7mm Mickoo's Commercial Workbench

[mickoo]

Would 3D printed wheels be replaceable with commercial offerings if there was a problem with them?

Not really, the raison d'etat for 3D wheels is to offer something not commercially available or replace poor commercial options.

Plus if there's a problem with them you just print new ones and by the time there is likely to be a problem with them, printers and materials will have advanced, therefore the next problem will be even further away.

There are folks who will take the chance and give it a go, you only have to browse railway forums, websites and Facebook pages to see a rather large populous that already is and then there are those who won't. No point trying to articulate to those who won't, far better to expend energy with those that will and advance the technology and ideas.

 

[Clarence3815]

Thank you.

Bernard

 

[oldravendale]

There are folks who will take the chance and give it a go, you only have to browse railway forums, websites and Facebook pages to see a rather large populous that already is and then there are those who won't. No point trying to articulate to those who won't, far better to expend energy with those that will and advance the technology and ideas.

IMHO, Mick, you are right on the money there.

Brian

 

[3 LINK]

Going back to the discussion regarding pick ups, on my last build which was a 2251 class, I decided to fit working valve gear, thus limiting where I could place any plunger pick ups, or wipers on the backs of the wheels. So I decided to try the American pick up option, and I can honestly say it was straight forward and the loco runs so smoothly without any hesitation. Apart from making a paxolin draw bar and insulating the footplate cover with a smear of araldite, that was it. I don’t intend to double head the loco, so I have left the buffers without insulation.

I had one slight hiccup as in the loco would run fine in both directions, but would stop dead over any turnout. The rest of my locos transversed the pointwork without problem. That evening I ran the loco in the dark to see if I could see any sparks, and bingo ! It was the front vacuum pipe drooping a fag paper too low and was just brushing the top of the pointwork !

Cheers, Martyn.

 

[Tim Humphreys ex Mudhen]

With a tender loco my preference is to pick up power via the tender wheels, preferable split axles using Slaters components.

Tim

 

[simond]

With a tender loco my preference is to pick up power via the tender wheels, preferable split axles using Slaters components.

Tim

I did something similar with my 28xx. Split frames, spilt axles, all sprung using PB wire. Shorted slater’s wheels, split slaters axles.

I try to fit loco pickups, as it’s easier to test run, but use additional tender pickups whenever I can.

 

[mickoo]

I have no aversion to the US pick up style, it's actually very convenient and simple, just an insulated draw bar or more as likely an insulated bush 3D printed to suit. Few people double head and most clients who send single insulated AGH are aware of the issues anyway. Insulating the tender chassis is perhaps a good idea but I've never been asked to apply it.

 

[adrian]

Very shortly the solution will be 3D printed wheels inside turned rims, there's already plenty of materials out there with the strength and durability, the only unknown is material stability and longevity but that will come and it will come very quickly I foresee.

I have a couple I've been dabbling with in the background, ironically planned for split axles but you could easily print the Slaters square end for quartering, in fact I might modify the design and do a set as a trial.

What about an alternative? 3D print a mould such that it holds a steel turned tyre and a brass center bush in alignment, maybe a cranpin insert as well, then allow castings of a harder resin or even whitemetal for the spoke and rim arrangement.

For another project I've been looking at what they are doing for 3D printing moulds for laying up carbon fibre panels. So for things like the etches for the ROD tender flares - maybe the solution is to make a mould and layup a resin carbon fibre panel instead. There's quite a few things where people are trying to 3D print quite large thing panels without distortion where I think it might be easier to 3D print a reverse mould and produce the finished article using some form of fibre reinforced resin panel.

 

[mickoo]

What about an alternative? 3D print a mould such that it holds a steel turned tyre and a brass center bush in alignment, maybe a cranpin insert as well, then allow castings of a harder resin or even whitemetal for the spoke and rim arrangement.

For another project I've been looking at what they are doing for 3D printing moulds for laying up carbon fibre panels. So for things like the etches for the ROD tender flares - maybe the solution is to make a mould and layup a resin carbon fibre panel instead. There's quite a few things where people are trying to 3D print quite large thing panels without distortion where I think it might be easier to 3D print a reverse mould and produce the finished article using some form of fibre reinforced resin panel.

Yes that would work but if I'm understanding it correctly you'd still have a flat back to the wheel and spokes, you could do a two part mould but not sure is the filler material would reach all the extremities and you'd end up with a joint line down the side of each spoke.

For the tender flares I'm just going to make a male/female 3D print with alignment holes between the tow and space for the flare, FNG will easily form 0.2 mm brass in a vice between the two, a block 10-15mm deep is incredibly robust.

 

[mickoo]

Back to the 3D wheel, I had a cup of tea and juggled the mind model into something workable and set to.

The concept works fine, the material is actually a lot stronger than I imagined, I did give it some grunt pushing the core in past the rear retaining lip but it held and dropped in, I did have to take a bit off mind (hence the gap in the rear surface) so will redo the 3D core to expand that diameter to compensate. I may take a waft more off to make it a tad easier pushing the core in.

I'll also add a rebate at the front to allow the whole lot to move forward about 0.3 mm to reduce the rim step at the front.

I also need to sort the artwork for the hub beading and blend it better with the spokes, Autocad is not very good at that, in some places it's brilliant, in others 'computers says no'.

There's a little bit of layering on the rim, you can't be away from it with shapes like this, but this was printed at 50 microns, 30 and maybe 20 will mitigate a lot of that in final runs.

 

[Dan Randall]

Nick work Mick.

