Fantasy racing bike.

[dogman dan]

I keep having this fantasy for a race bike. Dual hub, with two controllers. The front hub would be something fairly mild, like 1500 watts and a top speed of 30 mph. The rear hub would be crazy powerfull, more like a dragster bike. The rear hub would have a throttle and a monster controller.

The front hub though, would have an ebrake cut off, and it's throttle would be set to the max and locked. There would be an additional kill switch on the bars too.

In a race on the kart track it would work like this, the front hub would pull constantly, unless you pulled a brake lever. The power of the front hub is primarily used simply to improve your traction in the corners, providing a steady pull all the way through, but not really accelerate you. When you got to the wider corners, you'd add power with the rear motor. On the straight, you'd grab the rear hub throttle and smoke the rear tire with 6000 watts.

Not that I could handle such a beast, but I can in a fantasy. But would it get too inefficient? with the rear hub having to drag the slower front hub down the straights? gearmotor for the front?

 

[liveforphysics]

Wouldn't it be best to use that weight/bulk/complexity of the front motor-controller system towards making a stronger rear wheel drive motor?

I can't imagine it ever having an advantage to driving the front when you could spend that same power driving the rear wheel harder.

Anytime you want to accelerate, the rear wheel should be able to provide enough thrust to let the rider simply modulate throttle to maintain the front wheel off the ground until they need to brake for the next turn again. At least that's how it seems to work with the dirtbikes and streetbikes I've got. I've simply never had a time when powering the front wheel could have been helpful, or had it's available traction better spent towards trying to accelerate rather than being fully dedicated to the cornering/braking aspects, as when you desire to accelerate, the front is no longer in contact with the ground.

 

[AussieJester]

I can't imagine it ever having an advantage to driving the front when you could spend that same power driving the rear wheel harder.
.

You need to drum this into your Costa Ricca pal Luke i gather he still on about his great 2wd idea that will show us all how its done :-S (wouldnt know god bless ignore button)
Only time 2wd bikes have been proven any use is in very sandy conditions off road and extremely wet conditions on the track with average level rider on board, if it was such a brilliant revolutionary idea dont these clowns think major factories would be offering up a variety of 2wd bikes and conversion kits seeing the likes of Yamaha and KTM have had proto type 2wd bikes since early 2000? I guess the people that think its good havent ridden motorcycles in competition or at least at anything above cruising speed :-S Losing the front wheel on corners when cranked over is bad enough without the thing being powered too! it would be suicidal laid over powering through a corner with the front wheel spinning up IMO... Save your $$$ dogman buy more lipos and go with at least a rear frock, preferably a multi speed non frock setup so you can cut the weight down and get the bike better balanced.

KiM

 

[torker]

Yea I think these guys are right Dogman. I know what you're thinkin thogh - hmm I have the parts on hand But I think put some more lipo on the handlebars. Pulling a wheelie halfway down the straights would be the best pr an electric bike would need. And one great photo op.

 

[Ykick]

I don't know you too well but I enjoy a lot of your posts/ideas. Always useful stuff to ponder but I think the nay comments here are correct. Put your time, energy and money into a very serious rear hub using as many motorcycle wheel/brake components as possible. Work out the pedal gearing to where you can actually add something pulling out of corners and down stretches. Perhaps one of those 2spd cranks?

You're then free to go really crazy on the front with Gucci suspension forks, wheels and top drawer braking where it would probably do the most good. Wheelies could be awesome too!

 

[Drunkskunk]

when you're in a corner on dry pavement going as fast as you can, your tires will be at the limit of their traction. adding torque at that point will only cause you to lose traction.

Off road in loose sand or gravel with the front and rear motors balanced for power, its another story. if you could keep your balance in something like that, it should corner and climb like a cat on carpet.

 

[Thud]

The Last thing I ever want riding off road, is another 12# riding in my front wheel....power or no power...

 

[michaelplogue]

when you're in a corner on dry pavement going as fast as you can, your tires will be at the limit of their traction. adding torque at that point will only cause you to lose traction.

This was my thought as well. A free wheeling front wheel will only lose traction from lateral forces (assuming no brakes). Add a motor to it and you actually increase your chances of it losing it's grip.

 

[Dave Sloan]

I would like to add the positive aspects to your fantacy racing bike. Now that you have a front hub that will keep everything on the ground as much as possible - wouldn't it be nice to add a detector to the front shock that would apply that 6000w LiPo rear power the more the shock was compressed. That would ensure that as much power was being pumped into the forward motion as possible without loosing control.

