Tie rod ends

[66TigerMK1A]

If you want to do the math, Dr Mayfield's website has all the formulas he used to calculate Akkerman angles. Also his consensus is that a whole new crossmember is needed to achieve the correct angles. Reference to his web site at "Mayfield Company"

Mayf has some good info on his site... and ya.. if you want to have something close to perfect steering just call Mike $$$... or Dale $$$$$ for a complete custom front end.
There is still some room though to make slight improvement to the existing setup.
While those RV8 arms may bolt up, and it's true that the longer the arm will slow the 'effective' ratio, it also puts it slightly closer to the rack centerline so not as bad as it seems because it will lessen that angle. That's why the MGB arms help the ackerman.The bigger issue with those RV8 arms is that the tie rod end will be even farther inboard from a good 'ackerman' point
Mal... sending you the long version by email


Jim
B382000446

 

[Tiger tamer]

Not true. When you have a link with ball joints at each end, it is only capable of transmitting force in line with the axis from joint to joint. The shape of the part connecting them makes no difference. Because of the inherent geometry of the suspension with the rack so far forward compared to the tie rod end, there will always be an excess longitudinal load on both the rack and spindle; since the link can only transmit force in one direction, to get the necessary lateral component (to steer) it must also have a longitudinal component that makes the total force in line with the link axis. (Let me know if that is too much engineer speak and I'll explain it another way). That force is taken up by the bushings at the end of the housing. The slipper pad (assuming by that you mean the spring loaded aluminum bushing) is there to keep the rack tight to the pinion, so it doesn't want to climb off it with force.

A few other comments on the subject. Using a rack that is that much longer has a number of potential downsides. The first is that the bump-steer curves will be drastically different than what you are replacing. Not to say that the existing Tiger geometry is perfect (I don't know, but based on the Ackerman problem, I doubt that much thought was put into it) but it could be quite bad with that kind of change. Also, the longer rack/shorter tier rod combination makes all the angles get worse with travel. You already ran into the problem with running out of travel on the ball joint. I'm guessing that if you are changing to a power rack you also want to make the ratio quicker (shorter arm) which would make things worse. Also, have you checked the rack ratio (mm travel per rev of the input)? That could throw things off as well-- for better or for worse.

If I have all the dimensions I can calculate the Ackerman numbers... but don't forget that the longer arm will give you a slower ratio too.

Thanks Jeff for taking the time to explain the associated problems of what I was doing. Not to much engineers speak, I can get my head around that.
I am going to remove the RX7 rack and get a Miata (which I was originally after). The Rx7 rack will have to become garage wall art as I modified the aluminium mount are a bit.
Glad there was an engineer that was willing to explain.

Cheers Mal

 

[Tiger tamer]

Mayf has some good info on his site... and ya.. if you want to have something close to perfect steering just call Mike $$$... or Dale $$$$$ for a complete custom front end.
There is still some room though to make slight improvement to the existing setup.
While those RV8 arms may bolt up, and it's true that the longer the arm will slow the 'effective' ratio, it also puts it slightly closer to the rack centerline so not as bad as it seems because it will lessen that angle. That's why the MGB arms help the ackerman.The bigger issue with those RV8 arms is that the tie rod end will be even farther inboard from a good 'ackerman' point
Mal... sending you the long version by email


Jim
B382000446

Thanks for the email Jim. Explains the correct ackerman angle well.
I had a play with the pic of the MGv8 arms as well and figured that they probably would not help.
I will keep in touch.

Cheers Mal