Thread: 130 on portals

Originally Posted by uninformed

John, I think Im just confused, but to me you are saying that putting portals on a stock rig and not changing anything else, will increase squat? and that the only way to address this is to change the link geometry to achieve a higher % anti????

Im pretty certain adding portals and nothing else puts the anti-squat as a % higher...from everything I have read on pirate by Sam and triaged etc...and playing with the 4 link calculator. Thats why tyres alone or even just a different wheelbase changes the % of antisquat

what am I missing or miss reading????

cheers,
Serg

I have not investigated it properly, but what I was meaning is that when the COG is raised by larger tyres or portals then the inertia during acceleration will increase the apparent weight transfer to the rear springs and increase the squat force. The part I don't have time to investigate is whether the anti squat change will increase or decreases the percentage.

BTW I should have pointed out in my earlier post that, when all said and done, it is the ratio of anti squat force / squat force x 100 to make it a percentage that is most useful. By doing this, both the mass and acceleration (and the units) are mathematically cancelled so making the xx% antisquat independent of mass and acceleration changes.

Thanks John,

so if i have it right....rasie the COG (tyres/portals) with no link or spring change and the squat force (the amount the vehicle wants to squat down in the rear under acceleration) increases.....and Im 99% sure that rasing the COG will also cause the anti % to raise....I guess the question begs, is it a proportional change for both....ie will the rig feel and different by the seat of the pants when accelerating on level ground....

At the end of the day, anti-squat and anti-dive are only 2 things of more that make the whole....to me im guessing anti-dive be the more inportant safety wise. Performance wise, IMO you could get away with less anti-squat and anti-dive as long as the vehicle isnt pitching fore and aft under accelleration and braking....for me axle roll axis angle is important, as is the relaation between contact patch and chassis bush of RA and TA...but more importantly the RA in the front. I know there are other link set ups to go to like 1/3/4 etc...but for me RA presents a simple solution using some exsisting mounts and is easy to package on the outside of chassis rails....the rear A frame type link also lends it self to easy mods that can improve offroad and onroad perfromance when lifting COG, keeping onroad safety and handling.

cheers,
Serg

Serg,
I tried a couple of hypothetical 4 link suspensions and then changed the height as would occur if adding larger tyres - suspension geometry unchanged except height above ground. The results were that the %antisquat increased as you stated.

The %antisquat is a ratio of antisquat/squat so the anti increased at a greater rate than the squat for both cases.

In neither case did the angle of the roll axis change. This result is as expected.

good work.. where can i get this conversion kid?

Originally Posted by borneo_boyz

good work.. where can i get this conversion kid?

Portals? Call Daniel at Mulgo. I am having it done ATM and you can check progress in chooks defender thread in members rides.


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Hi Chook, do you need an engineers report done for portals?

yes you would need to

Originally Posted by gaz

Hi Chook, do you need an engineers report done for portals?

Yes absolutely you do......

There are not a lot of engineers that will do them either