HO PRR K4s Size/Dimensional Comparison (Bachmann, BLI, MTH, Sunset, PFM)

Model Railroader General Discussion (Model Railroader)
1

Hey yall, I spent a good amount of time doing some comparisons of size between 5 different manufacturers of PRR K4s. I know this wont interest a lot of people, but I figured it was worthy of those of us who do model PRR, or have an interest in owning a K4s.

The Manufacturers we will be comparing are:

  1. Sunset (NON prestige), built by Samhongsa
  2. PFM, built by United
  3. Broadway Limited Imports
  4. MTH
  5. Bachmann Spectrum (last run before transistion to standard line)

To be as precise as possible, I took photos of each engine, with my camera mounted on a tripod, and all settings preset, so every photo I took was with the same exact settings, location, focal length, etc. The engines were centered by placing the middle driver to be centered on the little orange marker on the track. I then compiled all photos into Photoshop, and added RED lines, using the BLI model as a reference (as I believe this is the most accurate model, though Im sure someone can tell me otherwise).

Here are the results!

Vertical lines only:

K4s Comparison Vert
K4s Comparison Vert1920×2822 711 KB

Lines were placed at the back of the pilot deck, front of the boiler, back of the smokebox, front of the drivers, front of the firebox, rear of the drivers, front of the cab, and rear of the cab.

Horizontal lines only:

K4s Comparison Horiz
K4s Comparison Horiz1920×2825 709 KB

Lines were placed at the running board, bottom of firebox pan, and top of the boiler at the FRONT of the engine.

Key Takeaways:

In terms of dimensions, BLI and MTH K4s are nearly identical, followed by PFM, then Sunset, with Bachmann taking up the rear as the farthest from the rest.
From these photos, a lot of things are far more noticeable. Here’s some KEY TAKEAWAYS:

  1. Bachmann’s drivers are undersized, at a scale 75", while the rest are all 78 to 79". Historically, K4s had 80" drivers.
  2. Bachmann’s smokebox is longer than the rest, the graphite paint extends beyond the second column of rivets.
  3. Bachmann’s boiler is far more tapered than the rest, which looks weird. Sunset’s is the least tapered, with its firebox being oddly flat, also making the model look weird.
  4. Bachmann and Sunset’s running boards are also both high. The boilers of all engines are more or less the same height but the higher running boards make the gap between the drivers and running boards larger, making the drivers look oddly small.
  5. Bachmann’s firebox ashpan is oddly flat, and far less angled than the rest of the engines. As a result, the trailing truck looks shrunken.
  6. Sunset and Bachmann’s pilots both stick out too far out front of the engine.
  7. Sunset and PFM’s engines both have oddly spaced apart front leading truck wheels. PFM’s wheels are undersized.
  8. Sunset’s cab looks short. Should be longer. Makes the firebox look larger than it should.
  9. MTH’s K4s trailing truck leaf spring is placed far forward than the rest of the engines, resulting in a large gap between the trailing truck and the chassis, and exposing the spring.
  10. Bachmann’s firebox below the running board seems to be placed further back. There is a HUGE gap between the rear driver and the firebox, when compared to other models. This makes the drivers look even smaller.

Those are the main takeaways I see, if anyone see anything else big feel free to share!
Charles

2

Charles,

It looks like cab number font styles and sizes are all over the map. Which is the most accurate?

Tom

3

Have you ever seen a K4 in person? Based on my first had experiance viewing the prototype, the Bachmann and the PFM have the boiler “hump”/tapper the closest.

The Sunset and the Bachmann by far have the best looking trailing truck.

The MTH model has the typical MTH exaggerated details, giant rivets, etc.

I will agree, the BLI model may have the edge in terms of overal correct appearance - except for the trailing truck, which lacks the distictive bottom curve.

But honestly, they all pass my “good enough” standards, not that I will ever buy any of them.

Sheldon

4

Depends on the year you are modeling and which one of the 425 K4’s you are looking at.

I’m not the PRR expert, but many of my friends are, and you pick stuff up. The first K4’s were built in 1914, the last in 1928. Paint job specs changed sometime after WWII and most or all were refitted with some ugrades then, or slightly before as well.

A few were retired as early as 1947, and some lasted until 1960.

So, the piping differences, running board differences, lettering differences and so on, seen on these models is all likely to be based on some actual photo from some point in time.

Sheldon

5

Gidday Charles, I hope I’m not “Damning you with faint praise” as such an undertaking that you have carried out, though as you mention “I realize this is very much a rivet counter kinda issue…” is worthy at the very least a “Mention in Dispatches.”

Just because a model’s measurements may be accurate, the model may not actually look right.

I say this because I read a comment, some years ago, made by a professional modelmaker that some measurements/angles did not scale down well, and that in certain circumstances, exaggeration had to used to get the “Look.”

Thanks for your efforts.
Cheers, the Bear.[:)]

6

Charles.

I applaud the effort. It would be sweet if a prototype photo was included for comparison to the models. Through it’s nearly half century service life the K4 went through too many changes that could easily fill a sizeable book. Just the experimental locomotives would take up many chapters. It’s still amazes me that many of them went to the scrappers torch still hand fired. The many faces of the K4s is represented in model form. Close enough is way better than not at all.

Thank you for the effort.

Pete.

7

Tom - it depends on the era you’re modeling.

