SRam Sparc -> how does it work (technically, two motors ?)? how in practical use

[kraeuterbutter]

offtopic the second:

here just some real-world data of a motor i use myself and have measured myself:

its a Lehner 1930-8 in star-configuration
230g light
36mm motordiameter
56mm long

i think this motor may maybe fit into the sparc


here the data i measured myself within an rc-offroad buggy (~ 3,3kg heavy)

you can see:
peaks around 50A
voltage: it was a 400g light 5s Lipo used
rpms: up to 30.000rpm
Watt: up to 950Watt peak, average was 180Watt
not that bad for such a small motor, its enough to outperforme the nitro-buggies at our field

so i think this motor should work ok in the sparc.. maybe too fast spinning ?
but there are 30 other windings available for that motor

 

[flecc]

It certainly looks promising kraeuterbutter. Were you still intending to use two motors? I'm not sure if just one is possible due to the belt drive outside the gear hub, but you may be able to have just an idler pulley in place of one of them.
.

 

[kraeuterbutter]

the problem with two motors is, that i would need two controllers..

i use brushless SENSORLESS controllers from Kontronik

here the specs of the KOntronik JAZZ 80-6-18
(for up to 6s lipos)
or the JAZZ 55-10-32 (for up to 10s Lipos)
Jazz - Drehzahlsteller für sensorlose Brushless Motoren, Jatt - Speed controllers without Sensors for brushless motors

the controller works without sensors, does not need hall-sensors, etc. etc.
it has features like:
BEC short circuit protection, Auto Programming Mode, Automatic Power Consumption APC (Governor-mode), Proportional brake (i would not want to use that in an heavy electric-bike because of overheating of the controller), Reverse polarity protction, Short circuit protection, False start protection, Current limiting, Overtemp. protection, Undervoltage cutoff, Active free wheeling circuit, and a frequenzy which adjust itself from 6 up to 32 khz, auto timing for best efficience at all circumstances, ....

so you see: even it is "only" a rc-hobby-controller (rc-cars-helis-planes-boats) there is lot of technics/hightech and knowhow inside that controllers..
its also programmable in different modes (how fast it spins up, when it cut offs, how strong the brake is, ...) and with a programmable card

but two motors: its doable, but the motors must be syncronized because the controller sees only one motor, not two !
so, when the motors are not syncronized it will not know how the rotor(s) are standing and can not power it...
baddest case -> controller gets destroyed

for that: i would realy prefere a single-motor-solution, or i would need two controller which is expensive..

 

[rooel]

Sram Sparc, the true story

I have only just come across this thread and even at a cursory glance find quite a bit of misinformation in it. I would suggest a look at http://www.sram.com/_media/pdf/sram/dealers/TM_GHS_MY06_E.pdf
where, straight from the horse's mouth, everyone will find accurate technical details of the SRAM sparc system with illustrations.

This is the latest 16.8 volt version which definitely does not use ex-power tool motors, or a drive belt. It is a very sophisticated set-up with the 5 speed gear hub (all metal), the motors (brushless), together with the electronics which note wheel speed and cut the motors at 15mph, and provide motor power in direct proportion to pedal speed, all enclosed in the steel hub casing. There are therefor only three external parts: the gear shifter and the on/econ/off switch on the handlebars, and the battery on the rear rack. The motor power is transmitted to the gear hub within the casing by means of nylon toothed gears (one of which runs round the internal circumference). I have never heard any reports of these stripping, an unlikely event, given the well controlled motor output.

I have found that the system provides power more or less equal to what I put in myself, and I assume that like most average cyclists I produce somewhere between 50 and 100 watts. Any cyclist who can produce 200 or 300 watts does not need an electric assister!

 

[flecc]

Thanks for this up to date information rooel.

But where is this "quite a lot of misinformation" you mention? No-one said they were power tool motors or that they were the same, only that the original ones were similar to power tool designs,which they were.

kraeuterbutter bought his cheaply second hand, so the latest information has only limited application since it was considerably improved after being received very badly when first released. His could well be the first version.

