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

[flecc]

As I posted kraeuterbutter, that mention of belt on the first version was from an independent news announcement of the Sparc, not from my knowledge as I've never had access to one. From what you've said it seems the poor reviews of that first version were justified, but it seems they've greatly improved the later one.

Hopefully your revision will make it the best of the three!
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[rooel]

Sparc Sram

kraeuterbutter, you may be interested in some photos I have taken of one of my own 16.8v Sram Sparc modules (for 20" wheel).

You will see that the circuit board is exactly the same in almost every respect, as are the sockets for power and the controller/battery meter cables (the white substance is some silicone sealant which I have introduced to improve resistance to water ingress).

The motors look the same, but as they are unlabelled, and are reported to be quieter than those used in the 12 volt system, they are probably different from yours.

The only visual difference I can see is that the motor drives the gears through two toothed belts.

It would appear therefore that the increase in power and range was achieved by Sparc by simply upgrading the batteries to NiMh, and improving the motors.

I have noted what you say about the quality of the circuit board components, and not being an electronics expert cannot comment, except to say that it all looks very competent to me, and that we would not want, or want to pay for, military/medical grade components on a board whose main functions are to conduct power from the battery to the motors, start the motors when road speed is around 1 or 2 mph, stop them when it is around 15mph (to comply with EU law), and sense the speed (not torque) of the pedals to determine the level of assistance to be provided.

As for the quality of the plastic supporting the motors, it seems strong enough for its purpose, and I wonder if the damage to yours was caused not by bumping over a kerb, but by someone trying to remove the black plastic unit without first discovering, and removing, the four securing screws which are concealed under the circuit board.

 

[flecc]

Thanks for that Rooel, so I was right in saying I'd read a report of belt drive used in this bike motor though I had the impression that it was the earlier version from that report.

I would think the change was in the interests of noise reduction, since this had been so criticised in the original.
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[kraeuterbutter]

@flecc, all:

i have bought now this bike:
20" KLAPPRAD FALTRAD KLAPP KLAPPFAHRRAD 6 GANG SILBER bei eBay Fahrräder, Radsport, Sport (endet 05.08.07 22:30:14 MESZ)

what do you think ?
(i didn´t want to disassamble my mountainbike just for a test... so i bought this one)

when the SRam Sparc runs up to 25km/h in an 26" wheel,
it should be around 19km/h in an 20" wheel and of course be a better hill-climber

are there any problems i have to face ?
(spokes in that size ?)

 

[kraeuterbutter]

@rooel:

It would appear therefore that the increase in power and range was achieved by Sparc by simply upgrading the batteries to NiMh, and improving the motors.

maybe they even have not changed a thing with the motors, and just increased voltage..
we run such motors in rc-cars with 14,4Volt or 16,8Volt..
(of course there is a big difference: rc-car -> 5kg weight, BIKE: 100kg
on the other hand: we use about 3,3Ah of capacity out of 16,8Volt in 10min
so the average power seems not to be that much lower than with a sram-sparc)
the motors get realy hot when running them that hard..

I have noted what you say about the quality of the circuit board components, and not being an electronics expert cannot comment, except to say that it all looks very competent to me, and that we would not want, or want to pay for, military/medical grade components on a board whose main functions are to conduct power from the battery to the motors, start the motors when road speed is around 1 or 2 mph, stop them when it is around 15mph (to comply with EU law), and sense the speed (not torque) of the pedals to determine the level of assistance to be provided.

i have nothing to say about cheap components..
when looking on it, it seems to be not that expensive at all...
iam just wondering, why the sram-sparc is sold that expensive, when the motors are 10Euro cheap motors, the inner parts are from cheap plastic (no stiffed carbon-plastic which would be a reason for higher price) and cheap electronics...
a new sram-sparc is realy expensive (at least i was told so)

As for the quality of the plastic supporting the motors, it seems strong enough for its purpose, and I wonder if the damage to yours was caused not by bumping over a kerb, but by someone trying to remove the black plastic unit without first discovering, and removing, the four securing screws which are concealed under the circuit board.

yes, i think so too...
from torque of the motors the plastic will not break, also the torque is handled by the motor-plate, so the cover which broke should not see anything from the torque..
i believe, it was a jump over a curb or a curb-hit by the owner before me..
and: no, i have not damaged it by disassembling it if you mean that

thanxs for the pictures !
belt drive is everytime a good thing when it comes to noice
(made a big difference in my electric helicopter when changed from pinion to belt-drive -> quieter and much nicer sound)

 

[flecc]

That bike is fairly typical of Chinese made folders these days and should be ok.

Are you proposing to try the Sparc in one of it's wheels, I'm not quite clear if that's the case?

