I guess its just a matter of practicality & cost then: how easy it is to do, the quality & reliability of the result, and whether you'd have got better value buying a ready-made ebike to begin with, and carrying 1 or 2 extra batteries as you said, but at least you know the quality of the bike you start with this way (and no-one to blame except yourself if it doesn't work!).

 

From what I've seen, I think most of the parts (motor, controller, batteries) could be had for around £600 or so, add a bit more for the rest (maybe some of the kit could be got from the states cheaper? After shipping,import & VAT costs probably not much difference though?).

 

EDIT: The cost was based on Crystalyte 400 series motors; I've rejected those due to their weight, so a suitable alternative is needed to do it at that price.

 

For that though, you'd get an ebike based on your choice of frame & components, capable of ~40 miles or more per charge, at a reasonable weight (25-26kg or so, plus rear rack, battery holder & case etc.) .

 

NiMH F-cells 36-39.6V (14Ah ?) would weigh 7.5-8kg in total but give 500-550Wh, good for around 40-45 miles with moderate pedalling in mixed terrain and with more rider effort & efficient, economic use of power as much as 50-55 miles, getting close to John's 60 mile range requirement!

 

Stuart.

Edited June 25, 200718 yr by coops

http://grandads.googlepages.com/Rear2.jpg

 

I am so pleased with my modification that I have decided that when the Giant battery gives up I will add another rack on the right hand side of the bike. Here is how it will look. To save weight I may remove the 'wings' on the racks.

 

I have other ideas on how to use the future empty space when the cells are removed from the existing battery box.

Could it be a tannoy or a boom box?

 

Jeff

Thanks very much for the illustration Jeff, that helps me visualize what I'm planning...

 

I am so pleased with my modification that I have decided that when the Giant battery gives up I will add another rack on the right hand side of the bike.

 

The low positioning of the battery weight on your mod looks particularly good for stability : is that a factor in your decision to eventually add a rack on the right too, or do you want to do it to balance the weight?

 

I think the advantage of making a holder for both sides from the start is that the load can be simply carried by the rear rack by a one-piece frame "straddling" it, and easily secured to it?

 

Stuart.

The preceding discussion has been very illuminating for me. It begs the following question : bearing in mind that earlier posts have indicated the Ezee Liv has a very 'peaky' power band ( I assume this means max torque is delivered over a very narrow rev area) at what mph does the Liv motor deliver maximum torque.

Ricgard

Hi Richard, I'm not sure but I'd guess its around half of maximum rpm similar to the brushless motors; I surmised as you did that "peaky" means over a narrower range of rpm. I'm sure someone else can answer it better if thats wrong .

 

P.S. Glad you found the discussion helpful :-).

I have other ideas on how to use the future empty space when the cells are removed from the existing battery box.

 

Could it be a tannoy or a boom box?

 

So you're still thinking how to use that space? It would make a good space for a "boom box" speaker system while you ride - you'll be making another battery mod to power them and a USB charger socket for your mp3 player then? Actually, you could use them to play wildlife calls/sounds while you're out riding the tarka trail, couldn't you, and see what turns up in response? :-)

 

Stuart.

Edited June 24, 200718 yr by coops

The low positioning of the battery weight on your mod looks particularly good for stability : is that a factor in your decision to eventually add a rack on the right too, or do you want to do it to balance the weight?

Stuart.

 

Yes Stuart, I do think that the low C of G is an advantage. As for balancing the weight, with the one extra battery presently on the left, surprisingly the bike feels perfectly upright and balanced when riding.

 

When stationary the offset weight is noticeable but not a problem.

 

Placing a replacement battery on the right will look better aesthetically and will be simpler than recelling with less chance of a Big Bang if I were to accidentally short any cells.

...with the one extra battery presently on the left' date=' surprisingly the bike feels perfectly upright and balanced when riding. [/quote']

 

Yes, I thought it would be fine, since some carry a heavier ezee battery on one side in a pannier bag with no imbalance . It does look aesthetically more "balanced" over two sides, and the width looks good for encouraging other motorists to give you some serious clearance when passing .

 

Using a ready-made battery & case does sound much simpler & safer, you're right: I'll look into using two cases to make one battery divided over two panniers .

 

Stuart.

Edited June 24, 200718 yr by coops

The preceding discussion has been very illuminating for me. It begs the following question : bearing in mind that earlier posts have indicated the Ezee Liv has a very 'peaky' power band ( I assume this means max torque is delivered over a very narrow rev area) at what mph does the Liv motor deliver maximum torque.

Ricgard

 

If it's typical of this motor type Richard, it will be very marginally lower than a brushless type, but it's still related to the top speed it's geared for. Knowing how eZee's bikes are generally enabled to run at ther legal limit late in their charge, I'd estimate the Liv's maximum torque point as still being about 8 mph.

