Craftsman 42" Hydrostatic scalps grass from one blade!

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  #1  
Old 07-29-10, 04:49 PM
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Craftsman 42" Hydrostatic scalps grass from one blade!

Grrrrr!

What happened? Did a blade get bent? Aren't these blades heavy duty enough to withstand running into an above-ground tree root? I scalped such a tree root, and now can't remember if this problem occured before or after this.

Other than that, I have no clue as to why it cuts so lousy/uneven. It even does it when the following wheels are both down on the lawn. If it were caused from say the deck swinging, then I would think you would see CIRCULAR scalp marks when the swing lowered the deck to one side. But this really is not the case. It is an even scalping.

BTW - it is 2-blade deck. Also the V-belt was just changed out to a New Craftsman replacement, with proper tension, and this did not help it.
 
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  #2  
Old 07-29-10, 05:22 PM
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I'd say you bent a blade or a mandrel. Can you park it on a flat spot, like your garage floor, peep under it and slowly rotate the blade. If it's a bad bend, the difference should be apparent. You might have to measure the difference in height of the ends of the blade.
Personally, I'd rather have a blade that absorbs the shock of hitting a tree stump rather than transmitting that shock all the way to the deck possibly bending the deck.
 
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Old 07-29-10, 05:49 PM
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Deere has a dandy blade height checking device, but you can make your own. Just kind of an inside dimension caliper to measure from the ground to the blade. Make sure your tires are properly inflated as a low tire will tilt the deck.
 
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Old 07-29-10, 05:49 PM
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The deck top looks even, the mandrels both appear to be perfectly perpendicular and tight to the deck. I can't get it up high enough to look underneath. Thinking of driving up some home-made ramp. (Am not keen on trying to remove all these arms and linkages and pulling the deck off and out from under the mower.)
 
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Old 07-29-10, 05:54 PM
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Originally Posted by goldstar View Post
Deere has a dandy blade height checking device, but you can make your own. Just kind of an inside dimension caliper to measure from the ground to the blade. Make sure your tires are properly inflated as a low tire will tilt the deck.
Never thought about the tires - but I doubt that is it - but will check. Thanks for the tip. After the easiest ways to check.

Is my problem something rather odd, with dual-blade lawn tractors, or is this kind of common, for reasons I stated? I don't care as much as my dad, who has to have a perfect lawn or else! (Gulp!). We sometimes share the mower. And I probably caused it! (Gulp, again).
 
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Old 07-29-10, 07:09 PM
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I agree with checking tire pressures first.
Use a jack to raise the front end, rotate each blade to a point you can measure or mark it against the deck, then rotate it and the other end should be close to the same point. Check this on both blades.
If you have grass piled up on the top of the deck you could have cracked a spindle housing and not even be able to see it.
Could also have spindle bearings bad. Grab the blade and try to move it inside the housing, any play at all could be a problem...
 
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Old 07-30-10, 01:02 AM
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Hitting a root above the ground can definitely bend a blade and this is probably the case if the tires are set right.
 
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Old 07-30-10, 02:23 AM
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Your best bet is to remove the deck, doesn't take long.
Stand the deck on it's back edge, position the blades tip to tip.
You can probably see a difference in the cutting plane of tips, rotate each blade 1/2 turn and re-check.
Also should be obvious if a blade is bent.
However, what is apted to have happened is the part of the deck the left mandrel is attached to, has been distorted.
This can be verified by laying the deck down and stretching a string across the top of both pulleys.
you will most probably find a space between top of left pulley and string. if so, the deck has been distorted.
This was(is) such a common problem, particularly on the 42" decks, AYP made a tool(DS-100, $150) for straightening the deck.
If this is the case, I can suggest a method that costs nothing. I bet I've straightened 6-8 decks in last several years.
hth
 

Last edited by GlenM; 07-30-10 at 02:30 AM. Reason: add'l info
  #9  
Old 07-30-10, 04:28 PM
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Originally Posted by GlenM View Post
Your best bet is to remove the deck, doesn't take long.
Stand the deck on it's back edge, position the blades tip to tip.
You can probably see a difference in the cutting plane of tips, rotate each blade 1/2 turn and re-check.
Also should be obvious if a blade is bent.
However, what is apted to have happened is the part of the deck the left mandrel is attached to, has been distorted.
This can be verified by laying the deck down and stretching a string across the top of both pulleys.
you will most probably find a space between top of left pulley and string. if so, the deck has been distorted.
This was(is) such a common problem, particularly on the 42" decks, AYP made a tool(DS-100, $150) for straightening the deck.
If this is the case, I can suggest a method that costs nothing. I bet I've straightened 6-8 decks in last several years.
hth

You are on the right track.

I started to work on it this morning. The left blade is bent about 1/4 inch. I was able to lift deck up on a 4 x 6(one side at a time) to easily unscrew the blade without dropping the deck. I wedged the blade in a heavy metal crotch on my farm tractor ands it took me many tries of springing the blade up to 4 inches to straighten it! But i did. I put the blade across a flat tabletop to confirm I got it straight when the center of the blade was flat on the table top.

