Question about pilot/pony trucks on ATSF 3460-Class Hudsons, 2900-Class Northerns, and the 5000-Class Texas

I consulted Model Railroader - Cyclopedia - Volume 1, Steam Locomotives edited by Linn H. Westcott. On page 95, there is a drawing of ATSF 2-10-4 #5012. It shows the pony wheel diameter as 42 inches (not including flange). So, the rolling radius from top of rail to center of wheel is 21 inches.

On page 225, the same reference has a drawing of ATSF 4-8-4 #3780 that shows the pony truck wheel diameter as 42 inches.

MELGAR

@MELGAR posted:

I consulted Model Railroader - Cyclopedia - Volume 1, Steam Locomotives edited by Linn H. Westcott. On page 95, there is a drawing of ATSF 2-10-4 #5012. It shows the pony wheel diameter as 42 inches (not including flange). So, the rolling radius from top of rail to center of wheel is 21 inches.

MELGAR

Thanks.

@AGHRMatt,

Matt,

Please note that I've revised my post to include ATSF 4-8-4 #3780. Pony truck wheel diameter also 42 inches.

MELGAR

Matt, a scale wheel will look good.

@AGHRMatt,

Matt,

I just noticed that you also asked for information on the ATSF 4-6-4 Hudson.

On pages 208/209, the same reference has a drawing of ATSF 4-6-4 #3462 that shows the pony truck wheel diameter as 37 inches.

MELGAR

@MELGAR posted:

@AGHRMatt,

Matt,

I just noticed that you also asked for information on the ATSF 4-6-4 Hudson.

On pages 208/209, the same reference has a drawing of ATSF 4-6-4 #3462 that shows the pony truck wheel diameter as 37 inches.

MELGAR

Thanks.

@AGHRMatt posted:

Thanks.

Matt, you’ll need to sneak up on your approach on this project. I’ve been through the wringer trying to get scale pilot wheels on the stock MTH or Lionel pilot trucks,…..even at 36” which is the most common on the Central Proper, it can be quite the challenge!….first, you have to make sure you have clearance on the bottom of the frame for the back and forth pivot, next, you have to watch your pilot truck’s hoop height vs. where it’s at now. Then you gotta make sure the new wheels don’t scrub up against the drivers in a curve, and lastly, the brake beam either needs to be modified or swapped out for something shorter,……like I said, sometimes I have a heck of a time with 36” in my world, I can’t even begin to imagine what 40” +++ does…..😳

Pat

Pat, seeing we are dealing with small wheels and overly large flanges on 3 rail models. Is there a general rule to follow as a starting point when doing this. Like measuring the diameter of the 3 rail flange and matching that up with the closest 2 rail diameter wheel. Figuring the smaller flange won’t add much more to the size equation. As you mentioned. The brake shoes on some models need to be reworked.

I’m also looking to go this route. I’ve purchased a couple of extra pilot trucks to experiment with. Have lots of questions. I notice most 2 rail axles I have are on the thick side. Does the Truck need to reamed out to accept a larger axle ? Or do the 2 rail wheels press on the existing axle on the truck.

How do you deal with the insulated wheel ?  

@harmonyards posted:

Matt, you’ll need to sneak up on your approach on this project. I’ve been through the wringer trying to get scale pilot wheels on the stock MTH or Lionel pilot trucks,…..even at 36” which is the most common on the Central Proper, it can be quite the challenge!….first, you have to make sure you have clearance on the bottom of the frame for the back and forth pivot, next, you have to watch your pilot truck’s hoop height vs. where it’s at now. Then you gotta make sure the new wheels don’t scrub up against the drivers in a curve, and lastly, the brake beam either needs to be modified or swapped out for something shorter,……like I said, sometimes I have a heck of a time with 36” in my world, I can’t even begin to imagine what 40” +++ does…..😳