I also disagree about cyclist power and the need for electric assist, and suspect you don't have to ride up very steep hills where you are. If you live in a constantly hilly area and have to ride up long hills of between 14% and 20%, with some a mile or more in length, 200 watts will mean a miserably slow rate of progress. If you carry shopping or other items with weight regularly in such conditions, the need for assistance becomes even more apparent.

I wouldn't regard any assist system that could only match 50 to 100 watts of rider power as adequate at all, or even worth purchasing, and neither would any experienced reviewer. Even one of the most popular which was limited to equalling rider power, the Giant Twist series, could give up to 390 watts of power.
.

 

[kraeuterbutter]

thx for your information !

i don´t know (yet) if it get the 12V (old version) or the newer 16,8Volt one..

i have looked at the document:
where have you the information from, that the motors are brushless ?
maybe do you know which motors are used as well (brand) ?!?

from the picture from page 48 it still looks like it was a typical canned motor (like there are running 100.000 each day from chinas assembly lines
but well: saying that fromt hat picture is a little bit too easy
from the other pic of the sram-page (the rendered half-open-see-through-picture) there are 2 wires to be seen.. so i assumed that it must be brushed motors)

I have found that the system provides power more or less equal to what I put in myself, and I assume that like most average cyclists I produce somewhere between 50 and 100 watts. Any cyclist who can produce 200 or 300 watts does not need an electric assister!

iam studying informatics and meanwhile also sports..
so: iam maybe a little above the average i-cycle-to-work cyclists when speaking about leg-power..

so why do i want a electric bike ?
1.) iam very interested in the technic of it...
2.) the idea, that a bike helps me with some power is challenging
3.) when i drive to my university i have to go for 9km each way...
not that far, few slopes..
nevertheless i would like to drive the same every day without transpire

for the reason to be able to go faster than 25km/h i want a bike with no added rollrestistance -> when i read it right, the sparc is such a system..
sparc + light battery should give me only 2 - 3kg added weight compared to normal bike

two other reasons:
my girlfriend was once making a very small tour (20km ?) to our palace and our castle ruin with me.. the region is hilly country

well, after that see said to me (with red head): "i will never drive with you bicycle again")

so i also think, that this ~100Watt+ for her could help, that see would change here opinion

last but not least: maybe i will give the bike to my father (60): he had an car-accident 20years ago, his legs for that enfeebled
we have a second house (dead grandmother, house is empty) were flowers have to be watered every 2nd day..
its only 2km away, with a hill between..
a light bike with some added power would help my father big time..
(i guess my light bike with sparc and batteries will be still lighter than his 20year old mountainbike )

so that said to my motivation..
but biggest part is: the technical thing, using componentes from my rc-hobby (300-500g light batteries, maybe controller and motors) to drive me around

 

[kraeuterbutter]

@flecc/rooel:
can you say from this picuture what version
it may be ?
eBay: Sram Sparc Elektromotor E-Motor (Artikel 300116817559 endet 10.06.07 21:00:00 MESZ)

i guess big time its the old one.. (he sold 3 sparc, all used)

 

[kraeuterbutter]

@flecc: you have edited your post so new question come to my mind..

so far i have only driven/tested e-bikes in complete flat area ;(

the real interesting part would be on hills/slopes..
when i considere:
pedaling with 100Watt --> can do that all day long
pedaling wiht 200Watt --> start to sweat after some time

so my imagination would be:
i can have about the same power (200Watt) but only investing 100Watt myself and for that not sweat..
downside: 5-10% added weight (bike+cyclist: 93kg, e-bike + cyclist: 100kg)

on weak e-bikes/pedelecs: is there a point on a hill (lets say 10-15%) were you say:
without the electrics i would be faster ?
so, a point were the added weight of the bikes is more a disadvantage than the added power is a advantage?
or do you provite anytime (more or less) from the electrics..

i can´t believe that 5-6kg added weight would do more harm then 50-100watt added power helps (assuming a horrible eff. of some e-bikes which are made to drive 30km/h and slowed down on the hill to 10km/h)

 

[flecc]

Yes, it's nearly always the case that you gain from having the added power kraeuterbutter. One downside is that if you don't use battery all the time, the bicycle part of the electric bike is often much less efficient than a normal bike. It's not only weight, they usually use fatter tyres which are often high drag designs.

