Draft buffers

[Gabe Ayers]

I don’t want or intend to bump JAC John’s post or question but thought this photo from a top horseman in Europe may be interesting for the buffer discussion.

[Andy Carson]

It is a very interesting design for a buffer using a much smaller and more managable spring. From the looks of it, I would guess these are more for shock protection, but I am not sure. It would be nice if anyone could report on these. They might be able to tell us if the springs are compressed very often during regular use (as opposed to only shock loads) and if they seem to help for other applications, such as starting a heavy load.

[Tim Harrigan]

My guess would be a relatively light load buffer, probably for wheeled vehicles. Looks to me like it might buffer the start and lower range peaks. I would expect to bottom out most of the time with skidding loads.

[Andy Carson]

It makes me really wonder. Maybe I am “reinventing the wheel” here and the Europeans already have a system to do this… The picture doesn’t look like they were pulling a wagon with this set-up, there is no breeching and it looks like the horses are to be attached to whatever they are pulling with a dragging chain. I would have guessed this to be a heavy dragging load, maybe a log? I am really curious because when I had first calculated the size of the spring, it seemed that a very large spring was needed. A large spring would be needed to equilibrate and store energy over a 0.2 second interval with the variations in speed that Tim had reported. After having done several runs, though, I can see the spring rarely compresses more than 1 inch over the preset. My interpretation is that with the spring equalizing and buffering the pull, variations in speed are minimized. If variations in speed are minimized, not only would that serve to reduce the spike forces, but would also reduce spring movement significacntly. Long story short, it seems the spring might not need to be as long as I had initially thought. Also, after having bagged on (somewhat) progressive springs, I am beginning to think that they might be better for this application. A progressive spring might make this system smaller and easier to handle, adjust, and implement, and increase the range of loads that could be effectively buffered. It would be very helpful to discuss how the springs that Jason posted work, and what they are effective at doing. Maybe one of our European friends can help us out here.

[Carl Russell]

Not to mention that each horse has its own buffer, allowing for the smaller spring. I like the way this is set up, as it could allow for a shorter hitch, although not taken advantage of in that pic.

Carl

[Tim Harrigan]

Countymouse;17781 wrote:

The picture doesn’t look like they were pulling a wagon with this set-up, there is no breeching and it looks like the horses are to be attached to whatever they are pulling with a dragging chain. I would have guessed this to be a heavy dragging load, maybe a log?

I also am curious about this tack and how/what it is used for.

[Tim Harrigan]

Countymouse;17781 wrote:

I can see the spring rarely compresses more than 1 inch over the preset.

Andy, I thought you were targeting the higher end by selecting the preset level. It seems like you would not expect to see a lot of spring action by doing that. And, maybe I am not remembering correctly, but didn’t you fall in to annoying harmonic oscillations of the spring when the pre-set was set too low for the load? That hitch uses two small springs, one on each singletree rather than a single larger spring. Maybe they are targeting the lower end and the starting forces.

[Andy Carson]

Tim,
Yes, I did fall into harmonic oscillations when the spring was set too low. These seemed to be counterproductive and annoying, especially when the spring had “swung” to a nearly compressed setting and the horse felt an unexpectedly heavy load with no way to anticipate it. I was suprized that it really doesn’t take much preload adjustment to prevent these harmonic oscillations. As long as the spring falls back to the preset level at least once during the normal cadence of the horse, the oscillations are prevented. At the beginning, I tried to adjust the spring so that it was compressed only slightly during the very brief “spikes” in draft. After trying several settings an load, it seems that this fine tuning is not as important as I had initially thought. It seems that as long as the spring is compressed at least once and comes to rest at least once during the normal cadence of the horse, all settings and loads behaved similarly. The only exception to that is the “no head bobbing” rhythm that does seem to require very fine tuning. At any of these settings (where the spring regularly alternates between compressed by the horse and resting at the preset) the spring compresses no more than 1 inch in addition to the preset. Usually the compression is much less during the normal rhythm, in the range of 1/2 inch. This is very interesting to me, because part of the reason that I had chosen a large spring was to prevent the spring from bottoming out when absorbing the power from a 0.2 second spike. From calculations of Tim’s data it seemed a large spring was needed for this, but in practice it seems a smaller spring would do fine. I suspect that the spring can buffer forward velocity, and that the buffering of the forward velocity also reduces the height of the “peaks” in force. In other words, the horse doesn’t feel the sled slowing down, and doesn’t put out a strong push to get it going again. This could explain why the spring doesn’t seem to compress as much as calculated and seems to indicate a beneficial effect. So, in the end, I think the the preload on the spring has more utility in preventing harmonic oscilations than in selecting which forces to buffer.

[Roscoe]

@Tim Harrigan 17785 wrote:

I also am curious about this tack and how/what it is used for.

This tack is only used for skidding logs, the tracekeeper are made from bungee cord, and prevent from stepping over the traces.

When I attended by logging contest, I used bungee cord as well, attached by the brechhing seat. But I used a differnt adjusment. The horse never had the singletree at the hocks.

[Tim Harrigan]

Thanks for the explanation, Roscoe. Can you also explain what you see as the benefit of the draft buffer springs in the singletrees?. Would they be primarily for starting the load, smoothing out the pull in transport, shock absorbsion when hitting obstructions, or other benefits? Thanks.

[Andy Carson]

I had not appreciated how much of a turn off the sheer size of the spring and holding apparatus would be… The change in draft angle is substantial with this 16-18 inch long mock up and this change might be as important as the spring buffering effect. I am going to work on a slightly different design that makes the whole apparatus smaller. Any other ideas for improvements? This designing has been alot of fun and it sure makes “conditioning time” with my horse more interesting.

[Roscoe]

@Tim Harrigan 17801 wrote:

Can you also explain what you see as the benefit of the draft buffer springs in the singletrees?. Would they be primarily for starting the load, smoothing out the pull in transport, shock absorbsion when hitting obstructions, or other benefits? Thanks.

I think for all three.
My Opinion is, that it doesn’t matter if the buffer is a part of the traces, singletree or doubletree for the function. I used http://www.fanac.ch/zep-f-.htm . This poly rope is for sure rougher then a leather trace, but never had a problem.
Look also http://www.fanac.ch/ zep.html
I Switzerland, it was also common by heavy freightwagons the using of doubletrees with a built-in spring.

Sorry for my poor english, after beeing a year here in Canada, it is still hard for my to write in english…

[Andy Carson]

Thanks Roscoe, It’s nice to know that versions of these buffers are used for several applications around the world. That gives me a good feeling going forward. I’m working on a leaf spring design that will essentially substitute for a singletree. It ought to have as much free motion as the coil spring with a similar spring rate. Hopefully, this design will be easier to adjust and allow the user to preserve a “standard” line of draft. The design is more fucused on making the concept as practical as possible. More details to come…

[jac]

In January 1927 Herman Ruedebusch patented under US number 1614994 an adjustable horse collar that was pneumatic !! My question is this… would this be a better buffer, as it would be lighter and Im sure very comfortable on the horse ,than springs which will undoubtably add weight ?? also is there any difference in the buffer effect in relation to where the buffer is placed..ie at the initial point of pull from the animals point of view or on the machine end ??
John

[Tim Harrigan]

John, I am not sure what difference it would make where in the system a buffer was. It seems like the crosscutting issues are response rate and the range of response relative to the demands of the load. Those are the basic issues we have been puzzling over and the things that Andy wants to address in his work over the next few months. I hope we can develop some reasonable and defensible recommendations. Thanks for this information, I not heard of that before.

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