Draft buffers

[Andy Carson]

Mitch, I’m glad you had a chance to try out a spring too. Even those many of the observations that both you are I am making are subjective, if different users see the same things, then they are more likely to be true. I do think that the springs in a spring tine harrow would act as buffers, but I am not sure if they would be in a range to be effective. It seems that the spring constants and response rates need tuned to a degree for the buffering to be most effective, and I just don’t know if the spring tines are there. I think that a committed buffer designed to respond to the predicted loads would be ideal, and yes, Geoff, I think that a spring tooth is great application of this technology. So comparing Mitch’s and my runs. Mitch, correct me if I’m wrong, but I think you are using a spring without a preload? Some differences might be attributed to this.

1. We both see a reduction in the power required by the front limbs
2. Mitch noticed a greater tendancy to walk, I can see this without a preload, but with a preload, my horse has a tendancy to go faster
3. I noticed a swinging action of the sled without a preload, which alternated high and low drafts and annoyed my horse. Mitch reports a jerky motion that his horses did not seem to be annoyed by. I am not sure if this refers to the whole implement or individual springs, but if it is the whole implement, than perhaps the “jerkiness” vs “swinging” is the same phenomenon occurring as a different frequency because of different spring constants and spring lengths.
4. I noticed a definite smoothing of forward speed, and I am not sure if Mitch sees this. I have to say, though, a periodically nosediving springtooth would be a lot more difficult to smooth than a sled.
5. I noticed an easing of effort to start loads, I am not sure if Mitch sees this…
6. Mitch reports as overall easing of effort, and I do not see much of a difference in effort. This is likely because my horse is a workaholic and if she feels like the load is easier than she just goes faster. I do notice that my horse speeds up with the buffer so perhaps these observations agree as well.

Very interesting to compare experiences. Perhaps if we could hear a little more about Mitches spring it would be helpful. What are the dimensions of the spring? Do you have an idea of it’s constant? How did you hook it up? Does it seem to be compressing or extending very often? How far does it compress when it is in action? Does it ever seem to bottom out?

[mitchmaine]

[ATTACH]1177.jpg” />

[ATTACH]1178.jpg” />Geoff, trying to attach some phots of the harrow and spring. it’s a 6’set of pioneer spring harrows. can’t show you the ground it was on, but imagine your driveway. with the points down, it lifted the harrow frame clear of the ground, and would walk on the points until it bit in and went.

[Tim Harrigan]

When I measured the draft of a springtooth harrow on ground that had been plowed in the fall then disked in the spring the draft was very sensitive to depth of tillage. We used a 22-tooth harrow and a map of the tillage draft across the field is attached for 2-inch and 3-inch depth. We did some measurements at 4 inches but I thought it was unreasonable to ask the team to work at that level for very long. On a per tine basis the average draft increased from 19 lbf per tine (418 lbf for us) at 2 inches to 28 lbf per tine (616 lbf for us) at 3 inches to 45 lbf (990 lbf for us) at 4 inches. The frequency chart shows the frequency of pulling forces in 100 lbf increments for each tillage depth.

I have noticed that folks just really like to bury those tines in the ground but there is really no need for it. At 2 inches you get reasonable leveling, breaking of crust, sizing of soil clods and uprooting of weeds. At three inches you get all of that plus you pull up buried residue and dry out your seedbed. At 4 inches you get a dried out seedbed and a tired team.

The left half of the field was harrowed at 2 inches, the right half at 3 inches. The high draft area in the southwest corner was were we started picking up and dragging some sorghum residue that fell into the field from the field next to this one. The really high draft in the northeast corner was with the tines set at 4 inches.

[near horse]

I mentioned the spring tooth being drug almost under the soil surface at the plowing event I went to this last weekend (in another thread). 4 abreast pulling the forecart w/ ~8 ft of springtooth overflowing w/ topsoil – tines weren’t down much at all – the frame of the springtooth was doing the “work”. This ground was freshly plowed and pretty loose but I think some of the troubles had to do with how the springtooth was hitched.

Some of this spring stuff is pretty interesting – keep up the good work. I might need to try setting up something myself.

