Actually, I don't want to change out the sets, unless I have to. The problem is an NS Non-power unit that does not track correctly through a curve. I have several other NP units of the same type that go through fine, and up until this unit, have not had issues with the track. So things point to the engine. I checked the lead truck on a flat piece of track (Checked with a straight edge.) The truck can have only 3 of the 4 flanged wheels touching at once. So I think I've found the problem, so of. Now it comes down to what is actually wrong: the truck casting, the wheel set(s), or improper installation, which is why I posted the question. I know how to get the wheel sets out (4 small screws and the 2 for the pickups), but what do I look for to tell what is wrong?

Chris

LVHR

PS Mike, you are right. It is actually an AC unit. The trucks are very similar.

The wheel sets can... not be seated fully, causing an issue like what I believe to be that you're describing. I have not seen a warped truck casting yet after working on a lot of MTH engines. When you remove the bottom cover on the 3/2 trucks, you can see the offending one usually. I also place a straight edge against the wheels to make sure they're all in line.

 Make sure the "bushings" are in the correct clock position to make contact with the small tab cast in the truck, underneath them.

I spent the afternoon trying to figure out what is going on with this engine. I started by getting out another NP unit and placing it on my piece of straight track. Sure enough, no wobble and all 6 axles turn freely.
So back to my problem child. To keep track of things, I numbered the axle positions 1-6, front to back. This means slots 2 and 5 have the blind wheel sets. First thing I found out is I have 2 problems in addition to the wobble: Axles 1 and 6 do not spin freely. Front truck first: Once I pulled the pickups and bottom plate off, axle 1 spun freely. I pulled all 3 wheel sets free of the casting. The blind set practically fell out, but the other 2 took more effort, especially axle 1. I tried the blind wheel set in all 3 positions. It dropped in easily in all of them. Next I tried axle 3 in all 3 positions. Again, it went in and seated fully, albeit with a bit more fuss. Axle 1 is a different story. It was a real pain to get into any slot, and the geared side would not seat all the way down. I left it in position 3, as it seemed to fit the best in that slot. When I put the plate and pickups back on, I could not tighten the screw next to position 3 fully without binding the wheel set. I repeated the procedure with the rear truck, and found axle 6 behaved similarly to axle 1.
So at this point, I believe the truck castings are OK and I have 2 bad wheel sets. It is not the wheels or the axles, but rather the bushing castings. I’ll order a pair of wheel sets from MTH and see if they cure the problem.
Sidebar: I don’t think this a related to my problem, but I’m curious. Above axles 3 and 4 are a pair of metal pins with flat faces. There are holes above axles 2 and 5, but no pins. And above axles 1 and 6, holes don’t even exist. What is the purpose of the pins?

Chris

LVHR

I believe those "pins" are for carrying the current from the wheel sets to the wiring. If that is preventing the wheels from sitting down fully leave them out. The holes are where the wiring would be for powered 3/2 models.

The cover should not be pushing down so hard as to prevent the wheels from spinning. If they are, the wheel sets are not fully seated.

I have not seen or owned any wheel sets that did not work. I have had more than enough, that were finicky about installing. Maybe the bushing got crushed somehow and is out of shape now? I have had many that were difficult to remove. I'd guess that I have converted around 1 to 2 dozen engines to 2 rail??

At his point can you hold each axle in your hands and spin the bushings freely?

Joe: I tried without the pins: no difference. I agree: Pressure from tightening the cover plate should not affect the function. Since it does, the bushing is not fully seated. The first picture above shows this on the geared side. Also, with the suspect wheel set in slot 3, the cover plate does not fully mate with the truck casting. I can see an angled gap between the plate and the casting.

Willygee: All 6 of the wheel sets spin freely if the plate is not screwed down tightly.

Chris

LVHR

Does the cover snug down firmly and look ok without any wheel sets installed ? The small black screws should bottom out and tighten with a "feel" and not feel forced.

BTW mixing wheel sets no big deal...might help in troubleshooting .

If it ain't broke, yer not tryin hard enough!

Good morning Chris....Is this a dummy unit?  I notice in your first photo the lead axle is not seated all the way down on the right side.  also try mounting the axles without those flat tipped pins..And like mentioned above try putting the truck block and plate (cover) together  without the wheels installed, should fit perfect. I have about a dozen of these six axle truck locomotives that I changed wheels on  and all are no problems.

Clem

Hey Clem, you wouldn't happen to have any Hi-rail GP38 wheel sets you would like to trade for scale would you?

mike g. posted:

Hey Clem, you wouldn't happen to have any Hi-rail GP38 wheel sets you would like to trade for scale would you?

Hi Mike......The only extra drive wheels I have, all have rubber tires. I use only the plain steel wheels.

Clem

Thanks Clem, I am so new to this, I don't even know if that would work. I know I have steel wheels on my GP38 now.

mike g. posted:

Thanks Clem, I am so new to this, I don't even know if that would work. I know I have steel wheels on my GP38 now.

On most MTH 3rail diesels all wheel sets are steel with the one's closes to center of locomotive having rubber traction tires mounted on them in a groove in the steel wheel. 2 rail have no traction tires.

clem

Hi Clem, My GP38 is so old it's just plain old Proto, with only 2 axels per truck.

Guys, Thanks for all the help. I think we are getting to the bottom of this.

Clem, Yes, this a dummy (Non Powered, or NP) unit. You are quite correct in that the mentioned wheel set is not seated correctly. That is part of the problem. It will not seat correctly in any of the 6 slots available. The flat tipped pins make no difference in the way the wheel set goes in. I left them installed.

Clem and WillyGee, I did try your suggestion to install the truck plates without the wheel sets. The rear truck is perfect.

This is how it should look. And all 4 screws bottom out very nicely.

Here is the front truck, up close and personal. We have issues. The yellow arrow shows a larger gap than is present in the same position on the rear truck. So the plate is likely warped from the wheel set not seating correctly. The red arrow shows a screw that does not bottom out. Notice the head is elevated and threads are showing. I have it as tight in the hole as I dare.

t

I returned to the back truck, since it has fewer issues. I installed both blind wheel sets (they went right in), and the tried each of the remaining flanged sets. 2 seated correctly and 2 did not. I put the truck together with the good flanged sets and on blind set. So now the rear truck is problem free.

The front truck now has the following issues: a) a screw that does not go in all the way, b) a warped plastic wheel set plate, and c) 2 flanged wheel sets that do not seat properly.

Time to call MTH for parts.

Chris

LVHR