The Great "Gearing vs Hub Motor" Debate

[xyster]

If your gearing allows you to allways stay at the top of the power curve you will accelerate/climb a hill faste

If system power is about equal, then yes. But I'm suggesting that standard bicycle chain driven systems can not reliably utilize near the 3,000 - 5,000 watts of input power that an x5 hubmotor like mine can.

Would our Tasman friend's 600 watt geared system, with him pedaling his 600 watt best, up a steep incline beat my 2,500 watt hubmotor system even without me pedaling?

I bet I'd win easily, as the bicycle speed calculator suggests.

If you agree, then at what power level would you say geebee needs to be at to win say, a one mile race from a dead stop up the same 10-15% grade?

Whatever power level that is, do you think his gears and chains would hold up over the long term at that power level?

 

[safe]

http://www.rohloff.de/en/technical/speedhub/efficiency/index.html

They claim 200 Newton Meters at the crank and 100 Newton Meters at the Hub are "normal" peak values for a bicycle. This is the torque for the 5304 Hub Motor at 72 Volts and 50% PWM Current Warping and 35 Amp controller. The units are "Newton Meters". It's actually the lowest rpm's that are the most dangerous.

 

[Lowell]

But that only applies if you don't live somewhere that the power limit is 200 watts (if you want to stay legal). Geared hubs of 200w work ok but top speed sucks.
Yes a hub motor rules for simplicity.
I can maintain ~300w for well over an hour and can sprint to over (the trainer maxed out at 500w) 500watts for several minutes, I had a bike with a 600 watt peak output B/B chain drive so I would guess 1200watt sprinting all up with peaks considerably higher and I had no drive train problems and it was all low end components.
But 3000-5000w is a lot more.
I updated my profile with where I live - Tasmania, Australia.

Has anyone heard of someone being stopped for being over the legal wattage? I just bought an X5 hub from Justin at ebikes.ca, and plan to run it to the max. If it can actually handle 5000w, you can bet I'll be trying that eventually.

The local regulations say 500 watts/32km/h, but the only time I've heard of people getting stopped is when they take the pedals off their gas scooter look-a-likes, at which point the police probably think you're on a BWS 50 without a license plate.

Maybe a good reason to have a valet switch on the bike.... :lol:

 

[D-Man]

Cool, which one did you get?

Personally, I'm not really into high speed, but would like to try a "brute" 5305. In the right size wheel and voltage, I'm sure it would burn rubber and climb any hill.

 

[Geebee]

If your gearing allows you to allways stay at the top of the power curve you will accelerate/climb a hill faste

If system power is about equal, then yes. But I'm suggesting that standard bicycle chain driven systems can not reliably utilize near the 3,000 - 5,000 watts of input power that an x5 hubmotor like mine can.

Would our Tasman friend's 600 watt geared system, with him pedaling his 600 watt best, up a steep incline beat my 2,500 watt hubmotor system even without me pedaling?

I bet I'd win easily, as the bicycle speed calculator suggests.

If you agree, then at what power level would you say geebee needs to be at to win say, a one mile race from a dead stop up the same 10-15% grade?

Whatever power level that is, do you think his gears and chains would hold up over the long term at that power level?

I do have a 500 watt direct drive hub in a 16" wheel with a bypass switch that allows it to pull 1000w peak if required and I can literally ride rings around it uphill on an unpowered bike or trike.
I feel you maybe under estimating the difference gears can make, also if you go to really steep hills ie. 25%+ I think the geared system will start to romp away.
My wild guess is that in a hilly enviroment you could reduce power by 50% and still have a better hill climber, bear in mind that a 50% power reduction will also reduce weight, this also assume that you resist the urge to use the geared drive to maintain a silly top speed thus needing more batteries.
I use both, but my enviroment is more suitable for a geared system.

 

[xyster]

If it can actually handle 5000w, you can bet I'll be trying that eventually.

In an email to me just before I bought my 5304 from him, Justin wrote the 5300 series can handle "3-5kw" continuous and 120 volts max (the crystalyte controllers handle absolutely no more than 100v). I run mine at 2.5 kw. Even after a hard ride it's hardly warmer to the touch, so 5kw seems ballpark.

I'm sure it would burn rubber and climb any hill

If provided 2kw or more, climb almost any hill -- yes. Burn rubber -- no. This motor weighs 25lbs and takes a little longer to get rolling than the much lighter 400 series...once it does though...

