On 07/21/2020 02:54 PM, John Dammeyer wrote:
Hi Jon,
How did you come up with the constant 0.0318?
Long story. There's complicated formula to compute it from
the helix angle of the screw.
Too much fiddling around. So, if you had a drum with a
string wrapped around it that advanced the
axis as much as the leadscrew, it should be equivalent
(ignoring friction and diameter of the string). So, how big
would such a drum be? The circumference should be equal to
the pitch of the screw, in this case 0.2". So, what is the
radius of a circle with a 0.2" circumference? 2 Pi R =
Circumf. so
R = circumf./2 Pi so, 0.2 / (2 Pi) = 0.0318
Now, if you apply 10 in-Lb torque to a 5 TPI leadscrew, you
get 10 / 0.0318 = 314 pounds force.
" So, that 100 oz-in motor (0.52 lb-ft) would
produce 0.52/0.0318 = 16.35 lbs of linear force (neglecting
friction)."
And, this was wrong due to a inch/foot mixup!
0.52 lb-ft is 6.24 in-Lb, and the linear force would be 196 Lbs.
And how did you work out the 5G?
"So, if your machine has a 200 Lb table, and the leadscrew
were to produce 1000 Lbs linear force,
it would accelerate at 5 G?
If you dropped the table on your toe (don't do this at home,
kids!) it would accelerate at 1 G.
if you push on the table with a force equal to 5 times it's
weight, that will accelerate at 5 G.
Jon
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