[Jason]

BIMMERPOST NEWS

BMW i patent powers eBike. Innovative drive unit swing arm goes into production at the Pedelec factory HNF Heisenberg.

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July 27, 2015

Munich/Biesenthal. BMW i stands for visionary vehicle concepts, progressive design and a new understanding of premium that is strongly defined by sustainability. Furthermore, BMW i also fulfills the function within the BMW Group of an incubator for innovation that reaches far beyond the vehicles BMW i3 and BMW i8 we are already familiar with.

The patent for a drive unit swing arm, which is now entering production at the HNF eBike factory after development to series maturity in collaboration with BMW Research and Technology, originates from the first stage of BMW i market research and the early concept phase.

As there was no longer any immediate use for the patent due to the focus at BMW i on two-track electric vehicles, it has now been finally released for external usage.

Its application in reality can now be experienced on the eBike “Heisenberg XF1”, on which a small logo with the wording “Concept by BMW i“ indicates the prestigious origin of this innovative functional principle.

________________________________

The drive unit swing arm is a new kind of frame technology for full-suspension eBikes featuring a mid-motor. The concept allows the drive train, which was previously firmly attached to the main frame, to float freely, eliminating the need for the conventional chain tensioner. This permits for the first time the combination of a rear suspension and the durable, maintenance-free carbon belt drive on full-suspension eBikes, resulting in outstanding propulsion and handling characteristics.

The BMW i patent for the drive unit swing arm principle facilitates for the first time the integration of mid-motor, gears and belt drive into an innovative suspension module, thereby dispensing with a belt tensioner.

The HNF Heisenberg development team designed the new suspension technology for the XF1 in a very specific way. The kinematics are fully integrated above the mid-motor, connecting it securely to the frame. To ensure consistent spacing of the low-maintenance carbon drive belt between the spindle and the rear hub, the mid-motor and rear hub are integrated into the drive unit swing arm. The belt runs under tension and perfectly aligned between both toothed belt discs and is able to effortlessly transfer even high peak loads from the mid-motor.

In accordance with the principle of four-joint kinematics with a virtual rotary axis around the spindle, the BMW drive unit swing arm is guided in such a precise way as to prevent the relative position of the mid-motor spindle unit from deviating in relation to the main frame. In conjunction with the shock linkage, this swing arm connectivity facilitates long spring travel of up to 150 mm on the rear wheel. One of the dynamics-related advantages of the drive unit swing arm is the fact that it functions without recoil from the pedal. Compared with other rear-mounted suspension concepts, which are specifically optimized for muscle-powered drive systems, there is no stiffening of the rear swing arm when the electric motor is providing a high degree of assistance such as during acceleration, constant travel at high speeds or on hills. The suspension can respond sensitively at any time, ensuring excellent grip and high traction. As the proportion of human driving force is relatively small, there is no unpleasant rocking movement when accelerating or breaking. Even in the event of extremely uneven terrain it is possible to pedal smoothly and efficiently.

From the summer, the HNF Heisenberg XF1 will benefit from the following advantages of the BMW i 4-joint drive unit swing arm:

• Mid-motor and even axle load distribution
• Maintenance-free belt drive with hub gear, without chain tensioner
• Highly stiff frame
• No pedal recoil
• Grip and traction in all riding situations, as there is no stiffening of the rear arm swing
• Possibility of implementing a modular drive system
• Freedom in the design of the main frame

About BMW i

With BMW i, the BMW Group is pursuing a holistic approach: With tailor-made vehicle concepts, a strong focus on sustainability along the entire value chain and a whole string of supplementary services, BMW i is redefining people’s understanding of individual mobility.

About the HNF GmbH

The company, which was established in Biesenthal near Berlin in 2014, develops next-generation eBikes with a direct service and sales concept offered under the brand name HNF Heisenberg. The founders are Michael Hecken, Karlheinz Nicolai and Benjamin Börries.

The eBike pioneers Michael Hecken and Karlheinz Nicolai had already established the Grace GmbH in 2008 and were commissioned by the Daimler Benz AG to develop the smart bike. HNF Heisenberg – their new future-oriented brand for an increasingly technophile public – will commence on xx.07.2015 with a model series ranging from the S-Pedelec city bike to the top-of-the-range full-suspension mountain bike.

