over-running pto clutch
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Category: Allis Chalmers
Forum Name: Farm Equipment
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URL: https://www.allischalmers.com/forum/forum_posts.asp?TID=129192
Printed Date: 22 Jun 2025 at 6:21am
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Topic: over-running pto clutch
Posted By: LionelinKY
Subject: over-running pto clutch
Date Posted: 24 Sep 2016 at 11:03pm
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Somebody please explain to me the concept, purpose, and need for an over-running clutch for the pto especially as it pertains to working a rotary mower with a tractor like my WD45. We never used "bush hogs" on our farm but did all the other pto work associated with running a 100+ cow dairy farm. The WD45 did its share running haybines and harvesters, none of which ever damaged the pto drive no matter how many times the clutch was pushed in thereby stopping the pto dead. I have heard stories of people running their mowers and then busting the pto drives out of WD/WD45 tractors only to find out that it probably wouldn't have happened if they would have made sure to use an over-running clutch on the pto. Why do rotary mowers appear to be so much harder on pto drives than other pto equipment? I can understand a little oversight with a new product at first explaining why the oldest rotary mowers may not have a built in over-running clutch. Do ALL new mowers have over-running clutches on the pto now or only certain brands? I have a friend offering to buy a "bush hog" if I would be willing to use my WD45 to help him keep a small field mowed down. I would like to make sure that everything is set up correctly so as not to damage my tractor whether that means getting a particular mower or having an over-running clutch installed on my tractor pto. Any and all information will be greatly appreciated. TIA ------------- "My name is Lionel and I'm an Allisoholic" |
Replies:
Posted By: VAfarmboy
Date Posted: 24 Sep 2016 at 11:39pm
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Because if you don't have one and push the clutch in on a tractor without a "live" PTO the still spinning blades on the bush hog can drive the transmission through the PTO shaft (creating an unsafe situation), or bust the shaft. Same deal with the spinning flywheel on a baler. The overrunning clutch lets the pto driven implement freewheel rather than turning shaft and continuing to drive the tractor forward or breaking the shaft when you push the clutch in. The overrunning clutch snaps onto the tractor's PTO shaft not the mower. I am not aware of any mowers that have built in overrunning clutches. They all have slip clutches to protect the drive-line on the mower. Most tractors built since 1960 have a "live" PTO that is independent from the transmission so this is not an issue but on the older ones you need an overrunning clutch for some applications. Does your WD45 have a three point adapter or an aftermarket three point hitch on it? If not you will have to have a snap coupler hitch fabricated for the bush hog, unless you get a trailer type bush hog with a lift cylinder. |
Posted By: LionelinKY
Date Posted: 25 Sep 2016 at 12:19am
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Lots of WD45s also ran balers, blowers, and choppers all which have a rotating mass that doesn't like to stop abruptly. I don't recall ever hearing about pto issues unless it involves a bush hog. The slip clutch doesn't allow for the necessary freewheeling of the rotating mass after the tractor pto has been stopped? ------------- "My name is Lionel and I'm an Allisoholic" |
Posted By: Herb(GA)
Date Posted: 25 Sep 2016 at 2:31am
| The momentum of a large implement pushing the tractor forward is normally not a problem with balers or cutters because this usually occurs in the middle of a field. Bushhogs are often used in corners of fields or among trees and along fences, where one can readily get into a tight spot. I have broken off a couple wooden fence posts with tractor front axle/front wheel because of this inertia. This situation can be prevented by quickly placing the gear shift into neutral (not easy to do if there is a load on the geartrain).Herb(GA) |
Posted By: Jack(Ky)
Date Posted: 25 Sep 2016 at 3:18am
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As long as you use the hand clutch you don't need one of these. A WD has "live pto" as long as you use the hand clutch to stop forward motion and leave the foot clutch alone.JP ------------- '59 D14 '68 170 Diesel '81 7020 40 All Crop |
Posted By: tractorboy
Date Posted: 25 Sep 2016 at 4:10am
| jack is right. you wont have a problem, hand clutch works great for that. once youre used to it, it'll be natural, especially with your farm experience !! |
Posted By: Gary Burnett
Date Posted: 25 Sep 2016 at 4:35am
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I can't see how a brush hog driving a WD/WD45 forward a little is going to damage anything on it as it takes very little force to drive the tractor forward.I've run those tractors all my life and never had an over riding clutch on one and have never known anything to get damaged because of it. |
Posted By: DiyDave
Date Posted: 25 Sep 2016 at 5:33am
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Another thing to consider is balers have a built in ORC in the drive line, at least NH ones... As others have said, use the hand clutch. the only time to step on the foot clutch, is out in the open, when changing gears. If you use the hand clutch, to stop, then step on the foot clutch, you then have to wait for the BH to spool down, before shifting. If you just step on the foot clutch, you let the BH drive the tractor forward, and use up the stored energy, making for a quicker shift...
