Racing and efficiency

[querlenker]

From the the tests I have made I can tell you that efficiency is much influenced from the gearing and wheelspin. Longer geared and more phase current (same torque on rear wheel as with shorter gear and less phase amps), lets you save batterie - that's what Luke tried to tell you before I think. I needed some time to find the best compromise in gearing and this is still track related.
Same with slip rate. We designed a device to control rear wheel slip rate. Before I did datalogging of rear wheel speed changes on several soil. It's unbelievable which short time peaks you get when traction is lost.. My system needs a lot of more tweaking as it is very hard to make it working on different track conditions. For example you go from hard track to sand track or from dry to wet. But the few times I had perfect setups in the device, it feels like you are on rails out of the corners and it saves battery and human energy a lot. Same for suspension, it will also save battery if it's a good one. For those who are interested in numbers, a small hole in the ground where you lose traction lets your motor rev from 2000rpm to max in a few milli seconds and increases battery current for more than 100A in this period of lost traction. Your bike isn't accelerating, just wasting energy.. Also you loose another few milli seconds when you get traction again till the slip rate come down. All those little things together decide if you are competitive or not in the end!

 

[speedmd]

Motor control looks to need a feedback loop that can dial in a electronic flywheel to keep drive wheel close to ground speed (slip differential) depending on looseness (% loss or torque to break traction-wheel lateral control) of the turf. If its bites well, let the juice flow until the front wheel gets too high or is moving vertically too fast. Real challenge coming up with control for when over ground that is loose over hard pack or slick -icy conditions where you just may need to dial back power a bunch.

 

[Punx0r]

From memories of previous postings, there was one member who implemented an effective traction control system that worked well on snow. The idea of monitoring front wheel lift would seem to have the same difficulties and complexities as those discussed in the long thread about designing an wheelie control system.

 

[Vanarian]

Not the most reliable way but you can make a virtual encoder (or simply just a real one spinning at the un-motorised wheel, challenge of mechanics though, just like dynamometer but smaller - maybe a small high RPM motor? ) out of hall sensors to get the exact spinning data.

This way you get your TC data and need to adjust controller to use this data when filtering your throttle input.

Another way is a force sensor at driven wheel, because it will shortly unload when you hit a empty area so this could equal to short freewheel? But that's a nightmare to set because of G forces randomly applying. You may get less accuracy.

 

[speedmd]

From memories of previous postings, there was one member who implemented an effective traction control system that worked well on snow. The idea of monitoring front wheel lift would seem to have the same difficulties and complexities as those discussed in the long thread about designing an wheelie control system.

I don't recall the traction control you mention Punx. Would be interesting revisiting that. As far as complexities of the gyro control, yes complex, but with the new low priced chips available, I can see this having some real possibilities with a bit of R&D. If your after max acceleration and efficiency, I don't see any way to optimize it without looking at excessive front wheel lift. Without it, you will always have the rider having to get off the power when it connects hard.

 

[ohio]

If you can't win the race to the first turn, you might as well not show up.

An Alta electric bike would get smoked even though they claim 40+ hp and 34 ft/lbs of torque.
That's why you don't see it drag racing ICE bikes on Youtube. It gets smoked off the line.
They are also 50 lbs overweight compared to a 450 at 270 lbs vs 220 lbs
http://www.altamotors.co/machine/redshift-mx/

A 450 makes 30 ft/lbs of torque. A 250 makes 20 ft/lbs of torque

Hi all, Marc from Alta Motors here. Bumping this thread to answer some questions and hopefully not stick my foot in the paint bucket too hard. Happy to answer follow up questions. Let me know what you got... right up until it's over my head and I need to tap one of our real engineers (my engineering degrees do not qualify).

