Okay, motorcycle helmets seem to be more protective (more apt to cover the whole head rather than mostly the top half), which makes sense, given that a motorcycle can hit much higher average speeds, and that therefore a crash can be potentially far more serious. Since motorcycles go faster, though, wouldn’t an aerodynamic shape provide a greater advantage their riders? You could take a traditional “bubble” type helmet and add spoiler-type extensions, right? Other than the fact that they’d look goofy, why don’t they make such helmets?
Actually, racers do have an aerodynamic hump, but it’s built into the back of their leathers rather than attached to the helmet. Shown here in this pic of Valentino Rossi.
Still – “all” bicyclists, not just racers, wear the aerodynamic helmets. I guess the other question could be, why aren’t there non-aerodynamic bicycle helmets?
Still – “all” bicyclists, not just racers, wear the aerodynamic helmets. I guess the other question could be, why aren’t there non-aerodynamic bicycle helmets?
One more thing, motorcycle helmets also have little ridges and spoilers and such. In that pic of Rossi, you can see a spoiler strip running across the back of the helmet from the corner of the “AGV” decal. Mainly to improve stability and to keep the airflow from trying to lift the helmet off your head. Not just racing helmets, either. Lots of street helmets have similar features.
Why all bicycle helmets are aerodynamic, I don’t know. Probably just the fashion.
You could say that cyclists have aerodynamic helmets because they are relying on their own body to power the bike. On the other hand a motorcyclist doesn’t care about how much drag he’s creating because he doesn’t have to put in any work to get the bike to move. At worst, a draggy motorcyclist might have a slightly higher fuel burn than a non-draggy one.
You could say that. But I don’t think a streamlined helmet makes an ounce of difference to you average bicyclist.
You also have to factor in that overcoming drag on a bike requires muscle power. Overcoming drag on a motorcycle just requires a bit more rotation on the throttle.
in many ways yes. Keep in mind that aerodynamic forces increase as the square of airspeed. Moving at 2-5 x the speed of a bicycle, the motorcycle helmet would produce 4-25 times the force.
In the event of an accident at motorcycle speeds, where the rider ends up rolling or sliding along the ground, you really don’t want too many things sticking out from the helmet, as these will snag and exert rotational forces on the neck.
Yeah, I thought about that. If you were doing them as add-ons, rather than molding the helmet shell as a whole with ridges, you could design them to break away on impact.
Ummm, the ones I have on my helmet are for vents and that’s what they look like to me. The bump on his back also looks like a back protector. IANA Motorcycle racer though, but it looks a lot like the stuff you can get for street wear.
I would say that the reason motorcyclists don’t have such helmets is because it doesn’t really matter. On the corners you have to turn your head, and on the straights you tuck in behind the shield which would do a lot more good then a helmet.
A rider on a bike is very un-aerodynamic to begin with, the advantage gained by the addition of a tail on a helmut is likely to be significant only in a competetive environment.
A much more significant difference can be made by simply lowering the cyclist, as any one who has ridden into a head wind has probably noticed
Depends on the helmet. My HJC ($) doesn’t have anything besides vents either, but my buddy’s Shoei ($$$) has a ridge across the back that’s supposed to reduce lift. But motorcycle helmets are designed primarily for safety and comfort, so it seems to me that making them aerodynamically neutral in a variety of orientations is best.
BTW, in his book A Twist of the Wrist, former racer Keith Code says the real reason motorcycle racers have the hump isn’t for speed (it only adds 1-2 mph to top speed) or protection (on the track you wear a back protector like these under your leathers), but to reduce rider fatigue by reducing the loading on the helmet. He relates a story of a time the team was testing aero configurations and they had various different humps to attach to the back of plain leathers. A hump fell off at speed and the difference was striking, said it felt like 10 lbs (IIRC) was instantly added to the helmet.
