Cantilever Gate Draw Force

Whenever you hear someone talking about the performance of gate, the conversation usually revolves around a discussion of how much a gate weighs, whether or not it is a cantilever design or how many cycles per hour it is going to operate. These kinds of conversations, while entertaining, do not contribute a great deal to the analysis of gate performance.

Sliding gate, by their nature, needs a horizontal force on the gate panel which is carried on a set of 4 cantilever rollers or track with 2 internal truck assemblies and by the application of that force, cause the gate panel to move. This force is called drawbar pull and it is measured in pounds. Just how easy or difficult the gate is to move will determine how much drawbar pull must be exerted. We have all experienced having to push an automobile which has run out of gas. Assuming your experience took place on flat pavement, you were probably able to push the car to the side of the road or maybe to the end of the block. Chances are that the car weighed three or four thousand pounds but you were able to push it with a few extra grunts and groans. That effort probably took less than 100 pounds of draw bar pull even though the car weighed several thousand pounds!

Imagine, now, that the air was let out of the tires and the car had not been greased in five years and also it was on a rough and rutted farm road. How far would you like to try pushing the car?

These same principles come into play in moving gates horizontally. A heavy gate may be easy or difficult to move depending on how good the rollers and track surfaces are. If it has reasonably good hardware and the track is level, then it won't take much force to move it along it's track. Conversely, a light-weight gate may take three men and a boy to move if the cantilever rollers are old and rusty, or the track is bent or the gate posts are out of plumb causing the trucks to bind inside the track.

Get used to the idea of drawbar pull. It is something you can measure with a fisherman’s scale and if you sell an operator to someone for a specific job and then the specifications change, you have a shelter to stand behind. The new gate that moves smoothly today may be a bear a month from now. Wouldn't it be nice to put the scale on the gate and be able to tell the customer that the gate needs to be serviced and the operator is not really the problem when the gate does not move?

Remember the weight of the gate will not change, but the amount of draw pull to get it moving can change in a minute. If the gate or posts are hit which causes a failure of any of the gate appurtenances, you have a major change in draw pull. .  Protect yourself; deal in terms which you can defend. Drawbar pull.