Then I sharpened the blade, and rechecked it after sharpening. Reinstalled.

Then I rotated the right blade and found nothing out of the ordinary - at first glance. I removed the blade and sharpened it. Reinstalled. Then I rotated the blade with my finger locked around the deck and pointing upward, touching the outer edge of the blade, and rotating the blade 180 and seeing if that blade also skims my finger tip. Nope. I found that blade off by about 1/8th-3/16th inch. I repeatedly did this test to make sure I was not in error. Oddly, this blade is flat, when placed on the table top. So this makes no sense to me. Even if the mandrel was tilted, this should not affect one side of the blade being off from the other. And as much as i could tyell, the blade locked onto that star and tightend squarely tight to the bottom fo the mandrel.

What I plan to do, is take off both blades and recheck for flatness. Then put the left blade where the right one is, and redo the test.

But this is not the half of it. I did what you suggested, without even seeing your post. Tip to tip, the 2 blade tips are off either 3/8ths or 1/2 inch, depending on what blade tip is pointing toward whichever other blade tip.

Now after reading your post, I will straight edge across the pulleys.

Upon all this observation I was doing, I discovered the left mandrel is new with new bolts! I asked my dad if the local lawnmower shop did it. He said that he never took the mower in. It just so happens though that the lawnmower shop worked on that very mower before we bought it from someone out of town. A real coincidence.

Is it common at all for a person to loosen the mandrel- to- deck bolts and put a spacer say under one of them to straighten such a problem, if the mandrel pulley test shows some kind of space/tilt?
 
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Old 07-30-10, 04:31 PM
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Originally Posted by cheese View Post
Hitting a root above the ground can definitely bend a blade and this is probably the case if the tires are set right.
Amazingly though, how on earth couLd it bend, it if it took me flexing the blade about 4 inches, multiple attempts, to straighten that obviously spring-steel blade?
 
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Old 07-30-10, 04:34 PM
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Originally Posted by BFHFixit View Post
I agree with checking tire pressures first.
Use a jack to raise the front end, rotate each blade to a point you can measure or mark it against the deck, then rotate it and the other end should be close to the same point. Check this on both blades.
If you have grass piled up on the top of the deck you could have cracked a spindle housing and not even be able to see it.
Could also have spindle bearings bad. Grab the blade and try to move it inside the housing, any play at all could be a problem...
No play in the mandrel bearings.

Forgot to check tire pressure. Will do that tomorrow.

Do not physically see any problem with mandrels from top or below.
 
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Old 07-30-10, 09:28 PM
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You had to pull that blade 4 inches because you were doing it slowly, and perpendicular to the plane of the blade. It hit the root at near 4000 rpm, the impact was very different. Think of getting hit by a bb that was thrown at you, then think of getting hit by a bb out of a bb gun shooting it at 700 feet per second. Same principle.

The mandrel may not be bent, but the mandrel shaft may be. I've seen these bend many times. To tell, put the blades tip to tip, then rotate one 180 degrees. If the tip to tip measurement is not the same, then the blade is bent or the mandrel shaft is bent. Try the other blade the same way.
 
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Old 07-30-10, 11:16 PM
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Maybe a few pics of piles of bent and broken blades from hitting tree roots, or mole hills, or Tposts, or dog droppings or....
Like cheese mentioned, these are spinning at nearly 4000 turns every second...just how many times did it hit that root before you got it stopped....
 
  #14  
Old 07-31-10, 03:22 AM
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Cheese's idea of checking for bent jackshaft is an excellent one. He and others have worked on a whole lot more of these than I have.
I'm just posting from personal experience on a dozen or so of decks brought to me that were cutting uneven.
I would still tighten a heavy string acrost the two pulleys to see if there is a space between the string and the pulley.
If there is a space, measuring the space at 4 different locations on the pullley can verify a bent(or not) mandrel shaft.
If space is same, the deck is bent and needs to be pulled back up to cut even,
fwiw,
thanks,
 
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Old 08-01-10, 10:31 AM
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Originally Posted by cheese View Post
You had to pull that blade 4 inches because you were doing it slowly, and perpendicular to the plane of the blade. It hit the root at near 4000 rpm, the impact was very different. Think of getting hit by a bb that was thrown at you, then think of getting hit by a bb out of a bb gun shooting it at 700 feet per second. Same principle.
Okay. Someone asked me if I tried to heat it to bend it. No. Does that work?

The mandrel may not be bent, but the mandrel shaft may be. I've seen these bend many times. To tell, put the blades tip to tip, then rotate one 180 degrees. If the tip to tip measurement is not the same, then the blade is bent or the mandrel shaft is bent. Try the other blade the same way.
When looking at it from the bottom, I presumed that where the blade is attached to the bottom, that there is a bearing right there. How can anything bend right there?

Can you post a picture of say an exploded view (or betteer yet, an x-ray type view) of a mandrel? Once a person sees the construction, then it might be obvious where the problem is.

If the shaft got bent, wouldn't on the blade-tip to blade-tip visual test cause the one blade to be 1/2 inch below the tip of the other blade on 180 blade rotation, and be 1/2 inch above the other blades tip upon full 360 rotation, if the shaft were bent?
 
