Design of a spool and connection from the Twizy gearbox to the Pajero disconnect clutch.

Welcome and a brief look intro to my 'OffRoadHybridVan' project.

The motivation for this project is to learn something practical of the engineering technology behind electrification of a vehicle. However deciding against, for many good reasons, not to attempt a full battery-EV conversion of my camper van, considering the size, weight, cost, limited range and charging demands which such a 3500kg vehicle would demand.

This decision not to embark (at least not yet) on a fully 'green/zero-CO2' project van will likely be a disappointment for many readers. The reality is that most owners of these camper van and the van-life culture associated with them, despite our best dreams to the contrary, the cost of full EV conversion and the limitations incumbent with driving range and mobility(charging) would be a severe compromise to getting to and staying off-grid, by desire away from urbanity and decidely off-grid - by definition out of sight of any charge point. The ubiquitous availability and convenience of diesel fuel will be with us yet for some years. This is not to deny the necessity to replace it and progress the alternative technologies, but in the near term, for motorhome and camper van vehicles and EV replacement is a very expensive choice.  I set this goal for a future next project. And yes, i have looked into and made design calculations for what could be a Tesla component equipped van conversion, and for all of the aforementioned reasons and more, i do not find it yet a realistic proposal.  This whole topic for discussion can become itself a companion blog to this build.

With my esoteric/pragmatic engineering head, I thought it would be more useful and practical for an 'Adventure' van, notably one based on the enormously common and popular Ducato/Jumper/Boxer/Promaster panel van platform, to add an electric assistance drive to the rear axle of this Front-Wheel-Drive van.

(update - April 2021 - in retrospect, and just to correct any misinterpretation of the reason for this rear axle project, after some further research i have the view that the most sensible, cost effective way to extend the pseudo-'off-road'/off-street traction performance of a Ducato platform van, would be equip it with a limited slip differential(LSD) on teh conventional front driven wheels. This option i had formerly discounted, thinking that the benefits in traction would be at rather small and potentially at odds with the requirements of the front steering. I will write more about this in detail in another post. However, worth to note in this moment, is that no such LSD is available off-the shelf for the M40 gearbox in my 3.0litre F1C engine Jumper.  So my rear axle project continues as an interesting journey of learning-by-doing.)

This idea arose quite unplanned following brief ownership of a conventional mechanical '4x4' van, a Dangel Ducato 4x4. That van was an ex-postal delivery van equipped with the Dangel viscous coupled rear drive axle, a common low budget type of so-say '4x4'.  Following an immediate problem of oil weeping from the rear gearbox, i found an overwhelming dislike of the whole inefficient concept of permanently connected and 99%-of-time useless mechanical drive. With some knowledge of the soon expected 48v electrification path for hybrid cars, i thought why not try to build myself an add-on 48v based drive system. It can be a part-time/only for off-highway 4x4 use which is anyhow the mode of operation familiar to old-school part-time-4WD vehicle. It is worth to mention that my other 'car' companion in many outdoor weekend trips has been a 1988 vintage '61 series Landcruiser, equipped with part-time locking front wheel hubs.

In auto-industry terms it would be classified a so called 'P4' /thru-the-road Hybrid, where the electric drive is added independent of any mechanical connection with the native combustion engine(ICE).

Hence this approach is a well suited to addition on the rear axle of a FWD vehicle, especially because it provides an effective '4WD' function.

 An important target in the design has been to adhere with a low voltage(nominal 48v) system for reasons of safety concerns and for reduced cost and to be within the capacity of recharging off-grid using conventional motorhome solar. A key motivation from the beginning has been that the drive system can be a realistic retrofit addition in complement to installation of an upgraded on-board battery system. Specifically a 4 x 12v Lithium-Iron-Phosphate battery pack is becoming already a safe and accepted installation in a live on-board camper van. I expect many car EV conversion enthusiast may argue the point, but i think it not something safe to be installing salvaged re-purposed Lithium-ion-NMC ev battery in a vehicle which can be expected to be sitting dormant, unused and cold for many days or weeks in between adventures. Admittedly LFP battery also require some thermal management but they are by comparison much more robust and safe. Again, with the pace of electrification technology these concerns may become alleviated but only then also accompanied by a change in use/expectation that the vehicle must remain itself powered-on albeit in a sleep either connected to a grid supply or with sufficient on-board energy or autonomous energy supply to avoid degradation of the battery cells.

Another desire has been to keep the design reasonably within a retrofit possibility. Unfortunately it has not been entirely possible to avoid encroaching thru the vehicle floor, this was necessary to maintain an acceptable ground clearance constrained by the depth of gearbox below the floor integral with the motor. Nonetheless, the hole is small and avoids any cutting of the main structural cross beam in the floor. The protrusion height is within 50mm thickness of the intended floor insulation and covering, so it will not be seen.

The original Ducato van rear leaf spring suspension and brakes are retained. The cross beam 'dead' axle has been replaced with one salvaged from a Dangel 4x4 Ducato which of course fits directly the original vehicle chassis and suspension but provides additional space for clearance of the added differential.

The differential i chose to use is salvaged from a 2003 year Mitsubishi Pajero(Shogun) 3.2DiD, with factory/oem locker. This is a monstrously heavy(53kg) lump of old-school heavy duty 4WD transmission. I believe these are quite sought after in the offroad community as retrofit on custom vehicles.

Anyhow, i figured it was the most suitable robust lump of differential i could find which provided me the independent mounting and lockable function.

The driveshafts i custom fabricated from each of original Pajero on teh diff side and Dangel driveshafts on the wheelside.

The critical feature to understand is the Dangel axle provides the needed wheel hubs which are driven not just freewheel hubs.

Ideally, i would like to have these hubs themselves capable of being disengaged(made freewheel) or driven, in the same fashion as was many old-school 4WD vehicles such as Toyota Landcruiser and Nissan Patrol of the 1980's-1990s'. For this idea i have a design in mind which itself would involve a custom beam axle which provides some increased ground clearance.