[aveillez]

BMW Bike technology !

[VCP]

Want!

[T_F30]

I definitely like that idea! Cool looking bike as well!

[nieko]

let me guess the price.
>10 000 ?

[bradleyland]

Looks pretty cool, but appears that it would be heavy compared to a traditional full-suspension setup. The reinforced baseplate that the rear sub-frame mounts too looks like a real behemoth as far as bike parts go. Then again, you're going to be hauling around a sizable Li-Ion pack and electric motor, so the weight added by this system is probably trivial in proportion to the electronic drive components.

This is the cool part:

"In accordance with the principle of four-joint kinematics with a virtual rotary axis around the spindle, the BMW drive unit swing arm is guided in such a precise way as to prevent the relative position of the mid-motor spindle unit from deviating in relation to the main frame."

In plain ass english, the geometry of this suspension is set up so that the rear swing arm rotates around the electric motor's spindle. This is important since this is also where the crank connects. Hence, the crank won't be jarred by bumps in the road/trail. You can get this in an electric mountain bike already, but you have a standard chain derailleur, which also functions as a tensioner. That's the real innovation here: you can use this with a fixed drive system and no tensioner.

Which brings us to this: this is a fixed ratio driveline. I guess when you have electric assist, you don't need the lower gears to get started, you simply use the electric motor for torque assist, then rely on human power at speed. Language in the write-up seem to support this:

"As the proportion of human driving force is relatively small, there is no unpleasant rocking movement when accelerating or breaking."

For a mountain bike with FS, this seems really optimistic though. When you're on an uphill, you need a lower ratio. There's just no way you're going to make it through a sizable ascent on the ratio pictured in the press photo. The battery pack will be depleted in no time. If you're just going to ride around a city, then why bother with FS at all? I would venture that you're better off saving all the weight and complexity, going with a rigid rear frame.

Never the less, this is a really tight looking design, and having a modular rear swing arm means that manufacturers could afford to offer this system on a much wider range of cycles

EDIT: I looked in to this "Carbon Drive" system, which I wasn't familiar with before. It looks like they use internally geared hubs to achieve variable ratio drive. Seeing that my price ceiling for a MB is around $3,000, I never really shop the upper end of the scale where this stuff sells. Mea culpa.

[drexplode]

Bosch has an E-bike system on the market for years now:

http://www.bosch-ebike.de/en/home/home.html

[bradleyland]

Originally Posted by drexplode

Bosch has an E-bike system on the market for years now:

http://www.bosch-ebike.de/en/home/home.html

That's not what the "innovation" is here. There are tons of e-bike makers. The innovation here is in the modular suspension unit. The problem here is that BMW's press department packs so many buzzwords in to their releases that no one has any clue what they're talking about.

[Bosozoku]

So is Tom Cruise going to destroy this too?

[T_F30]

Originally Posted by bradleyland

Looks pretty cool, but appears that it would be heavy compared to a traditional full-suspension setup. The reinforced baseplate that the rear sub-frame mounts too looks like a real behemoth as far as bike parts go. Then again, you're going to be hauling around a sizable Li-Ion pack and electric motor, so the weight added by this system is probably trivial in proportion to the electronic drive components.

This is the cool part:

"In accordance with the principle of four-joint kinematics with a virtual rotary axis around the spindle, the BMW drive unit swing arm is guided in such a precise way as to prevent the relative position of the mid-motor spindle unit from deviating in relation to the main frame."

In plain ass english, the geometry of this suspension is set up so that the rear swing arm rotates around the electric motor's spindle. This is important since this is also where the crank connects. Hence, the crank won't be jarred by bumps in the road/trail. You can get this in an electric mountain bike already, but you have a standard chain derailleur, which also functions as a tensioner. That's the real innovation here: you can use this with a fixed drive system and no tensioner.

Which brings us to this: this is a fixed ratio driveline. I guess when you have electric assist, you don't need the lower gears to get started, you simply use the electric motor for torque assist, then rely on human power at speed. Language in the write-up seem to support this:

"As the proportion of human driving force is relatively small, there is no unpleasant rocking movement when accelerating or breaking."

