Locomotive Drive Wheels : Box Pok, Baldwin Disk, and More

[@wardy98px1]

I love box spoke drivers and walshearts valve gear.

[@ovalwingnut]

I always wanted to be trained on the different wheel types. I now feel I'm on the right track with this video. You RoCk!

[@americansteamlegacy-yh9dr]

Hi ovalwingnut. Thank you for the compliment and I'm glad you enjoyed the video. Thanks for watching!!

[@nyeti7759]

This is really interesting to learn about and explains one of the iconic features of later American steam locos. Here in Britain disc wheels were very rare in the steam era. We did have our own variant called the Bulleid Firth Brown which is often called "Boxpok", but they were only used 1938-46 and only on some Southern Railway locomotives.

[@americansteamlegacy-yh9dr]

Hi nyeti7759. I've had a lot of viewers mention the Bullied Firth Brown drive wheel. I really need to research those and make a video for our friends across the pond!! Thanks for watching!!

[@marinegunny826]

It amazes me, the amount of engineering just to get people and stuff from one place to another

[@rrsteamer]

Earlier spoked driving wheel centers were made of cast iron and were subject to more shrinkage or porous portions of the castings. The cast steel wheel centers could have small casting defects repaired by welding depending on design specifications, type of material and welding procedures. With the BoxPok or variants from cast steel allowed for higher strength with less weight and better control of the stresses from the tire shrinkage, crank pin stresses and the operating stress during locomotive operation. Also, there was a redesign of the BoxPok centers due to deformation of the wheel rim (apparently) due to lack of strength between box sections to resist tire shrinkage pressure. But all that amounts to are the modifications due to in-service conditions. Few items work perfectly right “out of the box”. All in all, one of the better modifications developed for the steam locomotive. Thanks for the ‘lesson’ on wheel centers.

[@w.rustylane5650]

Well, I guess I'd better learn about locomotive wheels since I'm a model railroader. Didn't realize that there were that many types. Cheers from eastern TN

[@K-Effect]

I wish I knew more about the old-school Woodworking shops they had for building all the patterns. Those boys knew what they were doing

[@americansteamlegacy-yh9dr]

Hi K-Effect. Telling the story of how the guys in the pattern shop worked their magic would make a great video....that and a long list of other topics I hope to cover in this lifetime!!! Thanks for watching!!

[@stuartaaron613]

Meanwhile the Norfolk and Western, renown for some of the greatest steam locomotives, never used anything but spoked drivers. Also, the 2-6-6-6 Allegheny (Blue Ridge on the Virginian), the heaviest steam locomotive (the first group of them had a greater engine weight than the Big Boy), also used spoked drivers.

[@americansteamlegacy-yh9dr]

Hi stuartaaron613. It's hard to believe double disk type drivers weren't used more extensively on the superpower articulateds. Even the N&W J Class 4-8-4's rode on spoked drivers.

[@chefchaudard3580]

Casting made some progress with time, to the point that manufacturers, by the 40s, could cast large parts, like a chassis including the cylinders. I imagine they improved casting of spoked wheels, by controlled cooling, reheat, etc…

[@johnd8892]

Pity the lighter weight but stronger Australian design SCOA-P spoked wheel came too late to have been used outside a few Australian and African late steam locomotives.

[@wizlish]

There was also the Web-Spoke center (which, interestingly, was interchangeable with Boxpok and Scullin centers on New York Central J3a Hudsons) which addressed the rim strength and spoke-to-rim transitions by casting a 'web' into the inner face of the center. These had lower unsprung mass than a typical cast disc center. A further variant of this was the SCOA-P (for 'Steel Company of Australia - Paynter, iirc) which cast the spokes U-shaped and made the web on the outer face. These got closer to the mass savings of a deformed-plate center while retaining the ability to hold adequate angled balance mass.