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Posted By: Burgie
Date Posted: 25 Sep 2016 at 5:50am
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With the ORC you don`t have to wait for the implement to spool down before shifting gears. ------------- "Burgie" |
Posted By: kev/ont
Date Posted: 25 Sep 2016 at 6:48am
It'll never hurt the tractor 1 bit. It it down right dangerous for the operator of the tractor in certain situations. The brakes will not stop the tractor and the inertia of a rotory mower. So on hill sides or tight corners you would run over or into obstacles before you ever knew what happened. However with a wd/wd45 use the hand clutch, no issue. |
Gary Burnett wrote:Posted By: LionelinKY
Date Posted: 25 Sep 2016 at 6:58am
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My main concern is being able to safely stop the pto when I want to such as when the job is done or when I may feel the need to (emergency) without breaking any shafts or shelling any gears in my WD45. So, it sounds to me like the consensus is to disengage the hand clutch first and then I would be able to use the foot clutch to stop the pto and disengage the pto drive safely without any fear of damaging something?? I have to admit, the ORC does sound more and more like extra insurance against OH $h!+ moments that we all know can happen when we are out there trying to get it done. Thanks guys. Learned something new today on top of why Dad insisted that us boys use the newer tractors when we started doing pto work in the fields. He used the WD45 on occasion but we only got to use the Oliver 1750 or 770s and sometimes even the 190XT. The only pto job we ever did with the WD45 was its main summer job of running the manure spreader after the daily barn cleaning. Usually never unhooked from the spreader except rare occasions when Dad needed it to run the haybine. ------------- "My name is Lionel and I'm an Allisoholic" |
Posted By: Gary Burnett
Date Posted: 25 Sep 2016 at 6:59am
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I've stopped my 10ft Sidewinder cutter with the brakes on my D19 when I pushed in the foot clutch.Actually its an advantage because then the cutter can be stopped quickly if it hits something or better before it hits something.I think some posters are working off theory on this one not actually experience.Or maybe they had an 8N Ford(LOL) |
Posted By: AaronSEIA
Date Posted: 25 Sep 2016 at 7:26am
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You can also quickly drop the engine rpm and slide the pto out of gear. The blades will freewheel till they stop. Don't forget, if a WD/WD45 has a weak spot it is the PTO gearbox. Panic stops using the brakes to nearly instantly shut down a very high inertia mower can (only can, not will) grenade the gearbox. Simple fix is to buy an Allis spin mower. They came with an orc in the driveline. Oh, and a slip clutch is NOT the same as an over running clutch. They are spring loaded devices designed to hold power under normal loads but will "slip" if a quick shock (like a stump or scalping the ground) occurs. AaronSEIA |
Posted By: littlemarv
Date Posted: 25 Sep 2016 at 7:43am
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This is a great topic, I was going to ask a similar question, as I bush hog in tight spots quite a bit. I would actually like to install a slip clutch and an overrunning clutch on my bush hog. I'm not sure if a guy has to modify the driveshaft to use both, or lengthen the drawbar? Because won't you be adding several inches to the driveline by using both? ------------- The mechanic always wins. B91131, WC23065, WD89101, CA29479, B1, Early B10, HB212, 416H |
Posted By: Orange Blood
Date Posted: 25 Sep 2016 at 7:53am
All things being equal brakes on a D19 are far better than those on a WD, WD45 or even the D17. I have been in a situation, so I am not posting theory. Yes you can stop a 5' rotary mower with WD brakes, even in moderate shape, but it still takes a foot or two, if you are standing on them. I imagine the same is true of the 10' on the D19. Bottom line that foot or two of ground travel in some cases can mean the difference between life or limb, on Nothing!!!!! Now factor in most WDs have poor or weak brakes for whatever reason, and now the 6' brush cutter is pushing you 5-10' when you really want to stop now.......... BTW...The Allis pull type mowers I have seen all have overrunning and slip clutches built in. They sit right in front of the gear box.
