Pulling force?

[chipwitch 73]

Has anyone ever measured the dead pulling force one of these STOCK tractors can do? 

 

A sport fishing scale like the ones used to weigh tuna, marlin, shark and the like, a strong ole tree and a rope would do the trick.  I don't know much about tractor pulls other than the concept.  Not the same thing, but maybe some of you have tried what I'm talking about?  I realize there are many other factors like type of tires, ballast, ground surface etc.

 

Just curious.

[baerpath 517]

With our puller to lightly load the engine we pull a boiler plate (guessing around 400lb) and put another 1000lb on it.  The sled we pull is a 7000lb transfer sled. 

[chipwitch 73]

That doesn't tell me much.  That's why I mentioned the tree, scale and rope.  I'm interested in dead pull.  Static pull.  Sled pulling is a dynamic event where sled/earth friction, inertia, velocity and probably other factors are at play.  From an engineering standpoint, I'd like to know the maximum force that can be reasonably expected to be exerted on the hitch, for example.  Or up how steep an incline could the tractor pull a ton of bricks in a cart?  Does anyone know the torque delivered to the wheels?  That would be a start but even that is purely theoretical as it depends heavily on traction.  I'm surprised no ones tested the static pulling power.

[bmsgaffer 2,043]

I think the reason no one has done it is because:

 

a- it will vary WILDLY per the conditions, (surface, tires, weight added, horsepower, mods, age, etc., etc.) so there can be no accurate, or repeatable results. Joe Bob may be doing it on 10 year old asphalt with turf tires And Billy Jean is doing it on roughed concrete with slicks...

 

b- with the low gearing ratio there is a high probability of breaking something before you stall the engine assuming you can get all the traction you need.

 

Edited October 26, 2014 by bmsgaffer

[chipwitch 73]

 

b- with the low gearing ratio there is a high probability of breaking something before you stall the engine assuming you can get all the traction you need.

 

 

Really?  So no one has ever stalled an engine on a WH from too much load?  Something breaks first?  So, what's the first part that breaks?   The weakest link will tell me what I need to know.

 

My guess is the drive belt slips first.

Edited October 26, 2014 by chipwitch

[bmsgaffer 2,043]

well you were looking for max torque right? that would be first gear low... I think I would put money on no one stalling a good running engine at operating speed in first low...

 

I have never found a tire that could bite anything well enough to even get close to that...

 

I'm sure plenty have stalled them in a higher gear, with a load, or not at operating speed...

 

As far as what would break first? I'm not sure. If the belt, pulleys, and transmission are all in good condition I think I would say the transmission mounting plate followed closely by an axle... But thats just my educated guess.

Edited October 26, 2014 by bmsgaffer

[slammer302 2,154]

I just loose traction before something ever breaks

[joel_400 59]

In low gear Im sure you will just run out of traction before you hurt anything. The only time I even use the low gears is to till. With a hydro Im not sure how you would turn out. I never pull anything with them anymore. I have pulled an early 70s chrysler new yorker up a small hill years ago with my hydro tho. What a tank that was! Worked good till my buddy hit the brakes and I instantly left 2 8 inch ruts in his yard! Haha

Joel

[octfst 378]

I've got a 753 tractor I do a little pulling with. I pulled dead sled & always ran out of traction. pulled 1100 lb in the dead sled. But I've stalled it pulling transfer sleds. not sure what the weight would be at that time. The class was 14hp and under.

[Tankman 3,515]

In 40+ years, have only lost traction. 

 

I'm thinking, "Why would anyone deliberately risk hurting their Horsey?"

 

Been to many tractor pulls. Most are those with the bucks to repair, some have sponsors.

We groom and baby our Stallions.

 

I might even "force" the grandsons to rub a little Turtle Wax on 'em today. OK boys, mount up, ride 'em cowboys!       