[@RHJ3]

So much to learn about steam engines and this little tidbit was awesome, thank you. On a side note I was recently at the annual Utica NY model train sale and found something interesting. Its a 5 - 1/2 inch cast locomotive wheel that says Baldwin Disc Wheel across the top. It looks just like a Baldwin Disc Wheel. I'm not sure if it was a promotional item from Baldwin, maybe a paper weight, maybe you can shed some light on this item. It looks of the quality that maybe it's for a scale live steam engine. The guy I purchased it from didn't know either. Thank You.

[@americansteamlegacy-yh9dr]

Hi RHJ3. Without seeing the actual item I can't say for certain. It may have been made as a novelty item/paper weight. However, it could be a wheel for a working model of a steam locomotive. I used to work in the Baldwin Tower in Eddystone, PA. In the lobby was a working model of a Reading 4-8-4 that ran on what appeared to be 6" gauge track. As I recall, the drivers where about 8" in diameter. So, your wheel could be for a working model that may have run on smaller gauge track. I hope this helps. Thanks for watching!!

[@pascalelefebvre6942]

Certaines 141R construite aux États Unis pour la SNCF avais des roues identiques

[@antoinepenciolelli2845]

J'ai toujours aimé les disques Scullin donnant une allure plus moderne aux locomotives.

[@johnblair8146]

Box Pok is pronounced Box Spoke.

[@Boxpok]

Not a lot of people would know that anymore……

[@josephschuster1494]

Great info, many thanks! 🚂

[@Toledo1940]

HOW do you claim to know this?????

[@oriontaylor]

@@Toledo1940If it’s like me, from hearing it from people who were old enough to know.

[@Toledo1940]

@@oriontaylor That would include me; I'm 83 years old.

[@plunkervillerr1529]

Outstanding!, for me that was Pok Baldwin Over Loud.

[@Tom-Lahaye]

Good explanation, now I do better understand the different types of hollow cast wheels and how they look internally. The Boxpok design also made it on a limited scale to Europe, most notably are the British Southern Railway Bulleid Q1 freight locomotives and the Pacific types. Also the Soviet Union used them in many later designs. In East Germany the Pacifics class 01.5 rebuilds were known for these wheels, the class was partially fitted with them, but as there was a design flaw in these wheels which caused cracks forming they all reverted to standard spoked wheels. But these loco's certainly looked cool with their Boxpok wheels, skyliner dome cladding and pointed smoke box doors. Lastly there were the French 141R Mikado's built under lend lease by US and Canadian manufacturers which were partly fitted with those wheels, sometimes only the main driver. Except for the East German 01.5 of which only spoked wheel examples survive there are survivors of the other types, partially operational.

[@americansteamlegacy-yh9dr]

Hi Tom. I'm glad you enjoyed the video. Thanks for sharing all that great information on disk type drivers used on European locomotives. I wasn't sure to what extent these types of drivers where used in Europe. Thank you for your comment and thanks for watching!!

[@johnd8892]

The Bullied wheels were not a Box Pok, but the Bullied Firth Brown design. I would expect Bullied would claim it is a superior design, but more likely just a sufficiently different way of building it and design so as not to need any payments to the Box Pok design owners. Also could be produced locally in the UK by the Firth Brown company, which was very important during the wheels introduction at the start of World War Two. Shipping locomotive wheels from the US not being a high priority

[@johnd8892]

Wikipedia has some useful information on the Bullied wheels. Part of the story : The Bulleid Firth Brown, or BFB, is sometimes, but inaccurately, referred to as a Boxpok in reference to the wheel used by a number of US railway companies. The BFB is visually similar to the Boxpok, but is of a different design; the Boxpok is composed of sections fixed together to make a hollow shape, while the BFB is cast in a single piece, like a spoked wheel, the shape giving the rigidity needed. It also points to the Australian SCOA-P wheel with its advantages.

[@wizlish]

The Bulleid [note sp.] Firth Brown wheel is not a Boxpok wheel. It is essentially a single folded plate, and is an impressive piece of foundryman's skill (Wiki notes that one 'source' says the first 'B' in BFB ought to stand for 'Beaumont' rather than 'Bulleid'. If these were not cast really well out of good material they could have 'issues' with stress raising and breakage -- note that Riddles went back to spoked drivers on the postwar BR 'standards'.

