Car ball and nut steering

A different blog post from usual!

Modern cars have "rack & pinion" steering, which gives tight (minimal sloppiness or deadzone).

Many years ago, cars had "ball & nut", or "recirculating ball", steering. The main problem with this is a deadzone, or sloppiness, which got worse as the linkakes/bushes wore.

I was reminded of this recently, when read about the new 2019 Suzuki Jimny, and posted to this blog:

http://bkhome.org/news/201903/new-suzuki-2019-jimny-4x4.html

I was surprised that this Jimny still has ball & nut steering.

Back in the 70's I owned an early Suzuki 4wd, one of the "LJ" series, with a 2-stroke engine. I recall, it was dangerous on wet roads. Especially a wet road with tight bends -- I found that the steering would get out of my control, and I had to slow right down.

In the mid to late 80's, I owned an old Holden, an "EH" model I think, a 3-speed automatic. I was cash-strapped at the time, and bought this secondhand. Don't recall what price I paid, but do remember selling it for AU$300.

It had various problems, such as tending to overheat -- but they made engines out of iron in those days, it could survive repeated overheating.

It had the old recirculating ball steering, don't recall if it was power steering. It was worn, with considerable slack. Near where I lived, there was a dirt road, that turned to mud when it rained. I discovered that when driving home on that road, and the car lurched to the right, the steering wheel snatched violently out of my hands. I pulled the wheel left, and it got snatched out of my hands again as the car lurched to the left.

Thus I zigzagged across the road, until I had reduced speed to a crawl.

The problem was the tyres sinking slightly into the mud. If the front tyres turn very slightly from true forward direction, a small wall of mud then forces them to turn more. Which can happen due to the slackness in the steering linkages. When the wheels have been twisted more than a few degrees, the wheels get violently pushed to the side, and the steering wheel spins out of my control.

So, pretty awful type of steering, hey! However, I am over-dramatizing the risk. My Holden was old and the steering linkages very worn. If I had got it fixed, replaced some bushes, the steering slack would have tightened up considerably, and I would probably have been able to race straight through that muddy road.

Apart from the Jimny, apparently some trucks still have this, I don't know about other 4wd vehicles.

With the Suzuki 4wd cars, a popular after-market addon was a "steering damper", a hydraulic mechanism that will minimise the kind of scenario that I have described above.

It seems that Suzuki added it to the Jimny 4wd series, and it is in the 2019 model. Thank goodness. There is also power steering, so it would seem that the two mechanisms would be fighting each other -- well, apparently, it does cause the steering to have a "dead" feel, with no feedback from the wheels.

Why hasn't Suzuki gone over to rack & pinion steering for the Jimny? I don't know, there must be reasons. I don't know enough about the topic to guess why. More info here:

https://en.wikipedia.org/wiki/Steering

Quoting:

The recirculating ball mechanism has the advantage of a much greater mechanical advantage, so that it was found on larger, heavier vehicles while the rack and pinion was originally limited to smaller and lighter ones; due to the almost universal adoption of power steering, however, this is no longer an important advantage, leading to the increasing use of rack and pinion on newer cars.

The steering damper does make driving safer, however there is another concern. The deadzone means that the front wheels are not necessarily going in the direction in which you are pointing the steering wheel. This has been observed by testers of the 2019 Jimny on highway driving, where the car tends to wander to left or right, and has to be continually corrected.
This means that the driver has to be always alert, and it does make the driving experience more tedious -- though, the continual correction does become habitual. I also briefly owned a Suzuki 1.3 litre Sierra, the model after the LJ series and before the Jimny series, and I recall this wandering problem, but I adapted to it and found highway driving to be OK, if a bit odd.

Thought that I would post these interesting observations! 

Tags: tech