This photo recently came through at railpictures.net

http://www.railpictures.net/viewphoto.p ... 5&nseq=110

They are already doing work in the new facility.

I did not know you could do that with the wheel still on the engine. I would be afraid of burning up all the surrounding machinery.

Sweating the tires off of the wheels without removing the wheel sets from the locomotive is not unheard of, especially when you only need to deal with one or two tires. We replaced two tires on the front truck of our three-truck Heisler in this fashion. You just have to make sure that the diameter (aka the "tape") of the new tire(s) matches the others or you'll have issues (especially true with geared locomotives). In the case of the #700 at Portland, I would be more concerned about that intense heat so close to the fresh concrete floor.

Brian Wise
General Manager
Mt. Rainier Scenic Railroad

Being a former machinist I was curious as to the amount of interference fit used. A quick google search yielded this:

http://www.ehow.co.uk/how_8041051_apply ... heels.html



I find this to contradict my judgement.

A 0.055" intereference fit for a 24" wheel and on a 72" wheel yield vastly different stresses in the tire.

A rule of thumb I was taught for interference fits was 0.001" per 1" of diameter. This will give an acceptable stress level in the tire. Thus a 24" tire gets 0.024" interference and a 72" tire gets a .072" interference.

Steve

theres a good point there as concrete may hold trapped moisture, heat it up and it expodes away.

Work floor around a steam engine or hot work should be a moisture cured material.
er a de-moistured cure...

I think this technique is your fast fix get going deal, if it creates issues of minor imperfections its a job for the fast fix and do it right later.

Reminds me of some of my soldering work, I find using a very hot iron works better on HO rail because the heat is very hot first, you heat your focused ares rapidly, hit the solder on fast, and pull away fast and you won't melt nearby plastic. Use a lower power iron, you take forever heating and you start melting nearby plastic ties.
Just a model railroad comparison but the laws of nature are governed the same way big or small.

Same thing about resistance soldering as you heat the desired area only.

The 1000 weight cylinder oil in the lubricator above should pump now. ;-)

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Fascinating. I wonder why the increase with the larger diameters. Also, how did you determine when the tire was hot enough and expanded enough to assemble?

I can't imagine inside micrometer used on a very hot tire.

Steve

Just to make sure nobody misses the point, observe the tolerance range in the AAR table -- it is NOT symmetrical about the 'desired' shrinkage value.

Regarding adjacent components, gas not premixed with air via a venturi like you have on your stove or furnace burners, and burning with a mostly yellow flame as you see in the photo, isn't burning all that hot. Premixing with air would result in a much hotter flame that would be blue in color.

Maybe a simple venturi wouldn't work with a huge ring burner like that but it's also very likely that a hotter flame would not be desirable. With the less intense flame the heating is more gentle, slow, and even, and also reduces risk to nearby parts.

Steve

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there are hand held gauges with wafer varying sizes metal you prod into openings to test opening thickness, but .000001 whatever is...er...THIN! if applying heat you'll prolly melt them.
Really, you do your pre-measuring, some calculations, heat it up and pound the tread on. I'm sure all the kinks have been ironed out since this has been done since the early days of steam.

Film Last of the Giants of the UP Big Boy shows this process (from the pic above)

its the same theory like heating rail, the longer the piece, the longer the expansion,
(in the hot sun) its just your metal is around a circle, more metal pushing out.