I’ve done something similar for an Andrew Barclay fireless loco - Dave Summers and I, both have the kit in our respective stashes. Dave bought his first, but when he showed me a picture of the recommended Slater’s wheels (with their eleven spokes, rather than the seven of the prototype), I had to do something about it - they looked awful!

Dave had several sets of wagon wheels (not Slater’s - Gibson, maybe?) and with the loco wheels being the same diameter, give or take an inch, I drew up some new centres in Fusion 360 and inserted the printed centres into the steel rims….



I also made some split-axles and shorted out the tyres by incorporating a shallow groove around the perimeter of the print and passing some springy copper wire from the groove and down a hole through the centre of one of the spokes, where it makes contact with one side of the axle.

The project’s a bit of a slow-burner, as I’ve been dissatisfied with several aspects of the kit (which has been around a good few years, to be fair), so as you yourself tend to do, I’ve been drawing/printing quite a few replacement parts…

David Lane has had a lot of success with 3D printed wheel centres in 4mm scale/S4, so I figured it would be just as viable in 7mm scale and if I can find a decent drawing of a GWR “Castle” wheel, I’ll take a stab at that too.



Regards

Dan

 

[Clarence3815]

What is your prototype wheel Mick?

 

[Rob R]

Mick,
That wheel certainly looks the dogs doodahs.
Resin wheels are tougher than you think, once the paint is on to keep the UV off I suspect only gravity will do them in - and the rest of the loco with it.
Good stuff - keep going.

 

[SimonT]

For the tender flares I'm just going to make a male/female 3D print with alignment holes between the tow and space for the flare, FNG will easily form 0.2 mm brass in a vice between the two, a block 10-15mm deep is incredibly robust.

You ratbag
That's been my mind problem to keep me awake during the many journeys to and from the hospital! I shall find another one to ponder and await your reports. My need is for the flares on the 2000G Dean tender. Consumer research at Stafford revealed that no one likes castings and fingers/solder are so 1980s!

 

[mickoo]

What is your prototype wheel Mick?

Darlington 4'-7½" wheel for LNER J27, A7, A8 and any other engine that had that wheel.

 

[mickoo]

You ratbag
That's been my mind problem to keep me awake during the many journeys to and from the hospital! I shall find another one to ponder and await your reports. My need is for the flares on the 2000G Dean tender. Consumer research at Stafford revealed that no one likes castings and fingers/solder are so 1980s!

Sorry..... I too have mental conundrums to ponder to while away the boredom of long distance driving

My problem is finding the time to apply the solutions

 

[3 LINK]

David Lane has had a lot of success with 3D printed wheel centres in 4mm scale/S4, so I figured it would be just as viable in 7mm scale and if I can find a decent drawing of a GWR “Castle” wheel, I’ll take a stab at that too.



Regards

Dan

Cadbury Castle if I remember correctly, and there’s me thinking how long it takes me to complete a build !

Regards Martyn.

 

[mickoo]

So we're on Mk II now, quite a few evolution changes and a new sub design to fit direct onto Slaters axles. I've also added the balance weights and dropped the idea of the rebate at the front to fit into the front retaining lip; in the end I just machined the front lip back to 0.2 mm (2nd picture) thickness, it looks so much better.

Pressing in the cores is still fraught and some damage invariably occurs so I'm probably going skim some more off the rear retaining rim (we're talking 0.1-0.2 mm) so the core just 'snicks' in.

If I used a more pliable resin that might not be necessary; one thing to try is a mix of FNG with tenacious to achieve just that, you do loose a little detail but there's virtually no detail on wheels to loose so it could be a winner.

Mk I had a 0.1 mm run out and that was consistent with the axis of orientation (SLA printers naturally want to print banana's is a key thing to remember) so it was a simple task of moving the axle aperture in the opposite direction by 0.05 mm, run out is now 0.02-0.03 mm which I can live with.

The next problem, again linked to the way SLA printers work is a slight wobble, the axle to wheel is not quite 90°, it's about 3-4° out so the task now is to find in which axis it's out and then reverse tilt the axle hole in the core; that way when it prints it'll be a true 90° to the wheel.

You can of course easily counter that with the solid axle version by chucking it up and reaming a pure 90° bore, you can't do that with the Slaters square spigot fixing.

One final tweak was to rebate the heavy duty crankpins so the enlarged boss sits just proud of the wheel boss. The Slaters set are drilled and tapped 12BA with top hat bearings as is the usual way; I prefer 10BA and tapped top hat bearings so that'll be a third sub variant.

I've not fully cleaned up the rear faces, no need as these are going straight in the bin.

More to do.......

 

[OzzyO]

Hello Mick,

the one loco that could really do with a good wheel is the L.M.S. Princess, as the Slater's wheel doesn't have the correct number of spokes. I did have a word or two with David (forgot his last name) about these wheels and he said that they were correct (the Sharman book is wrong on this class of locos) and his book is the one I think Slater's used. Sharman Princess 6'6" PB 21 spokes, The photo below PB 20 spokes & bevelled rim,


6202 below 20 spokes with strengthening webs PB, & bevelled rim,


Duchess 6'9" wheels 20 spokes (Sharman book 21 spokes) Slaters 21 spokes. I maybe wrong on the number of spokes on this loco as I have picked a bad photo with the speedo bracket in the way.


Mick if you do a set for a Princess I would be very tempted to put my hand in my pocket.

ATB

OzzyO.

 

[Pencarrow]

Hi Ozzy, the princess / turbomotive looks like 20 spokes. Confirmed because opposite spokes align in a straight line.

The duchess looks to me to have 21. It's certainly an odd number as, to my eyes, opposite spokes are offset from a straight line.