We've been careful to keep our claims grounded in reality, so take the published figures at face value. The Redhift dynos 40rwhp on an eddy current dyno, higher than the new japanese 250F we use as our benchmark on the dyno and at the track (and of course not just at a peak). 36ft-lbs of torque at the rotor. It comes in a hair over 250lbs (not sure where you got 270?), which is 10-15lbs heavier than the true weight of a 4 stroke with a full tank (not sure where you got 220?), and it feels a lot lighter due to lack of gyro and the mass centralization. One supercross pro we sent out without telling the weight and when asked thought it was 225. It is a holeshot machine. So far every rider we've put on it is faster on the Redshift than on a 250F, and most are faster on it than they are on a 450F, since not many folks are actually able to put more than 40hp to the ground.

We haven't been able to compete in a proper MX, but we ran it in practice at the Mammoth Amateur National and were mowing down 250F and 250Ts, granted at altitude. But still, 250Ts. We built the bike the be the fastest offroader you can buy, for real riders in real conditions. The tradeoffs for that performance are cost and range, but I really think it's only those two. If the range works for your use, you should try it out, because given the option I don't think you'd want to be on anything else. And if you would, I'd love the feedback since this won't be our last bike.

 

[querlenker]

We haven't been able to compete in a proper MX, but we ran it in practice at the Mammoth Amateur National and were mowing down 250F and 250Ts, granted at altitude..

Hi Marc,

I think you should be so fair and tell why. You are running into the same issue as we, running 30mins at this level is not possible with a "light" bike and the current battery's. Depending on Track and conditions it will be more than twice you need compared to yours and our bikes current capacity.
That's why we are racing in series where the races are shorter, or enduro with battery changes (I think there you will loose to much time with your not fast swappable battery).

Anyway really nice bikes, I would love to see it racing here and also are really interested if and when we could buy a bike in Europe?

 

[ohio]

We haven't been able to compete in a proper MX, but we ran it in practice at the Mammoth Amateur National and were mowing down 250F and 250Ts, granted at altitude..

Hi Marc,

I think you should be so fair and tell why. You are running into the same issue as we, running 30mins at this level is not possible with a "light" bike and the current battery's. Depending on Track and conditions it will be more than twice you need compared to yours and our bikes current capacity.
That's why we are racing in series where the races are shorter, or enduro with battery changes (I think there you will loose to much time with your not fast swappable battery).

Anyway really nice bikes, I would love to see it racing here and also are really interested if and when we could buy a bike in Europe?

I think I am being fair... What numbers are you assuming? A top 5 pro on a 450 puts down 13kW average at a power hog track like Glen Helen. At 35 minutes that's 7kWh of energy (at full power). Most outside that elite, especially on a 250 Are putting down quite a bit less power. So we wouldn't want to run a full season in AMA Pro Outdoor Open Class right now, but that isn't a realistic possibility today for bikes that aren't homologated and a team that can't afford a multi million dollar race program. For normal riders that but their own bikes, it should make the distance. And the question earlier was about power and the holeshot... On those items, it's not marginal like range.

That said, we are putting the bikes into lots of other formats, and sure, the shorter the better.

 

[querlenker]

Dear Marc,

sorry that was not meant so offensive as it maybe reads. I am very happy that people like you and your staff are working their ass off for the stuff they love, I love. And you did build one of the best, if not the best electric motocross / supermoto i think!

I think I am being fair... What numbers are you assuming? A top 5 pro on a 450 puts down 13kW average at a power hog track like Glen Helen. At 35 minutes that's 7kWh of energy (at full power). Most outside that elite, especially on a 250 Are putting down quite a bit less power.

From my experience the numbers are higher. I am only talking of things I messured bymyself. For example at 2 sand tracks near by, we had an average of 14kw and 14.5kw drawn from the battery. That was messured durring races and with allready limited power, so we manage to complete the ~20mins those races are(15min+2 laps). Our rider is good (wildcard in worldchampionship), better than most hobby riders, but i wont count him to top 5 AMA rides - there are worlds between.
How do you get the 13kw, did you equip a 450 with torque and rpm sensing on the sprocket or calculate from fuel consumption?

So we wouldn't want to run a full season in AMA Pro Outdoor Open Class right now, but that isn't a realistic possibility today for bikes that aren't homologated and a team that can't afford a multi million dollar race program. For normal riders that but their own bikes, it should make the distance..

Sure I understand, are you competing local / amateur races?

