This forum is dedicated to Riding Scale Railroading with propulsion using other than steam (Hydraulics, diesel engines, gas engines, electric motors, hybrid etc.)
However, the standard omits some fine details. One example is that the standard does not specify HOW to measure the flange width, either on a drawing or on a physical wheel.
Bill Donovan of Real Trains Inc has proposed a method that can be used for measuring the flange location and width on CAD drawings. The proposal can be found here:
This proposal is not intended to change the current IBLS Wheel Standard, but to serve as an aid to those using the standard to draw construction diagrams.
I invite you to review this proposal and provide your constructive feedback on this thread, assuming Harold approves (He does!)
I believe that Bill is not reading the drawing properly. The width of the flange is not taken at the theoretical intersection point of the flange taper and the wheel taper. The flange width is measured from the wheel back to the gauging point on the flange, which is the point at which the fillet radius and flange tip radius (for lack of a better term) intersect, or at the point in which the fillet radius is tangent to the flange taper (depending on the tolerance used) If the flange were measured at the theoretical intersection point of the tread and flange tapers, one would end up with a thin flange. As I see it, and as I have been led to understand, as long as the fillet and flange tip tolerance has been adhered to, the flange width is measured at the "gauge point" (the point where these two radii meet or almost intersect). I once made a very blown up drawing of a model flange using all nominal dimensions shown on the IBLS standards sheet and found that the amount to flange taper on the rail side of the flange is very small, almost non existent. With full size railroad wheels, a "gauge point" is called out on standard drawings as a point that is 3/8" in from the highest point on the flange. This is where the flange width is measured. Since our model flanges do not follow prototype profiles exactly, this point is a little vague. I measure the flange width on my wheels at the point where the fillet radius starts (tangent point) on the flange taper.
More feed back is welcome
Bruce Mowbray
Springville & Southern RR
TMB Manufacturing & Locomotive Works
In a related question (i.e. hijack) the proposed IBLS standards call for the flange width and depth to be 0.156" and 0.187" maximum respectively for 1.5" scale. I'd be interested in knowing whether others have experimented with deviating from these nominal dimensions, especially by reducing the flange depth. I know that prototype RRs used a smaller flange width and depth on the second and third drivers of an eight-coupled loco rather than using blind drivers, for example.
The point that you state the measurement is made to is the point that is now used and is the point that I refer to in my discussion. I am not incorrect in this.
The point that I am trying to make is that defining width to a point where a line on an angle is tangent to a fillet between that line and another line that is also at an angle is difficult to draw exactly. Especially after also considering the tolerances on each of these three items.
Measurement of this point is extremely difficult to do accurately on the finished item. With the availability of CNC equipment measurement is less important than the initial drawing in CAD.
I am proposing that the width be defined as the point where the line defining the tread surface would meet the line defining the flange side which is inside of the metal of the wheel. This simplifies drawing.
I am not porposing that this change not be done without changing the numerical value of the dimension specification to result in the same size of the flange as is now used. This would not produce a thinner flange.
Changes in these values can get extremely complex unless you are laying new track to match your changes. They all interact.
The flange width is a maximum so that when the wheel goes through the flangeway of a frog it will fit within the width of the flangeway. This value is what is recommended for new wheels. With wear the flange becones thinner which allows the wheels to move sideways a greater amount. This must be accounted for in frogs and in the position of guard rails.
The flange height should actually be specified as a minimum. The work done by the IBLS 50+ years ago did this but over the years some errors have been made in updating the various tables. This value is also for new wheels. With wear the flange actually almost always becomes higher. This is due to the fact that the wheel tread surface wears down faster than the outer edge of the flange, making is higher above the tread.
If you change the flange sizes you can still produce a wheel that will operate correctly if you change the trackwork to match it.
I use the standard 0.156" thick flanges on the 1st, 4th, and 5th drive axles on my 2-10-0. the 2nd drive axle has a 'thinned' flange on it, about 0.100" thick. The back-to-backs are the same. The middle (third) driver is completely blind, per the prototype. I don't worry about the flange being too weak or breaking, because it is part of a steel tire that I put on there. I did it to help the locomotive go through curves easier. I figured if the locomotive builders did it, then it should work out OK. it's been that way for 2 or 3 years now, and no problems.
Here is a copy of each flange, using different parameters using nominal dimensions.
On the profile 1 drawing, I used the IBLS drawing to establish the width of the flange at the fillet (tread) radius / flange angle tangent point. This provides a .0134" thicker flange at this point at full .187" height. This is easy to measure from the back of the wheel.
On profile 2 drawing, I used the intersection of the flange and tread planes to establish the flange thickness of .156". Using the flange tip radius of .062", the flange height becomes lower at .147". Measuring this from the back of the wheel is not possible unless you consider the distance from the theoretical point of intersection to the tangent point of the fillet radius along the 10 degree angle of the flange.
Which is correct and why? (extra credit for showing your work)
PS I hope I don't have to re-profile my wheels
Attachments
Wheel Profile 1
Wheel Profile 2
Bruce Mowbray
Springville & Southern RR
TMB Manufacturing & Locomotive Works
Bill,
I believe the reason the flange depth is specified as a maximum is to keep the flange from bottoming out in a frog. If it is made less than the maximum it still conforms to the IBLS standard, and there is no incompatibility with current track. If the flanges are made less than 0.187" they will look a lot more like the AAR wheel profile, which seems to work for the full-size RRs.
just for the record, some of us out here, are machining new flange height to .125 +.005 instead of .1875 and having ZERO issues on any track we run at.
just need to make sure the trucks are flexible
Fixed, that is what happens when to much is going on at the same time
Last edited by cbrew on Fri Dec 06, 2013 3:44 pm, edited 1 time in total.
Your drawing number one is the current flange size and the current measurement method. I am not proposing changing the size, only where the measurement is made when doing a drawing of the flange. When the measurement point is moved the value supplied in the flange width tables will also be changed to maintain the flange the same width and height. Again, I am not changing the size of either new or already machined wheels.
You are correct that flanges could be much smaller and still work. There are modelers in HO scale that use scale size flanges and, with carefully laid track, have no problems.
As to the flange bottoming out in frogs. That is exactly what they are designed to do. As in the prototype the outer edge of the flange carries the weight on the wheel when the wheel tread becomes unsupported crossing the gap in the rail head. Many persons constantly report problems with the sharp point of a frog being pounded out of shape. Some have designed frogs with hard steel inserts, etc. in order to stand up to the impacts that result from the wheel tread hitting them. This is not necessary. The flange height should be a minimum and the flangeway depth in the frog should be a maximum so that the flange runs on the bottom of the flangeway. This is the same as what is called for in prototype handbooks from the AREMA.
(He does!)