Here's some real-life acceleration and hill climbing stats from my chart in the photos & video section:

 

[fechter]

Actual REAL numbers! Now that's useful.
I've always wanted to measure the miles per kWhr at a given speed to get an idea of overall efficiency and compare that on several different motors / bike configurations. Like an EPA milage rating (only accurate).

 

[Lowell]

I just bought an X5 hub from Justin at ebikes.ca, and plan to run it to the max.

Cool, which one did you get?

Personally, I'm not really into high speed, but would like to try a "brute" 5305. In the right size wheel and voltage, I'm sure it would burn rubber and climb any hill.

'03. I had originally wanted the '04, but a great deal came up on the '03 which has the old style connectors, and needs a spacer machined up for a 7spd freewheel. (no problem since I have a lathe in my garage)

Before purchasing the X5, I looked at all the info I could find on the internet, and test rode several different brands locally. While gear reduction is certainly the best way to acheive peak performance, the complexity and fabrication needed for a system that will handle 3-6hp is not appealing. Having broken more than my fair share of drivetrain parts through racing cars, a broken Rohloff hub didn't really sound appealing. I would love to hear from someone who has had good results from one though in a 3rwhp+ setup though.

Another consideration is how much torque do you actually need on a bicycle wheel? Run of the mill 2-3C NiMH batteries have significant voltage drop under load, so a '72v' pack might only have 65-68v when loaded down at 35-40 amps. Put in some good cells like these:

http://www.promatchracing.com/products.php?cat=5

and even a 60s1p pack would have 73v at 35 amps! More likely would be a 60s2p or 3p though, and voltage at 100% throttle would likely be 75+. With the right controller, an 80 or 90 cell pack would probably put a smile on the face of any rider
Anyone tried more than 72v in the Crystalyte controller?

 

[Lowell]

If it can actually handle 5000w, you can bet I'll be trying that eventually.

In an email to me just before I bought my 5304 from him, Justin wrote the 5300 series can handle "3-5kw" continuous and 120 volts max (the crystalyte controllers handle absolutely no more than 100v). I run mine at 2.5 kw. Even after a hard ride it's hardly warmer to the touch, so 5kw seems ballpark.

I guess a 70 cell 10C NiMH pack would be ideal then, as it would be right at 100v straight off the charger. 70s1p, 85v at 35 amps sounds like a good start for my project.

 

[safe]

Legal Issues?

All this talk of 4-5 hp hub motors makes no sense. The law on motors is either 1 hp or 2 hp depending on your state. (or worse outside the US) So what you are all describing is completely illegal and if a cop really wanted to cite you on it they would. (but if you look dorky enough they will laugh and let you go :wink: )

Frankly if you really wanted to get the top level of performance you would get a PMG132 motor and simply use a chain drive. Pick the right sized chain (small motorycle size is fine) and then you are free to select any gearing you want. (for a fixed gear) You are then "good to go" all the way up to 15 hp. (when you pop the nipples out of your rear wheel)

Multi-speed bikes would ONLY be for those motors that were able to satisfy the LEGAL LIMIT of 1-2 hp.

It seems pretty simple to me.

The hub motor has it's place in that it's less maintenance than having a chain, but that's about it. The chain is something in the range of 95% efficient and a PMG132 can be run at around 90% efficiency. Not only that but you can get an Altrax controller and completely dial in everything for it using software.

So let's stick to the "real world" of legal bikes. (or as close as possible)

Gearing is specifically useful for very small sized motors than need to be able to spread their small torque across a wider spectrum than the fixed gear alternatives.

http://www.electricvehiclesusa.com/product_p/ki-pmg-132-d.htm

If higher power is NECESSARY then we should be thinking in POLITICAL TERMS of how we can change the laws to allow the higher horsepower. My feeling is the the laws are "okay" and all you need to do is use gears to extend what is there. If there is a change in the laws it would be to remove the speed limt, but keep the power limit. At least that's my opinion. Then it's like at the race track with Formula1, Formula2, Formula3, etc classes... as long as the motor fits the requirement you can dial in anything else to your liking. It set's limits, but also allows a degree of freedom.

Well, that's my two cents worth...

 

[xyster]

This from a person who wants to go 50mph on his bike?

So let's stick to the "real world" of legal bikes. (or as close as possible)

Let's stick to the "real world" of bikes people are regularly buying, building, and discussing. I'm hardly the only one running more than one horsepower here.

