Middrive e bike v. car drag race

[speedyebikenoob]

Almost two years ago I made this thread: viewtopic.php?f=7&t=98656&p=1444769&hil ... n#p1444769

I answered my own question today though. I raced my e bike with my car today to see if I even had a chance at keeping up. My e bike is a middrive and runs about 4 kw peak now. The car is a 2005 Mini Cooper S with a few mods, so it should be making about 200 hp at the crank.

We did a rolling start from 5 mph so neither of us would have issues with putting the power down. I was pretty surprised the bike could hold its own and stay ahead till 25 mph, even with me having to shift through three gears, and then the car would pull away. We tried three times and it was the same result each time. Both the car and the bike were at wide open throttle.

Here's one of the runs for anyone curious: https://drive.google.com/file/d/1t3LCy1 ... sp=sharing

[Chalo]

The car has a better service interval on its transmission.

If you put 2000 hp into an otherwise stock Mini Cooper, that would be analogous to what you're doing to your bike's components.

[speedyebikenoob]

The car has a better service interval on its transmission.

If you put 2000 hp into an otherwise stock Mini Cooper, that would be analogous to what you're doing to your bike's components.

Well aware of it, but I'm okay with going thru a chain and cassette quicker for the power. It's just the compromise I have to make. I've been doing this for 900 miles and reliability has been alright. Anyways, that's unrelated. It puts a smile on my face so that's all I care about as long as it doesn't cost me too much in repairs.

[MadRhino]

900 miles is nowhere near reliability mileage test. For many of us here, 900 miles is only 2 weeks riding.

Having to shift 3 gears to 25 mph is lame. High power DD would give you much better acceleration.

[E-HP]

Having to shift 3 gears to 25 mph is lame. High power DD would give you much better acceleration.

I'm wondering, are there ways to use the Grin simulator to predict acceleration in terms of 0 to ## mph times?

Using my current battery and controller, using the custom settings, I looked at the big MXUS motors and it looks like the 4T works best for giving the greatest torque up to 30mph, before the torque curve drops off. With 3T, the torque is lower in that range, but extends further beyond that, where I don't need it (I don't ride fast).
MXUX 4504 vs 4503
https://ebikes.ca/tools/simulator.html? ... 200_0.03_V

So then, since I'm trying to not go big/wide on my next motor, I started looking at smaller motors where the torque curve doesn't drop off until 30 mph, it's easy to see how much torque I'd be trading off for motors and windings.

Here's the comparison with the Grin Fast wind hub:
https://ebikes.ca/tools/simulator.html? ... 200_0.03_V

9C 6T
https://ebikes.ca/tools/simulator.html? ... 200_0.03_V

MXUS 3005
https://ebikes.ca/tools/simulator.html? ... 200_0.03_V

Crystalyte H3540
https://ebikes.ca/tools/simulator.html? ... 200_0.03_V

Leaf 5T
https://ebikes.ca/tools/simulator.html? ... 200_0.03_V

9C RH212 Fst
https://ebikes.ca/tools/simulator.html? ... 200_0.03_V

So, looking at the smaller motors that have the best torque curves from 0-30mph, I'm concluding the RH212 Fst is likely on my upgrade list. It would be nice though, to see what kind of trade off in 0-30mph times would be for these examples.

Since I have a lot of hills, I also checked to see how much I'd need to back off on the throttle in order to not overheat on a constant 10% grade, and I looks like anything below 80% (27mph) will never overheat.
https://ebikes.ca/tools/simulator.html? ... 3&throt=80

[MadRhino]

Having to shift 3 gears to 25 mph is lame. High power DD would give you much better acceleration.

I'm wondering, are there ways to use the Grin simulator to predict acceleration in terms of 0 to ## mph times?

Using my current battery and controller, using the custom settings, I looked at the big MXUS motors and it looks like the 4T works best for giving the greatest torque up to 30mph, before the torque curve drops off. With 3T, the torque is lower in that range, but extends further beyond that, where I don't need it (I don't ride fast).
MXUX 4504 vs 4503
https://ebikes.ca/tools/simulator.html? ... 200_0.03_V

So then, since I'm trying to not go big/wide on my next motor, I started looking at smaller motors where the torque curve doesn't drop off until 30 mph, it's easy to see how much torque I'd be trading off for motors and windings.