Of course if you use your own bike with a kit motor like the Sparc that's not a problem, and the weight doesn't matter on the flat except when accelerating.

You shouldn't be limited to only getting half the power from the motor if you are providing your own motor and controller, you can arrange that to suit yourself. The nylon gears won't be a problem as rooel said, many hub motors use these nylon gears with up to around 500 watts of net power, and two of my bikes using one of the most powerful motors do.

I think what you're doing is sensible if you have the 12 volt version, since it was widely agreed that it was far too weak to be useful. Clearly SRAM agreed since they upgraded it with more power and other improvements, though the latest version is still one of the lower power systems.
.

 

[kraeuterbutter]

i see..

a powerfull bike (500Watt+ hub-motor for example)
will on the other side weight a lot..
often 7kg for batteries, 4kg for hub motors --> that are over 10kg added..

the sparc weights only 2450g, + the throttle and some cables..
let say: 3kg
(- 1kg for a normal 5speed-hub without motor(s))

so at the end: without batteries i hope there should not be much more weight added than ~2kg

and for batteries: i will use small ones, for sure less than 1kg
(my 4s Lipo from Heli weights 340g (0.34kg) only.. theoretically it will give constant 200Watt poweroutput for 18min which should be enough to start with - or 6min long 600Watt for the hill between our houses which should be also enough)

EDIT:
my next batteries for heli will be this:
http://www.elektromodellflug.de/akku-test/bilder/kokam4000.GIF

i think that should work very well in a bike... (specially when you want low weight and only low voltage-system is used)
and still.. very light

also impressive the safety-standards of this new cells..
**** KOKAM ****

 

[flecc]

Those batteries do look good, and that safety testing is very thorough it seems.

The bike weights aren't quite as bad as you said at first. My Quando and Torq motors are roughly 3.5 kilos built into the rim, the Li-ion battery is 4.4 kilos and my Q bike variation can give 35 miles/56 kilometres range with those. It's a brushless 576 watts gross motor, net power at the rim over 460 watts for 7.9 kilos. Not as much as your RC models, but it will do this for more years I suspect!

It's enough power to frighten the horses!
.

 

[rooel]

"But where is this "quite a lot of misinformation" you mention? No-one said they were power tool motors or that they were the same, only that the original ones were similar to power tool designs, which they were."

Agreed, but the current Sram Sparc motors do not sound anything like my electric drill,whereas, according to A to B magazine, the older ones did.

"kraeuterbutter bought his cheaply second hand, so the latest information has only limited application since it was considerably improved after being received very badly when first released. His could well be the first version."

As the 16.8 version only became available at the beginning of 2005, I think he almost certainly has the older 12 volt version powered by sealed lead acid batteries.

“I also disagree about cyclist power and the need for electric assist, and suspect you don't have to ride up very steep hills where you are. If you live in a constantly hilly area and have to ride up long hills of between 14% and 20%, with some a mile or more in length, 200 watts will mean a miserably slow rate of progress. If you carry shopping or other items with weight regularly in such conditions, the need for assistance becomes even more apparent.”

I am not sure where other posters live but here in the EU there is a limit of 250 watts power, and a top speed of 25kmh while in North America the limits are much higher. The chances of the police doing a random check may be slight but with illegal power a problem would arise in the event of an accident when insurance companies would disclaim all liability for injury to the cyclist or third parties.

