W&U Tramway coach, using 3D Printing and the Cameo cutter

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If you've seen my mention of this in another thread you'll have seen that Nickbrad supplied me with some drawings and Info. One of the things that came to light from this is the dimensions of the bogie, wheelbase 3'7" wheel diameter 2'9". My maths can just about work that out that there's only ten inches between the wheels, not allowing for flanges. No one does a bogie quite that short so I'm going to have to make one, unless some one can tell me that the reconstituted coach uses more modern longer bogies. Before I had the dimensions I knocked out a rough model of the bogie, here it is

bogie.jpg (40.74 KiB) Viewed 2677 times

It's sitting on the drawing, and you can see that the original prototype was shorter. Now do I insist on accuracy, I can probably slim down the bolster in my design, then I can move the wheels closer together, but only making one will tell me if it will be strong enough and the ends flexible enough to get the wheels in, and how it will run will be the big gamble.
I think that the shorter the bogie wheelbase the bigger the angle of deflection can be before the flanges take effect. Will I be wasting my time trying to produce a scale length bogie?

[Bigmet]

Provided the bogie frame is stiff, fairly easy when it is so short; then with practically no sideplay the wheel coning will do the work of steering the bogie properly. How to get the wheels into close fitting bearings in what is already a fairly stiff bogie? Drill the holes to take flangeless bearings right through the frame of the 3D printed piece. Move one wheel in each set undergauge, feed in the long axle end, then engage other axle end, regauge wheel set. Feed in the bearings one side to correct position, secure with smear of Araldite down locating hole, allow to fully cure. Repeat on other side. (I'd make the bogies from thin folded metal sheet for choice. The wheels will go in easily before the stiffening bolster and pivot (and quite possibly tie bars over the outer ends) are soldered on for a really sturdy job.)

There are dodges you can tinker with to avoid the difficulties of wheel insertion and a pivot on an ultra compact bogie.
Fix the inner pairs of wheels in the frame, pivot the outer pairs as pony trucks.
Fix all the wheels in the frame, allowing a bit more sideplay than normal. (Eight wheel coaches without bogies were tried, the ride was apparently both 'rough' and 'exciting' on occasions.

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Yes used to push bearings in from the outside on the old Triang solid bogies, when fitting them with Peco nylon wheels, but I have a cunning plan. The new frame built for the old body runs on "modern bogies" according to the website. Given that the flanges are slightly oversize, I think I'll go for a 10mm nominal wheel which will give a bit more space in the centre and allow a sturdy construction. I'm planning to 3D print the bogie, I'll make the side plates thinner and flat to allow the wheels to be sprung in. I can then print a detailed side frame lying on its back (best for printing) with holes through the axle boxes to take the bearing cups. A touch of countersink on the backs will allow flanged cups to be used. Then bond the detailed sides to the bogie stiffening it and holding the pin point axles in the cups. If I can't find the wheelbase of the modern bogies by any other means, I might be able to blag a trip at least halfway to the North Norfolk to measure them myself.

PS pushing a 2mm disc straight through the sides of a chassis on the 3D model and seeing two perfectly aligned 2mm holes appear after having sweated to drill the same things yourself is still a novelty.

[Mountain]

Bogie looks good.

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I've decided that this is a workbench activity, so I've shifted it into the workbench forum. So I'll be trying to document the steps as I do them in here. First off is to say I'm using "Design Spark Mechanical" the free version from RS. The free version has had some bits removed, you'll probably find some annoyed freeloaders complaining about it, they've taken out the Flip/Mirror option. There's a work around if your object is symetrical about two axes at right angles, as you can draw a quarter of it, copy and rotate it, stick the two bits together copy. rotate and stick again to create the whole thing. Otherwise you'll just have to draw the reflected version. It's so easy to draw it's hardly a bind.
I'm starting with the bogie so here goes. This is the software I will be using.

Here it is having dismissed the start page, you have to let them try to sell you something after all.