Edited October 26, 2014 by Tankman

[dtallon 320]

I don't have as much experience with the 'horses as some, but I'm also in the "it will lose traction before it stalls" camp.  

 

I have actually done the test you are talking about as a test engineer on Cat dozers.  It's harder to do you you might think.  To keep from spinning the tracks they have track shoes welded face up on a bed plate so the grousers on the tractor lock with the ones on the bed plate. Then it pulls against a "immovable" object with a calibrated load link in between to measure the force.  Even with this elaborate setup, test results vary quite a bit.  With just a little slack in the cables the tractor can get a small amount of momentum and pull and hold a higher force than it can if the operator perfectly eases into it. 

 

Of course, that was all done on tractors with a torque converter in them, and the converter acts as the "fuse", stalling out (zero output RPM) when max pull is reached.  We don't have converters on our little garden tractors, so traction is the "fuse".  If you locked the wheels in, I'd bet you would either slip the belt, or break something.  It's common to focus on drawbar force specs on any kind of tractor, but drawbar horsepower (force combined with speed) is a much more useful measure of tractor performance. 

 

Dave

[chipwitch 73]

Thanks for the replies, guys.  When I made the comment about the belt slipping first, I was imagining the rear wheels in a locked state, but only for the purpose of imagining what would happen.  My mind went to the belt.  In the real world, I'd imagine traction will ALWAYS be the issue (yes, in low gear). 

 

Tankman, you actually made me chuckle.  You ask, "Why would anyone deliberately risk hurting their Horsey?"  It reminded me of the video I watched of a member using a lawn ranger, loaded with what looked like about 400 lbs of weight, his weight and a homemade FEL wrestling with a monster sumthineruther.  the weight of the sumthineruther was great enough to give the camera a good jostle.  It was mounted to what looked like the pickup trailer towing the trailer on which the sumthineruther was being moved to.  I'm sorry if I've given the impression I want to "hurt my horsey."  I just want to know where its limits are!!!  Does anyone know?

 

bmsgaffer, yeah I've seen the pictures of transmission mounting plates.  Seems like a reasonable assumption, but I would guess the contrary.  My guess is your guess is based on your experience with pulling.  Dynamic pulling is much different.  You have weight on the nose, no doubt, engines are hopped up and you're snatching the load, yes?  I'm not a puller so I'm making a bunch of assumptions.  The sudden acceleration with all that weight on the nose is undoubtedly going to put stress on the TM.  The way I see this is if you are towing the load hitched to the right location (somewhere close to the axle), the only stress placed on the TM has to be a result of the moment arm of the nose of the tractor to the rear wheels since the transmission is bearing all of the towing load.  Imagine the tractor in a wheelie orientation at a moment in time.  The weight of the tractor's front end would be supported entirely by the TM.  If the load is hitched to the right location, there is no way the load itself can impact the transmission mount (rather, think of it as the front end mount) beyond the forces caused by the rotational acceleration of the front end around the rear axle.  I think the problem with the weak TM is most likely a result of fatigue coupled with any load placed anywhere ahead of the rear wheels including the tractor front end itself.  That being said, I'm only speaking in generalities as the placement of the tow hitch will affect the strain on the TM.  If you could place the hitch low enough (theoretical point below the earth surface), you could indeed place enough force on the TM to break it. 

 

I say all of this with a healthy dose of humility.  I have nearly zero experience with tractors and recognize my engineering skills aren't infallible.  So, if my analysis is flawed, I welcome correction. 

[chipwitch 73]

Dave, the test you're talking about is about testing for failure.  That's close to what I'm looking for with the exception that I'm NOT talking about locking down the wheels.  Traction is a huge and widely variable factor.  But, it's also one that is "accepted" when challenging others to a pull.  No?  I doubt there are many winners at a tractor pull that are running turf tires on the rear (unless there's a class for that or you're running on pavement perhaps).  Obviously, one is going to use the tires that they "think" will provide them with the most traction and take home first prize.  How much weight is placed on the tractor and where is also a huge factor.  The amount of weight towed is a direct function of those factors as well as a little skill on the part of the operator.  My point is this, having those factors certainly doesn't stop tractor enthusiasts going out to compete for bragging rights... Well, I pulled x with MY tractor!

