Tri-pod (3-legged) leg angles

[Brandon Ade]

I could use some thoughts/advice/experience surrounding the suggested angle on legs placed on a 3-legged metal anvil stand. I like to get my thoughts and measurements down in a simple CAD drawing before fab so attached are a number of photos to get my point across.

I am questioning the benefit of a 3-legged metal stand vs. a simple T-shaped stand (see photo). In my mind the simple T-stand is easier in the design, cutting and fabrication and offers less obstruction.

Regardless of the type, the question of leg placement becomes important. I included top-down photos of each proposed stand to get an idea of where the legs rest in relation to the anvil.

On a tri-pod, what is an acceptable angle for the legs to ensure stability? Here I have mocked up 3 examples showing different angles (from vertical) on the legs, using 11 degrees, 15 degrees, or a combination of 11/15. The single top-down photo of the tri-pod is of the 11/15 combo.

Discovering this "best" angle led me to wondering why not go with a simple T-stand? Though again, the placement of the feet becomes a concern so as to prevent tipping and the T-stand raises concerns about stress fractures given a single 4" tube as the connection point (here I am assuming A36 4"x3/8" round tube and 4"x3/8" sq. tube). 

I would enjoy hearing what others have to say on the matter of leg placement, degrees from vertical, clearance issues, structural integrity, and the like. Cheers!

[ThomasPowers]

T promotes sway in use.  However there is NO one best stand.  What works well for one smith may have another continually tripping over the feet.  You need to figure out what works best for you and that generally making it and using it.  All the skull sweat in the world doesn't work as well as experimental proof!

Now a big part of things is how large your anvil will be and how you plan to use it.  I think I missed where you stated that absolutely necessary information. (The stand makes a lot more difference with my 91# anvil compared to my 469# anvil.)

[JHCC]

Much would depend on the rigidity of the central post on the T-base stand. Tripods do have the advantage of a triangulated structure that minimizes the movement of any individual element.

[anvil]

You are overthinking the problem and not looking at your cad work.

The tee for an anvil stand needs a quick ctl/alt/delete. All stress will be at the joint of the plate and the vertical, not to mention enhancing vibration and "ring.

At least your other drawing attempts to distribute the weight of the anvil over three points instead of all weight and force basically focused on one point.

 

 

[Frosty]

Lose the T, it's a non-starter. There is one primary factor that determines stability, the base of support must equal or exceed the center of gravity. For an anvil stand you need to consider leverage and twisting moments as well. Pick a tripod with feet outside the anvil in the plan view. As noted by other smiths the more vertical the legs the more rigid the stand. Rigidity is a factor to consider AFTER you take care of the base of support.

There is one suggestion for you basic design though. Put the two leg end of the stand under the hardy hole as it's the end of the anvil that will see the most tilting and twisting forces. Think scrolling forks and a scrolling wrench. Hmmm?

The T stand is a worse trip hazard than the legs for the same foot print and the post will flex sacrificing rigidity. It's maybe a good concept for a side table but is a really poor anvil stand. It doesn't even have a little shelf under it to lay your tools to cool while the steel is heating. 

Frosty The Lucky.

[Brandon Ade]

TP: the anvil is 267#. Face height is 35-1/2".

I agree with all comments on why the T-stand needs to disappear.

Frosty: thank you for the wise hardy hole suggestion.

Back to my original post, what angle is appropriate for the tripod legs? My thought that led me to 11/15 degrees was simply to put the feet at a position outside the main body of the anvil. Is common sense the only math necessary here? Has anyone used an angle on a tripod that didn't work?

[ThomasPowers]

Large anvil: should not tip it easily as long as the legs extend past the line of a box drawn to encase the anvil.  However if you will be doing a lot of heavy work; a wider base increases stability. If you do a lot of light ornamental work where you may be "dancing" around the anvil with the stock then tripping hazard as well as tipping hazard should be considered.

If you are unsure; mock it up in wood and try it and decide which you like better!

[Frosty]

The angle isn't important so long as the feet are outside the necessary base of support, Thomas described a easy non mathematical method of determining. 

