differences between 240 and 280 steering racks

[zKars]

When I get a free day (2025 at the rate I’m going) I’ll measure my vast array of steering racks and let you know!

At the very least, I have a known 75 rack that I can measure and tell you about.

I don’t understand rack and pinion ratio’s anyway.   One turn of the wheel produces a certain amount of rack movement. No ratio of nothing.

 

 

Edited March 28, 2021 by zKars

[Captain Obvious]

Quick look at the internets:

Moog Parts defines "steering ratio" as the ratio of how far the steering wheel turns to how much the wheels turn. For example, if a 360-degree turn of the steering wheel causes a car's wheels to turn 20 degrees, then that car's steering ratio is 18:1 (360 divided by 20).

So you cannot determine steering ratio simply by measuring the distance the rack moves for one revolution of the wheel.

However, If everything else in the system is the same (like the lengths of all the other steering members), then the rack that moves more per wheel rev will have a higher ratio, but I'm not sure (in the Z car realm) that we have nailed all that down for sure.

[Racer X]

2 hours ago, zKars said:

When I get a free day (2025 at the rate I’m going) I’ll measure my vast array of steering racks and let you know!

At the very least, I have a known 75 rack that I can measure and tell you about.

I don’t understand rack and pinion ratio’s anyway.   One turn of the wheel produces a certain amount of rack movement. No ratio of nothing.

 

 

Ratios and proportions were always difficult math for me. I really struggle(d) with math, and yet I pursued a career in engineering (shortly) and then became a mechanic/machinist. 

Go figure.

Anyway, as I understand it, the ratio for something (as in gearsets and pulleys and other mechanical things) is the difference between the movement of one part compared to the other. Or, In mathematics, a ratio indicates how many times one number contains another."

As the good Captain points out, Moog defines the ratio in terms of degrees. 

360 degrees divided by the 20 degrees the wheels turn equals 18, so the ratio is 18:1.

So if the rack moves the wheels 24 degrees for one turn of the steering wheel the ratio would be 14:1.

 

I think I got that correct. A bit easier than calculus, trigonometry or descriptive geometry (the math behind geometry).

 

 

 

[zKars]

The 75 rack moves 1.51 inches for one pinion revolution.

Feel free to convert that steering angle any way you like.