.

I was in 3 minds again where to post this; I'll put it here to try not to confuse the Q-bike thread it also relates to, since its mainly about ebike efficiency.

 

I still think there is something about hub motors, at least the rpm they mostly run at, which makes them more efficient in small wheels.

 

I'm aware that smaller wheels, e.g. 20" or less, are less efficient due to rolling friction than larger diameter ones (so low friction tyres are even more important for ease of motion), but a wheel half the weight is also twice as easy to accelerate, and the relative increase in rpm with speed is inversely proportionate to wheel diameter i.e. the smaller the wheel, the higher the rpm increase for a given change in speed.

 

So put a 260rpm hub motor in a 20" wheel (top speed 15mph) and pedal too, and it seems to me the wheel is easier in two ways to pedal into a faster spin speed, which takes a load off the motor & so increases its efficiency & economy, than for a larger wheel. The smaller diameter may also make hill climbs more efficient too?

 

In the absence of more data on the efficiency of 26" 15mph motor wheels, I don't know if it happens for other sized wheels to the same extent, nor do I know if it depends on the geared reduction ratio of the motor:wheel or if higher torque, slower spin motors also might behave similarly.

 

The news that, apparently, a 16" wheel bike achieved 48miles with motor & pedalling at an average 13.4mph on a rather modest 266Wh battery (I'm not aware of what type of terrain it was) - thats only about 5.5Wh per mile adds to my suspicion that hub motors tend to make the most efficient ebikes in small wheels. I'm aware that much depends on the particular motor used, its design & its power consumption etc. but I think the same principle may apply?

 

I would really like to understand the dynamics better, to have more information on whether there is any real efficiency gain, but intuitively I think there could be: this was one of my first impressions from flecc's Q-bike efficiency figures and I was unable to express this idea properly then, but now I think it seems at least a strong possibility. Ok, so much of the efficiency overall could just come from better pedalability of the bike (which flecc has expressed of the Q), meaning less motor use, and this could be the case in the 48 mile test too - I'm not aware how much the motor was used - but it hardly matters where the efficiency comes from, better range is better range .

 

Easier to carry extra/bigger batteries too, on a low height bike... .

 

What do you think?

 

Stuart.

Edited June 25, 200718 yr by coops

As you know Stuart, I don't agree. If the gearing is matched to the wheel size for the same speed, the effort at the tyre/road interface is identical.

 

Now add to that the incontrovertible fact that the rolling resistance of a larger diameter wheel is less than that of a smaller wheel on everything other than a mirror finish surface and the larger wheel is the more efficient. The opposite would turn the fundamentals of physics on their head.

 

The acceleration of the mass of a smaller wheel is a red herring on slow vehicles like our bikes since they spend next to no time accelerating, mostly cruising. In addition, the mass difference of a 20" wheel is very little less than a 26" wheel, especially as a percentage of the weight of a motorised wheel when the difference becomes tiny, and on our bikes the 20" wheel can often be just as heavy.

 

That's because designers commonly make the smaller wheel's rim and tyre wider to compensate for the smaller diameter in order to equalise the tyre's contact patch. The identically motored Quando and Torq are a case of this, the Quando having wide rims and 2.125" tyres, the Torq having very narrow rims and 1.75" tyres.

 

The relationship of motor rpm to road speed is the same in both cases. What happens between those two is immaterial. It's like the intermediate orbital gear wheels in a hub. It doesn't matter how many teeth they have, they still just transfer the motion.

.

Edited June 25, 200718 yr by flecc

Its a tricky one this. I can envisage both sides, and the science is confusing me.

 

If we had 2 bikes geared for the same speed, but with 20 and 28 inch wheels respectively, then obviously the 20" wheels are rotating more than the 28" wheels.

 

Does this mean that :-

 

1) The 20" wheels require less turning force to rotate once? [EDIT] But slightly more to rotate to cover the same distance as the 28"?

2) The 20" wheels are carrying more momentum due to a higher rpm when traveling at the same speed as the 28" wheels?

 

Flecc youre the only person with the bikes to qualify this and you say no. But even you said you were more than surprised at the performance of the Q bike.

 

Could there be something else that isnt being included in the equation (excluding fairy dust )?

 

John

Edited June 25, 200718 yr by JohnInStockie

What surprised me with the Quando John was the sum of the efficiency gains. Although I've loads of experience in efficiency matters, I've always chosen bikes that were at least fairly efficient in the first place. The Q bike was the first time I've taken a very inefficient bike and turned it inside out in this way, and that was where the surprise came in. Now I've done something like the same trick with the T bike complete with 28" wheels, the surprise had gone out of it, but there's still been big gains.

