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Grin Magic Drive

Hummm?... "Now I see", says the blind man.

All that's needed now is the implementation of AI wireless coupling to monitor, control and log all bicycle modifications & usage (ala Tesla). "WTF!",.. "I just receive a summons via text that requires me go to court for tampering with... and speeding on my bicycle!"
 
It's pretty frickin' rude to use the website that Grin funds to post a message about hoping China undercuts Grin.
We don't have a rule against it and it's not my job, nor interest, to play brand police for anyone.

But damn, guys.. 😤
 
Grin isn't building these motors as far I know. The only way they will be made available for diy is from China. The Grin video even specifically states that they are not making any motors using this technology. The facts are if you want this technology in a time frame that isn't years away, China is the only one capable of doing it so everyone can enjoy it not just a privileged few
 
Last edited:
I wasn't trying to pick on grin specifically. I also believe we should all be driving Chinese electric cars because they do it better and cheaper than any domestic manufacturers. Those mid drive videos they are building none user repairable high-end mountain bikes that only doctors can afford.
 
neptronix said:
In the video, they are taking pre-orders. So they have some horse in the race.

Pre-order form:
Rear motor: https://ebikes.ca/ebike-parts/hub-motor-stuff/motors/magic-drive-deposit.html
Front motor: Pre-Order - Freegen Motor


Looking at the front motor, i see they claim the motor freewheels well. They don't make the same claim on the rear.
No idea on the final price is.
I'm inquiring for details.
Click to expand...
Those are hub motors, though, and DJI/Gobao have mid-drives. Very, very different. In fact, it could be just the thing to push me over the prebuilt bike market fence, because the benefits this would offer (especially with a belt instead of a chain) are just so massive.
 
Personally..
I'd never go with a proprietary drive, even if it was awesome.
I already have a 1.6kg 1.1kw continuous mid drive addon kit, so it would take a lot to tempt me to the dark side.
Interested in seeing a better hub :)
 
I'm disappointed that the rear Magic Drive motor is only available for pre-order for 140mm dropouts. All of my machines use 135mm.
 
Info i got back:

Should be based on Shengyi SX2
Motor cost may be around that of all axle motor
Motor kit should have controller and accessories at a minimum

Freewheeling?
If it's mounted for freegen braking, then we need to put a freewheel on the crankset or rear cog and as a result of that the motor itself freewheels fine when you stop pedaling. The planet carrier will spin and the motor will be stationary. But in the implementation shown in this video, when you stop pedaling the planet carrier stops too, which mean that the motor is still rotating and sucking up some energy due to the core losses.

Okay, so it can do both. I'm inquiring on what freewheel interface we have; the all axle is limited to 16T, and this would require beyond a personal pizza size chainring to keep up with; hope this is not the same case.

The Toecutter said:
I'm disappointed that the rear Magic Drive motor is only available for pre-order for 140mm dropouts. All of my machines use 135mm.
Click to expand...

Not too big of a stretch for 135mm dropouts, which are usually ~138mm uncompressed. If that's the case with your dropouts, each fork leg only needs to move 1mm.

Put a caliper to yours and let me know what you see. I saw 138mm on my modern bike. Almost feel confident to hook a 142mm hub up to it..
 
neptronix said:
so it would take a lot to tempt me to the dark side.
Click to expand...
I'm mostly in a similar boat, but I maintain that enclosed drivetrain, integration of continuous "shifting" with the motor electronics, and light and simple rear wheel with straight chain - that is a lot.
 
neptronix said:
Okay, so it can do both. I'm inquiring on what freewheel interface we have; the all axle is limited to 16T, and this would require beyond a personal pizza size chainring to keep up with; hope this is not the same case.
Click to expand...
Not if i understand the 2 vids i scanned.. you only need maintain + pressure on the pedals and provide speed input via the twist grip. the motor will accelerate upto its designated rpm (throttle wise) and the planetary gear set will 'back off' to meet your foot force so a 36t chainring will be ample to rotate the chain, it just needs to be under tension to go and the more tension applied the less motor input, as your input pushes back into the gearset with the throttle twist grip governing the optimum speed that both you and motor contribute to.

the toddler trike approach to braking however is a concern. though that leaves the braking by 'wire' rather than cable or pressure, which is not something i would welcome due to its necessary complexity- also while the regen braking on the test bike was at the rear wheel 70-80% of a sensible riders braking is at the front, disproportionate rear braking just results in skids and less control as we all know. I appreciate the one hub solution is neat and tidy and easy to sell - but a 2 hub solution 1 x drive at the rear and 1 x regen dynamo at the front might have some milage and be a more natural progression for most ebikers.

