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I rode the Kiwibirds original Cristiani all wheeler drive KTM big bore special. It wasn't too impressive in the handling and steering department and not as much fun as a regular bike. On big hills it still got trapped it really takes spinning the rear tire. The front wasn't that helpful as it's only a percentage of the rear. It was interesting though. 

The new bikes are Chinese specials so good luck. 

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14 minutes ago, stevethe said:

I rode the Kiwibirds original Cristiani all wheeler drive KTM big bore special. It wasn't too impressive in the handling and steering department and not as much fun as a regular bike. On big hills it still got trapped it really takes spinning the rear tire. The front wasn't that helpful as it's only a percentage of the rear. It was interesting though. 

The new bikes are Chinese specials so good luck. 

Very interesting Steve.  Thank you for sharing with us.

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I research this every few years to look for developments. The Christini is the best functioning system with the lowest losses so far but in my opinion the weight and complexity completely cancels the advantages.

Yamaha and probably every other manufacturer has also tested hydraulic systems. Yamaha called it the "2 Trac" but it was developed by Ohlins. Much simpler with less parts using a hydraulic pump driven from the countershaft and a motor in the front hub. Still heavy and expensive but with even more losses than the mechanical system. I don't think this system has ever been fully optimized with an eye towards better fluid flow, optimized pump and motor and newer fluids. 

KTM and probably others have also looked at electric motors on the front hub and this will probably surface again soon as batteries and motors get smaller, lighter and cheaper. It can also be used only on demand with no losses other than added weight when turned off. It could be an easy bolt on universal kit but any offering would surely include excessive use of electronic control gadgetry and the same problem as the other systems,... much more unsprung weight.

I wanted to piece together a front assist kit for sport quads using off the shelf electric hub motors as proof of concept to see how big the effect was. I gave up after realizing standard parts needed so much modification it was best to re-invent everything and I wasn't that passionate about quads to get into it. 

There is no doubt that in some conditions, 2wd is a benefit. At least for now there is simply too much hardware needed to get that benefit which is seldom needed. It also completely violates my obsession with simplicity and low parts count. The lightest, cheapest, most reliable parts are the ones you leave off the bike. Everything,.. power, handling, suspension, brakes,.. works better with less weight. 

We tend to solve problems by adding something but sometimes less is more,.. Remove 50 lbs. from the average bike and you'll have way more fun than riding a 2 wheel drive pig.

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6 minutes ago, woodsryder said:

There is no doubt that in some conditions, 2wd is a benefit. 

OK im not so sure about this, perhaps a slow speed run through a mud hole, but even that's questionable...

on a big hill the front wheel should just touching the ground (if you want to change direction) or better yet, just off the ground. and there is no where else that I can think of that front wheel pulling would be of much benefit...I have not ridden a 2x2 bike, so I can't judge, but when I think about them, I end up just scratching my head !?!?!?

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IIRC, Yamaha made their version on a 250 4T for a desert race class.  I can see where AWD would be beneficial in desert racing or snow/ice racing but anywhere else I think the added weight and complexity would override the advantage.

It is interesting how Christini does not use hydro and how it only works when the rear is losing traction, just like the well designed automotive AWD systems do.

A feller I work with informed me that most AWD rally racecars are just 2WD most of the time, even though they boast AWD as the be all end all of that type of racing.  Not sure how accurate he is but it surprised me if it is true.

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Ive seen them on Dakar bikes so maybe better in deep sand... but then so is a lighter bike.

 

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It works great in one place I was stuck. Front wheel on big tree laying on its side. Rear wheel on ground,front wheel pulled it right over. 50% of the time better then only rear drive bike. HAAAA  the other 50%   worse.

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I had actually considered a project like this but instead of true 2wd, I wanted to add an electrically driven front hub that was controlled via a set of sensors measuring the speed differential between the front and rear wheels.  If a delta was detected, specifically, the rear wheel was turning at a faster speed than the front, the electric motor would engage to "pull" the bike through. 

I doubt the benefits would be worth the hassle and weight, but thought it'd make a cool project.  One of these days, post retirement, I'll get around to it.

Edited by baglock1

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Rokon had 2wd.  What a tank that was.  You could put 7gallons of fuel or water in each wheel.  I think they still sell them

In sand, Yamaha BW200 works fantastic.  We rode one on the beach with swim trunks and flip-flops.  Very comfortable in sand.  They also had a 350 version.  

