LNWR Prince of Wales - a 3d printing project

[81F]

Just got the test print back ordered on the 6th March and  the cab handrails actually printed. Sadly the steps look too narrow so my latest version has this widened slightly. I've also added more detail on the boiler and enlarged the secondary splasher over the con-rods to accommodate some beading, correct an error in the curved bit at the front and give more clearance for the con-rods themselves.

Although the body now sits level it tends to rise up at the  front when I tighten the body screw so Ive lowered this again by around 1/4mm since this reduced the problem compared with the last print.

Sadly the chassis extension is too short and slightly too thick to fit in the slot in the body so I've increased the height of the slot and lengthened the extension which might also stop the body from lifting when the body scre is tightened.

In addition, I have discovered that the buffers had six rivits to hold them onto the buffer beam rather than so I may decide to reprint these if I find any other problems with the brass fittings.

As soon as the light is good enough  and I have time to take a picture I will post one.

[What About The Bee]

Hi 81F

Cannot wait for the pictures!

Perhaps a boss or hollow column around the screw?  The column extends all the way to the surface the screw screws into. Thus when the screw is tightened, it merely puts the entire column in compression without deflecting any material.    Just a thought.

Bee

[81F]

Many thanks Bee,

Just been probing around at the back of where body and fount that there is a slight step (see below) between the internal rear surface of the cab and the lower part of the body. Although this cannot be more than 1/2mm it is probablt just enoght for the body to pivot upwards as the screw is below it.

I have fixed it now but probably too late for the latest test print 😞  

[What About The Bee]

½mm?  Yes, that would do it.  An excellent demonstration of a lever.

Reverse engineering is always tricky.  It took me three passes to properly interface the body clips and screws with the Era 1 chassis (hopefully only 3, prints due soon).

Every person who moans about how long Hornby takes should be sentenced to this development process, so they can see just how difficult it is.  The moaning would stop, forthwith.

Bee

 

 

[81F]

Sprayed the  body gloss black last night to show up any blemishes only to find that the top of the chimney is totally flat without the capuchon and ridge around the top. This would explain the loose washer floating around the bag when the print arrived.

Thankfully before I ordered a revise print last night Shapeways diagnostics picked up the "loose shell" so I hope I've fixed it.

Sadly the paint is still sticky so I won't be able to photograph it before I loose the light, so will use the time to try and remove the paint from the Bachmann tender top I intend to use before moving onto some coal rails.

[81F]

Sadly the paint has now pickled on one side (hence only a view of the left side. However as this was just a test it doesn't really matter. However, I think it shows that I will need tpo do the final print in a fine detail plastic rather than PA12 which is a lot cheaper.

However, I have been working on the tender and will probably use the 21 pin socket in that to convert to DCC so have designed a new drawbar to link the B12 Chassis to the Bachmann G2A tender. A test print is being made by Shapeways (in PA12 plastic) but I will probably do it in brass ones I have checked the clearance. At the moment the tender is coupled using a spare Triang/Hornby Hall drawbar but aside from being a bit sloppy the tender also looks a little distant.

I have also added some more detail to the boiler and hopefully resolved the problem of the missing chimney top but I will not know for sure until my next Shapeways delivery towards the end of the month

I am still not sure whether to add the chassis above the pony truck to the chassis extension or the body, but the photo clearly shows it is needed.

Edited April 5 by 81F

[What About The Bee]

Hello @81F

Sublime!

In observing photographs of the real thing, the space above that front pony truck does need your attention.

You asked "on the chassis body or the extension?"  I would suggest a combination.

The front buffer beam in fine detail plastic will be incredibly fragile.  It needs a bit of support.  May as well make that support into some of the body exposed to view.

Yet the real article likely never went around curves we have.  Some of the real components obviously moved with the truck, not the body. Putting modeled components on the pony truck needs accommodation of our curves.  While adding to the complexity, the result will be fantastic.  

If you do not have the front pony truck and the attaching bar in your model yet, it may be time to do so, so as to permit proper engineering of the motion / articulation.

The current state of the model has high fidelity with the prototype.  Well done 81F!  The model is an excellent match to the photographs.  Keep going!!

Bee

[81F]

Thanks Bee for some thought provoking comments.

