pull type grader

[cjcocn]

have blue can you explain why the blade needs to be as close to the middle as possible? i would of thought it needed to be as far to the rear? thanks

Let me have a stab at this ....

Having the blade in the middle minimizes the effect of either the front or rear tires encountering an uneven surface.

If your blade is at either end, then it will (for example) raise 4" when the adjacent set of tires goes over a 4" bump. Alternatively, if that set of tires goes into a 4" pot hole, then the blade will drop 4". This results in a less even graded surface.

If the blade is in the middle, then the blade will ride truer to the intended depth regardless of the action of the front or rear tires. This results in a more evenly graded surface, which would become more level with subsequent passes of the blade since each uneven area would now be closer to grade (so the tires would go up or down even less than the first time).

HTH

 

[streamin]

cjcocn,
I was wondering why they don't make the standard grader blades longer for that reason?

 

[hdbikercouple]

thanks,the way i was thinking with it in the back,tractor tires go over a 4 " hump blade moves very little, but if in the middle it would move 2". as for pot holes they would not be any as the blade would of filled them in.

 

[MikeD74T]

thanks,the way i was thinking with it in the back,tractor tires go over a 4 " hump blade moves very little, but if in the middle it would move 2". as for pot holes they would not be any as the blade would of filled them in.

Part of the problem is the potholes are never really filled in until compacted. If the blade is completely at the rear it digs a new pothole just past the first when the rear wheels drop into uncompacted soil. The new hole will be nearly the same depth as what the wheels sunk into. When the rear wheels sink into that hole they create another. With a blade in the middle optimally you cut 50% of the deviation each time as the blade only moves 50% of the distance the wheels at either end move. In actuality you are creating a wavy surface with the waves getting smaller each pass. The longer the machine the shorter & further apart the waves. Ultimately the waves will be fractions of an inch tall and many feet between. This process goes much faster when you have power enough to completely dig out the potholes in one pass leaving consistantly solid earth under the rear wheels. MikeD74T

 

[cjcocn]

cjcocn,
I was wondering why they don't make the standard grader blades longer for that reason?

oops!

streamin

Sorry to have mislead you .... I know very little about the subject beyond having seen them operate for most of my life (gravel roads that I have lived beside). That ain't saying much because I have seen planes fly too, but you wouldn't want me as your pilot!

The little bit of info that I provided to you is a good representation of the extent of my knowledge in this area. LOL .... as funny as it may sound, I didn't mean to come off as being knowledgeable about graders!

.... as for the follow up questions - I shall continue with my "well it seems to me" approach (although I should probably quit while I am ... ahead?). Hopefully have_blue or someone as knowledgeable will add to this thread as I am interested in learning more about the subject myself.

When you say longer, do you mean the blades or the grader machine itself? I can't see how a longer (or wider, as the case would be) blade would help? The length of the machine is probably limited by safety concerns and also by a longer machine's inability to properly grade corners, etc. It would be harder to keep a longer machine close to the edge of a gravel road without risking putting the tires off the shoulder, which would negatively affect the machine's grading performance. Using a wider (longer) blade to compensate for the increased length would increase operating safety concerns, especially where vehicular traffic was concerned.

As for the blade being at the rear wheels - grading isn't perfect. Washboard and potholes aren't 100% eliminated, even when it looks like they are. There is usually still some hardpack left on the road. The hardpack is usually filled in as the grader passes, but there is still essentially a hole left within the hardpack. The grader's wheels will compact the gravel fill, but will drop into the hole while doing so. If a grader blade was at the rear, it would still result in a less even surface.

EDITED TO ADD: Thanks Mike! LOL .... I will be quiet and resort to reading and learning.

 

[Dirtnut]

hey guys maybe i can help here a little. being an operator i have run cat graders from 120 to 16h models. with the blade being in the middle or even back past middle a bit is more of a leverage issue than anything and a visability issue. length does help some but when the front wheels go over a bump of any size the blade will still jump to. leverage is given by the long front end and the shorter back end wich is heavier. this helps keep the grader from sliding side ways, like when plowing snow with a blade on the front it is close to the front end and it doesnt take much to slide the front of a tractor. graders are for fine grading they only cut a little dirt at a time, however the wide blade makes up for that. that is why grader blades are long and not very tall compared to dozer blades. dozers with a 6 way blade out front react the same way. a long trac dozer is easier to grade with than a short track dozer, the blade has less effect on the dozer. and the closer the blade is to the dozer or the rear wheels on a grader the better. this is why the guys with snow plows on the front of their loaders have alot of trouble plowing the leverage out weighs the tractor especially when you get down pressure and lighten the front end. graders are tough to manuver because of thier length that is why they have so many pivot points and hydaulics. they articulate,steer,front weels tilt, and the blade can do any position you want. if you ever get inside one you would be amazed at all the valve controls 6-8 on each side plus electic switches over hydraulics on some of the handles. i wont even get into the GPS models. as for pot holes they can be filled but the best way is to use the ripper or scarifier rip through the hole a few times to eliminate it then regrade, this nitts the dirt together. the fill in a pot hole doesnt nitt and when it rains it holds water and lets the dirt slip back out. hope this helps.

 

[MikeD74T]

EDITED TO ADD: Thanks Mike! LOL .... I will be quiet and resort to reading and learning.

Chris, Don't stop -I agree 100% with your post. I think we were both answering at the same time & I just hit the submit button a fraction of a second sooner. Being 1/2 mile from the Atlantic puts me closer to GMT. MikeD74T

 

[ttkeeler]

thanks,the way i was thinking with it in the back,tractor tires go over a 4 " hump blade moves very little, but if in the middle it would move 2". as for pot holes they would not be any as the blade would of filled them in.

It's all about the geometry of the blade to the points or tires in this case touching the ground. How many short, short road graders do you see? They are usually very long for a reason and from what I recall the blade was pretty close to the middle of the wheel base.

 

[Renze]

in theory, the effect of bumps and potholes would be less when the blade is right in front of the grader wheels, because the grader wheels ride on grade.
However in practice, the dirt in filled potholes is softer than the uncut dirt, which means that the dirt will compact when the grader wheels drive over it, lowering the blade.

With the blade in the middle, the blade takes only half the bump.

 

[Dirtnut]

that is correct the length does lesson blade jump some. lay a 2 x 4 on the floor and pick one end up the end u pick up moves much farther. the pivot point at the floor barely moves. in theory the farther back the blade the better. but for design and practical use graders are built the way they are. yes single axle rear graders this can effect some on pot holes. but double axle graders weels float on a center pivot to help eliminate this problem. as i said before the pot holes should be taken out and regraded thus eliminating the dip problem. in a perfect world proper grading is always done best when cutting not filling. however having a roller work with the grader is the next best thing to perfect. it is best to grade on compacted dirt than fill dirt, less deviation with tires.