Garden Railway Forum

Back in January I fancied building some new stock and decided to start with a PO van. The only 'industry' I have is a windmill and a water mill, so a milling concern had to be the obvious ( if slightly OTT) owner. The design is not based on any real prototype, just a typical generic van.

Some months ago I drew up a van for complete 3D printing, but having done an experimental partial print I came to the conclusion that it was not really the sensible way to go, requiring far to much cleaning up. So, for this one I decided that the underframe was printable and the strapping would be do-able, but the body would have to be a standard HIPS box with scribing for the planking.
I started with the chassis and integral axleboxes.
This gave no real problems until I did a trial fitting of the wheels. I had some SwiftSixteen wheels in stock and 3mm steel rod for the axles, but the problem I discovered was that the solebars were too rigid to flex outward and allow the axles to drop into the holes printed in the axleboxes, as I had planned!
I thought that I was going to have to rethink and print the axle boxes as separate items and then glue them on, trapping the axles on the way. Then I had a flash of inspiration and remembered that Swift Sixteen wagon kits have their axles running in brass tube held in a triangular mounting which is fitted to the underside of the vehicle floor, between the solebars, and that is easy to replicate as a 3D printed item.
In order to keep it central when fixing, I added two extensions on each side to hold it central and square to the solebars.
However, having done the trial print (above) to check viability, it dawned on me that it didn't have to be a big solid lump between the wheels so I removed the centre section, just leaving two relatively thin holders for the brass tube.
That seemed to be fine, but when fitting it to the frame (still on the computer 'drawing board') just to check things before finally printing, I accidentally slid one a couple of mm further along than the other, and that gave me yet another idea! So I added a couple of lengthways extensions to sit behind the headstocks, thus ensuring that both ends are exactly the same distance from the end, and square and central.

We've all seen rigid chassis 4-wheel vehicles lumping and bumping through pointwork and uneven rail joints and I've often thought back to my P4 days and wondered why nobody uses 3-point suspension in the larger scales. Well, looking at my axle holder, it dawned on me that the computer could easily split it into two so that one part could rock inside the other, similar to the etched brass units used in the smaller scales.
More to follow in Part 2....

Phillip - a touch of genius with the extra alignment bars to ensure a correct, square, equi-distant fit - and I like the fact the centre lump is cut away


I know you don't 3d print to make money but the Intellectual Prop on this could be valuable?????????

I like the compensation arrangement. Does it work on both ends or just one?.

Gralyn wrote: ↑Tue Mar 13, 2018 4:04 pm I like the compensation arrangement. Does it work on both ends or just one?.

Just one end. The whole point of the system is that effectively it creates a "3-legged stool" effect. At one end you have both wheels on the track and at the other end the vehicle is supported only in the centre so the wheels go up and down independently of the body orientation.

The buffers were printed separately to the underframe, because it is easier to print and gives a better finish with the slot facing upwards, so these were glued on prior to the body being attached to the chassis.
The next step was to draw and print the van strapping. Both sides and both ends are identical, so only need one drawing each. The straps are 1.5mm thick and this did cause problems of adhesion to the bed in some places. The net result being a rounding of the lower square corners, which required some careful filling with Squadron White once fitted to the body shell. The strapping print also included the bolt heads, door hinges and the door fastening bolt, all of which printed perfectly, much to my surprise.
The chassis was sprayed black. The body was sprayed a cream colour and then glued to the chassis.

The roof is a piece of thin ply, glued on and covered with some fine weave cloth then painted dark dirty grey to simulate tarred canvas.

Having done all that, the two wheel assemblies were finally glued to the floor of the van, between the solebars.

I was fairly pleased with the end result, but looking at it I felt there was something missing..... brake levers! So, back to the drawing board. I wasn't very hopeful about printing these because the V-hangers and brake levers are very fine. It took me several goes to work out how to get the printer to cooperate, but the end result is fairly acceptable. I'm not sure how robust it will be and its probably not the best way to do it ( I think next time I'll use brass strip for the levers at least), but all part of the learning curve. Once the brake levers were glued on, it became fairly obvious that there was nothing for them to do, so Brake Blocks and hangers had to be drawn and printed.
The final touch was PO livery.

