Re: Death wobble Quote:
Originally Posted by amit_mechengg
RBT has a steering box coupled to pitman arms, which is space saving.
Rack and Pinion has bigger racks below the engine and consume more space.
The biggest disadvantage of RBT is the dead spot/ slack in centre. No wonder safari turns a second after you rotate the steering wheel.
Variable rack and pinion has almost zero lag and gives perfect feedback.
Hydraulic assisted Rack and Pinion gives best feedback and Electronic Assisted are very light and with dull feedback. |
Thanks Amit, To help people understand your explanation better, I take the liberty to post some images on RBT and Rack Pinion set-up. Hope it helps understand the mechanisms better.
The following has a good list with nice explanation and interesting engineering drawings of most of the steering types: Steering Components (Automobile)
A old toyota worm roller steerting video:
RBT Explained: http://www.kfz-tech.de/Engl/Kugelumlauf-Lenkung
In a spindle at the end of the steering shaft, a thread-like channel has been milled to accommodate the ball-bearings. Through these ball-bearings it is connected with a (spindle-) nut. When steering, their cogs move the drop arm through a steering segment, causing a pivoting movement. Other connecting elements then transfer this movement to the tie rod/s. When they have reached the end of their respective channel, the ball-bearings are transported through curved tubing, to the beginning again. The gear ratio can be finely adjusted through the configuration of the ball-bearing channels and through the gear-tooth pitch between the steering nut and gear-tooth segment. The third figure above shows the hydraulic support. In this case, the spindle divides the interior of the recirculating-ball steering into two areas. Presuming a good sealing of the movable parts, pressure can now be applied, depending on the steering movement, to one side while at the same time, relieving the other side. Quote: Rack and pinion, recirculating ball, worm and sector 
Rack and pinion steering mechanism: 1 Steering wheel; 2 Steering column; 3 Rack and pinion; 4 Tie rod; 5 Kingpin.
Rack and pinion unit mounted in the cockpit of an Ariel Atom sports car chassis. For most high volume production, this is usually mounted on the other side of this panel
Many modern cars use rack and pinion steering mechanisms, where the steering wheel turns the pinion gear; the pinion moves the rack, which is a linear gear that meshes with the pinion, converting circular motion into linear motion along the transverse axis of the car (side to side motion). This motion applies steering torque to the swivel pin ball joints that replaced previously used kingpins of the stub axle of the steered wheels via tie rods and a short lever arm called the steering arm.
The rack and pinion design has the advantages of a large degree of feedback and direct steering "feel". A disadvantage is that it is not adjustable, so that when it does wear and develop lash, the only cure is replacement.
Older designs often use the recirculating ball mechanism, which is still found on trucks and utility vehicles. This is a variation on the older worm and sector design; the steering column turns a large screw (the "worm gear") which meshes with a sector of a gear, causing it to rotate about its axis as the worm gear is turned; an arm attached to the axis of the sector moves the Pitman arm, which is connected to the steering linkage and thus steers the wheels. The recirculating ball version of this apparatus reduces the considerable friction by placing large ball bearings between the teeth of the worm and those of the screw; at either end of the apparatus the balls exit from between the two pieces into a channel internal to the box which connects them with the other end of the apparatus, thus they are "recirculated".
The worm and sector was an older design, used for example in Willys and Chrysler vehicles, and the Ford Falcon (1960s).[1]
Other systems for steering exist, but are uncommon on road vehicles. Children's toys and go-karts often use a very direct linkage in the form of a bellcrank (also commonly known as a Pitman arm) attached directly between the steering column and the steering arms, and the use of cable-operated steering linkages (e.g. the Capstan and Bowstring mechanism) is also found on some home-built vehicles such as soapbox cars and recumbent tricycles.
| Steering - Wikipedia, the free encyclopedia
Last edited by AlphaKilo : 10th August 2012 at 13:04.
Reason: Edited large images and text
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