What makes an efficient on road e-bike?

[JohnInStockie]

Hi Everyone

I think there are some questions as to what people feel would make an efficient ebike. Obviously there are many different purposes and scenarios for this, and so I would like to narrow that down to "an on-road, low maintenance, commuter specific, moderately comfortable but as efficient as possible e-bike"

For example:-

What type of frame?
What materials?
What type of forks?
What wheels?
What tyres?
What transmission (hub or derailleur)?
What drive mechanism (chain or shaft)?
What motor (must be legal)?
What battery?
What seat?

If anyone has any views on any of these or other aspects of what would be an efficient e-bike, then please make a post.

John

EDIT: I ned to say I am not looking to adapt a current spec bike (thats beyond my means), I am asking about putting one together from a colection of readily available bicycle parts for this specific purpose.

 

[flecc]

Exactly the same as you see on club or race riders bikes John, but with a centre or rear wheel mounted motor. That is, no suspension, taut frame for best direct connection of rider to road, chain drive, derailleur, slim high pressure tyres, V brakes.

That's efficient. The Tour de France is due off shortly starting in Britain and it will be on TV. Look at those bikes. You don't have to have such extremes, drop handlebars and rock hard seats, but the general structure of those bikes is the most efficient of all. You won't see any of the following on them.

Padded saddle, springing of seat stem, forks or frame, hub gears, shaft drive, all sap rider input, as do large low pressure tyres. The fat tyres also sap motor power. If the motor drives through the transmission, shaft drive and hub gears also drain a bit of motor power, hidden though by the ability to change gears down. Gimmicks like disc brakes add unnecessary weight.

Most e-bikes are inefficient, since they include some or all of the "bad" items that I've listed.

Just seen your edit. Not an easy task to get good results and I think it shouldn't be attempted unless someone has quite a lot of relevant experience, and the battery mounting will always be a problem. That said, the extra thing is that a Hall effect motor is best, and with a rigid fork bike it needs to be a back wheel type for comfort.
.

 

[JohnInStockie]

Cheers Flecc,

I understand this is not a task to be taken lightly. That is exactly why it has to be a collection of parts, rather than an adaptation, especially considering the forks and the wheels.

At the moment this is all hypothetical, I just want peoples opinions (no plans - yet).

So, from what you have said, for efficiency a road bike is the starting point, full stop. From there I am interested in moving towards the minimum adaptaions to make the bike strong enough to have a motor (rear or centre), be reliable, and to be comfortable enough to be used for everyday commuting (although this is relative to the rider).

If the frame of the bike is a road frame, the gears deraillieurs, no suspension of any kind, mtb or touring handlebars, lightweight mudguards and rack.

hub motor or not?
medium width wheels?

Any more suggestions and advice or tips/experiences?

John

 

[flecc]

I'd just typed this part two answer John, so am including it first and will respond further as necessary to your response:

To go with the Hall effect motor, an NiMh battery will have the longest life and is most suitable for longer journeys and hilly areas since it responds to high drain situations better. For short journeys and frequent charging in area's without very steep or very long hills, a Lithium based battery will be more efficient, but it will always have higher running costs due to more frequent replacement. If your situation combines those factors in an awkward way for judgement, choose the NiMh.

Going back to the question of bike efficiency, my first response was a no compromise direct answer to your request for the most efficient. Obviously you can water down that specification with some inefficient inclusions for comfort, like fatter tyres; or for convenience, like hub gears. But the more you do that, the more sense it makes to just buy a ready made product.
.

 

[flecc]

If the frame of the bike is a road frame, the gears deraillieurs, no suspension of any kind, mtb or touring handlebars, lightweight mudguards and rack.

hub motor or not?
medium width wheels?

Any more suggestions and advice or tips/experiences?

John

If you buy something of decent quality, strength shouldn't be a problem, and it's not practical to add strength to a bike after manufacture. Make sure the frame size feels comfortable for you, not too much of a stretch, and definitely not feeling cramped, too small being worse than too big where efficiency is concerned.

Handlebars are just a personal choice thing, whatever you are most comfortable with and which give you an efficient riding position. They affect the wind resistance of course, but when commuting you need to be happy as well so you must be able to live with the bike. If you feel at home and content on board, your efficiency will be helped by that anyway.

If you go for a legal rear hub type Hall effect motor, that will be the most comfortable with a rigid fork bike, and you can use a multi sprocket freewheel with that. There aren't too many of those rear motors on the market though, most tend to be front motors.

Your choice there affects the wheel width and tyre choice. If you find a suitable rear motor, you'll be able to have thinner section tyres run harder for lower rolling resistance and still feel quite comfortable. If it's a front hub motor, you'll need wider section tyres and preferably rims to match, so that you can run the front at a lower pressure to make it sufficiently comfortable. Of course that's less efficient, and moves you back towards what's on the market already.

On the creation side, it's never a matter of just bolting together a collection of purchased parts. All sorts of adaptations are necessary. For example you will often have to fabricate attachments for the battery and for the controller, plus other bits sometimes. You may have to add or devise a way of switching on and off. The battery may just be that component with no plug in device, just hard wired connections, so that might not be convenient for charging or battery swapping.