Regards,
Sebastian

 

[toolman2]

Hey Marc, Welcome. Its dam good to have you here, ive been following your bikes for 4 maby 5 years now always believing that YOU are the guys making the most competitive electric dirt-bikes ever by getting a bunch of what i believe are the important details, dead right. Fine work.

Was going to say, with the language barrier and all Sebastian prolly wouldn't mean it that way, but dont worry im sure you will soon be told here that your kinda wasting your time with multiple reduction stages and should be using a hub motor for better efficiency, and that the the suspension can just be 'tuned right' to sort out the unsprung weight :lol:

This thread now has quite the collection of well informed people on the subject of racing and efficiency, as your eMXM querlenker is also quite a weapon and you guys have clearly been chipping away for a while and have achieved some impressive wins.

So do you find Marc that when you have to run taller gearing (say for a track with a longer straight) that you use less battery power when accelerating from a start (at the same rate of acceleration) , and at lower speeds?
-to my mind, for best efficiency you would always want the lowest gearing (most reduction ratio) possible with these motors, that JUST gives you the top speed you need for a given track, but there has been some conflicting information here recently that i cannot make any sense of.

 

[ohio]

Dear Marc,

sorry that was not meant so offensive as it maybe reads. I am very happy that people like you and your staff are working their ass off for the stuff they love, I love. And you did build one of the best, if not the best electric motocross / supermoto i think!

From my experience the numbers are higher. I am only talking of things I messured bymyself. For example at 2 sand tracks near by, we had an average of 14kw and 14.5kw drawn from the battery. That was messured durring races and with allready limited power, so we manage to complete the ~20mins those races are(15min+2 laps). Our rider is good (wildcard in worldchampionship), better than most hobby riders, but i wont count him to top 5 AMA rides - there are worlds between.
How do you get the 13kw, did you equip a 450 with torque and rpm sensing on the sprocket or calculate from fuel consumption?

Sure I understand, are you competing local / amateur races?

Regards,
Sebastian

Ha no problem. Don't worry, after 6 years of this, my skin is pretty thick and I generally assume the best intentions anyway.

Yeah, a sand track is the worst case scenario and I would expect to see numbers like you describe. Our worst case data was from a top 10 American Pro on a built 450 at a national track, measured via torque and RPM, not fuel consumption.

Yes, we are competing in local races in a couple of formats, but actually not an MX yet - the mammoth practice was the closest. We did supermotoUSA's season closer last November and walked away with the 250 class win. Competed in the 450 class, starting on the back row because we didn't run the qualifier (weren't expecting to race 450 until we showed so well in 250), and passed everyone in the field except the pole. And that was the first time our rider had ever ridden a supermoto. Not raced, ridden. He is a mid level MX pro, but still. We did similar at their Sonoma race. I think two of our team members are actually competing in a local MX race this weekend. We also did an indoor flat track in the 250cc class, and will be doing some endurocross and hard enduro in the future.
Would love to see more of what you guys have done. Is there a thread somewhere here with more info? I checked out the website and it looks like a really solid machine. Nice work!
Best,
-Marc

 

[ohio]

Hey Marc, Welcome. Its dam good to have you here, ive been following your bikes for 4 maby 5 years now always believing that YOU are the guys making the most competitive electric dirt-bikes ever by getting a bunch of what i believe are the important details, dead right. Fine work.

Was going to say, with the language barrier and all Sebastian prolly wouldn't mean it that way, but dont worry im sure you will soon be told here that your kinda wasting your time with multiple reduction stages and should be using a hub motor for better efficiency, and that the the suspension can just be 'tuned right' to sort out the unsprung weight :lol:

This thread now has quite the collection of well informed people on the subject of racing and efficiency, as your eMXM querlenker is also quite a weapon and you guys have clearly been chipping away for a while and have achieved some impressive wins.

So do you find Marc that when you have to run taller gearing (say for a track with a longer straight) that you use less battery power when accelerating from a start (at the same rate of acceleration) , and at lower speeds?
-to my mind, for best efficiency you would always want the lowest gearing (most reduction ratio) possible with these motors, that JUST gives you the top speed you need for a given track, but there has been some conflicting information here recently that i cannot make any sense of.

