gwhy!1
100 kW
zombiess said:
Your not wrong, I have ridden some scooters with very bad cvt's but I have also ridden scooters with very good cvts so it very much depends on the setup.
Conclusive proof gearboxes are awesome.
- Thread starter Teh Stork
- Start date
Your not wrong, I have ridden some scooters with very bad cvt's but I have also ridden scooters with very good cvts so it very much depends on the setup.
motomoto
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Zombiess wrote"
A pro motocross racer launches his bike out of the gate with 12,000 RPMs worth of kinetic energy in the crankshaft and outer clutch and plates and uses it within a seconds time.
You could do the same thing using an electric motor, but I am sure Lukes' solution can generate that kind of power instantly to accelerate a motorcycle from a stop.
A pro motocross racer launches his bike out of the gate with 12,000 RPMs worth of kinetic energy in the crankshaft and outer clutch and plates and uses it within a seconds time.
You could do the same thing using an electric motor, but I am sure Lukes' solution can generate that kind of power instantly to accelerate a motorcycle from a stop.
Chalo
100 TW
Arlo1 said:
For a brief moment, the heat dumped into the clutch probably does approach 75kW in some cases. It's only the power to the wheel that doesn't get anywhere near that.
Meanwhile, electrics can deliver full torque from zero RPM, without a clutch to eat up the power.
motomoto
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I kind of get tired of hearing the term "full torque". It means nothing unless it can get things spinning quickly enough to produce the desired result. I think
the only thing that is going to get a tire spinning quickly enough to launch a race bike properly is a whole lot of stored inertia released upon the drive system
suddenly and violently. Trying to get that out of an electric motor would just produce a shower of sparks.
the only thing that is going to get a tire spinning quickly enough to launch a race bike properly is a whole lot of stored inertia released upon the drive system
suddenly and violently. Trying to get that out of an electric motor would just produce a shower of sparks.
You are so so SO wrong on so many levels my friend!motomoto said:
Torque is what makes it all happen to get started. Everything starts at 0 rpm which means 0 HP no matter how powerful the motor if wheel RPM is 0 then HP at the wheel is 0 as well. What starts the wheel in motion is torque 20 ft/lbs at 0 rpm would make it start to move 1/2 as fast a 40 ft/lbs at 0 rpm.
This stored inertia you speak of is complete bull it does nothing! Why the "RACER" ( I raced Motocross for 5 years and was up with the pros when I ran out of money and guts after all my injuries.) Uses a clutch to bring the rpm of the motor up is because they need to get the motor up past the peak of the torque curve. This as Chalo pointed out is not needed in an electric. If a "racer" revs a bike to hi and dumps the clutch to hard on a slightly slippery start he will just spin more and not have the desired traction. Most motocross gates are in cement now so you have to get the sweet spot by not applying to much torque to the wheel until off the cement and try to have a clean surface Burnouts just waste your sharp tire. It all happens very fast but when I have a cement launch I spin the tire a bit and sweep the cement as clean as I can then Raise the rpm on the 4strokes to about 1/2 max and feed the clutch out smoothly and the clutch is not out all the way until about 3 feet into the dirt!
Therefor making this fictitious big fake burst of power you think comes out of thin air would still be a waste of power and just slow you down as you spin more!
Full torque at 0 rpm is a great thing when you ride a real electric motorcycle you will appreciate it! The new Zeros are just being shipped and BRD is planed for this year as well we will see in the next 1-2 years electrics getting hotshots like you have never seen against ICE powered bikes for the first time in history!
liveforphysics
100 TW
motomoto said:
You're right, no electric motor drivetrain bike could ever just explode forward like as hard as dropping the clutch on any trials bike out there, which doesn't have a swing-arm nearly as long but it will still just leap into the air at the twitch of the throttle catapulting people with enough force to knock there shoe off to go spinning away flying forward with the bike jumping and skidding in gravel for another 10ft or so spinning a bit, and yet still be geared like it's in "5th gear" already with respect to the desired top speed it had at the time (about 70mph, and I didn't want to even ride it that speed on that sketchy-ass twitchy frame while I was road racing it around laguna seca).