[@williamadams7865]

No mention of the SCOAP type wheels ;)

[@robertchapman6795]

Victorian Railways R class used SCOA-P driving wheels. But I’ve never seen them on anything else. I know they’re an Aussie design, but I can’t remember what SCOA-P stands for.

[@wizlish]

Steel Company of Australia - Paynter.

[@WilsonPendarvis-tn3wm]

Pimp my loc. that one is all boxed out. Respect

[@wizlish]

Boxster

[@dominicwroblewski5832]

Great video. This answered a lot of questions about late steam era drivers.

[@americansteamlegacy-yh9dr]

Hi Dominic. I'm glad you like the video and I'm even more glad to know it answered a lot of your questions!! Thank you for your feedback and thanks for watching!!

[@stanleydomalewski8497]

Great Video !

[@americansteamlegacy-yh9dr]

Hi stanleydomalewski8497. Thank You!!! And thanks for watching!!!

[@KenanTurkiye]

roses are red, violets are blue there's trains and trams in my playlist two there ya go, that somehow rhymed :))

[@KenanTurkiye]

....I had to subscribe, this channel is a gold mine or a vagon full of coal. :)

[@americansteamlegacy-yh9dr]

Hi @@KenanTurkiye. I'm not a poet either but your attempt is better than anything I could come up with. LOL. Thank you for the compliment and thanks for subscribing!!

[@KenanTurkiye]

@@americansteamlegacy-yh9dr Thank you for the kind words and great uploads. Have a wonderful day!

[@wizlish]

Roses are red Drivers are black Our cast driver centers Are so hard to crack

[@KenanTurkiye]

@@wizlish my man, you win

[@colinrobert-kv2up]

Round House everywhere,,,only no roads yet but horses, trails reform into road's curves, topo lines 7,3 or less percentage grades slopes, ..

[@struck2soon]

Good video thanks. (Just to clarify ‘Boxpok’ is pronounced “box-spoke’) Question: what is the loco you feature towards the end? I notice it has an air horn atop the the boiler.

[@americansteamlegacy-yh9dr]

Hi struck2soon. AT&SF #3424 is a Baldwin built Pacific from 1919 and is on display in Kinsley, KS. As for that feature on the boiler......I agree, it looks like an air horn but honestly, I have no idea what it is. In fact, I didn't notice it until you pointed it out. I haven't been able to find any information on what that object might be. Thanks for watching!!!

[@struck2soon]

Thanks. Hopefully one of your viewers can offer clarification.

[@sharkheadism]

@@struck2soon SP had horns on some of their steam engines, maybe it was experimented with elsewhere.

[@chickengeorge_8261]

@@struck2soon I thought you were referring to the Milwaukee Road 4-6-4 Baltic at the end of the video. That loco does feature an air horn atop the boiler as you can see in the picture.

[@struck2soon]

@@chickengeorge_8261 cheers!

[@Beechnut985]

Nice

[@americansteamlegacy-yh9dr]

Thanks, Beechnut985!! Thanks for watching!!

[@keithlewis9106]

Now , how was the balancing done ? Did they calculate the side rods weight or did they have a way to run balance ? This is a great video.

[@americansteamlegacy-yh9dr]

Hi keithlewis9106. The wheels were balance as a wheel set. In other words the wheels were on the axle when the balancing was done. The weight of the main and side rods could be calculated or obtained by actual measurement, and I believe the balancing was done on a wheel lathe, I'm not sure if the wheels were dynamically balanced or just statically balanced, but they were able to achieve a rather accurate balance.

[@kleetus92]

@@americansteamlegacy-yh9dr depended on the railroad... PRR in Juniata Shops in Altoona PA had a full size engine dyno that they could run on rollers, at speed to measure performance. They would sometimes do weight tuning there as well.