My intention is to re-use the B12 pony truck, although I am toying with the idea of getting some slightly larger diameter wheels. At 3'9" the prototype's would scale to 15mm whereas the B12 model's are only 13mm. However, do you think raising the front coupling by 1mm is likely to cause trouble with it operationally, although I could probably mitigate some of the additional height by replacing the plastic one with a metal version and bending it down slightly?

You make a very good point about the strength of fine detail plastic. My thoughts about the frame is to follow Triang's example with the B12 and add the frame detail to the body and have cut-outs over the wheels (see blue in image below) . However I would reduce the cut-outs radius sit the edge is much closer to wheel flanges. The ones on the B12 feel around 2mm above the flanges of the wheels so I think I'll try reducing this to around 1mm.

Once the dummy frames have been added I will probably also thicken up the material between them where it cannot be seen.

Depending upon what I find when my most recent test print comes back I will look again at lowering the body to match the Bachmann tender. I will also have to lower the steps so they match up with the tender. On the model in the photo, the running plate is about 1mm too high whereas the bottom step is about 2mm too high.

This will probably mean yet another test print with a boiler cut-out to check the clearance from the top of the motor. However I will take the opportunity to try out the alternative front end detail shown above. 

 

 

Edited April 5 by 81F

[What About The Bee]

Hi 81F

Adding that blue sub-frame over the pony truck is what I had in mind.  Lots of stiffness added to the front buffer beam, even without filling in the gap between them.

You wrote: I would reduce the cut-outs radius, sit the edge much closer to wheel flanges. The ones on the B12 feel around 2mm above the flanges of the wheels so I think I'll try reducing this to around 1mm.

This may be more troublesome than at first glance. 

Consider the case of entry to diverting route on a point.  The front pony truck bouncing through the rails and frog, as the locomotive trundles on. The pony truck pushed to one side.  That extra 1 mm of clearance might be needed.

I'd like to think that the engineers at Triang knew their stuff.  They had the gap set for reliable running, maybe not so concerned about appearance.  Yet you have a drafting tool they could only dream of.  Set the articulation of the truck for the tightest turn in the model and check those clearances!

As to the coupling being raised, you have far more experience and knowledge than I do on this matter.  I will defer to the expertise of others, instead of a glorious demonstration of my naivete.

Bee

 

[81F]

Just been notified that my latest test print left the Shapeways in the Netherlands this morning. Much earlier than the previous estimate of 26th. I hope this time the body will fit securely enough on the chassis for me to test run on the Rolling Road to check con-rod clearances and height above rail level when the fixing screw is fully tightened.

However, this is the print before  I added the frames shown in blue so I will still have at least one print before I'm ready for the final (and more expensive) fine detail plastic.

[81F]

After some delay, the print mentioned above arrived Tuesday.

I've almost got the height right but still some work to be done. The tender draw bar is too short so I have now lengthened it slightly, Also it has a tendency to lift the front of the tender so have made more modifications to resolve this .

The crank in the chassis extension that I made to replace the original B12 one is still too much as it continues to lift the body slightly and to pops out as it is fractionally too short, so I have lengthened this this and reduced the crank. Hopefully this will push the chassis back and allow me to tighten the body screw which will reduce the amount the front bogie appears to protrude.

If I remove the tender coupling and pushr down on the body so that its level, the running plate seems to be around 1mm to high, while the top of chimney is also about 2mm higher than it should be. I will therefore reduce that by 1mm. Hopefully lowering both the body and the chimney will bring it back to within loading gauge.

On the rolling road there is a regular knock so I will be increasing the clearance above the con-rods. Another modification I have already made to the virtual model iks to lengthen the steps so that they should line up better with those on the tender.

I will ultimately make two versions of the body, the one shown which is in a later condition while the other will be in original condition, and it will be this one that goes for the next test print as I just have to switch in a new smokebox saddle and switch off some pipework on the boiler

Edited April 25 by 81F

[What About The Bee]

1 hour ago, 81F said:

Looking good 81F!

Bee

[81F]

Been studying the pictures a bit more and noticed that several of the Prince of Wales class had coal rails on the tender so will need to develop some. Possibly in Bronze as these look quite fine and would probably snap in detailed plastic.