It's time to draw something. The first thing to settle is how close I can get the chosen wheels to each other. The prototype has 2'9" wheels on a 3'7" wheelbase bogie. The wheels I have are 11.9mm which is a bit overscale but they have fairly fine flanges so the first thing to draw is a side elevation with the wheels in their correct positions, to see how to fit the bogie spacer inbetween. I'll just nip off and do a bit of drawing.

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On with the drawing. Here I create a volume in which the bogie will be drawn, some corner of the envelope calculations say it needs to be 22mm wide, (I intend to add decorated sides later) and 30mm long, so I draw a rectangle that size.

and 10mm thick should be more than enough. So I use the "pull" tool to raise the top surface of my rectangle by 10mm.

now I need some working geometry, the first thing a bogie needs is it's pivot point. I could put a vertical construction line straight through the middle of the space but what's wrong with putting in a more useful 1.5mm hole. Looking at the plan view I draw a 1.5mm circle then swapping back to home view I use the pull tool to push the disk down more than 10mm. Presto I have a hole.

Don't take my word for it, when I change back to plan view I can see daylight through it. At he moment the most solid thing we have here is the hole, it has all of the attributes of a hole, an empty space surrounded by a surface and you can see through it.

the next step will be to create the axle holes in their correct positions relative to the pivot. Back soon.

[Dad-1]

Some project !!
They say you can't teach an old dog new tricks and that may apply to me,
but you seem to have embraced all this new technology so easily.

Geoff T.

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Geoff - I've got a bit of tidying up to do but I have the next steps through to making a test print, waiting in the wings.
I'f you have done any engineering drawing, mine never went further than GCE O Level, and can use an application like Paint or even just the drawing tools inside MS Word you can find your way around this software, The bit that puzzled me was going from a 3D drawn model to driving the printer. In my case the software that comes with the printer takes care of it. Otherwise a good explanation of what's necessary and where to get the software is all explained in a book by Jeff Geary and Dave Renshaw, (El-Davo of Warton and Cramdin Yard) called 3D Printing and Laser Cutting, A Railway Modelling Companion.
I'll post the next bit some time over the weekend with a picture of the test print.

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Cost is something that's purely relative my 3D printer cost just about the same as I payed three years before for an A3 five tank inkjet printer and every bit of software I'm using with it is free. But I suppose my outlook on prices of such is coloured by the 40% discount the tax man gives us when we set them against my wife's research budget for writing textbooks and exam papers.

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OK axle holes, it's fairly obvious that like the central pivot hole, I'm going to draw two circles, this time on the long vertical face of the block then push them through. The face I need is the "Front" face, so here it is.

I've drawn in the approximate outline of the wheels to see how close I can get to the prototype wheelbase and still have some strength in the bogie's frame. Making the bolster 3mm wide should give it some torsional rigidity. So that guides me to where to place the two circles that represent the axles. Yes it is upside down, that's because it will have a flat top but various cut aways below, so placing it's top on the printer bed will leave everything supported. With the two 2mm circles in place I can delete the outline pof the wheels and switch back to the home view. Pushing the two discs straight through the block is just a repeat of what I did with the pivot hole, Then I swaped to the top view, and started to draw in the bits of the bogies frame.

What you can see here is a circular hollow boss at the centre of the bolster to give the superstructure some stability when running, and an extension from the boss to provide somewhere to anchor a coupler.
Switching again to home view, I've caught the action just befoe I push that orange bit straight out of the block.

You can see that the holes I pushed through from the front will now become the bearing holes in the side frames. The next step is to push down the various bits that aren't needed, then the bits that are, stopping when they are the right size.

Here's that bit for the coupler rediced down to 1mm thick.

I've hit the limit on attachments so I'll carry the next bit into a separate post.