 

[knightmb]

The legal limit is quite low actually in the USA.

http://en.wikipedia.org/wiki/Electric_bicycle_laws

In the United States of America, Congress has defined a low-speed electric bicycle as any bicycle or tricycle with fully operable pedals, an electric motor not exceeding 750W of power and a top motor-powered speed not in excess of 20 miles per hour (equivalent to the Canadian 32km/h). An electric bike or trike that meets these limitations is regarded as a bicycle [8] by Public Law 107-319.[9] This Law defines electric bicycles only for the purpose of Consumer Product Safety and does not allow for their use on roads. It is a safety criteria that manufacturers should use in building electric bicycles, which helps protect manufacturers from the threat of lawsuits from within states that attempt to legislate more stringent safety requirements.

Tennessee Law on E-bikes under "Motorized Bicycle"
http://endless-sphere.com/forums/viewtopic.php?t=12

My state is more lenient though, they only consider an e-bike to be anything with pedals (that work) and a motor, but don't limit how much power and speed you achieve with it. They do limit what age though, basically if you are under 16, you have to get a motorcycle license, plus the young teenager has restrictions on what type of day they can ride. After your turn 18 years old, you are in the free, you need only a valid drivers license.

Of course you can't take the bike on any road with a speed limit above 55 MPH though (Interstate, Freeway, etc).

[I actually keep a printed copy of the TN law with me at all times just in case]

 

[safe]

There are cars that can go 140 mph and yet the speed limit is 65 mph in most places. The speed limit is 35 and 25 in residential areas. Obviously a geared bike of 1-2 hp needs to be ridden within the laws in areas "where you might get caught". But when you get that open country road (which there are plenty in the midwest) it would be nice to crank up the speed a little and go 45 mph or better.

The main thing is that if you do get pulled over the conversation will go like this:

"Hey that's quite an interesting bike you got there. I'm not sure how fast you were going but it looked like it was pretty fast. How fast can you go on that thing?"

"Well officer, I'm running a street legal one (or two) horsepower motor and so it couldn't be THAT high of a speed."

"One (or two) horsepower! Ha, ha, ha, well I can see that everything is okay you can go on your way."

"Thanks a lot officer, and have a nice day."

(I've already had this happen so it's a realistic story)

If I got pulled over on something that you could read the label: "72 Volts @ 35 Amps" then the officer could do the math and figure out that the motor was too big. (assuming he can do the math) When asked you would be forced to "LIE" which is always bad... the police don't like people who lie.

In Missouri (my state) the law goes:

1. No clutches allowed.
2. 50cc or 2 hp motors maximum.
3. Top speed 30 mph.

...so speeding would be the only thing I could get caught on, but I could argue that the gears help to climb hills, which is true.

 

[safe]

My state is more lenient though, they only consider an e-bike to be anything with pedals (that work) and a motor, but don't limit how much power and speed you achieve with it.

This goes to my point that "design follows function" and in our case the "function" is determined by the laws we are expected to follow. With those laws (quoted) YES the natural thing would be to go with a big hub motor.

My state has NO LAWS ABOUT PEDALS and so you don't need them to qualify as an electric bike.

So the result is we all end up designing our bikes to fit the unique laws that apply in our own locality.

"Absolute truth" is not important... "relative local truth" is...

When no local law exists then you have to follow the national law. When a local law exists it supercedes the national law. In most cases the local laws are more lenient than the national ones. And many local laws allow 30 mph as a baseline.

 

[Lowell]

All this talk of 4-5 hp hub motors makes no sense. The law on motors is either 1 hp or 2 hp depending on your state. (or worse outside the US) So what you are all describing is completely illegal and if a cop really wanted to cite you on it they would. (but if you look dorky enough they will laugh and let you go :wink: )

Frankly if you really wanted to get the top level of performance you would get a PMG132 motor and simply use a chain drive. Pick the right sized chain (small motorycle size is fine) and then you are free to select any gearing you want. (for a fixed gear) You are then "good to go" all the way up to 15 hp. (when you pop the nipples out of your rear wheel)

Blah blah blah (snip) ...

15hp would be great, but the problem with that is the look. An X5 hub bike doesn't look that different compared to a 500w, 40x powered bike to the average person. Put the batteries neatly in bags, and the only clue is the larger hub. My speed controller will have a nice "500W" sticker on it...

