Design of a spool and connection from the Twizy gearbox to the Pajero disconnect clutch.
Hello, and a long overdue update.
One of the key difficulties with this project is the necessity of a disconnect clutch between the electric motor and final drive. Ideally this should be as close to the wheel hubs as possible. In the absence yet of designing a whole new custom free-wheeling hubs beam axle, i decided on a solution with using a dog-clutch disconnect mounted immediately after the reduction gearbox and upstream of the Pajero differential.
The hardware i found suitable is the freewheel disconnect part from the front axle of a Pajero-io 4WD SUV. This was suitable because the clutched axle part is a separate module from the front diff body. A similar design exists in the larger Pajero gen.3 model front axle, but on that one the clutch assembly part is integral with the axle differential body, so the clutch can not be removed by itself.
So the design problem has contained three elements, 1/ how to connect the output from the Twizy/Comex gearbox to this Pajero clutch shaft, 2/ eliminate the open differential design of the Comex, and 3/ upgrade the torque capacity over the little skinny original 20mm output side shafts of the Twizy.
It has been really a tough design problem, where i considered many alternative designs. The difficulty was how to deal with or avoid any mis-alignment of the connected clutch shaft with the gearbox output shaft. A standard approach would be to employ some type of CV joint tolerant of some misalignment, but this would be a big work to achieve in the short physical space available.
Finally, the breakthrough came with a design actually very similar to how the Pajero clutch is mounted in it's own native differential, where the the shaft inserts itself into one of the side gears within the diff carrier. I realised that i could do the same approach within my new custom designed spool using one of the original Pajero differential female splined side gears to grab the end of the inserted splined clutch shaft. Among the advantages is to avoid any modification of the Pajero clutch shaft or it's housing, providing a best alignment and a strongest coupling, eliminating completely the small 20mm dia. original Twizy side shafts. For machining there is no complexity with needed to cut any custom splines, because the splined joint is made using the original native Pajero partner components, i.e. clutch shaft and it's side gear.
I have documented the activity in two parts, first to describe the design problem, and secondly the solution design.
It has been a big work learning to use FreeCAD to make the design. I am thoroughly impressed with the FreeCAD software, it is a great tool for design.
