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Leg angles for 3 leg splay stand


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Okay, I found my notes. Since no one answered, I will assume that either no one knows, or at least doesn't know well enough to explain it to a 5 year old :)

In case anyone else would like to design something top heavy that won't tip over I will put enough of an answer here that it will jog my notes. 

To start with the magic number seems to be 18 degrees. And, it is really that times 2. 

Here is the concept
1. determine the center of mass for the item, for example if you wanted an 10" tall anvil on a stand that placed the top of it at 30" off the floor, it would be ~35" assuming the stand had no weight to contribute. That assumption will simply place the center mass higher and calculate a base perhaps a little wider than necessary. Let's just call it a safety factor :)

2. Making an 18 degree right triangle the height of the center of mass in both direction for 2d or conically for 3d will make the minimum stability circle. You can do some calculus or trig to calculate this, or simply draw it and measure. (I simply use Inkscape) In this example the base would be 11-3/8 from the centerline out. So the base width would be almost 23". (A circle with a radius of 11-3/8) 

3. All leg points in contact with the ground need to fall outside of the above height. Regardless 3 or 4 or more legs, or full block stand. The implications are that wherever you attach the legs will actually determine the splay angle. In theory, if the mount plate were as wide as the stability width then you could have zero splay legs at the outside corners zero splay. As the mount points for the legs move more towards the center the splay will increase. Since the mount plate is below the center of mass, then it would be potentially possible for the splay to reach beyond the 18 degree point. 

4. This really only gets trickier when what you are trying to put atop the stand is significantly taller. That would raise the center of mass requiring a wider stability circle. But I digress. For short items (relative to mounting height) like an anvil, swage block, or a lathe (where the original calculation notes came from), one might simply assume the "center of mass" is actually the top of the item, and work with the wider base that such would calculate. Fudge factor/safety factor if you will :)

Hope this helps someone else. 

 

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While the 18 degrees sounds about right for how far to splay the legs out I think the answer is more practical than empirical.  Basically, you want something as stable as possible without the legs sticking out to be a tripping hazard as you move around the anvil.  I would use the horizontal measurement from where the work and hammer head would be on the anvil while working to the tip of my toes and use that to determine how far out to splay the legs.  The legs or the line connecting the legs if there are 3 of them, is the fulcrum on which the anvil and stand will pivot if lateral force is applied.  So, the optimum distance out from the center may vary depending on the mass of the anvil (heavier = harder to move sideways), the geometry of the work space and how you work (if you never hit over the heel while standing at that end of the anvil the legs can extend further in that direction without impeding you), and, frankly, personal preference.

Personally, I use a stump that is a couple inches larger in diameter than the longest dimension of the base of my anvil and it has worked well for years.

"By hammer and hand all arts do stand." 

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If my math’s right, 18 degrees would mean it would take a sideways pressure of about 30% of the anvil’s weight to tip it. Depending on what you plan to bend in the hardy hole, of course. . . .

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Now, just to be clear the 18 degrees is from the center of mass. As well it is the minimum and I think it is relative to "static loads", certainly not accounting for bending forces, or possibly not even for striking force. When I see those tripod farrier stands that I think look so cool, the legs all seem to come together at the extents of the mounting plate. 

I am currently using a cherry log. But the anvil is not attached by anything other than gravity. Nor is it stuck to the ground with anything else. I don't have so much issue with the log dancing, as the anvil itself seems to walk across the top of the log and needs to be re-centered from time to time. 

I have a benchtop vise that I had mounted to a chunk of 2x8 but there was a log I placed that on, and there was no satisfaction in that at all. 

So, I decided I will be needing to build a stand for that vise at least. I thought, while I am at it, make another one for the anvil. Although I have seen ones for farriers that have both the anvil and vise attached to the same stand. So, I am considering that as well. 

Funny thing, while looking for images, I find that they sell aluminum stands for anvils. That struck me as odd in a non-intuitive sort of way. I would never have even considered aluminum. 

I think, pretty soon we will all get to see how bad my mig welding skills are. It will definitely be interesting to see what kind of penetration I can get on 1/8" walled tubing and 1/4" plate steel. :)

 

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For demonstrations I have attached a vise to the hardy hole in my travelling anvil.  It is kind of awkward to work around but it was OK for a demo.  I wouldn't use it that way in the shop.  There are also combination anvils and vises but, IMO, they were more novelty tools that worked, sort of, and weren't as good as a separate anvil and vise.