You've seen the extreme lengths I've had to go to in order to create two truly efficient bikes, one all purpose and one dedicated for performance, but in both cases I started with standard bikes, because for me the kit approach is not acceptable. Ordinary bikes are just not made for the job and have too many compromises with battery mountings and the like.

However, the Q and T bikes do contain the elements I'm advising, no suspension, taut frames/forks, thinner tyres, rear motors, so you'll find there the desirable things. Both bikes are comfortable despite no suspension, and in the T bike's case, despite very thin and high pressure tyres.
.

 

[JohnInStockie]

Thanks Flecc. Hall effect motor- is that a hub motor? Ive often wondered if anyone knows which are the most efficient motors, I mean, for a given battery capacity, which type of motor would give the best use of that available energy (Hub, Currie chain style)?

I suppose I am also wondering which has the least effect on efficiency, having fatter tyres or suspension?

What about that padded seat, does that have a significant effect compared to fat tyres?

Regarding buying a ready made product, I cant see one that is that efficient. Most have suspension somewhere, or lose gearing due to battery, or have the motor in the wrong place, or are designed to be too comfortable.

If I was to design an e-bike, Id start from the point of most efficiency, in frame and in motor choices. I may choose stronger forks, wider wheels, and a moderately padded seat. I would ignore all suspension and have touring bars, as well as the full commuter pack, and absolutely essential is a full gearing range.

The thing is I dont see a bike like that for sale anywhere. Nearly all have suspension, or hub gears, or a poor range of gears.

John

EDIT : is this an example of an efficient commuter bike (In peoples opinion)?

 

[coops]

Good questions John

Hall effect is used on brushless hub motors, but not on brushed ones.

Here's some previous info from flecc on the front vs rear hub kits aspect:

Front drive has the advantage of two wheel traction, pedals driving rear and motor at front, useful in poor road conditions. It has the disadvantage of less comfortable ride due to the high unsprung weight. Suspension forks alleviate the effects of that to some extent. Traction can also be lost on poor or slippery surfaces with a powerful motor when pulling a trailer uphill.

Rear motors have the advantage of greater comfort and better trailer control. The disadvantages are poor weight distribution, much of the weight at the rear, and often gearing limitations. For example, no hub gears possible, and derailleurs limited to using freewheel sprocket clusters. These are much more limited in range than cassette systems and are weaker as well.

Most frames/forks take either motor type without structural problems.

I think the battery fixture is the main problem, because of its weight: secure fixing, stress on the frame, weight distribution on the bike, security etc., and the other issues flecc listed like case fabrication, switches, plugs, swapping, locks for security etc.

I'm considering trying some of the newer type phosphate Li batteries, for their certain possible advantages like fast charging and tolerance of high depth of discharge, as a test, and if I can manage the technical side of building one, or find one ready-made Li is lighter, but even so, they'll probably still weigh around 2/3 of NiMH for the same capacity and they're pricier. Total weight depends what sort of realistic range you need though: a fast recharge makes a smaller, lighter, shorter range battery less inconvenient: a ~10-15 mile (non-hilly) range battery could probably be made for a more manageable weight, say around 2kg, although allowance must be made for some battery and range deterioration over time.

I'm sure there must be a "keep it simple" principle to be had somewhere, but either way, kit or mod, seems to involve some compromise? And both seem to get quite technical very quickly .

I hope thats helpful .

Stuart.

 

[prState]

Exactly the same as you see on club or race riders bikes .

I suppose you could add toe clips, straps or cages to your pedals?

I thought about this before. Even if you're sworn to not consciously contribute any effort to the upswing, …still, probably over the course of several thousand (or hundred thousand) revolutions you are both going to significantly (if inadvertently) contribute more to the bike's forward motion and probably increase your leg musculature as well.

And assuming one of the reasons people ride electric is they don't want to fool with lycra, special shoes and what not, creating the most utilitarian method is probably preferable. Which is why I've considered adding a light magnet (like rare earth) to each pedal, and the opposite pole maybe attached to the shoe. Magnets can lift many times their weight stuck together, so contribute force, but would not make you feel stuck to the bike.

Now that I sound like a whacko, I will shut up.

 

[flecc]

To John:

That Wiggle bike is quite good as a basis John. The Maxxis tyres are the only ones from China which have a reasonable rolling resistance, but in my experience they also puncture at the slightest opportunity and wear fast. So those would have to go, M/Plus as usual recommended, especially for the motorised wheel.

The brakes are Tektro, and those are the ones fitted to Torqs and Quandos with their judder problems. So a change might be necessary there, especially with a front brake on a front motor wheel. You must expect this though, most bikes will have something that will need to be changed to be suitable for the purpose.

It could be more sensible to buy a basically suitable electric bike second hand, then fit the things you want to that. That way you'd get the strength and battery mounting space solved.

To prState:

You don't sound mad at all, the magnet idea could be a good one. To get deliberate release, a sideways tilt of a foot should give enough leverage for release if the shoe fit was sound enough. I've never gone as far as toe clips on any bike at any time, but there's no doubt they give an advantage. I doubt if many electric bike riders get to that level of contribution to the power though.
.