Spokes should not be a problem as they are available a wide range. For example, have a look at this UK dealer's spoke page for one particular type meant for small wheels like those on that bike. You'll see in the dropdown menu a list of sizes from 120 mm to 246 mm in 2 mm steps:

spokes
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[kraeuterbutter]

yes, i want to mount it in this 20" bike..

prevously i wanted to take my old Biangi mountain-bike, but on the other hand its a mountain-bike and driving onroad all time with it would be a shame

i have posted your link in an Austrian Bike-Forum and hope to get help..
(the guys there are maybe too much experts... when you look at there buy/sell-threads there are barley used bikes for less than 1000euro, there are even used bikes sold for 3000Euro and more !)

so i didn´t mention about the 20" "Chinese-bike", otherwise i fear i would not get any answer *lol*

40 Euro for the bike (new) is realy ok, not risking much with that..
when it runs 15km/h with that i would be happy..
maybe it would be able to go up some hills too

 

[flecc]

maybe it would be able to go up some hills too

It will certainly go down hills ok, so you're guaranteed it will be at least half right.
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[rooel]

kraeuterbutter, I agree, Sram Sparc may have done no more than apply a higher voltage to the existing motors. If so, it is little wonder that the earlier system with the 12 volt batteries was rather weak. I expect most respectable electric motors can stand a fair amount of overvoltage (+25%, or 50%?). I have had no problems substituting a nominal 18.5 volt lithium polymer battery for the nominal 16.8 volt nimh in my system, and that 10% increase certainly adds a bit of zip to the motor performance, so much so that when the lipo is fully charged (a no load measurement of 21 volts against 18 volts with the fully charged nimh) it rapidly takes me up to the cut-off speed of 15 mph and leaves me to pedal on my own rather more often than with the nimh.

I agree a new Sram Sparc kit is expensive (around £700 in the UK, if you can find it, as the official importers, Fisher Outdoor Leisure Limited, are hopeless at maintaining regular supplies of anything). And Dahon who used the Sparc system in their Roo El seem to agree as they have discontinued that model, allegedly because of the expense, and they would be getting them on a bulk buy straight from the manufacturers basis. However the Sram Sparc seems to be the only kit which builds the five speed gear, two motors, and electronics measuring pedal speed, etc all into the hub, providing a fair amount of protection against dirt and water. Everything else I have looked at uses external derailleur gears, drive chains, pedelecs, etc.

By the way my suggestion regarding the cracks in the black plastic was that a previous owner, not you, had tried to wrench it apart without discovering and removing the concealed screws. I am sure you would never do any such thing.

 

[kraeuterbutter]

hmm...
i more likely believe, that it was from some jump or curb..

the motors are not screwed to the front-plate as we do it with them in RC-cars..
(on cheap rc-cars with plastic-motor-mount, that motormount breaks on impacts/ high jumps)

in the sram sparc i have, the frontplate is only used to prevent the motor from spinning around its axis, so:
to work against the torque..

without the endplate it would fall off, because it is not screwed on the front
and i think: on a jump etc. etc. the endplate was cracked by the weight of the motors

question: the sram- 5gear-hub which is used:
is this standard work ?
if get a shift-handel-bar for a normal 5gear-sram-hub, will it work ?

 

[flecc]

Yes, it's the standard P5 hub kraeuterbutter, using the usual twistgrip control.

The only variation they ever did was a Cargo version with a slightly higher ratio but stronger low gear, 225% range instead of 250%, but I'm sure that also used the same control as it was only the epicyclic that was changed.

The latest hub core has a taper on the end of one of the components which has no function but may have been for manufacturing convenience in machining the part.

There was a change to the r/h spindle end on the later hubs to improve the location of the actuator which meant that the old actuator would not fit unless modified, but that won't affect you since you're doing the opposite, putting a new actuator on an old type spindle.

Together with a clearer window on the later controls, that seems to be the total of the P5 changes over the years.
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[kraeuterbutter]

thx..
so i need a Twist-grip + mechanics for a P5 Sram gear

hope to find that used in some bike-forum (want to keep the whole project cheap as possible )

for batts:
i think i will use 4s5p Konion... have such a pack lying here around, not used until now..
14,8Volt (right after charging 16,8Volt)
5,5Ah
rated: 60A contiouse, 110A short
900g light

thats a fine, small block which i will be able to mount it on the frame and still the bike should be foldable

for the sporks:
i have asked in a big forum here: there is no online-store in Austria were i can get such sporks with that length..
so i will have to order them from UK ?!?

 

[flecc]

Spokes can be difficult and that's why I gave you that UK link kraeuterbutter. It's a nice change to find something manufactured in Britain, and I've used those spokes and can say they are ok. You will find St Johns Cycles a good company and I'm sure that they will be happy to despatch to Austria.

When locating a used SRAM twistgrip and actuator, make sure the actuator rod and tube are in sound condition. The alloy tube that goes into the hub is easily damaged at the ends, particularly the outer end where it's notched.