[Andy Carson]

Geoff,
I am glad you are interested in trying out a spring buffer too. The buffer is really pretty easy to make once you have the spring. If you are going to get one for a team, you may have the best luck with a 12 inch (more or less) long spring with a rate of 250-300 lbs/inch. I think mine (119 lbs/inch) could use a little more “umph” and of course a team would need twice that. McMaster-Carr, sells a 12 inch long spring with a rate slightly over 300 lbs (96485K455) for $40, but you might get off cheaper by finding one at the junk yard. This is in the range of coil springs used for the rear suspension on some passenger cars, but there is alot of variation in these cars. Alot of these springs are going to be “progressive” and will be easy to compress at the beginning and become more and more difficult as the spring is compressed. The wires coils of progressive springs are usually close together at one end and wider spaced at the other end. I thought it was easier to do the modelling on a nonprogressive spring, but a progressive spring might work too. You can roughly determine the spring constant on a nonprogressive spring, with some weights and a measuring tape. You would be looking for a compression of about 1/4 of an inch with a 60-75 pound weight (or 1/2 inch movement with 125-150 pound weight). A progressive spring would need to be calibrated thoughout it’s load range, which would require a more complex set up, but might be the best way to go. Still alot to know…

By the way, I took a look at the paper that you posted. I was very interesting and well written. I thought the measurement of power versus speed was very interesting, as when the horse slows from 2 m/s (4.5 MPH) to 1.4 m/s (3.1 MPH), the power drops off only slightly, but the power is cut in half when the speed is reduced to 0.5 m/s (1.1 MPH). These lower speed higher draft numbers were from another paper they referances and are the white squares in figures 6 and 7. I was also entertained by the comment that the draft force was set at an upper limit of 20% because the Thoughbreds “became agitated if asked to exert greater force.”

[Tim Harrigan]

near horse;17688 wrote:

– in the TB vs Draft horse comparison while both had similar peak force-speed , the draft achieved it at 2 m/s (~ 4.5 mph) vs 5m/s (~ 11mph) and the experimental treadmill couldn’t be set any slower than 2 m/s. Perhaps the benefit of the draft animal is the force generated at low speeds – much more practical for farm work.

The typical travel speed for drafts for farm work is about 2 mph, about 1.75 mph for oxen. So the treadmill really was not representative of typical work. I have not read the article, not sure if it makes any difference.

[near horse]

I agree Tim and that was sort of my point – at first it is impressive that TB’s can attain relative peak force-speeds as the drafts (relative to body size) but they are achieved at rates of travel unfit for farming. In this study they couldn’t run their treadmill slower than 2m/s – the slower speed data points that Andy mentioned came from a 1934 study
Procter, R. C., S. Brody, M. M. Jones, and D.W. Chittenden. Efficiency of work horses of different ages and body weights.
Univ. Mo. Agr. Exp. Sta. Res. Bull. 209: 1934

[jac]

I have been reading this thread since it started with great interest and totaly applaude the work that has gone into this by all involvd. Have to admit Im not that great at the maths and physics tho… I was advised to ask you this question by a friend after he and I had discussed the subject, so here goes… Is there a possibility that, if we use too many mechanical draft buffers we insulate the horse/ox from the forces that, at present they can react to instantanously..balance, weight transfer ect.. way before we mere humans can see there is a problem ?.. A bit like when power steering was put on cars.. we lost the “feel” of the road….I read somewhere that the more a driver is insulated from the suroundings the less he is able to react.. Will the animals not have the same problems ?..
John

[Andy Carson]

John,
I think this is a good point, and yes, there seems to be a different “feel” to a load (at least when I’ve pulled with a buffer). Ar first, my horse seemed to think that since she was not feeling “hard bumps” when she pulled (and especially started) a load, the job was going to be easy. The sled was still heavy though and was hard work to pull… So even though she wanted to take off at the beginning, she learned what the “feel” meant after a short time (maybe 5-10 minutes) and learned how to pull with it. I think that animals have great intelligence when it comes to making physicaly adjustments to different physical “feels” or “rhythms” but I see your point about the “insulating” effect. I am not entirely sure how I would know if the buffers were inhibiting the animals reaction rate. On the runs I’ve done, there was nothing obvious, but I wasn’t looking for this effect. What kinds of behaviors should I be watching for?

[jac]

Andy Im not sure on that one.. Perhaps a delayed reaction that we might not even pick up on. a head rising for a second or even ears going flat for a second when we wouldnt expect it.. but I fear that any reaction would be over and dealt with by the animal before we could determine when it happened.. I suppose a video linked to sensors in the collar and then a bucket load of time watching the screen to try and see if a negative reaction from the horse coresponded to peaks or troughs in the draft/terrain… but that sounds like a project for NASA 🙂 Thank you all again for all the effort you guys have put into this..
John

[Carl Russell]

Thanks John, I was making this point earlier. The effect of the buffer is distinct, and theoretically it can have some beneficial effect of the spikes of draft that the animals have to respond to. However, in my mind training and conditioning a horse to use its weight and power effectively against a load is part of the package that is the working animal.