EDIT- Oh yeah extra mass and 2x the motor cost - perhaps not then..
 
Wish the Gobao didn't require a custom frame. If any mid drive is going to tempt me away from the ease of motor hubs, it isn't going to be one that requires a custom frame to bolt it in:
Screenshot_20260626-091429.png
I found even replacing my bottom bracket for the Efneo gearbox annoying. Gobao didn't even use a "standard" like for Bafang or Shimano AFAICT. So I can't get a cheap used/broken Bafang frame ready for whenever they eventually actually sell it.

People are saying in the https://www.emtbforums.com/threads/gobao-ecvt-emtb-mid-drive-motor.47672/ thread that the chain tensioner means no regen as well:
Screenshot_20260626-091445.png

Feels like some overly complex solution for mountain bikes at this point. I've had plenty of IGH hard tail and city bikes that didn't need a chain tensioner.
 
neptronix said:
Put a caliper to yours and let me know what you see. I saw 138mm on my modern bike. Almost feel confident to hook a 142mm hub up to it..
Click to expand...
I did when I originally installed my Leafbike 4T in a 26" wheel in 2020. It didn't fit, so I had to see what was up. The Leafbike fits 137mm dropouts, and when I measured them, they were exactly at 135mm. I have to pry them open with a screwdriver to fit that motor onto my KMX frame. Removing the motor, they reset back to 135mm and I'd have to pry them apart again if I wanted to re-install either the 3T or 4T version of that motor again. When I fit the differential/rear end on it converting it into a quad, everything fit right up as it was made for 135mm.

140mm might fit if I permanently altered the dropout width with a scissorjack, but I'd like to avoid doing that.

I'll see how this motor fares in the hands of others before I experiment with it. I'm very curious what it can reliably do regarding peak power as well as how pedalable it is on disabled electronics.
 
Its always exciting seeing new stuff come to market like this. I have always appreciated how Justin continues to chase new ideas.

I am trying to wrap my head around what the motor control strategy would be like here. Seems to me there would always need to be some motor torque from the controller to keep the pedals from counter rotating the motor. Is this correct? Would this system pedal home with no battery power?
 
Not just by a mid-drive, but by an eCVT mid-drive with two electrical motors inside so there are at least 3 electrical motors on your bicycle.
 
fill said:
Not if i understand the 2 vids i scanned.. you only need maintain + pressure on the pedals and provide speed input via the twist grip. the motor will accelerate upto its designated rpm (throttle wise) and the planetary gear set will 'back off' to meet your foot force so a 36t chainring will be ample to rotate the chain, it just needs to be under tension to go and the more tension applied the less motor input, as your input pushes back into the gearset with the throttle twist grip governing the optimum speed that both you and motor contribute to.
Click to expand...

Ah you're right. See, i'm thinking about what is happening if we have the power off and we still want to pedal ( frequent case for me, i always turn the motor off and keep pedaling ). In that case you have no cvt, so i imagine you're on one gear..

fill said:
the toddler trike approach to braking however is a concern. though that leaves the braking by 'wire' rather than cable or pressure, which is not something i would welcome due to its necessary complexity- also while the regen braking on the test bike was at the rear wheel 70-80% of a sensible riders braking is at the front, disproportionate rear braking just results in skids and less control as we all know. I appreciate the one hub solution is neat and tidy and easy to sell - but a 2 hub solution 1 x drive at the rear and 1 x regen dynamo at the front might have some milage and be a more natural progression for most ebikers.
Click to expand...

I imagine you can turn that off or use a freewheel.
 
TPEHAK said:
Not just by a mid-drive, but by an eCVT mid-drive with two electrical motors inside so there are at least 3 electrical motors on your bicycle.
Click to expand...
I think hillslayer@ needs two hub motors, a crank mid drive, a left side mid drive, two wheel friction roller drives, and a micro turbojet. Piggyback trailers for the batteries.
 
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