You only JUST got caught if i had of been 1 minute later to read the post you might have got away with it a little longer
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RUFF wrote:In general we dont but if something looks a little odd its easy to check
You only JUST got caught if i had of been 1 minute later to read the post you might have got away with it a little longer
Dash, Darn, I thought I could convince the world I was going to drive a shorty too.
Peter Kincade
SAM!!! D O N ' T Do it Bloke!!!
overkill wrote:Pete the whole driveline is in minnus tailshafts. Th truck is sitting about 3 inches higher than it will when move the front shackle mount. And yes Pete the Kone invader's turned up I managed to sneak photo without them knowing I'll post it up when it gets dark
SAM
Whatever you do. Don't go near those darn KONES in the dark. They turn the lights out so you can't see 'em and they play tricks on you like, er, they do stuff to your truck parts when your not looking. Last night I went inside to make a cofee, and when I came back they had jigged this up on the mill and they were, they were, errrr, um, they were eating it! ..... like this!!!
Peter Kincade
overkill wrote:Well show us some pics.
I have the material here for the tubes, but the axles won't be back for a week. Once I have turned out the diffs I will take a before & after with the new tubes. Unless of course those darn KONES beat me to it first.
Seriously though, by this time next week, I should have the frame complete and I will post some pics of it up on the jigs.
Peter Kincade
Cheezey have the KONES seen youe bender?
Hey Cheezey. How is your follower bar holding up on your bender? You know, the ally channel that the material is guided against the die by. Interested to know ...
Peter Kincade
overkill wrote:Bushy if I draw a line through the A frame and the controll arms at normal ride height they meet about half way through the engine. I don't know what that percentage gives me. Do you know?
My guess is that would make it a bit over 100%.
Looking at the side view:
1. Determine the height 'h' to the centre of gravity.
2. Draw a line from the point where the rear tyre contacts the ground to another point at height 'h' from the ground at the front axle - this line is the locus for 100% anti-squat.
3. Draw a line through the pivot points at both ends of the upper A frame.
4. Now draw another line through the pivot points at both ends of the lower control arms.
5. Extend both lines until they intersect - this point is the IC (instant centre).
6. Draw a line from the point where the rear tyre contacts the ground through the IC.
6a. If the upper A frame and the lower control arms are parallel (i.e. they never intersect) draw the line from the point where the rear tyre contacts the ground and parallel to the lower control arms.
7. If the line drawn at step 6 (or 6a) lies on the line drawn at step 2 then you have 100% anti-squat. If below, anti-squat is less than 100%. If above, anti-squat is greater than 100%.
Expressing this in a mathematical formula (reference "Race Car Vehicle Dynamics" - W. F. Milliken and D. L. Milliken, page 619) :
% Anti-squat = [(tan theta R)/(h/L)] x 100
Where:
'theta R' is the angle between the ground and the line drawn at step 6 (or 6a).
'h' is the height to the centre of gravity.
'L' is the wheelbase.
About 80% anti-squat is generally considered desirable. If it is greater than 100% the rear wheels are likely to bounce while climbing (Sam - StrangeRover has explained this well here and on Pirate). The top rock crawlers in the USA prefer large ant-squat with a limiting strap to prevent the rear lifting (and the wheels from bouncing).
John
N*A*M wrote:DirtPig
Can you draw me a diagram so I can understand this more clearly?
How do you accurately determine the CoG (and there fore the height 'h')? Is there an easy way to do this? I know it can be done relatively easily if you have one of those tip-tables but otherwise???
The value of anti-squat is a function of the CoG, so this must be accurately determined if any anti-squat figures are to make any sense.
Here is my sketch of the instructions detailed above...
Weight transferred to the rear wheels during acceleration is:
h/L x Weight x accel/g (where g is gravitational accel).
Note: the 1st term h/L - the cyan line in Fig. 1 is h/L.
The other terms (W x accel/g) is the value of horizontal force at the tyre contact and the moment of this force causes tension in the UCA and compression in the LCA
The tension and compression in the control arms can be resolved at the instant centre 'IC'. The direction of resultant force is along the cyan line (y/x) through the IC in figures 2 and 3. This is for solid axles - it is different for independent rear suspension.
If h/L = y/x then the forces in the control arms exactly counter the weight transfer during acceleration and the load on the rear suspension springs will be unchanged - the rear end of the vehicle will not squat or raise (100% anti-squat).
If h/L is less than y/x the vertical component, of the resultant of the forces in the control arms, will be greater than the weight transfer and the load on the rear springs will be reduced and the rear end will raise (more than 100% anti-squat).
h/L x Weight x accel/g (where g is gravitational accel).
Note: the 1st term h/L - the cyan line in Fig. 1 is h/L.
The other terms (W x accel/g) is the value of horizontal force at the tyre contact and the moment of this force causes tension in the UCA and compression in the LCA
The tension and compression in the control arms can be resolved at the instant centre 'IC'. The direction of resultant force is along the cyan line (y/x) through the IC in figures 2 and 3. This is for solid axles - it is different for independent rear suspension.
If h/L = y/x then the forces in the control arms exactly counter the weight transfer during acceleration and the load on the rear suspension springs will be unchanged - the rear end of the vehicle will not squat or raise (100% anti-squat).
If h/L is less than y/x the vertical component, of the resultant of the forces in the control arms, will be greater than the weight transfer and the load on the rear springs will be reduced and the rear end will raise (more than 100% anti-squat).
John
DirtPigs wrote:N*A*M wrote:DirtPig
Can you draw me a diagram so I can understand this more clearly?
How do you accurately determine the CoG (and there fore the height 'h')? Is there an easy way to do this? I know it can be done relatively easily if you have one of those tip-tables but otherwise???
The value of anti-squat is a function of the CoG, so this must be accurately determined if any anti-squat figures are to make any sense.
Here is my sketch of the instructions detailed above...
To determine the position of the CoG you need to measure the weight on the front wheels and the rear wheels seperately while the vehicle is level. Then measure the weight on the front (or rear) wheels when they are lifted a reasonable height above the rear (or front) wheels and note the height that the wheels were lifted.
The horizontal distance from the rear wheels to the CoG = (weight at front x wheelbase)/(weight at front + weight at rear).
The height to the CoG is more difficult - I have a spreadsheet (by another) that I will e-mail to anyone that wants it.
John
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