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17 minutes ago, Baja Rambler said:

Rokon had 2wd.  What a tank that was.  You could put 7gallons of fuel or water in each wheel.  I think they still sell them

They do still sell them and they're ridiculously expensive for what they are.  I'd love to have one but can't see paying for one.  I think they'd be perfect if you had some heavily forested/overgrown, rugged land that you wanted to cruise around on.

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All 2wd dirt bikes look like a ROKON in my eyes....

Lol

I don't see anything super cool or high tech ...

As soon as anyone shows anything, all I see is ROKON...

 

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Here's my two cents worth on 2WD, I posted it on another site and have simply copied it here. I must add that I have owned a KTM350 Freeride for four years so my opinion is a bit biased.

 

I'd love to try a Freeride E but I don't think there are any in Australia and there are certainly none where I live

I got to thinking about an electric Freeride but on a different train of thought from KTM's idea.

These are just some ideas I dreamed up during a boring day, they may or may not be valid and/or start a discussion
I don't know much about electrics and control systems but I'm sure someone on here can add their thoughts

1 Regenerative braking, should add to battery life.
Can it be moderated like the normal brakes?
Is there a limit on how fast the charge can be pushed back into the battery?
May need a manual braking back up in some circumstances.

2 Hub centre motor(s)
Would add unsprung weight but do away with a chain and all that goes with it. Would also allow more space for batteries where the motor normally sits.
Why not run two? One front, one rear. Set up a steering angle sensor and vary the speed so both wheels run at the true speed of the arc when cornering. Perhaps reduce power to a spinning wheel or add power to one under more load

Like I say just ideas

Cheers

Brent

Edited by brent j
Adding info

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2 hours ago, brent j said:


1 Regenerative braking , should add to battery life.
Can it be moderated like the normal brakes?
Is there a limit on how fast the charge can be pushed back into the battery?
May need a manual braking back up in some circumstances.

Regen fades to zero as you stop and always needs mechanical brakes. Batteries won't accept charge too fast so I suspect they use capacitors for short term storage. Capturing wasted energy is always good but brakes aren't as heavily used on dirt bikes as say roadracers.


2 Hub centre motor(s),.. Would add unsprung weight. 

Yes, way too much unsprung weight along with steering mass. Its also hard to design a motor with enough direct drive torque for a large wheel and not need internal gearing. Internal geared motors are smaller diameter but also noisier with more transmission losses. It makes sense to use a powerful frame mounted  rear motor chain driven to the wheel to keep efficiency up and unsprung weight down, The front needs much less assist so hub motors look better there to avoid wierd telescoping drive shafts and such.

For a road bike, a forward facing swingarm suspension with hub center steering and frame mounted motorchain driven motor would solve many problems but couldn't handle the long travel for off road use. I watched motors and batteries evolve in the R/C model plane industry and think we are just a couple more battery improvements away from a viable E-bike. They are already making a good showing at th Isle of Man TT and Pikes Peak hill climb despite their heavier weights.

 

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4 hours ago, brent j said:

2 Hub centre motor(s)
Would add unsprung weight but do away with a chain and all that goes with it. Would also allow more space for batteries where the motor normally sits.
Why not run two? One front, one rear. Set up a steering angle sensor and vary the speed so both wheels run at the true speed of the arc when cornering. Perhaps reduce power to a spinning wheel or add power to one under more load

Like I say just ideas

Cheers

Brent

just one more idea to kick around...

how about using the wheel itself as the motor stator. Position perm. magnets around the wheel rim, and then place the switching electro magnets on the swing arm and or forks and now you have motion. The advantage here is the very long distance from the axle center to the forces generated by the magnetic flux thus creating a rather high torque motor without having to employ any gear reduction at all. this design also minimizes sprung and un-sprung weight....

Love to ponder...!

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Brent. 

Your assumptions are all good ones and Bicycles have tried these ideas and more. Large dia. motor is better but also drastically increases flywheel effect as weight is moved outward. Its called a higher polar moment of inertia and less is better. The gyro effect would be massive and unwelcome. Also protecting the magnets would be an issue. Shock will weaken magnets and they could pick up all kinds of debris from iron rich soil. Off road bikes are a pretty hostile environment for technology. 

Typically a 2wd bike will power the front wheel at a reduced speed so its effect is only felt when traction on the rear is reduced. the front freewheels most of the time.

lots of development has been done already

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