Did you ever wonder what Norman Hossack would have done if he had designed a front wheel drive system on a motorcycle using his suspension? Well, some years back, he had been working out the plans for doing just that, he even calculated the additional weight involved, but couldn’t find a suitable CV joint to meet his needs. His dream was to build an AWD Dakar bike because he thought it would be unbeatable.
Norman was reading our article on the Lawson AWD KTM with a Hossack front suspension and thought we might like to see the plans he had drawn up years ago as another take on what could be done. The drawings here are actually the ones he was going to submit for a patent, but he wasn’t ready to spend the time and money so never went ahead with it.
There are a lot of similarities to what the Lawsons designed, but handlebar placement is obviously different as well as the design around the CV joint, the Hossack style suspension seems well suited to mounting the necessary extra hardware and can be adapted in more than one way. Maybe someone should try their hand at building another one with Norman’s own design.
You might remember the Hossack square piston engine Norman shared with us a little while back. I guess once you get the creative design spark, it just never quits. I love seeing these designs, I thought some of you would, too.
I’ve included the description and more images Norman was going to submit with the front drive patent below:
FRONT WHEEL DRIVE MOTORCYLE SUSPENSION SYSTEM.
ASTRACT
In a motorcycle front wheel suspension system the front wheel is mounted by a support axle to an upright unit which slopes to the rear and is in turn mounted to the vehicle chassis via two wishbones (A arms). The attachment between the up right and these two wish bones is accomplished with ‘ball joints’ which allow for the suspension to turn to the left and right as well as ride over undulations in the road. Also mounted to this upright is an axle shaft which supports a constant velocity joint and a chain drive sprocket. This sprocket drives a chain which transferees drive to the front wheel via its own sprocket. Drive is transferred to the outer element of the constant velocity joint via a chain drive from the engine of the motorcycle via a series of guide pulleys. As the wishbones are pivotally attached to the vehicle chassis the arc they provide creates a constant distance between the chassis and the upright. Therefore the drive is transferred to the upright along a path that is substantially in line with and between the two ball joints and positioned in such a way as to keep the chain tension constant. The final chain which transfers drive to the wheel can also be tensioned and the tension maintained because the components are all part of the same housing.
TECHNICAL FIELD
This invention applies primarily to motorcycle front systems though is not confined solely to them and may apply to other vehicle forms that would benefit from a driven front wheel.
TECHNICAL PROBLEM
The normal method by which the front wheel is mounted to a motorcycle is through a sliding telescoping structure commonly known as telescopic forks. In this structure the turning function of steering the vehicle is achieved via a steering head and the bump function is accomplished by this telescoping component. The steering head usually requires large bearing assemblies rigidly mounted to the chassis and a sub assembly to which the telescoping tubes are rigidly mounted. Both of these structures make it very difficult to pass drive of a mechanical form to the front wheel. At the steering head this drive would have to cope with the left/right turn and then this drive would have to pass to the front wheel which would be at a varying distance depending on the ride condition.
In a motorcycle front wheel suspension system the front wheel is mounted by a support axle to an upright unit which slopes to the rear and is in turn mounted to the vehicle chassis via two support structures here knows as wishbones. These wish bones are joined to the upright structure via ball type joints or universal type joints
Link: Hossack Design
Kenny says
Interesting.
Hossack seems to go for a much more symetrical design, while the Lawson’s appear to use an asymmetrical design with the girder and final drive offseting the mass of the double wishbone and (supply?) drive.
BoxerFanatic says
Hossack can be asymmetrical, or symmetrical. Either way, as long as it is double-wishbone, with the wishbones not being steered, while just the upright is steered, it is a Hossack type. A Girder front end includes the wishbones in the steered assembly.
Hossack did a prototype army project that had a single-sided upright, that allowed quick mounting of the front wheel rim, or even innertube replacement without removal, and the upright had an integrated airtight chamber that could be charged with compressed air to re-inflate the repaired tire.
http://www.hossack-design.co.uk/php/page.php?p=3
http://www.hossack-design.co.uk/php/page.php?img=17
Thure says
When do you think we will see this on BMW’s K1300s/r. Wonder if the CV joint could do double duty as balljoint as well? and save some weight.
GenWaylaid says
Not a bad idea. That also solves the problem of keeping that front cog pointed straight relative to the frame without adding more pieces. The front drive chain’s horizontal plane of symmetry and the lower control arm would have to be coincident. That would put them at a position somewhere between where they’re depicted in the patent but as low as possible to maintain a decent suspension geometry.
BoxerFanatic says
The ball joint is a weight-bearing spherical joint that allows gimbal and rotational movement of the wheel and suspension upright (suspension compression and rebound, as well as steering left and right) while transferring the weight of the bike and rider into the suspension upright, wheel and tire, to the ground.