 

[FMB42]

Here's a link to Tony Foale's "Motorcycle handling and chassis design: the art and science":

http://books.google.com/books?id=84hF-qoR5I8C&pg=SA18-PA8&lpg=SA18-PA8&dq=front+wheel+drive+motorcycle+handling+problems&source=bl&ots=FYD3sINfQh&sig=KVoc4mu8vY13dEAGqLScKI3foik&hl=en&ei=ws6cTNP0FoLmsQPwoITWAQ&sa=X&oi=book_result&ct=result&resnum=9&ved=0CD0Q6AEwCA#v=onepage&q&f=false

There's a section on front wheel drive that might help answer any questions you have on this subject.

Tony Foale's series of technical writings and books on motorcycle chassis design and handling is, IMO, pretty much the "go to" source for this topic.


Good luck and good riding!

 

[GrayKard]

when you're in a corner on dry pavement going as fast as you can, your tires will be at the limit of their traction. adding torque at that point will only cause you to lose traction.

Off road in loose sand or gravel with the front and rear motors balanced for power, its another story. if you could keep your balance in something like that, it should corner and climb like a cat on carpet.

It's even easier to keep your balance in sand, gravel, mud, and wet grass on a 2wd bike as opposed to rear wheel drive either motor or peddling. Helps to have slow wind motors too as you have more throttle resolution and less tendency to spin out.

I grew up riding a bike in sand and gravel so learned early how to handle it. We used to have lots of fun locking up the coaster brake to see how far we could skid through the gravel.

Gary

 

[John in CR]

A lot of incorrect input from people who probably haven't ridden a front wheel drive bike to understand the handling benefits first hand, including Tony Foale himself, who predicted the front wheel pulling torque in a turn would create more lean, which I never noticed. Everyone running 2wd loves it, so I'd go on the word of users than speculators.

In my case, the primary goal is to go to pretty extreme power without stressing system components, especially the controllers which cry at high current with my 2 turn windings. With one motor, then I have to ventilate the motor, but the controller is still at risk. I ran a front hub for a few months, so I believe 2wd will have a handling advantage, and I'll have regen braking in both wheels instead of just one.

Unsprung weight is the only real detriment I see, but that's an issue with all hubmotors, but it's only an issue on bumpy terrain. A moderate sized front hub doesn't weigh any more than than a small motorcycle's hub, disc, and brake caliper, so I'm not sure the detriment outweighs the benefits.

The part I don't understand with Dogman's fantasy racer is why just the on/off with WOT only for the on position of the front hub? I'm going to try mine first with 2 throttles, one left and one right. If that turns out to be problematic, then I'll tied 2 throttles together as one for my solution.

John

 

[Drunkskunk]

It's even easier to keep your balance in sand, gravel, mud, and wet grass on a 2wd bike as opposed to rear wheel drive either motor or peddling. Helps to have slow wind motors too as you have more throttle resolution and less tendency to spin out.

I grew up riding a bike in sand and gravel so learned early how to handle it. We used to have lots of fun locking up the coaster brake to see how far we could skid through the gravel.

Gary

I don't know if I would call it easier, since basic bike balance comes from your ability to center the bike under your center of mass by inputs from the front wheel, but I will conceed that it may be easier for you.

And its a hell of a lot of fun either way! Rear wheel drive is more fun for me on wet grass and sand, but thats more of a prefrence and my personal skill. But give me Mud, loose dirt, hills, gravel, and I want my front motor.

 

[Thud]

I have never ridden a FWD motorcycle...but can theroize the benifit ...as much as I hate driving FWD auto's... they are better in winter snow (I allways asumed from the weight bias over the driving wheels) then again I never drove a mid engine auto on snow......the rally guy's seem to have addapted briliantly.

The only negative I can see is the added weight in the front wheel...It may not be a complete hinderance on pavement. once off road there are 2 schools...high speed off-road motocross, & low speed enduro type
the current FWD kits are being contested in the enduro & enduro-cross series....some one must like the way it rides.
Hubbies are the perfect platform to put it to the test.....Dogman likes the way his bike runs & he's no slouch in the corners....so we'll just have to see whats what at the DR.
When it come down apples to apples...eventualy weight will become a deciding factor. The weight limit in the "World challange" kinda negates the option at that venue, but the death race is wide open.
Bring It.

 

[gwhy!]

They played briefly with 2wd on trials bikes ( you would have thought it would be a perfect application for 2wd ) the top riders that were beta testing them all concluded that there was no benefit and in fact it was a hindrance for control and finding traction ( which was odd ). Personally I think it will not be very good for enduance or MX but for something like supermoto or circuit racing , 2wd may start to shine..

 

[dogman dan]

Too much time driving my subaru? I know I love the all wheel drive on it. Seems like Pastrana likes it too.

So dog logic seems to say that all wheel drive would be good on a two wheeler too. Perhaps it's all in my head, but at lower power like 1000 watts I know I can feel a lot of improvent in my abilty to hold a corner with front drive. Hence my suicidal desire to try it at least once at 3000 watts.