Enjoy ES. We make things you wouldn't expect would be possible happen here, and still be quite efficient transportation forms with respect to most all other forms, including just human-pedal cycling for transportation. The no-load on that motor wasn't very high at all, like 5amps or something at 60v IIRC, so even though it was a regularly drawing like 5kw just cruising along and in normal acceleration and things, when it was pulling 5kw, it was putting like 91% of it (or something) into actually reaching the ground, which is quite a big difference in efficiency than the guys dumping 5kw into a radically under-sized-to-be-efficient-at-those-speeds hubmotor, and getting about 3kw of actual mechanical propulsion of energy back out. That agni bike had a pretty darn good Wh/mile due to that super high efficiency low no-load current motor. Thank you Cedric Lynch for figuring out that brilliant little design of a motor, a brushed that typically bests most all but the best of brushless with respect too efficiency, yet still will catapult a man by his groin hard enough to make his shoe fly off at just a brief touch of the throttle when you hit it with 650A geared 12/71 on a bicycle that has a long enough wheelbase so it has to just catapult by design rather than fly out from under you leaving you dropping straight down like the short wheel-base bike wheelie video wrecks always feel like.
It can be done. It is technologically possible to achieve both all the speed and all the torque at the wheel you could ever want on a bicycle at a speed higher than you want to even be riding on it for strong threat of imminent death if you don't slow it down a tad. Yet still have a bicycle that was a pretty reasonable ion de-charging sipper when using only like 5% of available power in operation, and had a very reasonable Wh/mile when driven riding along a non-powered good road cyclist buddy on a lunch ride. It was also an eerily quiet bike from using no chain-guides of any kind to make chain jingling friction sounds. It was perhaps the most quiet ebike I've ever heard. Maybe only Arlo's 5305 BMX was close to as quiet, but I think even it was still louder. Slow moving bike chains in new-condition on fresh new proper sprockets and fairly high static tension, way higher than the maximum efficiency more relaxed chain tension would be which also would let the chain last a lot longer to prevent skipping teeth from the frame flexing in about a 1/2" or so when you hit the throttle.
That bike was another proof-in-pudding for me of the tiny motor being most efficient for me. If you can get a big ass motor with respect to physical size, yet critically still manage to keep the no-load current value very low so it cruises with only 2-4A higher than the best of the small hub-motors, but you were planning on drawing an average power level of like 50A or something while riding, and with the remaining 46Ah you've got to transform electrical energy into mechanical energy with, and you've got all the physics of doing this in your favor with respect to amazingly good copper fill to end-turn resistive heat with respect to end-turn losses, and a generously large flux gap area and even a little help from about 5:1 gearing multiplication.
You guys do realize putting an Agni on your bicycle to just be a direct-drive hub would actually be a very fast and quick acceleration bicycle with respect to all other e-bicycles in the world, but on-top of that, you get to gear it 5:1 to make it hit like the torque of 5 of those hubmotors (it would put down 630-ft-lbs,which was hard to read accurately because the dyno roller would heat the tires to destruction when you strap them hard enough to not slip on the roller face, because even though you filled them with like 60psi, they are still comically bulged out at the bottom so it almost looks like it's in perpetual rim-cut danger just to get it pushed hard enough against the roller not to slip when trying to measure 610?ft-lbs of rear wheel torque, which is like the equal of trying to dyno a short-geared dirtbike in 1st gear with respect to the problems tire spin causes you when trying to measure how much torque it can produce, it just keeps violently spinning the tire up making a big ring of smoke instantly appearing around the tire, which would pop, and even managed to capture the moment of one popping by accident just through filming various dyno runs in testing and happening to get it on film.
So so so so glad I moved away from bicycle tires on that bike. Bicycle tires are death on deathbike. Good sticky premium R-compound race slicks made for 100hp racing-only superbikes are so much better suited for the application, both on and off road. That vehicle is not nearly as hard on a race tire as a full motorcycle, even though I bet with my 220lbs ass on it it likely weighs as much as a featherweight rider on a tiny RS125 or something. Now that I think about it, it's likely entirely because it corners like a giant wallowing pig to ride with that longer-than-many-real-motorcycles wheel base, and has no rear suspension, and doesn't handle nearly wheel enough to be safe doing >105mph with it's new improved drive-train that was staying fairly cool operating around laguna seca with at the previous re-fuel event last year, and still being a relative ion-sipper.