It is oriented with a near vertical axis.
The drive joint is a torque transferring device that turns the torque input 90-degrees, plus or minus the steering angle allowance, with the torque output axis being roughly horizontal at 90-degrees, with the steering arc on a plane perpendicular to the steering axis line defined by the wheel hub and suspension upper and lower ball joints.
The torque transfer joint has to be centered on that steering axis line, but it has a wholly different job to do than the suspension load bearing ball joints, and cannot handle the suspension compression and rebound angles without diminishing it’s rotational torque behavior. The input (driven chain, belt, or shaft) has to be designed to accommodate the suspension’s up and down movement.
Plus, the torque mechanicals likely need to be mounted above the bottom ball joint location, and likely also below the upper ball joint location, in order to clear control arm and upright bracing structural geometry, and provide operational component clearances.
Marty Lawson says
A CV could do double duty as a ball joint, but it wouldn’t be a very good ball joint or CV. A simple U-joint would work much better as both a suspension pivot and drive component. Several of my rejected AWD designs ideas used the drive U-joint to transmit suspension loads. In the end, I judged those designs to be heavier and more risky.
Paulinator says
The classic rear IRS design from Jaguar used each axle as a loaded component that double-dutied as one of the required four-bar links, thus saving weight, part-count and complexity. U-joints used in “phased” pairs, when input and output shafts remain parrellel, result in constant rotational speeds…or constant velocity. The Jag IRS met that requirement. U-joints could handle the load, whereas I believe CV joints would pull apart (or probably blow apart) when subjected to axial loading. By nature of the CV joint’s design, they are obviously very good at transmitting smooth torque and (I would venture to guess) very good at bearing radial loads. CV joints are also VERY HEAVY when compared to U joints for given torque ratings.
Paulinator says
Hey Marty, I just realized who you were 🙂 I think your build is awesome stuff. I once converted a mountain bike to tap handle-bar power to the crank-set (pedals). I used a torque tube, a kind of swash plate mounted to the left crank arm, some rod-end bearings and a hand built transmission that was basically a set of dog-clutches. The transmission enabled me to lock the handle bar rigid for normal riding or engage the oscillating torque tube for hill climbing. I found that the effect on steering and control wasn’t so bad. The bike’s handling actually improved on loose gravel when the torque from the handle bar was transmitted to the rear wheel.
I did a lot of off-roading in VW based buggies. I formed the opinion years ago that cable drive would be the lightest and simplest means of transmitting intermittent power to the other corners. I’m just talking though…never did it.
Andreas Aronsson says
When I read up on Hossack’s troubles with getting his design recognized I was all passively raging over how outdated simple telescopic forks are, and a bit fascinated that BMW actually waited 25 years before using the design just because of the patent… I would love a bike with the Hossack suspension, but I cannot afford a BMW… so meh 😛
I was fascinated by the two wheel drive KTM bike, very interesting design, and seems functional. This design is probably a bit easier to wield, but I do wonder where the shock absorber goes! 😛 And as for all TWD-designs I’ve seen, the amount of chains makes me wonder just how much maintenance it will require, haha.
Also, is it only useful offroad? Would you need some kind of differential when turning on tarmac? Hmm!
Marty Lawson says
Since motorcycles rarely travel backwards, a simple ratchet to let the front wheel spin faster than the rear works well.
I think AWD/TWD does have merit on road as well as off. Assuming a close geared full power drive like mine or Hossack’s is used. AWD gives combined front and rear breaking, eliminates a lot of front washout scenarios, and makes the bike docile and easy to control under power. (you can still steer just fine with the front wheel spinning)
BoxerFanatic says
I have yet to ride a Hossack bike, or Duolever BMW, but I hope to.
If I had all the skills and/or money to build or commission a bike, I would build a BMW 1200 hex-head boxer, or maybe one of the new water-cooled boxer, with a hossack front end, and a shorter wheelbase than a K12 or K16.
I have read through anything on the internet I have come across about the Hossack suspension, and in theory, I am a fan of it. I have read criticism that the K1200 bikes had lack of front end feel, and some attribute it to lack of suspension ‘noise’. I wonder if another iteration or two of design and geometry refinement might get it dialed in even better.
As for the front drive, I like and prefer AWD cars for year-round use. I am not sure that a street role for an AWD bike on the street, in the slick is justifiable.. and I wonder about the forces of a steered front wheel applying power, at a different vector than the rear wheel, and perhaps a different speed. The gearing ratio would have to be precise to account for tire diameter differences, as well as geometry changes in the suspension. If a viscous coupling, or other slip-allowance device were introduce, it would somewhat mitigate the point of adding so much complexity.
