Slip Clutch PLUS Overrunning Clutch?
Printed From: Unofficial Allis
Category: Allis Chalmers
Forum Name: Farm Equipment
Forum Description: everything about Allis-Chalmers farm equipment
URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=195692
Printed Date: 17 Jun 2025 at 10:29am
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Topic: Slip Clutch PLUS Overrunning Clutch?
Posted By: dfwallis
Subject: Slip Clutch PLUS Overrunning Clutch?
Date Posted: 14 Jun 2023 at 8:08pm
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It seems to me that a CA needs BOTH a slip clutch and an overrunning clutch. I didn't find any combos. Is there such a combo? I want to absolutely protect from damage and from pushes from a brush hog or similar high mass rotating device. Doesn't having those two in series cause difficulties connecting or is there that much slack in the typical PTO drive shaft?
I guess the term overrunning is imprecisely used. By it I mean uni-directional torque application with 'freewheeling' in the opposite direction. Some use the term overrunning to mean a friction (slip) clutch. This claims to be a combo but isn't really clear. https://www.bare-co.com/files-pto2002-pto61a" rel="nofollow - https://www.bare-co.com/files-pto2002-pto61a Sorry for all the newby questions :(
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Replies:
Posted By: MACK
Date Posted: 14 Jun 2023 at 8:35pm
| Most better cutters have a slip clutch on them. The over run can be be on cutter or tractor either way. Most go on tractor. MACK |
Posted By: dfwallis
Date Posted: 14 Jun 2023 at 8:47pm
Several things I've looked at just say shear bolt :(
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MACK wrote:Posted By: Allis dave
Date Posted: 14 Jun 2023 at 8:58pm
| I shear bolt could be ok too. Use a soft grade2 |
Posted By: KJCHRIS
Date Posted: 14 Jun 2023 at 9:32pm
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If your cutter doesn't have a slip clutch now it likely has a shear bolt. It can be on either end of shaft; tractor end coupler has 2 - 1/4" or 5/16" bolts, on the gearbox end it's likely a 3/8" bolt thru shaft coupler & shaft and no keyway slot in coupler. My 7' JD rotary cutter uses grade 5- 3/8" bolt style according to manual, I've broken maybe 5 or 6 in 20+ years. Most farm & home type stores can get you an inexpensive low HP over running clutch. The units you posted "are" a combination unit, but they're quite expensive. The over running clutch is in the center, slip clutch is the outer parts. We had similar ones for front mounted 8' & 9' snowblowers in a snow removal fleet. ------------- AC 200, CAH, AC185D bareback, AC 180D bareback, D17 III, WF. D17 Blackbar grill, NF. D15 SFW. Case 1175 CAH, Bobcat 543B, |
Posted By: HudCo
Date Posted: 14 Jun 2023 at 10:49pm
| you want part number sma 971-68386 over running clucth for your brush hog slips on your pto and your brush hog pto shaft slips on it you may have to shorten brush hog pto shaft 4 inches , 2inches each side you dont want it to bottom out |
Posted By: Gary Burnett
Date Posted: 14 Jun 2023 at 11:14pm
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AC brush hog has both |
Posted By: dfwallis
Date Posted: 15 Jun 2023 at 7:52am
Cost isn't a concern (within limits). I am interested in one with adjustable torque/slip though. A 26hp tractor needs a different setting than a 60hp tractor.
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Posted By: SteveM C/IL
Date Posted: 15 Jun 2023 at 10:21am
| Whatever you do try to keep slip clutch out of weather. The discs tend to "rust" to the plates and no longer slip. Wrap it with some kind of weather resistant material if parked outside between use. Most manuals will say to loosen and spin to free up before use then retighten. Who does that?? |
Posted By: ACinSC
Date Posted: 15 Jun 2023 at 11:01am
| My manual says that Steve . Like you said I've never done it . When ours was new Dad was wearing his earmuff/radio and didn't hear it slipping . After a while he noticed the paint on the guard was turning black . Happy to say the dealer gave me a new slip clutch . |
Posted By: dfwallis
Date Posted: 15 Jun 2023 at 1:22pm
I went ahead and ordered the low end one: https://www.bare-co.com/files-pto2002-pto64 For 40hp and under...from yesterday's tractors. Quite pricey even for that one :(
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Posted By: DSeries4
Date Posted: 15 Jun 2023 at 2:45pm
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I do not think there is such a combo having both in one unit. A slip clutch and/or shear pin is meant to protect the mower and PTO driveline, and is part of the mower. The over running clutch disconnects the mower's inertia from pushing the tractor, and I will say it makes a huge difference. With your foot on the clutch, the tractor stops right away and you can shift gears without grinding. I have been using one for over 15 years - works great! ------------- '49 G, '54 WD45, '55 CA, '56 WD45D, '57 WD45, '58 D14, '59 D14, '60 D14, '61 D15D, '66 D15II, '66 D21II, '67 D17IV, '67 D17IVD, '67 190XTD, '73 620, '76 185, '77 175, '84 8030, '85 6080 |
Posted By: dfwallis
Date Posted: 15 Jun 2023 at 5:20pm
There is. I bought it, see above. By Bareco of NZ/AU.
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Posted By: MACK
Date Posted: 15 Jun 2023 at 9:28pm
| AC cutters had a over run clutch on the slip clutch. MACK |