Force Required to Open Door

[GianlucaTempesta]

thread1083-438231
@hydtools I found this formula,
F = (I*(95 - theta)*pi)/(180*r*t*(20-t))
Could you explain how did you get it
Thank you in advance.
Kind Regards

 

[hydtools]

To accelerate: M*t=I*w or M=I*alpha w is angular velocity assume constant acceleration alpha, M is constant for time 0<t<=t1.
M = F*r M*t = F*r*t = I*w F = I*w/(r*t)
For time 0 to t1, w = w1 F = I*w1/(r*t1)

Given: total time = 20 secs, total angle = 95 deg
t1 + t2 = 20
theta1 + theta2 = 95

For time t1 to t2: assume w is constant = w1 = theta2/t2 = (95-theta1)/(20-t1)
Substitute w1 into equation for F. Multiply theta by pi/180 to get degrees in terms of radians.


Ted

 

[GianlucaTempesta]

Hello Ted,
thank you so much for your reply.
So I have this situation.
Weight of door 1400 Kg
Dimensions 2500x2500 mm
Door is hinged on a vertical side
Hinges are working on ball bearings.
Opening angle from 0° to 95°
t1 = 2 sec
t2 = 30 sec
teta 1 = 1 deg
teta 2 = 94 deg

I'm going to open and close this door with an electric actuator, I found that with a lever of 130 mm I need a force of 650 N.
Would you be so kind to double check this calculation?

Thanks

 

[hydtools]

Show your calculation.

Ted

 

[GianlucaTempesta]

Weight(kg) 1400



D (mm) 390
D1(mm) 880
Lb(mm) 1270
L(mm) 2500
s(mm) 90

Rv (N) 3433.5
Rh (N) 6867
R (N) 7677.539401


C.attr 0.01
Mattr (Nmm) 174421.8
F (N) 69.76872

teta 95
teta transient 1

stroke actuator 200
vel min 7

t totale 30.57142857
t constant (s) 28.57142857
t transient (s) 2

I (kg*m^2) 2916.666667

lever of actuator (m) 0.128

F actuator (N) 653.8827402

lever for manual opening (m) 2.5

F manual (N) 33.4787963

 

[zeusfaber]

CAUTION: I see the OP's discipline is Marine/Ocean.

Can I ask where this door is fitted?

The calculations above rely on a tacit assumption that the hinge axis is perfectly vertical and that the whole assembly is fixed in space. Those assumptions were perfectly valid in the original thread.

If those assumptions are not valid (if for instance you still need to open a heavy watertight door on a ship that has taken on a list, or restrain one on a ship that is rolling heavily) then more calculations are required and the required forces increase very quickly.

A.

 

[GianlucaTempesta]

Hello,
this door in fitted on a civil construction!
Kind Regards

 

[hydtools]

GianlucaTempesta
I calculate F = 667.57 N
Close enough

Ted

 

[GianlucaTempesta]

Thank you so much!!!