[Andy Carson]

“I used to think that the engineers of the horse era were hampered purely by the technologies of the time, but now I see that they were stuck with the same laws that we face now. Any amount of modern materials and practices cant overcome them…”

I have designed much more equipment on paper than I have actually built precisly for that reason… I think it’s fun to design new ways of getting things done, but I have rarely made something better than traditional equipment. The process I usually go through is:

A. Research traditional equipment for performing a task
B. Think I know a better way to perform task
C. Do some math and realize that it won’t my “better” way
D. Try a different (but still improved) concept
E. Do more math and realize that won’t work either
F. Buy an old piece of equipment
G. Break the old piece of equipment
H. Repair
I. Break something that is irrepairable and irreplaceable (not hard)
J. Return to “A”

I am not saying it is not worth trying to make equipment better, but sometimes I feel like I have been reinventing the wheel. I do think the use of hydraulics is probably a modern invention that would lend itself to many horse powered applications. I have to say, though, the power required to lift 500 pounds at a slow rate is pretty small and well within human capability given mechanical advantage or the use of a spring. If you can use human power to do something, you can be much more flexible in how that power is delivered (levers, wheels, ropes, etc). We are agile and smart little monkeys, even though we are weak.

[Andy Carson]

Hi John, this sounds like a fun problem to work on… OK, lets begin with a hitch cart with 30 inch (2.5 foot) diameter wheels traveling at 3 MPH. 3 miles = 15840 feet per 60 minutes or 264 feet per minute. A 2.5 foot diameter wheel has a radius of 7.9 feet. 264/7.9 = 33 rpm. Lets assume you use a 1 foot diameter drive wheel on top of the hitch cart tire, that would be a radius of 3.1. So, for every rotation of the big tire (7.9 foot radius), the small drive tire would rotate 2.5 times (7.9/3.1) asuming no slippage. That would be 83 rpm (or 1.4 rotations per second). Now the big unknown is how many cubic inches your hydraulic motor displaces per rotation. If it’s only .2 cubic inches per rotation the motor would yield .22 cubic inches per second. A 2 cubic inch per second pump would spit out 2.2 cubic inches per second. The surface area of a 2 inch cylinder is 3.14 square inches, so the small displacement pump would move at a rate of 0.07 inches per second and take over 3 minutes to travel 12 inches. The larger pump would travel 0.70 inches per second and move a foot in 17 seconds. Either way, this is a pretty slow way to lift something… As 550 pounds travelling 12 inches per second is 1 HP, you have plenty of power for either of these conditions. Enough traction, though, I’m not sure… The spring that presses the small wheel onto the large drive wheel could be made to apply as much downforce as you design, but the downforce between the cart wheel and the ground would be roughly half the total cart weight (I am assuming this is a two wheeled cart). Let’s assume your cart weighs 800 pounds with you on it, that would be 400 pounds of downpressure on one tire. I don’t know what kind of wheels/tires you have, but I’ll assume a friction coefficient of 0.5. That means the tires might slide if more than 200 pounds force is applied to them along the ground. I’ll calculate the mechanical advantage over one second by using force x distance = force x distance. 500 pounds (1/4 ton) x 3.5 inches (fast pump) = 18 pounds x 94 inches. So, you are no where need a point where your tire will slide. You might risk a slide if your pump is 20 cubic inches per rotation, but that’s a big pump! You might want to run through my math again to check for blunders. I would think about using a couple drive gears to speed up your pump and make the whole thing lift faster (depending on the size of your pump).

[Andy Carson]

I have used this website for determining the size and shape of steel for different applications.
http://www.engineersedge.com/
The beam deflection calculators on this site are great and they have almost every different type of stress and strain imaginable. There are charts that tell you the moment of inertia for standard structural shapes (like I beams) or let you calculate the moment based on the dimensions and thickness (it will determine the moment of a 2×2 inch steel tube with 1/4 inch thick wall for example). They even have a trigonometry calculator for those of you that (like me) are not as confident of your trig as you once where… Optimising the size and shape of beams used for different projects makes the equipment lighter to handle and cheaper to make, without any loss of strength. For me, I have been suprised how far off my “gut reaction” was from the calculated optimal beam size. In most cases, I would have picked a much bigger peice of steel. Just a warning, these calculators do not have a safety factor built into them. I usually double the loads to engineer in a safety factor.

[Andy Carson]

Hi John,
Glad to hear it’s getting better. The clipping alone worked for me, but from the sounds of it, I don’t think my problem was as bad as yours. I just had lesions about the size of a quarter (or a couple of cm, if you prefer). I think alot of people would have let them go, but cronic infections like these bug me. I have never been to the UK, but it seems like it could get get pretty muddy there… It has always been interesting to me that Clydes and Shires both were bred in a relatively muddy place. Maybe if most horses legs are muddy, than ones with long clean white feather would really stand out and demonstrate the quality of the horse as well as the quality of the care it receives? Just a guess. Just for record, I still think feather is pretty. Best of luck,
-Andy

[Andy Carson]

Maybe I’m overreacting to the issue, but most of the hair rubbed off on one side in the last 3 or so snow plowing sessions and I was afraid of what would happen when the traces got down to rubbing on skin. Maybe the skin is more resistant to rubbing, or toughens up and this isn’t a problem long term. I still think I’ll try to sew on some soft leather pieces to provide a little more protection. I don’t see how it could hurt. I have some soft mooseskin left over from another project, so the cost should be minimal. I’ll take some photos to share if the thing turns out well.