 

I'm not looking for anything different here except that we're trying to pull against an immovable object.  The conditions and configuration of the tractor would also be relevant.  In fact, without the conditions and configuration, the number registered on the "scale" would be meaningless.

 

The reason I'm asking about this is because of the 3PH I'm designing.  It's a reasonable question to ask, "What is the maximum reasonable force that a C-125 is capable of exerting on its drawbar under normal operating conditions."  That information would be very useful in determining the minimum requirement for materials.  Over-designing a hitch, or designing it incorrectly can both result in a damaged tractor.  That's what I'm trying to avoid.

[KyBlue 652]

Except your 3PH isn't the drawbar. You're building onto the axle, and you are going to be more limited by what you can lift, than what you can pull.  As you add weight to keep the front of your tractor down as you lift up on that 3ph ... you're going to add stress to the TM ... Cracks will develop if you do it enough.

 

This isn't a fullsize tractor ... you're not going to be lifting a brushhog with it...  While I applaud you're desire to prevent damage, and research your 3ph ... IMHO you're over thinking - and trying to over research the thing.  Go to your local larger tractor dealer - and look at the setups on the big ones ... take pics and measurements. This is going to be your most effective resource.  Pay attention to the material they used.  You can scale it back  because you're not going to be lifting the same loads... 

 

You'll get there, and I'm sure we're all looking forward to seeing what you come up with.

[RMCIII 838]

Dave, the test you're talking about is about testing for failure.  That's close to what I'm looking for with the exception that I'm NOT talking about locking down the wheels.  Traction is a huge and widely variable factor.  But, it's also one that is "accepted" when challenging others to a pull.  No?  I doubt there are many winners at a tractor pull that are running turf tires on the rear (unless there's a class for that or you're running on pavement perhaps).  Obviously, one is going to use the tires that they "think" will provide them with the most traction and take home first prize.  How much weight is placed on the tractor and where is also a huge factor.  The amount of weight towed is a direct function of those factors as well as a little skill on the part of the operator.  My point is this, having those factors certainly doesn't stop tractor enthusiasts going out to compete for bragging rights... Well, I pulled x with MY tractor!

 

I'm not looking for anything different here except that we're trying to pull against an immovable object.  The conditions and configuration of the tractor would also be relevant.  In fact, without the conditions and configuration, the number registered on the "scale" would be meaningless.

 

The reason I'm asking about this is because of the 3PH I'm designing.  It's a reasonable question to ask, "What is the maximum reasonable force that a C-125 is capable of exerting on its drawbar under normal operating conditions."  That information would be very useful in determining the minimum requirement for materials.  Over-designing a hitch, or designing it incorrectly can both result in a damaged tractor.  That's what I'm trying to avoid.

 

You are looking for DBHP, and not necessarily torque, although we all know torque begins to move the load, HP takes over. The device you are talking about would have some initial "give" to it before the tractor would actual start to strain under the load. I am sure you knew this already, due to the engineer degree. < Not trying to be funny or sarcastic. Not sure if this helps your investigation or not. I hooked my 518 up to a Pontiac Sunfire that had its rear brakes locked up. My neighbor needed to get it to his garage. He kind of gave me a look when I said I would just pull it with my tractor. We hooked the car up by the front end, and ran the chain under the car, and I pulled the car backwards. I know the area where we hooked allowed for some pressure on the front end to provide some "lift" for the rear of the car. It pulled the car just fine. WOT and at a crawl, the tires did break loose a little, going up his driveway, but we managed to get it into his drive where he could work on it. I'd say that is a big load for a little 18hp garden tractor to pull. BTW, you are still combining a dynamic load property in your testing of finding out what your DBHP would be... Static loads are designed for structural support, buildings, bridges, ect.. You are seeking to find the maximum "strength" your tractor can achieve. This device starts out with little to no resistance, and builds as it is pulled, like the large fish scale. So a static load would not do you any good. The only thing static would be the tree that it is attached to. As others have stated above, the ground conditions come into play. Also gravity, has nothing to do with, the force you are looking to find for your tractor. We all know that gravity is the effect on a static load. So to be correct, it is a dynamic load test that would be done to figure out DBHP. It is possible to "calculate what your DBHP" could potentially be. I would guess though that you are looking for an exact calculation. Just my 2 cents.  

