On choosing the type of drives for industrial swing gates.
On choosing the type of drives for industrial swing gates
These are not private gates that are opened 2-5 times a day. And the dimensions are by no means small. And throwing away the drive (or forcing the manager of the company — the reseller to do it, and at his own expense) after six months of work is not really something you want to do…
There are only three main questions for making a smart choice:
— how long will the drive work before it fails due to wear resistance
— will the drive have enough power to (at the wind speed that occurs in your region) overcome the wind load on the gate leaf
— at what frost will the drive you have chosen stop opening the gate
In order not to waste energy on research yourself, you can choose what the two largest Russian companies specializing in security systems choose: FSUE SNPO Eleron (Moscow) and CeSIS NIKIRET — a division of PO Start (Penza). After all, they have hundreds of people who are engaged in research, testing and certification. Moreover, each industry in ITS Certification Center requires them to confirm the declared characteristics.
And today I want to try to explain what can happen (and does happen) in case of an incorrect choice of drive for a specific gate (let's take a gate 3 m high and 2.5 m wide) with a gust of wind of 15 m/sec.
Note:
1. The gates chosen are by no means the largest
2. The calculations are given here in case the gate leaf is completely protected and not transparent to the wind
3. The wind speed is by no means enormous, but is quite acceptable for almost every region (we will not take the wind speed such as, for example, in Novorossiysk, where it can be 60 m/sec).
4. Let's assume that at a wind speed of 15 M/sec, the wind pressure force on 1 sq. meter of the panel will be 15 kg/sq. meter (you can calculate more accurately yourself).
So, the wind pressure force on the leaf will be: 15 x 3 x 2.5 = 117 kg.
If the drive is fixed with one end to the wall near the canopies (that is, at a distance of 1.25 m from the center of the wind load), and with the other end to the gate leaf, then the moment of the drive forces (so that it overcomes the wind pressure) must be greater than (117 kg x 1.25 m) 146 kg x M. Or (if converted to Newtons) 1460 N x M.
Let me assure you (without giving any calculations) that the moment of force of the strongest electromechanical linear Italian drive does not exceed 40 kgf x m. If you do not believe me, then take a dynamometer (or a regular spring balance for weighing), measure the holding force on the edge of the sash and multiply by the width of the sash.
F (in kilograms) x B (in meters) = M (in kilogram-meters).
And if you don't have a gate with an electric drive at hand, then request data on the drive you are interested in: — longitudinal thrust force (in Newtons), distance between mounting points (in meters) and distance from the longitudinal axis of the drive to the plane of the sash (in meters). And based on the simplest calculation from a school physics textbook, you will get the result (in N x M).
Now a little about linear drives:
— the strongest linear electromechanical ones have a traction force of 3000 Newton (300 kg). (There are, however, linear hydraulic ones with a traction force of 700 kg, but based on their geometric parameters they develop approximately the same moment of force, and the force of tearing the sash off the wall even with their nominal value is already 700 kg. And I will not calculate the breaking force (so as not to scare you) for this drive).
So, with a torque of 40 kg x M developed by the drive, the traction force (the force of tearing the sash off the wall by the drive) will be 300 kg. And what will be the tearing force if the wind with a moment of 146 kg x M acts in the opposite direction on the sash moved by the drive?
Let's calculate:
(146 kg x M plus 40 kg x M) x 300 kg: 40 kg x M = 1400 kg, that is, almost 5 times more than the force of the drive itself.
What are the risks of such overloads:
1. if the gate hinges did not withstand the tear-off force of 1.4 tons and came off, then the drive itself will be distorted
2. if your hinges are excellent, then the tensile (or compressive) force on the drive will also be 1.4 tons (with a calculated drive load of 300 kilograms).
We assume that the designers have introduced some kind of safety factor. … but not five times… There will be a bending of the steel screw, and an attempt to break the bracket (connecting the gate leaf with the drive nut), and an attempt to tear the drive lugs off the wall… But that's not all. After all, the screw has a thread angle of about 45 degrees, that is, it begins to transmit counter-rotation to the gearbox located between the engine and the screw. And the moment of force of this counter-rotation is several times greater than the moment of force for which the gearbox is designed. … especially since not all the parts there are metal, but also plastic.
It is preferable to draw a conclusion not from your own bitter experience. And those directors who entrust the choice of the drive to engineers, and the purchase to financiers, do not then contact other companies to replace the drives with more reliable ones.
That is precisely why the documentation from the manufacturer shows lattice gates in the drawings. And the dimensions of the gates are given (in accordance with their weight) only to show what force of inertia of the leaf this drive can overcome. And there is nothing about wind loads, or wear resistance when exceeding the parameters, or anything else — there is nothing there. That is, clear data necessary for entering into the passport data. And there is no need to make any claims against them.
And our Russian dealers (I am not talking about the competent, respectable ones) can often only move their lips, calculating the profit from the resale of equipment that you obviously do not need…
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Director of «Trud» — Nikolai Ivanovich
didenko@azov.donpac.ru