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Austin Insulators Inc.
suppliers of RF insulators and transformers since 1933

   
       

 

Products:  
Self Supporting  
Base Insulator  

Description 
Specifications 
Notes 

 

Austin Base Insulators for Self Supporting Radio Towers and Masts

   Austin Base Insulators for Self Supporting Radio Towers use ceramic in compression to bear the compression load and utilize continuous wound preloaded links to resist the individual leg uplift.
   In these bases, the resistance to shear load is derived from the compressive load and preload applied to the base.
   In addition to the standard range, designs can be provided for custom applications with extremely high electrical and mechanical working loads as well as high seismic load conditions. Special exact fit replacement bases, as substitutes for insulators by other manufacturers, are also available.

  • Oil filled to eliminate Radio Frequency loss due to water condensation on internal surfaces. Additional benefits are elimination of 'hot spots' and easy detection of porcelain failure.
  • Smooth insulator finish minimizes leakage and flashover due to surface contamination.
  • Items listed are types recommended for new construction. Previously listed Austin types are available for replacement purposes.
  • Insulators for higher mechanical and electrical loads are available. Please call, write, or e-mail stating your requirements.
  • All insulators are supplied with adjustable lightning gap.
   
         
       
  Specifications    
 
Insulator Type Number of Elements Maximum Recommended Working Download
(note 1)
Maximum Recommended Working Uplift
(note 1)
Permissible Shear Load at Rated Uplift
(note 2)
Preload 1 minute Drip Wet Withstand at 100kHz;
Voltages KV RMS
Standard Rainshield High Voltage Rainshield
*A-4950
A-4950-C
1 25,000 lb
11,340 kg
17,500 lb
7,938 kg
680 lb
308 kg
25,000 lb
11,340 kg
32 44
*A-4938
A-4938-C
1 50,000 lb
22,700 kg
35,000 lb
15,900 kg
1,850 lb
840 kg
50,000 lb
22,700 kg
22 30
*A-4881
A-4881-C
1 75,000 lb
34,000 kg
52,500 lb
23,800 kg
2,400 lb
1,090 kg
75,000 lb
34,000 kg
71 99
*A-4729
A-4729-C
1 100,000 lb
45,400 kg
70,000 lb
31,800 kg
3,600 lb
1,630 kg
100,000 lb
45,400 kg
71 99
*A-3167
A-3167-C
1 150,000 lb
68,000 kg
105,000 lb
47,600 kg
6,300 lb
2,860 kg
150,000 lb
68,000 kg
71 99
*A-2812
A-2812-C
3 250,000 lb
113,400 kg
196,000 lb
88,900 kg
10,000 lb
4,540 kg
280,000 lb
127,000 kg
71 99
*A-2913
A-2913-C
3 375,000 lb
170,100 kg
280,000 lb
127,000 kg
15,500 lb
7,030 kg
400,000 lb
181,400 kg
71 99
*A-3782
A-3782-C
5 600,000 lb
272,200 kg
455,000 lb
206,400 kg
25,000 lb
11,340 kg
650,000 lb
294,800 kg
71 99
*A-4049
A-4049-C
6 900,000 lb
408,000 kg
600,000 lb
272,200 kg
42,000 lb
19,000 kg
900,000 lb
408,000 kg
71 99
* Identical insulator except it has a round base.
   
 

 

Notes:
  1. Allows for a minimum Safety Factor of 3.
  2. The permissible shearloads stated above assume that the insulators are worked at their stated recommended maximum working uplifts. If your required working uplift is lower than that given in the table above, a higher shearload is permissible. The following formula will enable the new maximum permissible shearload to be calculated.
     
    Equation used in the calculation of shearload

    Example: For insulator type A-4881-C and a required working uplift of only 30,000 lb.,
     

    The 4,800 lb. represents the permissible shearload of this insulator when the working uplift requirement is 30,000 lb.
  3. The drip wet figures above are a minimum achieved with the insulator standing directly on the ground plane. Higher voltages can be expected with the insulator installed on a pier.
  4. All insulators can be fitted with a high voltage rainshield as an optional accessory to improve the voltage rating.
   
       
 

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