 

I've just this second come in from using the T, and the buzz that bike gives is something else! Same motor, and ride that and you'd be inclined to agree about wheel size.

 

But no, nothing is missing from the equation, there isn't one really, it's just a straight matter of a chain of physical relationships. As I've said several times, if small wheels had an advantage, they'd be in racing. Also, e-bike producers wouldn't have moved from them as they've done. Yes that's right, look at the development of e-bikes and the earlier models frequently had smaller wheels, 20", 22", and 24", some of those old designs still around today. But today's designers have abandoned them in favour of the more efficient larger wheel, except for folders. Even in the folding bike field, we've seen a marked growth in 20", 24" and even 26" folders, the 16" size hanging on only for portability, primarily in one bike, the Brompton. Those changes have all been for the gain in efficiency.

.

Edited June 25, 200718 yr by flecc

Ok, thanks flecc: I agree with what you say about the acceleration being a red herring; I needn't have mentioned it except to say that it would make it easier to increase the rpm, the other factor I was considering, if the wheel was lighter, which, as you say, it often isn't!

 

The relationship of motor rpm to road speed is the same in both cases. What happens between those two is immaterial. It's like the intermediate orbital gear wheels in a hub. It doesn't matter how many teeth they have' date=' they still just transfer the motion.[/quote']

 

This to me is the key to the question I raised, and what would resolve the whole thing: does the effect of pedalling a geared hub motor have the same effect on improving the energy efficiency & economy of the motor, for the same "road speed" (different rpm) increase of different sized wheels, both internally geared for the same speed? If, as flecc says, the gears just transfer the motion/rpm increase "geared up" now (because its working in reverse - from the wheel rim to the motor) then the ratio of rpm increase to "internal geared increase" is the same and the effect would be the same for both wheels (except that larger wheels will require less energy due to less rolling friction...) .

 

This last "if", the gearing up of the rpm increase to the motor via the internal gearteeth, is the only possible "hidden" factor I can see (barring fairy dust!) which, if it doesn't work smoothly e.g. some sort of friction, could reduce the efficiency of one "wheelsize & motor gearing" setup or the other.

 

If the gearing is matched to the wheel size for the same speed' date=' the effort at the tyre/road interface is identical.[/quote']

 

To John: At constant speed i.e. not accelerating the two wheels require the same force to turn, but 28" will need rather less to roll on the road due to less rolling friction. I think the "angular momentum" of the wheel depends on its weight and the speed of a point on the rim, so given the 2 wheels weigh the same and a point on the rim rotates the same speed for both (cf "on road" speed) then I think they have the same total momentum.

 

Certainly, for the same weight of wheel, the larger will actually be easier to accelerate due to the same energy required to increase the revs while having lower rolling friction losses. .

 

Hope thats useful :-).

 

Stuart

Edited June 25, 200718 yr by coops

And a further answer to that key to the question Stuart is not what you might expect.

 

There's a freewheel on the motor, and pedalling the hub is completely independent of the motor, in any instance. The rider is just pedalling the hub shell, just as on any bike.

 

The design usually takes care of the gear efficiency differences. The lower speed motors often have differently radiused orbital structures which evens out the relationship. Here's the much larger diameter Sprint motor orbital:

 

http://www.50cycles.com/images/sprinthub2.jpg

.

Edited June 25, 200718 yr by flecc

Thanks flecc, I thought there was something wrong with my reference to the gearteeth etc., of course there's a freewheel...

 

So, please tell me if I've got this right now: the amount you pedal beyond/in addition to the motor speed (and not necessarily top motor speed, but say a normal cruising motor-only speed of 10-15mph) makes no difference at all to efficiency/economy for different motors geared for the same speed but in different wheelsizes? Phew! I hope so..!

 

If yes, then I just hope no more red herrings... except with chips .

 

Stuart.

Yes, no difference Stuart, because if you can pedal the hub faster than the motor is driving, it will be spinning uselessly at maximum revs the other side of the freewheel and doing nothing. That's what happens if the throttle is kept wide open when pedalling fast downhill.

 

Surprisingly though, there's almost no power wasted. I once wanted to flatten a half charged battery to do a test, so with it in the Torq, I turned it upside down and taped the throttle wide open with the wheel spinning at an indicated 26. something mph.

 

Eight hours later the battery was nowhere near flat, the wheel still spinning just as fast, and that from half charge. So shutting off the throttle downhill probably isn't worth bothering with for all the power it might waste.

.

Ok, thanks for clearing up that one flecc.

 

I really should give up the chips too I guess....

