Building a C Class

[lucas]

I’ve been wanting to build a C class loco for a while now. I was originally planning to use the Silver Fox kit, but there are a few aspects of the kit that I wasn’t super happy with.

The main issue for me was the kit represents the later reengined B201 class, not the original Crossley-engined locos I wanted to model. The roof detail in particular changed a lot during the conversion; the existing vents were chopped up and repositioned to suit the new GM engines, the exhausts were completely different, and a much larger cooling fan was installed. The side radiator grilles were also much larger on the reengined locos, but interestingly the kit does use the smaller Crossley grilles here.

I figured if I was going to end up cutting up the kit to get it looking how I want, I might as well just start off with a clean slate and build my own.

A couple weeks ago I started working on a 3D print of the body shell. My little old FDM printer has neither the resolution nor the willpower to actually print any detailed parts, but I figured it could give a decent attempt at getting the basic shape dialled in. This isn’t just going to be one of those ‘scratch builds’ where the whole thing is just 3D printed in one go, I swear.

I forgot to take a picture of the finished print, but here it is after the first round of sanding. I printed in red because I’m modelling Iarnród Chorcaí after the People’s Republic declared independence because I just had a bunch of red filament lying around.

Here is the final revision behind an earlier draft. I made a slight tweak to the angle of the upper section of the cab with the windshields. There is only a fraction of difference between them, but the earlier print just looked a little off, to my eyes at least. As amazing as the CAD tools are, it’s a lot easier to see if things look right on a physical object. While I got most of the main dimensions from the C class drawings in the resources section, things like the curvature and angle of the cab ends were done by measuring photographs of the prototype from different angles and adjusting as necessary until it looks right. I think I got it pretty close, even if I do say so myself.

To fill in between the layer lines on the 3D print I use Polyfilla (yes, the stuff you use to repair holes in walls) thinned with a few drops of water. I brushed on a few layers and sanded back down to give a smooth finish. I will still need to give it a coat of filler primer when it comes time to paint it, but has smoothed out most of the bigger imperfections from the printing process.

The two red rectangles you might notice on the side are slightly recessed to align the air intake vents. I masked them off so that I wouldn’t fill them in which is why they’re still a slightly brighter shade of red. I actually haven’t decided how I will make the vents themselves. I will likely need some etched parts for the roof and the chassis, so I might design some etched for these too. I did pick up Studio Scale Models’ detailing kit for the Silver Fox kit, so I already have etches for most of the other grilles.

I’m hoping to start work on the underframe this weekend, but I figured I’d share my progress so far.

 

EDIT:

A few people have asked about the 3D model I made, so here they are. The .f3d file is the design file for Fusion 360 and the .stl is the finished model if anyone wants to print it.

Feel free to use them however you want, as long as you give appropriate credit; i.e. don't pass it off as your own.

c-class-body.stlc-class-body.f3d

Edited April 16 by lucas
Adding model files

[Mol_PMB]

Nice work! That captures the shape of the 'face' much better than the Silver Fox version.

[irishthump]

Wonderful finish on the print! It certainly looks the part.
What are you planning to use for the chassis?

[Tullygrainey]

Innovative stuff! Well done. And a new use for Polyfilla into the bargain

[lucas]

38 minutes ago, irishthump said:

What are you planning to use for the chassis?

I'm not entirely sure yet. Nothing RTR seems to have the same dimensions, plus I'll be building to 21mm gauge which further complicates things. I might well end up having to design my own chassis if I can't avoid it.

[Patrick Davey]

Very nice - looking forward to more updates.  Early days but do you have a livery in mind?

[lucas]

6 minutes ago, Patrick Davey said:

Very nice - looking forward to more updates.  Early days but do you have a livery in mind?

At the moment I'm thinking unlined green. But I am the kind of person that changes my mind a lot, so we'll see

[Mayner]

10 hours ago, lucas said:

I'm not entirely sure yet. Nothing RTR seems to have the same dimensions, plus I'll be building to 21mm gauge which further complicates things. I might well end up having to design my own chassis if I can't avoid it.

Many years ago I picked up a Q Kits C/B201 class motorised with a shortened Athearn F unit chassis, I also used Athearn trucks/bogies and drive in combination with a frame fabricated from KS brass strip and brass section for motorising MIR whitemetal diesel kits.

I don't know about current Athearn chassis, but the Athearn & Lifelike/Walthers Proto 2000s trucks of the era used a stub axle system which allowed the wheelsets to be easily adjusted to 21mm gauge.