So to try to completely replace that with a buffer probably doesn’t make sense, but certainly figuring out how to use the concept to give advantage where it is practical and important seems to make a lot of sense to me.

Carl

[Tim Harrigan]

John, you make a good point and I agree that it certainly is possible to have unintended consequences when making these modifications. I have already explained and have shown situations where, at least with the draft buffer I used, there are situations where buffers can actually be a drag on the system. Andy explained seeing harmonic oscillations that he interpreted as annoying to his horse, so buffers can also be counterproductive. I have seen other cases where the buffer was no benefit and in at least one case a buffer reduced draft almost 20% with no negative consequences. So there are a lot of possibilities, we just do not have many practical guidelines for selection and use of a draft buffer.

The challenge is that horses and oxen are effective in buffering the effects of draft so it is really hard to visualize or confirm the impact of a buffer. It is hard to watch a team and draw defensible conclusions because unless you are working near the edge of their capability they do not seem to reveal a lot. Part of the problem is that we can’t see the nature of the forces pulsing through the traces or towing chain. Even when we can get a look at the forces such as in the graphs I showed it is quite a challenge to interpret them in a practical and meaningful way because the animal can only inform us by it’s behavior. And, that assumes we can correctly interpret the behavior.

This thread has been about discovery. I like the turn it took from a display of forces generated to the practical implications of modifying those forces to linking and interpreting changes in animal behavior in response to those modifications. Andy’s work has the potential to be very informative. But we are still working around the edges of the bigger picture. Proper harness or yoke fit and design, hitching, conditioning and reasonable expectations have potentially a much bigger impact for our community of interest than a draft buffer. There is a possibility that in some hands a buffer could be another excuse for poor management or a lack of skill.

A draft buffer is a tool that could have a place and value in easing the burden of our draft animals by improving animal comfort and productivity. But it has to be practical. I think there is a certain practicality in a buffer for shock load protection, and perhaps in trimming peak pulling forces above a pre-set level. That practicality means the buffer will not be in action very often. I think it would be possible extend those benefits to a wider range of pulling forces but at the cost of more management and fussing around. There is value in that in the discovery process, but the practical use drops off. I don’t think anyone is suggesting everyone needs a draft buffer but there is potential value for many situations. We can still learn a lot with some fairly simple measuring of pulling forces coupled with close observation of behavior.

The better we understand the nature of the forces that are transmitted to our team and understand how our team responds to those forces, the better we can demonstrate our trustworthiness to them. That will be returned many times over by the trust they demonstrate in us.

[near horse]

There is a possibility that in some hands a buffer could be another excuse for poor management or a lack of skill.

This is a very good point Tim.

Overall, I believe we need to mindful of the abuse of this (or any) “technology”. That said, the long history of development of various implements, uses and methods of work employed by those using draft animals has (and does) certainly require adaptation on the part of our animals. Their ability and willingness to adapt to the challenges we place on them is one reason I enjoy working with them.

[Andy Carson]

@Tim Harrigan 17743 wrote:

…Proper harness or yoke fit and design, hitching, conditioning and reasonable expectations have potentially a much bigger impact for our community of interest than a draft buffer…

Having bought an out of shape horse, I can report that huge increases in sustained pulling power are possible with steady work and simple conditioning. Those increases make the 20% increase possible with the buffers look like a joke, no doubt. Still, an animal that is in good condition that is working near it’s limit would have to appreciate a 20% reduction in their workload. From the experiments I’ve done, it does seem like a particular buffer will have a somewhat narrow range of average drafts they will buffer at any particular setting. This isn’t a serious limitation in my mind, because I think there is only a small range of tasks that by their nature, would benefit from a buffer. For a small increase in efficiency to have practical utility, I would think the task would need to be long term. Similarly, I doubt that there is an practical utility in bothering with buffering really easy jobs. That’s what led me to pick a “useful range” of 300-500 pounds for one horse, and the buffer seems to require little adjustment within this range. Tim is right that since this is not near the short term limits, it has been difficult to demonstrate effectiveness. In giving directions for springs and whatnot, I am not advocating that everyone use the buffer for everything, I was simply saying “Hey, here is a simple tool that is pretty easy to build. Give it a try. Use your judgment and common sense, and see if it helps out.” After several runs with different set ups, I am becoming more confident that there are benefits of this buffer when adjusted properly. Still, only when a several people try it out at different tasks can we reach some sort of consensus.

[jac]

Being from Scotland I cannot comment on the really big teams like 8,10,12 and upwards. but I was wondering if that sort of hitch has the potential to compromise 2 or 3 horses without the teamster noticing especialy if they are on the upper limits for draft …or does the sheer scale of the hitch act as a buffer in its self ?.
John

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