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Posts Tagged ‘BMW’

Electric motorcycles and scooters, as the type name implies, run on electricity. Obviously, the two wheelers don’t have a very long extension lead plugged into a socket, but instead they run on batteries.

But normal 12V motorcycle batteries as we know them will not supply enough power to propel the bike any further than a mile or two. No, to be able to ride a reasonable distance on an electrically powered two wheeler, you need more batteries, and these batteries need to have a higher energy.

Take for example one of the top American electric motorcycle manufacturers, Brammo. This is what a Brammo will look like if you cut it open:

Brammo-Batteries-1

Those blue things are the batteries. They are Lithium-Ion batteries, and they are not 12V but 103 Volt (with a max voltage of 117.6V). They supply a total capacity of 9.31 kWh, with a peak of 10.2 kWh.

Brammo-Batteries-2

It’s the battery pack capacity that counts for electric motorcycles. The higher the number, the more power it has.

But to recharge so many batteries requires special equipment. Depending on where you plug your bike in (known as Level 1, 2 or even 3 charging) you can fully charge your bike in 3.5 hours or 8 hours (in the case of level 1, your household electrical socket).

But all those batteries make the bike heavy. If you look closely at the photos, you’ll see that the engine is the smallest part, in sharp contrast with its ICE (Internal Combustion Engine) cousins. The biggest volume is taken up by the batteries. In total, the Brammo Empulse weighs 460 lbs (some 213 kilos).

But despite the heavy weight, the Brammo can still deliver an incredible 90 Nm of peak torque, more than most sportsmotorcycles.

Even electric scooters use similar large amounts of batteries. Take for example the BMW C-Evolution:

BMW-C-Evolution-Batteries

Apart from the 12 cells (which by the way come from the electric car from BMW, the i3), there is one “normal” 12V battery located in the front housing which takes care of the normal electrical functions (dashboard, horn, etc).

The engine’s batteries, like the Brammo, are Lithium-Ion and supply 8 kWh. Recharging these batteries using a standard domestic 12A socket takes 4 hours (if it’s a 16A socket, it’ll take 3 hours).

The 12 cells supply 60 Ah and 133V, and the whole scooter weighs 265 kilos. But despite that weight, you get a torque of 72 Nm which is available all the time.

So as you can see, batteries take up the biggest amount of space on an electric bike. By far! Over the next few years, even decade, the batteries will start becoming smaller, lighter and packing more punch, allowing for longer rides. But until then, you will need to content yourself with riding 60 to 100 miles before requiring a charge. Far enough for a daily commute, not far enough for a weekend ride of the Tail of the Dragon at Deals Gap.

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We all know by now that Harley-Davidson motorcycles are known for their potato-potato-potato sound. You can recognize a Harley miles away just from its sound (and probably the loud pipes). The same goes for most BMW and Ducati motorcycles.

But did you know that the sounds are engineered? It used to be that engineers and designers looked after the engine and then the motorcycle frame; the sound came automatically afterward. The only thing the engineers looked at when it came to the sound of the engine, was if it stayed within the legal regulations envelope.

(c) Harley-Davidson

If the sound sounded dull, they adapted the exhaust noise. But Harley wanted more. They continued their research and found that people liked the potato-potato-potato sound, so they set out to replicate it on all their motorcycles. During the ’90s they even went so far as to patent their sound, but despite popular believe, their attempt was unsuccessful.

This brought in a new profession in the motorcycle industry; Acoustic Engineers. Almost all, if not all, manufacturers have at least one. Their job is to ensure that when you fire up your engine, it doesn’t sound like a lame duck with a severe flu. Nothing turns off a biker more than the sound of a lawnmower, not a real motorcycle when starting up their bike.

(c) BMW Motorrad

BMW have a special wind tunnel that generates a wind flow of 200 kph, but is totally silent. This allows their engineers to measure and analyze the sound coming from the motorcycle’s engine, exhaust and frame. Special care is taken with vibrations from different parts of the motorcycle, as to ensure that they do not disrupt the bike’s melody. A test dummy sits on top of the motorcycle, and hears everything a normal biker will. That sound is recorded, and analyzed for further improvements.

(c) AVL

The motorcycle sound is made out of three different parts; the air intake, the engine noise and the exhaust, but other parts of the motorcycle can negatively influence the engineered sound, like a dry clutch. So next time your ride your bike, enjoying the throb and sound of your engine (especially in a tunnel), remember that the sound was made, not an accident.

Of course all this goes away with the coming of the electric motorcycle, unless you use a CD player with the desired sound.

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