Monday, June 14, 2010

Why Does My HT Hop When I'm Raking?

Here are three key points to check.

First, is the frame level? Raking with the frame not level pushes the rake teeth away from their optimum “angle of attack”, causing them to push up rather than be pulled back as the rake moves over the ground, resulting in a “hop”. An improperly leveled frame also reduces the way the rake teeth vibrate and diminishes the rake’s screening action. Rake teeth are made curved to enable the tip of the tooth to lead the base of the tooth and maintain ground contact. The tip of the rake tooth where it touches the ground should NEVER be vertical to the ground, or it will negate this curvature. The tip should be running ahead of the base, not vertical or behind it. Proper tooth orientation is illustrated below.

Level, Not Level

Second, is the center pin as tight as possible? The nut on the center pin should be drawn up as tight as possible and then backed off just enough to get the cotter pin into the nearest of the two holes. When the unit is brand new the paint in this area may make it difficult to angle, liberally greasing this area will make it work easier. Retighten the nut after a couple of hours during the initial use. Keeping the center pin tight eliminates any “slop” and keeps the rake level with the frame and on the ground.

Finally, does the rake a hydraulic cylinder to raise and lower the rake? If it is a single acting cylinder it only uses pressure to raise the rake. Relieving the pressure allows the rake to go down and rest on the road; it does not put pressure on the rake, leaving a loose connection between the rake and frame. The factory lever assembly on the HT allows the operator to use the weight of the frame to keep pressure on the rake ensuring it stays in contact with the ground, that is why we recommend the use of a double acting cylinder to raise and lower the rake. A double acting cylinder pushes its ram one way to raise the rake and then pushes it the other way to lower the rake. This keeps the connection between the rake and the frame rigid and the rake in firm contact with the ground.