Double-Flanged Wheels and Stub Points

[Jeremy Cumberland]

This is my first post on RMweb since it is only recently that I have started railway modelling again, but I came across an unexpected problem in my little lockdown project. Since it involves double-flanged wheels and stub points, it is not a problem that many people are likely to face, but very little seems to have been written about modelling with double-flanged wheels, so I thought I would share it with you while I wait for some new wheels to arrive from Shapeways.

 

Originally I had just intended building some 7/8" scale Dinorwic Quarry slate wagons, with conventional wheelsets, to run on a garden railway (not mine – I don’t have a garden). However, this very quickly got sidetracked in favour of building a working stub or "Fothergill" point on a bookshelf, and putting double-flanged wheels on a couple of the wagons to form a diorama. I had visited Dinorwic Quarry a couple of years ago and took a number of photographs and measurements. I used these to make CAD models of chairs, wheels and other castings and got them 3D printed. With all the adjustment and reworking I had to do on the point (and I’ve still got a few more changes to make), I feel I could write a whole paper on stub points, but this post is really about wheels. Nevertheless, I was rather pleased with the stub point when I had it assembled (I haven't yet fitted check rails):

My first attempt at a wagon was rather less successful. Although supposedly to scale, I had neglected to allow for the wider gauge (45 mm in 7/8” scale is 2’ 0½”, whereas the actual gauge in the quarry was 1’ 10¾“) and a commercial 45 mm gauge wheelset rubbed against the inside of the frame. An elementary mistake to make. I’ll probably remove some material from the frames later, but in the meantime I built a second wagon which was slightly wider. With single-flanged wheels, it negotiated the point without any problem, but when I fitted a set of the double-flanged wheels I’d had printed, they barely fitted on straight track, and wouldn’t negotiate changes in direction at all.

This problem, too, was fairly easy to identify. The tread was too narrow, and as soon as a wheel reached a bend (Dinorwic stub points don’t have curves ) , there wasn’t enough room between the flanges for the rail to be at an angle to the wheel.

 

I redesigned the wheel to have a wider tread and got a couple of sets printed.

 

The new wheels were better, and I could at least make the wagon negotiate the diverging line if I kept my hand on it, giving it some weight, but when I pushed it along or pulled it by the hook, it derailed as soon as the leading wheels crossed over the toe (stub) end of the switch rails. Because Dinorwic Quarry points have straight stock and closure rails on the diverging line, there is a considerable change in rail direction to negotiate (about 5°), made worse in my case by the gauge being overscale. I had made the closure rails a scale 12’ long as per the prototype, but it might well have been better to have kept the same angle as the prototype and made the closure rails longer. The idea of making the diverging line curved never occurred to me, but would certainly make for more reliable running.

 

The front wheels were both hard up against the axleboxes, so it seemed that I needed to widen the wagon frames a little more. On the other hand, the inside wheel being up against the axlebox was only to be expected, because with loose wheels this is the only way the front of the wagon can be pushed round a bend, and the opposite wheel appeared to have clearance between the rail and the outside flange.

I couldn’t quite work out what was going on, but since I already had 3D CAD models of the wheels and chairs, I thought I would create a CAD model of the point and build the wheel model into a virtual wagon.

 

3D CAD is a wonderful invention. Once you have created a model, you can slice it in any way you choose, to see clearances, clashes and contact points. You can also, by making short movements step by step, see that path that objects take.

 

In these pictures, I have positioned the “wagon” just at the first point of contact between a flange and a rail. I have cut away the front of the wagon in line with the rail head, leaving just the flanges:

 

Here are the close-up views. First the left-hand wheel on the outside of the bend:

There is clearance between the rail and the flanges, but the wheel is actually running on the outside flange root radius (this is the bulge in the middle of the flange). I have no idea how accurately the root radii were printed, but I have come to realise they serve no purpose with double-flanged wheels. At any rate, this wheel seems fine.

 

Here is the right-hand wheel on the inside of the bend:

Here the flange is in contact with the rail, but it is the leading edge of the flange. Looking at it side-on, with the rest of the wheel restored, it is easy to imagine the flange climbing up the rail. The flanges are near-scale, a mere 1.18 mm deep, but I am sure the flange would climb up the rail even if it were 2 mm deep (the standard for 45 mm gauge). The flanges aren’t really 16-sided; this is just how the CAD program renders them.

 

Clearly what is needed are flange angles. The prototype does not have them (which is why my wheels didn’t), but prototype wagons weigh about seven hundredweight (350 kg). My wagon weighs two ounces (60 g).