“I wouldn't regard any assist system that could only match 50 to 100 watts of rider power as adequate at all, or even worth purchasing, and neither would any experienced reviewer. Even one of the most popular which was limited to equalling rider power, the Giant Twist series, could give up to 390 watts of power"

To be legal in the EU a diesel or petrol engine would be required complete with compliance with all the licensing, helmet etc regulations. I am 65 years old and have cycled almost every day for the past 30 years, mainly, however, a five to 8 mile commuter ride. I find that Sram Sparc on a 20 inch folder will assist me no matter how steep the hill and the amount of assistance is roughly equal to one gear level (by which I mean with the motor on I am comforable with the five speed shifter set, say, to 3, but with the motor off I would have to shift down to 2). If, with the motor on and the shifter set to 1, I find the hill too steep I get off and push or find another route which follows the contour. Unfortunately I can provide no measurements of the steepness of the hills in question but an excellent detailed review in A to B magazine (issue 48) says the maximum gradient is 1 in 20. Interestingly the same review says peak power is 170 watts, not the sort of thing which will appeal to power crazy North Americans!

Overall I have found that Sram Sparc electric assistance enables me to cycle further and faster, and that the exercise provided is at the refreshing, rather than exhausting, end of the scale. Others who are unused to cycling are simply enabled to cycle and have more confidence in entering heavy traffic areas.

As for the motors being brushed or brushless I can produce no documentary evidence, but I understand most electric assist motors are brushless (requiring no maintenance and being more efficient). If you look at Mr Motorvator's electrodrive pages you will see he regards Currie's recent switch to brushed motors as being retrograde as they will require maintenance eventually and reduce efficiency by up to 10%. The latest Sram Sparc motors have always been praised for their efficiency (if not for their power) and this has enabled the use of a small lightweight battery giving a total all-up weight (minus the cyclist) of around 18kgs, about 50% more than the weight of a similar bicycle without the electrics. That seems to suggest that with the peak power at 170, an 85 watt cyclist would receive assistance equal to twice his own output reduced by 30% to cater for the extra weight.

 

[coops]

I am not sure where other posters live but here in the EU there is a limit of 250 watts power, and a top speed of 25kmh

If I recall correctly, the EU limit is 250W continuous power, not peak power which it seems can be higher for assistance on hills etc. also, for less efficient motors, its not clear to me if that is 250W input (gross) or output (net) power: for many hub motors max efficency is around 80% tops, so could make around 62.5W difference i.e. 250W net output @ 80% efficiency is 312.5W gross input!

That seems to suggest that with the peak power at 170, an 85 watt cyclist would receive assistance equal to twice his own output reduced by 30% to cater for the extra weight.

Is that peak output power? I'm not aware of the efficiency of the SRAM Sparc, but presumably input power is a little higher at least? Even at 90% efficiency, input would be close to 190W, or at 80% over 210W.

An 85W, fairly lightweight cyclist of ~75kg, on a very smooth-running 12kg bike with low friction tyres, would still only travel at roughly 1.6-1.9m/s 3.5-4mph up a 5%, 1 in 20 slope, and half that speed up a 1 in 10 or 10% slope, assuming the bike has gears low enough to allow efficient pedalpower transmission at those speeds. Even at around 250W total output power, the same cyclist on the 18kg electric assist bike could only expect at best roughly 10mph on a gentle 5% 1 in 20, 3.4m/s or 7.3mph on a moderate 7%, 1 in 14 slope, and again less on steeper (in fact, if its not transmission drive, it may even stall on anything steeper due to lack of motor torque), slopes which can be climbed much faster and more safely by many hub motor bikes e.g. up to 1 in 7, 14% with little speed loss below 15mph on motor power alone, 10% and steeper with little pedalling also at over 10mph.

I'm not sure what you mean by "reduced by 30% to cater for the extra weight"?

Stuart.

 

[flecc]

As Stuart has said rooel, the 250 watt limit in the EU and 200 watt in Britain are effectively just legal definitions of a notional average power.

Virtually no electric bikes have peak power that low. Most in use in the EU peak at around 400 to 450 watts gross, some legal motors as high as 576 watts gross. For example, the recently introduced Giant Twist with the front hub motor grosses 400 watts.

There is even a legal one that peaks at almost 5000 watts, that occurring just at the start of rotation, the power then diving so that it still has an average across the range of 250 watts. That one, The Lynch motor, is used on goods trikes, so that total weights of 500 kilos can still be moved at low speed, around 6 mph.

