Lawson all wheel drive conversion with Hossack style double A-arm front suspension for a KTM 300 EXC
Today's dirt bikes are pretty capable machines, light weight with long travel suspension and able to traverse rugged terrain with ease, but there are times additional drive from the front wheel would be an advantage. Marty Lawson and his dad decided to design a front drive system for a KTM 300 EXC and what you see here is their third prototype and it looks like they've got it working pretty well.
Lawson all wheel drive conversion for a KTM 300 EXC
The new Hossack style double A-arm front suspension brings anti dive and anti rise capabilities by itself, but with the addition of a front sprocket, a single universal joint and two chains, they're now powering the front wheel with a surprisingly simple system. It adds just 28 pounds, however, their aim is a production unit with a target weight of just 13 pounds. That's a minor weight penalty for a potentially major traction advantage.
Close up detail of AWD conversion
It is easier for an average rider to control on steep bumpy slopes, to surmount rocks and logs, and to maneuver in sand, mud, and snow. As both wheels are pulling to surmount obstacles, the Lawson design motorcycle does not require speed and aggressive spinning of the rear wheel. As a result it is much greener, doing less damage to the terrain, and it can be much more easily walked through narrow backcountry trails such as those used by firefighters or rescue personnel.
An overrun ratchet in the front wheel allows it to spin faster than the rear wheel in turns and adjustable gearing allows as little as 1 percent rear wheel slip before the front wheel engages, which means essentially full time AWD.
Drive chains for the front wheel
This looks like a very well engineered system, though actual comparison tests will help anyone decide how well it works. The video below shows the bike in action compared to a standard 1WD.
Nice job, Marty!
Link: New Tech Development
Video below:
{ 35 comments… read them below or add one }
wow, impressive. I would be interested to see if the front drive system imparts any torsional loading to the front suspension on its way through the parallelogram linkage. It looks as though it may try to lift the front wheel under power (compress the suspension) – at the same time the rear wheel is trying to lift the rest of the bike. Plus, a U-joint isn’t the smoothest way to apply power. In other words, I see no shortage of fun, interesting challenges to be solved on a system like this. I’d love to give it a shot too.
Simply awesome.
-todd
I built a handle-bar drive attachment for my mountain bike because I was sucking wind trying to pull my two kids up hills in their trailer (they were small once). I used an off-set linkage that resembled a U-joint, to transmit power from the A-head to the torque-tube drive system. It was not CV but there were no ill-effects with steering inputs as great as 20 degrees either side of center. Surprisingly, the bike was actually MORE stable on loose gravel. The bike never swung like a pendulum when baring down, either. Personally, I’d use a flex-cable drive for this type of power-transmission.
“It looks as though it may try to lift the front wheel under power” Yea, the anti-dive geometry is works to help keep the front of the bike down. It’s worked quite well so far, keeps the bike quite calm even with choppy throttle and brake work.
“U-joint isn’t the smoothest way to apply power” no they’re not, but they’re STRONG. It’s rare on this bike to need much steering lock and power at the same time so the U-joint is rarely an issue.
I’m not a fan of flex cable drives. They’re flexy, can’t take much torque and have plenty of friction.
Marty, I’ve never actually used a flex drive in any design, so I’ll have to be cautious of the deficiencies you mentioned when it comes time. You guys did a great job superimposing the geometries of steering/suspension with the drive-line…then building a runner. Congratulations on your skilled work!!!
Here Paulinator: http://www.christinibicycles.com/bikes-longtravel.php
Holy Rokon, Batman! That’s a nifty looking system.
Exactly what I thought..Spawn of Rokon!
Awesome engineering work. Here’s to the Doers of the world.
All those flailing chains…..Hmmm. You know if I was looking at this problem, without cost constrants etc etc. I would have thought a electric motor in the front wheel hub would have worked?
That would be interesting to try on an electric dirt bike like a Zero. Slip control would have to be handled by a custom motor controller. The main challenges would be unsprung weight and the limited power of the front hub motor relative to the rear motor.
Wow, that’s incredibly impressive work. The overrun ratchet is a clever (and undoubtedly cheaper) solution rather than using a differential somewhere off the transmission.
Some polish would be needed to make this a production item, but it’s quite a concept.
Not to start a “stroke” war, but the only down side here is the 2 stroke. I say this ONLY because a nice 450 4 stroke would provide a lot more low end grunt which would definitely be suited for something of this nature.
depending on how they’re tuned, a two stroke can either be set up for high OR low rpm torque. I’ve owned both and you can’t beat the light weight, low cost/complexity, easy repair, and tractor pulling low RPM torque of a two stroke – what with power pulses at every revolution of the crank.
-todd
Actually, 2-Strokes make more torque. That and their light weight is why they are the kings of hard enduro. Not a single 4-stroke finished Erzberg. 23/25 finishers of Romanicas were 2-strokes. Hop on a 300, especially a ported one. More bottom end than a 450 and 30lbs less weight.
Hi Guys,
I just saw this thread. Impressive engineering. We made a similar designed AWD bicycle for BMW and Jeep back in 2000. It worked pretty well.
Here’s a link to the YouTube video of Geoff Aaron on our AWD CHRISTINI-KTM 300 at Erzberg. He finished 6th (Kyle Redmond Finished 5th) on our AWD 300 at their first race. We also finished 5th in Romaniacs that year. Take a look at the bike in action: http://www.youtube.com/watch?v=TE14nCmZzh4
Another reason why telescopic forks are obsolete…
Christini already makes a simpler system for this bike. It uses a telescopic drive running the length of the standard fork to the front hub. The power comes off a chain mounted on the front sprocket.
It looks a lot more sophisticated than the two wheel drive dirt bike someone made out of an XT500 here in the UK in the late 1980s or early 1990s. I remember seeing that and a guy I knew rode it and remarked that it was interesting, but not fully sorted. I’m curious to hear how this thing is to ride.
