Electric bike conversion kits - more advice please re drag, noise, robustness, etc.

schoe · Jun 6, 2011

From what you say it may be worth waiting for the cytronex kit due out later this year.

eddieo · Jun 6, 2011

As long as both bikes share same wheel diameter and the same brakes the new wisper DaaHub kit may fit the bill? I wonder if you could order an extra battery docking station (fits within triangle) to fit both bikes..... then it would be a 5 minute job to swap wheel and battery from one bike to the other.....

wisper uses Dapush motor with reportedly little drag......I have demo'd this set up on an Wisper Alpino and it is indeed powerful. I am getting one of the first DaaHub kits fitted today to a Specalised Crosstrail Ltd Disk so looking forward to it on a much lighter bike! It should by all accounts fly.........

Cyclezee · Jun 6, 2011

Oiseaux said:
Because I have a tourer and an off road bike I am beginning to consider the kit route again as my entry into electric bikes.

Ease of swapping between bikes
Minimal drag with motor off
Minimal noise
Minimal weight
Battery arrangement
Ability to withstand off road use

I have also read that the Ezee kit is very good and this would also be on my shortlist if I could be assured as to ease of assembly. I realise that like the MFI wall cabinet, the first time will take five hours but the second time hopefully will take five minutes !!

I would welcome any advice from individuals or suppliers especially as to the feasibility of swapping between bikes, advisability of using kits off road, as well as any other recommendations for kits to be considered.

Oiseaux

Hi Oiseaux,

Firstly, for some reason I am not able to view the images of your bikes, but I would guess that your tourer has 700c wheels and the off road bike 26".

If that is the case, swapping a kit is not going to work because of the different wheel sizes.

Obviously, I am going to recommend an eZee conversion kit, but not just because I can supply them, but because of the number of variations that are available, front or rear motor and different wheel sizes, a choice of batteries, proven reliability and performance and value for money.

My suggestion would be to buy a separate kit for each bike, and as you will only be using one bike at a time you would only need one battery.
The battery is large percentage of the cost of a kit, so there is a considerable saving to be made. The wear and tear on each would be reduced.

If I can be of assistance please do not hesitate to contact me.

Andrew harvey · Jun 6, 2011

Some Bafang kits come without the motor freewheel. With a freewheel they offer no more resistance than the Dahub motor.
I've used Bafang motors for about 7 years now, I have found drag on two examples.
One was a motor with no internal freewheel the other was a very powerfull older model the Hill King. The Hill King motor only realy offered drag when the you where trying to pedal faster than the motor would normally run, noticable when the battery was running down, but not so when it was fully charged, it did have a top speed of well over 20 mph.
The lower geared Bafang motors, geared for 18 max or less tend to have little drag. They will hum a little at low speeds and high power settings but it is not noticable when you have a little wind noise.
I am now using an Anada motor, Q100, very simalar to the SWXH motors nice little motors smooth power not as much torque as the Ezee but I'm running it on a 12 amp controller, with the 20 amp controller you get a much mor defined kick when you power up but at the expense of range and battery life.
I'm running this on a recumbent trike, which as everyone who hasn't tried one will tell you, aren't good on hills. Even at 12 amps it climbs better than I can, my handle bar controller has 6 power settings coupled to the pedal sensor. Even in the lowest setting, were the motor assists to about 5 mph I can climb better than 1 in 10 hills without sweat, I do this if I'm out for a long distance run, I like to do most of the work myself and use the motor to extend my personnal range. I have made 80 mile trips on a tiny little 8AH pack, although I was a barely able to walk to the bar for 20 miunutes after.

If you go go a kit from someone like BMS Battery they will sell you to sets of control setup so it's just a case of swapping the motor wheels. Except of course tourers will generally use 700 wheels not 26", check the sizes before ordering, you might need two motors/wheels. I would just buy one to start and see how you find it.

Cyclezee · Jun 6, 2011

Oiseaux said:
Hopefully pics are now showing and I have added wheel sizes of 700x38c for the tourer, and 700x35c for the hybrid. I would also add that I am a nine stone weakling !