David Henshaw at A to B who likes the Dahon Roo with the latest Sparc, says it's good for 12% without rider assistance, the 20% you mention being a reflection of his own considerable cycling strength. Most riders wouldn't find 20% easy. I'm happy to accept that the current Sparc is a competent if low powered motor, and I have used, maintained and repaired SRAM gearhubs for years and hold them in high regard. But as you may appreciate, the original Sparc that's the subject of this thread deserved the comments made about it.

Believe me, we are in a forum which very thoroughly understands the subjects of electric bikes, their uses and capabilities, and the laws in various countries, and we naturally are concerned that no misinformation is given. That's why I was concerned about your rather sweeping remark.
.

 

[Miles]

Stuart,

For both the EU directive and the 1983 Regs, the 200/250 Watt figure applies to the continuous output rating of the motor.

 

[rooel]

Coops, I am afraid I can provide no scientific measurements myself but the A to B review says the 16.8v Sparc has a peak power of 170 watts compared with 120 for the 12v. As for efficiency the same review says the Roo El narrowly beats the Giant Lafree to run at 6.7Wh per mile (around 1500mpg).

"reduced by 30% to cater for the extra weight"?

What I meant by this is that if an 85 watt cyclist who normally pedals a 12 kg bicycle without electric assistance transfers to an 18 kg bicycle with 170 watts assistance he will lose some of that assistance because some of it will be driving the extra weight. He will not therefore receive the full 170 watt assistance. I thought perhaps as the bicycle is 50% heavier and 6kg is one third of 18 kg the percentage loss would be around 30%, but I am happy to admit that these figures may be mathematical nonsense. I think however the principle I am trying to state is sound.

 

[Miles]

"reduced by 30% to cater for the extra weight"?

What I meant by this is that if an 85 watt cyclist who normally pedals a 12 kg bicycle without electric assistance transfers to an 18 kg bicycle with 170 watts assistance he will lose some of that assistance because some of it will be driving the extra weight. He will not therefore receive the full 170 watt assistance. I thought perhaps as the bicycle is 50% heavier and 6kg is one third of 18 kg the percentage loss would be around 30%, but I am happy to admit that these figures may be mathematical nonsense. I think however the principle I am trying to state is sound.

rooel,

It's the difference in the total weight, including that of the human motor, that you need to use....

 

[coops]

For both the EU directive and the 1983 Regs, the 200/250 Watt figure applies to the continuous output rating of the motor.

Thanks for the clarification Miles . So, depending on the efficiency, the input power could be as much as I said i.e. 200 or 250W would be the same percentage of max input power as the efficiency of the motor at the "rated" output power, usually also the point of maximum efficiency for a hub motor? (I'm not looking for more legal loopholes, honest! just clarity - if such a thing exists in law... ....)

Stuart.

 

[Miles]

The legislators aren't interested in how much heat or noise your motor generates... - or even the exact mechanical output at any moment in time - only the nominal mechanical output that can be sustained indefinitely. Does this clarify?

 

[coops]

Yes, Miles, absolutely clear thanks!

rooel, re: the input/output power for the Sparc, that's ok - it makes little difference really at those power levels & if its very efficient as you say; better than higher powered but less efficient motors too, after all its the useful watts that count! . Still, I hope you get my point that peak power of over twice rider input is useful on hills, even more so if a reasonable efficiency can be maintained.

6.7Wh/mile is very low, but in what conditions: speeds, terrain etc.? The same bike can get very variable range in different circumstances.

Also, efficiency and power consumption is one factor, but battery type, capacity, weight, charge speed etc. all affect the usefulness & versatility of ebikes. If one can carry more battery energy for similar weight, and recharge it in minutes, not hours, then while I like maximum efficiency, if its at a much greater initial cost, I'd probably go for slightly higher power and higher speed hillclimbing at lower efficiency!

@kb - sorry for taking your thread a bit off-topic how much peak torque do you think you can get from the Sparc with one of those motors, and at what sort of wheel rpm?

Stuart.