8/7/2019 calculo de espirales

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You have D (outside flight diameter), d (inside flight diameter), P (pitch of flight).

So consider that b is the result of (D-d)/2.

Now developed the outside diameter,A = square root of [(PI*D)^2+(P)^2].

Then the inside developed diamater,B = square root of [(PI*d)^2+(P)^2].- Value of PI = 3,1415926...

So the developed inside radius of the flight will be:

r = R-b => b=R-r; b/r=(r-R)/R - 1 step

R/r=A/B; (R-r)/r= (A-B)/B - 2 step

consider that R is the developed outise radius.

so we have:

b/r=(A-B)/B

then...

r=(B*b)/(A-B)

that is valid for cylindrical screw flights made with plates.

enjoy

EJEMPLO

It's a screw of 9" OD, 9" pitch and a tube of 2"1/2 sch 40. (2.875) inside of it.

That screw is called a auger , it is also named the ARCHIMEDES SCREW.It's easy to calc by simple geometry.

First step = get the pipe perimeter

2.875 * pi = 8.7493281 "Think you develope the pipe surface in plain after you mark where the fligth meets the pipe.

So you will have a rectangular triangle whose sides are the pitch = 9" and thedeveloped perimeter = 2.875 * pi = 8.7493281 "and it's hypotenuse is Ih = Square root ( 9^2 + 8.7493281^2)= 12.55192704

This measure is the depeloved perimeter of the internal diameter of the "washer" so Ih/pi = IDin this case is 3.995402467By the same method you can get the outside diameter the 9 in OD is 28.27433388the pitch is the same 9 so the OH =29.67217479and the OD is =9.444946579

so you need to cut a "washer" 9.445" OD and 3.99"

cut it and weld one after one and then strech it over the pipe

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8/7/2019 calculo de espirales

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Hola, creo que tienes todas las expresiones para obtener el desarrollo plano dela hlice, te comento eso si, que hay un error en una de las expresiones, especficamente la del paso 1 o Step1, pues dice:

r = R-b => b=R-r; b/r=(r-R)/R - 1 step

R/r=A/B; (R-r)/r= (A-B)/B - 2 step

y debera decir : r = R-b => b=R-r; b/r=(R-r)/r - 1 step

efectivamente sera bueno verificar las expresiones con un modelo en 3D de la hlicey despus medir el largo de la curva exterior e interior de la hlice.

Para efectos de construir o fabricar un transportador de tornillo, conozco un procedimiento, pero es tan amateur que no creo que sea lo que busques si lo que deseas es obtener algo similar a la helice que entrega la maquina que indicas.

Respecto de esa maquina del video, no creo que tenga un nombre tan especial, elprincipio es el mismo que usa una mquina que hace resortes, que fuerza a pasar elalambre por cavidades o guas para que salga con forma espiral, hay un video en youtube tambin. Saludos!