I've made two tripod anvil stands and drew them on graph paper to determine the base of support and the footprint I liked. Then I cut a piece of cardboard for a template to angle the vise on my cutoff band saw. The real tricky part was getting the height right without using any of that icky math so I used my framing square to mark the next cut position and set the stop. Cut the first angle on the end of the stick, move it up to the stop clamp, turn it on RrrRrrRrr and I go off to work on the angle iron frame until CLANG. Move the tubing up clamp RrrRrrRrr go back to fitting the frame to the anvil foot. CLANG and repeat. 

Tack welded the legs to the frame and double checked for the correct height a bit lower than I'd like but good enough and welded it up. Took about 1 hr. for this old retired: welder, fabricator, driller operator. Why mention driller? Drills in the field REQUIRE a lot of welding or pieces fall on you. 

I have no idea what the angle is and it's only close to the same on the other tripod. You CAN tip the Soderfors over if you try but the Trenton will slide before it tips even on asphalt.  

Frosty The Lucky.

[Brandon Ade]

I wanted to share a grateful update on what I finally ended up fabricating and how it went. The final design took on somewhat of a hybrid of the 3-footed tripod and the T-stand, but I can't take credit for this design, it was a shameless rip-off from examples at the school. Previously this design was not possible as I only had access to 4" tube, so I owe an immense thank you to Haley at the ACC shop for allowing me access to some hefty scrap material. Ended up with 1" base plate, 6"/8" round tubes for legs, 8"x6"/8"x4" square tube for supports, and 1/2" plate for the feet. 

After having so much larger stock available the design could change. It all started comically as this chalk board insanity (feel free to laugh, it's absurd):

After getting the material home it was a lot of cutting and grinding to get the pieces to fit. 

  

Finally they were ready for dry-fitting and all cavities were filled with sand to add an extra 150# in weight. Designing and cutting took a few weeks, welding less than a day...

    

Caulk laid down on base and 3/8" chain with 1/2" hex bolts used to pinch down:

 

With a coat of black engine enamel I had laying around the stand is finally finished and a happy anvil is ready to roar to life in it's new home:

  

The design maintains the benefit of a triangulated 3-feet footprint which keeps it ultra stable and the extra width of the feet really add an extra dimension of stability. Maybe my next stand will be a tri-pod to compare.

Designed the face height to be 34". Had a huge goof up in fabrication and ended up at 34-1/32"...oops.

Anvil weight is 267#. Stand ~300#.

I didn't put much thought into the finished look (as in I got lazy and just wanted to get it operational), I just used the black paint I had on hand. I wasn't sure how I felt about the zinc plated "gold" chain, but I ended up liking how the gold and silver of the anvil play together, kinda pops and makes me imagine dwarves mining and forging precious metals deep below some mountain somewhere. It makes me laugh because it also reminds me of Mr. T, so maybe I just found it's new name. It sure doesn't have that rustic antique historic look, but I think it will get the job done.

Thanks for the earlier input, the best take aways: go big and don't worry so much about the angles.

[arkie]

Nice fab and welding work, but I think you are going to be stumbling and stumping your toes on the large footprint (no pun) of those pieces of pipe, not to mention a lot of leaning over the anvil to avoid the pipes...your back will talk to you. 

[ThomasPowers]

Having it on a plate rather than anything directly touching the ground seems like a loss of efficiency issue too.

[Frosty]

My thought too. Looks nice though.

Frosty The Lucky.

[Brandon Ade]

Arkie, no issue with access. I can get my hips all the way to the face and get as near as I like without bending over. I've worked on similar stands without it bothering my back, even on lower face heights. That's the reason for the large single leg placed at the heel, it allows getting very close.

TP, the average of four 1" hardened ball bearing tests was 86%. When the anvil was directly on the ground (concrete) I was getting 90%. So at least for that test I agree I have lost 4%. Something I will just have to accept.

[ThomasPowers]

Thanks for the details; It was very interesting to have an actual difference reported. It's your setup and so you can do with it as you wish---just don't make a zucchini stand---that would be right out!