The Great "Gearing vs Hub Motor" Debate

[Lowell]

I say run what you got, street racing style.

Sounds good to me! But Safe's trying to make a NEDRA event out of a little friendly competition to promote the publication of real-world empirical data after a good debate replete with reference to theoretical stats & graphs.

He's got the 100 amp controller. I think Safe just doesn't want to race because he's afraid he won't be able to shift fast enough during short acceleration tests, his all-powerful gears becoming an embarrassing hindrance.

http://www.skoolshooting.com/text_ricer.htm

Gears are no fun unless you can full throttle upshift like cars and motorcycles. (with ignition cut of course)

 

[safe]

He's got the 100 amp controller.

But it's for a 48 Volt system.

I've got THREE very large (28 lbs each) SLA batteries that cannot be converted to anything 48 Volt very easily. With the cell based packs you can just rewire things to make changes. What would just suggest, that I buy and add another 28 lb battery just for the test? No way.

On my future bikes I'll be able to run 100 amps at 48 Volts and then we can do some kind of comparision, but for now I'm limited to the 750 Watt 36 Volt @ 40 amps configuration which peaks at 1012 Watts. The new bike will reach 1772 Watts... a 57% increase in power.

 

[safe]

Here's an idea...

Rather than the 660 foot race you are suggesting (1/8 mile) I'd say that since most of us have odometers that can easily measure a mile or a kilometer that we use that as our measuring stick. That gives the geared bikes some advantage on the start (for the first 50 feet or so) and then when the power comes on it allows the aerodynamics of a bike like mine to demonstrate how important that is. You end up with a mix of acceleration and top speed... the perfect "real world" test of the mix that it would normally encounter in stop and go riding.

So how about either 1 mile or 1 km?

5280 feet or 3280 feet?

I like a mile because then I don't have to do any math or change my odometer settings... you just read off of the numbers directly.

The main thing is a STANDING START... so you stop, reset the odometer to zero, then run the mile and jam on the brakes the moment you finish and read what you get... that will be "close enough". Hills are okay as long as you start and stop at roughly the same altitude.

 

[Matt Gruber]

how about 1 mile including buying and carrying a weeks worth of groceries? that's real world.

 

[safe]

how about 1 mile with a weeks worth of groceries? that's real world.

Never on my bike... mine is for "Sport" only... if I'm getting groceries I drive my "truck" which is one of those "wimpy" japanese light trucks, not a "macho" American "hemi', but it gets good mileage.

Groceries would best be done with a bike trailer... (which you can remove and then get back to "Sport" afterwards)

 

[Lowell]

Timing over a properly measured mile or kilometer would be better than using an odometer, but you can pick any race you want. 7000m would work too, as there is a 7km stretch of flat road near my house with no intersections.

http://www.texasmile.com/

 

[safe]

Timing over a properly measured mile or kilometer would be better than using an odometer, but you can pick any race you want. 7000m would work too, as there is a 7km stretch of flat road near my house with no intersections.

http://www.texasmile.com/

7000m is 4.3 miles.

That will favor aerodynamics over acceleration so much that the start won't matter much.

Are we doing a "drag race" (acceleration only) or an "overall performance" race?

For "pure" acceleration a 100 yard dash would work... even 50 ft would show how fast you can "jump" off the line... How about you just take a tape measure and measure out 50 feet and then we see how many seconds it takes us to cover that? That's a "real world" quick start scenario and it would not really give you much time for shifting much... maybe one shift if that... this would show a comparision of "first gear" on a low powered geared bike verses a "hub motor" with massive power. (which I think is at the root of our questioning)

This sounds "fair".... 50 ft... (and that way we are not dependent on anything but a stopwatch... if your meter on your bike is wrong you don't end up reporting "fantasy numbers")

 

[TylerDurden]

Groceries would best be done with a bike trailer... (which you can remove and then get back to "Sport" afterwards)

Park the gasser babe, the trailer is the way to go to the store.

I use baskets for most stuff, but I have a trailer for bulky items.

You want to talk about getting attention, the good kind? People like to see ebikes in everyday use: getting groceries, going to the bank, hardware store, etc. The only thing I don't fetch with the bike is building material. And gas of course.

