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BadMouth:
Dunno if anyone here cares about my 3D printer tinkering, but I don't belong to any other forums to post on. :lol

Settled on this boring belt path for the Y axis. I planned to put a tensioning adjustment in the back, but there isn't room so need to rework the front. This is just a plate for testing. The final version will have the bolts holding the idlers supported on both ends. I flipped the X motors over so they are above the back crossbar instead of below it. That with this Y motor mounting puts all four X and Y motors in the same area which will eventually be isolated from the build chamber and cooled. I think the Octopus control board can fit in there as well which would make every run of wire in the machine much shorter.

I installed the new X/Y joints which pushed all the belts out 2mm. This looked like too much and the back idlers pushed the belts out way too far. So I did what I should have done the first time around and measured the distance between the belts and the linear rail at both ends. It turns out that leaving the rear idlers where they were and only pushing the front ones out 1mm would have been the correct thing to do. So another overnight print and I have X/Y joints that give the belts 1mm clearance over the blocks. The top and bottom belts are in perfect alignment with each other which gives me a warm and fuzzy feeling.

Since the belts are still pressed against the blocks where they are attached, they can still rub when both X axis blocks are near each other. So next up is to rework the x-carriage to incorporate a 1mm shim behind the belt being attached.

Howard_Casto:
I've been following along... I just don't have anything useful to comment on. The documentation of your experiments are very much appreciated.

bobbyb13:
I am merely a voyeur here because the stuff is fascinating but I still know almost nothing about it all !

BadMouth:
Progress:

The belts for each X carriage must pass through each other.
In the last installment, I moved idlers forward 1mm to provide 1mm of clearance behind them. (pic1)

The other worry is that the belts will rub the mounting screws. I verified they did not by attaching the belt to only one carriage and installing only bolts in the other so that everything was visible. (pic2)
I may have thrown in the towel or restarted from scratch if this hadn't worked out.

The next issue was to raise the secured belt 1mm off the block so it doesn't rub the other carriage when they are close. I started out with a shim, but really hated the idea of having to hold the shim, belt, and carriage all in place while installing screws. Finally came up with a different way. (pic3)

Final clearances. (pic4) Top is secured, bottom is pass-through. Other carriage will be opposite. Passthrough tolerance looks super tight, but I pushed on the belt in all directions and it moves (meaning it has room to move). Did the same test with the carriages at the ends and close to each other. An official design would probably have more clearance toward the front to account for variation in parts used. I am running with this for my build though. The parts pictured are test pieces. I will print the full carriage parts tonight.

BadMouth:
Complete dual toolheads now mounted. Waiting on Y drive parts to print, then it will be alive again. It turns out that the old induction sensor will not work with the newer Voron carriages (it touches down before the nozzle!). I had a pair of the newly specc'd ones on the way from Ali-Express, but shipping was delayed. So I ordered a knock-off from amazon along with some HIPS filament. Hopefully I will be pushing plastic next week.

The BTT EXP-MOT expansion board came in. It allows you to drive 3 more motors. It works fine with the Octopus. This means that I can run the Y motors independently and also upgrade the to the Trident Z axis.

If anyone has a need to add a few more motor drivers to a BTT board, here is what you need to know:

It connects to EXP1 & EXP2 that the screen would normally use. If you have a setup where the display connected to the mcu is required, this is not an option.
The included cables are only about an inch long. This is because the board was designed to work with SKR 1.3/1.4 and sit right up against it.
I used a set of cables that came with a display and had no issues.

All pin assignments just use the EXP1 & EXP2 pins on the Octopus. There are no separate addressable pins.
Wipe out your display pin assignments before connecting the expansion board.
It took me longer than it should have to work out the pins because I tried to translate an SKR 1.4 example to the Octopus. Something was either wrong on the example, or I transposed a couple things.
The pinout included with the expansion board documentation is from the silkscreen on the back of the board, so it is a mirror image. It is not a guide as if looking down on the board like the documentation for other BTT products.

Anyways, worked through it and pic of pin assignments is attached if anyone is looking for them on a diy arcade forum. I only tested Motor 1. Now using all of them and they are correct, but always check every pin assignments yourself. Jumpers were set for 3.3v logic & UART mode. Other jumpers next to EXP2 removed.

This expansion board is a neat thing to have on hand. I haven't gone through everything required, but with one of these someone could probably run a Voron 2.4 with a single old SKR1.3 or 1.4 that they already have on hand instead of buying an Octopus or second MCU. A Trident could definitely be run off of it.

EDIT: I also should have mentioned that I cut the sensorless homing pin off the stepper driver per Voron instructions, as there is no jumper to disable it.

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