Steam Locomotive drive wheel question

[Berk765]

If you see steamer drive wheels that look like they have large holes drilled in them instead of wheel spokes what is their type called?

[arkansasrailfan]

There is a name but The ones youre talking about are Box Pox drivers(sp)I think, but I will go and consult my steam cyclopedia(Out of print)

[BillyDee53]

Either Boxspok or Scullen disc...depends on the shape of the holes.  (I'm sure there's more to it than that).

[BillyDee53]

Boxspok wheels have teardrop-shaped holes; scullen disks have round holes. 

[selector]

The correct spelling is Boxpok.

[VAPEURCHAPELON]

The correct spelling is Boxpok.

As well as Scullin, not Scullen.

[Berk765]

My favorite style is the Skullin disc. Those are just beautiful.

[SealBook27]

Was there any purpose to these designs, other than to make the wheels more modern looking?

[Berk765]

My theory is that they were designed this way so the wheels have much better balance so the engine could run at higher speeds with fewer vibrations.

[VAPEURCHAPELON]

Was there any purpose to these designs, other than to make the wheels more modern looking?

To make the wheels more modern looking was NOT a reason for their existence (but it was an appealing secondary effect). The idea was to find forms of wheel castings being more resistant to deformation thus reducing the need of returning the tires considerably. Though these wheels look more massive, they were even lighter than the classic spoked types.This is because the discs are very thin and the box pok type is hollow between its two discs.

[AltonFan]

I believe that Scullin and Boxpok drivers were also supposed to be easier to counterbalance than spoked wheels.

[Dr Leonard]

I am not sure about the technical aspects of this question, but my understanding is that the Boxpok (meaning "box spoke") drivers were typically the ones with the "teardrop" shaped holes and the Scullin were the ones with the round holes. But some Boxpok drivers also had the round holes, so I am wondering whether the shape of the holes really identifies the manufacturer. And don't forget that there were also Baldwin "web spoke" drivers, as on the L&N 2-8-4s and others. Maybe it's best to just use the general term "disk (or disc) drivers" for the more modern non-spoked types.

[timz]

But some Boxpok drivers also had the round holes

Can you find an example?

(Now that I think of it, some of the NP 4-8-4s might be an example. Were there others?)

[VAPEURCHAPELON]

But some Boxpok drivers also had the round holes

Can you find an example?

(Now that I think of it, some of the NP 4-8-4s might be an example. Were there others?)

You are thinking of NP's A-2 #2650 - 2659. Other engines were C&NW class H-1 4-8-4, as well as other C&NW steamers like the rebuilt E-2 series 4-6-2s and some 2-8-2s. Some of the ERIE 2-8-4s had them as well as some CN and GRAND TRUNK 4-8-4s. Some of the rebuilt MP P-73 4-6-2s got them as the main driver. T&P 2-10-4s got them as a couple of them were completely modernized with light weight running gear. There were probably other railroads which used that type of wheels from time to time, too.

But the holes of this type of wheel were NOT exactly round. Almost - but not exactly.

I have to look at a cyclopedia, but I still think that the main feature of Boxpok wheels seperating it from most other types is that they had two discs per wheel with connections once called "box spokes" - hence the simplified name boxpok. I believe that Scullin as well as Baldwin type wheels only had one disc per wheel. But there still were other types I could not identify like NYNH&H I-5, or NYC "Mercury" 4-6-2s, or Santa Fe's rebuilt 3450 class 4-6-4s as well as some Pennsy types. These seem to be developments from these roads alone.

[Big Wheel Driver]

When spoked driving wheels are cast the spokes have a tendency to crack where they join the hub, as the casting cools. Boxpok drivers don't have this problem.

 Regards,

Malcolm.

[Anonymous]

for a picture of a baldwin disc driver go to;  youtube the city of new orleans-willy nelson by nlimonge, the slide at about 1:46, you can see what they look like and even see the letters at top of wheel cast  BALDWIN DISC.

[VAPEURCHAPELON]

for a picture of a baldwin disc driver go to;  youtube the city of new orleans-willy nelson by nlimonge, the slide at about 1:46, you can see what they look like and even see the letters at top of wheel cast  BALDWIN DISC.

Don't you could provide a link?