For a mountain bike with FS, this seems really optimistic though. When you're on an uphill, you need a lower ratio. There's just no way you're going to make it through a sizable ascent on the ratio pictured in the press photo. The battery pack will be depleted in no time. If you're just going to ride around a city, then why bother with FS at all? I would venture that you're better off saving all the weight and complexity, going with a rigid rear frame.

Never the less, this is a really tight looking design, and having a modular rear swing arm means that manufacturers could afford to offer this system on a much wider range of cycles

EDIT: I looked in to this "Carbon Drive" system, which I wasn't familiar with before. It looks like they use internally geared hubs to achieve variable ratio drive. Seeing that my price ceiling for a MB is around $3,000, I never really shop the upper end of the scale where this stuff sells. Mea culpa.

Very nicely explained there, I am certain many appreciate that effort!

[hmd5859]

Nice as always, but I am sure its going to have the typical BMW price point of a Bazillion dollars or some insane price for a bicycle. But nice to see the forward thinking.

[WAY]

This has a maximum range of 130 km and is priced from €8,345 ($9,235).

[bradleyland]

Originally Posted by hmd5859

Nice as always, but I am sure its going to have the typical BMW price point of a Bazillion dollars or some insane price for a bicycle. But nice to see the forward thinking.

Heh. Checked prices on any FS e-bike lately? You'd think they were all made by Rolls Royce.

[scrammer]

Quote: In accordance with the principle of four-joint kinematics …

Looks and sounds a lot like the DW Link or VPP already in use in MTB

http://bicyclingaustralia.com.au/med...---DW-link.png

[BananaCar]

My guess $5499usd

[raysspl]

[DriveHard]

Wait. Look it has a timing belt as a drive belt to the rear wheel.

I guess they learned there lessons about CHAINS!!!!

Nice looking bike though!

[atg4]

Originally Posted by DriveHard

Wait. Look it has a timing belt as a drive belt to the rear wheel.

I guess they learned there lessons about CHAINS!!!!

Nice looking bike though!

I fail to see the lesson here...

[bradleyland]

Originally Posted by scrammer

Quote: In accordance with the principle of four-joint kinematics …

Looks and sounds a lot like the DW Link or VPP already in use in MTB

http://bicyclingaustralia.com.au/med...---DW-link.png

Only similarity is in the fact that they both use two-link geometry. Otherwise, the geometry is completely different. All (well, most) two-link setups have the same goal: to move the center of rotation to a location that would otherwise be difficult or impossible. BMW i just happen to have an application that moves the center of rotation to the motor spindle, which has obvious benefits in this case.

[bradleyland]

Originally Posted by DriveHard

Wait. Look it has a timing belt as a drive belt to the rear wheel.

I guess they learned there lessons about CHAINS!!!!

Nice looking bike though!

Originally Posted by alexandertg21

I fail to see the lesson here...

I'm curious what the lesson is too? Chains are incredibly well tested and reliable components. They can be noisy, but if you keep your drivetrain adjusted, they're quiet enough that I don't even notice the noise on most surfaces. When things get really bumpy, you can end up with a bit of slap in the higher gears, I suppose. You don't get that with a chain. Another advantage of chains is field repair. You can pack a small kit to repair a chain in the field.

[scrammer]

Originally Posted by DriveHard

Wait. Look it has a timing belt as a drive belt to the rear wheel.

I guess they learned there lessons about CHAINS!!!!

Nice looking bike though!

BMW likes chains …

Camshaft drive
As in the S85, the inlet camshafts of the S65 are driven by chain drive and the exhaust camshafts are driven by a gearwheel drive. This means that the inlet and exhaust camshafts always have an opposite direction of rotation. In contrast to the S85, which works with two single-roller
chains between the crankshaft and the inlet crankshafts, in the S65, two double-roller chains are installed. This is because of the higher chain drive load in the V8 S65.

[larryn]

I was thinking it was reclaiming power (charging) by the movement of the suspension components, similar to how it is currently done in eVehicles during braking. Their wording on kinetics threw me off.

I'll give this a personal meh on the innovation scale. I like my idea better.