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Is mower deck rigidity all that keeps the blades aligned?


Fred_C_Dobbs's Avatar
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06-27-17, 12:52 PM   #1  
Is mower deck rigidity all that keeps the blades aligned?

The bridge across the bottom of the discharge chute has worn through and broken off on my Mom's old 2-bladed 42" Murray (WalMart) riding mower. I don't notice it cutting especially unevenly but I do think it's much more prone to "scalping," especially when the wheels on one side get a little elevated, like when cutting next to the base of a tree.

So I'm wondering if the structural rigidity of the deck itself is all that was keeping the blades parallel, so now when the mower chassis flexes it pushes the blades askew and makes the lower side more susceptible to scalping.

If this is the case, might this be fixable, or is the only fix to replace the mower deck?

 
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06-27-17, 01:43 PM   #2  
Making sure blades are balanced helps a lot. Past that, good pulleys and drive belts

 
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06-27-17, 02:01 PM   #3  
The mower deck is what holds the spindles and blades and so it is the deck that keeps them straight. If the deck is bent it can knock the blades out of alignment. A steel fabrication or welding shop should be able to weld in some simple patches or reinforcements if needed.

 
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06-27-17, 03:33 PM   #4  
It has nothing to do with keeping the blades level however it does act the same as the rest of the lower edge of the deck. If you go over tree roots, dips or other obstacles it that piece will raise the deck or keep the object from entering and encountering the blade. With out it you could easily wind up trimming tree roots and perhaps even get stuck by something like a rod or cut off pole or some such getting through the discharge chute such as in a turn. I am not 100% sure but I think some of those are bolted or riveted...you might look at a parts diagram and see if you can get replacement or you could find something suitable and weld or bolt it on...
I would certainly advise getting something in place...you only get one guess why I advise this


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06-27-17, 05:15 PM   #5  
The bridge across the bottom of the discharge chute has worn through and broken off
A riding mower deck is suspended from the tractor so it's not holding anything, it's mainly hanging there to enclose the blades, structural integrity is not being compromised.

Welding or bolting in a piece of metal across the bottom could be done but I doubt having it gone is all that critical.

 
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06-27-17, 06:42 PM   #6  
Welding or bolting in a piece of metal across the bottom could be done but I doubt having it gone is all that critical.
In this case why would the manufacture even spend the extra time, effort and cost to include it?
It is there for a REASON!


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06-27-17, 07:32 PM   #7  
All it does it keep the front of the mower deck from pushing under the deck and getting hit by the blades if you ram the deck into a root or something similar, and allow the deck to skid or slide across the ground or objects that pass under it in that area. It doesn't really affect deck level or the quality of cut.


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06-29-17, 01:56 AM   #8  
I get hung up on an unknown piece of buried metal
Doesn't make sense, the bottom of the shoot that the OP is asking about is at or near the height of the cut, lets say 3-4" high, how does something above the ground get hung up on a buried piece of metal.

Nobody is saying that the manufactures did not intend it to be part of the mower.
It simply wore off after many years of friction against the grass, and what ever else was run over. But the deck hangs from the mower so it's not a structural component of the mower and the OP apparently is still using the mower.

Replace it, leave it alone, it's just not going to stop the mower from continuing to cut grass.

 
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06-29-17, 04:10 AM   #9  
I think what we're talking about is a horizontal "skid bar" riding along the bottom of the deck's chute.

I'm guilty of maintaining a 1973 AMF (Murray) Mower that has a floating deck, and I'm now on my 3rd deck (and 3rd engine) with this machine. It's not my only rider; but that floating deck makes it ideal for mowing some of the more irregular rolling terrain among the 3-4 acres that I keep mowed. It's not nice and flat like a football gridiron.

The skid bar seems to be more of a consumable item on this kind of deck than most would suspect. It wore off of my 1st deck, and once gone, the vertical face of the deck absorbed the force of any irregularity that the mower encountered, and the front face was slowly bent inwards until it started making contact with the blades, and had to be manually pulled out and put back into shape.

In replacing decks, I've had to resort to having a Blacksmith fashion new Skid Bars, that guide the deck up and over any minor obstruction. The floating deck concept relies on the deck being suspended at just two points, fore and aft, at a yoke in the front and a kind of keel in the rear, both centered on the machine . . . . otherwise, the only connection is the belt.

Deck wheels on the sides of the deck, in the rear, provide some guidance in ensuring that the deck doesn't drag on the ground; but there are no such wheels in the front. The wheels are often up in the air, and only prevent the deck from getting closer than a minimum distance from the turf. The key to having this skid bar work properly, is to have it's nose fashioned in a curved-up manner like the nose of a ski, so that it will gently lift the deck up and over minor obstructions . . . . the same obstructions which, without the skid bar, will cause the deck to slowly succumb to wear in that area.

If the part is no longer available (as mine is), then I'd investigate the presence of a Blacksmith in your area to make the part; a very handy person to have a good relationship with.

 
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06-29-17, 01:36 PM   #10  
Thank you for all your inputs.

The deck is question is, as Vermont suggests, mounted fore and aft and nowhere else. I also have a 3-bladed 48" mower that has (antiscalping?) wheels on the mowing deck, but this one does not. And funny you should mention it, Vermont, because the "skid bar" on my mom's long ago wore off on the left front side of the deck and I occasionally find myself having to take a pair of channel locks to the bottom of it to bend it back out to stop it contacting the mower blades.

A friend of a friend is a rat rod builder and the best fabricator I know of who will work for beer. Looks like I'm due for a visit to the rat rod garage.

 
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10-05-17, 01:08 PM   #11  
You know, there's times when you do things so monumentally stupid that you're morally obligated to let the world know about it.

It took me six months to work it out but I finally realized why my mower has begun scalping so badly.



This is the leading edge of the left side of the mower deck. And there's a good 3/4ths of an inch of material missing from the bottom edge toward the outboard side. I mentioned above that this deck has no anti-scalping wheels, but it only just occurred to me what role the deck itself plays in providing the blades stand-off to the ground and preventing scalping.

And that's all I have to say about that.

 
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10-05-17, 03:03 PM   #12  
Posted By: Fred_C_ Dobbs ". . . I mentioned above that this deck has no anti-scalping wheels . . ."
Did the design of that Deck originally incorporate such wheels, or have they just fallen off ?

 
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10-06-17, 11:30 AM   #13  
Vermont:
Did the design of that Deck originally incorporate such wheels, or have they just fallen off ?
I can't say, because I've already said all I had to say about that.
[/Forrest Gump]

...but if I could say, I'd say it never had any.

 
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