 

In my 3D CAD model of the wheels, I removed the root radius and added 20° flange angles (the is the G1MRA standard, and in far off days was also the flange angle adopted by the Manchester Model Railway Society for what might have been the very first finescale wheels, way back in the 1950s, so it seemed a good starting point). I then needed to thicken up the flanges to make them suitable for 3D printing – the base of the flanges are now 0.95 mm thick, which might sound very thin for 45 mm gauge, but the backs of double-flanged wheels don’t do anything, so they only need enough thickness to give them strength. The tread width is 4.2 mm, or 1.4x the rail width, and the flange depth is 1.18 mm, as before. A slight boss in the centre brings the overall width to 6.5 mm, which is also unchanged.

 

At this point, it might be worth noting that double-flanged wheels need extra space between the frames compared to single-flanged wheelsets. The standard width over a wheelset in 45 mm gauge is 52 mm (40 mm back-to-back plus 2x 6 mm wheel thicknesses). Double-flanged wheels should really be centred on the rail centres, which are 48 mm apart with the Chris Barker code 250 rail I am using. My wheels are 6.3 mm across the outsides of the flanges, or 6.5 mm wide overall, which means I should have 54.5 mm between the frames to accommodate them. My test wagon actually has 54 mm, and this is what the CAD model shows so I think it will be fine.

 

Here is the CAD model with the virtual wagon fitted with the new wheels, showing the leading right-hand wheel running onto the stock rail. Because of the greater clearance, I have had to run the wagon forward a few millimetres:

This is far better. The edge of the flange no longer touches the rail, and it is unlikely the sliding contact further back will have the grip to ride up onto the rail head. However, it is a close-run thing, and I don’t think a smaller flange angle would work.

 

Incidentally, while G1MRA use a 20° flange angle in their wheel standard, the 16 mm Association use a 10° angle in theirs, and put a 10° angle on the back of the flange as well (why, I wonder – are 16 mm modellers that much worse at bending check and wing rail flares than modellers in other scales?). This made me curious about what my other rolling stock has. A quick check reveals my Slaters wheels (two different types) and Accucraft carriage/wagon wheels use the G1MRA standard, but my Accucraft Quarry Hunslet uses the 16 mm Association profile. I must say I find this very odd, and I am a little puzzled why the 16 mm Association chose 10° in the first place, since their members are surely far more likely than gauge 1 modellers to use the sharp curves that make 20° more necessary.

 

The new wheels are now being printed (with rounded flange edges not shown in the picture above) and I look forward to seeing what improvement they make.

[Ian Smeeton]

Working in 2mm finescale (large enough for me), I found that check rails are actually functional. Ther really is a reason for them being there!!

 

Perhaps the addition of check rails might help.

 

One other thing which occurred to me is the actual wheel profile.

 

Single flange wheels are coned (about 10 degrees, I think) on the real railway.

 

if you are printing your own wheels, might it be possible to introduce a double coning effect to the wheelsets, so that in section, the tread looks like a flattened W?

 

This should help to keep the wheel centred on the rail head so less chance of the flange climbimg the rail.

 

No experience, only thoughts.

 

Regards

 

Ian

[MikeTrice]

No idea if this image helps?

http://www.modelrailroading.nl/news articles/PhotoEssays/2011/2011-08-24 Llanberis Lake Railway/index.html#DSC07319.JPG

 

I wonder how the Slater's kits perform.

[Grovenor]

I would keep a root radius, it is there to keep the flanges away from the rail as much as possible, and use the 20 degree flange angle.

 

Ian,

These are double flanged wheels loose on their axles, neither check rails or tread coning are of any value.

[Ian Smeeton]

13 minutes ago, Grovenor said:

I would keep a root radius, it is there to keep the flanges away from the rail as much as possible, and use the 20 degree flange angle.

 

Ian,

These are double flanged wheels loose on their axles, neither check rails or tread coning are of any value.

 

Sorry, I hadn't realised that the wheels were both loose on the axle.

 

Back to (someone else's) the drawing board.

 

Regards

 

Ian

[Ref44]

Having tried something similar in 16mm scale, I found that running improved when I drilled the hole in the wheel a bit larger than the axle diameter. This allowed the wheel to angle slightly at the joint from closure rail to switch/crossing rail. I had the same problem with wagon width, 32mm gauge was too wide.

[Mountain Goat]

The beauty is that double flanged wheels did not need an exact gauge. This is why they were used as with some of the quarries, a rock falling on the track, or rough handling of the light rails, which were often only strips of metal which sat in slots in the sleepers and keyed in with wedges of wood which over time tended to lean over etc... Only the wealthier quarries could afford proper rails and railchairs. 