Pat

I read an article years ago about the 1st Generation 2900-Class MTH Northerns in O Scale News. The author replaced the original wheels with 40". My suspicion is that under 36" radius (O-72) there might be some rubbing against the cylinders which I can shave out, but since the club layout is 40.5" radius (O-81) and my home layout will be 49.5"/54" (O-99/O-108) I don't think it will be an issue. On the Texas, the wheels are larger, plus have large flanges so going to a 42" wheel set shouldn't be a problem. My 3460 Blue Goose is a scale-wheel unit and doesn't have issues, but it looks like the pilot wheels are smaller than they should be. I'm looking at Code 172 wheels rather than the standard Code 145 as the slightly wider tread and slightly larger flanges can compensate for imperfections in my track work when the layout build is complete.

@Dave_C posted:

Pat, seeing we are dealing with small wheels and overly large flanges on 3 rail models. Is there a general rule to follow as a starting point when doing this. Like measuring the diameter of the 3 rail flange and matching that up with the closest 2 rail diameter wheel. Figuring the smaller flange won’t add much more to the size equation. As you mentioned. The brake shoes on some models need to be reworked.

I’m also looking to go this route. I’ve purchased a couple of extra pilot trucks to experiment with. Have lots of questions. I notice most 2 rail axles I have are on the thick side. Does the Truck need to reamed out to accept a larger axle ? Or do the 2 rail wheels press on the existing axle on the truck.

How do you deal with the insulated wheel ?  

I’ve pretty much have most of the mods on NYC machines down to a science now, obviously, there’s always a caveat,…….first things first, I try and get the wheel base correct for the model I’m reworking. Some of the MTH pilot trucks are just too grossly long, but fortunately for me, I have buckets of pilot trucks to pull from to get the wheel base right. Next is the wheel diameter and face type used on the prototype. Seems I’ve always been able to find something either exact, or so friggin close, I’m good,….I deal with the insulated wheels by knocking the insulator clean out, and using a much larger axle, as that’s how they’re supposed to be anyways…..and of course, they get center drilled as they should be. I’ve found that dead Railking chassis make great axle donors. The driver axles!….and yes, I just bore the truck to accommodate the larger axle ……..I’ll find some pictures,…..your buddies Mario & Gary have been bitten by this bug too,….and they both have an insatiable appetite for me to make them trucks pretty much on a regular basis, ….the challenge being,  doing it remotely, praying it’s going to make it through somebody else’s curves,…..I did one for Gary recently, and it needs a tweak to get through his S curve,…..

Pat

@Dave_C posted:

...

How do you deal with the insulated wheel ?  

In the case of a two-axle pony truck, just reverse one of the axles and it should electrically bridge the truck for insulated rail activation. That's not an issue in my case as I plan to use optical sensing. For a single axle pony truck, putting a wheel wiper on the insulated wheel and tying it to the pony truck structure would un-insulate it.

@AGHRMatt posted:

I read an article years ago about the 1st Generation 2900-Class MTH Northerns in O Scale News. The author replaced the original wheels with 40". My suspicion is that under 36" radius (O-72) there might be some rubbing against the cylinders which I can shave out, but since the club layout is 40.5" radius (O-81) and my home layout will be 49.5"/54" (O-99/O-108) I don't think it will be an issue. On the Texas, the wheels are larger, plus have large flanges so going to a 42" wheel set shouldn't be a problem. My 3460 Blue Goose is a scale-wheel unit and doesn't have issues, but it looks like the pilot wheels are smaller than they should be. I'm looking at Code 172 wheels rather than the standard Code 145 as the slightly wider tread and slightly larger flanges can compensate for imperfections in my track work when the layout build is complete.

Matt, ….trust me when I tell you, your curves will be the least of your worries! ….I thought the same thing when I started this crusade!….getting the hoop height correct can drive one insane sometimes!….also forgot to mention, the pivot bar can become a nuisance when you go to a scale wheel. As you go to a taller wheel, the pilot truck frame also raises up higher, ….kinda like a lift kit on a 4X4 truck,…..I hope it goes really smoothly for your project!….I’ve had some fight me to the bitter end!…

Pat

Here’s a good picture of Gary’s Dave, ….this is before I painted it to match his weathering,…..you can see how large the axle is, which is actually appropriate. Most of the insulated wheels I encounter still have a smaller ID than a Railking locomotive’s axle OD, ….so it’s just a matter of bore and press fit….

