On the 1:1 prototypel how deep are the flanges typically? I realize there is much wear, and that the treads are re-profiled, new tires put on ect., but in inches how deep(tall) is the flange. I am just looking for a figure plus or minus an eight or so. I also realize the tread itself is tapered at about a 2 degree angle, and the radius between the tread and the flange makes it hard to measure. I was looking at the FRA and other websites but could not find the answer.
Thanks
Paul
The actual figure will vary between different railways, but as an example, the railway I work for here in Australia allows flanges to be a mimimum depth of 24.93mm, and maximum of 28.07mm. So the figure is very roughly an inch. Our wheel standards are derived from US AAR standards, so that figure will be very close to what US railroads use. Cheers, Mark.
Mark,
Thank you very much. That is exactly the information I was looking for.
Paul
Mark’s information was correct. The North American standard is for 1"-deep flanges, plus or minus 1/16". - Andy
It’s a scary thought riding a typical VRE train to work that 1" inch on about 64 wheels is all that is keeping the train on the tracks. I’m sure someone can describe the physics in detail, but it’s still scary; esp. since the train bounces up and down a lot.
I wonder how much contact the flanges actually have with the rail on straight track. I was under the impression that contact is minimal, and engineered to be that way.
What keeps the train centered between the rails is not so much the flanges as the 3 degree taper in the wheel tread. On reasonably well maintained track with reasonable curves the flanges won’t contact the railheads at all.
To understand how that works, just lay a paper cup on its side and push it. It will roll in a circle, not a straight line. If you can connect two such shapes with an axle and roll them down two parallel rails, they will center themselves so that the contact lines have identical radii and circumferences. A wheelset has two identical conical forms, and will roll down the track on identical contact lines on the conical wheel tread, not on the radius that forms the tread side of the flange.
On a curve, the outer wheel moves away from the center of the rails and the inner wheel moves toward the center. That establishes two new contact lines, the outside one having a longer circumference than the inner one. If the curve is so sharp that the conical shapes cannot absorb the difference the outer wheel flange will finally contact the rail - with a screech that can be heard by anyone within several hundred meters. That’s where the prototype will install flange greasers.
FWIW, note that tie plates impart a 3 degree slant to the rails, so the wheel will make contact across the entire railhead. That reduces wheel and rail wear, and reduces the kind of stress that can lead to transverse fractures.
If memory serves me as a wheel shop foreman (more decades ago then I care to count) wheel flange was close to 1 inch high when new or re-profilled, and not to be over and condemed at 1 1/2 inch in height. Dont confuse this with flange thickness as a thin flange was condemed at 1 inch in thickness, as this thinner flange could split a swich
Height is determined with a wheel gauge that is measured from the back (flat back) to the center of the 1 in 20 taper tread.
As .the rail wears the taperd tread, it will in time become concaved. Again measuring the wheel in its worn condition, the gauge drops down further as it rests in thes center part of the tread where the metal is worn away, as we now look at the gauge the flange is higher, compared to the tread, thus it will be condemed at 1 1/2 in height. ( the flange did not grow in physical size, as it is related in measurment to the center of tread.)
Clear as mud…LOL …John
Flange depth is also a consideration when rolling through a switch or turn out. A flange too deep can cause a condition known as “high flanging” when the truck rolls through a switch’s frog. It’s possible that the wheel set could actually bounce off the rail. at which time it’s return to the rail or the ground can become an almost 50-50 proposition. Some model manufacturors made their flanges quite deep several years ago. This situation has much improved as track is much closer to scale, and the flanges on our rolling stock and engines has followed suit.
As Andy Stated above the flange is about 1 inch. Kevin
As Tomikawa says it is not the flange that holds the rail on wheel on the rail. The physics of four cones back to back (thick ends together) in two pairs in a fixed frame is what keeps a rail vehicle on the track. that and the vehicles weight.
Suspension also comes into it. Shocks imparted by rail joints and (if things are wrong) parts of switches are dampened and absorbed by the suspension. This acts against a vehicle being bounced off the track.
Far more scarey than the smallness of the flange is the actual amount of wheel/rail contact… which at any one times for each wheel is something a bit less than the area of the palm of your hand.