The 1000 watt 30 mph max speed motor I ran in the death race was the perfect amount of power and near the fastest speed anybody on that track was taking the corners. They all just passed me on the straights is the thing. It appeared to me that I was faster at the apex of the corners than 90% of the field though, since I had some extra traction happening on the front hub. I was touching the brakes, then full on the throttle all the way through the corner while others often seemed a bit loose till they got past the apex and throttled up. Then it would look like I was standing still, but I swear I was fast in the corner and passed a few by taking that corner faster.

So this fantasy is to have that same setup though the corners, and then grab real wattage once past the apex. The throttle always on thing would just be a way to avoid having to modulate dual throttles. It would be low power on the front, so you'd never have too much on even the tightest corner.

The real question in my mind, is would this kind of thing be better, or worse, than just having two motors powered off of one throttle and having equal power.

I totally understand the idea that getting the weight on the rear wheel to accelerate is where it's at on the straight. But what I'm trying to grope for here, is a way to stay powered up all the way through the corner. With lots of power it's seeming touchy to grab throttle before the apex. I'm no real racer, so I have a lot to learn for sure. But I roared up a lot of sandy arroyos and snowy roads to ski areas, and in those conditions getting off the throttle would kill you. Instant stuck in the sand, or spun out on the snow. So I have this, never coast through the corners attitude.

Thanks for the link, I'll look at that. All this is not unknown. just unknown to me.

As for unsprung weight, at this point, the whole bike is unsprung. But yeah, once you have shocks, all hubmotors start sucking a lot more .

I've been thinking about this bike for about 2 years now, but it started as a dirt bike idea. I was thinking dual bmc 600 watt motors at that point, for serious hill climbing. There was once a bike like that,. Cubman? It had huge atv type tires and 2wd. Hunters and prospectors loved em before quads were invented.

I was thinking trials type riding when the idea was for a dirt bike, but now I realize why that sucked. Just too heavy on the front wheel, and harder to pop over stuff when you need to. Now I do insist on rear hub on dirt for this reason. But I have enjoyed powersiliding a front hub in the loose sand on a packed dirt road. It's a weird feeling, and some can't get used to it just like they feel about front drive cars. The same broady you do with the rear all the time does feel scarier with the front drive bike, but it works once you learn how. I set out to learn how, because it's gonna happen on that sandy corner on pavement. Now I don't even blink when I hit the sandy corners riding to work.

I'm just crazy enough to try anything. I used to hear people tell me all the time " you can't do that on those ski's." Watch me, I'd reply. My bro said I did stuff like that because I wasn't crashing enough on regular skis.

 

[docnjoj]

I've been thinking about this bike for about 2 years now, but it started as a dirt bike idea. I was thinking dual bmc 600 watt motors at that point, for serious hill climbing. There was once a bike like that,. Cubman? It had huge atv type tires and 2wd. Hunters and prospectors loved em before quads were invented.

They are still around.

http://www.rokon.com/about/index.htm
Rotax/Rokon made the 2 W/D 2 wheelers that the linemen used in Vermont snow. I think you may be on the right track with 2w/d. Good luck in October!
otherDoc

 

[dogman dan]

Ok, I just read the excerpt from Tony Foale. I think I understand it, what he's saying about enough power, applied off center, would tend to pull the handlebars back straight again, out of the curve.

I don't think I'm at a power level where this is significant, and the skinny tires of a bike may help too. So that may explain why I feel sticky and good when I use the front hub at moderate power levels. Even now with 3000 watts on tap, I'm at what 4 hp? Wooo.

So while I can see why it might not work well at 30 or more hp, I don't see why it would have to suck at 4 hp. Clearly at high power, the motor pull could suck your handlebars back straight, and you fly off the corner. With rear drive, there is no ability to pivot, and the frame absorbs the forces. But on front, you'd have to push back with brute strength.

At 4 hp, it's just not taking that much brute strength. At slower speeds on the bike last spring, I was able to pedal around a sharp corner without pedal strike, and did enjoy 2wd traction. It felt good. Now the bike I have cannot be pedaled through a corner and I only have front drive till I straighten up.

At this point I think I can say experience with front hub shows it works, but at higher power it could be very different. I'm not even recalling anybody else running 100v through a frontie at the moment. I may be in ugknown territory for ebikes already.

 

[Thud]

I recall Methods had a video of him doing front wheel burn-outs with 100v @ 100amps (wife was running the video) I beleive he wallerd out the drop-outs & scraped that bike....its out there somewhere.

 

[dogman dan]

I had a feeling somebody had at least tried it. ( high power front hub) Figures it would be one of the regular experimenters here. I did have to weld some steel onto my forks. The first run, I was lucky not to ruin a motor and controller. I wallowed the dropouts some even with two torque arms.

