how many horses

[jac]

Tim I use the machine to create slots about 6″ long and up to a max of 7″ deep to let surface water away , let air in as well as nutrients. The slots then crack and gradualy spread out as the ground dries out. We have very heavy land and if you leave it to late it can get way to hard, though I could weight it up but then I suspect it would be to heavy for horse work. I also have a land driven seed box mounted on top so I can sprinkle grass seed at the same time.The tractor made versions have 72 blades but then you have to weight them up to get it to penetrate.
John

[Tim Harrigan]

John: Here is a pdf of a presentation about some work I have been doing integrating manure and cover crops. This in not likely to be a draft animal application but you may find it interesting.

[jac]

Hey Tim that rotor is a larger version of the one I made. You look to have 4 blades per bank where I have only three but its the same idea. I take it you can alter the angle of the rotors to increase the slot opening?. If I was asked to describe the two machines i’d say yours was more of an incorporation tool as opposed to mine being just an areator. I notice you mentioned pest control. Were you refering to slugs?. Seed loaded slurry hasnt’ been used over here,but then cover cropping isnt a big thing either, the clover looked good in the foto. Got me thinking about the effluent that seeps away from my manure heap.. should really be burying a tank and saving that stuff. Perhaps a small tanker of say 150 gallons and a dribble bar would work following the areator.Think I saw a foto of one being used at a progress day. Very small scale but a thought for market gardeners.. Soil errosion wasnt’ an issue I’d thought of but when I think about it, after heavy rain there are tiny rivers running down the field, the 1st steps of errosion I suspect, so if I can get rid of the surface water, then the soil errosion problem can be helped. I noticed before I started using my slitter that the compacted area along the fence line where the horses congregate got really slippery after a shower of rain, where as after the slitter had been over it the land didnt take on that shiney appearance. Thank you for all that really great feed back Tim: cheers
John

[Tim Harrigan]

Not slugs, 🙁 oil seed radish suppresses sugar beet cyst nematodes and oriental mustard suppresses some soil borne fungal diseases like pythium and rhizoc. And the combination of manure and cover crops is more effective than either manure or a cover crop alone. 😀

[jac]

Does anyone know the real “horsepower” of draft horses. Ive heard figures of around 8hp/per average drafter ?? but if thats true then my team only has about 16 hp!! Now mabey Im looking at this to simplisticaly but your average lawn tractor is 16hp.. and I cant see that moving a 4 ton load on a wagon at 5mph or even pulling my grass harrows !!??!!
John

[Tim Harrigan]

I can help explain this but I will not have much time or energy for a few days. 🙁

[Traveling Woodsman]

@jac 15004 wrote:

Does anyone know the real “horsepower” of draft horses. Ive heard figures of around 8hp/per average drafter ?? but if thats true then my team only has about 16 hp!! Now mabey Im looking at this to simplisticaly but your average lawn tractor is 16hp.. and I cant see that moving a 4 ton load on a wagon at 5mph or even pulling my grass harrows !!??!!
John

Ok, so here are some of my thoughts. I’m sure there is science and math involved here that you can learn somewhere, this is just some of my musings on the subject, and is by no means comprehensive. I would be interested in what anyone else has to say.

The energy required to move a given object, be it dragging or rolling, is measured in units of force, such as ft-lbs. 1 horsepower is equal to 550 ft. lbs per second, and is a unit of work, which is a force exerted over a distance. So horsepower measures force over time, and by extension distance. Now engines, let’s take for example a 60 HP tractor, are rated usually by brake horsepower. There are other ways of measuring horsepower, but this one is fairly common. Brake horsepower is the measure of the output of an engine after internal losses such as friction, but before external losses are factored in, such as alternator, water pump, power steering pump, muffled exhaust, gearboxes, differentials and other auxiliary components. (Somebody correct me if I’m wrong). All of these together can be significant subtractions to the actual usable HP, somewhere around 20-40%, depending on the situation. I have heard even higher numbers.

