[Andy Carson]

Looks great Phil. Does it seem to help with the loads? Does the spring rate seem appropriate? Any oscillations or threats of bottoming out?

[Andy Carson]

Thanks Geoff, and don’t worry about criticism. Without constructive criticism, I wouldn’t have gotten this far…

Yes, the spring floats on the angle iron and is only attached through the center bolt. The spring is prevented from twisting by the angle iron, and the center bolt holds the spring in place really well even without shackles. I had initially been thinking about incorporating a shackle-like system if this showed potential but am not so sure now. The shackle would add minimal length and largely get rid of the friction, but it seems the friction is helping somewhat in this system. I would like it to be a little slicker though. I had sprayed the ends of the spring with WD-40, but think I will try some more advanced lubricants before I make a shackle. I have also been thinking of attaching some teflon to the contact surface between the angle iron and the spring ends. That might be as friction-less as a shackle anyway…

The leaf spring arch is a funny thing and very counter intuitive to me. It seems stiff at the beginning, then gets more responsive, and might stiffen again when the spring is almost bent the wrong way. I will know more when I do a complete calibration curve. I started one, then didn’t believe the numbers and decided to do it again with the same set-up I used for the coil spring. The spring I bought was from tractor supply (part number #1750195) although I am using only two of the three leaves it came with. I took out the middle leaf as it seemed too stiff with all three leaves. My horse rarely got through that stiff initial spring constant into the “responsive area” with all three leaves, but with two it works great. Drilling springs, by the way, is tough work. I got a tip off some other message board that you can use a masonry bit for it. True, but it ruins the bit. At least I didn’t ruin one of my good bits!

[Andy Carson]

Report from the leaf spring draft buffer…
One of the important differences between this buffer and the coil spring buffer is that friction must be overcome to compress the leaf spring buffer. Personally, I attribute most of the differences I noticed between the coil and leaf spring buffers to this attribute. In all honesty, the spring rate is also different as well as the distance of spring travel, but these seem like subtle differences to me and do not account for the phenomenon I observed…

1. Easing the starting of a load
This seems just as efficient with the leaf spring as with the coil spring. As the forces are rather high here, it is not surprising that the additional friction from the leaf spring has no effect here.

2. Smoothing of the forward speed/prevention of stopping
The leaf spring was not as efficient at smoothing forward speed as the coil spring. It is definitely smoother than without the buffer, but doesn’t achieve the “boat-like” feel of the coil spring. I attribute the small “bumps” to transmitted draft forces that were not great enough to overcome friction in the leaf spring.

3. Reducing maximum draft forces
Unknown…

4. Easing the strain on the front quarters
Still a definite decrease in strain on the front quarters, but not quite as efficient as the coil spring.

Even though the leaf spring does not seem as efficient of a buffer as the coil spring in some ways, it has one HUGE advantage. It can operate over a very wide range of loads with no need to adjust the preload on the spring. in fact there is really no need to preload the spring at all. I found this out by pulling a standard weight sled with a “light” preload. When I noticed the buffer was acting as it should (I had expected oscillations), I adjusted the sled weight and preloads up and down and the spring acted as it should at all weights and preloads I tried. Probably because of the friction, I do not see any harmonic spring oscillations at light preloads, and there was no threat of the spring bottoming out even with a heavy sled. The design also maintains a line of draft that is efficient and doesn’t take up any more space than a standard single tree. I am pretty happy with this! I might try something to decrease the friction a little, but I don’t think I want to get rid of it altogether anymore. I think it’s almost done!

[Andy Carson]

Yes, I will definately be splitting it up into 1 acre plots with crops that have different planting and harvest dates. A couple trips around the field convinced me of that fast! That will be next year, though, this year I just want to focus on letting the land recover and gettign things set up for next year.

[Andy Carson]

I finally figure out for sure what was sprayed on this corn field last year. Bicep II. I googled that this has two active ingredients, S-metolachlor and atrazine. Does this limit my planting options? I’m probably just going with a cover crop/green manure this year to rejuvenate the soil.

[Andy Carson]

What about using a compressed air tank or a car battery to run a motor that spins the disc at a constant rate? I know it’s not primed by the weight of your bag, but it might be easier to set up and could use more “off the shelf” parts… At first pass, I would think there would be enough energy in the weight of that bag to power the spreader, but it seems the friction in a system like that would likely be substantial.

[Andy Carson]

@Plowboy 17967 wrote:

Hitching too many horses abreast causes side draft on the horses when plowing. The hitch point and the center of draft are too far off on a two bottom to track right.

Thanks Plowboy, I figured there must be a good reason I have never seen more than four abreast…

[Andy Carson]

I am just curious… What is the advantage of setting up the horses with 3 leaders and 4 behind rather than 7 across? It would be a wide hitch, but the field looks big and flat. It would maintain an efficient line of draft. Is turning the limitation?

[Andy Carson]

Here’s the new draft buffer, this design incorporates a small leaf spring into a singletree. It’s very simple, easy to build and adjust, and doesn’t add any appreciable length to the setup. The leaf springs seems a little less linear in it’s response, and I am going to have to calibrate the spring with known weights, but am pretty happy so far. I am most concerned about the sliding of the spring loops over the angle iron. I greased the contact points, but if it takes a beating, i might put some plastic over it to keep down the friction.

[Andy Carson]

Here’s the new draft buffer, this design incorporates a small leaf spring into a singletree. It’s very simple, easy to build and adjust, and doesn’t add any appreciable length to the setup. the leaf sprign seems a little less perdicatble with it’s response, and I am going to have to calibrate the spring with known weights, but am pretty happy so far. I am most concerned about the sliding of the spring loops over the angle iron. I greased the contact points, but if it takes a beating, i might put some plastic over it to keep down the friction.

[Andy Carson]

John,
I think that for a buffer to be effective, it must not only absorb the peaks in force, but also release that power in a way that be converted into useful work. I think it is likely that a pneumatic collar pad could be designed such that it could capture the peak force, but I am more doubtful of it’s ability to release that captured energy in a slow, long push. It is interesting that I was just talking to an engineer friend on mine who had been thinking about the use of a pneumatic air bag (made from load levelers). One abvantage to this system is that the pressure could be adjusted over a pretty wide range for different application. That essentially adjusts the initial spring constant of the system. The downsides are that while a spring can be adjusted in the field with a wrench, an airbag would need an air pump, and probably a high pressure one. Also, force versus volume in an air bag is an exponential fuction (pressure doubles every two fold reduction in volume) which means that there might be a limited range of travel where the response rate would properly act as a buffer in this system. That range can be extended (as in the long compression spring) by increasing the length of the apparatus. This might be great if it weren’t that I am trying to minimize the size (and especially the length) of the buffer to preserve the line of draft.

PS. Some of my experimental observations can speak the importance of response rate. I was able to adjust the initial spring rate in the first buffer by adjusting both the preload on the spring and the load on the sled. Although this study is very limited, I did not see any evidence that spring response rate can be too slow to be effective (as in a light load with light preload). I did, on the other hand, see that response rates can be too fast for efficient buffering. This was most evident during harmonic oscillations of the sprign with a light preload pulling a medium load. When the natural peak due to horse stride occurred at the same time as the most compressed oscillation of the spring, the spring nearly bottomed out. From my observations of the horse, this looks like this process results in a hard “pop” in draft, followed by a return to a normal pull. In theory, there ought to be a “push” of energy return there, but I can not see one and it is likely too fast to be useful.

[Andy Carson]

This sounds like a great project. I am excited to see pictures and hear how the venture goes. Best of luck!

[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…

[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.

[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.

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