Rotary Cutter Question
- Thread starter Bluesteel
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fixitman123
Bronze Member
I hope the slip clutch solves your problem. I like to "beat the bushes" to find a good bargain also!
jaydee325
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Bluesteel, I'm just throwing an idea out as this intrigues me.
Are your blades pivoting free at the connection points on the stump jumper? My theory is that if one or more is stuck and the blades won't pivot, it would transfer additional stress to the sheer pin.
Just a thought. Good luck.
That is a good thought and you are on the right track. The blades are free, no binding or sticking. I think the problem is prior to engagement of the PTO when one or both blades are resting in toward center of cutter the initial centrifugal force throwing one or more blades outward is too much for the shear pin. I would suspect one blade toward center and the other one in normal position prior to start up creates an imbalance causing the violent shaking of the deck and the sheared pin.
Very good observation jaydee.
crankshaft21
Silver Member
I don`t think most of these people know how hard these ptos hit with the electric pto switch. My tractor has electric pto switch, but my bushhog has a slip clutch. I can see how this would shear a bolt. The best remedy is to install a slip clutch.
bumperm
Veteran Member
I just checked the original, still intact, shear bolt on my CountryLine 5' rotary cutter. It's a grade 2 bolt 1/2 diameter 3 1/2 inches long. My Kubota B3350 has an independent PTO, lever operated, and the spec says hydraulic clutch, though I've never tried moving that lever slowly as my impression has been that it was either on or off, but I'd try moving it slowly next time. I only engage the PTO at idle, and save for the banging around a bit until the blades both get slung out properly, no issues so far.
I know it's no finish mower, but with the mower deck 1.5 to 2 inches off the ground at the front, and a little higher at the rear, the shortest cutting length is still about 5". Measuring from the blade edge to the bottom of the "skirt" is 3 1/8". I'm thinking of raising the side skirts by maybe 1 1/2" (Plasma cut some out of the middle and re-weld it back together). Anyone done anything like this? Thoughts?
I know it's no finish mower, but with the mower deck 1.5 to 2 inches off the ground at the front, and a little higher at the rear, the shortest cutting length is still about 5". Measuring from the blade edge to the bottom of the "skirt" is 3 1/8". I'm thinking of raising the side skirts by maybe 1 1/2" (Plasma cut some out of the middle and re-weld it back together). Anyone done anything like this? Thoughts?
Guesseral
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I have the same cutter and the electric PTO also. YES it does hit hard when you start it, I usually start at a low idle and lower the cutter into high weeds or grass it seems to soften the starting blow quite a bit. I do not have a slip clutch and had the same problem with the sheer bolts at first I went to grade 8 and never sheered one but I dropped down to grade 5 and if I hit something that one will sheer and even sometimes after a hole lot of starts it will also sheer grade 2 just doesn't cut it but grade 5 is much better. Let us know how the slip clutch works out I would be really interested. I think you will probably have to cut the shaft down with the extra length of the clutch but there are directions in the owners manual.
bumperm
Veteran Member
Well I did test the PTO engage lever, always at idle of course, and moving it slowly does do a "soft start" of sorts - - a little softer than moving the lever quickly.
Also took the cutter to my shop and sliced off almost 2" from the stock 8" skirt. The stock skirt had about a 3/4" bent over edge at the bottom. Since I sliced that off with the "Bobbit Job", I welded on a 3/4" square steel tube to reinforce the bottom edge. Should be able to cut down to about 3", much better for taking the tops off the cheat grass.
Also took the cutter to my shop and sliced off almost 2" from the stock 8" skirt. The stock skirt had about a 3/4" bent over edge at the bottom. Since I sliced that off with the "Bobbit Job", I welded on a 3/4" square steel tube to reinforce the bottom edge. Should be able to cut down to about 3", much better for taking the tops off the cheat grass.
I installed a new slip clutch today. I repainted the mower gear box and replaced the rusted bolts on it with stainless steel. Installed a drum shield and shortened the PTO shaft 4". I haven't used it yet but probably will in a week or so if the rain holds off.
bumperm
Veteran Member
Bluesteel,
You are probably aware stainless fasteners do not have the same tensile strength as high strength steel fasteners. Stainless bolts are typically just a little stronger than Grade 2 bolts but nowhere near as strong as Grade 5 or 8 and as such should not be substituted in those applications where strength is important.
Not sure which fasteners you are replacing, though if it's to mount the gearbox to the deck, I'd question if stainless would be up to that. Stainless is good in many applications, however when used with non-stainless materials the dissimilar metals can promote corrosion in less noble metals. In most application I use anti-seize when using small SS fasteners to prevent galling.
for more info; https://www.boltdepot.com/fastener-information/materials-and-grades/materials.aspx
You are probably aware stainless fasteners do not have the same tensile strength as high strength steel fasteners. Stainless bolts are typically just a little stronger than Grade 2 bolts but nowhere near as strong as Grade 5 or 8 and as such should not be substituted in those applications where strength is important.
Not sure which fasteners you are replacing, though if it's to mount the gearbox to the deck, I'd question if stainless would be up to that. Stainless is good in many applications, however when used with non-stainless materials the dissimilar metals can promote corrosion in less noble metals. In most application I use anti-seize when using small SS fasteners to prevent galling.
for more info; https://www.boltdepot.com/fastener-information/materials-and-grades/materials.aspx
I replaced the 8 bolts on the front of the gearbox. I did use anti seize. Just about any fastener subjected to weather I replace with SS depending on strength and application. The slip clutch is mounted with grade 8 bolts. Thanks for the link.
Here are some similar links:
