Steam & Excursion > 611 drivers question

Why did the J's have spoked drivers rather than boxpok or disc, especially considering that the J's were considered by many to be the ultimate steam design?  A 12/29/03 TO thread indicates that boxpok and disc were better than spoked.

Steve

Because the boys in Roanoke knew something about balancing locomotives.

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SGillings Wrote:
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> Why did the J's have spoked drivers rather than
> boxpok or disc, especially considering that the
> J's were considered by many to be the ultimate
> steam design?  A 12/29/03 TO thread indicates
> that boxpok and disc were better than spoked.

If you look closely at the J's drivers around the crankpins, they do in fact share some characteristics with disc drivers. But in a disagreement between TO posters and N&W's locomotive design staff, I know where I'd place my money.

"Who else could pull 80,000 pounds of tractive force out of a 4-8-4, then roll the same engine at 110mph just to show the critics that her 70-inch drivers were no handicap in the flatlands?

Why, the more you compared, the more embarrassing it became. Baltimore & Ohio's marvelously photogenic 2-8-8-4 never meant quite the same thing to me after an analytical friend pointed out that N&W's 2-6-6-4 produces virtually the same drawbar pull with more than 47 tons less engine and four fewer drivers.

You couldn't tell Roanoke anything. Long after everybody else gave up on the Mallet as an impossibly slow beast of burden, N&W kept on tinkering with the design it had once loaned to other roads in the guise of the USRA compound 2-8--8-2 until it had that ideal mountain engine, the Y6.

For that matter, the crowd complained of the turnaround time on steam while N&W rearranged its engine terminals to groom a Y6 in 1 1/2 hours or less; the trade papers exclaimed about pulling big passenger mileages out of diesels as N&W's J's rolled off a steady 15,000 miles each per month; and the steam diehards said the future lay in poppet valves and duplex drives, ideas which Roanoke pointedly passed up.

Roanoke had a way of obtaining from orthodoxy what others strove for in gadgetry." - David P. Morgan


 



Edited 5 time(s). Last edit at 05/22/15 15:07 by johnacraft.

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Because they could cast them in their own foundry.

They would have had to buy Boxpok, LFM, Scullin or others.

"Who else could pull 80,000 pounds of tractive force out of a 4-8-4, then roll the same engine at 110mph just to show the critics that her 70-inch drivers were no handicap in the flatlands? 

Why, the more you compared, the more embarrassing it became Baltimore & Ohio's marvelously photogenic 2-8-8-4 never meant quite the same thing to me after an analytical friend pointed out that N&W's 2-6-6-4 produces virtually the same drawbar pull with more than 47 tons less engine and four fewer drivers. 

You couldn't tell Roanoke anything. Long after everybody else gave up on the Mallet as an impossibly slow beast of burden, N&W kept on tinkering with the design it had once loaned to other roads in the guise of the USRA compound 2-8--8-2 until it had that ideal mountain engine, the Y6. 

For that matter, the crowd complained of the turnaround time on steam while N&W rearranged its engine terminals to groom a Y6 in 1 1/2 hours or less; the trade papers exclaimed about pulling big passenger mileages out of diesels as N&W's J's rolled off a steady 15,000 miles each per month; and the steam diehards said the future lay in poppet valves and duplex drives, ideas which Roanoke pointedly passed up. 

Roanoke had a way of obtaining from orthodoxy what others strove for in gadgetry." - David P. Morgan 

What a great quote.  Thanks (again) D.P.M.

God, could DPM write an evocative paragraph...

Makes one yourn for someone who could convey a picture with words. Modern journalists have lost that touch. B

Brendan611 Wrote:
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> Makes one yourn for someone who could convey a
> picture with words. Modern journalists have lost
> that touch. B

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Edited 1 time(s). Last edit at 05/22/15 07:01 by kurt765.

A couple of possibilities beyond simply that they could make their own:

Spoked wheels are lighter than solid wheels. Mass is not your friend on a rotating object like a wheel if you can avoid it. Of course you need a counterbalance weight and some extra strength around the rod connection, so the wheel can't be all spokes.

A disk wheel has more iron so more thermal mass. I would not be surprised if a spoked driver was less likely to throw a pressed-on wheel rim than a solid driver under similar braking conditions.