Changing the Mendel90 sturdy horizontal X-axis to a vertical orientation, requires also another way of mounting  the direct drives extruder’s to the X-carriage, the ultimate greg’s wade’s geared extruder has both,  the vertical is firm but not particularly rigid.

Most of the weight comes from the stepper motor, located far from the attach-point and only a small force is already sufficient for movement/vibration of the nozzle in the Y-direction to the X-carriage.

Adding a third mounting point to the X-carriage improves this

With proper choice of stepper motors (weight) of direct drive and X-axis, is the center of gravity on the line between both Z-axis smooth rods with the nozzle only 20mm in front of this line

A proximity sensor can be attached to the each direct drive body in place one to the x-carriage, but all by all it requires a lot of X-axis space and with keeping open an upgrade to a larger heatbed (300x200mm) needs quick 45-50cm smooth rods, a length not preferable to down-grade the 10mm Mendel90 sturdy smooth rods to 8mm

The required X-axis length can be significantly reduced by rotating the extruder body 90 degrees (like i3 Rework , L3K) and limiting the length two LM10UU bearings (65mm).
The x-carriage of the 3in-1out has already as test, plastic variant for LM10UU (IGUS-style, next SF-1 10x12x?), which has the advantage ~ 45 grams less moving mass for the x-axis, which benefits the acceleration and faster printing.

Greg’s Wade’s geared extruder turning 90 degrees is a big modification and there are many options as also a few alternatives for hobbed bolt are included.

I selected a very limited few  from the many available feedstock gears for  5mm shaft for the first draft Left to right: “reprap mendel extruder drive gear” , MK8, MK7, T26, T38 and U604zz bearing

There is a slight preference to stay close to the effective diameter of a hobbed bolt, keeps the possibility open for all direct drive extruder having the same steps/mm, with only a customized different transmission ratio’s (1:3 – 1:5 ratio).
Indirectly it’s, also a preference for small effective diameter feedstock gears since these need lesser force and make it even easier to swap the standard NEMA17 stepper motor for a pancake or NEMA14 stepper motor, which is another 150-200 grams less mass to move during printing.

For remote Bowden drives, the weight of the stepper motor is not so important and I also looking into other types, like friction drives (Vaeder V Struder / Gunstruder)

The first draft is made with the most major modification tailored for each feedstock gear on basis of the openSCAD 7th Gen Greg’s Wade’s geared extruder sourcecode.

The first basic printing data can now be collected for dropping some feedstock gears and modifications.

STL’s (zip-files)
3-point mounting  Greg’s Wade’s  geared extruder body  (3mm)
MK7 1,75mm filament
MK7 3 mm filament
MK8 1,75mm filament
MK8 3 mm filament
T26/T38 1,75mm filament
T26/T38 3 mm filament
Used herringbone gear set
Simple 80 tooth GT2 gear for M5 hex bolt