Here's the comparison with the Grin Fast wind hub:
https://ebikes.ca/tools/simulator.html? ... 200_0.03_V

Faster kv are capable of the same (sometimes slightly better) acceleration off the line as the slower Kv of the same motor. Only faster motors are consuming more current to do so. It is normal that limiting current does result in better low speed acceleration with a slower motor.

Then, the simulator does render estimations, not reality.

Smaller motors are making slower acceleration because they have less copper mass. Basically, copper mass is the real indicator of power capability. The way this copper mass is wound does have little effect on total power capability. Gearing down does make better acceleration for a given power, until the DD power is higher than the drivetrain capability. That is why, for an example, BB drives are easy to beat with an average DD hub: Bicycle drivetrains can’t stand much power, while a 15 lbs DD hub can take 10 kw bursts. Feed a 30 lbs motor 25 kw, and you need a motorcycle drivetrain to compete with gears.

[speedyebikenoob]

900 miles is nowhere near reliability mileage test. For many of us here, 900 miles is only 2 weeks riding.

Having to shift 3 gears to 25 mph is lame. High power DD would give you much better acceleration.

To each his own I guess, I've ridden hubs and I honestly don't like the way they feel. For normal commuting it's perfect, but idk I just find these middrives a lot more fun. I've actually tried taller gearing and find it less fun.

The short gearing on this bike makes it feel like I'm going a lot faster than I really am. I know a hub motor would give me better acceleration, but I would have to throw more power at it. I just want a fun bike, doesn't need to be fast, don't need an electric motorcycle lmao. The reason I like a middrive is probably the same reason I still like having a stickshift in my car.

As for reliability, I'm basically done with upgrades on this bike so I can start using it as a daily driver, so we'll see how it holds up. I doubt I'll be doing more than 2000 miles a year though, so it would be worth it for me. Also I would really like to know who's genuinely doing 450 miles a week on their bicycle XD. That's literally how much I use my car.

[MadRhino]

Of course, we build our own ebikes to best suit our personal requirements. Each his own favorite ride.

I can ride 500+ miles in a nice sumner week. Even when the weather is sh*t, I still do 175-200 miles. One of the reasons why I prefer a DD hub build, for the low maintenance, and top speed too. I abandoned using a car long ago.

[dogman dan]

Quickest bike I ever saw won the last death race held in Tucson, years ago. It was a mid drive, but its large motor was in one gear, which would let it hit about 60 mph on the short straight sections of the track. Left hand drive, with the pedal gears intact on the right. It outclassed the gas bikes with 10 hp engines big time. Light rider helped as well.

In short, it performed much like the DD's in the race that year, but weighed less, and more importantly on a Kart track, handled better in the many tight corners than DD bikes, or Gas bikes.

[speedyebikenoob]

Of course, we build our own ebikes to best suit our personal requirements. Each his own favorite ride.

I can ride 500+ miles in a nice sumner week. Even when the weather is sh*t, I still do 175-200 miles. One of the reasons why I prefer a DD hub build, for the low maintenance, and top speed too. I abandoned using a car long ago.

Wow, that's genuinely a lot. If I ever plan on giving up on the car for normal commute and using it only for road trips (which I might very well do), maybe I'll go your route and build a dd hub bike

[speedyebikenoob]

Quickest bike I ever saw won the last death race held in Tucson, years ago. It was a mid drive, but its large motor was in one gear, which would let it hit about 60 mph on the short straight sections of the track. Left hand drive, with the pedal gears intact on the right. It outclassed the gas bikes with 10 hp engines big time. Light rider helped as well.

In short, it performed much like the DD's in the race that year, but weighed less, and more importantly on a Kart track, handled better in the many tight corners than DD bikes, or Gas bikes.

That's another reason why I like middrives, the weight distribution. I haven't had the chance to go around corners quickly with a DD bike but I'd imagine it would feel similar to how my bike felt when I had the battery over the rear wheel. Handled like crap. I have a very strong dislike for poor handling vehicles.

