Recent postsView all

Unit Plans
2 Jun 19
Getting started?
27 May 19
Practical work (and Paper 3)
18 May 19
Group 4 Project
12 May 19
Single slit distraction
9 May 19
Extended Essay
5 May 19
26 Apr 19
IA 2019 reflections
21 Apr 19
21 Apr 19
Individual investigation
13 Apr 19
6 Apr 19
1000 questions
30 Mar 19

Cracking ball joints

Thursday 4 January 2018

Today I was dismantling the suspension of my Triumph spitfire. This involves removing several ball joints. A ball joint has a tapered end that fits tightly into a hole, removing them is difficult so you need a ball joint cracker. This fits between the ball joint and the holding arm, you tighten the nut and the ball joint pops off. Today I had a bit of a shock when a ball joint flew off suddenly at great speed. I should have known it would since I was doing a lot of work tightening up the bolt storing PE in the joint that was converted to KE when it is released.

Let´s say I was exerting 300 N over the last half turn with a 20 cm long spanner. Work done = Torque x angle = 300 x 0.2 x π =190 J. The ball joint weighs about 200g So it´s velocity can be found from 1/2mv2 that gives 44 ms-1 which is 160 kmhr-1 . That´s why it´s best to crack them while they are still attached to something. To be honest I think my estimate is a bit high, a lot of energy will be lost in friction.

Mock exam
21 Jan 2018


To post comments you need to log in. If it is your first time you will need to subscribe.