Transitional Fitting Fabrication 110203a Flashcards
When a transitional fittings used?
- to change aspect ration
- to move duct for architectural reasons
Why is the use of transitional fittings avoided?
- time (layout skills)
- money (cost of fitting)
List 3 joints used to join transitional fittings to each other
- Slip and drive connection
- CP (standing drive) connection
- Proprietary connection
Why must a slip and drive joint be adjusted on transitional fittings?
The 1” S-cleat cannot be at an angle to the next fitting
What must be done to the net pattern for each slip and drive joint connection?
Reduce length of the net pattern by 1”
What must be done to the net pattern for each proprietary connection?
Reduce the length of the net pattern by the length of the proprietary connection attachment pocket.
What must be developed first when developing the cheeks for curved runner pattern?
The flat view of pattern
To brake a transitional brake on an elbow, the amount of angle is measured with a protractor?
False
What mathematical concept is used when building transitions from plan view?
Pythagorean Theorem
(теорема Пифагора)
The stretchout length of a heel runner should be calculated or measured?
Calculated
When developing the pattern on piece of metal that has been pre-cut to length, the opening sizes and offsets are placed where?
On the NET pattern line
When developing the piece for a 2 side flat transition, what should determine which sloped side gets to pocket allowances?
Why?
The side that has the most amount of slope.
Less angle for transfer of angle notch
When assembling a transitional fitting, what should be done before assembly?
- Form seam and edges
- Open Pittsburgh Lock
Why would blocking be used when assembling a transitional fitting with raw edges?
To keep the assembly edge flat and not damage the fitting
Why would the throat and heel be fastened to one cheek instead of fastening both cheeks to either the throat or the heel?
The throat or heel can help support the cheek during assembly
What is the best aspect ratio in a square duct?
1:1
What is the maximum allowable aspect ratio in a square duct?
4:1
FOB stands for?
Flat on Back
FOT stands for?
Flat on Top
ON stands for?
On centre
What does the Raw edge connection require?
The Raw edge connection requires that no allowance is added to the completed pattern.
From witch side of the duct drive side should be made?
From the shortest duck side always.
What does the Standing drive (CP) connection require?
Standing drive (CP) connection, requires two allowances to be added to the raw edge of the duct and both allowances are folded or broken to the outside of the duct or fitting
What is a hammerlock (tap-in), typically used for?
A hammerlock, also called a tap-in, is typically used to join a smaller rectangular piece of duct to a larger piece of duct.
Which joint requires an adjustment to the net pattern for the pieces to line up?
One of the joints that do need an adjustment to the net pattern, if the pieces are to line up, is a proprietary connection.
What do most prints or job specifications state about ductwork construction?
SMACNA
What is the important thing to remember when developing the patterns for Y-branch?
The net pattern opening locations must stay in place