Shortened Athearn F7 chassis fitted to Q Kits B201    The HO scale F Unit truck/bogie 9' wheelbase is reasonably close to the 8' when re-scaled to 4mm.

The original builder shortened the chassis to fit a B201 apparrently by shortening the diecast chassis at both ends, moving one of the trucks/bogies inwards (RHS of photo) with a new frame stretcher/truck pivot fabricated in brass and removing the flywheel. Bogie sideframes appear to be Q Kits with brass steps added by the original builder. I fabricated a completly new frame/chassis from KS box section and strip to motorise an MIR 141 with trucks and drive from an Athearn GP35, shortening the drive by omitting both flywheels. 

A 3D printed frame possibly in metal would be an alternative to a scratchbuilt/modified rtr frame.  A local modeller uses a Chines print house to 3D print gearboxes and gears/transmission parts in aluminium for O gauge locomotives.

Athearn truck/bogie with existing wheelsets pushed out to 21mm gauge. Wheels run on stub axles rectangular brass bush and steel strip is part of the pick up system.

 

[Dempsey]

I have a silverfox kit myself that I'm planning to build onto a dcc doner.

[lucas]

5 hours ago, Mayner said:

Many years ago I picked up a Q Kits C/B201 class motorised with a shortened Athearn F unit chassis, I also used Athearn trucks/bogies and drive in combination with a frame fabricated from KS brass strip and brass section for motorising MIR whitemetal diesel kits.

I don't know about current Athearn chassis, but the Athearn & Lifelike/Walthers Proto 2000s trucks of the era used a stub axle system which allowed the wheelsets to be easily adjusted to 21mm gauge.

Shortened Athearn F7 chassis fitted to Q Kits B201    The HO scale F Unit truck/bogie 9' wheelbase is reasonably close to the 8' when re-scaled to 4mm.

The original builder shortened the chassis to fit a B201 apparrently by shortening the diecast chassis at both ends, moving one of the trucks/bogies inwards (RHS of photo) with a new frame stretcher/truck pivot fabricated in brass and removing the flywheel. Bogie sideframes appear to be Q Kits with brass steps added by the original builder. I fabricated a completly new frame/chassis from KS box section and strip to motorise an MIR 141 with trucks and drive from an Athearn GP35, shortening the drive by omitting both flywheels. 

A 3D printed frame possibly in metal would be an alternative to a scratchbuilt/modified rtr frame.  A local modeller uses a Chines print house to 3D print gearboxes and gears/transmission parts in aluminium for O gauge locomotives.

Athearn truck/bogie with existing wheelsets pushed out to 21mm gauge. Wheels run on stub axles rectangular brass bush and steel strip is part of the pick up system.

 

This is good information, thank you John!

To be honest I'd been looking mainly at UK models for a donor chassis without really considering much else. I reckon I'll need to take a closer look further afield before deciding what to do.

[irishthump]

3 minutes ago, lucas said:

This is good information, thank you John!

To be honest I'd been looking mainly at UK models for a donor chassis without really considering much else. I reckon I'll need to take a closer look further afield before deciding what to do.

I seem to remember at least one poster here who used the MM 141 chassis under a Silverfox body, personally I would'nt have the heart to butcher a 141!

In the past I used an Athearn F7 body with Co-Co trucks from an Atlas loco under an A class body. I think one of the small shunters like the SW1500 might be a good fit, and as was mentioned easy to convert to P21.

I have a few spare Athearn parts floating around at home, I could look through them and see if there's anything of use to you if you like.

[lucas]

38 minutes ago, irishthump said:

I seem to remember at least one poster here who used the MM 141 chassis under a Silverfox body, personally I would'nt have the heart to butcher a 141!

Here it is sitting on top of my Murphy/Bachmann 181. The distance between the bogie pivots and the overall length are each too long, so it would need a ~10mm slice cut out of the middle. The bogie wheelbase and wheel diameters are both <1mm off, so it could work. But then again they are a bit of a pain to regauge (I've been putting off regauging this 181 for a while).

[irishthump]

1 minute ago, lucas said:

Here it is sitting on top of my Murphy/Bachmann 181. The distance between the bogie pivots and the overall length are each too long, so it would need a ~10mm slice cut out of the middle. The bogie wheelbase and wheel diameters are both <1mm off, so it could work. But then again they are a bit of a pain to regauge (I've been putting off regauging this 181 for a while).

