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Some thoughts on track gleaning and wheel diameter and flanges

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Some thoughts on track gleaning and wheel diameter and flanges
Posted by Richard 4x8 HO on Thursday, January 7, 2021 11:33 AM

I just read an article on gleaming track. There were some posts mentioning cleaning the wheels too.  I am not an expert on prototype trains, but I had a detailed conversation with an expert on train tracking and wheel details.

First Point: The wheel diameters should be exactly the same diameter. Both wheels are one piece with the axle, in that they do not rotate independently. If one wheel is smaller than the other, the wheels will have to scuff as they rotate, due to the different circumference at the rolling diameter of each wheel where it is touching the rail. To explain, exagerate the diameters of one of the wheels, lets say one is 30 inches in diameter, and the other is 29 inches diameter. In one rotation of the axle, one wheel will move forward by the length of its circumference (Pi x Diameter) 3.14 x 30 = 94.2 inches. The other wheel (Pi x 29 = 91.06 inches. There would be much scuffing of the wheels to compensate for the difference of distance travelled per one rotation of the axle.

Second Point: The wheels are ground to a small taper, smaller toward the outside edge of the wheel. This is what keeps the wheels and axle running central to the track. (the flanges are not what keeps the wheels on the track. If you look at prototype wheels, especially well worn wheels, you will see wear on the centre of the rolling surface of the wheels, and NO WEAR ON THE FLANGES!) The taper of the wheels changes the rolling diameter of the wheels if the wheels/axle shifts side to side while rolling along the track. If the axle moves to the left, the right wheel rolls on a smaller diameter, (due to the wheel taper) while the left wheel rolls on a larger diameter, (also due to the wheel taper). The axle will SELF-STEER along the track due to the difference in the rolling diameters of the wheels.

Whew!

Richard 4x8 HO

 

 

 

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Posted by SeeYou190 on Thursday, January 7, 2021 6:42 PM

Welcome to the Model Railroader magazine dicsussion forums. Your first few posts will be delayed by the moderators for approval, but that will end pretty soon.

Please stick around.

The tapered tread also allows one wheel to be a slightly different diameter than the other.

The axle will just shoft slightly to the side to compensate

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by Lastspikemike on Thursday, January 7, 2021 6:49 PM

Not following this different diameter point.

In order for the axles to run in the centre of the gauge the taper on the tread must be the same for all wheels. If one wheel is smaller, even slightly, then that wheel will scuff.

The mismatched sizes will also drive the axle sideways causing one wheel to continuously run on its flange.

Alyth Yard

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Posted by BigDaddy on Thursday, January 7, 2021 7:06 PM

Are MR wheels actually machined?  If they are, it is not turn of the century machining where you have a lathe, a machinist and a micrometer.  It is all done by machines and mass production.

Those tolerances are going to have to be good enough.   It's going to be a cold day in HO Land before I measure every wheel on my rolling stock

You second point is totally correct.  I'm just not convinced your 1st point is significant issue on current production.

Welcome to the forum.

 

Henry

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Posted by SeeYou190 on Thursday, January 7, 2021 7:29 PM

Lastspikemike
In order for the axles to run in the centre of the gauge the taper on the tread must be the same for all wheels. If one wheel is smaller, even slightly, then that wheel will scuff.

If one wheel is a slightly different diameter the axle will shift to the side. This happens automatically, just like the "steering" in curves.

When shifted to the side, the tire surface taper "makes" one wheel larger and one wheel smaller.

If you put a 33 inch and a 36 inch diameter wheel on the same axle, this will not work because there is too much of a difference. If you put a new 33 inch wheel on the same axle as a worn 33 inch wheel, you can see how it happens.

Having a test car with a clear plexiglass floor reveals all kinds of wheel/track magic.

BigDaddy
Are MR wheels actually machined?

Some high-end wheels supposedly are. I use Kadee wheels almost exclusively, and they are not machined.

The RP-25 wheel profile can be cast well enough for our needs.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by Overmod on Thursday, January 7, 2021 7:52 PM

To learn about the full-scale wheel/rail dynamics, I'd start with finding and reading the Wickens papers from 1965-6 that deal with railway vehicle stability at high speed.  They contain answers to the questions being asked.  There has, of course, been considerable work since then, including analyses of why independently-rotating wheels in a 'wheelset' perform relatively less well than a pair rigidly connected ... even when, as on current HSR, the wheeltread is only very shallowly coned or in fact cylindrical.

I am amazed that it is possible to form a HO wheelset with both an accurate RP25 contour and perfect concentricity/zero runout on an axle as a routine and cheap fab operation.  I think there was a time when QC was not as good as it is today in those respects.  But now...

