Saturday, March 02, 2013
Rob Hackstetter talks about the AWD Invex998
While 2WD/AWD off-road bikes already exist, what really fascinates us is the possible application of AWD technology on high-performance streetbikes. Litre-class superbikes – machines like the BMW S1000RR, Aprilia RSV4 Factory APRC, Suzuki GSX-R1000, Ducati 1199S Panigale and Kawasaki ZX-10R Ninja – are what we love best and the prospect of AWD on such bikes is, for us, very exciting. Unfortunately, it seems that mainstream motorcycle manufacturers want to have nothing to do with AWD development for superbikes. But that hasn’t stopped individuals from trying to build their own AWD superbike. One such machine is Rob Hackstetter’s AWD bike – the Hackstetter Invex998 – which features AWD. We caught up with Rob for a quick chat about his machine. Here are some excerpts from what he had to say to us:
On when and how he got started with the idea of building an AWD motorcycle
In June 2005, one of the tenants in the industrial park I leased an office in, asked if he could keep his motorcycle in my office. Apparently he was hiding it from his father, who was also his boss. I’d start my mornings with a cup of coffee, staring at a motorcycle against the wall of my office. It was at this moment that the idea of a more advanced two-wheel-drive motorcycle came to mind.
I chose a superbike for proof of concept and packaging, the idea being that if you can fit all the running gear for 2x2 in a superbike, it should be easy to integrate the design into a touring bike or cruiser or off-road motorcycle, where spatial constraints are more forgiving.
On his first AWD prototype machine
The first prototype, the Invex998 that you see here, is completely handmade. The name Hackstetter Invex998 is derived from the Hackstetter 2x2 gears housed in the transmission and the 998cc engine. I built ninety-percent of the bike from scratch. The only preexisting component is the engine, which had to be reworked to fit my design. The Invex998 was originally supposed to utilize a preexisting frame but I made the decision to move away from a premade frame when I realized that the modifications needed to the frame would most likely take more time and material than it would to construct a new one.
After careful consideration, I chose to fabricate a trellis frame out of Chrome-moly-steel; the type of frame that Ducati is famous for. I chose this design over the twin-spar aluminum frame because with the latter, it would have taken much longer to configure the bike’s suspension set-up. (More on that here)
On the advantages of AWD on streetbikes
The major advantage of having all-wheel-drive on a motorcycle is superior traction, as data logged laps aboard my bike, at the Pocono raceway, attests to. I don’t think a motorcycle should have a switchable traction source like some 2WD systems use for rider safety alone. The biggest design mistake I’ve seen, which is clear on the Suzuki Nuda concept and some others, is driving the front wheel from one side, which causes torque steer. Another issue I see, which seems to be promoted by misinformed magazine editors, is that that you can’t just chain the front wheel to the same sprocket output shaft of the motorcycles engine that’s also driving the rear wheel without any ‘differentiation.’ This is the fatal design mistake I see in every design. The best approach I’ve seen in the past was the Nuda – they address differentiation with a viscous coupler, which, however, is too slow.
On reactive vs proactive AWD designs
Reactive designs are not seamless, especially for the rider. In my opinion, this is the sole reason why these designs have not evolved past low production dirt bikes/ kits and prototypes, in some cases a one-off motorcycle. The Hackstetter AWD is proactive, not reactive, and this is why it should have a future in motorcycles. We incorporate a torque-sensing transmission that allows engine torque to be automatically directed to the front and rear all the time, in a tenth of a millisecond, it’s always happening; it’s not waiting for an event.
Under 'normal' conditions, where traction at both the front and rear is equal, torque is split between front and rear with a 'default’ 50:50 distribution. In adverse conditions, where there is variation in traction between front and rear, a maximum of 67-80% of the engine's torque can be directed to the front or rear . The fully automated mechanical nature of the Hackstetter Transmission helps prevent wheel slippage from occurring by diverting torque instantly, without any discernible disturbance to the rider, to the wheel which has more traction. This method of operation can be described as ‘proactive.’ (More technically-oriented readers can go here to understand more about how the AWD system works)
On the Hackstetter AWD system’s electronics
The Hackstetter AWD is electronically controlled, but not in the classic sense, which might come as a shock to some readers. Let’s just pretend we decided to use a Haldex clutch drive system. Well, once again, they are reactive – since they only redirect torque after wheel slippage has occurred. The Hackstetter all-wheel-drive utilizes a rider information microprocessor and accelerometer to make adjustments to the default 50:50 torque split, which also takes into account the bike’s weight distribution. This takes into account vehicle loading (if you have a rear-seat passenger on board, for example..) and optimizes stability, acceleration and traction. Torque transfer between the bike’s wheels remains seamless under both hard acceleration and hard braking.
On the future of Hackstetter’s AWD system
I can’t elaborate on the manufactures that have contacted me, but I can tell you that the Hackstetter all-wheel-drive technology may show up on a streetbike under license by Hackstetter or under a new trade name if we decide to sell off the technology exclusively.
Well, the Hackstetter AWD bike shows that it can be done – it is possible to build a 2WD superbike and while the results would need to be validated by professional test riders, it would seem that the benefits of added traction could possibly take performance to a whole new level. We can only hope that in the future, some mainstream manufacturer will take more interest in 2WD/AWD technology for motorcycles, which just might lead to a production-spec AWD machine…