 

[JohnInStockie]

Battery space issue

I dont understand this issue. I understand that the more weight that is lower the ground the better the weight distribution, but surely if you had even a 10kg pack and controller in a bag on the rear rack, it wouldnt make any significant difference to the weight distribution, not with my 100Kg+ on the seat above it?

 

[JohnInStockie]

It could be more sensible to buy a basically suitable electric bike second hand, then fit the things you want to that.

Flecc - Do you know of a production e-bike that would start out with the characteristics for a good basis as mentioned above, bearing in mind that most are unable to fabricate parts, and would have to be looking to replace inferior parts with more suitable ones?

John

 

[flecc]

All those with a style to suit you really John.

For example, if I were doing this and located a suitable 36 volt rear motor with freewheel thread, a second hand Torq could be a good basis, with both NiMh and Li-ion batteries possible. You'd need to use a rear wheel in the front wheel position because of the wide forks of course.

If I'd chosen a front motor, then it would be better to look out for a bike with suspension forks to tame the front motor weight that already had the right front motor width.

In all cases, make sure the battery provision matches the motor voltage of course.

Sometimes a second hand will already have a good motor but just need improving on the bike parts side.

But basically that was just another suggestion to solve the battery placement problem. With all such projects, I think you must be able to start with your own clear idea of what you want to achieve and what is needed to do that. I'm doubtful about this approach to it, and still think you could be safer with a production electric bike and where necessary just altering the odd things to improve it to your requirements. You've already done part of that with your Lafree of course, with the M/Plus tyres.
.

 

[coops]

I've considered adding a light magnet (like rare earth) to each pedal, and the opposite pole maybe attached to the shoe.

So, magnets on the souls of our shoes then? I like it! could be a good idea - might catch on! (sorry!) highly attractive (ok, I'll stop I promise ).

Nice one, prState!

Stuart.

 

[Ian]

Which is why I've considered adding a light magnet (like rare earth) to each pedal, and the opposite pole maybe attached to the shoe.

Great Idea, the only downside would be inadvertanly picking up scrap metal while walking in the shoes.

 

[flecc]

And you'd only kick a car once after getting stuck for the motorist to punch you!
.

 

[coops]

Thanks Ian, I just had another Grandad cartoon "moment" there! (picture someone walking with metal roadsigns attached to feet akin to flippers/snowshoes!)

EDIT:

And you'd only kick a car once after getting stuck for the motorist to punch you! .

Could be a handy (ok, "footy") way to "draft" off vehicles .

Ive often wondered if anyone knows which are the most efficient motors, I mean, for a given battery capacity, which type of motor would give the best use of that available energy (Hub, Currie chain style)?

I think the most efficient, but also the most pricey & not the most powerful, are transmission drive like the Twist. The rest are similar, depending on motor design & quality. I'd say probably most critical to efficiency & utility from a design perspective is a motor well-geared to the bike e.g. for a hub motor, geared for good torque at low speed for hills and the larger the wheel & higher the "geared reduction" of the motor, the more efficient for low rolling resistance, but smaller wheels gain slightly for more efficient acceleration, so choose according to intended use: commuting (& maybe most uses) may favour larger e.g. 26-28" wheels. A good hub motor geared down to ~200 rpm gives around 15mph in a 26" wheel & maximum torque at around 8mph+ for hills, for the same in a 28" wheel requires very little difference of ~185 rpm, and variation of spin speed between those two, due to battery charge state & voltage, will probably be higher than the difference from gearing .

Stuart.

 

[flecc]

I dont understand this issue. I understand that the more weight that is lower the ground the better the weight distribution, but surely if you had even a 10kg pack and controller in a bag on the rear rack, it wouldnt make any significant difference to the weight distribution, not with my 100Kg+ on the seat above it?

This is often misunderstood John. There's a crucial difference between your weight and added weight.

Your weight has an intelligent and fast reacting brain attached to it, able to drive balance correcting muscles instantaneously without your concious realisation it's happening. Therefore your weight is somewhat irrelevant to balance.

The 10 kilos on the carrier is dumb enough to get you into trouble.
.

 

[JohnInStockie]

The 10 kilos on the carrier is dumb enough to get you into trouble.

Really, it can make that much of a difference? So if I was to build a range extender battery mod like grandads, then it MUST be low mounted.

Could I build a battery only 1 battery width thick, with 20 cells on each side of the back wheel in panniers, connected in parrallel together ( I am thinkng of making a framed waterproof pannier specifically for that)?

If so then weight could be a problem, but if I could get 11Ah cells, then that would give you 22AH at 24V for 7Kg costing around £8.50 each meaning £170.00 + del - ouch!!! see here. Is this unrealistic?

John

 

[JohnInStockie]

Although I havent thought of charging....

 

[Ian]

but if I could get 11Ah cells, then that would give you 22AH at 24V for 7Kg costing around £8.50 each meaning £170.00 + del - ouch!!! see here. Is this unrealistic?

John

John, I have a couple of those cells making up the numbers in a battery pack, and they work just fine.if space permits it would be advisable to mount them in proper D cell holders though.