Garden Railway Forum

Thank you

Handsome loco and very striking in smart safety yellow.

I'm posting my dad's latest project on his behalf, I suppose its a sort of one-off kit for him made by me.

We've had these Andel balcony coaches for years, my dad really likes them, and has been wanting a railcar for some time.


I've had one of those Chinese K40 CO2 laser cutters for a couple of years, but haven't really been able to get much use out of it yet. I've made many modifications, even built a new shed in the garden to house it last year. Now its at a point where its pretty usable, so I wanted a project to to start learning with.

I started drawing up a railcar in the Andel coach style about a month ago in Fusion 360. It ends up with some "interesting" proportions, definitely would need to duck under the doors, but its in keeping with the existing coaches.


Both bogies were designed to be 3D printed. I made a prototype chassis to test. I tried giving giving the rear a bit of pitch compensation as well. At this point the chassis seemed to work well...


I decided to try and give my dad the basic body kit for Father's Day, ended up running into issues with keeping the laser cool, but got most of the wood cut out by the Sunday morning.


All the laser cut bits. Ended up with a few issues with things not fully cutting through, but all a learning experience. The fits for the tab and slot construction came out quite nice, the result when put together was very solid.



We thought it looked a bit odd not having any detailing at all for the doors on the inside. I found some cardboard out of the bin (one of those Amazon cardboard envelopes) and tried cutting out some doors on the laser. I think this worked out quite well - super cheap and quick. Maybe on the next model a full interior could be detailed with cardboard overlays. I didn't give him any cab detailing in the 'kit', left that up for him to come up with.



Started to look at the chassis, now the issues begin. I turned & milled some brass crank pins, M2 thread for a captive nut in the back of the printed wheels. This worked out OK, once the connecting rods were thinned down for clearance, but quartering was not easy. I printed up some jigs but it didn't really help, the idea was to hold the wheels with superglue, but it wasn't very strong and was difficult to keep everything free. The slightest knock and the quartering could go.




So we've just tried milling flats on to the axles, and printing the wheels with a matching flat - turned 90 degrees for one side to get the quartering. The wheels have a slight wobble but the quartering is easy and strong, seems to be working OK.


I got the idea for a ball joint for the front bogie from forum member Gile's Ashanti Bagnall build: https://www.youtube.com/watch?v=ndCPUi-3e94 As it is it provides a lot of articulation to follow a rough track, probably too much, but the socket block is easily replaced with a modified version.


So that's where we're up to today, tested ok pushing one of the coaches up the section of track clear of vegetation, just needs a bit more traction, some lead weights might help.

That is quite impressive, and would make a nice addition to many a railway

Thanks for the detailed description of the railcar's inception and construction. It certainly does look the part! I'll be really interested in seeing how it progresses. I've fought shy of 3D printing wheels and chassis parts up to now, so your conclusions about these are very welcome.

Rik

metalmuncher wrote: ↑Wed Jun 29, 2022 10:08 pm
The wheels have a slight wobble but the quartering is easy and strong, seems to be working OK.

It's looking good Richard. I do like the varnished wood effect.

I always end up with wobble using printed wheels. I guess with me it's from using a bench vice rather than a proper wheel press.

Looking good. I wouldn't worry about the passengers having to duck to enter, most early railmotors were tiny things, look at the size of the Wee Donegal's first one........

Laser cutting has a lot to recommend it for model making, especially flat panels.

metalmuncher wrote: ↑Wed Jun 29, 2022 10:08 pm the idea was to hold the wheels with superglue, but it wasn't very strong and was difficult to keep everything free. The slightest knock and the quartering could go.

As you found out, superglue is useless as a retaining compound. I use Loctite 601 for fitting metal wheels to axles on live steamers, but I've no experience of using it with plastic wheels. The current equivalent is Loctite 609, I think.

The d shaped axle is self quartering and probably as good as anything else you could use.

I don't like the look of the wheel flanges though, too thick and what looks like a ridge on the front face. I'd be giving them a skim in the lathe, which should reduce any slight wobble as well.

metalmuncher wrote: ↑Wed Jun 29, 2022 10:08 pm So that's where we're up to today, tested ok pushing one of the coaches up the section of track clear of vegetation, just needs a bit more traction, some lead weights might help.

Plastic wheels won't be helping traction, but lumps of metal for the cab control panel and drivers seat will sit over the power bogie and should do the job.

Regards,
Graeme

Good points there Graeme.

The wheel profile is mostly to the 16mm association spec, so 1.5mm flanges:


They are only 20mm diameter on the treads, so that might be causing the flanges to look a bit big compared to more standard sized wheels.

These were supposed to be test pieces, printed at a coarser layer height resulted in that step in the flange.

I did actually try turning some of these plastic wheels. The surface finish left a lot to be desired. The form tool has clearances but no top rake, not very sharp, so probably not ideal for plastic. This was with some matte black filament though. Turing the grey stuff seemed to go a bit better. Might give it another go this weekend. If the wheels are painted black before turning, the turning will expose the grey on the treads and flange, might look a bit nicer for not much effort as well.

Sounds like a plan.........


I use the G1MRA coarse profile, which is pretty much the same as the SM32 one you use. I use a simple rounded tool to turn the tread and form the flange root radius, then a file to chamfer the back and round the outer corners of the flange. Form tools and I don't get on well.

I've never machined any printed plastic parts, but FDM prints are effectively sintered plastic, so I wouldn't be surprised if they won't machine all that cleanly. I've seen solvent used to smooth out the surface on FDM prints, so see no reason why it wouldn't work to smooth out the tread of a printed wheel after turning.

Interesting idea to print wheels in grey plastic and leaving the tread unpainted. The only plastic wheels I use are Binnie curly spoke type on timber bogies. The wheels are moulded in black, so I paint the treads a metallic grey. They look good for a while, but the paint inevitably wears off.

Graeme

GTB wrote: ↑Sat Jul 02, 2022 4:13 pm
Interesting idea to print wheels in grey plastic and leaving the tread unpainted.

I tried this once, using the resin printer rather than FDM, and wasn't over happy. The resin is a bit paler grey than many filaments, and the black is only crudely applied, but it doesn't look realistic to my eyes.

philipy wrote: ↑Sat Jul 02, 2022 5:49 pm I tried this once, using the resin printer rather than FDM, and wasn't over happy. The resin is a bit paler grey than many filaments, and the black is only crudely applied, but it doesn't look realistic to my eyes.

The light grey looks more like aluminium than steel. In the distant past there were aluminium wheels avaiIable in HO, which were all I could get at the time. They looked awful and I rapidly changed to blackened brass........

Treads need to be dark grey, metallic if possible and I now use Humbrol #53 when I paint log bogie wheels. I tried Humbrol #27003 'polished steel' from the Metalcoat range, which looked good when newly applied, but wore off too rapidly to be useful when run regularly. The bogie in the first photo was done with Metalcoat, but I couldn't find a closeup of a more recent build. The second photo shows wheels painted with Humbrol #53, but out on the track.






Paint sort of works for rolling stock, but I'm not sure I'd use it for locos. I think it would be gone the first time the wheels slipped.

Graeme