1989 Homelite-Jacobsen 20" Mower

1saxman

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I remembered the problem; the new-style driver has the key made into it so the crankshaft must have a keyway that starts at the bottom. The old way was the driver has a keyway in it that fits a separate key in the crank - the complete opposite. The crank has a short keyway for the Woodruff key but it doesn't extend anywhere near the end of the crank. So, there was no reasonable way to adapt the new blade driver to the old crank.
However, I like the idea of checking around for an old one that will take the new blades. I know of two places right away that have 'mower graveyards' behind the shop. :)
 

tom3

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I'll just throw this out there. There have been a couple million mowers built with a single bolt mounted blade. I'd probably grind off those two outer knobs and go with a standard single bolt and heavy washer type blade mount if finding a workable blade is a problem. 3.5 horspower is not going to twist that blade off.
 

1saxman

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Grinding off the locating pins was one of my first thoughts, and I will definitely consider doing it when the time comes for another new blade and if I still have it. At this point I'd really like to find a good home for it.
 

1saxman

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I think this one's time is just about up. Engine is still good, deck is good, but the blade is obsolete, it needs another set of wheels and axles and the bag is wearing out. Plus the major factor is I just don't need it and I have no room for it.
Oh, BTW, the problem with the post-1994 blade drivers is they have a built-in key, which matches a shaft with a continuous slot, or 'keyway'. My driver has a built-in keyway to fit a shaft with a Woodruff key or perhaps a continuous key.
I probably won't be able to throw this mower away but I would gladly give it to someone who wanted it. Maybe I'll clean out my shed and keep it around a little longer as a very light and maneuverable trim mower.
 

1saxman

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I think I found an adapter that will work - just like the old one except the blade pins are farther apart (2") which will allow the use of a common 20" generic blade. Yes, it also appears to be thicker in the bottom surface (by the drawing provided) as you mentioned. I'll scribe in the deck where the current blade hits and see if I think I might have to set the deck height up a notch after checking where the new blade hits. Of course, the existing blade already would scribe lower than the original blade because of its design, so I'm probably looking at about a 1/2" total adjustment which is one notch. I just have to make sure the blade remains above the deck opening - if it doesn't this plan is toast.
Assuming the adapter fits, it really solved the problem, because now I can give/sell it to somebody who will use it without trying to tell them how to modify a blade to work, or just keep it around if I can make some room in the shed.
 

1saxman

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BTW, just looking at my picture above showing the last authentic blade I could get for it, you can see that the blade would scribe the deck probably about 5/8" up from the edge, so I'll use that as my desired value. Man, you never know how an old picture will come in handy some day. :)
 

1saxman

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Well, it worked! The adapter is taller than the old one but the new blade is straight instead of the previous generic blade that had 'drooping' ends. The result is the new blade scribes the deck about 1/4" above the lower edge which is good enough. It also clears that ring plenum under the deck which is another good thing. Very close tolerances on this deck - the original blade was designed to hug that plenum to get all of the vortex effect possible for efficient bagging. I probably have lost some of that efficiency but it basically works great, and now a blade swap is just that, not two hours over the vise modifying a blade that really doesn't fit.



 

1saxman

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After some careful measuring, the blade is about 1/4" lower than the marking on the wheel adjusters, so a setting of 3" is really 2 3/4". Consequently I set it at the next setting which is 'High', which will give about a 3 1/4" cut.
 
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