Enjoy this video's slow-motion section. In normal speed it's so fast you can't even catch all the funny details.
http://vimeo.com/23752461
John in CR
100 TW
It's no use guys. You're talking to someone accustomed to a motor that needed a 9 speed to get it rolling. It has to be experienced. I'm sure the guy that flipped off of Deathbike 1 and lost his shoe gets it.
Motomoto, haven't you ever noticed that gassers need an rpm# next to their torque number, but electrics don't? Did you see the new AMG Mercedes SLS coming out? A motor in each wheel, obviously single speed with 740hp and 738ftlbs of torque. That torque by the way starts at 0 rpm and most likely is flat right up to peak power. Forget everything you knew about gassers, because much of it doesn't apply to electrics. Launches is something we're having issues with on the high power bikes using cheap controllers, and it's not because they're too weak. It's because the launch it too violent.
Motomoto, haven't you ever noticed that gassers need an rpm# next to their torque number, but electrics don't? Did you see the new AMG Mercedes SLS coming out? A motor in each wheel, obviously single speed with 740hp and 738ftlbs of torque. That torque by the way starts at 0 rpm and most likely is flat right up to peak power. Forget everything you knew about gassers, because much of it doesn't apply to electrics. Launches is something we're having issues with on the high power bikes using cheap controllers, and it's not because they're too weak. It's because the launch it too violent.
liveforphysics
100 TW
motomoto said:
This statement exists in your mind to say because you've had experience with rc-sized motors with lots of gearing to make torque.
Try a motor that first off makes about 2-5x more torque per amp fed to it like the typical RC motors, but then doesn't saturate until another 5x more current at least around those little teeth in the RC motor, so now you're at as much as a 25:1 motor torque multiplier, yet not using any additional power to have this multiplier, you're making this torque very energy efficiently still, and the motor still spins up to 6500rpms or so with the right reasonable pack voltage (80v?) so you still get to multiply this torque by about a 5:1 ratio before hit hits the wheel. Your RC motor with higher KV and higher shaft speeds get's to multiply by about 10:1, maybe 15:1, which would be a 3x torque output multiplying advantage. Fortunately, this 3x penalty in gearing pales in comparison to being able to efficiently-enough make about 25x more torque at the motor, for a winning advantage of about 8-ish times more torque at the wheel than you've got in your experience with most RC motor setups, yet it makes it more efficiently with less moving parts and slower moving parts and less system complexity, at a very real system penalty of weighing at least >15lbs more in drivetrain wight than the RC motor setup. Both are going to end up with similar final efficiencies when riding around doing normal ebike stuff, just one weighs 15lbs more, yet provides something like 4-8x more rear-wheel torque to the party available at all times over nearly it's whole speed range at the twitch of a wrist at any time, and still able to reach speeds higher than you even want to be traveling at on a bicycle and cruise at them for 10minutes of continuous WOT output on a punishing elevation-change full-size motorcycle racetrack without overheating. But it is a heavier way to do it, so if weight is really the absolute key critical factor, the RC motor bike is going to be lighter and hence better for that particular application where weight is so critical. For all other applications, give me another 15lbs on the bike please, and a super-size dish of the reliability and silence that comes from big slow moving full-size-motorcycle drivetrain size parts applied to a bicycle.
You can achieve drivetrain perfection. I think you can with hubmotors (though it hasn't been done yet, I think John has some that are getting the closest, and cromotor is also a step in the right direction for the guys who aren't just trying to average 500w to get around, but more like averaging 3-5kw to get around doing 50-60mph everywhere you go. You know who you all are out there, it's ok, I'm on your side.
motomoto
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Arlo1 wrote:
I have been emailing with Marc at BRD. He says the ICE bikes get the jump on the electric at the start because the clutch hand is quicker than the throttle hand. I can see that. When the throttle
is turned, if there is any hesitation in the circuitry, you are going to get beat at the start. He says they are trying to work it out with programming, but as a last resort, are considering a clutch even though it would add a few pounds.
