Figure 1. Detail of cone guide wheel.

Figure 2. Cone guide wheels on precision cultivator.

Figure 3. Cone guide wheels on carrot knifing rig.

Cone guide wheels are the heart of a precision cultural system (PCS). They allow an implement to follow along a shaped bed with no effort on the part of the tractor driver.

The cone wheels ride on the sides of the bed and guide the implement. The sway blocks or sway links on the tractor are removed or loosened so that the implement floats free laterally and is controlled by the guide wheels, not the tractor. All the driver has to do is keep the tractor between the beds.

What Are Cone Guide Wheels?
Cone guide wheels (Figure 1) are steel wheels shaped like a truncated cone. The angled surface of the wheels matches the sloped sides of the beds and provides guidance.

Using Cone Guide Wheels
Cone guide wheels are normally mounted so that the spacing between the wheels at the point where the cone is truncated matches the width of the bed top. It is best to use one pair of guide wheels on each bed, although this is not always necessary in multi-bed configurations. If the sway blocks or sway links are not removed or loosened, the effects of the guide wheels are negated. It is not a good idea to use cone guide wheels for vertical support or vertical gauging of the implement. The weight of the implement should not ride on the guide wheels. Most of the implement weight should be carried on the 3-point hitch.

Operations with Cone Guide Wheels
Cone guide wheels can be used to guide the planting operation if the planter is not mounted directly on a bed shaper. Once the crop has been precisely planted, cone guide wheels can be used for subsequent operations. The most common and important use of cone guide wheels is precision cultivation (Figure 2). Using cone guide wheels allows cultivation within 2-3 inches of the crop row without risk of crop damage and without any effort on the part of the driver. Any type of cultivator – sweep, rolling, rotary tiller, etc. – can be guided effectively. Other operations can also be guided, including sidedress fertilizer application, directed spraying, knifing carrots (Figure 3) and harvest operations such as undercutting carrots or onions.

Alternatives to Cone Guide Wheels
There are alternatives to cone guide wheels, but they are expensive and more complicated. Hydraulic hitches are available that move the implement back and forth for alignment on the row. Automatic steering systems based on GPS technology are becoming increasingly popular and can achieve the necessary precision, but these systems are costly (especially when this level of precision is needed) and are available primarily for large tractors.

In summary, cone guide wheels are a simple, robust, economical way to achieve excellent guidance of vegetable operations and are a critical component of PCS.