John, again food for thought. If this works out my friend wants a kit as well, but I'm the guinea pig!! I take the point about only using one battery, is it possible to have a battery that is mounted in the triangle ?

Oiseaux

Hi again Oiseaux,

So both bikes have the same size wheels. The Lapierre being a hybrid/trekking bike which would explain that. You could try one kit for starters, then a second minus battery at a later date.

At the moment it is not possible to mount an eZee battery in the triangle.The best option for this is the Bionx at twice the price of an Ezee kit.

flecc · Jun 6, 2011

Oiseaux said:
This continuous debate about Bafang motors is very puzzling. I tested them two months ago and both were without a doubt very heavy to pedal without assistance, but I have read on this site others who say this is not so for them.

Oiseaux

There is drag, despite claims from some suppliers and strong cyclists that they experience none. I've owned two models and have ridden a number of others, all freewheeled versions and all have had drag at cycling speeds. The occasional mention of freewheels is a red herring.

The freewheel disconnects the motor, but the epicyclic gears remain engaged at all times and still rotate when the motor is not used. The losses due to the epicyclic gear are fourfold:

1) Tooth friction at six driving points between sun, planets and ring gear.

2) Grease "stiction" as the teeth engage and release.

3) Distortion due to the nylon material almost always used for the gears.

Number 1 will vary according to the state of dryness of the gears.

Number 2 will vary according to the grease type, it's age and the amount.

Number 3 will vary according to the nylon quality, the thickness and stability of mounting of the fairly thin ring gear.

All three will also change according to a 4th variable, cycling speed, drag increasing with speed in a linear fashion.

All these variables mean that motors will vary to a considerable degree, so a strong rider with a lower drag hub on easy to moderate territory will notice little drag. Conversely, a weaker rider with a poorer example riding in difficult territory can be severely affected, so the range of reported subjective impressions will differ greatly.

An example of the effects of an epicyclic gear is that of hub gears. Three speed hubs and one make of five speed hub use a single epicyclic gear. Independent tests show a typical efficiency of around 89% for the best three speed model, some 10% below that of a good derailleur. Now bear in mind that the hub gear figure is an average of all 3 gears and the middle gear is direct drive, so at 100% efficiency. This means that the other two gears which do use the epicyclic are at a mean of under 84%, an efficiency loss of 16%. Now bear in mind that in a hub gear the cogs are precision steel ones, not nylon like that epicyclic in the hub motor, and you will begin to realise that zero drag in an internally geared motor like the SB models is impossible. That 16% loss example isn't academic, it's a subtraction from your pedalling input, and it's why racers use derailleur gears and never epicyclic hub gears.

flecc · Jun 6, 2011

In addition to the numbered three variables which could apply, there is a reason why the Giant's Sanyo motor is particularly low drag.

This motor was originally an American design which included regeneration, meaning no freewheel and high drag all the time. Sanyo bought the design from the Birkestrand Corporation and used it themselves in Japan and Giant adopted it after abandoning the Pansonic unit. That Giant Twist 1/2 series model used the regeneration but it didn't work well and the high drag was badly received in the market, leading to dealers heavily discounting to get rid of them.

So Giant had second thoughts and with Sanyo removed the regeneration, fitted a freewheel and paid attention to getting drag as low as possible to make amends. Their current Twist Freedom and Express models are therefore much better in this respect.

Suzhou Bafang haven't been entirely asleep though. The latest side entry cable motors have a smaller diameter much thicker section ring gear in the epicyclic, which will be more stable. I'm therefore not surprised to hear reports of them having very low drag, but I've yet to try one.

Andrew harvey · Jun 6, 2011

Interesting, anoughter red herring I'm afraid Flecc, Epicyclic gears do require a finite amount of power to turn them, however losses due to epicyclic gears, as in say a hub gear only become appreciable when there is transferr tourque passing throught them, when they are not transmitting power they do not absorb appreiciable amounts of power.
You do seem to have something against nylon gear cogs, can I suggest you speak to the people at amongst others Volvo who have used nylon gears for 20 odd years to reduce friction in their cars. I had a 740 estate built in 1986 the owners manual specifically warned agaist engaging 5 gear below 40 mph because it had nylon gears in top to reduce friction and lower fuel consumption.
When there is no power passing through the nylon cogs they will not distort.
'Grease stiction', the grease applied is very soft when new and eventually will fly of and deposit itself around the inner ring.