You wanna talk about how gears are an asset? Pull that trailer with a cord of firewood or a square of shingles!!

 

[safe]

You wanna talk about how gears are an asset? Pull that trailer with a cord of firewood or a square of shingles!!

Boy that's for sure.

A "really practical" machine that towed a trailer would do well to have low gears to get up the hills more easiliy. Another good argument for gears. (that's also a case where the hub motor can't as easily "lift" it's way out of the bad part of the powerband like when it's running light)

Try to carry too much load with too low of gears and you run the risk of too much torque and destroying your internal hub gears though... so you need to stay away from getting too "greedy" with those ultra low gears... (there are limits to everything)

 

[fechter]

Yes, it seems like gears would be a big advantage for hauling heavy loads, especially if there are hills involved.

You could load up the trailer with batteries and ride till you butt hurts.

 

[safe]

Yes, it seems like gears would be a big advantage for hauling heavy loads, especially if there are hills involved.

You could load up the trailer with batteries....

Anyone ever run the numbers on how far you might be able to travel with 100 lbs of Lithium cells in a trailer?

200 miles?

500 miles?

 

[xyster]

There's no flat mile nearby without a ton of traffic on it. Safe just doesn't want to race a short distance because he knows he can't shift fast enough to keep up.

But it's for a 48 Volt system.

You already used your 100 amp controller with your bike at 36v, right? Didn't you tell us how much more powerful it was, but that it ate your battery power too fast so you went back to the original controller?

 

[safe]

Result

Lithium pack would cost $4,500.

It would weigh 104 lbs.

For a 750 Watt motor overvolted to 48 volts and running at a low controller limit of 15 amps (to conserve fuel) would go a minimum of:

445 miles.

Actual range could be beyond 500 miles..

 

[xyster]

Anyone ever run the numbers on how far you might be able to travel with 100 lbs of Lithium cells in a trailer?

100lbs of lithium would be about 1000 of my 46 gram 2.2ah li-ion cells.

A 20S50P pack of these would be 110AH. Ridden conservatively 15-20mph this would go about 300 miles.

I have 30 pounds of cells on board right now (300 X .046grams = 13.8kg = 30.3lbs).

 

[safe]

There's no flat mile nearby without a ton of traffic on it. Safe just doesn't want to race a short distance because he knows he can't shift fast enough to keep up.

My "issue" was with calibration of the measurements.

One mile is easy to do with a meter because you can get a fairly accurate measurement. 1/8 mile is so short that the reading will not be reliable and by the time I slowed to a stop (to actually read the meter) the numbers would be all screwed up.

50 feet I can actually measure with a tape measure and then just use a stop watch.

I think across the entire spectrum my bike would do quite well.

In a real "race" I'd blow most bikes away simply because I'm a fast rider on a bike that can handle speed and corners well. I can carry speeds leaned over in a turn that a regular bike would wobble and probably place him on the ground in a crash. I can literally CARRY 25 mph WHILE LEANING through tight corners! That would scare the heck out of most bike riders. And on the high speed corners where I'm leaned over at 35 mph that would make a huge different in lap times. Handling would be the primary issue in a real race situation.

You have to remember that I have over 100,000 miles on fast motorcycles in my past so my riding skills combined with the bike will blow most people away who don't have similiar backgrounds.

 

[Lowell]

There's no flat mile nearby without a ton of traffic on it. Safe just doesn't want to race a short distance because he knows he can't shift fast enough to keep up.

My "issue" was with calibration of the measurements.

One mile is easy to do with a meter because you can get a fairly accurate measurement. 1/8 mile is so short that the reading will not be reliable and by the time I slowed to a stop (to actually read the meter) the numbers would be all screwed up.

50 feet I can actually measure with a tape measure and then just use a stop watch.

I think across the entire spectrum my bike would do quite well.

In a real "race" I'd blow most bikes away simply because I'm a fast rider on a bike that can handle speed and corners well. I can carry speeds leaned over in a turn that a regular bike would wobble and probably place him on the ground in a crash. I can literally CARRY 25 mph WHILE LEANING through tight corners! That would scare the heck out of most bike riders. And on the high speed corners where I'm leaned over at 35 mph that would make a huge different in lap times. Handling would be the primary issue in a real race situation.

