1940 drawbar safety law?

I have seen similar references before during my tractor surfing, but wasn't as focused on them.

Does anybody know what that references? A law? A standard? I have been unable to find any specific references.

Thanks,
Dave IL

This link points to one of the ASAE drawbar standards for wheeled tractors. It will give you an idea of what a design standard is; in this case, location of hitch point with respect to tire contact.

As an Ag Engr graduate 40 years ago, I will tell you that overturning by pulling on a properly positioned drawbar doesn't happen. As the front of the tractor rises, the overturning moment decreases, and the tipping action ceases. This is NOT the case of a plow snagging a stone where momentum is the principle force. I know this bothers your sense of intuition, but only hitch to a properly positioned drawbar, and you'll be OK.

I agree with you that the pull alone will not flip the tractor with a properly attached load. However, when you state it can't happen, it's a bit misleading, because you are disregarding the additional flipping force due to power and traction. If you have the traction and the load is keeping the tractor from moving forward, then torque will do you in.

Longitudinal stability is NOT just a function of drawbar geometry. It is also a function of tractive coefficient. See pages 140-145 of the reference book link.

While these conditions might rarely exist in the real world. Telling people it CAN'T flip is dangerously misleading. Extreme traction conditions (we know they can flip if frozen down) and modifications to the weight - fluid in tires and wheel weights - can be just as deadly as hitch point modifications.

CAUTION - The referenced link is to a VERY large pdf.

• The Mechanics of Tractor - Implement Performance

I'd like to down load the link yo sent but I don't have the time this evening. The wording you have used in you note makes me believe that it's contained in that reference.

I have to agree with Jerry on the idea of this not being law. The IH fast hitches especially the one point on the offset tractors would never complied with any laws regarding flip up. Same would be true with the little Fords and Fergies that used a cross bar in the 3 point for a drawbar. Very useful items but ones requiring extreem caution.

Thanks