combined trailing arm mount/body outrigger

My explanation of anti-squat starts with what squat is.

When a vehicle accelerates (level or inclined surface) inertial forces (force = mass x accel and every force has an equal but opposite reaction) act in the opposite direction. The sum of all of these reactions is resolved to the height of the centre of gravity. During forward accel, this causes an increase of the load acting on the rear springs, compressing them, and a reduction in the the load on the front springs, extending them.

When the rear suspension geometry is designed to produce anti-squat, the force in the suspension links create forces that have a vertical component to lift the vehicle apposing the squat forces. If anti-squat is equal to, but opposite direction, this is called 100%. It can be less or greater than 100%.

If the rear, lower links are parallel to the ground, they will not create any lift (0%), if they are very steep, anti-squat will high.

Squat and anti-squat both change the suspension geometry, and if anti-squat is greater than 100% the change in geometry leads to even greater anti-squat, which leads to unstable change in geometry/anti-sqaut and hopping during hill climbs. This is what Serg is most concerned with here.

John has simply and clearly stated what I was trying to....this is the sign that he really knows it and I just feel it.

For me it is not only AS that im looking at, But roll/bump steer and geometry change through Bump and Droop. There are alot of comprimosies though, as Im not starting with a clean sheet of paper. For example, as im not changing the A frame links I am limited to the length chnage of the TA's otherwise there will be some funky pinion angle changes through bump and droop due to the different arcs the uppers and lowers will scribe....

IMO the stock RRC on 29s probably has it bloody good for a mass production vehicle...but as soon as you change one thing, it all changes. Example, change the wheelbase and the AS/AD changes. Fit larger tyres AS/AD changes....and if you fit longer springs it changes more things, Roll axis angles, roll center (in the front due to Panhard)

I have in mind many things I would like to do...but feel it can only be tackled one item at a time. Consideration has been made to the final set up, but any effect that only doing one item will cause.

Thankyou John, Dougal and Serg, but my head really hurts now from reading the replies and I think I will retire from this vehicle modification hobby. It's getting too scientific for my feeble old brain to keep up with.:confused:
bill.

The guys that can model all these suspension setups and play the compromise game to get a particular outcome aren't necessarily much more knowledgeable than someone who has a gut feel approach.

It is often the combination of an internal sense, an understanding of the science and access to resources like modelling software than can make some breakthroughs. I would therefore not throw it in Bill, it takes all kinds. All the better when shooting the breeze.

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Originally Posted by wagoo

Thankyou John, Dougal and Serg, but my head really hurts now from reading the replies and I think I will retire from this vehicle modification hobby. It's getting too scientific for my feeble old brain to keep up with.:confused:
bill.

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Says the guy who's built more than all of us.:D

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Originally Posted by Dougal

Says the guy who's built more and achieved more successes than all of us.:D

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Fixed it for you!

Suspension geometry, relies upon solution of triangular geometry (i.e. trigonometry involving sines, cosines and tangents, etc. of angles).

As such it is easy to solve by graphical methods and, with some knowledge of these constructions, can be visualised by simply looking at the relative positions of the ends of the links relative to the tyre contact with the ground and a good guess of the location of the centre of gravity. Some people don't need to do any more than this.

What I find a little missleading is that some people think that these theoretical lines through certain points are lines of force that cause squat/dive and their anti's, etc. In fact they are only a graphical method to resolve the resultant of a bunch of forces and solve the vertical/horizontal components of them.

The other thing which missleads is that the suspension geometry and forces constantly change when our vehicles travel over obstacles.

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Originally Posted by Bush65

Suspension geometry, relies upon solution of triangular geometry (i.e. trigonometry involving sines, cosines and tangents, etc. of angles).

As such it is easy to solve by graphical methods

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That's it exactly. It's a geometry problem (like ~90% of mechanical engineering), the complicated maths is just there to describe the geometry.

Quote:

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Originally Posted by Bush65

Suspension geometry, relies upon solution of triangular geometry (i.e. trigonometry involving sines, cosines and tangents, etc. of angles).

As such it is easy to solve by graphical methods and, with some knowledge of these constructions, can be visualised by simply looking at the relative positions of the ends of the links relative to the tyre contact with the ground and a good guess of the location of the centre of gravity. Some people don't need to do any more than this.

What I find a little missleading is that some people think that these theoretical lines through certain points are lines of force that cause squat/dive and their anti's, etc. In fact they are only a graphical method to resolve the resultant of a bunch of forces and solve the vertical/horizontal components of them.

The other thing which missleads is that the suspension geometry and forces constantly change when our vehicles travel over obstacles.

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the only reason I can visualise the small amount I can, is because I play with BASIC trig. most days and constantly looking at angles etc for work...

The forces would have to be transmitted through the physical components would they not??? I cant see force shooting out from the tyre contact patch through the point of IC and over the front axle.......dissapearing into the eather :D

But that imaginary line is still a very important one IMO

Suspension change is the whole reason I want to change mine....at static height it is fine and drives ok on flat level ground, but when you go around cornes etc things change rapidly....

Quote:

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Originally Posted by wagoo

Thankyou John, Dougal and Serg, but my head really hurts now from reading the replies and I think I will retire from this vehicle modification hobby. It's getting too scientific for my feeble old brain to keep up with.:confused:
bill.

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Bill, the science has been there from the begining of exsistance, its just that now the internet is here it has opened up the web wheelers (me!) to bang on about something that I know VERY little about...

I would not be able to learn were it not for the very knowledgeable, like John, nore without the workings of guys like yourself (that is not to say you are not very knowledgeable as well)

You can have my theroy(ill write it all down on a grain of rice) if I can have your pratcial experience and unique designs :)