In Search of a Bobsled

[Tim Harrigan]

@Countymouse 32569 wrote:

…So, I think that by unweighting the nose we make the angle of approach easier, but will also increase the total amount of sinkage. Is it better to have more sinkage and preconditioning, or less sinkage and no preconditioning? … I still like the wider rear edge as this distributes the additional force over a wider area and minimizes high pressure areas that might increase total sinkage.

The soil is not homogeneous. Soil strength and carrying capacity increase as the soil is firmed up and compacted so you have probably experienced 90% of the compaction in the first half of the runner even though the rear is packing a heavier load. So you have diminishing returns working on it from that point. If you widen the runner in the back you are trading surface area for the plowing effect of the ever widening runner, and the trade-off is for snow-plowing tillage versus a runner surface on optimal carrying conditions. I think your system might have an advantage in bad conditions where flotation is of interest, but maybe less so under normal conditions.

So part of the trade-off generally is how wide should the runners be. If flotation is primary, wider is better, but we also need the runners to cut in some to hold the line on side slopes, etc. That is the big disadvantage of a stone boat on hilly ground. So it is tough to have one tool for all conditions. Interesting to think about what impact minor changes might have.

Oh yeah, where did you find that sled/stoneboat article? Is that on Tillers site? Have not seen that in a long while.

[Andy Carson]

I am trying not to sidetrack this thread too much, but I think my interest in the value of “floatation” vs “front end lift” is directly correlated to bunk placement, which is a big part of this thread.

Tim, I agree a wider runner would have more of an advantage in in rough conditions where floatation is a concern, but I am not sure these are not “normal.” Your work with the sled vs stoneboat (which I googled up) demonstates a significant draft advantage when you have floatation (via stoneboat) in “firm soil” and on “tilled and settled” soil. I think that “firm soil” is probably a really good “real world” representative we have for this work. Tilled soil is probably a stretch, but one areas where I have run my sled alot (particularly in corner where the runners push dirt around) I think its a good real world approximation.

As far as the wider rear track goes, I think you are right, Tim, that it would probably would snowplow dirt to the side if it was a copy of a parabolic ski. This effect could be fixed pretty easily though, by providing another angle of attack in the widened track area. This could be done by putting a runner next to the main and giving it a smooth downward angle of attack to push dirt down rather than to the side. If engineered well, having a narrow track in the front could provide positive tracking in the area where steering occures and provide floatation in rear where more weight is carried. It could be the best of both worlds, and looking at Tims stoneboat vs sled comparisons, there is room for a 25-30% reduction in draft with proper floatation if nothing else is lost. This much improvement seems like it’s worth serious thought.

[Tim Harrigan]

Why do I get the feeling that Andy is making room in his shop for a new project? 😀

[Carl Russell]

@Countymouse 32566 wrote:

… The only thing I am still not sure about is the statement that because the front of the sled is not lifted up very often or very far that the tillage aspect is not important or teh effect on drag is minimal

That is not exactly what I meant. What I was trying to describe is that by putting all these logs on a sled, either style, there is a huge reduction in friction. What I was indicating was that I don’t think the tillage from my sled would be significant enough over the other style in comparison with this aforementioned reduction, especially when combined with both the efficiency factor of less energy required to lift to reduce overall ground contact for starting, and the additional maneuverability provided by the rearward located bunk, to make that much difference.

I understand that with greater forward mechanical advantage for lifting, there is a greater force exerted against the soil at the rear of the runner than with the centered bunk, but it is a combination of efficiencies that create the overall functionality, and that soil tillage factor really doesn’t come into play in real working situations.

Carl

[Does’ Leap]

Great stuff here. It is amazing to think that this “conversation” on this scale could not have happened even 20 years ago, not to mention 100 years ago when use of sleds was common. Needless to say, I am sufficiently convinced – shorter runner, bunk back, load forward. I’ll keep you posted on its acquisition. Thanks to all.

George

[Tim Harrigan]

@Does’ Leap 32590 wrote:

…It is amazing to think that this “conversation” on this scale could not have happened even 20 years ago…

It is amazing, even 10 years ago I am not sure if it could have happened, certainly not with the speed that we see in some of these conversations.

I am indebted to Andy for digging up an article on sled and stone boat draft that I wrote with some folks at Tillers based on some work we did about 10 years ago. I had not looked at that work in several years and now when I look at it I find the introductory paragraphs explaining the motivation for the work to be more important to me than perhaps the work itself.

In writing a series of articles on implement draft, we at Tillers International are seeking to improve the relationship of people with their working animals. We are committed to easing the burden of animals as they help meet the energy needs of small farms.

