Reducing wheel flanges

[Orange Cat]

I am looking at a loco which has 6'6" driving wheels spaced at a wheelbase of 6'9"+8'3". As the 2mm FS Standards set flange depth as 0.51mm that would mean two pairs of wheels with a diameter of 14.02mm spaced 13.5mm apart. They are not going to fit.

I can see three options:

1. Use smaller driving wheels.

2. Space the driving wheels further apart.

3. Reduce the depth of the flanges.

 

Or a combination of the above.

I don't particularly want to use smaller driving wheels. The locomotive has a slightly raised footplate so the large wheels are quite a visual characteristic. It also has horizontal outside cylinders so I would either need to drop those or have the cylinders out of alignment with the wheel centres. 

I would also like to avoid altering the spacings if possible, partly, again, for aesthetic reasons and just for the sake of fidelity to the prototype.

That leaves me with option 3, which actually quite appeals. I have often thought that the flanges on 2mm FS are more generous than perhaps they need be. I did a little comparison with other standards. Below are flange depths in, or converted to, mm.

2mm FS: 0.51

NMRA RP-25/54: 0.41

3mm Fine scale: min.0.50, max 0.55
S4: 0.39

S Gauge: 0.46

 

If the much larger scales can use flanges with less depth, that suggests to me that there is scope to reduce the flange depth on 2mm FS wheels also, at least to the NMRA standard of 0.41mm. Possibly even a little more. I would not get the full reduction in overall wheel diameter that I need but it would reduce the size of the adjustment to the wheelbase and hopefully stop it looking "wrong". It would also result on a more "scale" appearance of the driving wheels.

Has anyone tried this, for this or any other reason, and if so how did it work out? Am I setting myself up for problems with keeping the loco on the track?  Should I just go the whole way and adopt, or invent, "Scaletwo"? Opinions and discussions invited.

[Skinnylinny]

I have to admit, I'm not a 2FS modeller, but may I suggest a fourth option? Slightly reduce your flange depths on your outer driving wheels but have flangeless centre drivers. You may find the visual mismatch between the adjacent wheels jarring, however, especially given how close they are. 

[Ian Smith]

I am looking at a loco which has 6'6" driving wheels spaced at a wheelbase of 6'9"+8'3". As the 2mm FS Standards set flange depth as 0.51mm that would mean two pairs of wheels with a diameter of 14.02mm spaced 13.5mm apart. They are not going to fit.

 

I can see three options:

 

1. Use smaller driving wheels.

2. Space the driving wheels further apart.

3. Reduce the depth of the flanges.

 

Or a combination of the above.

 

I don't particularly want to use smaller driving wheels. The locomotive has a slightly raised footplate so the large wheels are quite a visual characteristic. It also has horizontal outside cylinders so I would either need to drop those or have the cylinders out of alignment with the wheel centres. 

 

I would also like to avoid altering the spacings if possible, partly, again, for aesthetic reasons and just for the sake of fidelity to the prototype.

 

That leaves me with option 3, which actually quite appeals. I have often thought that the flanges on 2mm FS are more generous than perhaps they need be. I did a little comparison with other standards. Below are flange depths in, or converted to, mm.

 

2mm FS: 0.51

NMRA RP-25/54: 0.41

3mm Fine scale: min.0.50, max 0.55

S4: 0.39

S Gauge: 0.46

 

If the much larger scales can use flanges with less depth, that suggests to me that there is scope to reduce the flange depth on 2mm FS wheels also, at least to the NMRA standard of 0.41mm. Possibly even a little more. I would not get the full reduction in overall wheel diameter that I need but it would reduce the size of the adjustment to the wheelbase and hopefully stop it looking "wrong". It would also result on a more "scale" appearance of the driving wheels.

 

Has anyone tried this, for this or any other reason, and if so how did it work out? Am I setting myself up for problems with keeping the loco on the track?  Should I just go the whole way and adopt, or invent, "Scaletwo"? Opinions and discussions invited.

 

You could just file the flange away on each wheel where they would touch (a bit like having a flat tyre but only flat at the bottom) 

 

Seriously though, I think most people would use a smaller set of drivers.  A 4'6" (9mm) wheel with the out of scale 0.5mm flange would actually be 5'0" (10mm) diameter which would mean that any splashers would have to be made over-sized, and would probably look too big.  Using an 8mm driver with the 0.5mm flange would bring the overall size of the wheel back to 9mm, and in my view looks right.  It is your model though, so the choice is yours (and I have very limited loco building experience).