Now I have a question to some who may know this. The old way that was once popular was to have flangeless wheels where the track had the flanges. Now this design found favour in the early years as waggons did not have to stay on the rails. They had the advantage of being pushed to where they were needed off the rails and then simply pushed back on to the end of a track where they were assembled to make their next journey. 

Question. Were double flanges also used in this way?

In the early years when for a while they had both railed systems, locos (If they were wealthy enough to have had a loco) and waggons would have suitable wheels with thick flanges which could be used with both track systems with the same wheels. The new edge rails had to have a slightly wider gauge to do this but it was a brilliant solution as it meant that one could slowly convert ones railway system as one could afford it, as lets face it. Railways are not cheap!

[Jeremy Cumberland]

Thank you for the replies.

 

In this particular case, the wheels aren't loose on the axles, but each wheel has its own axle, which can move from side to side (although I am not sure how much it does this on a model). This means that the wheels are held square to the wagon in both axes, something that with conventional wheelsets is usually essential (unless you have a steering or tilting mechanism).  However, I like @Ref44's suggestion of giving the wheels a rather loose fit, and I may try this.

 

As @Grovenor points out, check rails serve no purpose with double-flanged wheels. Until I built this point, I had wondered why Dinorwic Quarry added check rails to their stub points at all. After building the point, however, and running a few vehicles over it, I think it is to protect the crossing rail from getting clouted by a heavy steam locomotive if there is any misalignment (check rails were only fitted on lines used by steam locomotives). It is harder to ensure correct alignment of the crossing than it is the switches, and the crossing is not so easily seen by the person operating the point. I suspect that check rails fell out of use over time, since some points had check rail chairs but no check rails. Other points did not have check rail chairs at all, or had them only on one line.

 

On 24/06/2020 at 09:23, Grovenor said:

I would keep a root radius, it is there to keep the flanges away from the rail as much as possible, and use the 20 degree flange angle.

I don't think I want to keep the flanges away from the rail. It is only the rail-flange contact that changes the wagon's direction; it is not like conventional wheelsets where you can use the root radius as a form of extreme coning, to help steer a vehicle round a curve by steering the axle. In any case, I don't see how the root radius would keep the flange away from the rail since there is nothing that I can see to cause the the wheel to move off the root radius; the weight of the wagon surely isn't enough. If I adopt @Ref44's loose-fit suggestion, then I imagine root radii would cause problems, since the wheel would be sitting on the outside edges of the rail, and the different diameters of the flange root and the tread would try to turn the flange into the side of the rail.

 

However, one thing I will do in due course is set up my test oval of track and pull and push some wagons around with different wheel types, to see what works best on more normal track. The 5° change in direction that this point has is rather extreme.

 

On 24/06/2020 at 10:08, Ref44 said:

I had the same problem with wagon width, 32mm gauge was too wide.

I imagine 0-16.5 modellers have it far worse than us. Or does everyone model 0-14 these days?

 

On 24/06/2020 at 10:36, Mountain Goat said:

Now I have a question to some who may know this. The old way that was once popular was to have flangeless wheels where the track had the flanges. Now this design found favour in the early years as waggons did not have to stay on the rails. They had the advantage of being pushed to where they were needed off the rails and then simply pushed back on to the end of a track where they were assembled to make their next journey. 

Question. Were double flanges also used in this way?

It is possible, I suppose, but double-flanged wheels hardly lend themselves to this. If the flanges sink into the ground at all, then going round corners becomes next to impossible.

 

On 24/06/2020 at 10:36, Mountain Goat said:

In the early years when for a while they had both railed systems

Did anywhere have both plateways and edge rails , that you know of?

Edited June 25, 2020 by Jeremy C

[Mountain Goat]

11 hours ago, Jeremy C said:

Thank you for the replies.

 

In this particular case, the wheels aren't loose on the axles, but each wheel has its own axle, which can move from side to side (although I am not sure how much it does this on a model). This means that the wheels are held square to the wagon in both axes, something that with conventional wheelsets is usually essential (unless you have a steering or tilting mechanism).  However, I like @Ref44's suggestion of giving the wheels a rather loose fit, and I may try this.

