(first posted 9/3/2013) Californian Charlie Fehn first had the idea to design and build a two-wheel drive motorcycle in the late fifties, and was eventually granted a patent in 1963. It’s been a long and rocky road for his “Trail Breaker”; the number of legal entities and plants that have built his invention is long, but it’s still being made today, and it hasn’t changed fundamentally during all that time. Sometimes a good idea just won’t quit, no matter what the obstacles.
Here’s Charlie Fehn with the the first complete demo “Trailmaker” (later re-named “Trail Breaker”) on the dunes in 1959.
And here’s the patent from 1963. The one I stumbled into as it was being serviced on the owner’s driveway is a 1972.
And now we have the current Trail Breaker. Yes, it’s evolved a bit, but it still has the same basic frame and drive system, even if it has acquired a four-stroke engine, smaller wheels and a front suspension.
There are just things that only a Rokon can do, or at least do best, like being floated across a river thanks to its giant hollow aluminum wheels. Or if they’re filled up with fuel, be able to traverse hundreds of miles of wilderness without worrying where the next gas station is going to be.
Let’s take a look at what makes this mountain goat so effective. Well, those big 15″ tires borrowed from a small tractor is a good place. The air valve is on the left; about 5 psi is best. And the cap to convert them to a reserve fuel tank is on the right. Realistically, there are some downsides to using them as fuel tanks, like a negative affect on the bike’s handling. And I assume you need to have an air pump along too.
But let’s jump to what turns them both, starting with the engine. A number of two-strokes were used in the very first few years, but it soon settled down to a 134 cc West Bend mill. These are descendents of the first popular air-cooled outboard motors built by West Bend for Elgin and Sears. It evolved to become a the first really successful go-cart engine in the fifties, as well as other applications. Chrysler Marine took over West Bend in 1965, so this is technically a Chrysler engine. In the eighties, Brunswick took Chrysler’s marine division off their hands, and today its descendent is still being built by U.S.Motor Power in Wisconsin.
But recent Rokons have switched to both Honda and Kohler four strokes, which has pros and cons. The four strokes meet CA emission regs and have excellent torque, but climbing up radically steep angles has caused oil starvation in some owners’ bikes. That obviously can’t happen with the two-stroke.
A centrifugal clutch takes up the power and sends it to the input shaft of the transmission via that blue belt. That’s the hand-shifter for the transmission, like an old Harley.
That transmission caught my eye, with that name “Albion” on the case. Sound rather British, eh? Well so it is, a venerable three-speed motorcycle unit dating back to the twenties, no less. It’s withstood the test of time, although more recent Rokons use a Salisbury torque convertor, similar to the ones used in snowmobiles.
The output from the Albion is taken up to a jack-shaft via chain, that also has the 90 degree take-off for the front wheel. I should have taken the seat off and gotten a better shot of it, but the there’s a central shaft that runs forward through the frame tube.
But I did shoot a close-up, so here it is. Sorry, but I’m a bit of a fanatic about shooting and showing these kind of things. And I’m always amazed at how difficult it is to find good detailed shots of lots of details of cars’ undersides and insides and such. Someone fifty years from now will thank me…hopefully.
Actually, Tony, the Rokon’s owner, did take the seat off, to show me its Italian origins as a scooter seat for Vespas or Lambrettas.
You’re looking at where the power shaft meets the front fork assembly. That includes both a CV joint as well as an over-ride clutch, a critical component. When a bike is in a turn, the front wheel traces a larger arc than the rear wheel, so it has to be able to roll a bit faster. The over-ride clutch allows just that. The current Rokon even has a clutch that automatically disengages the front wheel drive at full handlebar lock, allowing the rear wheel to spin out a bit at will, which can be helpful in positioning a bike in certain situations.
This is the front end of that power shaft, and here it makes another 90 degree turn, for the chain drive to the front wheel. On the other side of that shaft is the only brake on this Rokon, a mechanically actuated disc brake. Rokon was the first bike to use a disc brake, but at first glance it might seem odd to see it here on the front wheel. But since the wheels are always coupled, it brakes both wheels equally. It looks a bit feeble, but Tony said it does the job.
It’s not like it has to brake the Trail Blazer from blazing speeds. Top speed is about 25 mph, although newer ones can go somewhat faster. First gear is as slow as it needs to be, including climbing over giant logs, up the side of the Empire State Building, and other obstacles.
Instead of talking about the Trail Breaker’s capabilities, let’s see them in action. But not a current video, rather one from the sixties, as is befitting of this living dinosaur.
Now I haven’t really covered the Trail Breaker’s long and convoluted ownership and manufacturing history. It’s pretty messy, and maybe a bit tedious. Here’s the best detailed history of the Rokon out there. And let’s just say that Rokons are being built today in a small family-owned facility in New Hampshire. And it wouldn’t surprise me if they still are fifty years from now. Some ideas are hard to improve on.
6/23/2018 postscript: of course now it’s super easy to build a two wheel drive electric bike with two cheap-off-the-shelf hub motors, so I doubt the Rokon has much of a future.