Gruberassist: lightest and most invisible electric drive for all bikes -> WOW !!

[kraeuterbutter]

what a cool thing !!
GRUBER ASSIST

don´t miss the videos with explanation on the webpage !
here how it works:
YouTube - Gruber Assist 2 English

YouTube - Gruber Assist 1 English
YouTube - Gruber Assist 3 English


some would maybe say: "pah.. only 200Watt? not worth at all"



i think you have to look from another direction on this thing...

what do electric bikes in generally have in common:
they are heavy (the "light" ones are around 20-23kg, but some are even close to 30kg)

when you are a sporty driver you invest a good amount of money to get a maybe 2-3kg lighter bike, invest money for light rims, ...
and what is done with the ebikes?
-> a 4kg heavy Hubmotor is mounted into the wheel
-> a heavy battery pack is included

if the bike should be driven without motorassist, you have to drive the 10kg of additional weight, and often there is even no free wheel build in =>
they call that regen. braking

Resulat: driving such a bike without motor assistance is not that fun at all (weight, drag) (you can see that on the bike-tests everyyear -> so you have to include even bigger, more heavy batteries to avoid running out of electricity


(you can see this for example in this ebike-test here: http://www.flyer-halle.de/download/Testbericht1_E-Bikes.pdf
the notes for driving without motor-assistance (1 is very good, 6 very bad)
Biketec Flyer T8 premium -> 2
Giant Twist Comfort -> 4
Heinzmann estelle „Elegance“ -> 3
Hercules Emove „Tourer“ -> 4
Gazelle „Easy Glider“ -> 3
Sachs „ALU Touring“ -> 2
Sparta „ION m-gear“ -> 4
Euromoto „BinBike“ -> 4
Helkama „Jubilee“ -> 3
Lohmeyer „Mistral E“ -> 3
)



with this Gruber-Assist and a light bike (something in the 12-13kg range) you should be able to have a complete systemweight of not more than 15kg
so still a real light bike, still a bike enoyable when driven without motorassistance
(when removing the battery its down to 14kg and the weight of the motor is in the maybe most center and least anoing possible position on the bike)


this seems to be a real other way of bike to me..
not going electric all time, but only when you realy need it, because: the bike should still run as good as before and shouldl be light and agile in handling
for that a smaller battery would also do the job because not that often used

on the page there are (unfortunatly in German, the inventer is from my country, Austria) some field reports..
for example from Marco, discribing how it helped going a hill with 24% average over 200meter of height (600 feet)

this 100Watt output (lets say 200 Watt input ? -> 80% motoreff. + multiple-stage-planetary-gearboxes + the gear on the bottom --> maybe 50% overall-efficience)
should make a good difference

and something i like: its good for going steep hills (for exaple 24%) or going faster in flatt regions..

i think when you wana go offroad the best choice so far...

downsides:
* the price.. (of course... very expensive)
* the noise it makes
* how durable is it ? the planetary-gearboxes of that small size and doing that big torque.. hmm...

man.. if there was not the price,i think it would be the perfect motor-system for my bike and my most-liked driving (in the woods climbing steep hills to the castles standing most times on the steepest hills here in Austria )

 

[flecc]

Yes, we've seen this before Kraeuterbutter, and it has been in some magazines.

I do favour a central motor system on a bike, but I see a number of technical and practical objections to this sort of downtube system and I'm not enthusiastic about it.
.

 

[kraeuterbutter]

oh.. damn.. sorry
i was so euphoric when reading all this i had to post (before using the search-engine.. have seen now, that it was already mentioned )

"normal" electric bikes all have a little bit the taste of seniors-bikes or bikes for disabled...
the 20 year old mountainbike of my father is lighter than most e-bikes..

just an example:
with my 15kg mountainbike i can drive 30km/h on the street and when i have to go up the footpath i just jump (lifting front and rear-tire at same time about 15cm) and fly 2-3m smoothly up to the footpath without slowing down..

but with an 22-24kg e-bike ?!?

so with this gruber-drivetrain the bike would stay a sports-toy and not become a bike with seniors-bike-character..
you understand what i mean ?

the GHOST HTX 7500 on the Gruberwebpage with the motor AND batteries would be ~13,5kg !!!! impressive !!!


on the other hand, iam also sceptical...
200Watt input doesn´t sound much, but brought down this 200Watt to only 60-100rpm is some MASSIVE torque !
and this massive torque in a tranny mounted inside a 31mm tube (i guess: its planetary gears...)
i wonder how long this would hold ?!?

and then there is the price...
~1800Euro for the NiMh-version
~2000Euro for the LiIon-version
thats - well - i think a little too much... (well: far too much)

high-end-brushless-motors in this size costs around 80-150 Euro
controller for 200Watt (seems to be sensorless, no need to spin the bike from start up (its forbidden because it would burn the motor/controller), only a slow-up function) should not cost more than 150 Euro
the batts are also not that big/heavy and for that not that price

so there are 1000Euro left...