Here the test lift the back wheel of the ground and spin it, Flecc has will argue this test proves nothing, he's wrong , the rate at which the wheel slows is directly related to the amount of drag it feels. Try the same thing with a basic mountain bike wheel it will stop in a similar time from similar speeds. Try this with a 20 year old Sturmey Archer and the wheel just keeps spinning and what sort of gears do they use? Again this comes down to the fact that epicyclic gears only run at high losses when they have power going through them, at other times the losses fall away.

flecc · Jun 6, 2011

A simple fact Andrew, huge numbers of people experience drag with these motors, often very noticeable as Oiseaux has reported above. We've had a couple of members who swap the motor wheel out for some trips to make unpowered cycling much easier, and I've experimentally swapped out a front SB motor wheel for a normal wheel and the bike ran as freely as my Panasonic unit bike where it is a pig to ride at 13 mph or more with the motor in. And yes, the motor is freewheeled and the freewheel works.

I know in theory it doesn't make perfect sense, but we don't pedal theory and we know when pedalling hurts more. I've suggested above the list of possible sources of the drag that so many experience. Not all will necessarily hold good, but some must since all the many who have complained of drag over the years of this forum, most often with SB motors, cannot all be wrong.
.

flecc · Jun 6, 2011

flecc said:
all the many who have complained of drag over the years of this forum, most often with SB motors, cannot all be wrong.

Further to the above when I was short of time to answer, since a row with someone else who claimed there was no drag and said he'd never seen any post saying there was, there have been 7 posts acknowledging the drag in just 12 days. That doesn't count my mentions.

In answer to Andrews other points, the efficiency of nylon 6 gears, dry with simple profiles is typically about 88%, for the equivalent steel gears 98%. The claim that Volvo use nylon for efficiency cannot be so, nylon gears are primarily used for the lower noise they produce. The reason they produce less noise is that instead of dispersing lost energy via noise, they absorb it by virtue of the softness of the material, i.e. distortion to produce loss through heat. This answers the claim that there is no distortion. In any case, the Volvo example is not comparable since there the gears run in a permanently oiled environment and will be of the highest specification. As Ian Hughes of Storck Raddar has observed, there are very different qualities of nylon gears and a glance at SB source prices indicates at which end they almost certainly stand.

Regarding epicyclic loading, there is friction and "stiction" at the six gear points mentioned and they constitute a load which appears at the hub shell. Though small in total when not driven, that means zero drag is impossible.

The contention that there's no stiction since the grease is dispersed does not hold true since a thin layer of grease remains on the tooth profiles for much of the life of the gears. If it dispersed immediately and had no lubricating presence, manufacturers wouldn't bother to put any in, so that presence makes stiction a fairly permanent feature.

jerrysimon · Jun 6, 2011

Ok as promised I have done a couple of videos with my recent conversion using a 190RPM Tongxin in a 26" wheel both from manually spinning the wheel up to 11mph (pretty frantic slapping of the wheel lol), powered up to 18mph and back down to rest. This one definately spins for much longer than my 260RPM Tongxin in my 16" rim which I guess makes sense.

The manual test spins for about 30 seconds down to stop from 11mph after I stop spinning it. The powered test spins for about 50 seconds.

Manual spin

[video=youtube;9eflebcfBJg]http://www.youtube.com/watch?v=9eflebcfBJg[/video]

Powered spin

[video=youtube;x_hZziLq7eM]http://www.youtube.com/watch?v=x_hZziLq7eM[/video]

PS although my 26" rim was calculated to spin 14.8mph it seems to spin up to 18mph not sure why. The computer is set correctly ?

PS note it even turns back very slightly after it stops. I spun the back wheel and it is clear that there is drag on the front as the back one continues to spin for ages.......................

Regards

Jerry

flecc · Jun 6, 2011

As you say Jerry, it makes sense that the 26" wheel will perform better due to the flywheel effect.