Other possible faults are the cable adjuster plastic thread badly damaged, missing spindle locking bolt, missing brass centre clamp in the rotary actuator, or missing red plastic locator sleeve. That whole actuator assembly is not very well engineered and easily prone to damage from clumsy fitting.
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[kraeuterbutter]

so.. update..

got the 20" bike today..
the spring at the rear-wheel --> well, does not work very much at all.. so its more for "looking good" than anything else

the front-wheel had - out of the box - a little "8" (the wheel is not straight, don´t know how you call this)
its not that much that it is not drivable, but too much to be ignored

then first driving:
whohooo.. after 5min i got a little bit familar with it (never drove a 20" before)
the steering is compared to a 26" very easy to turn...

hills: no way you can go up hills with that
when you try to pull on the hand-bars the whole front bents..
i thought: smaller tieres will give slower speed and for that better clmbing-abilities
but you are not allowed to pull on the handles its too weak for that in my eyes..
the breaks: as long as you don´t go over 15-20km/h and don´t go down hill taller than 10-15% they are acceptable for the moment

so.. now iam wondering:
should i realy spoke in the Sram-sparc into a 20"-rim ?
if it works and i say: yes, it has enough power for me

--> can i invest 200-300Euro in another 20"-bike (does not need to be foldable) of higher quality and will this be better,
or are all 20"-bikes weak like butter and not usable to go up a 10-15% hill ?

AND: question specially to flecc with his lot of experiences:
do you think the sram-sparc 12V can bring me up a 10%-12% with the 20" rim wheel ?
the slower speed it will get in flat terrain compared to 26" will be ok, because anything faster than 20km/h is nothing i would want to do with this bike..

maybe the bike will be driven by my mother:
19kg the bike (19KG !!!! for such a small bike !!)
2,5kg the motor + controller
0,4kg the battery
50kg my mother

would this combination go up a 10%-12% hill ?

oh: best thing: when unpacking the bike by pulling it out of its box i ripped of parts of the baggage porter
*lol*

 

[rooel]

For a better experience with the Sram Sparc, Kraeuterbutter, I would recommend you to spend £300 (rather than euros) or more, on a mid-range Dahon 20" folder, such as the Speed P8. I have installed the Sparc on that, and with its cromoly frame, and Big Apple tyres, have found it safe and stable for both town and country.

If, as we suspect, Sram "upgraded" the 12 volt motors by simply substituting a 16.8 volt NiMh battery for the 12 volt lead acid, you should try one of these too.

 

[flecc]

I agree with Rooel, kraeuterbutter, the cheap folders often have poor steering columns. Any Dahon would be much better.

From what I've read of the Sparc in reviews, the older version should climb 10% with just moderate pedal help, but may need a bit more effort on 12%.

The newer model would do both quite easily, and possibly you can upgrade as Rooel says.

Answering your query, when a wheel is not "straight", we say it is "not true", or "out of true". Correcting that we call "trueing".
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[Jwptm2016]

Hi I have this sram sparc bike as well and need help with little problem with motor motherboard need to know what part is this is this a sensor which is my guess or what?

 

[Nealh]

They are obsolete now and doubt you will find any spares, your best bet might be to try and somehow re-solder the broken part back on .

 

[geojorjika]

Hi Guys

i've just bought second hand SRAM Sparc , i looked inside it and everything looks good, no physical damage and no burns, i've connected with 13.5 v power supply (polarity is correct) but no reaction, no led light on control panel. i tried to rotate the hub motor, but still no reaction. even i tried to connect power supply ( 2 to 14 v) only to controller but still no led light.

anyone had electronic problem with sram sparc?

 

[ata2k6]

Hi I have this sram sparc bike as well and need help with little problem with motor motherboard need to know what part is this is this a sensor which is my guess or what?

Hi, that's a reed relay. Probable that is sensing when you pedal and start the motors. The 2 small black 3 terminal components are hall sensors, they are responsible for the speed measuring. There is a magnetic disc on the axle, and these are counting the revs.


My question, is there any difference between US and EU version, as I see US has higher top speed, is there any difference on the mainboard? US is limited to 20Mph (~32Kph) and EU is 25Kph. I'm wondering is that limiter can or has been modded by somebody?

My motor is a 2005 build (16V version, belt driven), I'we just upgraded the battery to a 5S7P config(18V 20Ah) mod) , ( that fits perfectly to the old battery box and I'm able to use the original charger and plug too (original charger voltage is 21V 2A) so it's exactly perfect for 5S max voltage.
Other planned mod is to install another parallel power mosfet, as they have the place on the board, so I guess it would give some extra amps at low revs.

It has really good torque but it tops out at 25kph by cutting power completelly, I'm wondering if top speed limit can be extended a bit more as I have the EU version and I would like just a little bit of more top end.