 

Ian

[CF MRC]

I would be wary of reducing flange depths too much, the difference between 0.51 and 0.41 is not going to be really apparent: it's only a stroke with a file and I have done it with engines with very tight clearances. As Ian says, the visual effect of the flange can become part of the overall picture and you may still have to increase splasher size, which can be rather obvious. Quite honestly, if you are worried about 0.5 mm here or there in the main body dimensions, especially the length over splashers, then you probably worry too much. The tight dimension could be relaxed by stealing a little from the larger rear space and moving the front wheel forward a touch.

 

Tim

[Orange Cat]

Thanks for the comments everyone.  
 

You could just file the flange away on each wheel where they would touch (a bit like having a flat tyre but only flat at the bottom) 

 

 

I did think of cutting a crescent shape out of one to accommodate the other. I also rejected the idea of reducing the flange thickness by half, at the front of one wheel and the back of the other, so they could overlap.  

Splasher size is not likely to be an issue as the prototype has large splashers anyway. That is part of the reason not to use smaller wheels as the size of the splashers, along with a somewhat raised footplate could, I think, make having the wheel centres lower than scale look a bit odd.

 

 

 the difference between 0.51 and 0.41 is not going to be really apparent: it's only a stroke with a file and I have done it with engines with very tight clearances. 

 

I take it that doing so didn't cause any problems with running? 

I realise that I am only talking about fractions of a millimetre but then that's what we are dealing with in lots of aspects of 2mm modelling, particularly when it comes to clearances. If I can save a few fractions of a millimetre here and there the problem is solved. Turning down the flanges slightly would help with both the wheelbase proportions and any issues with splasher clearances as well as possibly looking better. If I can make a bit of a saving there, without adversely affecting performance it reduces the compromises I need to make elsewhere. As you say, it is only "a stroke with a file" (or a quick spin in the lathe) so not a major undertaking. 

 

[CF MRC]

My Stirling 8' Single has sub minimum spec 2 mm wheels at the front for both tyre width and flange depth, because it has to, with minimal clearances on bogie splashers and slidebars. It works.

 

Tim

[Orange Cat]

That's good to know. The standards looked to me like there was a bit of scope to reduce things slightly but it is good to hear from someone who has done it successfully.

I think I will send off an order to the shop and see how the drivers look turned down a little bit. I can always buy some new tyres for them if I go too far, or they don't work.

[Yorkshire Square]

Tim mentions a reduction of .51mm to .41mm, but you will need to reduce each flange by over half to .25mm to avoid interference. That's getting into P4 territory and they have the benefit of 8 times the mass to keep their stuff on the rails.

 

As a pretty average modeller, I'd push the centre wheelset back a cock hair (technical term). I'm sure nobody here will tell.

[Orange Cat]

I think it will probably be a case of skimming a fraction off the flanges and making up the rest by extending the length of the loco between the first two sets of coupled wheels. If I don't try it, I won't know if it works.

[Tim V]

the P4 and S gauge flanges have the benefit of using springing/compensation. 2mm doesn't use that - to the same extent. You would be bringing trouble I would think.

 

Guy Williams (the noted 4mm builder) used wheels that were correct over the flanges, check his Ian Allan book on 4mm Locomotive Construction. If it was good enough for Pendon, should be good enough in 2mm!

[Chris Higgs]

Tim mentions a reduction of .51mm to .41mm, but you will need to reduce each flange by over half to .25mm to avoid interference. That's getting into P4 territory and they have the benefit of 8 times the mass to keep their stuff on the rails.

 

Not to mention springing. P4 locos with large drivers and a rigid chassis are not that easy to keep on the track. Trust me, I know.

 

Both the other approaches mentioned are used in RTR. Dapol's A3 does not have a prototypical wheelbase, but maintains the correct wheelsize. Farish's Duchesses by contrast reduced the wheelsize by a bit. I don't think 99% of modellers have noticed either subterfuge. I'm waiting to see what Farish will do with their new Castle.