OK. I must have mis-remembered that one!

[Mol_PMB]

121s are a bit shorter than 141s.

20'8" bogie centres compared to 22'6" for the 141s. Would be pretty close.

C class are 21'0" bogie centres so the 121 is within 1mm. The bogie wheelbase is the same on both, 8'0".

[lucas]

2 hours ago, Mol_PMB said:

121s are a bit shorter than 141s.

20'8" bogie centres compared to 22'6" for the 141s. Would be pretty close.

C class are 21'0" bogie centres so the 121 is within 1mm. The bogie wheelbase is the same on both, 8'0".

I figured a 121 would probably be closer, but  I hadn't been able to find the exact dimensions. I had always assumed the bogie wheelbase would be the same 8' 1½" as the 141/181, not that you would see the difference.

I might keep an eye out for a damaged 121 I wouldn't feel too guilty about cutting up

[Brendan8056]

Lucas,

            I have a couple of Q kits C class locos, one purchased secondhand, which uses Model Irish Railways bogies. the one I built myself is on an Athearn switcher chassis, the one that used to be marked on the boxes as an SW1500, but was always an SW9 or similar. The bogie wheelbases are a bit short but the sideframes hide this and it runs sweetly. Both are 21mm gauge.

    The 3d loco you have done looks good. I think the Q kits version got the cab end profile of the A and the C very well. Whatever faults they may have 45 years ago they were the only models available.

[enniscorthyman]

Heljan class 15 is a good doner  for a silverfox C class.

[lucas]

2 hours ago, enniscorthyman said:

Heljan class 15 is a good doner  for a silverfox C class.

Class 15 is probably the closest BR loco, but it's still 1' 6" (6mm to scale) longer between bogie centres and 6" (2mm) longer bogie wheelbase.

I had been using this list http://www.clag.org.uk/wheelbase.html for comparing dimensions. For reference a C Class has 21' 0" between bogie centres, 8' 0" bogie wheelbase, and 3' 2" wheel diameter. 

I'm hoping to keep things within a mm or 2 which doesn't really seem to be possible with anything that ran in Britain.

 

Unless something perfect comes along I might just end up building my own chassis anyway. Even if not out of necessity, as a challenge to myself. I've always been the kind of modeller that likes building models, not necessarily just playing with finished models.

[Colonel]

Having done a decent job so far on the body, I'd say go for it with the chassis. There are rtr and bogie kits out there that are worth looking up. Try 'Locos n Stuff'. Mainly narrow gauge, but Mark Clarke does a large range and offers both etched and 3D printed chassis, including replacements for Tenshodo spuds.

 I've got one of his bogies under my 21mm gauge Donegal railcar and it runs very nicely. He doesn't advertise widely, but his website is a delight, with all sorts of ideas and products.

 Even if you are not interested in narrow gauge, there is something for everyone here!

[enniscorthyman]

The SilverFox C class body is decent enough. I know some may say the face of it is a bit off.I love my little 209 which has a Bachmann class 20 chassis.The class 20 chassis obviously didn't  fit,so it was cut a fair bit and only one bogie is driven  from the motor,but it runs very well.

[jhb171achill]

6 minutes ago, enniscorthyman said:

The SilverFox C class body is decent enough. I know some may say the face of it is a bit off.I love my little 209 which has a Bachmann class 20 chassis.The class 20 chassis obviously didn't  fit,so it was cut a fair bit and only one bogie is driven  from the motor,but it runs very well.

It looks very well, with the detailing a highlight too. A grubby little workhorse! I had a cab run in one on a ballast train in the 1970s from then-closed Clonsilla to North Wall..... I think I had 209 on the Loughrea branch too, still in the old livery.

[enniscorthyman]

10 minutes ago, jhb171achill said:

It looks very well, with the detailing a highlight too. A grubby little workhorse! I had a cab run in one on a ballast train in the 1970s from then-closed Clonsilla to North Wall..... I think I had 209 on the Loughrea branch too, still in the old livery.

I was inspired to number this C class 209 because  of a few photos of it on the North Kerry line hauling the Weed Killer train.209 itself was looked at by the ITG for preservation at one stage.

[jhb171achill]

14 minutes ago, enniscorthyman said:

I was inspired to number this C class 209 because  of a few photos of it on the North Kerry line hauling the Weed Killer train.209 itself was looked at by the ITG for preservation at one stage.

