Rear Brake Pedal...class 1 Levers...mechanical Advantage

[iconic558]

My SWM has had it's footrest moved down and back thus making the rear brake pedal position a bit off for one with smaller feet...needs to be further back and lower to be ideal...cut and shut would be too easy.

Now the rear brake pedal acts a class 1 beam lever....load-fulcrum-effort, so if I shorten my lever this means I will loose some mechanical advantage, not good.

I should know the answer to this question but here goes....

....if I call the original 'effort-pedal-foot-touch' point 'A' and weld a strip of metal to this original point but below & at an angle of 45' and at a point 2" further back in the direction of the rear wheel & call this position B, would the 'effort-pedal-foot-touch' point of the lever now be at this new shorter B point or the original further forward point A?

or other words the foot now press's down 2" further back but acts as if it was 2" further forward by acting as if it was still in the original position...hope that makes sense....I've read and reread this a few times and its hard to put into words without a drawing.

I think the effort would act as if it's still acting on a shorter lever thereby still reducing my mechanical advantage as the effort acts as if it goes thru the beam not on the end of the beam but have to check my physics

[ourian]

I tend to agree with you.

It's the distance in a straight line from the fulcrum point to the point of which the effort is applied which determines the force required.

[iconic558]

I'm sure you are correct..

.....but you know when someone pops their head over ya shoulder and plants a seed of doubt even though you damn well....

thanks for that, for a moment earlier today the universal lever law was in questuon!

[ourian]

There are two ways I can think of to solve the problem

1) move the pivot (fulcrum) point back

2) shorten the distance from the fulcrum point to the point of load and the point of effort i.e. reduce the distance from the pivot to where the brake rod/cable attaches to the pedal and shorten the pedal itself, however, this method would require the now shorter pedal to travel further downwards to create the same braking effect as before.

Edited December 29, 2014 by ourian

[ask greeves]

I would ask an Egyptian, they managed to build pyramids using levers and fulcrums, so a SWM rear brake should be no problem....Also remember, position the rear brake lever wrong, and rear suspension action, will cause the rear brake on and off, if worked by rod.

Edited December 30, 2014 by ask greeves

[totalshell]

make the brake arm longer so although your brake pedal leverage will be reduced you can even it up by lengthening the rear brake arm..

[iconic558]

make the brake arm longer so although your brake pedal leverage will be reduced you can even it up by lengthening the rear brake arm..

good thinking, great idea....also would cure a slight interference issue with the cable I already have.