Locomotive truck width - close to scale?

I run premier MTH and yes the truck side frames are way to wide. I narrow all of mine and still they are too wide. They need to come up with new side frames. This really shows up on the two rail versions. Some Railking are pretty good.

3-rail truck sideframes are between 1/4" and 1/2" too wide to accommodate both the width of the wheels and back and forth play necessary to stay on uneven track.

I think he was talking about wheelbase, which is probably better classed as "length".  Truck width, for O Scale Hi Rail, is hopeless - often wider than the car body.  Proto-48 is the only group that is scale width.

I stand corrected.

I have no idea what the actual dimension is, scaled down, but as rdunniii said, there is simply no way to duplicate that in O Scale, no matter how many rails.  I have a scale freight car truck that is 1 7/8" wide over journal lids.  I would say that a scaled down Diesel truck would be around 2" over the outside of the journal caps.  Normal car bodies are 2 1/2" wide, so the overhang would be 1/4".

Ok, so I've done some digging, and this is the dimensional data that I could find on the Blomberg 4-wheel truck design...

What this tells me is the inside dimension between the sideframes is 72-17/32, we'll call it 72.5".  Distance to between the center casting of the side frames, as shown in the drawing is 79-1/2"; a difference of 7"... so, to go to the outside of the end of the casting, we'll add another 7 inches, which brings us up to 86.5%.

Scale down 86.5", and we get 1.80".  Lionel's scale F3 and Atlas' scale F2 truck castings measure 1.93", for a difference of 0.13"; or a full size 6.24".

So, to say that the truck width across the sideframe castings are hopelessly wider is a bit of a stretch... more like acceptable to me.  Not really 0.25-0.5" too wide, but only a reasonable 1/16" on each side.

Again, I don't know of the MTH trucks, but I can sleep better knowing that the wheel flanges are bigger than how much the side frames are off...

For those of you that have more modern locomotives, here's some detail of EMD's HTC truck dimensions:

I hope this helps! 

Thanks,

Mario

References:

Blomberg Trucks: EMD Truck Maintenance Instructions

HTC Trucks: ASME Publication - July 1984

According to my calculations, if you take the HTC (3-axle SD truck) "overall" dimensions of 9' 8-5/8" (116.6"), which I assume is over the brake cylinders, it comes out to 2.4".  I have an SD40 in the box I'll have to measure.

Hot Water, can you share any information?

Thanks,

-Mario

OCS Blomberg truck from PD hobbies with P48 bolster from Protocraft vs Lionel's latest truck for its ES44s.

Huge difference to me.

With P48, track is 1.177" inside-inside while O gauge is 1.250", only .043" difference.  But when you figure in the width of each O gauge wheel, all that extra wheel width pushes the inside of the frame out even more.  The width of O gauge wheels is the real big culprit when it comes to width of the truck frame, the frame has to be wide enough to accept those wide wheels.

Look at how thin those P48 wheels are in the truck from P&D Hobbies.

The numbers and dimensions don't lie. 

I measured across the frame casting on my F units and got 92.6", which the drawing show to be 86.5".  Pretty close.

The Blomberg frame castings are 14" thinner across the frame than the EMD HTC truck, so I would expect a modern diesel's truck frame to be 0.3" wider than an F's. 

Can we see a picture of the P48 Blomberg next to a Lionel F unit truck or an Atlas'?

Thanks,

Mario

Lionel yes.

I have found this thread extremely interesting, and kudos to Mario for doing such a masterful job with his Lionel F units.  A couple of points:

I did go all out with the MTH trucks, but you don't have to get that involved, particularly if you are in three rail. Remove the trucks, slot the mounting holes on the side frame mounting tabs as far as you can, and screw them back in.  You'll move the trucks inwards by a good .125"

The photo above by Rdunni is very instructive.  The MTH trucks (not shown) stick out much further than the Lionel trucks.  The gap between the inside face of the sideframe and the face of the wheel is .225" in two rail, or about .125" in three rail.  This huge gap is not to allow for any required clearance, as the lateral play in the axles is less than .010"   I think rather its to allow ease of assembly and to allow ready replacement of the traction tires.  The MTH side frames are screwed in from the bottom, not the top as are the Lionel (and Atlas). Allowing access to those screws is what juts the sideframes out.

I am sure that the numbers don't lie. The issue is whether the trucks "look right". By that I mean are the sideframes tucked inside the vertical plane of the shell, as in the real thing, or do they stick out.  That can sometimes be a bit of a challenge when we are dealing with conventional O gauge track, rather than proto 48.  But it looks like Mario has solved it.

Lastly, I have moved Atlas RS-1 sideframes inward by simply filing down the tabs, and gluing them closer.  I used JB weld, and stuck a thin cardboard spacer between the sideframes and the wheel faces.  I hen applied a small drop of JB weld between the mating flange on the side frame and truck and clamped until it cured

These small drops of JB weld can be readily broken, if things are not aligned right. After checking clearances, I beefed up the joints by wrapping carpet thread round them and then saturating the thread with JB weld:

The difference is quite noticeable:

Thanks, John.  As always, you photos make me jealous and eager at the same time, just beautiful.

I never noticed how much these do stick out until I went back and looked.

Funny, I don't they don't stick out that far on the F units.

I'll have to try the slotted hole idea... Thanks!

-Mario

Uh, the truck side frames are too thick, I'm sure, but we do know that O-"gauge"

is incorrect in and of itself, and is not appropriate for 1:48 O-"scale", don't we? It's 5 feet, not 4'8.5", as it "should" be. We know this. This accounts for some of the Fat Trucks.

Plus...there's a big rail down the middle of the track. Not an excuse for sloppy modeling,

mind you, but definitely a reason (along with the 5' gauge) to be forgiving. Then there's the swinging pilot thing...

The models look really great. The trucks look great. It makes no difference to my efforts,

but this reminds me of "straining at a gnat to swallow a camel".

What swinging pilot thing?

Here are my MTH RS11 One is not altered the other is narrowed by elongating the screw holes.

Clem 

Wow, Clem!  They were not kidding, you can really see the space between the wheel and the sideframe.  And, you can really see the difference the slot makes.

How did you make the slots?  It's nice that you can get to the screws from the bottom, like the new Lionel stuff.  You can do that with Atlas too, but the older Lionel scale stuff has them from the top, like above.  I'm not taking them apart again to get to them; its a pain.

Thanks for sharing!

-Mario

Here's a quick side-by-side with your fab RS-1 and my stock...

PS - Thanks for the kind words.

Thanks,

Mario

I submit for your consideration:

Below is the actual measurement of the casting of a Lionel Legacy GP7 Blomberg truck.

1.94" = 93.1" (Compare to Picture 1; 86.5" across the casting)

This means that the actual variance from the nominal is 6.6" on the prototype, or 0.138" at this measurement point, for a difference of 0.069" per side.

An US quarter is 0.069" thick...

The difference of a thickness of a quarter is not what I would describe as grossly oversized.

Thanks,

Mario