I'm sure I had a close encounter with 209 itself somewhere other than Loughrea - you've got me wondering now!

[Robert Shrives]

I look forward to this loco build as I too have a Silver Fox C class and it looks ok to me but can see the front shape is better.  With tongue  slightly in cheek I expect when finished a very well know supplier will announce an RTR model.  In a twin pack in NIR blue and an 80 class railcar.

robert

[DJ Dangerous]

6 hours ago, Robert Shrives said:

With tongue  slightly in cheek I expect when finished a very well know supplier will announce an RTR model.  In a twin pack in NIR blue and an 80 class railcar.

robert

With that in mind…

Any chance you could build an O Gauge 071, first?

[lucas]

12 hours ago, Robert Shrives said:

With tongue  slightly in cheek I expect when finished a very well know supplier will announce an RTR model.

As long as I can get a little use out of mine before before it gets usurped by a RTR version I'm happy 

[lucas]

A few people have asked about the 3D model I made, so I've attached them both here and in the original post.

The .f3d file is the design file for Fusion 360 and the .stl is the finished model if anyone wants to print it.

Feel free to use them however you want as long as you give appropriate credit; i.e. don't pass it off as your own.

c-class-body.f3dc-class-body.stl

[enniscorthyman]

[Tullygrainey]

Lovely model. Looks and sounds great. Layout looks pretty good too!

[lucas]

Made some progress building the frame out of plasticard over the last week.

I had estimated the height of the solebar (or at least the visible portion thereof) to be 4 inches when I created the model, or 1.333 mm to scale. Unfortunately I didn’t have any 1.333 mm plasticard lying around, so I had to laminate together 0.040” (1.02 mm) and 0.012” (0.30 mm) to get the correct thickness.

I created the buffer beams by cutting and drilling holes for the buffers and coupling. The detail around the coupling was incredibly fiddly to put together, but the result isn’t so bad. I did a little more filing after this photo was taken. It’s not perfect but once painted and weathered I reckon it won’t be too bad.

This was glued to the ends of the solebar along with the triangular gussets which drop from the solebar down to the bottom of the buffer beam on either side.

On the prototype there are two plates welded to the underside of the buffer beam and the triangular gussets. You can see in some of Ernie’s photos that it makes the buffer beam appear a little taller on both sides and there is a clear weld line against the gusset on the side.

I added two thin pieces of plasticard to represent these.

I haven’t cut any holes for the chassis yet, just marked out where the bogie centres should go. That will come later when I have a better idea of what the chassis will look like.

For now here is the finished frame sitting underneath the body. It looks a bit weird without the front footplate (or whatever you call it) with the lamp mounts, almost more like an A Class. I will probably try to make this out of brass so it's not too fragile.

Buffers and couplings are loosely fitted to show what it will look like. These will be one of the last things to be glued in place as I have a history of accidentally breaking off smaller protrusions mid-scratchbuild. The screw link coupling is a Hornby part, while the buffers are Accurascale Class 37 ones. I will file down the buffer cylinder to remove the little foot step on top, since the Cs didn't have them.

 

[Mol_PMB]

That’s looking excellent and you have done a great job in capturing the little details. 
One of the differences between the faces of the A and C class is the relative position of the cab front and the bufferbeam, with the footplating overhanging the bufferbeam on the C, while on the A the cab front is set back a bit. Looks like you’ve got that relationship correct but perhaps need some thin metal shim for the overhang?

Excellent work, anyway. I’m taking the easy way out and waiting for IRM to make one, but I do hope they hurry up! 

[lucas]

1 hour ago, Mol_PMB said:

Looks like you’ve got that relationship correct but perhaps need some thin metal shim for the overhang?

Yes, that's the front footplate I mentioned is still missing. I'm sure that's not the correct term, overhang might be better. 

I'll be making that out of brass since I reckon a thin sheet of plasticard would be too fragile. I might get the curved shape etched since it saves me a bit of work and I'll be getting some etches made for some of the other details anyway.

[Mol_PMB]

Very good! Sounds spot on. I should read more carefully.  

[Colonel]

Good stuff and nice to see a bit of hybrid/mixed media modelling.

[Horsetan]

On 24/4/2026 at 6:38 PM, Mol_PMB said:

.... I’m taking the easy way out and waiting for IRM to make one, but I do hope they hurry up! 

I wonder what the spares situation at IRM is for "A" class parts at the moment? I'm sure there's bits in there he could cannibalise....