[@wizlish]

Ralph Johnson goes into great detail in his book on the Steam Locomotive, and you can start there. Some British companies, notably the GWR, used high-speed dynamic balancing of drivers, particularly the mains, and built special motorized facilities to do this (the driver wheelsets were not in the frame when this was done, and for two-cylinder DA engines bobweights on the pins would be used). Advanced balancing practice can be determined with reference to Voyce Glaze's balancing book (which is preserved at NWHS). This distributes overbalance for surge in the coupled wheels, retaining only enough in the main for the vertical component of piston thrust estimated for 100mph operation. ATSF had a procedure for calculating both cross-balance and angling a slight (off the top of my head 4-and-a-fraction percent) which has been covered in online references. While it can be difficult to find the reference Stateside, the account of how the driver balancing was calculated for the British 9F 2-10-0 is particularly interesting -- these had 57" drivers without fancy lightweight rods but could run over 90mph in service...

[@porthuronerieproductions9980]

Don't mind me asking, but will there ever be a video on the experiments attempted to spoked drivers themselves in order to enhance stability, durability, and counterbalancing? While doing research on the New York Central's class L-2d of Mohawks, I noticed that the two testbed Mohawks (#'s 2995 and 2998) had webbed drivers. Another example would be the New York Chicago & St. Louis' class L-1A/B Hudsons with the center driver being webbed. After noticing, I always wondered, why was this?

[@americansteamlegacy-yh9dr]

Hi porthuronerieproductions9980. That's a great idea for a future video and will require quite a bit of research. Thank you for the suggestion!!!

[@johnd8892]

Sounds similar to the Australian production patented SCOA-P wheels. The most use currently are on the preserved and running Victorian Railways R class Hudson locomotives. Came to late to make a big impact but used in several Australian late production steam locomotives and some African ones too. Vulcan foundry in the UK would promote them on the last locomotives they made.

[@wizlish]

Those are Union Steel Castings 'Web-Spoke' drivers, and were apparently purchased and tested by a number of railroads. I believe elsewhere in this thread are some very good pictures of a PRR K4 with a Web-Spoke main and conventional cast coupled driver pair -- with a note that this also shows typical repair needed to cast spoke centers. Apparently NYC considered these 'equivalent' enough to the Boxpok and Scullin centers on the J3a Hudson's that they used them indiscriminately on the same engine in the latter years that 'appearance didn't matter but performance still did' -- see Thoroughbreds for pictures and a rudimentary discussion. I suspect NYCSHS would be a source for more detailed historical and technical description.

[@ChargerusPrime]

If ever i was to restore a steam locomotive, (by God's might and goid graves YES PLEASE!!) I'd honestly cast a whole new set of Scullin disc drivers for it. Why? Simple,theyd be easier on the rails and comparitably simpler to make than the other 3 types.. and i also don't like spoked drivers like 611 or 1218 have. Scullin drivers also allowed for much better and more precise counterbalancing than that of the others by a slight to pretty noticeable margin. The other reason being they just look so dadgum good on even some less modern engines. Gives it that sort of futuristic all American look that many people seen drawn in books and comics. And again, performance benefits.. just sayin lol.

[@americansteamlegacy-yh9dr]

Hi ChargerusPrime. I agree completely. The Scullin's kind of became my favorites as well, although the Baldwin Disks on the T-1 and S-1 duplexes don't look too shabby either. Thanks for watching and thank you for the great comment!!!

[@davidmason7765]

Thanks from NSW Australia. Our last express steam locomotives the 38 class were fitted with boxpok drivers. I knew the locomotive frames came from General Steel Castings in Granite City but not that this is where boxpok driving wheels came from. Do you know if the design was ever licensed out to be cast elsewhere ? Next time I visit one of the surviving 38s I will look to see if there is any evidence on the wheels as to where they were cast.

[@americansteamlegacy-yh9dr]

Hi davidmason7765. As far as I know the Box Pok was produced only by General Steel Castings since GSC held the patent. I remember reading somewhere Baldwin had something to do with it as well, but I don't think Baldwin ever produced Box Pok wheel centers. Great question! Thanks for watching!!

