after each third pick of the weaving process to permit reed 16 to 34 beat 34 the pile warp into the fell of the cloth being woven the end of arm 44 located within the fork of arm 40 is provided with an elongated slot 46 to receive a pin 48 secured at its ends to the fork a block 50 also is located within slot 46 the block is joined to a lead screw 52 threaded into arm 44 the lead screw 52 is joined by a flexible drive cable 54 to motor 38 thus as motor 38 operates block 50 is moved along slot 46 repositioning of the block varies the degree of displacement imparted to the lower end of arm 40 by the uniform horizontal movement of arm 44 produced by the cam drive the motor 38 has associated with it a rotary limit switch 60 which is set to turn off the motor when the rocking bar 18 is adjusted to its maximum and minimum limits the rocking bar 18 is interconnected with a slide 56 which reciprocates horizontally in response to the arcuate movement of bar 18 caused when the lower end of arm 40 is displaced slide 56 carries at its outer end a spiked roll 58 the spikes penetrate the cloth produced by the weaving operation roll 58 turns only.