If we lack an understanding of what we ask of our animals, we have limited means of knowing why they may act up in particular ways. If a teamster mistakenly thinks a load is light, he or she may become overly demanding. Underestimating a load may lead to a heavy whip and frustrate the animals into becoming nervous and unpredictable. Repeatedly overloading a team will discourage them and reduce their willingness to pull. Our goal is to enhance the teamster’s ability to match the power of the team with the demand of the load.

Estimating a load will take a little practice and attention. But you will be rewarded with a more productive relationship with your animals. They trust us to attend to such details and their trust grows as we demonstrate our trustworthiness to them. Those who have not worked oxen or draft horses may think this overestimates their perceptiveness and memory; nonetheless, experience clearly teaches the perceptive teamster that oxen and horses develop differing levels of trust and respect for variations among drivers. There are real benefits to be gained by understanding the loads you are asking your animals to move. Tillers hopes this article will help all teamsters empathize with the tasks they are presenting to their animals.

Now, with the benefit of hindsight, I can see how this philosophy has always provided guidance in my approach and interaction with my animals, and more recently in many of the discussions on DAP.com that I have been able to contribute to, particularly the times when folks were having trouble working through behavior or training problems, and in particular the need to ‘listen’ to your animals and attend to the details of the work and the relationship. So in looking back, with only three or four years experience with working animals at the time, I did not really know where this craft was going to take me, but now I can see that it was a path to higher ground. Not only to a deeper relationship with my animals, but to a deeper understanding of myself.

I hope some of you can find some value in it, it has been a great journey for me and this community of interest has been very important in the process. Thanks.

[Andy Carson]

One of the things that is so fun about these conversions for me is that there seems to be a variety of different approaches different teamsters take, when it comes to the “details.” The “detail” of bunk placement is a good example. These different experiences gives one the chance to form theories about bunk bunk placement (or anything else), present them, and have someone with first hand experience comment on them and say “Yes, that matches my observations” or “No, that not right because X, Y, or Z happens.” It’s kinda a test that I don’t have to do that informs theory and ultimately informs animal use. Sometimes it gets frustrating because observation (even careful observation) may not let someone know if the ground is compressed 0.5 inches or 0.6 inches, for example, and how much work went into the 0.5 inch versus 0.6 inch compressions. This is why I rely on and quote Tim’s work so much in these conversations. I few measurement in real work situations can go a very long way. I truly beleve that a synthesis of real-world experience and theorical knowledge can not only explain why some traditions tools work well, but can also improve them. Most importantly, though, I think this is fun to think about. I am glad that other find it fun to think about too.

[mitchmaine]

@Does’ Leap 32590 wrote:

Great stuff here. It is amazing to think that this “conversation” on this scale could not have happened even 20 years ago, not to mention 100 years ago when use of sleds was common. Needless to say, I am sufficiently convinced – shorter runner, bunk back, load forward. I’ll keep you posted on its acquisition. Thanks to all.

George

George, tim,
Do you mean this conversation couldn’t have existed 100 years ago because of the lack of a computer? Back then This conversation wouldn’t have even been necessary. Those guys worked in the woods and fields every day of their lives. They designed and improved the bobsled, scoot and d-ring harness. Not by accident but knowledge and experience. They knew how much they could load and go with, because they had done it a million times with good horses and bad, good scoots and bad, good woodlots and bad. They didn’t ask Archimedes to help them roll logs because he thought about it too much. Sometimes you just have to get down and get going and figure it out as we go. Those old guys are gone now and we have to remember what they said. mitch

[Tim Harrigan]

@mitchmaine 32600 wrote:

George, tim,
Do you mean this conversation couldn’t have existed 100 years ago because of the lack of a computer? Back then This conversation wouldn’t have even been necessary…

Mitch, I think we are following the faint trail of conversations and conversions that have gone on again and again over the years. The problem is there are not many around who share the interest and expertise. Not in my area, anyway. So DAP provides a way to connect and find others with shared interest. For the most part, we are not the innovators.

I think George was referring to the spatial or geographic scale of the discussions. We are not neighbors geographically, and that is how the discussions would have occurred in the past.

[mitchmaine]

absolutely tim,
i love this website! documented by the amazing number of times i’ve chirped in(823). too many times maybe, but just this morning on facebook, erika shared a european horse progress days, and i have never seen anyone hook a draft with a breast harness or a steer with a collar but they do over there and i wouldn’t have known it without her and face book so there ya go. thanks for being there and sharing. mitch

[Michael Low]

@Carl Russell 32524 wrote:

George, I think that the different design features have everything to do with the seasonality of the use. I want a sled I can use any time of the year, not just on snow. I think that his design gets away with inefficiencies that I don’t want anyway, but specifically during dry-ground use. The value of the single-bunk sled is, to me, too high to limit it to a few months use.