[chipwitch 73]

RMCIII, first off... I never claimed to have an engineering degree.  I went to school for it.  I got bored with it before finishing.

 

Second, I'm simply asking a question, "What is the maximum reasonable force that a C-125 is capable of exerting on its drawbar under normal operating conditions."  I thought that if I asked it, someone here just might have an answer for it.

 

Third, statics is the study of a system in a state of equilibrium.  By definition, a tractor putting with all its "strength," as you put it, against an immovable object is static because all the forces acting on the system net zero.  A change if the force exerted by the tractor is exactly equal to the force in the opposite direction exerted by the tree.  If the tree moved, the system would not be in equilibrium and the system is no longer static.  Conversely, if the force exerted by the tree was greater than that of the tractor, well then the tractor would be pulled backwards and that would be a quite magical feat.

 

Fourth, gravity is a force, nothing more.  As a force it is sometime the key component in evaluating a static system.  In this particular case, it only plays a role insomuch as it affects traction.  And, I don't remember introducing gravity into this equation.

 

And lastly, Finite Element Analysis is the study of the forces acting on a very tiny portion of a part.  It is always done when all the forces acting on the system are a net zero.  Dynamics can reveal additional forces that are acting on a system in motion such as centripetal force that would not have been determinable in a static analysis.  However, to study the point at which a part will fail ALWAYS (as far as I'm aware) concludes with a static analysis.  The reason dynamics is important is to find those forces and include them in a static FBD, but they must ALWAYS be offset by some countering force first.

 

Now, if only you had had a tension meter on the cable you used to pull that Sunbird up a slope... I would have been very interested in the results!  While it may not tell us what the limit is of your WH, it would have told us the force it was able to transfer to the hitch.  I find that pretty cool.   

[chipwitch 73]

Except your 3PH isn't the drawbar. You're building onto the axle, and you are going to be more limited by what you can lift, than what you can pull.  As you add weight to keep the front of your tractor down as you lift up on that 3ph ... you're going to add stress to the TM ... Cracks will develop if you do it enough.

 

This isn't a fullsize tractor ... you're not going to be lifting a brushhog with it...  While I applaud you're desire to prevent damage, and research your 3ph ... IMHO you're over thinking - and trying to over research the thing.  Go to your local larger tractor dealer - and look at the setups on the big ones ... take pics and measurements. This is going to be your most effective resource.  Pay attention to the material they used.  You can scale it back  because you're not going to be lifting the same loads... 

 

You'll get there, and I'm sure we're all looking forward to seeing what you come up with.

 

 

That's why I said this:

 

 

 

Thanks for the replies, guys.  When I made the comment about the belt slipping first, I was imagining the rear wheels in a locked state, but only for the purpose of imagining what would happen.  My mind went to the belt.  In the real world, I'd imagine traction will ALWAYS be the issue (yes, in low gear). 

 

Tankman, you actually made me chuckle.  You ask, "Why would anyone deliberately risk hurting their Horsey?"  It reminded me of the video I watched of a member using a lawn ranger, loaded with what looked like about 400 lbs of weight, his weight and a homemade FEL wrestling with a monster sumthineruther.  the weight of the sumthineruther was great enough to give the camera a good jostle.  It was mounted to what looked like the pickup trailer towing the trailer on which the sumthineruther was being moved to.  I'm sorry if I've given the impression I want to "hurt my horsey."  I just want to know where its limits are!!!  Does anyone know?