You think that that is small? it’s changing constantly as the wheel rolls… at speeds up to 125mph and even 140mph in some places. Now that is “interesting”.
When curves are encountered the flange may be deflected with the movements of the cones as Tomikawa says with the resulting squeals of steal on steal.
Centifugal force also comes into this and G forces. The thing that you do not want is for the G force on the outer wheels on a curve to become zero or less. If that happens you go straight on instead of round the curve.
How often is the measurement made? Is it routine maintenance, or the result of observation or an occurence? Where does the car or locomotive get sent for the measurement? How is the measurement done (manually, by machine, high-tech laser/ computer,…)? How much down-time? Tolerances? More info!
Sorry for the Journalism 101 approach, but I think this is really interesting stuff, and I obviously don’t know anything about it.
Thanks.
In the UK there are stock inspections all over the place all of the time. Most times anyone not informed wouldn’t know they were going on. Passenger stock gets examined at least once every 24 hours.
Apart from the modern technology, which often does things automatically, examiners learn what to look for… and where they don’t already know a fault they know what looks different… the trick is to pick up on it and not just breeze by.
It’s the same as when a cop walks down the street. He/she can spot regular trouble. A wrong car will stand out. When he wanders into his doughnut bar (she wouldn’t she’s watching her figure)(and very sensible she is too) ([(-D]) he has to catch on to a robbery going down fast not get blown away.
There used to be “wheel tappers”. These men (it was a male job back then) examined more than just wheels but they tapped each wheel with a stick or hammer and knew what it was doing /how it was by the sound. they could do this in a busy/noisy yard or station. Experience was the big thing.
Also, anyone can hear a wheel that has got damaged with “flats”… it thumps along. Bad ones can be heard miles away.
Speaking only for my railway, passenger stock is inspected daily before entering service. This includes a visual inspection of wheels and flanges by the brake examiner if in a depot, or by the train crew if in a stabling yard. A more thorough inspection is carried out every 28 days, which includes the examiner using a simple sheet-metal profile gauge to check for wear. The 90 day inspection uncludes a more detailed examination using a so-called profile caliper, which actually measures wear. Originally this was a mechanical device, but these days the fitters use a small electronic gadget which gives a printed copy of the measurements. Cheers, Mark.
I’ve heard it said that if our models had truly prototypically-sized wheel flanges we couldn’t keep anything on the track.
That chestnut probably originated as much in response to our generally sloppy (when compared to the prototype) trackwork as to unprototypical wheel profiles. The RP for Proto:nn modelers lists a scale flange depth of about 1.2 inches, which is very close to prototype, as well as a 1:20 tread taper. Of course, Proto:nn trackwork requires much more effort to install and refine than flex track.
Consider also that our models are unprototypically light, which contributes to derailments regardless of flange depth. If mass scaled properly, we’d have fewer derailments, but it would be difficult to put anything on the track, and once there, our can-motor-powered locos would be unable to move it.
Not in my experience. I have some 1/43 scale models with dead-scale tyre profiles and flanges. Providing that the track they run on has been properly laid, they run beautifully.
I have always been told that the wheel-rail contact area is the size of a dime.
When the flange of the wheel contacts the outer rail in a curve, the wheelset is slightly torqued or twisted. It then snaps back to normal. This happens continuously as the wheelset tracks around the curve, and at a high frequency; which causes the sounds that we all hear.
While zero G on the outer rail is bad, it can happen only when the train is moving slowly. What’s really bad is the inner rail having zero g. This means the whole train rotates to the outside of the curve around the rail, i.e. ends up on its side to the outside of the curve. This is known as the overturning speed. And it requires the train to be travelling much faster than the normal design speed.
DAW
Um… I don’t think so…
If I recall correctly a dime is about the size of our old sixpence. If the contact were that small a wheel would not spread a penny (old/real style - or modern 2p which is almost as big but not as thick) out to about twice its original size. My Brother still has one that he had squashed as a scout at Nine Elms Loco Depot back in the 60s. (In thos
Do you have any evidence to support this claim?