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Carrying on:-
Now it's just a matter of getting rid of the bits we don't need to leave what we do. Push the infill in that centre boss down to level with the coupler extension and it's outer rim to level with the bolster. Switching to the front view I drew on the outline of the bottom edge of the frame, and back in the home view pushed away the unwanted bits. Here it is

This is the point where we have to go for a reality check, That might look like an upside down skeleton bogie, what it is a collection of rendered faces, This is where it has to be handed over to some other software to eventually end up with the instructions to drive the printer. Now my printer comes with a program called "XYZware" it will do all the steps from here once I've exported the design as a .STL file.
The XYZware will first scan the file to make sure it makes sense to the printer and will fix any minor problems. Then it will cut the shape into very thin slices each of which the printer will place one on top of another. The flowing plastic will only bridge a small gap without collapsing that's why I turned it on it's top, the two millimetre holes through the vertical plates are just small enough for the plastic to bridge, much bigger and they would have to be drilled later. The other thing the software can do is add a brim, a thin low density patch surrounding the object helping it to grip the bed and not move during printing. If I didn't have this software I could find programs on line to each do one or more of these final tasks.
So all that's left is to send this file to the printer and wait. Probably just under half an hour. I'll be back!

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Well here it is printed. the first test print, I know there will be things to alter.

As I thought I need to do some fiddling with the distance between the side frames. This is a pretty fundamental measurement if I was making this by any traditional method. But here I have an unlimited supply of virtual copies to tweak and twist until I get it right. I can pull and push on surfaces until I get the dimension that I've determined from the test print. If this had been assembled from stock materials I might have been able to modify the prototype to get the new dimension. Then face the dilemma of should I then use the modified prototype or build from scratch to the revised dimensions. Once I've modified the virtual model I can have a brand new print for no more effort. Turns the old motto of "measure twice cut once" on its head
There's other things I should be doing right now but I'll come back to it and make some tweaks. Once the frame is finished I'll go on to making the detailed sides.

[Dad-1]

Is this Star-Wars ?
All Science Fiction to me, I'm beginning to believe I'm a stone age inhabitant.
Knife, glue, abrasive paper and the Mk.I eyeball ........Chase that mammoth
I'm ready for lunch !!

Geoff T.

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Hope someone is building a great big fire, a mammoth takes a bit of heat to spit roast. I went way and did a bit of tweaking on a copy of the file, and surprised myself how easily you can modify a created object. I probably didn't do it the easiest way, I did it the way I could think it through. Doing my measurements on the trial print, with some axle cups pressed in, I decided the inside of the frames needed to be 5.5mm further apart. As I didn't want the frames to be any thinner the outside surfaces had to be 5.5mm further apart as well. So it went like this
highlight nearest surface.
click on it with the pull tool and pull,
in the box that shows how far you have pulled it type 2.25mm and hit return.
Spin the whole thing around and repeat for the other side.
Manipulate the image with the spin and slide controls to get a clear view of an inside surface.
Click on it with the pull tool, push and type in 2.25mm.
Repeat for the other inside surface.
Lo the sideframes are now 2.5mm further apart.
Here's a shot of the screen at that stage

and here's the next print still attached by its "Brim" to the bed.

As you can see the bed is covered with masking tape, the makers supply 6" square patches (for the American market) but masking tape is just as good if you press the joins down very firmly. It helps the print stick to the bed during printing, and is far easier and less likely to cause damage if it all goes wrong and needs scraping off. Only happened once so far, when I experimented with printing glazing bars straight onto transparency. Next up, the bogie cleaned up, trimming away the brim and smoothing where it was. Then I poked a 2mm rod through the axle holes and forced in bearing cups, once they were started in the hole I put it over a thick washer with about a 4mm hole and pressed the bearing in with the flat and of my tweezers. There's just a perceptible bit of sideplay, the bearings aren't going to fall out, they are an interference fit!

There's still a bit of fettling to do along the top edges, but this rolls so well, (kept rolling out of shot,) that I'll go straight to printing a second one.
The next stage will be printing the detailed sides, springs axleboxes etc, so I have a bit of experimenting and learning to do, I'm more a straight lines and round holes sort of designer so it may be fun.

[TimberSurf]

Would not have been better to print in black?