For a steerable power transfer, I wonder if an axis-tilting crown wheel gear would work. The crown wheel is essentially a shaft drive ring gear, oriented horizontally, between the suspension upright braces, centered on the steering axis. The power input pinion would come in from the main body/frame of the bike, and drive the crown wheel gear. The crown wheel gear would in turn drive a second output, trough the suspension upright brace, driving a belt cog wheel or chain sprocket down to the wheel hub, as the illustration shows.
1: The problems foreseen… more precision machining than a hossack suspension upright typically requires, for the crown wheel drive assembly to pivot on the output pinion axis.
2: The input pinion shaft would likely need to be double jointed, universal or CV joints, to not over-stress the crown drive unit in the suspension.
3: unsprung weight. more parts count on the suspension at the unsprung end of the control arms.
4: Torque-steer. Torque being applied to the crown wheel gear would tend to try to rotate the whole assembly, rather than just the crown wheel gear. It would be exacerbated when the front wheel traction is stuck stationary, which would lock the output pinion and the crown wheel gear while the pinion tries to turn it under driveline power. It would try to wrench the whole suspension the same direction as the crown wheel rotation.
Some or all of these issues might apply no matter what method is used to turn the torque output path, with any sort of joint, or geared mechanical device.
For off-road soft or loose surface, I can see why it might aid to keep the front wheel from plowing, pushing, or getting too badly mired.
But in reality, it might end up being quite complex to engineer, and handle once built.
I think I would stick with just having the Hossack front suspension, and leave the unsteered rear wheel to apply torque.
dave says
Interesting. Still too many moving parts. Yamaha did it better.
Marty Lawson says
Huh. Using the chain to guide and control a sprocket mounted to the outside of a CV is technically risky, though likely to work. (bet it would be rather sensitive to alignment) Trying the same trick with a U-joint is likely to fail due to reaction forces generated by a u-joint’s “knuckling”. If the CV/sprocket does work, un-sprung weight is likely to be around 10% less than my suspension because of the simpler front fork structure.
Probably could convert an existing motorcycle if Hossack borrowed the steering link and low-rake zero offset steering geometry from my bikes.
Rob says
Ok I’ll go outside the square.
Electric hub drive or internal combustion hub drive eg. mini turbine in hub?
Benefits of AWD vs RWD? If we can do it with out messing up the ride, then it could be useful. An on/off switch would be nice and having the drive in the hub might mean simply switching front wheels (after disconnecting petrol or electric lead) to go from AWD to RWD.
Hooligan says
Electric hub? Exactly my thoughts, none of those flailing chains. And much easier to control and regulate.
sfan says
I agree with several comments above, I think chain based 2wd has too many inherent drawbacks. The Ohlin’s (Yamaha’s) hydraulic system or electric hub is the way to go.
Paul Crowe says
As newer technology appears, what would have been perfectly functional in the past, now seems like the less elegant solution. It’s more obvious on cars right now with so many “by wire” systems being added, engineers are constantly getting rid of direct mechanical connections everywhere which creates a lot more freedom in design.
Motorcycles are behind in this regard and the tech for an electric motor in the front wheel isn’t really optimal yet, so chains still work pretty well, but you can probably assume, anyone seriously looking to develop an AWD solution in the future is more likely to consider something other than chains, or cables or hydraulics for that matter.
joe says
Hydraulic drive is the simplest way to go. It’s been tried and tested. Cv joints and universal joints transmit torque reaction through the steering. Flailing chains and spinning sprockets close to the rider are downright dangerous.
Rob says
Hydraulic drive sounds ideal really.
Though if we can produce something between this
http://www.youtube.com/watch?v=PFnZJeHc-KY
and this
http://www.wired.com/science/discoveries/news/2001/11/48400?currentPage=all
Then a hub drive with a simple ratchet system might work, or a small motor mounted Solex style above the front wheel.
JimP says
I have read the comments related to this article and tend to agree with those that suggest an electrical solution. A drive system comprised of a motor/generator and hub motors would seem to be an obvious solution. The extra weight of the generator, electric hub motors, controllers, and wires would be offset by the elimination of the gearbox, chains/drive shaft, CV joints, additional pulleys, etc., etc., that would be required for a mechanical drive system. The weight tradeoff may not be equal but any additional weight due to an electric drive system would be seem to be a small price to pay for all wheel drive. And conversion to rear wheel drive (or front if desired) only would require a simple on/off switch. I believe the technology is presently available for a prototype.
norman says
I am surprised nobody has spotted the real reason that the wishbone system is better than tellies for FWD. With a near vertical wheel path there would be no generated lift. In the same way that tellies generate dive under braking, a driven front wheel with tellies would generate lift under acceleration. I would say that is the opposite of what is needed as it would transfer weight to the rear.
Norman