Question

Kinematics Problems

Describe the following thread: 1-1/2" - 6-UNC – 3B A 1-12-UNF thread is used in a scissors lift to raise a stand 8 inches. Using the diagram on the board determine how many revolutions of the thread must be made to do so. A 2" - 4 Acme (pitch diameter = 1.8402 inches) double lead thread is used to rapidly raise a load of 20,000 pounds. If u is 0.40 what is the torque required to turn the bolt? If the wrench is 2 feet long, how much force is required to turn the bolt?

Answer 1

This question is based on the Threads terminology and Screw Jack Design.

Screw jack is used to lift heavier weights by applying less amount of effort on the lever by using threaded nut and bolt with collar.

The step by step solutions for all the three questions is given below:-

(6 - 12 - UNF threads, Nominal diald) 1 inch Threads per inch. - 12. Distance travelled in one turn = 4 inch. 2 full 0.0833 inų 12 To travel 8 inches no of turns = required Nominal diameter 6.0833 e htud 96 turns Pitch Haxis- (6) 2 - 4 ACME pitch dia= 1.840 212 double lead thread. Nominaldiameter d = 2 inch threads per inch = 4. I (P2 bitch = 114 Coredlameter, der do P de 2 - 1 2 = 1.75 in. dede mean diameter dan dm = 2+uns = 1.875 in

edmi stan a = ka helt angle lead. tand - 2x 14 2x 1.875 = 0. 0848 [x = 4.8518] See & = 1.0036 load (F) = 20,000 lbs. and coefficient of fiction canna0.40 Torque required to raise the road, by turning the bott, T = F xdm / taudin seed Ladnoul seet 3) TR = 20000 x 10875 T 12 + 2 x 0140 x 1-875 X116036) 2x1.875 -0.408/71.0036 » TR = 10000X1.875 2. 865 S.6897 I TR= 9441. 293 lbs-in length of wrench (leness = 2 ft. Gli ex12 inch force Required to turn the bott, Foto 9441293 393.387 ebs.