I think the advantage to the farrier set up is its probability because a farrier is always moving from job to job.  For a shop that stays in one place I think having the vise at a different point of your work triangle of forge, anvil, vise would work better.

I strongly suggest that you anchor your anvil to your stump.  If nothing else, the added mass of the stump adds to the stability of the united unit.  I have a Peter Wright anvil which has steps on the front and back of the base which makes it easy to use a piece of angle iron and 4 lag bolts to attach it to the stump.

"By hammer and hand all arts do stand."

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This is the 66lb Vevor. The base flairs in a way that would be convenient enough to secure with some angle iron or strapping. I just haven't done it. Nor have I taken the advice of just using some silicone to stick it to the log. As I mentioned, the log seems to nicely stay put on my pavers without any assistance. So I may simply add some silicone under the anvil and see if that stays put. 

Currently my vise is a 6" pony bench vise. I attached it to a chunk of 2x8, and for other purposes I would place it on a bench and clamp it down rather than permanently affixing it to anything. It is not my first choice for use in the forge, since I am still keeping my eye out for a post/leg vise, though I haven't found one I can afford yet.

This was intended to replace a smaller 3 or 4" one I use in the shop for holding stuff to cut with a hack saw or cold chisel. Or to hold things while I angle grind them. Interestingly enough, that one is simply attached to a piece of plywood and sits in the top of a rolling tool cart. It is just a bit small, and over the years the jaws don't meet all that well anymore. But it is still fine for what I use it to do. So ultimately whatever I do with the pony will be temporary at least until I can get a reasonable deal on a leg vise.

I do have some 4x4 wood left over from several outdoor projects, and putting together something that could mount that vise is probably going to happen sooner rather than later. Who knows, perhaps a vise on a dedicated stand is something that would make sense in the indoor shop anyway. The only thing, I kind of wish it had a spring of sorts. The runout on the lead screw makes it tough to use with one hand quickly. Perhaps that is a complaint for the Pony Jorgensen folks on their design. :) 

Anyway, I had a local fellow come out to the shop to give me some pointers. He hated that the anvil was on a log, and was quite strong in his suggestion that I make a metal stand or it. I am not one to ignore advise, especially when given face to face. Since I have several pieces of 18"x18"x 1/4" sheet stock laying around from which to cut a mounting plate, it sounded like a simple enough project if I could find something to use as legs. I picked up 10 or 12 of 1/8" walled (maybe 3/16) 1-1/2" tubes that had been miscut to 30 something inches for like $12. I figure if I put an angle on them and slap the magnets against them it would go together pretty fast. Worst case, if they are not heavy enough, I could probably double each one.  I have enough other scrap that a stretcher would be no big deal. All in all it seems like a simple enough project. And it will be good welding practice :) Lord knows I can use the practice.

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Oh GOOD GRIEF! You're really overthinking this and gotten lost in a maze of doesn't matter.

1st. Center of mass is irrelevant unless you plan on hitting your anvil from the side. Forget center of "mass."

The simple rule of building things to stand in a stable manner is. Center of SUPPORT must exceed the center of GRAVITY. PERIOD DOT.

Your anvil is tippier front to back than side to side and you're do heavier work on the heel than but not by a lot so make the FOOT of your stand extend past the ends of horn and heel. Make it's width maybe 2x the anvil foot's width. 

I just bent angle iron flange up and out around my anvil's foot. It wedges to my anvil with my hammer and tong racks. Then came the trick part, getting 3 legs the right length and angle to fit MY working height. Calculate angles, etc? 

Hardly, I drew a chalk line on the floor with another at 90* more or less centered. I propped my anvil more or less centered on the vertical line in the stand frame. Measured from the face to my working height and drew a line 90* across the vertical reference line to represent the ground. 

Then I picked everything up and laid the stock I had on hand for the legs, 3" x 4" rectangular. The anvil frame touching the outside of the tubing, the bottom crossing the ground line just outside the horn and heal length. I use flat white spray paint and scratch through it to make precise marks. 

After cutting the tubing on my cut off saw I'm left with legs tilted longitudinally with the anvil. The leg under the horn is where it needs to be, aligned straight down the center of the anvil. Rotating the two legs under the tail spreads the footprint from = to the anvil's width to approx 2x or a bit more. Tack it up and do any final tweaking so it lays flat, anvil frame at the top being roughly equal distance to the ground all round. 

Tack the spreaders, do any final tweaking and weld it up. 

The only angle calculations are with scissors and pasteboard. Addition and subtraction does it all nicely.

It takes care but requires nothing but basic arithmetic. 

Frosty The Lucky.

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