The Grin All-Axle Hub Motor

The Grin All-Axle hub is a direct-drive motor series we designed to be universally compatible with all the varieties of quick release and thru-axle mounting standards that exist in the bike world these days. It solves the compatibility problem between hub motors and modern bicycle frames, it provides the benefits of direct drive without the traditional heft, and simplifies the installation with integrated torque arms. 

Features

The All Axle motor has the following characteristics:

• 4.0 kg motor weight (vs >6kg for comparable generic DD motor)
• 0.35mm Laminations for low motor drag when pedaling unassisted
• Integrated Torque Arm with secure fork mounting clamp
• Fits All Front Fork Standards (regular quick release, QR12x100, QR15x100, QR15x110 Boost, QR15x150 Fatbike, QR20x110
• Fits Most Rear Fork Standards (135mm quick release, 12x142 Thru Axle, 12x148 Boost Thru Axle)
• Compatible with Single Side Installation on many trike and quad vehicles
• Uses 32 Spoke Holes for vastly more in stock rim options
• 18mm Disk Caliper Clearance fits most (but not all) calipers without spacers
• Statorade Compatible with side cover injection port
• Available in both metallic silver and black anodized finish
• Designed and Assembled in Canada

Rear Freehub and PAS

The Rear All-Axle motor uses a Shimano HG compatible mountain freehub allowing for easy use with 8, 9, 10, and 11 speed mountain cassettes. Inside the freehub body we've also secured a 12 pole quadrature PAS encoder ring for pedal assist applications. This sensor provides almost immediate engagement of pedal assist and permits back-pedal regenerative braking, all without having to add a separate crank sensor. The PAS feature is brought out through a 6 pin HiGo connector, and we include a long HiGo->5 pin JST extension cable to plug in directly to a V3 Cycle Analyst.

Do note that since the PAS sensor is on the rear cassette and not the cranks, the Cycle Analyst will be showing wheel RPM rather than cadence on the human power screen.

Front Axle Adapters

The stock front Grin motor axle is 95mm long with a 20mm hollow center, and then uses a series of axle inserts and end caps to accommodate different installation geometries

Rear Hub Adapters

With all of these adapters, a separate torque arm is installed on the right side of the motor axle. A mating frame clamp secures to the fork blade with a pair of hose clamps and the two parts or locked together with an M5 bolt. When the motor needs to be removed, this bolt is loosened and then the arm can slide freely downwards as the wheel is taken off.

Motor Speed

The Grin All-Axle Motor is currently produced with three different windings; a slow 8 turn stator, a standard 6 turn stator, and a fast 5 turn stator. All three motor winds are capable of producing exactly the same torque and power outputs so the recommended motor model depends on youre desired vehicle speed. The faster wind motors are more appropriate for small wheel diameters and/or lower battery voltages, while the slower motor winds are more common with larger wheel sizes and higher battery voltages.

The following table shows the unloaded speed of each motor winding at common battery voltages in 20" 26", and 29" (700c) wheel sizes.

The top speed under any kind of load is going to be less than this value, and we recommend using our motor simulator for exact performance details of any given combination of motor, battery voltage, and controller model.

Motor Power

The Grin motor uses a 27mm wide 205mm diameter stator and has similar continuous power and torque capabilities as other direct drive hub motors with this size. However being optimally designed for weight reduction it has less metal mass to absorb heat. Under heavy loads the core temperature will rise at a faster rate than you would see on an otherwise identical but heavier hub, and for those reasons we recommend Statorade in the motor when used in more demanding applications.

The table below shows both the continuous and 5 -minute power capability of the motor at various RPMs with and without Statorde motor coolant.

For a more detailed understanding we recommend using our motor simulator or trip simulator applications to properly predict the capability of this motor in any specific usage scenario.

Single Side Applications

A unique feature of the front All-Axle hub design is its ability to work in applications requiring a single side mount. This allows the side wheels of trikes and quads to be readily electrified for the first time, and is especially popular with tadpole trikes running an internal gear hub rear wheel.

Unlike front bicycle forks where there are industry standards (admittedly a lot of standards, but standards at least), the wheel mounting strategy on trikes is all over the map, and unique adapters are required for most vehicle models. We've taken the approach of using the disk caliper mount as an anchor point to hold the wheel and lock the axle against rotation.

One Side or Both?

A trike with dual Grin hub motors can be insanely powerful and will be able to rocket up the steepest hills with amazing efficiency, but it is also quite expensive to do a full conversion with two specialized motors and motor controllers. You can also run a tadpole or delta trike with just a single side wheel motor and leave your original wheel on the other side. In general this does not result in any lopsided steering or handling issues and allows for a ligher weight and more economical conversion.