[Andy Carson]

Thanks Grey. Easy to fix then, I’ll just swap out my traces for the biothane ones. I really do love my nylon harness, didn’t know it would rub like this. Is biothane the most gentle? I could sew on a leather tube…

[Andy Carson]

I personally have never got along well with geldings and have never had one, although I have driven a number of them. Some because I was interested in buying them, and some because they were friends horses. In my hands, geldings usually seemed either asleep, or interested in goofing around. I like a responsive horse and just wants to get the job done and doesn’t have to be told to “go” very often. While, it is true that the mares I have had will give 110% some days and try to give 80% on others, the vast majority of the days are 110%. Also, being “up” on most days lets me see what they are really capable of and let’s me know how hard I can push on “down” days. Honestly, I love to watch the mare that I have now buckle down and pull and know that it’s her own desire that is making her work that hard. She’s no record making pulling horse, but I admire the effort nonetheless. Also (and this might just be me) I have an easier time reading a mares emotional state. Maybe this is more because I am more used to how mares express themselves, but I think it’s probably because they have a little stronger emotions. It is true that I do on rare occasions have to deal with a balk, be strict about slowing down, or lead her through a rare patch of “scary” brush. I look at it that I make a few very small concessions to her emotional state and get paid back with 110% effort whenever I ask for it (and sometimes when I don’t). I think ultimately it’s a personal choice and there really isn’t a better horse, but I like mares.

[Andy Carson]

I reposted this on the horse forum, as I had not meant to post this question in the equipment catagory… I don’t know how I can delete this post here…

[Andy Carson]

Thanks alot everyone, and especially for the photos of the bridle chains. They look pretty simple to make and I am kicking myself for not thinking of that already… Mitch, the two systems (shafts and chains) don’t seem redundant now that I am reading and thinking about this. When I only had chains (I had a much less eficient way of attaching the chains) I had to fuss with them all the time, engaging them on slight downhills (and sometime wishing I had them on to stop on the flat). When I tried shafts alone, I was disappointed that they didn’t have enough braking power for steeper downhills or heavy loads. I think I didn’t have much success because I was trying these things in isolation and not as part of a unified system. I suspect I will have to futz around with the shafts a little to adjust them to have just the right amount of pivot, but that might be a fun winter project. The chains look like there wouldn’t need much in the way of fine tuning.

[Andy Carson]

Wonderful!!! I thought there must be better solutions out there than what I was trying

[Andy Carson]

Thanks for the thoughts, I have done alot of work with the stoneboat in preparation for farm work. I’m glad it wasn’t wasted. She will pull 1800 pounds for about a half hour over rough terrain with mild hills, and 1320 for about 2-3 hours over the same terrain. It took about a year to get her in this good of shape and 1000 pounds is not hard for her at all right now. I’m glad to hear that this is a good way to know and that I haven’t been wasting my time on the sled.

[Andy Carson]

Thanks Donn, I haved tried putting shafts fixed in place on the front of the sled, but it made the it very hard to turn. I use the sled alot in the woods and need to be able to turn tight… After that, I added a pivot point so that the shafts could turn with the horse instead of being stuck pointed forward. That made turning easy enough (not as good as without the shafts) but on downhills the sled had a tendancy to want to slide “around the horse” (downhill to the left or right) and was hard to keep straight. Maybe some system that has removable pin in it to allow for pivoting when I need manuverability and rigidity when I am going downhill would be best. Chains under the runners do work great, they just require alot of “fussing” if you don’t have shafts holding you back on even mild downhills. I bet if I get a shaft set-up that allows for the amount of manuverability I like, though, I won’t have to “fuss” with the brakes so much. Maybe that is where I ought to be spending my designing efforts.

[Andy Carson]

I think I have the plans worked out so that I won’t have to do a lot of plowing (what I was worried about with a single horse) and can use the springtooth in areas that have been worked last year and were planted with crops that don’t create sod. According to my plans, I expect to have about 3/4 of a an acre that would need plowed under year (as it would be planted with rye as a cover crop). I think it’s not crazy to expect a single horse could do that. Do any of you all have experience with a single horse plowing? Is a 10 inch plow the right size for a single hard working draft? I saw I&J makes one, but would prefer to get one a used one cheap if possible. I haven’t seen any at auction, though, are they pretty rare? I have seen alot of 12 inch plow, but I think this is too big.

[Andy Carson]

Banei (Japanese draft horse racing) provides another example of the horse power with a little more endurance involved. The record for the 200 meter Banei Kinen race is 3 minute 8 seconds. That’s 2.4 MPH. In the deep sand, I would think the draft of the 2200 pound sled (pulled singly) would be to be 880-1100 pounds (0.4-0.5x). Using Ben’s formula, that ends up with 5.6 to 7.0 HP for this very stout horse.

[Andy Carson]

I agree that, in general, these numbers do not take into account many factors (such as the overload capacity, maneuverability, low impact, etc) that make make draft animals so attractive. I do think they are important, though, as they demonstrate to both the general public and to potential users of draft animals that we (as users or draft animals) are not “backwards” and there are real, tangible, and important reasons to use draft animals.

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