I need some Help

[Bart Leetch]

I am planning to make a new cabinet to put my old Delta lathe on & am thinking of building a torsion box base for it & filling the box with sand for ballast weight.

Does anyone know how to figure out much sand it would take to to weigh 400 lbs. & how deep that box would have to be if it was 17" x 48"?

I'll put this on heavy duty locking casters that will be mounted on 2x4" steel tubing that will stick out 6" to the front & back for the base for stability.

These measurements match closely what I have now accept there is no place for drawers now & I will have the motor underneath instead of on the left end like it is now.

As you see the set up I have now it is very very stable & weighs about 420 LBS. This is what I hope to have when finished but on wheels with drawers & the motor inside the case under the lathe so I can use the outboard turning capability of this lathe.

The first picture shows the whole lathe. The second picture shows one ot the feet the lathe sets on as well as my free standing tool rest.



Sometime in the future I hope to add a 3 phase motor & VFD.

Any thoughts an this are welcome too.

[Tim A. Mitchell]

Mine is made from 2x8 material, with outside dimensions of about 54 by 23 inches. There is a 3/4 inch ply bottom, and I think it may be supported by 2 by material , laid on its side. I have about 200 lbs of sand in it.

From another standpoint, sand should weigh in at about 90 to 100 pcf.

[Hank Merkle]

I created a torsion box from MDF and used biscuits to align and glued everything together. I have large casters on the bottom of thetorsion box and still notice that it sags a little. now, I made mine 2.5 to 3 feet wide by 6 feet long so in hind site, I probalby shold have realized that it might need more support. Then I created drawers and cubbies for other stuff with an MDF top and finished the surface. Then on top sits two lathes a small turret lathe (5C collet converted to a wood lathe and a central machinery with the head stock removed and replaced with a craftsman veriable speed drive) back to back. (In other words there is a LOT of weight on it.) So I did not add any additional ballest to the torsion box.

All that said, if you want to calculate the cubic feet - take the height times the width times the length and that is the cubic feet then use Tim's number of 90 pounds to 100 pounds and that willl give you the weight.

Example: I create a torsion box 3 feet wide by 4 feet long and 4 inches deep. Four inches is .33 feet (4/12= .33333)

so 3 X 4 X .33 = 3.96 cubic feet X 90 punds per cubic foot = 356.4 pounds

dont forget that you have created a number of "holes" that the sand goes into so we honestly sholld take that away or calculate just the holes, add them together and then multiply by the weight. (you will see that it does make quite a difference)

if I create the same box 3 feet by 4 feet by 4 inches deep (the top and bottom sit on top and bottom of the 4 inch board) and then lets assume we create six boxes wide and eight boxes long with 3/4 lumber with the end pieces that is 9 boards 3/4 " wide along the length (6.75 inches) and and 7 boards 3/4" wide along the width (5.25 inches)

So we can calculate the two different ways 3 feet minus the 5.25 inches and 4 feet minus the 6.75 inches or caclulate the box size and multiply by 48.
3 feet minus 5.25 inches is 2.083 feet and 4 feet minus 6.75 inces is 3.4375 feet (2.083 x 3.4375 X .33 = 2.363 x 90 = 212.67 pounds

So we must almost double our torsion box size to get the same weight (IN SAND) dont forget that the wood weighs something and if you use MDF like I did (IT WEIGHS A LOT!)

Good luck!

Hank Merkle

Mine is made from 2x8 material, with outside dimensions of about 54 by 23 inches. There is a 3/4 inch ply bottom, and I think it may be supported by 2 by material , laid on its side. I have about 200 lbs of sand in it.

From another standpoint, sand should weigh in at about 90 to 100 pcf.

[Bart Leetch]

Thanks everyone. You've given me plenty to think about.