[@johnd8892]

The last express steam locomotives for Australia were the Victorian Railways R class Hudsons. After fitting Box Pok drivers to several classes they encountered maintenance access issues. Out of this the lighter and stronger Australian SCOA-P wheel was developed and fitted to all R class Hudsons made as well as the J class light consolidation. Quite a few other late era Australian and African steam locomotives used these due to their advantages.

[@davidmason7765]

@@johnd8892 Fascinating!

[@robertchapman6795]

@@johnd8892 I have just commented that R class were the only loco’s I’d seen them on. Now you have given me flashbacks to watching South African films on the condenser systems they used, and yes. S.A did use SCOA-P type wheels.

[@wizlish]

GSC had a casting facility at Eddystone as well as at Granite City -- this is why you can see 'Baldwin Boxpok' in the ATSF 4-8-4 centers

[@nathanielmeade5731]

Didn't know there were multiple types

[@americansteamlegacy-yh9dr]

Hi Nathaniel. You and me both. I was aware of the Box Pok, Baldwin Disk and Scullin, but the Universal was a bit of a surprise. Thanks for watching!!

[@quentinhilpert9606]

In the first picture of this video it shows rods down. Where the connecting rod pins are essentially not moving relative to the rail. This is a problem when the other side or other piston is on dead center. How does the engine start moving? I was stumped. He then explained the steam in this sides cylinder is PUSHING on the piston head and thus the engine. You could weld the wheels to the rail in the rods down position and the engine would still try to move forward because the steam is pushing on the cylinder head and thus the engine. Pretty cool I thought, and think, but then I'm a mechanical engineer so you know. NERD.

[@wizlish]

Look up the kinetics of a 'class three lever' which is what a rim-adhesion-loaded driver with central pivot taking the draft resultant but driven by an eccentric pin constitutes. (It is not as simple as a crank producing torque from a connecting rod as in an IC engine!) There is certainly such a thing as a 'dead center' though -- in fact there are two, which we call FDC and BDC rather than the more familiar 'top dead center' in vertical or V motors). A single-cylinder engine would stall if loaded with its piston and rod in this position. This is why two-cylinder double-acting engines have their drivers 'quartered' at 90 degree phasing, so that one side can always 'turn' the engine off dead center to allow admission on its side.

[@richardsobieck9660]

My question is, about the distance between the crank pin and the Center of the drive wheel. Was this something standard or did it vary on locomotive types? It would seem the distance would make a difference of leverage in moving the locomotive. I have never heard any discussion on this.

[@prsearls]

The crank pin radius would have been determined by the length of the piston stroke in the cylinder. Cylinder dimensions and effective steam pressure basically determined the engine's horsepower. It's actually a very complicated problem for the locomotive designers. Horsepower vs speed vs economy. Lots of compromises to balance these factors to produce a locomotive suitable for specific operating conditions (speed, tonnage, economy, low maintenance). And all done with slide rules and #2 wooden pencils (and some very smart minds)!

[@richardsobieck9660]

@@prsearls Thanks that helps a lot. I always knew that the wheel diameter makes a difference in speed and pulling power, Like different gearing. Smaller wheels mean more pulling power but less speed. etc

[@wizlish]

The crankpin radius is determined by the stroke, and there is some complexity in the 'history of balancing' as longer stroke with smaller piston diameter and hence overbalance mass came to be a sort of Lima trademark. The fun came when you wanted shorter stroke (for perceived higher speed) on a locomotive with high ihp. The great canonical example is the PRR T1, where the stroke cannot be minimized any further because the 'web' between the axle fit and the pin fit would be too thin for needed strength (see Vauclain's talk at Atlantic City in the early '40s). PRR went even further in shortening main-rod stroke by grinding the main pins eccentric where the mains were located, so the reciprocating stroke was less than the side-rod crank circle...

[@prsearls]

That is interesting. Altoona and Norfolk & Western engineers certainly produced some of the highest performance and advanced steam designs. If diesels had been delayed for another decade, it’s interesting to imagine what we would have seen.