------------- Still in use: HD7 WC C CA WD 2-WD45 WD45LP WD45D D14 3-D17 D17LP 2-D19D D19LP 190XTD 190XTLP 720 D21 220 7020 7030 7040 7045 3-7060 Projects: 3-U UC 2-G 2-B 2-C CA 7-WC RC WDLP WF D14 D21 210 7045 N7 |
Posted By: DSeries4
Date Posted: 25 Sep 2016 at 8:08am
A slip clutch is usually built into the bush hog (but I do not know of many that have them) - it is not something that can be put on it. The over-running clutch on the other hand simply goes on the tractor's PTO and then the bush hog's PTO attaches to it. No need to extend the drawbar or shorten the PTO shaft for it to go on either. To all the nay sayers, I have to say that the over -running clutch has been one of the best investments I have ever made for using the rotary mower. ------------- '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: Gary Burnett
Date Posted: 25 Sep 2016 at 8:43am
If you need to stop the tractor immediately then thats what the had clutch is for. |
Posted By: CTuckerNWIL
Date Posted: 25 Sep 2016 at 8:45am
A slip clutch CAN be added to just about any PTO equipment. http://www.ebay.com/itm/Add-on-Rotary-Cutter-Slip-Clutch-Easily-Add-a-Slip-Clutch-to-Your-Shear-Bolt-PTO-/371504621928" rel="nofollow - http://www.ebay.com/itm/Add-on-Rotary-Cutter-Slip-Clutch-Easily-Add-a-Slip-Clutch-to-Your-Shear-Bolt-PTO-/371504621928 You can buy them off the internet. I also KNOW of situations where adding an ORC has caused real problems if the PTO shaft isn't altered. ANSI drawbar length is critical here. You CAN very easily bottom out the sliding PTO shaft when going thru a dip. The tractor facing uphill and a pull type mower still going downhill can ruin your day if you just added an ORC and didn't check things out first.  Now,if you add the ORC and lengthen the drawbar to 14 inches from the end of the ORC to the center of the pull hole, you should be OK. ------------- http://www.ae-ta.com" rel="nofollow - http://www.ae-ta.com Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF |
Posted By: Orange Blood
Date Posted: 25 Sep 2016 at 9:01am
I disagree respectfully......Almost ALL tractors out there have a foot engine clutch, very few have a hand clutch, even among Allis tractors. Instinct kicks in during emergencies, and the foot clutch is what you "grab" for, not the hand clutch unless that is all you run. So using the hand clutch is not "natural instinct" to those who don't use the WD much anymore.
------------- Still in use: HD7 WC C CA WD 2-WD45 WD45LP WD45D D14 3-D17 D17LP 2-D19D D19LP 190XTD 190XTLP 720 D21 220 7020 7030 7040 7045 3-7060 Projects: 3-U UC 2-G 2-B 2-C CA 7-WC RC WDLP WF D14 D21 210 7045 N7 |
Posted By: Gary Burnett
Date Posted: 25 Sep 2016 at 9:11am
It is for me I reach for the 'hand clutch' sometimes on my Olivers(LOL),I have multiple brands of tractors I use so I have to keep in my mind what I'm driving. |
Posted By: ocharry
Date Posted: 25 Sep 2016 at 11:02am
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hi guys i just got a new to me ac 170 this spring,,,i went from a jd to this tractor and it was a learning curve but i'm getting there.... after i got this ac home i thought well with the extra ponies i can get a bigger mower,,,so i got a new 6' bush hog razor back....nice mower the difference between the two tractors is the jd had live power....foot clutch made no difference to pto drive,,,it had its own clutch set up after a little seat time and a push or two,,,,i thought all tractor had the live pto,,,,i got to doing some research and find out that the foot clutch does disengage the pto on the ac,,,,that was an ahh-haaa moment,,,, so i got a over run clutch and a slip clutch and put them on,,,,,now this mower came with a shear pin set up,,,and i used that plus the slip clutch for the drive line at the gear box on the mower,,,,and the over run clutch at the pto shaft on the tractor,,,,over kill,,,,maybe,,,maybe not,,,,but i feel better about it and it works just fine oh and i had to cut 12" off the drive shaft,,,,,i still have 4" of dead space when it is all the way at the top of the lift,,,,,,,MAKE SURE YOU CHECK THAT,,,,if it bottoms out you WILL break something sooner or later,,,,,maybe the first time my .02 ocharry
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Posted By: Gerald J.