1000Euro for the (planetary?)gears and the last gear-stage..
seems to be overprized too me

nevertheless.. i like the idea very much..

 

[kraeuterbutter]

funny:
when looking at the list of shops who sells this i found 1 shop here in vienna..
and when looking on the map -> voila: only 370m away from my flat were i live

so i will go to them next days... would be wounderfull if they have one there to put my fingers on or even testride one

 

[flecc]

It is true what you say about "normal" electric bikes, and like you, I favour a centrally mounted motor.

However, I don't see any chance of saving weight over current systems. That motor is very small and not at all powerful compared with what I normally use, and I think 200 watts is a bit optimistic. As you know, there's a strong relationship between weight and power in electric motors, and electro-magnetic laws can't be just swept aside for advertisers and optimist's convenience, so there's going to be very little saving if any on motor weight.

The spiral bevel gear drive is much heavier than having an output chain sprocket like the Panasonic system, so a weight gain there

Battery weight is the same whatever motor disposition there is, so no change there, and the same goes for bike weight, that fixed by the strength required. I also think noise could be a problem, compared with the best normal systems.

In other words, whatever that does can be done by normal systems, those having big advantages in terms of accessibility for maintenance etc., and for a central drive I prefer the Panasonic style arrangement. The motor casing there replaces the frame's bottom bracket area and provides that strength so adding hardly any weight. For example, The Giant Lafree Twist was about 22 kilos including full road equipment, dynamo, lights, mudguards, heavy duty carrier etc, and in it's US stripped version under 20 kilos with it's 6.5 Ah 4.2 kilo NiMh battery, so very close to normal bike weights.

With the latest 10 Ah Li-ion battery weighing 2.2 kilos, that would have been down to only a bit over 17 kilos if still made, light enough for us I think.

P.S. Just seen your latest post and look forward to your impressions.

Also see here from last September:

BB Drive
.

 

[kraeuterbutter]

hi flecc..

yes.. from technical standpoint (many many involved gears, small fast spinning motor -> but low rpm needed) makes this all not ideal..
than the noise.. nono..

the cool thing is, how invisible the motor is mounted..
and also not bad, how light the whole thing is..

i think there is at least no Hub-motor-unit with that small weight compared to the Gruberass (approx. 775 g Motor and tranny + 125g the controller)

of course: you can combine every electric bike on the market with a small battery..
BUT:
1.) a small battery on a motor with sucks 500Watt+ peaks is mabye not that good
2.) you never want to become the battery empty.. for sure not on a bike with "regenerative braking", a bike without freewheel unit

so: i would say: on most bikes its not possible to use small batts, because you never want to run out of juice
for bikes-weight: yes you are right.. on the other hand:
when i go through the 2006 and 2007 test of most common european electric bikes there was non with less than 19kg (the 19kg was a 20" folder), all over 20kg

As you know, there's a strong relationship between weight and power in electric motors, and electro-magnetic laws can't be just swept aside for advertisers and optimist's convenience, so there's going to be very little saving if any on motor weight.

here i would see the relation a little other way..
not the weight is connected to power, but more the rpm..

here a very exiting example from rc-modell-world:

here are even videos of it:
Mark's Paragliding Pages |Paragliding Videos|News|T-shirts/Merchandise|

this is a real, man-carrying paraglider, using a motor from rc-modelworld:
the motor weights only 1.5kg (so less than most bicycle-hub-motors)
power ? 17hp !!!! continouse
for short burst a lot more

so you see: weight can not be the only thing why you need big hub-motors..
when a 1.5kg light motor can do 17hp,
i guess a 150g light motor (1/10 weight) should do 170Watt (1/100 power) easily..

the problem is: RPM...
in a bike you need slow rpms --> tranny, gears, noise, looses, arghhhh !!!!
for that the hub-motors have benefits...
on the powerside at that low rpms they are realy weak

besides, same thing: small motor, huge power: YouTube - electric trike


sorry: i have to show just one singe additional pic:

just for size comparision:
thats a Predator30 from Plettenberg, used in bigger RC-planes..
motorweight: 1.55kg
Power: 11.000W
its not that big.. nor is it realy heavy

some data: at 50volt (the maximum in Europe we rc-modellers are allowed to use) and 169A current it turns with 6500rpm at 89,2% efficience (controllerlooses already included) given a trust of 27,5kg for the plane

 

[Miles]

thats a Predator30 from Plettenberg, used in bigger RC-planes..
motorweight: 1.55kg
Power: 11.000W
its not that big.. nor is it realy heavy

But, alone, it costs more than most electric bikes

BTW, isn't that a Terminator in the pic...?

