changing a tire on a Steam engine

"The flow of oxygen is cut back to produce a bluish flame..." Oops...

john wrote in news:Ke- dnbNWhacJBdnbnZ2dnUVZ snipped-for-privacy@nni.com:

Are those the wheels you machined a while back?

We cut the bores in the tires.

John

Very interesting. 55 thous for heat expansion seems a lot, but that is a LARGE wheel.

Years ago, my wife worked in production scheduling and raw material ordering. The railroad told her the shipment would be late because the railcar had a flat tire. We always said this was pure BS, maybe not.

Karl

Well worth the look!

Thanks, Wes

A flat tire is very true. Lock the wheel and skid it along the rail a couple miles and you get a long flat spot. Next time you are stoped by a train, listen, you can hear a flat wheel as it rolls and pounds the track at every revolution

Howard Garner

The bore on the tires was about 67 inches. A normal interference fit usually run between .001 to .0015 thou. per diameter inch.

Yup they get flat tires too. If you ever look at a railroad wheel up close you will see that the profile is not flat but it tapers larger toward the inside flange. This is done for a reason. When the train goes around a curve the outside wheel has to travel a farther distance around the curve. The centrifical force pushes the wheel to the outside and the effective diameter of the wheel gets larger for the outside wheel and smaller for the inside wheel. Remember the wheels and axle are one solid unit but the distance per revolution is larger for the outside wheel and smaller for the inside wheel. This keeps the wheels from skidding and also prevents the rails from being worn out too soon.

John

John...That was very interesting, Thanks for sharing that! Jim

I can still see my uncle Frank with a bar prying off a tire at the Pitcairn enginehouse with that ring of flame ...must have been only 2 or 3 then ...... God Bless .... Tom in Belle Vernon PA

And the Steamtown site says that they "sweated" the old tire off. But why wouldn't they just cut it off? Were they somehow reusable? It seems unlikely that they could re-tread it, so to speak. Bob

And maybe even more importantly this same tread geometry causes the centering of the wheelset on tangent track thus keeping the wheel flange away from the rail. Theoretically the flanges never touch the railhead on the straight.

Paul

On Fri, 11 May 2007 22:46:34 GMT, with neither quill nor qualm, "Karl Townsend" quickly quoth:

IIRC, they used about 1/4" interference fit for the tires on wagons. They'd build a nice oak fire around it and when it was red hot, hammer it onto the wheel and quench it with water. Dem puppies STAYED on. _The Wheelwright's Shop_ by George Sturt is a great read if you're interested in such stuff.

That's why I've never locked up my tires when doing emergency stops. It puts flat spots on the tires (rubber or metal, huh?) Besides, you can stop more quickly if you don't lock 'em up.

- Metaphors Be With You -

I've read somewhere that maximum traction for braking is at 10% slip in rotation. When I had a motorcycle, I often practiced braking and I could really hear those tires talk to me when I was balancing on the edge of lockup. (Note make sure nobody is behind you :) )

Wes

"John" The centrifical force pushes the wheel to the outside

uummm...nooo....the wheel wants to go straight, the rail pushes inward toward the center of rotation. There is no such thing as 'centrifugal' force, only centripetal. Think central force motion........ Phil Kangas

Phil, Forget-it. I went down this road a few months ago and just gave up after many, many rounds of posts. There are just WAY too many physics "experts" on the net to get anywhere with the lecture on circular motion. :-) ...lew...

You guys just don't get it so I will explain the forces in detail so you can go home educated. Yes, the centrifugal force is considered an imaginary force outward from the center of the radius of arc. It is actually the ma in the F=ma for the continuos acceleration of the mass to the center of the arc.

In equilibrium, the forces are balanced but in this case the centripetal force is prodices a constant acceleration toward the center of the radius. The equivalent 'centrifugal force' is used. There is an actual force outward on the rail. The outward force on the rail would be equivalent to the 'imaginary' centrifugal force.

John

are

Yah, you are right, Lew. I'll let it go but it bugs me. ;>) At least one other guy out there feels as I do about it, Thanks. Phil

On Sun, 13 May 2007 02:26:30 GMT, with neither quill nor qualm, Lew Hartswick quickly quoth:

Could this be referred to as a "circle jerk", lew? ;)

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