Date Posted: 25 Sep 2016 at 11:29am
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If the PTO is driven off the transmission like the 8N, the bush hog spinning inertia will make you hit buildings, poles, trees, and fences when you try to get close to them. Sounds like the two clutches of the WD can solve that if the operator realizes the hand clutch is the only way to stop the forward or reverse motion of the tractor, but these days most of us are used to the foot clutch doing that work. Hitting those obstacles can do damage to the machinery or those obstacles costing way more to repair than the cost of an over running clutch. Gerald J. |
Posted By: Dan73
Date Posted: 25 Sep 2016 at 11:46am
| Yes always check the free play in any pto setup when you hook up the first time. I remember there was a broken pto shaft for one of the tractors here when I was a kid. The shaft broke on the first turn because no one checked it on something we just bought. It was the tractor side that broke too pretty expensive and a pain to replace. |
Posted By: TimNearFortWorth
Date Posted: 25 Sep 2016 at 12:37pm
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Said it before on here but it warrants repeating; a good number of folks are killed each year because of tractor "push" when using a brush cutter, mainly when they are pushed into a limb (head trauma). Doing fence lines myself currently before winter seeding and always 1st low range so I hopefully have a bit more response time if ever required. It only takes a second to get into very deep trouble with a brush cutter of any size . . . . |
Posted By: TREVMAN
Date Posted: 25 Sep 2016 at 12:42pm
| Install an orc. It helps prevent shock loads to tractor driveline and engine. You'll be glad you did. "Bush Hogging" is very hard on tractors...JMHO, Trev. |
Posted By: CrestonM
Date Posted: 25 Sep 2016 at 1:09pm
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I have an ORC on my 8N, and I really like it. Like was said earlier, you don't have to wait for the implement to wind down when shifting. Of course, I had to have an adapter of some sort because the 8N, as well as my B, have a 1 1/8" PTO shaft. So the ORC input is 1 1/8" and the output is 1 3/8". This way I can switch it easily between the 8N and the B, depending on which is doing PTO work. A little off topic...I've never seen any PTO implements that require 1 1/8" shaft. Surely they made some though? All I've seen is the drive sheave for my sickle mower, which fits the 1 1/8" shaft.
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Posted By: Gary Burnett
Date Posted: 25 Sep 2016 at 1:43pm
So you got an 8N huh? Maybe you can settle a question for me fellow with an 8N swore it could out pull my 3 legged Mule so I was gonna to bet him but he backed down when $$$ became involved.What'd you think? |
Posted By: CrestonM
Date Posted: 25 Sep 2016 at 2:20pm
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8N at 1/2 throttle could out-pull a 3 legged mule! Lol How often do you see one mule pulling a 2 bottom plow?
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Posted By: Dan73
Date Posted: 25 Sep 2016 at 2:21pm
| About as often as I see a 8n pulling one... but then I never seen anyone actually use a 8n |
Posted By: TMiller/NC
Date Posted: 25 Sep 2016 at 2:29pm
| ORC is especially handy when using a Bush hog or mower backing up to building, fence, creek bank, or other drop off. Push in foot clutch and stand on foot brake. Brakes don't seem to work as well in reverse. |
Posted By: Hubert (Ga)engine7
Date Posted: 25 Sep 2016 at 2:57pm
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Ran Dad's WD for years with either a six foot heavy duty bush hog or a baler just using the hand clutch with no problems. That being said, an ORC is not a bad idea and gives some extra insurance, especially for someone who is not used to using the hand clutch. ------------- Just an old country boy saved by the grace of God. |
Posted By: Gerald J.