Wheel Lacing

Unlike most hub motors, the All-Axle uses 32 spoke holes rather than 36 spoke holes in order to fit the much larger availability of 32 hole rims. The spoke holes are paired sufficiently close that there is NO NEED to have the spokes cross over. With a radial lacing the spokes have an effective angle that is the same as a regular hub with a triple cross. That said, you are free to do a single cross lacing if you prefer the look.

One not-so-obvious detail is that the spoke flange of the All-axle motor is designed for the spokes to be laced with the elbows in and the head facing outwards. The flange has a couterbore for the spoke head on the outside, and is wide enough apart (49mm, vs 25mm for typical motors) that there is sufficient triangulation with all spokes elbows in. If the wheel is laced with the spoke elbow facing outwards, it results in a bending force on the flange that pushes the entire center of the side plate outwards by 1-2mm. This can result in the motor axle developing play to slide left and right. 

Differences between V1 and V2

The original V1 All Axle hub motor was in limited production from 2013 until early 2019 and used a large 45mm ID thin section bearing on the side covers. This allowed for a generous amount of room for the heavy gauge phase wires to pass through the axle, but the thin section ball bearings could have short lifespans in setups with frequent exposure to the elements.

In the spring of 2019 we released an updated V2 Grin motor design based on feedback and experience. This updated model has the motor cable exiting on the disk side of the motor rather than the non-disk side to facilitate single side installations, and it uses a wider 35mm ID ball bearing standard with a custom tooled lip seal to prevent ingress and egress. These changes increased the overall motor weight a small amount, but the improved robustness and versatility was worth it.

In addition to the mechanical changes we also updated from N35 to N40 grade magnets. Stronger magnets allow the motor to produce more torque for hill climbing with less heat loss, but they also increase the drag of the motor when riding without power. In our original design we erred on having lower rolling drag because at the time we felt this was more important than efficiency on hill climbs, but the Virtual Electronic Freewheeling feature in the Phaserunner/Baserunner controllers has shifted the balance and we switched to a higher strength magnet.

As a result the V2 motors spin about 5% slower than the V1 models. They have about 10% more drag torque but they can also climb hills with 10% less heat generation.

Technical Specifications

Videos

Background

The All-Axle motor has been a long development project for Grin to produce a direct drive hub motor that was lightweight and compatible with all Thru Axle and quick release fork standards. The idea first took roots in 2010 when we were impressed with the performance of large diameter direct drive hub motors being imported from china, but increasingly frustrated with the poor mechanical tolerances and bike fitment. While prototyping these mechanical improvements we also saw considerable opportunity to reduce the mass of the hub without affecting the torque output.

These earlier videos filmed from Ken (owner of a Calgary based ebike store) as he was passing through town in 2010 show the early development and thought process:

Since then we've gone through a number of design revisions, enhancements, mold toolings, and several pilot production batches while working out many kinks along the way. The hub was really put to the test in several touring trips (such as 2013 cargo biking Vancouver to San Francisco, and the 2018 Sun Trip solar bike race) and has finally come of age in 2019 with the V2 model when we switched to a wider and more rugged bearing, cable exit on the disk side, and a move to o-ring seals rather than silicone sealant for the side plates and screws for more consistent mass production and easier servicing. 

Marine Motor

We are actively developing a Marine version of our All Axle motor for people interested in electric sailboats conversions. The ~4kg motor can directly replace a much more massive diesel engine, and it is perfectly matched to drive the shaft 1:1 with no transmission required. Our standard width Grin motor with a 27mm wide stator can effectively replace an 8 horsepower engine, while a fatter 45mm stator option could replace a 12 hp diesel. This should broadly cover most sailboats with the 24-32 foot realm, or larger vessels if you don't mind being under powered.

We are planning to do a pilot launch of this motor in summer 2021 and are currently looking for potential pilot customers in BC lower mainland or Vancouver Island. Ideally these are people who have an existing sailboat with an inboard engine that is due for replacement, and with the drive shaft still in place. If that situation rings a bell and you have a strong interest in going electric, please fill out the google form below:

Where to Order

The Grin All Axle hub motors are available in stock at our shop in Vancouver and also sold through dealers all over the world, including ebike-solutions in Germany, Declic-Eco in France, BikeToTheFuture in Switzerland, and BikeSwift in the USA

All-Axle Motors from Grin's Online Store

Full All-Axle Conversion Kits from our Online Store