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Old 08-01-10, 10:40 AM
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Originally Posted by BFHFixit View Post
Maybe a few pics of piles of bent and broken blades from hitting tree roots, or mole hills, or Tposts, or dog droppings or....
Like cheese mentioned, these are spinning at nearly 4000 turns every second...just how many times did it hit that root before you got it stopped....
It made a quick E-A-Y-R-U-T sound (like feeding a carrot into a juicer) and scalped the top of the root.

Yesterday though, when I mowed the mound in MY yard, the blade dug into the mound and made a circular ring, not just the grass, but through the grass, 2 inches into the dirt! I've never seen anything quite like that before. Here I had just sharpened the blades - naturally! These tractors must be worthles on all but perfectly flat lawns!!!!!
 
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Old 08-01-10, 12:53 PM
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Yes there is a bearing there, and yes, the big thick shaft still bends right there at the blade. I've replaced an arm load of them this summer already. Look at a replacement shaft and you can see the flat head that can bend over on a tilt and cause uneven blades.
 
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Old 08-02-10, 04:49 PM
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But if the shaft gets bent, wouldn't that cause, as I said in previous post, the blade to climb higher at 1/2 rotation and then dip lower upon full rotation? Mine does not do that. If I get no such deviation, I am thinking I must need a spacer between the blade and the underside of the mandrel. That new mandrel may be mounted with washers where the other one wasn't?, or vice-versa, or it was for a different model tractor deck? ???
 
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Old 08-02-10, 05:03 PM
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Stretch a string across the top of the pulleys..............
 
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Old 08-02-10, 08:47 PM
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Yes, that's what I said... the tip to tip measurements will differ when you rotate the blade 180 degrees. There are no spacers or washers to be used to shim the mandrels. The need to do so is an indication of other problems. Did you do the string?
 
  #21  
Old 08-03-10, 04:35 AM
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I don't have a hydrostatic, but I had the same problem and found the casting that holds the bearings and shaft for the blade broken off of all 3 mounting points.
 
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Old 08-08-10, 03:28 PM
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Originally Posted by cheese View Post
Yes, that's what I said... the tip to tip measurements will differ when you rotate the blade 180 degrees. There are no spacers or washers to be used to shim the mandrels. The need to do so is an indication of other problems. Did you do the string?
Didn't need to. Yes the deck is bent. When I put on my far-sighted glasses, and using my new super bright LED penlight - there it was! - a crease in the deck at the center facing mandrel bolt! This crease means the mandrel leans in towards center, causing the center-facing tip of the blade to nosedive down compared to the center facing other blade tip.

I already prepped for mandrel and pulley removal by cracking loose and then lubing the threads on the 3 mandrel bolts and the pulley nut, and jostling the pulley loose by hand. My next project will be to drop the mandrel out the bottom(to get it out of the way) so I can crow bar the depressed deck area back up in the air(hopefully), at that bolt, without pulling the deck.
 
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Old 08-08-10, 09:03 PM
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Darn, that's the hardest thing to fix accurately when talking about things that make uneven cuts. It's also probably the least common thing to have happen. Usually the mandrel breaks or the shaft bends before the deck actually yields to the impact. Oh well, now you know what the problem is and can work at it until it is straight again.
 
  #24  
Old 08-09-10, 03:17 AM
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Chuck, you've worked on waaaaaaaaay more of these than I have, it's just my limited experience on a 1/2 doz or so has been as ecman described, deck bent.
maybe one where mandrel housing feet were busted.
I've had good luck in straightening back to almost perfect by
removing deck and mandrel guard.
Hooking a short loop of small log chain around mandrel where loop is at outside edge of deck.
then using a heavy 5' prybar in between deck and inside chain loop, making sure chain is just under pulley, pulling back toward the 730-8 o'clock direction.
checking blade tips after each pull.
have to have someone stand on opposite end of deck to hold it down on last couple of pulls and checks.

which is essentially what the AYP tool does as demonstrated on page 38 of following document.
http://www.gardenresources.co.uk/con...5321635-78.pdf

hth
 

Last edited by GlenM; 08-09-10 at 03:33 AM. Reason: add'l info
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Old 08-10-10, 06:45 PM
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I'm hoping I do not have to remove the deck. I will let everyone know how my attempts went when I have at it. It is sort of low priority on my to-do list since by me raising the deck height, it cuts uneven, but is less noticeble than when it is scalping the grass down to the yellow roots on one blade, when the other blade is yielding higher greener color grass.
 
  #26  
Old 08-10-10, 08:03 PM
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I have the same deck and it was doing the same thing. I pulled the deck off and the mandrel is broken. Where would i find one to order? thanks
 
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Old 08-11-10, 03:42 PM
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Is it also a Sears? Sears has a parts center, and a website I think you can order from. Or you'd think any of the larger lawnmower shops would either have one or could order one.
 
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Old 08-11-10, 04:06 PM
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Old 08-16-10, 10:28 AM
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Thanks I got the part, installed it and it cuts a lot better
 
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