 

To John: What do you think of the pannier battery idea for longish range trips then? Is this more in line with your original ideas? I'm suggesting it out of slight desperation of finding a suitable ebike candidate for "modifying" more than anything, but I think if a good motor & controller can be found (skip the Crystalyte 400's I think - I didn't know they were so heavy ~8kg each it seems!) its another option .

 

Stuart.

It's already on the market Stuart, and at under £1400 it's cheaper than you could build yourself.

 

It's the eZee Forte (or Forza)

 

The Velovision test in very hilly Sheffield returned 15 miles range, same as the Torq in hilly territory, and from the same 36 volt battery. But it speeds to 20 plus derestricted like the Torq and it had no trouble zooming up a 1 in 5 (20%) in Sheffield, pedalled by a vicar, so exactly what you are asking for, a Torq that climbs hills easily.

 

Problem solved!

 

The eZee approach with the F series is a US style motor restricted down to UK levels of course.

 

Well, I've been all round the houses I know :o but I'm beginning to think so, on all cost, component & performance grounds. I'd probably go for the forza of the two, uncertain about the ezee assistance factor & carrying spare battery, but I'll ask about that elsewhere .

 

Stuart.

Of the two, the Forza would be my choice too Stuart. It'd certainly have no trouble climbing hills fast with a spare battery or two on board. I'm not keen on twiddling onboard power control switches, those being on the BionX and Sparta too of course.

 

A simple throttle and a human attached is all that's needed I think.

.

Yes, as far as I can tell the ezee assistance factor works just like a "sticky" modified throttle in pedelec mode (it allows finer tuning of power level which is set by a dial; still continuously variable like the throttle), so I'd also just go for a simple throttle which I could modify to "stick" if required.

 

How to best carry a single spare battery is a question though, especially if I stick with the slightly heavier NiMH? Two spares would be more balanced I guess, but a lot of extra weight & unnecessary for many trips.

 

Do you have any suggestions flecc? A rear-rack battery carrier add-on? .

Edited June 28, 200718 yr by coops

I've always preferred lower in a pannier Stuart, and I regularly ride like that with one only. There's no balance problem even with a 5.5 kilo NiMh in a high pannier on a Torq and in traffic too.

 

The kinetic energy of the bike and wheel gyroscopic action tend to keep a bike stable regardless once rolling, you're just riding minutely tilted to one side, but it's far too small a tilt to see.

.

Thanks flecc

 

Do you need especially strong panniers for that, and inflexible ones to prevent the batteries moving around on corners etc.?

 

If I'm pushing the boat out that far, I may as well get 2 spares to use till I lose weight, then one may suffice after that, if the capacities haven't dropped . 3 lots of 36V 9Ah... thats virtually 1kWh! I like that! 3 times the range too, so at moderate speed (17-18mph) and pedalling I'd say around 70 miles .

 

Stuart.

And why not. I use ordinary soft Altura panniers, about 15 litre size, and sit the battery on the slant, base forward and leaning back, the pannier top enveloping the top of the battery and holding it at the rear of the pannier, so it's stable.

 

The first time I carried a battery on the carrier it was a Giant Twist one and this happened, scroll down slightly: busted

 

so it's not a favourite method, though I have carried eZee ones in the box that way on the odd occasion.

.

Yes, the rear carrier seems too high for the weight, not very secure either & too much risk of damage if it falls off as you say...

 

Looks like panniers are enough then (when I said rear-rack battery carrier "add-on", I did mean a pannier style one, like a sort of "double Grandad" job, not on top of the carrier ). I'm sure you've posted that info on carrying batteries before, now you've said it, so apologies if thats so, but it was a long time ago, before my ebiking days and thoughts of extra batteries for long range trips .

 

Stuart.

Edited June 27, 200718 yr by coops

interesting discussion..

 

for "road e-bike" and efficient..

 

for me, this looks very efficient (roll restistance, aerodynamic drag, light weight, motor uses the bikes gearing, ...)

 

http://www.kraeuterbutter.at/Bilder2/sonstiges/Elektro_Rennrad_1.jpeg

 

battery: 24Volt and 6,5Ah

with lipos maybe you can increase that to 36Volt at same capacity..

frame would have to be made for new..

 

the weights of ~16kg is for sure cool...

 

and for your batteries (light weight, high distance)

when you are building your packs by your own, you can get for a

37Volt 12Ah pack (including shrinkrap, including balancing/equalicing-connectors)

for around 2.4kg

 

or if you want to be lighter:

for about 1.6kg 37Volt and 8Ah

 

and the 10kg pack you mentioned:

(if money is not of big concern) i can build you a

37Volt pack with ~50Ah

of course high-powercells... (with low-power/high energie-density cells for same weight even higher Ah would be possible)

Edited June 27, 200718 yr by kraeuterbutter