Force needed to open door
Force needed to open door
(OP)
Given:
174" ID Autoclave Side Hinged Door w/ accessories
Weight: 30,000 lbs (just picture it like opening a door in your house, only larger and heavier!)
5" bore hydraulic cylinder to open door
Thrust bearing holding weight of door
Pump pressure available 1500 psi
The cylinder is capable of moving the entire weight of the door w/ the appropriate pressure supplied (max 3000 psi) but how do I account for the fact that the cylinder is just pulling the door open, not lifting the door?
The door hinge bracketry sits on a thrust bearing to take the 30,000 load. How do I go about calculating the force needed to open the door? Obviously the cylinder doesn't have to move the full weight as it is resting on the thrust bearing. What percentage of the weight does the cylinder have to overcome to open the door?
Probably something simple for many of you fresh out of school but this old brain needs some help. Thanks.
174" ID Autoclave Side Hinged Door w/ accessories
Weight: 30,000 lbs (just picture it like opening a door in your house, only larger and heavier!)
5" bore hydraulic cylinder to open door
Thrust bearing holding weight of door
Pump pressure available 1500 psi
The cylinder is capable of moving the entire weight of the door w/ the appropriate pressure supplied (max 3000 psi) but how do I account for the fact that the cylinder is just pulling the door open, not lifting the door?
The door hinge bracketry sits on a thrust bearing to take the 30,000 load. How do I go about calculating the force needed to open the door? Obviously the cylinder doesn't have to move the full weight as it is resting on the thrust bearing. What percentage of the weight does the cylinder have to overcome to open the door?
Probably something simple for many of you fresh out of school but this old brain needs some help. Thanks.
Brian
[url=http://www.wabfab.org]WabFab[/url]





RE: Force needed to open door
M_friction = Bearing mean radius X door weight X bearing friction coefficient
Now:
F_cylinder = M_friction / vertical distance of cylinder pull point from the door hinges
The bearing dimensions and coefficient of friction is given in the bearing manufacturer catalog.
RE: Force needed to open door
If the door is hung on vertical hinge pins, (vertical axis of rotation) and swings horizontal then
israelkk is correct but probably meant:
F_cylinder = M_friction/HORIZONTAL distance of cylinder point from the door hinges.
Maybe the door is opened and closed by hand pumped hydraulics, but if you are using powered hydraulics please read on. The problem here is what happens when you stop the swinging door either on the closure seal or the swing open stop. Be sure and use a cushion cylinder, cushion stops and/or bi-directional flow control elements in your hydraulic circuit. Otherwise, you will be swinging a 15 ton hammer.
RE: Force needed to open door
RE: Force needed to open door
I was on the right track in my thinking, but I couldn't find any relevant formulas in the books I have.
Everything is set up for the door to open nice and smooth and it works...just have to "prove" it on paper, you know how it goes.
Thanks again.
Brian
RE: Force needed to open door
This is the correct way otherwise you may end up with a too strong (expensive etc.) actuator or a too weak actuator where you will have to redesign the whole system (expensive etc.)
This is why engineers go to engineering school where they actually teach you the basics from where you can do all the needed calculations.
RE: Force needed to open door
Brian
RE: Force needed to open door
It's not as simple as will it work. The real question is; how well will it work, and is it the most affordable efficient method.
RE: Force needed to open door
With basic open/close valves, a hydraulic cylinder is essentially a constant force machine. The geometry and kinematics of the connection of the cylinder to the door and a rigid mount may alter the force vs. degree of opening profile that the door sees.
Constant force means constant acceleration. The inertial forces associated with a 30,000 pound door are liekly not negligible, as ccw pointed out earlier.
RE: Force needed to open door
You will have to watch your mounting configuration for the cylinder the multiplication of forces could impact the system performance.
RE: Force needed to open door
I guess my point is that you need to have something to dissipate the inertia. Built in cushions in cylinder, a bumper, separate hydraulic shocks or slow down ramp.
I would suggest separately mounted bumpers or shocks if the cylinder piston can bottom out at full extension since the angle usually gets ugly there. The further you can limit travel under 90 degrees the better.
Barry1961
RE: Force needed to open door