You have to remember that I have over 100,000 miles on fast motorcycles in my past so my riding skills combined with the bike will blow most people away who don't have similiar backgrounds.

Let's stick to things that can actually be measured and replicated by most of the users. Video with a visible stopwatch in the frame sounds like a good way to keep track of time/distance/speed.

 

[xyster]

Let's stick to things that can actually be measured and replicated by most of the users. Video with a visible stopwatch in the frame sounds like a good way to keep track of time/distance/speed.

Yup. Time-to-speed is easy, accurate, and easily video'd.
0-10
0-20
0-30
0-40
0-50
0-60
0-70 kph

takes just one run audibly shouting out the speeds as they show up on the speedometer, then using the video recording to derive the times.

 

[Lowell]

I was thinking video the DrainBrain with a stop watch taped to side. Then it can be looked at frame by frame to determine time deltas.

 

[safe]

I don't have a video camera. My brother had one for years and it finally broke last year. So for now the video idea is beyond my capabilities.

I do have a tape measure and I just measured out 100 ft and did a few runs with a stopwatch and managed under 5 seconds. The funny thing is that 100 ft is actually PAST the shift point of first gear on my bike, so I used second gear for the test, but it was my "low gear" front sproket so it's still low. My "shifting" hand was holding the stopwatch so I couldn't shift anyway.

So just go out and try that... 100 ft in less than 5 seconds. (three runs)

For a bike that weighs 140 lbs with Lead Acid batteries that's far better performance that one would expect... (it's still 40 degrees out there right now, so I'll wait until later for the one mile test)

 

[xyster]

I was thinking video the DrainBrain with a stop watch taped to side. Then it can be looked at frame by frame to determine time deltas.

It's easy for me because my speedo/odo, voltmeter and ammeter all sit within the camera's frame while it's recording video. I posted a few vids like this on the other forums a few months ago.

 

[Lowell]

http://reviews.cnet.com/Canon_ZR100/4505-6500_7-31263285.html?tag=lst

I have a ZR40, and it's been nothing but reliable. I've used it underneath vehicles to anaylze suspension motion and tire shake, taped it to my helmet to film races, and my friends took it on the Open Track Challenge in 2004 in a Lancer EVO8 that I helped prepare. http://www.opentrackchallenge.com/
(the car got written off at one of the tracks unfortunately)
I keep waiting for it to die so I can buy newer technology, but it just won't quit.

 

[TylerDurden]

I have a ZR40, and it's been nothing but reliable... I keep waiting for it to die so I can buy newer technology, but it just won't quit.

I have the ZR60... worked great until I loaned it to a pal.

I do have a tape measure and I just measured out 100 ft and did a few runs with a stopwatch and managed under 5 seconds. The funny thing is that 100 ft is actually PAST the shift point of first gear on my bike, so I used second gear for the test, but it was my "low gear" front sproket so it's still low. My "shifting" hand was holding the stopwatch so I couldn't shift anyway.

You could measure out 800 feet: then you can get through yer gears, then hit yer stopwatch

 

[Matt Gruber]

tried my mbike 100'....7 seconds
WITHOUT bypass
it's lots quicker on bypass, but i doubt it would beat 5 seconds.

 

[xyster]

I have a Canon S2 IS camera that shoots very nice 30fps VGA video. For recording ebike video I just where it around my neck.

I'm going to repost to ES one of my older videos of an acceleration test. It'll take a few hours to transcode it to a flash format so that everyone can see it without the quicktime/wmv hassles. I have a mac, so wmv playback sucks much worse than it already sucks on a PC. And I understand most PC users do not have quicktime installed, so for posting I either transcode the camera's mpeg movie to flash, or to both quicktime and wmv.

 

[safe]

You could measure out 800 feet: then you can get through yer gears, then hit yer stopwatch

That's a little more with the tape measure than I want to do.

I'll do a one mile test. That way I can go through the gears and get a reading off my meter. At one mile the short distance that it takes to brake to a stop would not screw up things that much. We're just trying to get a "ballpark" figure to see if all the calculations are indeed correct.

I'm guessing about 30-35 mph average for the one mile... the first 1/4 mile will be getting up to speed and the rest just getting into a tight tuck...