[81F]

The new Chassis extension and tender drawbar arrived today. The latter no longer lifts the tender and holds the tender away from the body ans swings more freely. However it only just goes around small radius PECO streamline points so have made the virtual model 1mm longer ready for the next print.

However as shown above, rear of the body is effeminately 1mm too high. Also the chassis extension needs further modifications to lower the front. Unfortunately the body is also too short for the chassis so I will need to compromise and stretch the whole thing by a mm or so. I will achieve this by moving the smoke-box 1mm further forward and stretching the boiler. As well as moving the bufferbeam 1mm further forward I have also made it slightly thicker.

I am now uploading the new body onto Shapeways and running the automatic checks.

Edited April 30 by 81F

[threelink]

@81F. That is a stunning looking loco already. Can't wait to see the finished article. 

[81F]

Many thanks Threelink. Still a few more test prints to do as I am not sure if the motor is hitting the top of the boiler so I have uploaded a couple of sectioned virtual models to see what clearance there is above the motor. I will also use these to see if I can get an old X04 powered chassis into the body.

One of the files has what I think is an earlier front end while the second is the later version like the one above except I have lengthened the body as the one above is a little too short for the chassis.

Spent the evening going through the virtual model tidying up the inside and making it much smoother. Hopefully that will fix the knocking as there was a tiny bit of plastic sticking out that may have been getting in the way of the con-rods.

 

Edited Friday at 22:49 by 81F

[Aussie Fred]

Just curious, What do those "test prints" cost a pop, I thought it was quite expensive, well, here in Aussieland not that cheap.

[What About The Bee]

Hello Fred

While I have not yet developed a formula for pricing parts from Shapeways, there are some key input criteria

1) Material selection.  You can literally print in gold, platinum, copper or a variety of plastics.  Each has a different unit cost.

2) Spacial volume.  The part occupies a space in the print volume.  A cubic extremity is computed by Shapeways.  You pay for this.

3) Part volume.  How much material does your part consume, independent of occupied spacial volume.

4) Minimum price.  I have yet to be quoted a price under 5 USD for any part, no matter how small it is.  

5) Express handling. Shapeways will do a hurry up, but you pay for it.  I always skip this.  

6) Shipping and overhead.  This fixed price is added to each order, independent of the number of parts.  Once I figured this out, I always gang many parts together.  It is a big cost increment to ship each part individually.

An example: The floor of the cattle waggon needed multiple passes to get a perfect fit.  I chose to make it in fine detail plastic, tan.  It didn't occupy too much print volume, nor consume much material.  I was above minimum price.  I skipped express.  Shipping and overhead was more than the part!  Tax applies, of course.  Each turn was ~30 USD.

Bee

[81F]

My two most recent test prints were only for half a loco so they only cost around £21. but I've been using the cheapest plastic up until now. When I eventually print the final version in detailed plastic I expect it will top £70

[Aussie Fred]

Thanks Bee and 81F, just curious, as it it way out of my league (thinking wise)

[What About The Bee]

Happy to help Fred.  

When I first started the printing portion of my exercise, I thought to myself: that seems a triffle high.  But I came to realize that their staff deals with the physical printing, the chemicals, resins and etc.  I never have to worry about room temperature, or print bed parallelism with the horizon.  I need only worry about the design, not the printing process.  If Shapeways says they can print it, they do.

Its also been wonderfully energizing.  I have little expectation that any firm, Hornby included, will ever cover all the LMR carriages.  Yet now?  No worries, I can make the ones I want. 

Top row, center: Even the first class Lacey and Allen Carriage.  I believe the LMR had two of these.

And I have not forgotten about LMR locomotives.  I do expect Hornby will do Planet someday, but Twin Sisters?  Never.  Experiment?  Never.  Caledonian?  Never.  So as I gain experience, I can see locomotives in my future. 

Just as 81F is doing now.  

Bee

[81F]

@ Bee, I wish I could say that no manufacturer is ever likely to produce my models. I did a GWR 517 once for a Hornby 14XX chassis and just discovered that Dapol are to produce one!

Thankfully it is a slightly different version to the one I wanted so all is not lost.