 

it's also worth noting that even with reduced wheel sizes, the issue of mounting your brakegear can be tricky on locos where a close prototypical wheelspace is replicated in the model. You will be well-advised to draw it out in CAD on even on paper before you commit time to actually cutting frames.

 

Chris

[bécasse]

Bear in mind that the diameters quoted for prototype wheels reflect their newly-tyred state. Tyres both wore, and were turned, down before they were ultimately replaced as part of the locomotive overhaul programme. This meant that the actual prototype wheel diameter in service could be up to 3" less than the officially quoted dimension.

 

I would always go with the advice of the late Guy Williams, get the diameter correct over the flanges of the model wheels (or marginally smaller to reflect availability and "prototype wear") - the wheels will look right and fit right.

[Izzy]

I think the problem here is that while the advice of the late Guy Williams is a good one to follow where possible it doesn't always prove feasible. Much depends on the size/depth of the wheel flanges relative to the wheel size and actual scale used. I believe I am correct in saying that Pendon in particular use their own wheel standards - basically the old EEM ones I think - with flange depth/width that is not that much more than the P4 standard. It also helps if wheels are available in sizes that vary in small steps. Not too difficult in 4mm, less so in other scales.

 

With respect to 2mm the 0,5mm flange depth is large relative to the diameters, twice the size compared to much 4mm stuff, and 6'6" drivers are 13mm, but the next available size down is 12mm. A 1mm difference in this scale is very noticeable, even 0.5mm is. I think some well known modellers reduce flange depth to about 0.4mm with no issues, so perhaps in the OP's case it needs a mix and match approach of slightly reduced flanges along with adjusted wheelbase to get a usable combination that looks okay and actually works i.e. the loco stays on the tracks!

 

Izzy

[Orange Cat]

 

perhaps in the OP's case it needs a mix and match approach of slightly reduced flanges along with adjusted wheelbase to get a usable combination that looks okay and actually works i.e. the loco stays on the tracks!

 

 

That pretty much reflects my own conclusion on the subject. As bécasse points out also, treads did wear, so if I end up finding there's problems I can always take a fraction of a millimetre off the treads to restore the profile. I think a 12.7mm driver with 0.4mm flanges, for example, would look a lot better than a 12.0mm one with standard flanges and would only require the wheelbase be adjusted by enough to provide a working clearance between the two sets of drivers. Like I say, if I don't give it a go I will never find out if it works. 

 

[CF MRC]

You may also end up with some very tastefully S shaped spoked wheels!

 

Tim

[Orange Cat]

If they go wrong, at worst I order a new set of drivers from the shop and try an alternative approach.

Just need to decide how many motors to use in the tender drive now. I quite fancy those little 1.5V vibrating mobile phone motors. Use the vibrating motion to drive a crankshaft, mount eight of them in a v-formation and I have a 12V V8 tender drive. No?

Time to start ordering some bits and pieces and clear the work bench, I think.

[34theletterbetweenB&D]

... if I end up finding there's problems I can always take a fraction of a millimetre off the treads to restore the profile. I think a 12.7mm driver with 0.4mm flanges, for example, would look a lot better than a 12.0mm one with standard flanges and would only require the wheelbase be adjusted by enough to provide a working clearance between the two sets of drivers. Like I say, if I don't give it a go I will never find out if it works. 

 

 There's more to it than just the mechanical clearance and on track performance; the loco's appearance may be very sensitive to small changes in wheelbase dimensions, or alternatively not really affected at all!

 

The standard 12mm diameter wheel with a 0.5mm flange is a straightforward fit at the correct 13.5mm axle spacing, and the eye will perceive the 13mm diameter over flanges as the wheel diameter. I'd draw that up in side elevation alongside your proposed modified wheel diameter and wheelbase arrangment, before buying or cutting any metal.

[bécasse]

The standard 2FS 12mm ø driving wheel with 0,5mm flanges will appear to be much closer to 13mm in diameter than you seem to think, partly because the treadwidth is overscale and not just the flange depth. Given that the prototype wheel with allowably worn tyres will come down to 6ft 3in diameter and that its flanges would be barely apparent*, the 12mm ø wheel would probably be a better choice from an appearance point of view even if there were no clearance problems.

 

* If you doubt this, try looking at prototype photos of, say, a 9F in order to determine just which wheels were flangeless - been there, done it, with much cussing!