That motor would be a good match for:

http://www.e-ride.ca/Electric_Scooters/Motorino_XPh.html

The chain drive is already there, it would just need some serious beefing up. Freewheel the pedals, add another gear reduction sprocket and it would fly. The only problem is how to load that many watt hours onto the 'bike'?

 

[Lowell]

This from a person who wants to go 50mph on his bike?

So let's stick to the "real world" of legal bikes. (or as close as possible)

Let's stick to the "real world" of bikes people are regularly buying, building, and discussing. I'm hardly the only one running more than one horsepower here.

Agreed, after all this thread is "Gearing vs Hub Moter", not "legal pondering"

Now this is an interesting bike:

http://www.electricrider.com/custom/index.htm

Can probably go a lot faster with some streamlining of components plus better batteries. With that kind of power, there's no need for multi gears, much like the powerful X5 hubs.

On a side note, pellet airguns are restricted to 500 feet per second in Canada. Nobody I know actually pays attention to that, but when you post on a Canadian forum about modifications, there's always someone helpfully pointing out that it's illegal. Probably the same people that drive exactly the speed limit in the left lane holding up traffic...

 

[xyster]

From the insane-o-cycle link above, a clue to the geared chain drive reliability at high power question:

The chain appears to be the weak link in the drive system, requiring a change every 500 miles,and that's fine with me. Five minutes to replace, adjust, and I'm back in the saddle.

The motor only appears to have one, fixed gear though.

The page doesn't say,
http://www.electricrider.com/custom/index.htm

but his acceleration times, the four visible batteries and the alltrax controller w/software current limit suggest his bike is 145 amps and 48 volts for 7,000 watts total - not too much more than a 5kw x5.



calculators:
http://www.4qd.co.uk/faq/current.html
http://www.kreuzotter.de/english/espeed.htm

 

[Lowell]

I wonder what kind of run times those SLA batteries give at those kinds of current draws? Even at 1C, lead batteries have much lower capacities compared to their 20hr ratings.

I particularily like this setup:

http://www.austinev.org/evalbum/465

Not blazing speed, but excellent efficiency. 900 watts with very little extra aero drag from parts flapping in the wind. The only thing I'd add (besides more power :lol: ) is:

http://www.bikesportmichigan.com/reviews/barwars.shtml

which would give a bit more speed, and a comfortable way to rest in a tucked position.

 

[safe]

(quoting) The chain appears to be the weak link in the drive system, requiring a change every 500 miles,and that's fine with me. Five minutes to replace, adjust, and I'm back in the saddle.

Chains come in all sizes for all different types of loads. There's no reason to stick with a bicycle chain if you are running a 15 hp motor. All you need to do is <<< think >>> for a second and upgrade to a motorcycle chain. (a motorycle chain can go for 20,000 miles or more if lubricated properly)

All the electric road racers use chains... and most use the PMG132 motor and an Altrax controller...

http://electricmotorsport.com/EGPR/egprPage.htm

But this is all going "full circle" for me because I "started" this reasoning process with the electric motorcycle and 15 hp. My goal was to bring as much of the performance of the "full sized" road racer down to the level of the 750 Watt class. This is where the "magic" of gears comes into place because you can stretch the capabilities of the small motors with gears. That's the whole point... otherwise it's smarter to just step up a class to the motorcycle category. I've ridden more than 100,000 miles on motorcycles (I've done 140 mph before) and I'm not really interested in that much speed with my "old man" body. But getting a little motor to "perform" seems like a fun thing to do...


How many people own motorcycles now or have owned them in the past?

If you want "real" speed maybe you might want to get a motorcycle? (is this place filled with a bunch of motorcycle wanna be's? ...dare I say "dorks"?)

This is the kind of bike I personally find beautiful... an absolute model of efficiency even though it's still gas powered. The thinking is right, but the fuel type simply needs to change... best power to weight ratio of anything on the road...

 

[TylerDurden]

I wouldn't be suprised if plenty of folks here had/have hogs or crotchrockets... I sure did.

I gave 'em up before getting maimed or vegitated. Motorcycles aren't that dangerous, traffic and young riders are. (Ask any nerosurgeon or racer...) Here in Michigan, we call em' donorcycles.




Onward...

Good research follows from clearly indentifying the scope of the inquiry...

Maybe good framework for the question is: "what kind of performance and effiency can be achieved within legal guidelines for ebikes, given the available technology?"

