Steering Rack, Part LeMons..

[Rupunzell]

Made up a different set of blocks for the LeMons racer.
These move the steering rack forward to reduce ackerman
(reduction of corner entry understeer).

Rack with old rubber bushings and new with modified blocks:

Rear view of the blocks:

As installed in car:

View of the rack pinion gear inside the foot well. Note the altered position of the steering shaft U-joint.

Steering arm rod end is mounted on the opposite side relative to
stock. This is required due to the amount the LeMons exxe has been lowered and to keep the bump steer curve reasonable. The rod end and cone spacers will allow bump steer adjustment.

Bernice

 

[Black-Tooth]

OK... more "Rocket Science" here...

at least from my limited perspective...

My first encounter with Mr. Ackerman was back in '66 when I reversed the spindles on my 23 T Bucket in order to install a tie rod forward of the axle... look closely here:

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In doing so... the entire geometry was thrown off as the outside wheel would now rotate more than the inside tire and actually skid sideways. A bit of knowledge and a torch eventually corrected the problem.

I understand though that there is a triangulation aspect with respect to the rear axle that (at least initially) determines the angle that each spindle arm should be aligned with. There are also many ways in order to adjust or align or alter all this including moving the axle(s) closer or further from each other.

So I said all this (I guess) to simply ask... just what did you alter with the new brackets that impacted the Ackerman effect? I just re-read your post that said you moved the rack FORWARD which in effect is like lengthening the wheelbase and I would then GUESS that the Ackerman effect is thereby LESS... or a reduced difference in attack angles.

WOW... I dunno if I'm even close but I think I am... and if so... what did you think needed correction in the first place, and why and how did you come up with this solution... and how did you determine how much to move the rack forward in order to achieve it?

BTW... Did you drive the car yet to see how it actually works? (theory vs. practice???)

Keep it up Bernice... Great stuff!

 

[Rupunzell]

Vintage of Papa Tony?

Ackerman was invented to deal with wheel hopp in solid wheel wagons going around a turn due to the difference in outside -v-s inside turn radii.

All works fine on a 4 wheel vehicle with solid wheels and street cars that generate very low tire slip angles.

Once we put speedy racer into a race car with flexi tires generating significant slip angles, and significant cornering loads all that ackerman stuff no longer really applies. This is due to the amount of weight transferred to the outside wheels and tire slip angles.

Some time in the 1950-60's race chassis designers figured this out and began to reduce ackerman in race car chassis.. in some cased ackerman was eliminated completely or the parallel steering chassis.

Some race car chassis have adjustable ackerman.

The first time I heard of any X1/9 racer doing this was Kim Baker and later National Champ Bob Boig. In both cases, they altered the steering arm geometry at the upright. Another way is to move the steering rack forward. There are a circle track and NASCARs that have a slot on the steering arm upright just for this adjustment.


Bernice

 

[kmead]

I remember Kim Baker's cars. Eons ago when I lived on the east coast, we would have some of his prepared cars participating in our autox events. Watching a "stock" X out drag an early GTI was pretty interesting, all just to win a plastic trophy... Between him and his prepared Xs and Jackson racing prepped CRXs our results were often a bit skewed.

His Corvettes were equally interesting.

 

[Black-Tooth]

Well... I guess I really don't understand what...

"Reduced" Ackerman" is then?

If the axle is moved forward (in whatever way) is that a reduction and then... what does that mean exactly... less angle of attack by one wheel over the other?

If ya think its too much trouble to explain... we can do it another time... And overall, what does the "advantage" equate to? Better traction in a turn or ???