I sure would like to see some video on how the BRD bike puts 5 seconds a lap on a KTM 250 like they claim. All I have seen are lame videos of all the electric mx bikes. The new Zero
videos are the best. I want the electric bikes to beat the gas bikes, that's why I mention my ideas and will implement them in my build.
I have been emailing with Marc at BRD. He says the ICE bikes get the jump on the electric at the start because the clutch hand is quicker than the throttle hand. I can see that. When the throttle
is turned, if there is any hesitation in the circuitry, you are going to get beat at the start. He says they are trying to work it out with programming, but as a last resort, are considering a clutch even though it would add a few pounds.
I sure would like to see some video on how the BRD bike puts 5 seconds a lap on a KTM 250 like they claim. All I have seen are lame videos of all the electric mx bikes. The new Zero
videos are the best. I want the electric bikes to beat the gas bikes, that's why I mention my ideas and will implement them in my build.
liveforphysics
100 TW
motomoto said:
I've not had chance to ride the BRD bike yet. I have seen electric holeshots that delivered the goods you're talking about though.
I've watched the 2013 Zero FX and MX bikes both hang dead-side-by side a properly launched 2012 honda CRF-250R dirtbike, both had the front wheel off the ground by just about 4" which is right about peak-possible acceleration position for those bikes chassis from about 0mph to about 50mph, but I think the CRF-250R ran out of the power to hold it's tire up still on the factory gearing before the Zero did, even though the Zero had a 30lbs heavier non-professional-motorcross-rider on it just leaning as much of his weight as far forward as possible and twisting the throttle, and the other was ridden so hard with all WOT shifting so fast it's tire didn't even drop to the ground during the 1st-2nd torque interruption period because the time it wasn't accelerating for was so small when you're willing to just sacrifice the poor gear-box that is designed to not be able to avoid shifting it somebody merciless stomps down on it's little lever hard enough like this guy was doing because that's how pro's launch evidently when they are really trying to get a solid holeshot in. I personally tend to chop throttle a minimum to shift out of respect for the poor little dog edge/corners in a tranny even when I'm trying to shift quickly.
John in CR
100 TW
The is some fraction of a second delay on the start from a full stop with brushless motors, which is most noticeable with DD hubmotors and more pronounced with lower pole counts. Cheap controllers are probably a factor too. I believe this stems from the controller needing the motor to rotate slightly so the controller can verify the rotor position to make sure the timing is correct prior to laying on the full current. This has nothing to do with gear boxes, or a weakness or flaw in the motors, but instead it's in the control systems. For some type of racing where the launch is critical, then I have no doubt they'd come up with (or already have) some kind of different arrangement so the controller positively knows the position and can do a full and immediate start. eg Rolling up to the start line should tell the controller positively where the rotor is.
In the meantime, when there's a moto wanting to race that I think outclasses my bike, I just tell them no revving their engine, since I can't. That puts the launch advantage way over on my side.
In the meantime, when there's a moto wanting to race that I think outclasses my bike, I just tell them no revving their engine, since I can't. That puts the launch advantage way over on my side.
liveforphysics
100 TW
I know what you're talking about john, where you have to pre-load a little bit and find a spot where its good to apply full torque without just stuttering a bit. This always bothered me too.
With a sevcon and sine-cosine encoder for super precision rotor position info, you can get real full torque at zero rpm and with nearly undetectable lag of any kind when the throttle is spun to full open, something that is foolish for guys in the 150lbs range to even do on an FX because you likely won't be able to shift your weight all forward fast enough to avoid just flipping over before you've made it 10ft forward.
Good encoders and rotor position resolution is actually another requirement for doing the big slow torquey motor technique. Something like a kelly running on halls is just way to jerky and torque-rippleing from a start to ever make it mainstream in a high performance application where torque ripple actually shakes your whole body pretty aggressively from a start.
