Ackermann geometry on TVR,s
Discussion
How did you accomplish the other changes?
Are you thinking of a combination of moving the fore/aft location of the rack and changing the length of the steering arms?
Are you looking for faster turn in?
Why are you thinking you don't have enough Ackermann effect?
Have you run the geometry through Suspension Analyzer, or Wishbone, or some such other software?
You were probably looking for answers, not questions, weren't you?
Best,
B.
Are you thinking of a combination of moving the fore/aft location of the rack and changing the length of the steering arms?
Are you looking for faster turn in?
Why are you thinking you don't have enough Ackermann effect?
Have you run the geometry through Suspension Analyzer, or Wishbone, or some such other software?
You were probably looking for answers, not questions, weren't you?
Best,
B.
Got rid of bump steer by making new steering arms
am trying to get best road (90%)and track handling i can, as the chevy engine can easily produce big power
adding caster and getting rid of bump steer made a big difference
was just thinking of adding ackermann by altering the steering arms
not sure about KPI on the early Tuscan S6 either
thanks
am trying to get best road (90%)and track handling i can, as the chevy engine can easily produce big power
adding caster and getting rid of bump steer made a big difference
was just thinking of adding ackermann by altering the steering arms
not sure about KPI on the early Tuscan S6 either
thanks
One thing to consider is that track compromises are different from street, in the sense that other costs are weighed at less value. So, while you'd be happy to increase camber on a track car, tire wear on a high miler would suck. Similarly, one thing I've heard people building various race cars mention, is that increasing toe-in creates a better preload on the outside tire, and accelerates turn-in, which allows the car to take a set more quickly. Again, to the detriment of tire wear.
I vaguely remember the Ultima guys having a discussion on Ackermann, and IIRC, the consensus was that scrub on the inside front was not all that important. Maybe that's because of the weight transfer to the rear on some of these light weight, high power cars, on corner exit. (My memory is for s
t, so I might have read that elsewhere.)
Basically, what I'm trying to say, is that whatever you do to "maximise" grip on the track will probably not be acceptable on the road. One thing someone who has a very quick M mentioned to me, is that what makes for a nice track set up (in the way of springs, shocks, ARBs, and settings), may be very "twitchy" on the street, especially in the rain.
Have a look at this bump steer set up:
The pic below is of Mike Zappa's M.
Best,
B.
P.S. Please post piccies of the steering arms you made.
I vaguely remember the Ultima guys having a discussion on Ackermann, and IIRC, the consensus was that scrub on the inside front was not all that important. Maybe that's because of the weight transfer to the rear on some of these light weight, high power cars, on corner exit. (My memory is for s
t, so I might have read that elsewhere.)Basically, what I'm trying to say, is that whatever you do to "maximise" grip on the track will probably not be acceptable on the road. One thing someone who has a very quick M mentioned to me, is that what makes for a nice track set up (in the way of springs, shocks, ARBs, and settings), may be very "twitchy" on the street, especially in the rain.
Have a look at this bump steer set up:
The pic below is of Mike Zappa's M.
Best,
B.
P.S. Please post piccies of the steering arms you made.
Walford said:
Have dropped track rod end, this has straightened it out relitive to the rack
I don't think that would change the Ackermann effect as you'll still get the same turning radius for each wheel. I spent a fair amount of time looking at Ackermann effects (albeit in a different context of a variable power 4WD system). My only real advice if you're serious about making changes then you need to have some definable goals and do some testing as to what you find is the best setup for you.
If you want to create better "performance", then you'll need to split this out into a few areas such as turn in, initial bite/feel, steady state speed/stability etc.
If you're fabricating some new steering arms, then i'd have a look at putting multiple mounting points for the steering arms, and also look at how much movement you can create you have in the rack front-back. Plump some figures into a calculator or simulator and see what change in the Ackermann % you have a realistic chance of making.
I'm not sure what the std % is for the Tuscan?
Also worth bare in mind that the more you deviate from a "general" setup, then the more specific the car will be set up and feel good only in a diminishing number of situations. The roads here are so varied then i'd suggest getting some steering arms made, and do some testing to find out what "feels" best for you.
Oh, and keep us updated, it's good to see people still willing to try out different set ups!
When viewed as a "static" diagram, I agree, that there would be no change to Ackermann effect. When you think of the dynamic system, and you consider body roll, I would speculate that you've increased Ackemann.
Here's my logic:
Toe-in increases more with track rod/tie rod articulation from 10deg inclination to 20 deg inclination, than it reduces from 10deg to 0deg.
Equal body roll with track rod/tie rod articulation from 0deg inclination to 10 deg inclination, and from 0deg to -10deg, respectively, produces less overall gain in toe-in.
Therefore, you have effectively increased the distance from one track rod/tie rod to steering arm interface to the other, thereby causing the inside wheel to turn in further for the same angle on the outside wheel.
I hope that's right, it was a long day before I started thinking about this.
Again, I'd strongly urge you to download some free software, and play with it. That's so much faster than building new bits. I can't remember where I grabbed "Wishbone," before my last computer gave up the ghost, but it's a fun one.
Best,
B.
P.S. Since I'm guessing at the numbers, you might want to run the actual geometry through a calculator. Also, I agree w/ the rest of MrChips comments.
Here's my logic:
Toe-in increases more with track rod/tie rod articulation from 10deg inclination to 20 deg inclination, than it reduces from 10deg to 0deg.
Equal body roll with track rod/tie rod articulation from 0deg inclination to 10 deg inclination, and from 0deg to -10deg, respectively, produces less overall gain in toe-in.
Therefore, you have effectively increased the distance from one track rod/tie rod to steering arm interface to the other, thereby causing the inside wheel to turn in further for the same angle on the outside wheel.
I hope that's right, it was a long day before I started thinking about this.
Again, I'd strongly urge you to download some free software, and play with it. That's so much faster than building new bits. I can't remember where I grabbed "Wishbone," before my last computer gave up the ghost, but it's a fun one.
Best,
B.
P.S. Since I'm guessing at the numbers, you might want to run the actual geometry through a calculator. Also, I agree w/ the rest of MrChips comments.
Gassing Station | General TVR Stuff & Gossip | Top of Page | What's New | My Stuff