Pat

@AGHRMatt posted:

I read an article years ago about the 1st Generation 2900-Class MTH Northerns in O Scale News. The author replaced the original wheels with 40". My suspicion is that under 36" radius (O-72) there might be some rubbing against the cylinders which I can shave out, but since the club layout is 40.5" radius (O-81) and my home layout will be 49.5"/54" (O-99/O-108) I don't think it will be an issue. On the Texas, the wheels are larger, plus have large flanges so going to a 42" wheel set shouldn't be a problem. My 3460 Blue Goose is a scale-wheel unit and doesn't have issues, but it looks like the pilot wheels are smaller than they should be. I'm looking at Code 172 wheels rather than the standard Code 145 as the slightly wider tread and slightly larger flanges can compensate for imperfections in my track work when the layout build is complete.

Look at your Blue Goose’s pilot truck vs. a high rail pilot truck. MTH loves to throw you a curve ball, …..Some do not have a cast in hoop, but have a separate stamped steel hoop that’s screwed to the pilot truck’s frame,……but, I do believe in the parts dept of MTH we have those hoops available as a separate sale part,…..but don’t quote me on that, ….I’ll look and see if there’s an available part no. and report back,….those will be super handy to have on hand when attempting this mod,…..it’s a fun & cool mod, and is very rewarding, but sometimes the pitfalls are like “ oh my god, what do I do now!?” 😂😂😂

Pat

@harmonyards posted:

Matt, ….trust me when I tell you, your curves will be the least of your worries! ….I thought the same thing when I started this crusade!….getting the hoop height correct can drive one insane sometimes!….also forgot to mention, the pivot bar can become a nuisance when you go to a scale wheel. As you go to a taller wheel, the pilot truck frame also raises up higher, ….kinda like a lift kit on a 4X4 truck,…..I hope it goes really smoothly for your project!….I’ve had some fight me to the bitter end!…

Pat

Thanks for the heads up. Didn't think about that aspect. I'll dig out my Hudsons for a comparison. It's nice to have a hi-rail and scale-wheel example to compare.

@AGHRMatt posted:

Thanks for the heads up. Didn't think about that aspect. I'll dig out my Hudsons for a comparison. It's nice to have a hi-rail and scale-wheel example to compare.

Yep, …having models on hand to compare engineering aspects is always a plus,…..I’ve had some of my own models where I’ve had to strip the entire frame down, and literally mill a pocket in the frame for the pilot wheels to clear as they swing under the frame ….the things we do for scale fidelity!!….

Pat

@harmonyards posted:

Matt, you’ll need to sneak up on your approach on this project. I’ve been through the wringer trying to get scale pilot wheels on the stock MTH or Lionel pilot trucks,…..even at 36” which is the most common on the Central Proper, it can be quite the challenge!….first, you have to make sure you have clearance on the bottom of the frame for the back and forth pivot, next, you have to watch your pilot truck’s hoop height vs. where it’s at now. Then you gotta make sure the new wheels don’t scrub up against the drivers in a curve, and lastly, the brake beam either needs to be modified or swapped out for something shorter,……like I said, sometimes I have a heck of a time with 36” in my world, I can’t even begin to imagine what 40” +++ does…..😳

Pat

I was converting a MTH Allegheny to 2 rail and someone here posted that I should use smaller pilot wheels so they didn't short. I don't know who posted it but I remember having a short (on curves) until I followed that direction. (maybe Joe F?)

Now my memory is bad and this might be different, but I'd listen to Pat's post above.

Lionel doesn't use those undersized pony truck wheels for nothing. They're necessary for the wheels to clear the steam cylinders on curves. The tighter the curve, the smaller the wheels...

MELGAR