Stark range video(s)

[DaveAusNor]

Easy to see why with some quick physics.

edit: those copy paste formulas came out with terrible formatting. basically 2 main forces, rolling resistance and drag. rolling resistance is linear but drag from wind is cubed with speed.

• 30 km/h (8.3 m/s): ≈ 0.40 kW
• 60 km/h (16.7 m/s): ≈ 1.74 kW
• 80 km/h (22.2 m/s): ≈ 3.62 kW

(Drag term scales with v3v^3v3; rolling term is linear in vvv.)

Power scales with speed³ → small increase in speed = big jump in energy use.

 

[AbnormalWrench]

Well that was to be expected. It's a high bike (still on knobby's?) with a small battery.
Since all E bikes are comparably efficiënt it's very easy to calculate how far you'll come when you have ridden one before.

The Zero is about 30% more efficient on the freeway than the Varg, so no, they are not all the same.

 

[Erwin P]

I don't have that much Freeway experience with the Stark since mine is not road legal. But did you run it on knobby's? It's also quite tall with the rider sitting up very straight.

 

[AbnormalWrench]

I don't have that much Freeway experience with the Stark since mine is not road legal. But did you run it on knobby's? It's also quite tall with the rider sitting up very straight.

I have a set or dirt rims and street rims, this was with the street tires. I was sitting straight up.

 

[brongle]

This is about 5 miles of light highway riding on street rims and 15/44 gearing, took basically exactly 10% battery.

 

[AbnormalWrench]

Off the freeway, I get around 6 to 7 miles per 10%, but it isn't uniform, it depends on the SoC. It tends to get worse the lower your SoC is. I am just comparing to the EV bike that I'm very familiar with as a baseline, which is a 2022 Zero FX that I have about 11K miles, which has a smaller battery but has a more efficient drive train. I guess most people just using it as a race bike won't care about this stuff, but I think it is interesting how it compares. Maybe others will find it interesting.

 

[Erwin P]

I guess the belt drive om the FX is more efficient?
It's also a much lower bike so a lott less wind to catch.

 

[vic321]

THE BIKE IS OVERWEIGHT STOCK
6kgs more than advertised.
End of story.

While having 50% more torque over the whole rpm band than any 450 ICE. End of story. You want to ride the bike, not carry it.

 

[markhamr]

Its more like 100 percent more torque

 

[Erwin P]

Depends in the gear. In first gear an ICE does about the same torque. Especially if you play with the sprockets.

 

[vic321]

Where does an ICE Bike gets 900 Nm in first gear? They are happy to achieve 1/10th of it. And you have to be in the top torque range about 5000 rpm. So you will need your clutch, which also eats up torque.

 

[markhamr]

lost me there vic

stark varg on dyno - Search Videos

www.bing.com

 

[markhamr]

I think that's about right 35ft for a 450/ 70ft for a stark
so maybe ?ft set on 60 in the app ,but its totally different .
I think electrics a bit linear on the dirt.
Cogging the motor somehow like traction control would help.
I was surprised how much it spun the rear tyre in the mx2 setting.
After the changes i have made since doing timed runs id guess,
I have made most of the time back against the 450
and over a day probably much faster.

 

[Erwin P]

Where does an ICE Bike gets 900 Nm in first gear? They are happy to achieve 1/10th of it. And you have to be in the top torque range about 5000 rpm. So you will need your clutch, which also eats up torque.

Welcome to the wonderfull world of gearing. Wich is indeed a loss on power, but actually a torque multiplier. There are multiple rear wheel torque measurements that go up and around Stark numbers. 1 of wich was a YZ450 that was also posted on this forum. If you really wanted you could surpass the rear wheel torque of the Stark by just switching final transmision ratios on about any MX bike.

I did some calculations (of wich i was able to check a few to real numbers and are pretty close) on multiple bikes. A KTM 990 for example does well over 1600Nm on the rear wheel.

However all this torque is pretty much lost when shifting up some gears.

 

[markhamr]

There are a lot more factors involved.
I would rather leave piston bike comparisons out of it and just concentrate on making this one go well.
It is a bit easy to just jump on a stark with all that power and say hell it is fast.
Reliability is a key and it doesn't matter how fast it is if it cant finish the race or even start it.
I am going to get a 1.2 for me it will help a lot for mx.
I am looking forward to riding instead of making changes all the time. ,
or work out how to get around issues.