With the bunk back and log weight forward the fulcrum of extra runner length increases the horses ability to lift the weight, AND the friction of the load is reduced by shifting the dragging weight of the logs from that portion on the ground to the narrow steel shoe under two runners. These two factors contribute first by enhancing the bio-mechanics of the horses lifting power, which in and of itself reduces friction (by lifting a portion of the runner off of the ground), but having more weight on the runners than on the dragging logs, the load is easier to pull overall. This latter detail is minimized when working on snow and ice, but in my mind efficiency is efficiency, regardless of the circumstances, and with live power we can maximize our efficiency through the physical design of the equipment we use.

Also by affording increased lift to the front of the runner there is increased maneuverability by lifting the front of the runners off of the ground when turning. With the configuration of my sled, the turning occurs on the heels of the runners more than with Dwayne’s design, which again is less important on snow than on dry ground, but easier is easier….. and it increases the functional application of the equipment (more seasons that just winter).

When I say the horses shouldn’t put lateral pressure on the pole for turning, I mean that when they step gee or haw the sled should turn by being pulled in that direction from the evener, not by being levered over with the pole through the neckyoke. The pole should “float”. As true as this is, there are no doubt instances where there is some lateral pressure on the pole, and in those instances (holding back going around a corner on a steep hill) that I want the strongest pole/roll configuration I can have. I see the A-frame as the kind of insurance that when I need that kind of leverage that I can get it without compromising the integrity of the hitch and jeopardizing the safety and well being of myself and my horses.

As far as turning, even when turning at a stand still, I expect the inside horse to step forward. The power of horses is forward, not sideways. I will have them step over with an empty sled, but there is next to no pressure on the pole/roll connection in that maneuver. When turning a load, it is extremely inefficient to ask a horse to do so in a lateral movement. Time and planning should be taken to give the horses room to move forward while turning. By moving forward at the same time that they move to the side the power is translate through the evener under the load, and the load is turned with no lateral(lever) pressure on the pole.

I think that with long runners and the bunk centered, there is no advantage either for lifting nor for turning. Having the horses closer to the load in this case may seem like they should have more lift, but there is no mathematical advantage, runner length equal front and back, which amounts to a dead lift. And when you combine the fact that you are dragging more log length, it is a lose-lose situation. Then add in the longer runners that create more lateral resistance for turning, and you’ve lost my interest.

By placing the bunk back, it allows more weight to be put on the bunk(more to lift for sure), but by creating mechanical advantage (more runner in front than behind), you make up for that, and then when drawing the load friction is reduced, which in turn increases efficiency for the real power of the work, moving the load over the land. Shorter runners/less shoe combined with the front-of-the-runner-lifting makes much better turning ability increasing overall functionality…….

My sled was originally built by a man who lived near Walden. His family raised Brabants for years, and they logged and sugared with them. I didn’t buy the sled from him, I bought it from Walt Bryan. I never knew whether it was custom-built for Walt based on his own design, or whether it was a standard design that they used for their own purposes. I cannot remember the family name for the life of me….. maybe Dwayne knows who they were/are.

Carl

That would have been Francis Foster. Lived in Walden, and was one of the first to import Brabants into the country. That’s the same Foster who owned the mill shown in the Ben Thresher video. He supported a family, 12 kids plus 10 foster kids, on horse logging and eventually his sawmill. Quite a charactor who unfortunately died just a few years ago.
Michael Low

[Carl Russell]

@Michael Low 32642 wrote:

That would have been Francis Foster. Lived in Walden, and was one of the first to import Brabants into the country. That’s the same Foster who owned the mill shown in the Ben Thresher video. He supported a family, 12 kids plus 10 foster kids, on horse logging and eventually his sawmill. Quite a charactor who unfortunately died just a few years ago.
Michael Low

That’s the one….Thanks Michael.

Carl

[Does’ Leap]

I purchased my team from his son Archie – lives in Hardwick. Nice fellow.

George

[Carl Russell]

@Does’ Leap 32644 wrote:

I purchased my team from his son Archie – lives in Hardwick. Nice fellow.

George

Query him about sled hardware that might be taking up space in his shed…….:o

Carl

[Does’ Leap]

I already talked to him about it and yes, he does have hardware. I have a trip planned. He was telling me stories about bobbing logs as a boy. At 12 years old, he got special permission from the school superintendent (after being declared truant) to leave school at 9:45 provided his work was done for the day. Then he headed to the woods to meet up with Frances. His father and hired man served as choppers while he twitched and yarded logs and pulp with a bob.

George

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