Grading Bulldozing With A Box Blade

[MChalkley]

glennmac - I don't think the physics lesson was so much missed as it was stated in different terms. The reason some tractors top links, or top link brackets, bite the green weenie when bulldozing backwards is because it's not designed for the stress in the opposite direction. And the reason it's more likely to happen to the side links, or side link supporting hardware, is because they're designed for tension stress, and not compression stress. In particular, I'm pretty sure the side link sway adjusters are not designed to handle nearly as much compression force as they are stress force.

 

[RPM]

Dealing with the stresses as pure compression or tension doesn't reflect the reality of the situation. The blade is almost 100% likely to strike an object off-center, so the loading will be asymmetric. You are therefore probably better off considering the loading on the 3pt as a lateral bending stress or a torsion.

My guess is that on a compact tractor you would have to have fairly significant speed to get enough travel up or down on the links to bend them. I'm betting it's the lateral motion or torsion that sets the process in motion.

Patrick (not patrickg)

 

[MChalkley]

Patrick - I agree 100%. That makes a lot of sense to me, too. I think that's why I bent more left-side sway adjusters than right-side ones. The right end of the blade was frequently slanted forward and tilted down a bit when I was grading roads, so it would be the most likely part to hit something really solid and that would put tremendous compression pressure on the left side, as well as tension pressure on the right side. The adusters were better able to cope with the tension pressure, as could be predicted by looking at them.

 

[billboe]

I too have used my box blade in reverse for bulldozing... I find that it is able to cut <font color=red>much</font color=red> better in that direction! I was recently (before all the rain!) doing some terracing and this was the method that worked best (by far!). However, in terracing, you are constantly pushing harder on one side of the blade. So far (knock on wood) I haven't had any problems. I do take it nice and easy tho...

 

[ewoss3]

Harv, I had to fix a bent lower link just last week from bulldozing in reverse. I ended up going to a machine shop that had a 12 ton press because my 4 ton would not straighten the link. While I was being charged $53.00 the machinist gave me a little lesson. He said take a straw and pull on both ends, now take the straw and push toward the center. Well I guessed what he meant and I won't be bulldozing unless I have to. By the way, a new link cost $94 at my dealer. sorry no pictures

 

[TresCrows]

Harv, unless one modifies a swing back type to have a lockable back then the only way it can be used for leveling is to be pushed backwards with the rear tilted up so that the inner blades is being pushed backwards. This is the same as tilting a standard box up in the front so that the inner blade is lifted clear of the ground and the box then rides on the rear blade. At least for me that is the case it seems.
I know there are many here who have far more experience with tractors than I ever will--nonetheless---I will continue to both bulldoze and level in reverse. It has had no delatarious effects upon the little BX, surely your big manly tractors can take a little bulldozing. It also seems the 2410 does well so maybe some of you guys have to large a blade in use. Frankly, the arms and the top link form a triangle. A triangle is one of the strongest structures, also an arch, when under compression loads such as when pushing a box backwards. Torsional loads are likely the culprit as someone mentioned but I think you guys are all tractor weenies treating your tractors like some kinda luxury car or something /w3tcompact/icons/wink.gif /w3tcompact/icons/smile.gif . Hades, bend the crap out of it and then buy another arm, If I bend one the next one will be homemade and the tractor will bend first--oops--broken in half Kubotas--here we go.
The boxblade is a mysterious device but clearly it was designed for both forward and backward use unless you think the blade on the rear is just a convienient spare holder or something /w3tcompact/icons/wink.gif .
J

 

[Anonymous Poster]

Harv, Let me add one or two bits of info to my previous post about reverse grading. I am going slowwwwww. 1st gear is necessary to give you adequate time to keep the blade adjusted. Yes you do sometimes run against objects. you HIT objects when going unreasonably fast for the situation. I feel sure it is easier to damage a compact or ag tractor in reverse than going forward, but the difference in quality of work offsets the miniscule chance of damage, considering the ultra slow speeds used. I also have the square adjusters as MarkC mentioned. Also the use of the bottom hole for the toplink at the tractor seems to give the tractor more leverage as opposed to the opposite, reducing wheelspin and increasing ability to pust objects. Maybe I am doing something wrong but my long terms results prove otherwise, at least to me.
Common sense should always dictate strategies......
Greg H

 

[RPM]

Re: <font color=blue>the arms and the top link form a triangle</font color=blue>

They do - but when you consider the extension of any two of the link anchor points on the tractor to the corresponding attachment points on the implement you are dealing with three quadrilaterals. These aren't as inherently rigid as the triangle - hence you will more likely get failure.

Patrick

 

[RPM]

<font color=blue>He said take a straw and pull on both ends, now take the straw and push toward the center</font color=blue>

That's a good illustration, but you need to be careful with it. Don't forget that for every action there is an equal and opposite reaction. Therefore, unless your implement is magically perfectly loaded in tension, there will always be compression on the links too ...

Patrick

 

[Harv]

<font color=blue>A triangle is one of the strongest structures</font color=blue>

Well, yes it is. It is strong because it is totally rigid, good for making geodesic domes and cranes and anything else you absolutely do not want bend or change shape. If our 3-pt was truly a triangle, though, we would have a helluva time doing any lifting with it.

Like Patrick says, it's more of a quadrilateral. The top link is distinctly higher than the lift arms at both ends, so there are effectively 4 "sides" to our structure. In addition, the implement's top link connection is designed to be "sloppy", so we hardly have a rigid setup.

All that being said, J, I pretty much agree with the general thrust of your message. These are rugged beasts for doing rugged work. I think the key here, though, is that even rugged beasts have limits, and they'll last longer if we stay within them. The trick, of course, is to discover what those limits are before[/b] we bust something.