In the last issue, we looked at several factors that went into the design of pull graders. Here’s another important consideration that space did not allow to be included in that discussion.
Grader literature often recommended the appropriate power supply, either in horses or tractor horsepower, for the machine in question. While ratings likely varied from one company to another, this table of data published by J. D. Adams is representative of how much power was recommended for various sizes of graders without allowing for the breed of horse:
|Grader Weight Range||Horses||Drawbar Horsepower|
|1,400-1,785 lbs. (635-809.6 kg)||2|
|1,400-2,110 lbs. (635-957.1 kg)||4||8-15|
|2,015-3,945 lbs. (914-1,789.4 kg)||6||10-25|
|3,500-4,225 lbs. (1,587.6-1,916.4 kg)||8||20-25|
Other types of equipment that encountered resistance from the ground, particularly scrapers, were also rated in this fashion, and woe to the operator who disregarded these ratings! Applying too much power under load risked several outcomes, all undesirable: Forcing the machine away from its work; excessive wear at best or breakage at worst; or having to take less than an optimum load to avoid the other two.
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