With a good encoder and good sinus bemf motor/controller match, the big motor can be an eerily smooth turning thing, like its a giant servo motor or something, which is actually what it technically I suppose, is a massive servo motor, because the controller has exact rotor position and angle and torque at all times. So much control I bet you could run it direct drive as a lathe spindle and have the resolution to precisely cut threads and do it all in one continuous clean cut, and that motor would make such a wicked lathe spindle motor for a medium sized lathe that doesn't need more than 70ft-lbs spindle torque ever. Poor lathe making industry having to rely on big complex and fragile (ive broken 2 lathe gearboxes myself from stupid mistakes) gearboxes to take a low torque density and virtually constant speed, but not perfectly constant speed by a percent or difference when you're cutting a normal light tool cut vs no-load rpm due to slip. Those things make the whole non-direct drive and servo-level-encoded lathes in the world seem pretty inefficient and fragile and needlessly loud grumbling straight cut gears that make noise in a process that could just be the cool sounds of the tool cutting through the metal be the only sound above silence, and do away entirely with your gearbox and thread pitch cutting chart with the 4-5 gear selection levers for setting the right speeds for the tool drive vs the spindle drive. Just make them both servo motors with very high fractional degree resolution and have a little smart phone processor driving a pair of nice controllers for all your threading needs with the added ability to run any thread pitch imaginable, even like 1 turn per 4ft if you wanted, or likewise thread a super tiny high thread pitch screw like M3 or something where most lathes with gearboxes max out around m4 pitch limits due to gear size limits. This setup could cut finer threads than you could see the ridges on, and cut a thread that was 20ft to the 1/4 turn or whatever if you wanted something to have that thread pitch for some strange reason like a high speed direct drive long-travel precision low-force linear actuator with still having decently precision movement.
With a sevcon and sine-cosine encoder for super precision rotor position info, you can get real full torque at zero rpm and with nearly undetectable lag of any kind when the throttle is spun to full open, something that is foolish for guys in the 150lbs range to even do on an FX because you likely won't be able to shift your weight all forward fast enough to avoid just flipping over before you've made it 10ft forward.
Good encoders and rotor position resolution is actually another requirement for doing the big slow torquey motor technique. Something like a kelly running on halls is just way to jerky and torque-rippleing from a start to ever make it mainstream in a high performance application where torque ripple actually shakes your whole body pretty aggressively from a start.
With a good encoder and good sinus bemf motor/controller match, the big motor can be an eerily smooth turning thing, like its a giant servo motor or something, which is actually what it technically I suppose, is a massive servo motor, because the controller has exact rotor position and angle and torque at all times. So much control I bet you could run it direct drive as a lathe spindle and have the resolution to precisely cut threads and do it all in one continuous clean cut, and that motor would make such a wicked lathe spindle motor for a medium sized lathe that doesn't need more than 70ft-lbs spindle torque ever. Poor lathe making industry having to rely on big complex and fragile (ive broken 2 lathe gearboxes myself from stupid mistakes) gearboxes to take a low torque density and virtually constant speed, but not perfectly constant speed by a percent or difference when you're cutting a normal light tool cut vs no-load rpm due to slip. Those things make the whole non-direct drive and servo-level-encoded lathes in the world seem pretty inefficient and fragile and needlessly loud grumbling straight cut gears that make noise in a process that could just be the cool sounds of the tool cutting through the metal be the only sound above silence, and do away entirely with your gearbox and thread pitch cutting chart with the 4-5 gear selection levers for setting the right speeds for the tool drive vs the spindle drive. Just make them both servo motors with very high fractional degree resolution and have a little smart phone processor driving a pair of nice controllers for all your threading needs with the added ability to run any thread pitch imaginable, even like 1 turn per 4ft if you wanted, or likewise thread a super tiny high thread pitch screw like M3 or something where most lathes with gearboxes max out around m4 pitch limits due to gear size limits. This setup could cut finer threads than you could see the ridges on, and cut a thread that was 20ft to the 1/4 turn or whatever if you wanted something to have that thread pitch for some strange reason like a high speed direct drive long-travel precision low-force linear actuator with still having decently precision movement.
John in CR
100 TW
I bet it sucked when the used to run a lathe off of anything other than an electric motor. 8)
I understand what I'm missing by using my primitive controllers. Lebowski has a good question though about whether sinus controllers using BEMF to sense current will work on my 6 phase motors. The 2 groups of phases are electrically separate, but they share the stator iron...different teeth but it may be magnetically coupled enough to confuse the current sensing.