Meanwhile, I have suspected since I was very young that the 'as-delivered' railhead profile of commercial drawn nickel-silver rail probably looks almost nothing like the physical railhead and gauge-corner profile of actual rail -- new or worn -- against which the coned wheel and fillet in real wheels work.  In my opinion a good track-gleaming method should form some analogue of these as it burnishes the actual metal finish.  Most published methods do not explicitly do that.  But as noted the physical effects of 'getting the right shape' likely would matter comparatively little at model scale, with model engineering detail design, involving model-scale physics. 

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Posted by mbinsewi on Thursday, January 7, 2021 8:00 PM

I buy wheels from Intermountain, 100 sets at a time.  I'll leave the details to who ever does Intermountains wheels.

I've NEVER used a micrometer to check the wheels, other than to determine what size I need.

I don't run a 1:1 railroad, I run an HO (1:87) scale MODEL railroad.

I don't see how either point 1 or 2 have anything to do with model railroading.

As far as track gleaming AND a an inspection car with a clear plastic bottom, I have some hidden track, so neither are used, or done on my track.

Gleaming and an inspection car only work if you can walk around your railroad, and see ALL of the track.  I can do neither.

I run a track cleaner car about once or twice a year.

I clean the wheels on my locos when I notice some black gunk build-up.

Welcome to the forums.

Mike.

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Posted by rrinker on Thursday, January 7, 2021 8:32 PM

 6:45 mark of this video of Richard Hammond's Engineering Connections show has a great visual demonstration of how trains go around curves, using some metal shapes and LGB track.

  https://www.youtube.com/watch?v=xA4aaSzqT9s

                                         --Randy

 


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Posted by BN7150 on Monday, January 11, 2021 12:14 PM

The video experiment introduced by Randy (rrinker) can also be experienced at the railroad museum, which has the longest history in Japan. That's right. This action is common sense in the world.

However, HOWEVER, the fact is different. Why did GE (Steerable Trucks), EMD (HTCR) and GATX (Barber-Scheffel Trucks) adopt the steering trucks? Conical tread is not useful on sharp curves. Works on sections that probably run at speeds above 50 mph, gentle curves which radii above 2000 feet and straight lines. That is, in models it only looks good. Is there anyone here who can understand what I mean?

I posted this theory on my blog 8 years ago (How do trains turn in curves smoothly?), but it seems that only 10% of readers understand it. Since this level is by my mother tongue Japanese, explanations in English, which I am not good at, will be useless.

Kotaro Kuriu, Kyoto, Japan

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Posted by SeeYou190 on Monday, January 11, 2021 1:53 PM

Kotaro, that was a great video, and an excellent display.

I have visited many railroad museums in the United States and never seen a demonstration like that one.

That would fit in perfectly in the Chicago Museum Of Science And Industry.

Thank you.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by BigDaddy on Monday, January 11, 2021 5:39 PM

Kotaro you are doing pretty darn good in English 

Ikimashou is all I can muster in Japanese.  Keep posting

Henry

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Posted by BN7150 on Wednesday, January 13, 2021 12:48 AM

Thank you for your encouragement.

This is a demonstration of the Kobe City Youth Science Museum. Many others are installed in various places. The mechanism is like an armillary sphere that explains the "Geocentric theory". This makes it possible to perfectly explain the perceptible movements of celestial bodies. All the Japanese railway experts I asked were "Geocentric theory". All public enlightenment books and many specialized books are "Geocentric theory". A university professor even made a website and insisted.

On the other hand, The "Heliocentrism" can only be found in books on wheelset-track dynamics. I have never seen both the "Geocentric theory" and the "Heliocentrism" in the U.S. books. It takes tremendous effort to prove the "Heliocentrism". Someday Galileo should appear.

I will ask again. Is there anyone here who knows that conical tread don't work on sharp curves?

Kotaro Kuriu, Kyoto, Japan

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Posted by Overmod on Wednesday, January 13, 2021 7:38 AM

Pam Long pointed out to me that you could get arbitrarily close to proper celestial mechanics with sufficiently complicated Ptolemaic epicycles... if you dismissed the question of what the epicycles 'turned' on.  This is akin to duplicating any waveform with 'enough' sine waves...

There are key differences between prototype and 'model' stability, a major one being the 'correct' action of needle-pointed axles -- including when 'steering' into curves and not just load-bearing.  It is my personal opinion that until there is careful modeling of railhead profile at model scale, much of the 'taper centering' will be accidental at best, and that before we take up the issues of flange wear.

I have always, a bit naively, thought the root and flange fillet of RP25 far more important in model guiding than a 'counteracting' mutually-opposed running taper, or subtle effects of differential rotation, as in the prototype.  As you noted that applies on much longer-radius curves than found in even extreme cases of practical model layouts... and with proper spiraling and attention to vertical curvature, too.

I had something of an epiphany from Dave Goding, who after long work on very successful steerablr truck design has come to recommend against using steering levers at all in a zero-rigid-wheelbase truck -- I will not put words in his mouth regarding the reasons.

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