Power needed to eliminate need for gears....

[Ken M]

Obviously the more drive system power you have available, the fewer gears you need. This topic is probably best considered to be in the realm of hub motors only because the torque is always applied 100% to the rear wheel independent of typical bike gearing via chain rings. When you run simulations for a cruise speed on flat surfaces in the 25-30mph range it's pretty clear that rider input is a small fraction of the power required to sustain those speeds (I'm assuming that most riders would have a difficult time of sustaining 300W power). This is mostly the result of air resistance. If a bike was geared for a reasonable cadence at 28mph (say a 52T front and 14T of 16T rear fixie freewheel) I think a 2000W Direct Drive Hub motor drive system would eliminate the need for any additional gearing and probably a 1000-1500W gear hub motor would provide the same benefit. This is not exactly exotic technology but clearly it's not compliant with current regulations unless you go to an "off-road" or "race" mode as some ebike companies have done and just ride ?illegally?

I believe this is a power and speed capability that is compelling for ebikes to be truly "transportation" capable while being compellingly simple.

I just wondering how many ebikers would prefer an urban mobility ebike with that capability.

Note: Mid drives suffer significant mechanical efficiency losses at high speeds thru the drive system so they really are not an effective high speed solution unless they had a reverse chain ring configuration (small front large rear and spun the crank axle very fast like emopeds so that have mid-drive motors (ie not hub motors as many emopeds have).

 

[AHicks]

I think anyone that has an interest in riding an e-bike at sustained speed of 20+mph is very likely a commuter. As a recreational only rider, and an old fart at that, I can say with no reservation I personally have no interest in those kind of speeds. That's not to say though, that I don't appreciate the larger DD motors (1000-1500w) for their ability to get the bike moving with a proper sense of urgency available. Current experience limited to DD, but looking into the potential of 1000+w gear drive rear hub. At the speeds I'm interested in, the gear driven system would likely be working at peak efficiency. Understood, at 20mph+, they drop off as compared to the DD hubs.

 

[MarkF]

I would like to see a 28 mph bike with 2000 watts of power. That way you have the energy to get going when you need it and the option to dial it down when you don't. Just because a bike has a lot of power doesn't mean it has to go 40+ mph. Although for me, I like the 40+ option

 

[Ken M]

I would like to see a 28 mph bike with 2000 watts of power. That way you have the energy to get going when you need it and the option to dial it down when you don't. Just because a bike has a lot of power doesn't mean it has to go 40+ mph. Although for me, I like the 40+ option

To keep a rider engaged to 40mph the cadence would be around 100rpm on a bike with 27.5 / 650B rims with 2.4" wide tires with a 66T front sprocket and 14T rear. That would be a really bad gear ratio to ride if you ever lost battery power.

I think keeping the rider engaged in the assist delivery past say 28-32mph requires pretty exotic chain rings if you want a fixie rear with 14T (that seems to be the smallest standard fixie rear ... probably to keep wear reduced and chain reliability up).

2000W is pretty much the sweet spot for a direct drive hub motor bike that could achieve enough assist to sustain a speed in the mid 30mph.

 

[JRA]

Unless you go MoPed class you won't be able to go over 1000w legally but getting the DOT involved is a whole nother thing. Actually the way their regs read you need to have an automatic transmission or as you suggest a one speed. I think it would make a good commuter though, that is why I liked that Bultaco Brinco as it looked like it could sustain the demands of high speed riding. I noticed it had a Schlumph High Speed Drive so it also had high enough gearing to support pedaling at speed. Which I admit is not the objective of all potential users.

 

[Mr. Coffee]

What you are describing stops being an electric pedal-assist bicycle and becomes something else.

Due to wind drag, efficiency of an electric bicycle is going to dramatically drop off past 20mph, and you'll probably use twice the Wh per mile at 30mph that you used at 20mph. So your proposed design approach implies much larger batteries as well.

You are also constraining yourself grossly by ignoring internally geared hubs such as a Rohloff or Pinion.

 

[Cowlitz]

Vespas and other small motorcycles are available already.

 

[AHicks]

I would like to see a 28 mph bike with 2000 watts of power. That way you have the energy to get going when you need it and the option to dial it down when you don't. Just because a bike has a lot of power doesn't mean it has to go 40+ mph. Although for me, I like the 40+ option

You can do that now with the current 1000-1500w DD kits. They'll both do 30+ pretty easily. You just aren't going to do it long. They are using a LOT of power at those speeds, and unless you plan on multiple large capacity batteries, you're going to be range restricted. That said, they do tame down easily, and aren't that bad on power consumption at all.

 

[AHicks]

Vespas and other small motorcycles are available already.

Holler when you see electric versions of those on the market. I think something like that would be pretty interesting, as long as there was a reasonable range available!

 

[Jerry LM]

First I am NO expert just a rider but I regularly travel over 20 mph around 23 mph for long distance with Very Little input from my legs, in other words pressure on the pedals, very easy steady cadence. My bike is 750W and 110NM torque and I usually ride in PA level 3, I am 76 so not in the shape; of a younger rider and this pace is easy for me. When I encounter hills then it drops off of course and I use my electronic shifting to dial down just a bit, it works instantly so quite easy. In fact it shifts so easy a very light touch is needed or you go to far, takes a bit of getting used to. If I am not mistaking I think mine is rated 1000 W max output. I don't know all the math involved in gear ratios etc. but find the bike easy going even on windy days but my speed drops into a head wind on the coast here and I just slow down and take it easy.

