Working Principle of Sewing Machine ( Paddle Part )

[shinnsohai]

Hi guys,
I wanted to ask something that I am interested on
Which is on the traditional sewing machine mechanical mechanism (On the foot paddle part)

Image taken from Google.

From the image above, a typical sewing machine
For such application, what is the "Name" for it?
Im more likely wanted to know more about how do i calculate the force from paddle to the sheave

P.S: I've been searching around the internet, all i got on the principle of the sewing machine is on its lock stitch

 

[SteamKing]

The mechanism is called a "treadle":

http://en.wikipedia.org/wiki/Treadle

In the days before electric motors became common, the sewing machine operator would use a foot pressing on the treadle to turn a crank, located up above. Turning the crank converted the reciprocating motion of the treadle into a rotary motion used by the sewing machine on top.

 

[shinnsohai]

Thanks mate!
I'll look into it