Like I wrote above, no problem. Hopefully I didn't sound offended... written form is always imperfect.

Looking forward to the gear reduction and unsprung weight debates. I've been perusing and getting a feel for some of the different philosophies floating around here. Are (or most?) are valid depending on what yyour priorities are. Our CTO, Derek, is actually the best guy to weigh in, but he has his hands pretty full right now...

On that last question, it's not really a static answer because we are always tuning and retuning our motor to extract the max efficiency, and one tune may be more efficient at lower RPMs / higher torque (in which case yes to your question assuming a traction limit) and another may not. And if I answered for the current tune, it may change if we change strategies. This isn't necessarily one of those things that is answered completely with a black and white "electric motors are more efficient in X usage."

 

[querlenker]

Would love to see more of what you guys have done. Is there a thread somewhere here with more info? I checked out the website and it looks like a really solid machine. Nice work!
Best,
-Marc

Thanks!
No there is no build thread anywhere. If you have questions, feel free to ask, what I can/want to answer I will do-same like you .

 

[MarisS]

Very interesting information in this thread. Practically speaking, any idea how competitive would be MX bike if we just took some relatively recent 250-4t chases and replaced combustion engine with, let's say, motor that was used in go-kart application posted above:
GoldemMotor 10kW motor with one of their controllers?

(my kx250f have major engine blowup and I kind of started looking in converting it to EV. I know it won't be 100% competitive, but maybe for practices and as relatively easy entry into EV MX bikes, it's easiest and cheapest way)

 

[ohio]

Very interesting information in this thread. Practically speaking, any idea how competitive would be MX bike if we just took some relatively recent 250-4t chases and replaced combustion engine with, let's say, motor that was used in go-kart application posted above:
GoldemMotor 10kW motor with one of their controllers?

(my kx250f have major engine blowup and I kind of started looking in converting it to EV. I know it won't be 100% competitive, but maybe for practices and as relatively easy entry into EV MX bikes, it's easiest and cheapest way)

You can definitely build a fun and competent bike, but you'll have a hard time building something truly competitive. We started by trying to use off the shelf chassis and components, and there was just no way to get to the power, range, and weight that was needed to go head to head with a 250F and win under equal riders. I know we're not the only ones that found ourselves developing new, clean sheet parts to actually get to the performance needed to displace (pun intended) combustion.

 

[macribs]

Thx to all the experts weighing in on this thread, great to see the emmx and alta motor is here, and toolman2 has done some wild things with his joby racer. (not that he will share yet

Will follow this thread for sure. And to the racers, best of luck getting more wins and creating more craving for electric bikes.

Imagine having e-mx tracks in the inner city converting an old block of buildings into a racetrack, or an e-mx as part of park. Where people can enjoy e-motorsport without the noise. That would add tons to the urban living. As motorsport in general mixes badly with being urban today.

 

[Thud]

For lack of a better place to post this:

[youtube]CcOmKjWzF1Q[/youtube]

 

[liveforphysics]

Great rider and great run!!

 

[motomoto]

My thoughts are to drop the 70 pound battery on the ALTA and use a 13 pound 100C drag racing pack rated at 70 kW from Lonestar like Doctorbass,
but then, I would be going for the win.

 

[querlenker]

Congrats to all Alta Stuff, I had the same goose bumps as we did win our first race!

http://www.redbull.com/us/en/motorsports/offroad/stories/1331825319747/straighth-rhythm-race-recap

 

[Voltron]

Alta flat tracker pic from a buddy from the wild...I dig the asymmetrical tires.

 

[toolman2]

Yep excellent work, that is a really awesome result!

-Any better you wont get invited back again. :wink:

 

[ohio]

Thanks guys. What a crazy night. I lost my mind when Hill passed Cunningham.

 

[ohio]

You can watch the whole thing here, and for the juicy bits jump to the light blue Lites Quarterfinals for the electric action: http://www.redbull.tv/live/AP-1M77PBGTS2111/red-bull-straight-rhythm