Went looking for a chute design .. found this one on Google Books .. this gave me at least a general idea

I used this as a basis for my own ratchet mechanism .. modified a lot.
My own design. This was something like Version 5.

The chute is supposed to be cast iron so I decided to have the material printed in WSF (White Strong & Flexible) now called ‘Versatile Plastic’ (someone help me with businesses constantly changing what works just fine). This Sintered Nylon has a slightly rough surface that IMO works fine for Cast Iron in O scale.

The gate mechanism was printed in FUD (Frosted Ultra Detail) .. now called ‘Fine Detail Plastic’. The material data sheet says “Also known as Frosted Detail Plastic” .. so I intend to keep calling it FUD .. at least for a while.


Here’s the chute as printed in WS&F. You can see the slight texture .. too much for something like a cab but fine for cast iron in larger scales.


The way I designed this, the door can be either up, down or in between. I was quite happy with how well it printed in FUD. If I were to do this again I think I would step it up and have it printed in FXD – now called ‘Smoothest Detail Plastic’. FUD is printed at 29 micron layers while FXD at 16 micron. These have been hit with a light coat of Tamiya Fine Surface Primer.


I wanted to get an idea of how this would look when assembled so I rendered this in Kerkythea – a free open source program. This is much cleaner and new than it ended up with the model.


Both the WS&F and FUD type plastics need to be primed. Here I have hit the chutes with some cheap WalMart gray primer – working my way to them being rusty cast iron. You can see the texture with thi sintered nylon .. I really like the effect at least in O scale for looking like cast iron. I masked the face of the chute as that is where the chute mechanism will glue to. The holes are there for Tichy NBW – WS&F sucks at small details like bolt heads.


Honestly I don’t remember what I used to spray the brown – a brown primer perhaps .. I am pretty much willing to use any brownish-reddish color for a base coat for rusting. This was applied after the NBW were super glued in place. When dry I followed up with a light wash of vallejo rust.


I used one of my craft store acrylics such as Folk Art brown and a sponge to finish off the rusting.

For the rest of the rusting I used vallejo rust paints – light rust, rust and dark rust in that order followed by vallejo black wash applied as a pinwash.


This photo is posed for a test fitting of the gate, showing how the shafting will work. The pin will supply the shaft with the gears sliding on. The door can be positioned either down all the way as shown or in the up position – limited by that the pinyon gear has to mesh with the rack. At the top left is the vertical shaft tube. This is where the shaft from the handwheel will drop down to hold the bevel gearing.

At an extreme close-up like this you can see the layering of the print. Honestly you can’t see this with the naked eye but this was printed in FUD at 29 micron layers. If I had it printed in FXD at 16 microns it would hardly be noticed even in a macro photo like this.


The gate assembly has been primed and painted with Folk Art metallic acrylic paint (oily steel) and then everything is glued in place. I can’t leave well enough along so will be rusting up these parts too.


Not trying to beat a dead horse but the gears here were printed in FUD at 29 microns. I think they are pretty darn good ‘as is’ but again .. if printed in FXD at 16 microns would be even better. I brush painted these using a Folk Art metallic craft acrylic – I am sure that airbrushing would have been better but I will leave to others to do.


In this photo I am holding one of the bevel gears while sliding the shafting through the center. Once the shaft was through the bearing on the gate support on the far side I slid the two pinyon gears onto the rack and used some thin super glue to fix them to the shaft. This photo shows the chute with the gate mechanism in the up position.


The finished project. All in all I am quite happy with the results. Like I mentioned earlier I would probably have the gate mechanism printed at 16 microns instead of the 29 microns that I did .. but honestly you can’t see the difference except with a macro lens so that is all just me being picky.

Shapeways 3D Prints