 

bmsgaffer, yeah I've seen the pictures of transmission mounting plates.  Seems like a reasonable assumption, but I would guess the contrary.  My guess is your guess is based on your experience with pulling.  Dynamic pulling is much different.  You have weight on the nose, no doubt, engines are hopped up and you're snatching the load, yes?  I'm not a puller so I'm making a bunch of assumptions.  The sudden acceleration with all that weight on the nose is undoubtedly going to put stress on the TM.  The way I see this is if you are towing the load hitched to the right location (somewhere close to the axle), the only stress placed on the TM has to be a result of the moment arm of the nose of the tractor to the rear wheels since the transmission is bearing all of the towing load.  Imagine the tractor in a wheelie orientation at a moment in time.  The weight of the tractor's front end would be supported entirely by the TM.  If the load is hitched to the right location, there is no way the load itself can impact the transmission mount (rather, think of it as the front end mount) beyond the forces caused by the rotational acceleration of the front end around the rear axle.  I think the problem with the weak TM is most likely a result of fatigue coupled with any load placed anywhere ahead of the rear wheels including the tractor front end itself.  That being said, I'm only speaking in generalities as the placement of the tow hitch will affect the strain on the TM.  If you could place the hitch low enough (theoretical point below the earth surface), you could indeed place enough force on the TM to break it. 

 

I say all of this with a healthy dose of humility.  I have nearly zero experience with tractors and recognize my engineering skills aren't infallible.  So, if my analysis is flawed, I welcome correction. 

 

 

Respectfully, I'm not over-thinking this.  This is how things are produced commercially.  From the most complex aircraft to the humble paperclip.  Leaving it to chance or WAG (wild-axx-guess) engineering are fine for those who wish to engage in them.  That's not me.  I like to know the numbers.  I realize it ain't for everyone...

 

This thread has gotten way off topic.  While I enjoy engineering, calculus and physics, and could talk for hours on the subject, with all due respect, all I really want to know is what I asked in the OP, "Has anyone ever measured the dead pulling force one of these STOCK tractors can do?"  If not, that's cool.  Just remember, these tractors would have never become what they are today had someone (many people) not done precisely what I'm trying to do for my hitch.

 

Maybe we don't share a common enthusiasm for the engineering behind our tractors, but we all DO share our enthusiasm for the end result.

 

cheers 

[bmsgaffer 2,043]

The conversation has evolved because everyone is trying to tell you that information is irrelevant.

 

Heres what you want to know:

 

At the end of the three point hitch max lift capacity no more than 300lb, dead pulling 600lbs. (your tractor weights a little more than 600lbs, this is what I am basing all of the numbers on). And you will require weights in front to keep tractor down.

 

Drawbar (not 3 point) the SAFETY numbers are the same as you are not supposed to tow more than 80% of vehicle weight, however many people here (myself included) have been able to tow many times more than that. I would say 1000lbs would be max. (Before people yell at me: thats pulling force, not weight of object towed, which can be many times more depending on friction forces of motion)

 

For building materials figure a factor of safety of at least 5 times.

Edited October 26, 2014 by bmsgaffer

[KyBlue 652]

Exactly!

 

You are right about research and engineering, except you are trying to redo what the big tractors have already spent many many many thousands of dollars, and many years deisnging and refining. You can use their effort to build your piece.  That's called working smarter, not harder, and you're not producing something commercially. You're making a one off piece for your GT that has already been done by several members on the board already - with much success.

 

I respect what you're trying to do, and you're right it isn't me.  But if you want research, and hard engineering data, you're probably going to have to do it yourself, and you'll need much more than a Fish Scale to measure pull of your GT.

