> US DOT regulations.
> Requires the wipers to cover a specific percentage of the windscreen (I
> don't remember the exact percentage). The twin wipers on the MGB and
> Midget didn't cover enough.
> SO, in their infinite wisdom, the boys at the works added another arm
> and blade.
> Incidentily, the triple blades were on roadsters. The GT with it's
> larger windscreen and slightly longer wiper blades made the cut.
> Rick Morrison
> 72 MGBGT
> 74 Midget
>
It also has to do with the geometry of the windshield wiper motor and
arms on the 'B'. If you just had two 10" blades, but each one went
through 180 degrees of sweep, you would have a total swept area of
314 square inches, which would probably be enough to satisfy US DOT
regs. Some trucks and airplanes use this type of semi-circular sweep
pattern. Because the axis of rotation of the MGB wipers is so far
from the blade, a third blade was the easiest way to go. To get a
full 180-degree sweep, you have to have the shaft of the
wiper motor exit the body right at the upper or lower edge of the
windshield, and that just doesn't look right on most cars.
Scott
|