Check Tube Deflection¶

Deflection Calculation

It is now possible to check the deflection of a roller tube when an order detail line is entered.
There is a new parameter for this in Blind Details > Blind Types called ‘Check Tube Deflection’, which defaults to false.

If this parameter is set to true, and if the calculated deflection is > admissible deflection, a message will appear.

The formula for this is as follows.

MI for Solid Round Beams = (pi * (OD4 - ID4)) / 64
Deflection = (length3 * force) / (3 * E * MI)
Bending Stress = (force * length) / (MI / (0.5 * height))
Where,
MI = Moment of Inertia
E = Modulas of Elasticity in psi
If bending stress exceeds the materials yield strength it will be permanently deformed and not return to its original shape.

Example:
Calculate the deflection of a simple round tube.
Length (Inches) = 15
Diameter (Inches) = 5
Wall Thickness (Inches) = 0.2
Force (Pounds) = 5
Material = Steel

Solution:
Apply Formula:
MI for Solid Round Beams = (pi * (OD4 - ID4)) / 64
Deflection = (length3 * force) / (3 * E * MI)
Bending Stress = (force * length) / (MI / (0.5 * height))
Deflection = 0.000006111549814728781 (Inches)
Bending Stress = 6.111549814728781 (PSI)

The ‘Admissible Deflection’ and ‘Moment Of Inertia’ are held in the stock record.
There is a new field called ‘Modulas Of Elasticity’ which is held in the Characteristics tab.

The force is calculated as the weight of the blind, so we now calculate this.
The weight is calculated for each bill of material record and stored there, and then also held in the detail line and also in the order total (there is a display field for it in the Totals tab).
It is displayed in the BOM form and is a column choice in ‘Window Blind Amend’.

The weight is calculated by taking the quantity calculated in the BOM record and multiplying it by the ‘Specific Weight’ field that is in the stock record.

Similar to dev 4748, the ‘admissable deflection’ and ‘moment of inertia’ are taken from the relevant chosen tube option.
If the calculated deflection > admissible deflection, a warning message will appear saying
‘The calculated deflection has exceeded the admissible deflection for this tube. Please select a bigger tube’.

Torque Calculation

It is now possible to calculate whether a motor or mechanism is powerful enough to lift a blind and give a warning message if it is not.
This takes place immediately after the functionality that takes place for ‘Check Tube Deflection’.

There is a new field in the blind type record called ‘Check Torque’ which defaults to false.
There are two new fields held in the stock record called ‘Torque (Nm) and ‘Friction %’.

The calculation for torque is (expressed in lb) is:

(Weight of blind * (Tube diameter / 2)) * (1 + friction %)

Expressed in Nm (Newton metres) 1 newton meters, or 0.737562149277 foot pounds

If the ‘Check Torque’ flag is switched on and there is not enough torque in the selected option, a message will appear asking the user to enter an appropriate motor or mechanism.

Order Processing > Orders > Tube Deflection

If ‘Check Tube Deflection’ = true, when an order detail line is entered, it now display what the tube deflection is in the BOM form.
If the tube deflection is too high, the warning message now displays the formula and the calculation being applied in the tube deflection calculation.