[@tonywise198]

Box Pok wheels are still running in the UK on preserved Southern Railway "Merchant Navy", "West Country/Battle of Britain" class 4-6-2 locomotives. Originally with flat sides, these so-called Spam Cans by us young trainspotters in the 1950s, some were rebuilt in 1956 but retain the Box Pok wheels. Quite a few them (both original and rebuilds) survived into preservation when the Southern got rid of steam in 1967. They were also fitted to the Southern Q1 class 0-6-0 locos, as someone else has said. Only one Q1 survives in the National Railway Museum in York.

[@mikebrown3772]

These were Bullied Firth Brown wheels, a single disc type where the back of the apparent 'spokes' is open.

[@russellgxy2905]

Those aren’t Boxpok, but Bulleid-Firth-Brown wheels. These are single disc, but the concept of being lighter and stronger than spoke drivers is the same. They greatly differ from American discs in that they were originally designed without counterbalances! The rebuilt Pacifics received balances on their center driver after getting conventional Walschaerts gear. Easier to maintain, but the added balance made the Light Pacifics heavier on their wheels. Had the rebuild program not been cut short, a few of the Spamcans would’ve been retained to work the lighter routes west of Exeter, as the original wheels and Bulleid valve gear saved stationary AND dynamic weight

[@neiloflongbeck5705]

The BoxPok cross the Atlanic and was used on the Pacifics used on Britain's Southern Railway designed by Bullied.

[@struck2soon]

The wheels used on Bulleid’s Pacifics were not Boxpok. They were BFB wheels. (Bulleid Firth Brown.) They are different to Boxpok wheels, they do not have the ‘boxed spoke’ construction.

[@alan-sk7ky]

No consideration of the 'Bulleid Firth Brown' wheel used here in Britain on the Southern Railways. somewhere between a Baldwin disc and a 'pok'

[@BassandoForte]

There never is any yank respect for British Steam... Its like they're jealous that not only did we invent the things in 1802 - We also had THE FASTEST... Although Bulleid had nothing to do with that record, obviously... 🤣👍

[@mikebrown3772]

Not really related at all, the BFB is a single disc design without any box sections more closely related to the 'wobbly web' wheel of 1960s racing cars.

[@wizlish]

Of course, the Brits couldn't cast the BFB wheel well enough in postwar years to assure Riddles of its advantages -- all the Standards used conventional spoked drivers.

[@wizlish]

(No disrespect intended to contemporary British design, though!

[@curtiscroulet8715]

Isn't "Box Pok" correctly pronounced "box spoke?"

[@americansteamlegacy-yh9dr]

Hi curtiscroulet8715. Both pronunciations are correct. I believe "box spoke" was the first but over time was shortened to "box pok". Thanks for watching!!

[@indridcold8433]

The steam era will return. When atomic fussion is fully perfected, steam will be in all machinery again. An automobile could run on half a kilogram of Einsteinium, a fussion reactor, and water for over 250 years. A fussion reactor would likely see several automobiles before all fussion stops. Fussion stops when the Einsteinium degrades into Carbon 12. The Carbon-12 can then be used for fertiliser, or just discarded as almost everything in nature has carbon in it. The harmless carbon will absorb back into plants and animals, like the harmless chemical it is in nature. As for Einsteinium, a top secret method to manufacture it from spent nuclear fission fuel has already produced enough of it to power the planet for about 750 years. The only issue is making the fussion reactor. One exhausted fission reactor's worth of fuel, will have enough exhausted fuel in it to make about 1000 fussion reactors worth of Einsteinium. There are currently some issues regulating the enormous amounts of energy produced from a fussion reactor. Once this is, solved, the world will never be the same again.

[@BassandoForte]

No Bulleid wheels..?? Shame on you... 🤣

[@americansteamlegacy-yh9dr]

LOL!! I'll better next time!! Thanks for watching!!

[@BerlietGBC]

Very good but you missed on out en.wikipedia.org/wiki/Bulleid_Firth_Brown_wheel#Design