Seeking advice concerning metal thickness for a tree digging spade

Click For Summary

Discussion Overview

The discussion revolves around the appropriate thickness of plate steel for a custom tree digging spade intended for transplanting trees. Participants explore design considerations, material strength, and operational challenges related to the spade's construction and use.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • AntonK proposes using either 1/8" or 3/16" thick 1018 mild steel for the spade, expressing concern about the stress from levering and potential obstacles like rocks.
  • Some participants suggest that extending the handle to the tip of the blade would enhance strength, particularly for leveraging purposes.
  • There is a recommendation for using 3/16" thickness due to the likelihood of greater stress in practical use than anticipated.
  • One participant advises adding a strap across the outside flanges of the blade to resist flattening, indicating a concern for structural integrity.
  • Another participant questions whether multiple spades will be made for surrounding the tree, suggesting a strategy for easier removal of the root ball.
  • Concerns are raised about the adequacy of the design for manual operation, with a note that hydraulic power would necessitate heavier materials.

Areas of Agreement / Disagreement

Participants generally agree on the need for a thicker plate and the extension of the handle for strength, but there is no consensus on the exact thickness or design modifications. The discussion remains unresolved regarding the optimal specifications for the spade.

Contextual Notes

Participants express varying assumptions about the operational stresses and potential modifications to the spade's design, indicating that the effectiveness of the proposed solutions may depend on specific conditions and use cases.

AntonK
Messages
2
Reaction score
0
Hello to all,

I have a question concerning what thickness of plate steel to use for a tree spade that I'm going to have made to help with transplanting some trees. The intent is to have a spade that cuts 1/4 of a cone that is 24" in diameter and 18" deep. After cutting the tree's root ball, separate cuts in the ground on one side of the root ball will be made to offer a bit of a slope to make easier the levering/dragging of the root ball out of it's original position so that it can be moved to a new location. I hope to attach a picture of what I'm proposing so that you can get an idea of the configuration. The blade portion of the spade is to be either 1/8" or 3/16" thick 1018 mild steel (I think hot rolled). It is to be a total of 21.625" tall and 19.75" wide at the top. It is also to have two bends that are about 25 degrees each segmenting the blade into three somewhat equal triangles. To the center triangle, there is to be welded a 1" square bar that will serve as the handle and as the means of transferring the force of a 17 lb, metal fence post driver to the blade. The soil in this area is about 110 lbs/cu. ft. and the volume of the root ball will be about 1.5 cu. ft.. Add to the weight of the soil a tree's weight of about 40 lbs and I estimate this spade will have to support about 205 lbs. But it's the levering and the driving (possibly into the occasional rock) that concerns me the most. The question is: is it better to use 1/8" plate or 3/16", or something altogether different?

Thank you for any input -- even if it isn't scientific.

AntonK
 

Attachments

  • Tree spade drawings.png
    Tree spade drawings.png
    12.7 KB · Views: 738
  • 3D view of tree spade.png
    3D view of tree spade.png
    5.8 KB · Views: 564
Engineering news on Phys.org
The spade would be stronger if the post can be extended to the tip, rather than attached half way.
This is especially so as the plan is to use the spade as a pry bar, to lever obstacles.
I would certainly go for the 3/16th thickness, as the actual stress in the field is almost always greater than the expected amount. People are hard on equipment.
 
I certainly agree with the comments above regarding extending the handle further down the blade and also with the use of heavier plate.

1) I would suggest a strap across the outside flanges of the blade at the top end of the blade, to help resist flattening.

2) Are you planning to make several of these, so that you can surround the tree, leaving each in place while you pry on another, with a helper inserting deeper those that become free in the process?

3) What you show here looks adequate only for manual operation. If you should decide to arrange hydraulic power for the shovels, much heavier material will be required.
 
Thanks for all the input. Those are excellent suggestions. To OldEngr63, I'm only having one made and it will be a manual operation that involves surrounding the tree with four "cuts" to create a root ball. Then, on one side of the ball, cutting a wedge of ground away so as to create a bit of a ramp. Inserting the spade on that side of the ball, I hope to tilt the ball out of place so that I can pry/drag it out of the hole and to its new planting place. I know it sounds like a lot of effort, but readily available systems that don't require a bobcat start around $2K. If this were a business proposition, I'd make the investment, but it's a personal project so I'm trying to keep the cost down.

Thanks again for all the input,
AntonK
 

Similar threads

Graduate Motion of rotating and sliding metal bar for robot combat
  • · Replies 1 ·
Replies
1
Views
2K
Torque created around offset wheel
  • · Replies 8 ·
Replies
8
Views
3K
Earthing & Lightening Protection for a Home on a Mountain Top
  • · Replies 9 ·
Replies
9
Views
10K