Interesting, clever and great work. BUT…
1. Telescopic forks have proven time and time again that the dive is beneficial to performance
2. This has increased wheel base which will hurt performance everywhere but climbing
3. Cost will be astronomical with the need to buy a shock
4. Weight (all up high), cost and complexity will be far more than Christini
5. The ratchet idea sounds cool BUT when turning the REAR wheel needs to spin faster, not the front.
I applaud them for the effort. They came up with a unique system and put in a LOT of work to build it, which must have been hard. But, do people ever ask before hand if it actually will have any benefits over what is already available? When designing something for function, it has to actually function better, or be cheaper. This is neither.
Let me dispute a couple of my own comments.
With a ratchet the front wheel will spin freely, and you can adjust rear wheel spin with gear ratio. So no issues there.
I still see weight up high, cost, anti-dive and complexity as the main problems.
Anti-dive has been ruled out after several attempts in the past and present, but I don’t know if this has been really tried heavily in dirt.
Good luck, hopefully we can see a third party comparison with Christini one day.
1) As a novice rider I certainly appreciate anti-dive with a soft off-road suspension. Instead of pitching forward when I grab a handful of brakes, My bike calmly stops with 1/3 the usual pitch and about half the suspension stroke left. This is likely no help to a expert or pro rider though. The AWD also helps with stops as it re-distributes the front braking between both wheels. This keeps the front wheel from locking while weight transfers, and if the front tire hits a small slick spot.
2) The wheelbase is less than 3 inches longer than stock. It’s hardly going to be an issue.
3-4) Yea, making this a conversion kit is going to be expensive. (See Christini AWD) Designed into the bike from the start, the extra cost should be minimal. (also see Christini AWD)
5) huh? The front tire goes around a larger radius in turns. Having the front/rear tires geared nearly the same and break free at the same time keeps traction balanced at all times. That eliminates any tendency to fishtail and makes the bike “point and shoot” even with the tires spun up.
I guess I don’t see how the AWD will help under brakes. I need to think about it more. But it provides forward drive.
With super soft off-road suspension, I see how anti-dive could help.
Take the cost of Christini ($4k), add a $1,000 shock, and some extra parts and this is too much. Like you said, best bet is to build complete bikes.
For the wheel speed difference, sliding the rear tire is common, and good, on dirt bikes. Letting the rear tire break and slide aids in turning. Not to mention, sliding is 50% of the fun of a dirt bike!
I guess I am not their market anyways, I would never buy an AWD bike. Just like AWD cars, it ruins the fun for me. Same with auto clutches.
No thank you to any multi-drive system.
Nice work Marty,
While some will tell you why its no good, wont work, blah blah. you have done it and shown it will work, and work well. Personally I like the fork design and think the benefits outweigh any shortcomings (if there are any).
Forget all the nay-sayers. Keep doing what you’re doing. Looks like you and your father are having fun being doers. Congrats!
Yamaha 2Trac
http://www.youtube.com/watch?v=4KSJEEMXRu8
http://www.mcnews.com.au/testing/yamaha/wr-2trac/page1.htm
One constant of the bike world that always exposes itself on the internet: Hardware intended for higher performance always irritates and confuses those happier with lower performance hardware.
My only concern would be steering when you lose traction in a turn. As it it now with a RWD bike, you can spin the rear wheel without the front wheel losing grip. With AWD, if you do manage to break the tires loose in the turn, won’t you also be inviting the front end to wash out? Maybe I’m a lousy rider, but losing the front end seems a whole lot worse to me than having some wheelspin out back.
My experience has been that as long as the front tire is spinning you can still steer. The steering does feel “loose” when the front starts spinning, but there’s no loss of control like can easily happen if the front wheel spins too slow or stops. A lot of the wash out scenarios I know about involve the front wheel spinning to slow or stopping. With the AWD, a quick burst of power is often all that’s needed get the front back under control if you feel the front tire washing out.
Seems to me that it would be a lot like driving an AWD car… Adding power pulls you in the right direction. “Don’t lift!”
Why not a CV joint? Weight and power handling?
I like this, seems good. BMW should put it on their street bikes
That cluster of 3 sprockets on the long chain is pretty cool, I would have thought there would be 2 chains and a double idler.
The initial U-joint vs CV choice mostly came down to availability and specifications. The U-joint started as a standard farm PTO part and I could find good drawings and torque ratings on the manufacturers web-site. A CV of similar size and ratings would either be an ATV part or custom. So I’d either spend $$$$ on a custom part or spend $$$ and weeks of wasted time buying, returning, and/or breaking random ATV parts. I decided I’d try a U-joint first and upgrade if it became a problem. So far the U-joint hasn’t been a problem so I’ve continued using one.
“BMW should put it on their street bikes” YES! I’d be happy to license the tech to them
Good luck with that. Just ask Hossack how it worked out for him. Once the IP lapses they’ll claim inventive license and call it “FWD-Lever”.
Personally would like to see how it compares to a machine being driven by hydraulic, isn’t it ohlins that has a pretty sweet set up? I think this looks cool, but mostly beneficial to beginners, really not that advantageous to really good riders. Still I would like to try it on the terrain and places I normally ride. It takes a lot to accomplish what these guys did, pretty cool
Compared to a hydraulic drive a chain drive can take a lot more power for a given weight, and is less sensitive to dirt and contamination. Chain is also cheaper to buy and replace.
It is rather a shame that Ohlins never got to sell that hydraulic drive setup. While limited, it’s one of the few designs that has a chance of being an economical conversion kit.
The Ohlin/Yamaha hydraulic system is way more elegant. Electric drive is also more elegant than all those whirling chains.