 

[Ken M]

I've noticed some comments that anything over a 750W motor is no longer an ebike. There is no legitimate way to specify a motor with a static power rating like that so in reality the federal limit is ambiguous (why do you think so many ebike drive systems exceed 750W operationally.

If you ever want to confuse a legislator / lawyer ask this simple question:

If actual speed limits or max speed a bike can achieve can’t be argued as the basis for the assist limit, what is it’s basis?

This is the obvious question given that bike speed is not limited by the assist speed and speed limits are utilized to regulate the speed of other transportation products. I think it's crystal clear that we need human scale transportation more than we need brain-dead assist limits (that originated in Europe and favor mid drive systems) that can't be justified even by the law-makers that pushed them. I frequently ride at 35mph on my traditional road bike (not for any great distance but certainly when even a slight down hill grade is present) so it seems rational that assist speeds into the mid-30s makes sense. This does not mean everyone riding a bike capable of that speed is going to riding recklessly (bothers me that so many resort to the Pandora's Box argument on assist speeds).

 

[Alaskan]

Even the most powerful motorcycles have more than one gear. Sometimes simplicity is an impediment to functionality or in the inverse, "complications" can enhance usefulness .

 

[Mr. Coffee]

I guess I have a hard time understanding what you are trying to accomplish here.

Gears are in no way difficult to use. Most fifth and sixth graders who ride bicycles have no trouble mastering them.

Also, drivetrain efficiency losses are going to be noise compared to drag losses. Pro bicycle racers go very fast, and they are obsessed to a hilarious degree with aerodynamics, yet largely ignore drivetrain losses. From a mechanical standpoint there is very little difference between derailleurs and sprockets on racing bikes and on any bike you might buy at a bike shop. Yes, they are lighter in weight, use fancy materials, and are insanely expensive, but you can recognize all the parts and you use them exactly the same way you'd use the derailleurs on a $99 bike from Wal-Mart.

 

[Ken M]

Even the most powerful motorcycles have more than one gear. Sometimes simplicity is an impediment to functionality or in the inverse, "complications" can enhance usefulness .

Don't confuse gas powered motorcycles with electric mopeds and motorcycles that almost always have only one speed. I have two different emopeds and both are one speed (one is a NIU emoped with a Bosch direct drive hub motor in the rear wheel). I'm pretty sure that most electric cars have only one gear.

 

[Ken M]

I guess I have a hard time understanding what you are trying to accomplish here.

Gears are in no way difficult to use. Most fifth and sixth graders who ride bicycles have no trouble mastering them.

Also, drivetrain efficiency losses are going to be noise compared to drag losses. Pro bicycle racers go very fast, and they are obsessed to a hilarious degree with aerodynamics, yet largely ignore drivetrain losses. From a mechanical standpoint there is very little difference between derailleurs and sprockets on racing bikes and on any bike you might buy at a bike shop. Yes, they are lighter in weight, use fancy materials, and are insanely expensive, but you can recognize all the parts and you use them exactly the same way you'd use the derailleurs on a $99 bike from Wal-Mart.

I tried to explain the reason for the post. Aerodynamic looses become very significant when riding over 20mph. At 30mph they are so great that human power alone can not sustain that speed (unless riding a very aerodynamic bike). It takes about 1000W to sustain 30mph on an upright bike for a rider that weighs about 200lbs so in reality to sustain that speed the drive system on an ebike will have to provide the majority of the power. That being the case, it's seems that gearing of the bike becomes less important thru the entire speed range of a bike because many riders riding fixies do fine without motors or gears.

It's mainly about simplifying a powerful ebike.

 

[Feliz]

Doesn't aerodynamic resistance double with the square of the speed?

 

[Alaskan]

A single-speed, 2 wheeled vehicle that can maintain 30 mph is well beyond a human powered bike. I realize that the definition of "bicycle" is being expanded these days but surely such a ride would be at the bleeding edge.

 

[Deleted member 4210]

Typical rider MAYBE does 250 watts at a regular cadence, and if he/she is not in shape (i.e. not an avid cyclist), that wont be for very many miles.

If you want to go 30 mph, generally people buy a electric powered moped or scooter.
( below link is what I mean by moped or scooter)
https://www.genze.com/e-scooters/#20s

In otherwords, since a rider is barely providing maybe an 1/8th of the total power, whats the point of even having something with pedals on it, when you have 2000 watts ?

Your leg power is barely even part of the equation.

Maybe go Buy a SurRon, and you can pretend you are pedaling, and go way faster than even 30. lol.

 

[JRA]

Knock yourself out here: https://endless-sphere.com/forums/viewtopic.php?f=3&t=94649

 

[Jelester]

To keep a rider engaged to 40mph the cadence would be around 100rpm on a bike with 27.5 / 650B rims with 2.4" wide tires with a 66T front sprocket and 14T rear. That would be a really bad gear ratio to ride if you ever lost battery power.

I think keeping the rider engaged in the assist delivery past say 28-32mph requires pretty exotic chain rings if you want a fixie rear with 14T (that seems to be the smallest standard fixie rear ... probably to keep wear reduced and chain reliability up).

2000W is pretty much the sweet spot for a direct drive hub motor bike that could achieve enough assist to sustain a speed in the mid 30mph.

I like the speed thing but since I am too old I would not want to ride that fast. I am afraid with the increased speed that Ebikes will be banned from some of the great trails.