And how do you define and where do you measure performance and efficiency?

Just like you can bore-out cycinders to get greater power frome a gas-motor, you can boost power from an electric motor... the trick is, what are the sacrifices?

The need for air cooling (when boosting a small motor) indicates losses in the form of heat... lots of heat = lots of watts not going to the pavement. But, you do get more performance in the form of power to the pavement, but you also drop efficiency with the heat loss.

On paper, gears are very efficient in delivering power to the road, but in the real-world, performance losses result from shifting gears (especially on hills?). CVT might be good...

On the other side, hub motor design currently seems to be applying the blunt-hammer approach: more power... despite the fact that they are turning the wheel from the worst place: the center of the wheel. A motor built out by the rim could have a smaller power rating but still deliver plenty of torque to the road with higher efficiency.


For what it's worth, you can't get much dorkier than me on a kid's electric motocross bike, but I take pride in not firing-up the ol' five cylinder just to make an in-town trip. Like you said, dorky can be an asset: a 5KW hub motor on a Barbie stingray could very well be the sleeper of day.



Don't forget the tassles...


*

 

[safe]

Don't forget the tassles...

I got a true laugh out of that one!

Very, very true. One of the best ways of avoiding trouble is with camoflage. By looking like a "dork" it diverts suspicion and keeps the law off your back. The moment your bike begins to look "really" cool and actually goes "really" fast you wake up people and become a potential threat.

Motorcycles can kill you and maim you and everything in between. It still gives me a sense of sadness whenever I think about Wayne Rainey the World Road Racing Champion during the 90's who while leading the race in the Italian Grand Prix crashed and broke his back and was paralyzed from the waist down. He was on his last season, soon to retire, on literally the last laps of his career and he lost everything. (imagine retiring a millionaire, but paralyzed)

So sad.

I'm no kid and don't want to get hurt, so I want the speeds to be "perky" but not life threatening. Top speeds of 50 mph are okay if they only occur in "ideal" situations. I've got a hill that is posted as 35 mph, but people always drive it at 50 mph. (down it) For me to stay up with traffic on this "non-freeway" I need to keep up with some decent speeds. Missouri also has no "bike lanes" (or even a shoulder to the road usually) so letting people pass you in SUV's is very scary on a bike. (I feel more scared on my regular bicycle than on my electric bike for this reason)

 

[safe]

5304 on Steroids?

Okay, more of the "theater of the absurd". How about comparing the speed of the 5304 at 72 Volts verses 96 Volts?

5304 - 72 Volts - Best top speed (low wind resistance) - 48 mph

5304 - 96 Volts - Best top speed (low wind resistance) - 63 mph

750 Watt - 36 Volts - Best top speed (low wind resistance) - 47 mph

(the last one is a 750 Watt Unite motor with 8-speed gearing for comparison purposes. The 750 Watt bike uses roughly half the power that the "big boys" use, so the range would be about double given the same battery)

 

[safe]

Base Gear for Multi-Speed Bikes?

What is the effect of the "base gear" (the gear ratio before you begin to consider the separate 8-speed gearbox) on the overall torque and top speed?

For a 750 Watt Unite motor at 36 Volts and a 40 Amp controller we get a range of low, middle and high base gear possibilities.

Imagine climbing a 40% slope!

 

[xyster]

The 750 watt motor (running at 750 watts I assume) does not have the power to propel the bike 47mph unless it's going downhill. 47mph takes (at ideal 100% efficiency) 3000 watts!
http://www.kreuzotter.de/english/espeed.htm
There's no way to get around this with gears because as you gear for more speed, you lose the torque to overcome wind resistance. Your "low wind resistance" would have to be wind on Mars, or wind at the top of Mt. Everest where the air is thinner...or you'd have to be riding a super aerodynamic bike like the lowracer option in that calculator.

 

[safe]

My road racer is approximatly equal to the "Lowracer with Streamlining Tailbox". (my frontal area is probably half of most upright bikes because the "tuck" I can get into is really, really tight and even my feet are up high like a jockey) Change that and put in 185 lbs for the rider and 100 lbs for the bike (1012 Watts peak for this 750 Watt motor) and you get the following results.

Note: All of my charts have been run with those SAME values so if you want to "keep me honest" always use them in the future.

Eventually I will do the "full fairing" thing with fiberglass and that will help alot in those last few mph's.