 

[Erwin P]

So far i had little challenges with starting races. It actually has been quite reliable (1 dead battery and 1 handlebar switch that broke). However it does have a hard time finishing my 2 hour CrossCountry races. I don't think the MX 1.2 or EX would do either.
When we get into the predicted by some 8.6kWh battery it will be and that would be a huge gain for me.

The bike is still as heavy as it was so pretty sure you don't like that one either?

 

[vic321]

Welcome to the wonderfull world of gearing. Wich is indeed a loss on power, but actually a torque multiplier. There are multiple rear wheel torque measurements that go up and around Stark numbers. 1 of wich was a YZ450 that was also posted on this forum. If you really wanted you could surpass the rear wheel torque of the Stark by just switching final transmision ratios on about any MX bike.

I did some calculations (of wich i was able to check a few to real numbers and are pretty close) on multiple bikes. A KTM 990 for example does well over 1600Nm on the rear wheel.

However all this torque is pretty much lost when shifting up some gears.

Stark has nearly the same gearing as other bikes. But the ICE engine has only 1/10 of the torque at low speed. And you are not able to multiply the torque by 10 times by changing the gears. . Not even 2 times without entering physical limits. KTM 990 has 103Nm.

 

[Erwin P]

Stark has completely different gearing to other bikes. The final sprocket ratio is roughly the same, but inside the powerplant it's nothing alike.

And you can change rear wheel torque by 10x, or a 100x, or a 1000x if you can slip in enough reduction gears.

The 990 has 103Nm on the crankshaft, sure, but after that comes the primairy transmission, the gearbox and the final sprocket ratio. So that 103Nm gets multiplied a lott of times.

Even Stark has something like that on their website.
They claim 275Nm at the output shaft of the powertrain (not on the motor axle). 275 / 14*48 = 942Nm wich is really close to their claimed 938Nm, so close that it could be an rounding error in that 275Nm.
They also claim 80 Nm of torque on their motor axle. 275/80=3.4375 reduction. They don't seem to offer the number of teeth on the primairy gears, but if you were to count the number of teeth in te picture below on this post you will end up with a ratio very close to that 3.4.

As you've now learned reduction gears actually multiply torque, is it that hard to believe that 3 reductions in a row can achieve huge torque numbers?

 

[vic321]

Show me the reduction gear that will reduce at least to 2 times in a standard motorcycle when you add it to the bike. And an EV has max torque at 0rpm. An 450 Ice engine somewhere between 6000 and 8000 rpm. And the width of the max torque band is quite short. That makes more of a difference.

275Nm at the powertrain is 5 times as much as the 450 4 stroke has on the powertrain. That gearing is only possible because the BEV engine can rev up quite high. With a torque value that softly decreases with rpm from 0.

That leads to the result that the Stark has much more torque over the complete rpm range. Especially in low rpm. So 10 kg more weight does not play a role anyhow. Its more the ability of the driver to transfer the torque into traction.

 

[Erwin P]

I'm not saying E is not superior, but just the numbers are not that wildly more than a normal ICE.
And apples to apples... 275Nm is at the output shaft. That's not that hard to get on an ICE and i'm quite sure there are some that actually pull around that. If we have a good described engine i could calculate that for you.
The Varg has 80Nm at the motor, or crank so to speak, wich is more than an ICE, but not by a multitude.
Just look at any primairy gear, that will mostly do something between 3 and 7 times reduction. Then another 3-1 reduction in first gear and another 4-1 in final sprocket ratio. So yess there are quite a lott of those more than 2 times reductions.

However torque is not that important. It's power output that moves you. And like it ot not... an ICE can actually make more power at lower speeds than the Varg can. An 450 that can do 65hp can do it in every gear and thus at multiple speeds. A Varg has to wait to at least the RPM where it does make that power wich is at a speed you don't even reach on a lott of tracks.
It's funny to see at SM on the straights were only raw power matters. You see short sprints where the 450's are actually keeping up or are faster than the Stark. However they run out of breath and need to shift combined with near the end the Stark is getting over the 65hp of those bikes and actually runs away. But below say 100 km/h they shift 3 times in the straight between corners and you can cleary see them 3 times keeping up with the Stark for a moment.

Smoothness and never being outside of the powercurve is what makes the Stark feel so powerfull. Not its torque or hp number. If you were to find someone who could always keep it exactly in the power and shifting would be seemless the 450's should be faster at lower speeds.