[RMCIII 838]

RMCIII, first off... I never claimed to have an engineering degree.  I went to school for it.  I got bored with it before finishing.

 

Second, I'm simply asking a question, "What is the maximum reasonable force that a C-125 is capable of exerting on its drawbar under normal operating conditions."  I thought that if I asked it, someone here just might have an answer for it.

 

Third, statics is the study of a system in a state of equilibrium.  By definition, a tractor putting with all its "strength," as you put it, against an immovable object is static because all the forces acting on the system net zero.  A change if the force exerted by the tractor is exactly equal to the force in the opposite direction exerted by the tree.  If the tree moved, the system would not be in equilibrium and the system is no longer static.  Conversely, if the force exerted by the tree was greater than that of the tractor, well then the tractor would be pulled backwards and that would be a quite magical feat.

 

Fourth, gravity is a force, nothing more.  As a force it is sometime the key component in evaluating a static system.  In this particular case, it only plays a role insomuch as it affects traction.  And, I don't remember introducing gravity into this equation.

 

 

I guess I missed the "static-load, vs. Dynamic load principales" when I was in school. Although I do need to use the standards of a static load vs. a dynamic load on a daily basis becasue of my job. When I mentioned gravity, I thought everyone knew, when referring to static loads, it is the gravity, combined with a constant load, that needs to be tested. So for isntance. A rigging point that is rated at 2,000lbs, needs to have a tension applied of 2,000lbs, that does not move (dynamic) for a period of 10 minutes. If the meter stays constant for the 10 minutes, the point is said to be certified at 2,000lbs. Now, that is a static load, and not a dynamic load. The dynamic load increases as the element, or attached fixture to the point, provides more or less weight throuhout it's movement. Dynamic load. A static load uses gravity and a steady weight to achieve the "static laod" rating! You are, and I am sorry to be so anal, looking to use dynamic forces to attaine a metric value of your C-125 draw bar strength... It is very simple to achieve either with the DBHP formula or just go out and purcahse one of these:

 

http://www.smokstak.com/forum/showthread.php?t=98438

 

BTW let's keep it friendly and open for inputs. You are talking about something that I have 30 plus years of expierence on. Not school room knowledge, so my verbal comunication, may not be on target with written books, but I am pretty sure after 30 years of playing with this stuff I could at least have an open conversation with what I still work with today in my professional world.

 

 

 

Rob

[Forest Road 594]

Speaking from experience you'll run out of traction before you run out of power. Hydros and 8 speeds alike will pull far more than they are capable of stopping.

This one time when my brother in law and I were both drunk..... We hooked a 312-8 up to my Crew cab F-150 and pulled it quite some distance. Then in his infinite wisdom my bro OUT law put the truck in reverse. Bastard!!! It was good for some laughs.

[chipwitch 73]

Thank you gentlemen.  I appreciate the effort.

 

[ericj 1,576]

back in the day john deere put a 8 hp kohler in a 110 jd and called 10 hp drawbar hp thus the 110. but as we all know you still only have 8 hp pto power. i would guess through gearing they got that little 8 to pull 10 dbhp. i don't think it work so well for them in the long run

 

 

 

eric j 

[gwest_ca-(File Mod) 10,491]

I'm working on pulling stumps and trees with 4 blocks and a cable so the force exerted is 5 times what the tractor will pull. That wasn't quite enough so added 2 more blocks after the 1st set making 15 times what the tractor will pull which is scary. Have decided to find out what I'm working with. Have a hydraulic cylinder that will hook to the tractor and the cable will hook to the cylinder rod. Will almost fill the cylinder rod end with oil and add a pressure gauge to that end. The other end will get a breather filter. That way I can use the pressure created to calculate what I dealing with.

 

Can pull a hard maple tree by tying on a foot up for every inch of diameter at the stump. 10in being the largest so far.

 

Garry

[Geno 1,928]

I would love to see that setup!