Date Posted: 25 Sep 2016 at 3:05pm
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I had an 8N for a few years. It had a trip bucket loader and came with a 12' single rank disk and a 2 bottom plow. I added a three point blade because the loader and bucket were lousy for moving snow. As I recall, the trip bucket full of snow wasn't front heavy enough to tip when the latch was released. It didn't have enough weight to push the blade in a foot deep snow. The only way I could move snow was to drive forward away from the snow, and the hit the snow backing fast. I broke the frame of the blade doing that. I did borrow a bush hog mower once without a ORC and I did hit stuff because the flywheel of the mower blade was connected to the intermediate shaft of the transmission and drove the tractor even if the engine was stopped. That was a handy way to design the PTO, and Ford considered it a benefit to have the PTO speed a fixed ratio from the ground speed for things like a PTO driven rake. That's very likely the source of the 540 RPM PTO since the N family were the first tractors with the shaft PTO. I plowed a garden or two with the Dearborn 2 bottom plow. It didn't please the gardener, the depth of plowing varied from high to low and sometimes the plow would go deeper, then pull harder and the three point would lift (safety feature) the tractor rear axle and the tires did more tillage than the plow. It was just too light for the power and the three point safety features like that messed up doing a good job of even plowing. I put new rear tires on it, a new wiring harness, and rebuilt the starter. I was glad to see it go and I actually got a few bucks for my labor over my purchase price and the costs of repairs. I moved snow better with a JD 112 and a JD 400 snow thrower, though I spent more time in wet snows unplugging the thrower (single stage) than throwing snow sometimes. I consider an 8N a toy best suited for a yard ornament, not good for real work. I'd probably have moved more snow and plowed gardens better with the lighter and lower powered Allis G. I know post war farmers transitioning from horses got along with the 8N, but I didn't. The MF-135 that I bought when I bought the farm is about the same size as the 8N but has twice the power and twice the weight and can do real work like plowing with 2x 16s all day. Gerald J. |
Posted By: wfmurray
Date Posted: 25 Sep 2016 at 4:56pm
| Dad pulled a combine for years with a D/14 no trobule with pto. I got it and put a bush hog on it with no clutches.Pto would not disengage . It had twisted shaft at splines . To many stumps .Put clucth on and solved problem .With mower stopped rev engine and drop foot clutch and mower clutch should slip some .Check mine first of every season.. |
Posted By: Dan73
Date Posted: 25 Sep 2016 at 5:06pm
| With a wd or d serries if you pull the hand clutch and then step on the break peddle it will stop the tractor while the brush hog spins. I did that last fall brush hogging with my d15. The hand clutch will disengage the rearend from everything so all you need is the break to actually stop the momentum of the tractor. With a d serries the fluid hand clutch will drive a little when it is out of range but the break will easily over come that. If it was mine I would put the brush hog on it try it in a nice open place and see how it feels if you don't like the feel those overrun clutches are pretty cheap. |
Posted By: CrestonM
Date Posted: 25 Sep 2016 at 9:02pm
8Ns are very lousy loader tractors. I agree on that. And reverse is way too fast for pushing snow with an angle blade backwards. But plowing...sounds like your draft control wasn't set right. When it's set right, it should just bump the plow out enough to keep the tractor wheels from slipping. Similar to the traction booster on a Allis. Except on an Allis you can adjust the sensitivity. And about the 540 RPM PTO, I'm a little confused by what you said about the N-series were the first tractors with the shaft PTO. The 9N was the first in 1939, but Allis WCs in 1935 had them for running All-Crops. Farmall Regulars had them too, and they started in 1924.
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Posted By: VAfarmboy
Date Posted: 25 Sep 2016 at 9:56pm
A lot of guys around here used to farm with 8ns back in the day. They were a good sized tractor and way ahead of their time when they first came out. My grandad had an 8N for 50 years. It was the "big tractor" on his 80 acre farm until the day it left. The only thing he didn't use it for was cultivating and side dressing which was done with a Case VAC and a Farmall Cub. I did some plowing for him with it back when I was a teen and at that point the tractor was over 30 years old, had nearly 3000 hours on the clock and was using oil but it would still move right along with his old two bottom Dearborn plow. When it finally got traded on a new Deere 5210 in 2002 because it was completely worn out, the Deere dealer gave him more than twice what he paid for it new in 1952. The three point having a mind of its own and lifting up by itself is not a "safety feature". That is a common problem with 8ns when they get worn out which the vast majority of them were over 40 years ago. The one my grandad had got like that, you would be bush hogging with it and suddenly the three point would lift the bush hog up all by itself. He looked into getting it fixed but you apparently have to disassemble the whole ass end of the tractor to do the job which is probably why most of them out there haven't been fixed. Grandad wasn't much of a mechanic and didn't want to dump the kind of $$$ the New Holland dealer wanted to fix it into a 50 year old tractor that also needed an engine overhaul so he sent her down the road. They were popular back in the day and there are still a lot of them around. Ford 8ns that have been "restored" (which in many cases simply means a fresh coat of paint) are a hot item with the folks who move out into the country and buy a five acre lot. The Deere dealer said that some guy saw grandad's 8n Ford going down the Interstate on the lowboy and followed them to the dealership and paid them the asking price of $3,500 for it on the spot, before they even unloaded it.  |
Posted By: m16ty
Date Posted: 26 Sep 2016 at 12:13am
| I read somewhere that IH was the first to come out with the PTO on the 8-16 in 1918. Due do the gearing, it just so happened that the PTO speed was 540rpm so I guess it stuck. It wasn't like they planned the speed to be 540, that's just how it turned out. |