Motors often spin faster than specified rpm under no load conditions. A 22 mph specified hub motor I had in a 700c rim spun to 26 mph with no load.

Andrew harvey · Jun 6, 2011

For the perceived drag I can only express my findings, which are that there is little drag from these motors, OR I am to ham fisted to notice it

Now I have ridden Bafang motors with no freewheel and there is drag, noticable drag from above about 10mph, next to this the drag produced by a motor with freewheel is negligable. A simple test is to take a bike to the top of a hill scoot forward and see what peak speed it attains, any drag in the system should be proportional to speed, so the faster the bike rolls the more drag the motor should produce and the greater the difference between the speed with motor and without.
On my way to work I expect to see 25 to 30 mph depending on wind conditions, although I have had to pedal down on a couple of occasions to maintain far lower speed.I have never repeated the same trip after changing the wheel to gain an exact comparason, I use this hill most mornings when the wind is generally lighter than during the middle of the day. In the last year on my trike I have tried a 250w Bionx, a 26" geared SWXH, a 20" geared SWXH and an Anada Q100 as well as the original 9 speed wheel. Now I estimate that the low wind resistance of the trike appears to add about 2mph to the downhill speed, but at such low speeds it's hard to be accurate, not one of the motors I have used have made a difference that could be assesed in the once a day trip.
I have however taken a variety of bikes home, as a result I would say that I would rather pedal one of these motors without power than a mountain bike with nobbly tyres. Further to this for the last few weeks my son, (he is 11), and his friend have been riding to school along the lanes, they are single track for a good strech, so I been riding with them. They bot6h have mountain bikes with nobblies, I have 3 wheels but Marathon Racers and the extra drag of the motor. When we get to the top of the hill they have to pedal to keep up with me whilst I put my feet up.
This demonstrates to me the amount of drag my motor produces is less than a set of nobbly tyres, now you don't here most many people complain about tyre drag, except me and the damn kids on the BMX s

I have looked back at some old reports on Crystalyte motors from a few years ago. There was a story that a lot of the drag found on these was due tyo poor machining, were the axle holes were not directly opposite each other. Since the freewheels on my motors are largely produced to a similar design to yours, they should only be as good as yours, so perhaps misalignment of axels might be more of a concern. In that case it may have been pot luck as to wether you had drag or not, with the oldeCrystalytes it seened the clogging drag did seem to vary from one motor to anoughter.
It may well be that they simply have different machines to produce different motor cases, so different models have slightly better tolerances.
If you get the chance you'll have to try one of the newer motors and report how you find it compares.

flecc · Jun 6, 2011

I've no doubt about anyone's experiences Andrew, there are so many factors involved both personal and mechanical that there is no one right answer. It's just that I cannot dismiss my own and other's experiences. Oiseaux's experiences above are typical. Clearly he knows when there is no perceptible drag as with one Giant example, but he perceived some small measure of drag with another example of the same bike, the variability I've spoken of. With two SB examples he experienced much more drag. It's highly unlikely both were not freewheeled, I've never come across a fixed one yet that wasn't a regen version.

I know that in my most recently owned examples, I usually rode unpowered of choice at between 15 and 18 mph on my Lafree for the first three miles in my one flat direction route. On both the SB motored bikes, I couldn't even contemplate that. One is too exhausting to pedal without power for any length of time and is always a misery at over 13 mph. That's the better one, the other is strictly a power only bike these days. Both are normal enough bikes other than being electric and as said, one was transformed with a temporary normal front wheel.

I'm fairly confident the newest side entry cable SB types have improved in this respect since I've had reports of that from a couple who have complained of drag on older versions.

Cyclezee · Jun 6, 2011

eZee Spinning Wheel

The following video demonstrates the freewheeling ability of an eZee motor

YouTube - ‪eZee Spinning Wheel Demo by Cyclezee‬&rlm;

jerrysimon · Jun 6, 2011

Interesting that one seems to spin well.

Another thought occured to me that if the hub also wieghs more won't it also tend to spin longer.

I guess as stated this test is not really valid as there are so many variables its hard to measure their actual drag in real road/load conditions ?

Maybe it could be done on some sort of rolling road ?

Regards

Jerry

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