[MadRhino]

It is definitely easier to achieve proper suspension with a mid drive. It can cost lots of time and money to successfully mod and tune a suspension with a heavy rear wheel. Yet proper weight distribution and geometry had never been so hard to achieve for me in over a decade building with hubs. The fact is, in a place where powerful ebikes builders are many, I never met a mid drive ebike who could compete, city or mountain.

[donn]

It was a mid drive, but its large motor was in one gear, which would let it hit about 60 mph on the short straight sections of the track. Left hand drive, with the pedal gears intact on the right.

At that point, what's the difference? Is a different motor, or could it have been a DD hub driving the chain? Counting the chain drive, it's effectively a geared hub ... is that the difference? More motor than would fit inside the wheel / drop-outs?

[Grantmac]

It was a mid drive, but its large motor was in one gear, which would let it hit about 60 mph on the short straight sections of the track. Left hand drive, with the pedal gears intact on the right.

At that point, what's the difference? Is a different motor, or could it have been a DD hub driving the chain? Counting the chain drive, it's effectively a geared hub ... is that the difference? More motor than would fit inside the wheel / drop-outs?

The difference is what every hub motor proponent doesn't want to talk about and why no serious electric race bike runs a hub motor: unsprung weight.

[MadRhino]

It was a mid drive, but its large motor was in one gear, which would let it hit about 60 mph on the short straight sections of the track. Left hand drive, with the pedal gears intact on the right.

At that point, what's the difference? Is a different motor, or could it have been a DD hub driving the chain? Counting the chain drive, it's effectively a geared hub ... is that the difference? More motor than would fit inside the wheel / drop-outs?

The difference is what every hub motor proponent doesn't want to talk about and why no serious electric race bike runs a hub motor: unsprung weight.

Of course, a hub motor is not interesting for any motorcycle, racing especially. They can’t have enough power, and gears are a must. On ebikes they have a fair place, because of the relatively low top speed and lighter weight of the bikes. Ebike racing today, is mid drive domain because of power limitation rules, because the races are organized and sponsored by ebike manufacturers. Unsprung weight is a problem, but can be solved with proper geometry/suspension mods and tuning, that can make a good handling up to 70-80 mph. After all, a lot of motorcycles have a rear wheel just as heavy as an ebike motor wheel. Still, a hub build will never be a good jumping bike, or technical trail bike. On the city streets though, a powerful hub motor ebike can compete with motorcycles advantageously.

[donn]

Ebike racing today, is mid drive domain because of power limitation rules, because the races are organized and sponsored by ebike manufacturers.

I guess here you're talking about multiple gears? No doubt a great advantage, if your drive train can support the loads anyway.

But the winning bicycle above was fixed gear, for the motor. So other than the form, mechanically it was effectively a geared hub, like our MAC etc. but presumably larger.

Working in your garage, it's probably a lot easier to make a geared hub with a chain, than fabricate a MAC, so there's one advantage.

[Grantmac]

TT Zero bikes have 1 gear and NONE of them run hub motors.
Electric drag bikes don't even run hub motors.

All offroad factory built electric motorcycles use some form of mid-drive. I can't think of any that have gears except for a few E-Trials prototypes, not sure that'll make it into production or if they will just have one gear and a clutch.

You can't "solve" unsprung weight via suspension tuning. You simply accept lower performance in return for a simpler build, which is why in any real competition you'll not see a hub motor. Not at any power level.

[donn]

The unsprung weight doesn't have to be the reason why hub motors don't show up in races. From a builder's point of view, it seems to me that putting the motor inside the wheel is just a gratuitous complication. For the consumer, it's very different - that hub has already been designed and manufactured, and at most I just have to lace a rim onto it - but in a highly competitive race situation, you aren't buying a factory solution, am I right?

[E-HP]

These guys had some early success using a rear hub. There's some videos of actual races and it doesn't seem like handling was an impediment.
https://www.youtube.com/watch?v=TtGykI8tlTM

Looks like it handled better than it accelerated, so more advantage on the twisties.

https://www.youtube.com/watch?v=sY4-rYi6oXk

[MadRhino]

You can't "solve" unsprung weight via suspension tuning.