 

[kraeuterbutter]

indeed.. you are right..
the predator would be a little bigger and 500g heavier..
the Terminator has only - i think - 920g

however: of course, the price is very high (nevertheless cheaper than this 2000 Euro Gruber-thing )

just wanted to say, that for the weight more power than hub-motors in current e-bikes provide is possible
but ok: we see this already in Scooters.. the hub-motors there are barrley bigger or heavier, and nevertheless can do over 2kw

 

[Miles]

Sure, the problem, as you say, is that the Predator needs to be running at more than 5000 rpm to get that power. So, for a BB drive you'll need 60:1 reduction....

 

[kraeuterbutter]

yeah.. not power is the problem... rpm is..

and gearing of 1:60 single stage is barley possible ;(
and always combined with noise

i hope my trailer will work with single gearing...
it has only 16" wheel, so the wheel spins faster --> good

motor: i think i will try first something like this, because with 40$ its VERY very cheap
https://www.unitedhobbies.com/UNITEDHOBBIES/store/uh_viewItem.asp?idProduct=4569
brushless, 1600Watt max,
Size: 51mm Diameter x 89.2mm Length
Weight: 425g
Constant: 352Kv !!!

so for 30km/h and a single 1:10 gearing (i can do this by a chain or quiet belt) the motor needs to run with 3800rpm
and that can be done with 3s Lipo at 11V
so with only 20A i should get my 100-150Watt Power to the wheel
so with my 3s 14Ah Konion-pack i should get at least 45min of additional power.. great..

 

[Miles]

352kv....

I would have thought this would be a better candidate?
https://www.unitedhobbies.com/UNITEDHOBBIES/store/uh_viewItem.asp?idProduct=5142

I think inrunners are better for ebike situation, though...

 

[kraeuterbutter]

*gg*
yeah.. thats a monster...
still -> compared to some hub-motors not realy that heavy...

but no, i hope that the 350g light motor would be enough...

in the moment i have already some projects in mind..
another one is this:
powercroco 24N28P 6530

it has an kv of only 77rpm/Volt
and was specially designed and build for use in a bicycle..
so: when i have more time i think i will maybe try this...
maybe it can be brought to even less rpm with more windings...
with 1kg its the most i would want as a motor... lighter would be nicer

 

[Miles]

I had lengthy correspondence with Dr Okon, 2 years ago, on this subject...

 

[Miles]

Did you see his conclusion?

ES LOHNT DIE MÜHE NICHT!

 

[kraeuterbutter]

you speak German ?
well.. he fixes his comment for example on the fact, that batteries are too expensive..
720 Euro
well to face this: i personally do not need a battery for 50km..
two DEWALT-A123 Fepo4 packs with 36V and together 4.6Ah with 1450g weight
would cost me together only 200 Euro (and would last years and most likely more than 1000cylces)
should give enough power for 1-2hours of assistance

for the sensorless controllers: as said, when iam driving on a hill an notice that i need assistance i hit the throttle.. so no starting from stand-still needed for me
-> so also the controllerargument is no argument for me

 

[Miles]

I didn't say I agreed with his conclusion

Incidentally, if you're looking for a servo tester, I'm quite pleased with this one: Product Information - Batteries Servos & Accessories for Electric Flight available at BRCHobbies.com It's handy to have the readout when testing motors.

 

[mk1]

funny:
when looking at the list of shops who sells this i found 1 shop here in vienna..
and when looking on the map -> voila: only 370m away from my flat were i live

so i will go to them next days... would be wounderfull if they have one there to put my fingers on or even testride one

kraeuterbutter, are you still going to have a test ride?. The Gruber doesn't sound very powerful on paper but I would be interested to to know what it's like anyway.

Martin

 

[kraeuterbutter]

hello..
yes, i want to visit them soon..
iam not at home in the moment, so no possibility in the moment..

but i fear: this shop will maybe have the possibility to order a set, but maybe not a set IN the shop for testing..