Sheldon - I have seen a K4s in person, and while there is a taper, I don’t recall seeing the firebox have as extreme of a taper as the Bachmann model. I also specifically am focused on the core boiler and driver dimensions , as those should be consistent throughout all K4s. Yes of course piping, paint, and such would be very different throughout the 425 engines, and that’s why I didn’t comment at all about that. However, boiler sizes, driver sizes, etc should all be the same. Bachmann engines having noticably smaller drivers is wrong, as is Sunset’s boiler shape. Many of the descrepencies I mentioned SHOULD be consistent throughout all manufacturers.

Bear - I agree, as long as the model achieves the “look”, they have accomplished their jobs. However the Bachmann and Sunset engines have always “looked” weird to me, but I could never place my finger on as to why they looked odd to me. I’ve seen thousands of K4s photos in my lifetime, so I am very familiar as to what a K4s should look like, and those models have always bothered me in how they look. That was the purpose of this exercise. I know for the average modeler, these engines look fine! And that’s what matters to them!

Pete - see this is the problem with using photos as comparison. Using photos can give you VERY precise measurements in comparisons IF the photos are taken at the same settings. (focal length/zoom, distance from object, vertical and horizontal tilt, etc). However it would be impossible to find a photo of a real K4s taken with the same exact camera angle, and would be useless in a photo comparison.

To all - I wouldn’t take these photos to heart. Always take everything you see on the internet with a grain of salt. Since we have not prototype to compare it to, we wont ever know what is most correct, BUT these photos do show the variations in model form of one of the mos

8

Charles,

Agreed, the Bachmann drivers are small.

The Bachmann trailing truck in total is the most representive of the prototype, meaning the truck itself and the bearing plate. The BLI is the clear second on this item.

The rest just have a gaping hole were the bearing plate should be, and the trailing trucks lack the distictive lower curve.

I have never quite understood the “beauty” some see in these locos, this has much better lines:

http://www.rr-fallenflags.org/bo/bo-s5317bhn.jpg

But again, to me they all could fill the bill.

Sheldon

9

Here is a dimensional diagram hosted at fallenflags:

45514 - class K4s (railfan.net)

Notice that the boiler and Belpaire firebox tops are slanted away from each other, but in descent. The only one that seems to show it to the extent evident in the diagram is the Bachmann. My opinion.

This image clearly shows the two slopes, both the conical boiler and the sloping ‘shoulders’ on the firebox:

prr-s1361G02.jpg (1040×385) (rr-fallenflags.org)

10

I agree. As per my very first comment in this thread, that has always been my opinion as well, the Bachmann is the only one with a correct firebox slope back to the cab.

And, ironicly, that is the one feature of many PRR locos that I find visually awkward and un-appealing.

The L Mikados have a nearly identical boiler to the K’s and have that same feature.

Sheldon

11

Wow. what a great post, and thank you for the effort you put into this.

I will never buy any of these locomotives,and have no interest in the PRR, but I love models and the details they have. The work you did to make the images as equal as possible is remarkable.

I was fascinated by what you pointed out.

-Kevin

12

What about the versions done by Red Ball, NJCB, and Crown Custom Products? You should separate brass K4’s from die cast and plastic…two different ball games! Snobery is not meant, but there is a tremdous difference between brass and “other”. Howell Day’s (Red Ball) K4 is no slouch and has the correct diameter pony truck wheels, but often mistaken for a PFM which had undersized pony wheels as did most of their models for tight radius clearence. PFM K-4’s came out in 1960 when the 24" curve was the standard then. They did a fine job in hiding this feature.

13

Here is a better drawing that supports the Bachmann model as having the correct amount of taper back to the cab.

https://en.wikipedia.org/wiki/Pennsylvania_Railroad_1361#/media/File:PRR-K4s-Drawing.jpg

Sheldon

14

While I do not model the steam era, I do model the PRR, so I have seen q lot comments on the K4 models out there. Not a lot of love for the Bachmann version, BLI seems to be the favorite.

15

IIRC the Bachmann engine came out about 1987, I think the other ones were much later. I believe the recent ones use the same body and such, just upgraded motor / wiring for DCC etc. For something that old, sounds like it holds up pretty well…considering when new they sold for around $50.

BTW, many model steam engines have smaller than prototype drivers, to allow for the larger than prototype flanges on the drivers.

16

The Bachmann model has been around a long time, since 1989, and has gone thru a number of upgades mechanically and electrically, before reaching a point of being a pretty good model a decade or so ago.

So there will be lots of people who bought the older ones and are/were less than thrilled.

BLI on the other hand, has only been around 21 years, and had the benefit of learning from the growing pains of Atlas, Life Like and Bachmann who pioneered model locomotives as we know them today.

The BLI K4 is a nice model, runs good, but the firebox taper is wrong.

Sheldon

17

Have to say…I’ve admired the “K-4s” since I was a kid (1950s) and all of the models shown are excellent representations of the proto. If I had modeled the PRR, I would have wanted all of them.

Too bad the Santa Fe didn’t have any…

18

I personally model the PRR on my layout from the early 1940s to the very early 1960’s. I have about 6 K4s , of various makes, Bachmann, IHC, etc.

There are slight differences but not enough to bother me, I simply am not a rivet counter. I model the PRR in the midwest ( northern Indiana) since several of my relatives , my Dad included and my Granddad on my Mom’s side work worked for them. My Dad was a brakeman, and I had two Uncles who worked for the PRR also, plus several other relatives.

One relative was the chief engineer on the famous Broadway Limited passenger train.

Right now it takes up a 6 foot wide by 24 foot long area in my basement.