Box Scraper Fixed vs Floating Box Blade

[JFD3940]

I have limited experience with tractors other than dragging a sandy riding arena for about 4 years.

How do you determine whether you need a fixed or floating rear blade when using a box blade. I'm going to be breaking up soil that has grass growing in it in order to make a road bed. I'll already have a straight blade available as well.

Thanks

 

[MarkV]

JFD welcome to the forum. My box is the type with a hinged rear blade. The idea is that the rear blade will float on and smooth the material left behind the cutting blade. It works reasonably well with the right type of material. Those who use a fixed rear blade will argue that you loose the ability to adjust your top link so the rear blade only hits the ground when you do your final finishing. That is true and I can see where it would be valuable at times.

Which is better? It is a matter of personal taste in my opinion. There are box blades that are hinged in the rear but include a bracket that lets you lock the rear hinge with a pin to have the best of both worlds. If I had more need for my box I would modify mine to do that.

More important than hinged or fixed is weight when it comes to a box blade. For cutting or digging soil the more weight the better to keep the box from bouncing along the ground rather than cutting in. If you were just moving loose material weight is not as much of an issue.

MarkV

 

[patrick_g]

I have 6 years experience with a box blade but none with a floating blade. I have hydraulic raise/lower scarifiers and top and tilt so can pretty much do whatever a "FIXED" blade design can do.

I have found a couple ways to get a smooth finish (before backdragging with FEL bucket) and one of them is to let the box fill to the point of overflowing and drag it over the surface in question with the cutting angle reduced such that it would only cut a definite projection sticking up in the way. Any low spot takes material from the supply in the box and raised spots tend to get loped off. Multiple passes are usually required and the throttle requirement is substantial as I have only 39 HP and a LARGE VERY HD 6 FT BOX BLADE WITH LARGE CAPACITY. Up hill work often requires low range (hydrostat.)

This gives a pretty nice finish, pretty much as nice as a box blade can give. I also use the hydraulic top lift to control spilling out dirt as the control is much finer than raising or lowering the 3PH but it would be so tedious as to be impossible to do this with out a hydraulic top lift.

I think the front to back dimension of the full box of dirt makes for a better smoothing action than the "point contact" of a rear blade. I have never bent a box blade, even when using it backwards as a dozer but one little oops and a rear blade is bent. (Always raise the rear blade before backing up because it you have it slanted one end will dig into the dirt and the blade will be bent before you can possibly react.)

Maybe I am parading extreme ignorance but I just don't see how a blade that is not FIXED would be such a great idea. Maybe one day I will get to see one in action and experience an "AHAH" reaction as my bulb comes on at least dimly.

I do like the rear blade for moving gravel accumulating at the road edges back out away from the edges. I'd probably like my rear blade more if it had hydraulic angle control instead of manual with limited resolution in placement.

Pat

 

[john_bud]

Pat,

don't feel too bad - here's some info to turn that bulb on. Or, maybe make you realize it wasn't off at all?

Box blades have 2 cutting blades. 1 facing forward inside the box and 1 facing backward outside the box. The rear blade on premium boxes can be either bolted solid or allowed to freely swing to the rear. (They are stopped by the support structure from swinging forward). Less premium boxes are either always freely swinging or most commonly always fixed in position. It's cheapest and easiest to have the rear fixed, so that's what most are.

It's not a super big thing, but having the option of swinging or fixed gives more options and can give a bit better performance in various situations.

If you are in the process of smoothing, you will set the box up so the nose is higher than the tail. That will then lift the box up, pivoting it on the rear blade. That puts some down pressure on the rear and can then leave your trail slightly lower. (it's actually pretty good at smoothing this way). But, if you have a freely swinging rear blade, it will not be the pivot point. The effective pivot is closer to the front blade due to the sides sinking in. This keeps the front blade somewhat actively cutting off high spots. No real improvement, (in fact it may not smooth as well in many situations!), but you can somewhat combine final cutting with smoothing to save time.

When you are actively cutting soil, the benefit is greater, but still not staggering. There is a much greater proportion of the box's weight riding on the front blade when the rear blade is swinging. That lets it cut faster and deeper. I did some testing with it free and fixed. On my mostly sandy soils with some sandy/loamy, the box fills in about 1/4 to 1/3 less distance. It also seems to keep cutting better when the box is full to overflowing.

In summary, you can dig a bit faster, maybe even a bit deeper with a swinging rear blade. You can also combine some cutting and smoothing operations and (maybe) get done sooner. On harder soils where the clods don't break up, fixing the rear blade and severely tilting the nose up, puts greater pressure on the clods and helps break them down. So, typically smoothing operations are better with a fixed blade.

It's not a huge deal, it's just an additional thing to diddle with.


Oh, the fear factor on dozing back wards isn't bending the rear blade. That is supported pretty well in most designs. The real fear is hitting a rock/root or just burying the box and stopping the tractor. That will typically bend the lower arms on the 3pt. (I know!) When backing up, it's best to have the box 1" tail high to dead level. A good starting place is 1" high so you don't snag the ground.

jb

 

[jbrumberg]

Great Advise here. JB your actual experience is consistent with my hypothetical "head assessments"; now I can delete that data from my overloaded neocortex . Thanks- Jay

 

[patrick_g]

JB, My box blade has a fixed back cutting edge. Out of ignorance and lack of breadth of experience I didn't know there was another way. I followed what you explained and expect that in most instances the differences are pretty darned subtle.

I don't understand how their backing up bulldozing performance would be any different that fixed as they would not be pivoting in that mode.

I had a lower arm snap in two but not while backing up. I hired a REAL weldor to weld it back together and weld a reinforcement to widen my arms (vertically) on both sides in the area where the one broke. I get pretty wild backing up bulldozing and never bent anything. The repais hve held for a few years now.

Thanks for the description, I feel like I HAVE seen one now.

Pat

 

[AndyMA]

JB, My box blade has a fixed back cutting edge. Out of ignorance and lack of breadth of experience I didn't know there was another way. I followed what you explained and expect that in most instances the differences are pretty darned subtle.

I don't understand how their backing up bulldozing performance would be any different that fixed as they would not be pivoting in that mode.

I

Backing up when the swinging blade is forced into position there clearly is no difference. Pulling forward when the front blade is doing most of the work, I would agree that the differences are subtle. I've been using a 8 foot LandPride with swinging rear blade for over 20 years. I've also run many other with both types and to tell yo the truth I'm not sure I can tell you the difference from a performance standpoint. I certainly can tell the difference based on weight. The heavier the batter.

Andy

Andy