Many motorcycles have a 40 lbs rear wheel, and they are tuned to ride fine. A hub motor build can be tuned a proper suspension, but it can't be done in the configuration of a bicycle suspension design. The travel ratio need to be lower and the shock rebound control need to be improved. Then, even with a proper suspension, the unsprung mass is still a loss in reaction time because of the moment of inertia. That is a problem only on terrain that requires quick suspension reaction.

At equal power, a mid drive does make better performance than a hub, but ebike mid drives are low power as compared to the 25kw that we feed to 30 lbs hubs nowadays. The mid drives to handle that power are motorcycle domain. All powerful mid drives that I have seen built on bicycles have a very short life expectation.

[Chalo]

The most capable multi-speed test hubs for bicycles are rated 5kW (NuVinci N171). That's the outer limit of bicycle based chain drive. You wanna compare apples to apples, that's your power constraint. If you put the motor driving separately on the other side of the wheel, you have a bastard motor-bicycle that doesn't compare directly to either one.

Slow-quiet-safe-considerate-efficient are the parameters where bikes excel. That's what I like. I deal with uncountable assholes in the opposite categories every time I leave my house. I don't have to be one of them.

[Grantmac]

At real race speeds *all* terrain requires fast suspension response. On rough terrain at any speed having less unsprung mass is far more comfortable.
Most vehicle designers say that every 1 unit of unsprung mass is equal to 5-10 units sprung.
That's why serious bikers are running tubeless.

A powerful hub is around 20kw. People put that into pit bikes these days and they will walk all over some cobbled together "bicycle".

Comparing a 20kw motorcycle to a bicycle is stupid.

[serious_sam]

At real race speeds *all* terrain requires fast suspension response. On rough terrain at any speed having less unsprung mass is far more comfortable.
Most vehicle designers say that every 1 unit of unsprung mass is equal to 5-10 units sprung.
That's why serious bikers are running tubeless.
A powerful hub is around 20kw. People put that into pit bikes these days and they will walk all over some cobbled together "bicycle".
Comparing a 20kw motorcycle to a bicycle is stupid.

Agreed:

I would like something for trail riding,

I haven't ridden a surron, but I think I'd like one. It's an actual "dirtbike". Dirtbike pegs. Dirtbike seat. Dirtbike balance.

I own a pretty fast downhill bicycle frame modified with a MXUS 3K and Nucular 12F. 11kW peak. 100km/h. It is a lot of fun.

BUT, its still a bicycle, with a bicycle seat, and a big fat hub motor in the back wheel. Fast as fck in a straight line, but in my opinion, hub motor bikes handle like shit. It's just physics. The rear wheel is nearly 1/2 the weight of the bike. There's no way to fix such a massive unsprung weight in the back wheel. No amount of suspension tuning will make it better than a traditional chain drive. No matter what madrhino says, his bike might be the best handling hub bike on the planet, but still not better than most traditional drivetrain bikes. It's just not physically possible. The ratio of wheel mass is very close to the sprung mass, so their natural frequencies are very close, which means that the transmissibility of force is very high = bad handling. Put simply, when the wheel hits a bump and goes up, it forces the bike up, and there's not enough bike mass to react and push the wheel back down. You make the spring harder to push the wheel down harder, but it also has the effect of pushing the bike up harder. You just can't "tune" it out.

Hub motors have a lot of good traits though. Simple. As mentioned, usually pretty quiet. Low maintenance. Decent power available. Relatively cheap. Easy to convert. Maintain the bicycle look for legal reasons, or for the use of high quality bicycle components. Satisfaction of DIY conversion. For these reasons, many people go that route, including myself.

But back to the surron. It doesn't suffer from that massive rear wheel mass, and also has a traditional motorbike seat, so you can slide/move your weight forwards and backwards easy like on a traditional dirt bike. So balance is much better.

But we digress. This is a little off-topic, considering the OP is about a drag race...

[serious_sam]

I'm wondering, are there ways to use the Grin simulator to predict acceleration in terms of 0 to ## mph times?

You could try this:
viewtopic.php?f=3&t=109551&p=1604640#p1604105

[Chalo]

That's why serious bikers are running tubeless.

Haha. He said "serious" and "tubeless" in the same sentence.