Joined
·
529 Posts
I started a debate with this know it all about how cranking up your torsion bars on your IFS is not a good idea.
I need some really good theory and explanations to shut him up. More theory then my limited experience can provide.
It all started when he said that adjusting your torsion bars wouldn't effect travel and I told him that wasn't true.
I had told him the more you crank the torsion bars, the higher the effective spring rate on your front end, thus taking more weight to get the same amount of compression.
Which results in
-harsher ride
-less travel especially in the downward direction (droop) of the suspension.
Here's his response.
[ 10-13-2001: Message edited by: Mark 73' FJ40 ]
I need some really good theory and explanations to shut him up. More theory then my limited experience can provide.
It all started when he said that adjusting your torsion bars wouldn't effect travel and I told him that wasn't true.
I had told him the more you crank the torsion bars, the higher the effective spring rate on your front end, thus taking more weight to get the same amount of compression.
Which results in
-harsher ride
-less travel especially in the downward direction (droop) of the suspension.
Here's his response.
Thanks guysOkay, spring theory 101, there is no way to change the spring rate of a spring once it has been made. The spring rate of a torsion bar or any other type of spring is fixed after it has been made and depends on the shape, cross section and material properties and no adjustment in the world can change it!!!! The spring rate of a torsion spring is in the form; radians/pound-foot. That means, if you twist a bar with 100 lb-feet of torque, then it will twist a specific number of radians, which can be expressed in degrees as well. Therefore, if you double the torque applied to the bar, you will also double the twist, linear relationship. There are a few real weird springs that don’t behave this way but a torsion bar surely does.
Now, if I preload a torsion bar spring with 25 lb-feet of torque, then to apply an additional 100 lb-feet or torque you would need to input a total of 125 lb-feet even though you only added 100lb-feet of torque to the system because of the previous 25lb-feet of preload. The net effect or internal stresses will be the same as if you applied 125 lb-feet or torque with no preload. In effect, by adjusting the torsion bars a couple of turns on that screw increase the preload a bit, but not a drastic amount. Now for the angle on the axles shafts, I calculated it before and after and it is
So, your statement is flat wrong about changing the spring rate of the torsion bars by adjusting them. Even the Pope couldn't change the spring rate man, there you go guessing again. What does happen though is you do change the pre-load if you adjust them. Pre-load is a far cry from changing the spring rate.
[ 10-13-2001: Message edited by: Mark 73' FJ40 ]