Nice combination of old and new modelling techniques. And nice end-product. It’s a shame that P.O. vans were rare on narrow gauge, there is something about a train of P.O. wagons that is very attractive.

Andy

Wonderful to see your thought process in action producing well designed items to a satisfactory conclusion. The finished van is a triumph and a great prototype for many to follow.

I like the suspension idea as well.

RylstonLight wrote: ↑Tue Mar 13, 2018 5:39 pm It’s a shame that P.O. vans were rare on narrow gauge, there is something about a train of P.O. wagons that is very attractive.

Andy

Yes, I'll restrain my muti-coloured train instincts!
However, the thing is that Bench Mills Ltd is about the only part of the Bench Hall estate that makes any money, so Lord Elderbury, who was a late convert to the financial benefits of the railway, likes to shout his wares as much as possible, to attempt to divert attention from his otherwise rather pecunious state.

A brilliant design process Philip, and a very professional looking end product. The way it evolved from one step to another, the detail, the livery, everything just perfect. You have been busy.
Grant.
PS I confess I first thought this to be about a Post Office van

LNR wrote: ↑Wed Mar 14, 2018 12:22 am You have been busy.
Grant.
PS I confess I first thought this to be about a Post Office van

Ditto however having said that, I love the finished van - I do have a brewery on my line so I do have an excuse for some Private Owner vans

philipy wrote: ↑Tue Mar 13, 2018 1:30 pm Some months ago I drew up a van for complete 3D printing, but having done an experimental partial print I came to the conclusion that it was not really the sensible way to go, requiring far to much cleaning up.

The model has come up very well. I also thought Post Office when I first saw the heading, as the nearest equivalent here in Oz was known as an advertising van.

That's a much more rational use of rapid prototyping than I usually see. Too many people get hung up on printing a one piece body and the result is a model where it is impossible to get a good surface finish.

I seem to remember you use a filament printer. Out of curiosity, what polymer did you use for the model and what do you use to glue the parts together?

Being me, I'd have probably fitted short lengths of brass tubing into the inner axle supports to act as bearings, as I don't have a lot of faith in common polymers like PLA and ABS when used for bearings. Might be OK though, if lubed with a dry lube like powdered graphite or teflon, instead of oil.

Regards,
Graeme

GTB wrote: ↑Fri Mar 16, 2018 1:19 pm

philipy wrote: ↑Tue Mar 13, 2018 1:30 pm Some months ago I drew up a van for complete 3D printing, but having done an experimental partial print I came to the conclusion that it was not really the sensible way to go, requiring far to much cleaning up.

That's a much more rational use of rapid prototyping than I usually see. Too many people get hung up on printing a one piece body and the result is a model where it is impossible to get a good surface finish.

As I said, far too much cleaning up needed. Although I drew up a complete van, I just printed one quarter. It took forever ( about 15 hours from memory) and this was the result!:

GTB wrote: ↑Fri Mar 16, 2018 1:19 pm I seem to remember you use a filament printer. Out of curiosity, what polymer did you use for the model and what do you use to glue the parts together?

For this I used PLA filament and for glue I use a product called EMA PlasticWeld which is basically Methylene Chloride/Dichloromethane

GTB wrote: ↑Fri Mar 16, 2018 1:19 pm
Being me, I'd have probably fitted short lengths of brass tubing into the inner axle supports to act as bearings, as I don't have a lot of faith in common polymers like PLA and ABS when used for bearings. Might be OK though, if lubed with a dry lube like powdered graphite or teflon, instead of oil.

I did think about using two short lengths of brass tube, effectively bushes, but not being 100% certain that the two holes would print in perfect alignment, I decided that one tube would get around that by forcing the plastic to deform as necessary.

I am very impressed. I like van trains so this is right up my street.

Ian