So let’s look at the 60 HP tractor. With a brake HP of 60, we might only have 36 HP usable after all deductions are accounted for. This 36 HP can be used on the PTO or on the drawbar, but the drawbar is what we’re interested in for the purposes of this discussion. The percentage of this 36 HP available on the drawbar is a function of the tractors ability to grip the ground and the amount of HP required to move the actual tractor. There are a number of variables that determine this, such as weight, whether the tractor is 2WD or 4WD, whether there is locking differential(s), tire type, surface type, moisture, surface condition and maybe some others I’m not thinking of. I am not currently aware of specific numbers here, and this is also something that can vary significantly. But I have heard numbers as low as maybe 15-20 HP actually available on the drawbar from a 60 HP tractor. Or one number I’ve heard specifies a 40 HP tractor actually having 7-8 HP on the drawbar.

Now let’s consider the output of a team of 1500 lb. draft horses. It is generally accepted that a team in good flesh and condition can exert 1 HP each continuously for a 6-8 hour day. So 2 HP per team. But, that same team could exert up to 25 HP together for a short period. This is the actual output, after the horses move themselves along. And I have actually heard numbers as high as 40 HP for a bigger team on short pulls. So a big team of horses may be able to out-pull a 2WD 60 HP tractor for short distances. In fact, my first team of horses which were 1500 lb. each wringing wet, could move a log in wet conditions that my neighbor’s 50 HP 2WD John Deere couldn’t move in the same condition (although it could move it in dry conditions). However, this was a short term effort for my horses. This is where it gets hard to compare horses to tractors, because a tractor doesn’t have this tremendous short term overload capacity, but what they can do they do indefinitely.

Both engine manufacturers and equipment manufacturers obviously want to cast their products on the best light possible, which is why numbers such as brake horsepower are used. So the horsepower unit has degenerated from a way to compare horses to machines (it’s original purpose), to a way to compare machines to machines, since there are so many variable factors that determine that actual usable horsepower of a given piece of equipment.

To summarize, the 16 HP lawn tractor mentioned cannot provide an actual 16 HP on the drawbar for several reasons. One, there is loss between the crankshaft and the drawbar. Two, the traction capability of the tractor determines the percentage of HP provided by the engine that can actually be translated into useful force. Third, the lawn tractor has to move itself before it can exert a force.

So,

Usable drawbar HP = Brake HP – auxiliary component deductions – force required to move tractor – tractor’s inability to sustain traction.

Don’t get hung up on the numbers, my purpose here is not to provide scientifically accurate data, but to communicate ideas. I hope it helped, and I am interested to see what other people have to say that I might have missed.

[Traveling Woodsman]

The numbers I quoted above were just off the top of my head, and I would be interested in knowing if anyone else has more accurate and precise numbers.
(At least some info. is available through a google search).

[Carl Russell]

Thanks Ben. This is a great explanation. It also leads into my comments which take into consideration the mental conditioning of the animals to respond to the required power. It is a factor left out of many discussions, but that momentary overload capacity that you mentioned is driven by an understanding and a desire that can never be engineered into a machine. And measuring drag, or pulling power required, may take into consideration the weight of an animal, it can never account for the heart, nor the skill and subtly of the teamster in getting the desired performance. This goes for pulling heavy logs, as well as dragging pastures.

Never-the-less, it is good to know how these numbers stack up, because it has become such a cultural assumption that even small machines are so much powerful than animals.

Carl

[Tim Harrigan]

Good explanation Ben. Some of the tractor inefficiency could be even more than you mentioned. For instance, if you had 60 hp at the flywheel we would expect 50 at the pto and only 25 at the drawbar in sandy ground with a 2wd tractor. Like Ben said, it depends on the ability of the tires to maintain traction. On firm ground we would expect to make 39 hp at the drawbar.

Your estimates of peak pulling power are interesting and I haven’t given it much thought. It would be interesting to estimate it some time. It would be fairly easy to do at a pull if they were pulling a sled that maintained a constant load such as a stoneboat. For instance, to calculate the instantaneous hp if a team pulled a 10000 lb sled in a 6 ft pull. The calculation would be lbs force in the chain time speed (mph) and that product divided by 375 equal hp. So you would measure the travel speed of the sled with a stop watch in feet per second (6 feet in 3 seconds would be 2 ft/sec). Also, the force is not the weight of the sled but rather the force needed to move it. If on a firm clay surface I would guess 1/3 of the sled weight in the chain. So 10000 x .333 = 3300 lbs force. Multiply ft/sec x .628 to get mph. So HP = 10000 x .333 x 2 x .628 = 4182. 4182/375 = 11.15 hp.