 

As @Grovenor points out, check rails serve no purpose with double-flanged wheels. Until I built this point, I had wondered why Dinorwic Quarry added check rails to their stub points at all. After building the point, however, and running a few vehicles over it, I think it is to protect the crossing rail from getting clouted by a heavy steam locomotive if there is any misalignment (check rails were only fitted on lines used by steam locomotives). It is harder to ensure correct alignment of the crossing than it is the switches, and the crossing is not so easily seen by the person operating the point. I suspect that check rails fell out of use over time, since some points had check rail chairs but no check rails. Other points did not have check rail chairs at all, or had them only on one line.

 

I don't think I want to keep the flanges away from the rail. It is only the rail-flange contact that changes the wagon's direction; it is not like conventional wheelsets where you can use the root radius as a form of extreme coning, to help steer a vehicle round a curve by steering the axle. In any case, I don't see how the root radius would keep the flange away from the rail since there is nothing that I can see to cause the the wheel to wish to move off the root radius; the weight of the wagon surely isn't enough. If I adopt @Ref44's loose-fit suggestion, then I imagine root radii would cause problems, since the wheel would be sitting on the outside edges of the rail, and the different diameters of the flange root and the tread would try to turn the flange into the side of the rail.

 

However, one thing I will do in due course is set up my test oval of track and pull and push some wagons around with different wheel types, to see what works best on more normal track. The 5° change in direction that this point has is rather extreme.

 

I imagine 0-16.5 modellers have it far worse than us. Or does everyone model 0-14 these days?

 

It is possible, I suppose, but double-flanged wheels hardly lend themselves to this. If the flanges sink into the ground at all, then going round corners becomes next to impossible.

 

Did anywhere have both plateways and edge rails , that you know of?

 

They did in South Wales, UK in the early 1800's. One line I read about started off as an edgeway line, and was converted into a plateway (As that was the "In thing" in latest technology back then, and later converted back to edgerail design. (Edge rail is what we use today as the rails are sat up on edge).

[Ref44]

The other issue I faced with 16mm scale was the mismatch of Slaters loco wheels to 32mm gauge. The slop is great for getting round tight curves; for 2 rail power it is a nightmare at the crossing. I had to tighten the gauge to 31mm or just below at the crossing to stop the outside wheel shorting on the inner closure rail. Depending on what motive power you are proposing to use, it is something to keep in mind.

[Jeremy Cumberland]

4 hours ago, Ref44 said:

The other issue I faced with 16mm scale was the mismatch of Slaters loco wheels to 32mm gauge. The slop is great for getting round tight curves; for 2 rail power it is a nightmare at the crossing. I had to tighten the gauge to 31mm or just below at the crossing to stop the outside wheel shorting on the inner closure rail. Depending on what motive power you are proposing to use, it is something to keep in mind.

 

This is just a static diorama on a bookshelf, and will be no bigger than the grey base you see in the first photograph, so there is no need for track or any other form of power; I barely have room to fit a single wagon on the plain track before the switch rails. However, I read your own double-flanged wheel thread with great interest and wondered how you insulated the point, particularly with metal chairs (but I assumed you must have arranged it so the closure rail "block" chairs did not conduct from one rail to the other).

 

Do you have the closure rails permantly wired to their respective stock rail? I imagined that you would switch them electrically, and the rail beyond the crossing as well (with insulated joints a little further on), so that the unused closure rail and the unusued rail beyond the crossing were unpowered. This ought to mean that a single short across one of the "block" chairs (which I could easily imagine) wouldn't be a problem, and problems would only arise if you had shorts at both ends of the unusued closure rail at the same time.

 

I then wondered what would happen if someone ran single-flanged stock on a double-flange turnout. This ought to be far more reliable mechanically, but I imagined the risk of having two simultanous shorts would increase considerably (I reckoned double-flanged wheels probably wouldn't be a problem here, not unless they were very wide). I suppose this is why the very few double-flanged stub points I have seen on exhinition layouts seem to have very wide rail separation at each of the block chairs.

 

However, all this is speculation; I have no practical experience and bow to those who do. I would much rather see a layout with a slightly wider than prototype rail separation that worked, than one that was exact scale but didn't.

Edited June 25, 2020 by Jeremy C

[Ref44]

My last attempt had metal block chairs at the switch end of the closure rails and on the vee side of the crossing. The crossing end of the closure rails had a plastic block chair. The turnout was wired in a coventional manner; stock rails and closure rails linked, with the pivoted crossing and short rails beyond wired as a switchable crossing. By reducing the gauge to 30.75mm, i could get a reasonably small gap in the block chairs. Things worked by keeping the relevant wheel tight to the closure rail, it being forced there by the restricted gauge. I could run both my De Winton and Hunslet through the turnouts without shorts.

You have now given me an idea of only powering the closure rail when needed using relays. Some experiments will be called for.