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PostPosted: Mon Sep 20, 2010 7:56 pm 
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Has anyone switched the miata front hubs from front steer to rear steer for a right hand drive car of course using the miata rack? Just wondering if it's a possible thing to do. To me in my head i don't think it would make a difference but then again I'm known to look over the small things.

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PostPosted: Mon Sep 20, 2010 9:10 pm 
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If you switch a front steer rack to the rear the controls will be reversed. Turn right to go left and vice versa. That's sort of a problems for most folks, unless of course your making it right hand drive.

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PostPosted: Mon Sep 20, 2010 9:16 pm 
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oddsaabs wrote:
If you switch a front steer rack to the rear the controls will be reversed. Turn right to go left and vice versa. That's sort of a problems for most folks, unless of course your making it right hand drive.


that's not what i'm asking. i'm asking if anyone has put the left hub on the right side and the right hub on the left side and flip the rack over so it can be used for a right hand drive car. i would like to know if there is any issues that i may be overlooking.

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PostPosted: Mon Sep 20, 2010 9:46 pm 
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Oops, my bad. I re-read your question only to discover that you do want to make it RHD.

I see no reason why it wouldn't work. As long as the rack was placed carefully to avoid bumpsteer, it should fly just fine.

Do you have room in front of the motor to do a rear steer rack? Pretty tight right there in most cars.

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PostPosted: Mon Sep 20, 2010 10:09 pm 
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Steering arms will probably have to be heated and bent to correct the ackerman angle.


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PostPosted: Mon Sep 20, 2010 10:37 pm 
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oddsaabs wrote:
Oops, my bad. I re-read your question only to discover that you do want to make it RHD.

I see no reason why it wouldn't work. As long as the rack was placed carefully to avoid bumpsteer, it should fly just fine.

Do you have room in front of the motor to do a rear steer rack? Pretty tight right there in most cars.


the way things look so far it looks like i'll have the room (r1 motor pushed as far back as it can go) i'll also have to see with the turbo placement and all..


"Steering arms will probably have to be heated and bent to correct the ackerman angle." could you elaborate??

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PostPosted: Tue Sep 21, 2010 1:50 am 
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Flipper_1938 wrote:
Steering arms will probably have to be heated and bent to correct the ackerman angle.
It appears to depend on design... I took my Fiero Spindles and swapped them side to side and ended up with decent Ackerman.

90gt has been playing with models of it and figures it's mainly due to where the rack is placed in reference to the pick-up points on the spindles. I have mine about the same distance behind the "line" as they are normally in-front of the "line" so it simply sees it as being the same, hence little changing in Ackerman angles. I have a very small powerplant and it left me lots of room to play with.

I was not aware of this before designing it or assembling it in my particular application. I simply stumbled into a arrangement that appears to work.

I will concur whole heartedly with oddsaabs in that the rack takes up more room than one would think and it needs to be looked at and planned for or somethings bound to get upset when another part invades it's space!

Try it.. you may end up with the same "benefit" I did. Let us know if your successful!

Good Luck!

KS

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PostPosted: Tue Sep 21, 2010 7:52 am 
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While it may be possible to do so, It is unlikely that the Ackerman will be right. You may get it to work as Botbasher did. Rather than trying to heat and bend the steering arms, you might just consider finding a LHD rear steer rack. Then it should work when flipping it over for RHD, keeping the Miata hubs front steer with the geometry they were designed for.

Just another option.

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PostPosted: Tue Sep 21, 2010 8:50 am 
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rx7locost wrote:
While it may be possible to do so, It is unlikely that the Ackerman will be right. You may get it to work as Botbasher did. Rather than trying to heat and bend the steering arms, you might just consider finding a LHD rear steer rack. Then it should work when flipping it over for RHD, keeping the Miata hubs front steer with the geometry they were designed for.

Just another option.



i may have enough room to keep the rack in the same orientation as it is in the front steer position but in the rear. i won't know for sure till i get the a arms done. i'v been keeping an eye out for another rack.

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PostPosted: Tue Sep 21, 2010 7:59 pm 
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rx7locost wrote:
While it may be possible to do so, It is unlikely that the Ackerman will be right. You may get it to work as Botbasher did. ....
OK... but that brings up a question....

What is the correct Ackerman for a Lotus/Locost? I know that tire type and several other factors contribute or detract from the baseline, but what is a good starting point?

I've always had issues with Geometry... in the sense that they ask "What is X?".. it's a letter, duh!! I have gone through Staniforths and searched the site but no one has really given baseline numbers to start from that I have found or been able to extract from the discussion.

So stating that it's unlikely to be right.... what is right? Not trying to be an A$$hat... my mind works better when I have a point to start from or to get to. Without even the OEM figures for, say... my Fiero spindles, "the correct Ackerman" becomes as ambiguous a goal to me in relation to the car as "X" does when working a geometry problem!

KS

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PostPosted: Tue Sep 21, 2010 9:37 pm 
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Uhmmm....... IIIII....... aaaaaa........

What is the correct ackerman? Heck, I don't know. I was just saying that if it was such to give acceptable handling in the donor, the likelyhood is that changing hubs left and right (front steer to rear steer) wouldn't feel close to being right. In most cases, I guess it depends, now there is a definitive answer. I am not a suspension guru.

Here is a writeup on Ackerman. 6 experts can't agree totally. Chances are that you couldn't get 6 people on this list to agree on how much is the right amount.
http://www.smithees-racetech.com.au/ackerman.html

Personaly, I just used the donor's hubs on my build and left sleeping dogs lie.

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PostPosted: Wed Sep 22, 2010 11:57 pm 
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I'd aim for as close to 100% ackerman as you can get, but I'm no expert. I do however understand how it works and the principles its based on make good sense to me. What it does for those who may be reading about this for the first time, is turn the wheel on the outside of the turn more than the wheel on the inside of the turn. This is done because as the car turns sharply (think low speed autocross, or just turning around in your driveway) the wheels will be tracing seperate arcs of differing radii. With zero ackerman both wheels will be steered an equal amount, so one or both wheels will be scrubbing along rather than both maintaining grip. With 100% ackerman, the inside wheel will be steered at a sharper angle to compensate for the smaller circle/arc that wheel is tracing compared to the outer wheel, and neither wheel slides.

Critics argue that once up to speed, and with the car set into a turn weight shiting will dictate the tire on the inside of the turn is only loaded very lightly while the tire on the outside of the turn is doing the heavy lifting and turning the car. So they will say it doesn't matter if the inside tire is scrubbing slightly since it is doing very little to actually turn the car. Some actually advocate anti ackerman steering as a means to reduce tire temps during high speed cornering that come about as a result of the tires being loaded differently and generating different slip angles. (I don't claim to understand this, but it's how I read it)

I've read a fair amount about it though, and the most convincing testimonial was from some race crew cheif. (sorry I forget the guys name, the team, the track, etc. but I want to say it was an old F1 team) I read where as a test of it's validity, unbeknownst to the driver Ackerman was gradually adjusted into a race car on a during testing and as ackerman was increased the lap times became marginally faster.

Image

Compare full ackerman to zero here:
http://www.compgoparts.com/TechnicalRes ... eering.asp

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