What size square tubing for rear blade mount?

[BGL990]

I've got a very heavy duty blade about 7' long that I am going to make a 3pt mount/frame for. I will be pulling it behind my soon-to-arrive John Deere 990 (~40hp, about 4000lb with loaded tires, etc.).

My question is what size of tubing would be strong enough for the frame? I'm mainly wondering about the main beam extending back from the 3pt, as well as the cross member between the lift arms. I was thinking 3" or 4" square with 1/4" walls. I haven't had much chance to get to a dealer to look at "real" blades so I don't have a good feel for what might be strong enough. I expect, however, that my 990 in low gear could exert some pretty significant forces on everything if a corner of the blade get hooked on something.

If anyone has a similar size blade and feels like measuring the frame tubing, it would be much appreciated. /forums/images/graemlins/smile.gif

Brad

 

[Darren]

Definitely look at a couple of factory models. You should be able to do that on the internet. Look up Woods and Bushhog for example.

 

[BGL990]

Well, I looked, and found some nice pictures to use as a reference, but nobody seems to give any specs about the frame or mounts. At least not in regards to tubing size or thickness. /forums/images/graemlins/frown.gif

I'll keep looking, but dialup is slow ...... /forums/images/graemlins/tongue.gif

Brad.

 

[MadReferee]

When I built my super heavy duty landscape rake, I tried to copy what Landpride used on their rear blades. I settled on 4"x3" rectangle tubing with 1/4" walls. Plenty strong. I used a piece for the span between the lift arms and another piece for the arm going out to the rake. I used 2"x2"x1/4" for the 3pt tower and for a few diagonal braces. See the attached picture.

The nice thing about using 4"x3" is that you can cut a small section out to get a wrench into where the lift pin nut is and have plenty of clearance. Otherwise you have to weld the nut.

 

[MadReferee]

Here is a pic from another angle.

 

[BGL990]

Thanks for the pics! (And nicely built btw.)

That is very much like how I plan to build my blade frame (like there is really much choice for a 3pt mount ... /forums/images/graemlins/tongue.gif)

Good point about the rectangular tubing, but I'll likely weld "ears" on the horizontal crossmember to take the pins so the nuts are out in the open. I'm a little paranoid about welding nuts inside somewhere that would require a bunch of work to replace if they got stripped.

Brad.

 

[BGL990]

Just ran outside and took some pics of my own. Here is the blade of which I speak.

Front view.

 

[BGL990]

Back view. You can see it was set up to pin onto some sort of loader.

 

[BGL990]

With a 5 gal pail for size reference.

 

[MadReferee]

</font><font color="blue" class="small">( Good point about the rectangular tubing, but I'll likely weld "ears" on the horizontal crossmember to take the pins so the nuts are out in the open. I'm a little paranoid about welding nuts inside somewhere that would require a bunch of work to replace if they got stripped.)</font>

If you notice in this picture the horizontal crossmember has an end cap thru which the lift pin is attached. All you have to do is cutout the bottom 2" or 3" of the crossmember. With a 3" tube width this will give plenty of room to get a box wrench in there to access the lift pin nut. Welding the nut is not necessary. This method is simple to fabricate and makes for a nice clean and very strong installation.