1) File off any burrs before fixing the gear box. The planes on which the box will be mounted
must be absolutely even and orthognal to the axle(s).
Minimal corrections can also be done by putting under a piece of paper or plastic before screwing all together.
The gear behaviour is very sensitive to distance and angle difference offset.
When compiling the OpenSCAD file the distancies are printed in the console window.
The gear pair is mounted correctly, when the noise reaches a minimum.
2) Instead of set screws bore a 1mm hole through the prepared holes and the axles,
insert a 1mm wire and bend them by 90°.
3) Do step 2 also for the already existing wheels of your models. By this you get a little
mechanical clearance at the wheels.
Because most models have no differential gear, you get a better behaviour in narrow curves.
4) Since version 3.1 you can select expicitely horizontal mounting. In this case the fixing wings are
always printed. The wings have a fixed size which is calculated from the mechanical parameters
defined in the *.scad file. The wings are printed on both sides of the box, so you can mount the
box in front or behind the motor. Four holes for the screws are printed in both wings (diameter 1mm). You have to bore up the holes for your needs. On the non-to-fix-side you have to bore up the holes to a size, that your screw driver can pass them.
When pulling more than two Playmobil or LGB coaches, the gear wheels may skip by one or two tooths,
because the motor (and its box) is fixed only one side (and at the opposite side of the gears).
Advantage: Motor will not block if overstressed.
You can avoid this behaviour by pushing together the gear wheels a liitle bit. Yet if you
push them together too much the motor may be blocked and / or noise increases. This may also damage the tooths.
For the Stephenson locomotive I decided (for me) to cut 1,8mm of the axle carrier. Marked in red
Otherwise I had to choose another transmission ratio or choose manually another circular pitch.
Example for the console output of OpenSCAD if the box will not fit:
ECHO: "Circular Pitch:", 159.545
ECHO: "Axle No of Teeths:", 20, "Pitch Radius:", 8.86364, "Root Radius:", 7.77727, "Outer Radius:", 9.75
ECHO: "Motor No of Teeths", 10, "Pitch Radius:", 4.43182, "Root Radius:", 3.34545, " Outer Radius:", 5.31818
ECHO: "Distance between gears axles:", 13.2955
ECHO: "Free space left to the AxleFirstFreeMountingPosition:", -1.70455
ECHO: "Note: Minimum distance must be: ", 15
ECHO: "Increase number of teeths for the motor or decrease (mechanical) AxleFirstFreeMountingPosition"
ECHO: "Gear box dimensions (Length x Width x Height:", 18, 16, 30.4455
Most of the parameters for the gear and the gear box can be selected in the .scad file.
For users without OpenScad experience open the file with a text editor.
The .scad file is decorated with a lot of comments about the different parameters
and contains also tips about the 'what and how to do'.
Different parameters like available physical dimensions, free space available, transmission ratio
and much more is selectable.
Enhancements to Version 2
1) Selectable fixing plate. Enhances stability and needs no modifications of the model.
2) Introducing a backlash value. Reduces abrasion and noise
3) The gear pair and the gear box are calculated from the parameters.
4) Messages are output for the radii of the gears and the size of the gear box.
A warning is output if the gear box will not match without modifying the model.
5) In Version 3.1 you can select horizontal mounting explicitly.
Outlook to the future: I will split the parts with the physical dimensions of the model to a
separate file, which will be included at compile time.
But now i will really concentrate the work on the current pickups....