Sevcon needs to stop being so greedy anyway....or Lebowski win the lottery so he can put his in mass production. 8) I just can't justify the Sevcons, especially since I need 2, and more especially since there's question about whether they'll work.
I understand what I'm missing by using my primitive controllers. Lebowski has a good question though about whether sinus controllers using BEMF to sense current will work on my 6 phase motors. The 2 groups of phases are electrically separate, but they share the stator iron...different teeth but it may be magnetically coupled enough to confuse the current sensing.
Sevcon needs to stop being so greedy anyway....or Lebowski win the lottery so he can put his in mass production. 8) I just can't justify the Sevcons, especially since I need 2, and more especially since there's question about whether they'll work.
When you are almost at shift rpm (on a mx track not pavement) you start pulling on the shift lever and any little bump in the dirt will allow enough time for the transition to the next gear with no clutch and WOT! When I learnt this was in a 6 hour 3 person team endurance race with a women on our team and we won!liveforphysics said:
I will usaly Start pulling on the shift lever at just before the desired shift RPM with wide open throttle never let off on the starts and if it doesn't shift I will Just yank the clutch quick then its in the next gear and you can do a 4 gear power wheelie while doing this. During the rest of the race I shift to the desired gear coming into corners for preparation for the exit and shift in the air of jumps for the next desired gear. Shifting in the air was the best because the bikes always shifted easier. I would get 1-2 race seasons out of a bike and the shift dogs/slots were fine. Its amazing how much abuse a MX bike can take.
motomoto
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I wanted to mention the full throttle shifting the bikes can do also. So shifting doesn't have to produce acceleration gaps that
get mentioned to dis on transmissions.
I hear Luke talk about Agni motors and how great they are, but dialing in a Sevcon correctly is beyond any of us at present. Why don't they have a program you can
run a motor through that reads the BEMF from zero to max rpm and take that data and creates and imbeds the info into the controller to produces the optimum
output for that particular motor? Life would be a dream.
get mentioned to dis on transmissions.
I hear Luke talk about Agni motors and how great they are, but dialing in a Sevcon correctly is beyond any of us at present. Why don't they have a program you can
run a motor through that reads the BEMF from zero to max rpm and take that data and creates and imbeds the info into the controller to produces the optimum
output for that particular motor? Life would be a dream.
Dauntless
100 TW
http://www.instructables.com/id/transparent-gearbox-on-a-homemade-bicycle/
Ken Taylor
100 W
liveforphysics said:
Fast ebikes are fun but 500w is still a lot in comparison to human power which is mostly less than 200w.
If you want something that will double or treble human power, handle like a bicycle and ride like a bicycle after the battery expires, weight is a critical factor. The lightest hub motors available all have complicated, but single speed, epicyclic gearboxes with the lightest at about 1.6kg according to http://www.avdweb.nl/solar-bike/hub-motor/ebike-hub-motor-selection.html#h0-1-2-hub-motor-weight . If it's possible to build a direct drive hub motor that lightweight, nobody has succeeded.
It seems hard to beat low powered geared motors. None of them offer multi-ratio gearing but they could if they offered a method to lock the carrier. http://en.wikipedia.org/wiki/Epicyclic_gearing. Maybe two speed epicyclic hub motors would be good?
Ken Taylor
100 W
Miles said:
That's interesting. You link to 4 patents. They all use epicyclic gears to get two speed hub motors by reversing the direction of motor rotation. Given they all use epicyclic gears that have been used on bicycles forever, I'd question whether they would pass a challenge on the obviousness test. Maybe its the reversal of rotation direction that is novel.
It seems like a good approach though so I wonder why you can't buy one?
The early Ford Model-T (19-teens) had a 2-speed epicyclic transmission with a reverse. Customers have been very price-sensitive, and for under 25-MPH there isn't much of a customer base that will pay extra for a 2-speed planetary hub, although I seem to remember ebikes.ca was working on one to give heavy cargo-bikes a low gear.
