Why design the core monorail hardware this way?
This is hard to answer without a degree of speculation, but I assume that the core reason behind the decision to design the monorail this way likely came down to cost and engineering challenges. TLG wanted to allow for a monorail train to be able to navigate inclines effectively. This required:
A cog system
I'm not aware of any sites that are dedicated to DUPLO train layouts, but there are certainly interesting layout ideas out there. For example, this was included in set 2932:
There are also loads of great creations in this Pinterest category:
Not really an answer, just a small point of fact..... There were actually 4 Monorail Trains planned, a Futuron Space-Themed one, a Unitron Space-Themed one, the ever pleasant Airport Shuttle Town-Themed one, (good for cities, even by today's standards, as building a large scale Monorail using brick-build tracks and Power Functions is a little too labor ...
I have found the linked .doc file by using the Wayback Machine, consider making a donation to their awesome service if this has saved you time and/or money :)
But in order to reduce load on their servers and provide a backup, I have reproduced the contents of the document below:
Anatomy of a Monorail Switch
This document describes the features ...
Maybe the plastic is worn off just enough that the switch is not pushing the pins completely anymore.
Debug step 1:
When the train pins are in the switch zone there shouldn't be a lot of space between the point of the pins and the face of the switch. If it looks too loose that could be the problem. A way to test this would be to put some clear scotch ...
There's an article about this topic in the November 2018 issue of HispaBrick magazine.
In addition to a nice interview with the designer (Masao Hidaka), the article shows off some of the techniques used for building the rails:
Technically, the design matches most of your specifications.
It even includes a rather complex motorized switch:
Here's a ...
Try to keep the track in mint condition. For example, don't expose it to extreme heat or cold. Keep it away from any pets or children who don't know better. Looking at some pictures, it seems that the vehicle on the monorail runs on a gear. Try interchanging gears every so often so that the gears don't wear and the teeth don't get bent or break.
First question; yes. as long as they are your CAD models you can do that , for example on Brickshelf
Second question: In LDraw , A CAD program for Lego they have monorail parts, here
this may also be usefull
Monorail Network Planner Tool
There were more than 5 monorails planned actually. The fifth one was a Wild West themed one. It used the same track but had a different motor. I’m surprised that it gets overlooked since an image was released of it for brick-journal
The track is pretty durable. I have several pieces of old track that the motor runs on well.
With the 3D printers now available I am hoping to be able to "print" some of the track with ABS filament. Getting the gear teeth just right will be the tricky part and the end connectors.