Carl is perceptive in emphasizing that horsemanship is not captured in this measure of performance.

[Traveling Woodsman]

Good thoughts. You’re absolutely right Carl in your comments on the variability of a team’s output. I of course know what you’re talking about, I just hadn’t connected it with this discussion.

Tim, I have heard it said by a number of different people that an athletic team in good shape, and like Carl says, in a good relationship with a teamster, can exert a tractive force equal to their own body weight. From all of the dyno pull results I have seen, this appears to be true, and in fact most records involve a greater tractive force than the animals body weight. Check this out http://www.horsepull.com/Record%20Loads.htm . This shows a #3000 team exerting #3650, and some heavyweights exerting #4900. Then it’s just a matter of determining speed. Dynamometers take all of the guesswork out of determining the actual force exerted, since like you said the amount of force required to move a given load is only very indirectly related to the weight of that load.
I’m sure though that making these records involved horse training methods that I don’t approve of. And the dyno track is an artificial environment that has little in common with a log and a wooded hillside. Just some hard numbers to talk with.

Good discussion.

[jac]

Wow !!! I had no idea mechanical power was so wastefull guys and inefficient. If these numbers relate to modern tractors just think of the blatent lies the farmers of the 20s and 30s must have been told to make them shift from horses..
John

[OldKat]

I seem to remember from an Ag Mechanics class that I took in college that the basis for a single “horsepower” was never actually measured. In other words the 550 ft / lbs per second was only a speculation on the part of whoever initially developed that equation. I have often wondered what the “real” measurement of horsepower would be.

I know that I have mentioned this before somewhere on this forum, but I forget where. Anyway, a guy I know told me that he was trying to disc his sandy loam property with a disc pulled by a certain number of Percherons. I think he said 7, but I could be wrong … maybe it was 5. Anyway, he unhitched and latched on to it with his 38 HP Kubota tractor and he said it was struggling to pull it as well. This much I remember for sure; he said he went back and added two Halflingers to the original hitch and they “walked away with it”. The reason I think he started with 7 Percherons is that I know that is how many he owned at the time.

Now he allowed as how he had to stop and rest the hitch, which he wouldn’t have had to do with the Kubota. Regardless, the Kubota could not effectively pull the disc where the hitch could. I did not witness this, but I think he is a straight shooter so I don’t think he was fibbing about it. I do remember that he had an odd number of animals, so I was wondering about how he strung his lines. I never did ask him about that though.

[OldKat]

@jac 15048 wrote:

Wow !!! I had no idea mechanical power was so wastefull guys and inefficient. If these numbers relate to modern tractors just think of the blatent lies the farmers of the 20s and 30s must have been told to make them shift from horses.. John

That is exactly why the University of Nebraska developed their tractor testing lab. A state legislator from Nebraska bought a tractor circa 19-teens that was so underpowered that it literally couldn’t pull its own weight. He was so mad that he introduced a bill and it passed & was signed into law establishing the University of Nebraska testing lab. Any model of tractor offered for sale in that state must be tested in the lab on a dynamometer before a single unit can be sold there. I think they measure draw bar and PTO HP, but I can’t recall for sure.

Over time they became the official testing lab for all tractors sold in the US. Not sure who, if anybody does this internationally.

[jac]

I remember reading somthing about how the big manufactureres actualy hired dealers to buy up good farm horses and create an artificial shortage !! Over here a major newspaper mounted a campaign in the 30s to rid the british streets of horse drawn transport. Some accountants challenged the figures about the costing of horse versus motor lorry but the horse was swept away regardless. Its interesting to note the amount of small business failures that happened after they made the shift to lorries.. Even today the figures dont add up… for short haul delivery work horses are without a doubt as cheap if not cheaper than lorries.. but the modern road and street layout make it hard for horses to operate A classic case of a lie being sold to the masses.. My original idea behind this discussion and subsequent info collection was that it may help a farmer make the transition back. If he or she knows a certain cultivator needs that 80hp Deere then he could work out how many horses he needs. Or even myself who up till now has done mostly wagon work and is moving towards using tractor implements behind a fore cart . Amazing feed back..
John

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