I know some folks are out there running front x5's at pretty hefty power. Like 48v 50 amps. That's not so uncommon. I just didn't recall any specifics of somebody crossing the 3000 watt line with one. I still can't believe it when I take off from a stop and see 3200 on the CA. I still haven't even beefed up the stock 9c phase wires.

 

[Toorbough ULL-Zeveigh]

It appeared to me that I was faster at the apex of the corners than 90% of the field though, since I had some extra traction happening on the front hub.

perhaps what ur seeing there is the result of an elektrix inherent advantage having available torque all the way down to zero & irrelevant being front or back?
if i recall, u were the only electric in the race so no chance to duel with a rear hub.

did ur bike weigh any less than the gassers, or possibly better weight distribution, which might account some for a faster turn-in.
another factor might be that ur race bike seems like it has an awfully short wheelbase (altho that could be from being distorted in the pix).
plus don't underestimate that u just might be the more talented pilot, doubtful if anyone there is a pro.

so i think there's still some variables that need to be pinned down how much benefit there really is to fwd on dry pavement.
but i'm more optimistic than most, seems to me operating at the limits of traction on dry should be no different than normal riding on the wet or sno & ice so keep probing the limits.

 

[FMB42]

Torque steer is one of the biggest problems with FWD/AWD vehicles. Fortunately, power steering and computerized traction control and stability systems do much to alleviate the adverse affects of torque steer with late model autos and, as such, many people never give it (torque steer) much thought (until they start taking some really hard corners on dry pavement). FWD/AWD can, of course, offer greatly improved overall traction in certain off road and/or slick pavement (snow, ice, rain, etc) conditions. However these conditions are entirely different than that of "dry" high speed paved roads and/or courses. Another problem with FWD is that the steering system must not only perform its basic function of steering but, must also be designed to drive the vehicle as well.


I myself, have never cared much for the adverse effects of torque steer during hard cornering on dry pavement. Fighting with the steering wheel while trying to correct the unwanted directional changes just isn't very appealing IMO. But then again, maybe this is partly why FWD/AWD systems are rarely used on dry condition closed circuit high speed pavement racing venues such as Indy, F1, Nascar, and motorcycle road racing events.


The good news here is that vehicle manufacturer's will, no doubt, eventually solve the problems associated with torque steer (by use of extremely sophisticated computerized feedback control).

 

[liveforphysics]

All the computers in the world can't solve weight shifting off thee front wheel(s) as the vehicle accelerates.

Also, imho, as a guy who drives/races an absurdly over powered FWD, torque street is the least of the problems. Proper suspension design (aka, not some gay struts) equal axle lengths, and a good LSD make torque steer something fixed by simply gripping the wheel a bit harder.

FWD can be made to work, and made to work awesome in a car, but its tough.
RWD can be made to work, and its easy.
AWD just seems to fail IMHO (for dry pavement). There is a good reason everytime you see a crazy fast subaru or skyline etc on a roadcourse, its had the front axles pulled and the center diff welded. Same with drag cars even. When they start getting really fast, the subarus, evos, skylines, DSMs etc convert to RWD.

The AWD cars that handle well are often RWD only cars when over 30mph or so (if they have that ability).

 

[dogman dan]

Makes sense LFP. I can't say I push anything at all in my subaru on dry pavement. But I do love how it feels on a sandy or snowy road. Totally different situations.

To summarize, the bike I raced last spring was a cheapie wallmart mongoose. I may have just had more balls to enter the corner fast, but that confidence was coming from me thinking I had an advantage. At low power at least, placebo works. :lol: I might be more skilled, I skiied a TON, and skiing and cornering motorcycles are very transferrable skills. All the other bikes in the race were rear drive gassers. Many were much faster than me, and left me. The rest, the slow guys were probobally easy to beat. But several of the fast guys could not take me in the corners, and had to take me on a straight section.

FR31, who won, seemed able to take anybody anytime, anywhere on the track. 8) If you watch the video close, you can see him decide, ok enough fun and good video, lets just win this now.

This years bike is a normal wheelbase vintage hardtail MTB. It does have a short frame vertically, and the battery box makes it look short horizontally.

This discussion has helped a lot. Now I do realize why I'll need to go to rear drive as power increases. A lower power front hub may only be good for the placebo effect. However, if it makes me braver it has a good effect.

 

[jdcburg]

I don't know anything about racing or dirt bikes, but if I were doing it, I think I would have the fwd on a throttle so I would have the control needed through the corners. Then I'd put the rwd on a momentary toggle switch and relay for use on the straights. As long as it's a fantasy, make it a 2 position switch - 3/4 power in the middle and full power all the way down - jd