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Single Rope Technique
Chest Ascenders

A4-816, Version A A4-816, Version B A1-811 A4-816 L
A4-816, Version A A4-816, Version B A1-811 A4-816 L

Overview


The numbering for these ascenders may seem confusing - it is. The best explanation that I can offer is that the A1-811 was probably not numbered correctly when I bought mine (1994), and should have been the A4-816.


A4-816, Version A
(#17, 2153)

Front View: Closed Rear View: Closed
Front View: Closed Rear View: Closed
 
Front View: Open for Rigging Rear View: Open for Rigging
Front View: Open for Rigging Rear View: Open for Rigging

Technical Details

I acquired my Single Rope Technique A4-816, Version A from Single Rope Technique in 1989. I acquired another in 2017 as part of Bob Thrun's collection.

The Single Rope Technique A4-816 is 118 mm. tall, 81 mm. wide, 46 mm. thick, and weighs 279 g. The body is extruded aluminum allow painted yellow. The attachment holes are 19 mm. in diameter. The rope channel is 18 mm. wide. The cam radius increases from 42 to 62 mm. over an angle of 45°, giving a 27° cam angle. The tooth pattern is (4.5)^3,(4.3)^2(4). The cam safety is milled from aluminum, anodized, and hinged from the bottom of the cam.

The body behind the cam is stamped "S.R.T.," "AUSTRALIA," and "EQUIP." There is a kangaroo cast into each side of the cam.

Comments

The A4 816 is designed to be a chest ascender for the Frog System. The body is milled from an aluminum extrusion that sets the attachment holes 45 degrees to the plane of the cam motion. This works, but leaves a ridge that sometimes digs into the chest. I find that the Kong-Bonaiti Cam-Clean or the Petzl Croll are somewhat more comfortable. The frame is rugged to the point of overkill, as one expects from an SRT ascender.

The cam is well made and the teeth are nicely formed. The safety doubles as a hold-open catch for the cam.


A4-816, Version B
(#2154)

Front View: Closed Rear View: Closed
Front View: Closed Rear View: Closed
 
Front View: Open for Rigging Rear View: Open for Rigging
Front View: Open for Rigging Rear View: Open for Rigging

Technical Details

I acquired my Single Rope Technique A4-816, Version B in 2017 as part of Bob Thrun's collection.

The Single Rope Technique A4-816, Version B is 115 mm. tall, 80 mm. wide, 43 mm. thick, and weighs 292 g. The rope channel is 18 mm. wide. The cam radius increases from 42 to 62 mm. over an angle of 45°, giving a 27° cam angle. The tooth pattern is (4.5)^3,(4.3)^2(4).

The Single Rope Technique A4-816 is 115 mm. tall, 80 mm. wide, 43 mm. thick, and weighs 292 g. The body is extruded aluminum allow painted yellow. The attachment holes are 19 mm. in diameter. The rope channel is 18 mm. wide. The cam radius increases from 42 to 62 mm. over an angle of 45°, giving a 27° cam angle. The tooth pattern is (4.5)^3,(4.3)^2(4). The cam safety is stamped stainless steel with a turned knob attached, and hinged from the bottom of the cam.

The body behind the cam is stamped "S.R.T.," "AUSTRALIA," and "EQUIP." There is a kangaroo and an up-pointing arrow labeled "UP" cast into each side of the cam.

Comments

I prefer the new safety, but in use, the difference between the two is minor.


A1-811
(#19, 2155)

Front View: Closed Rear View: Closed
Front View: Closed Rear View: Closed
 
Front View: Open for Rigging Rear View: Open for Rigging
Front View: Open for Rigging Rear View: Open for Rigging

Technical Details

I acquired my Single Rope Technique A1 811 from Inner Mountain Outfitters at the 1994 Old Timers Reunion. I acquired another in 2017 as part of Bob Thrun's collection.

The Single Rope Technique A1 811 is 113 mm. tall, 76 mm. wide, 39 mm. thick, and weighs 225 g. The body is milled from an aluminum alloy extrusion and then anodized. The rope channel is 14 mm. wide. The cam radius increases from 43 to 61 mm. over an angle of 41°, giving a 25° cam angle. The tooth pattern is (3.4)^2(5.4)^2(3.4)^2(F). The cam safety is stamped stainless steel with a turned knob attached, and hinged from the bottom of the cam.

The rear of the body is stamped with "AUSTRALIA," "SRT" inside a map of Australia, and "PATENTED." The cam has a raised up-pointing arrow labeled "UP" in raised letters, and "S R T" in raised letters.

Comments

The A1-811 is the "Explorer" series Version of the A4-816. There are minor differences in how the frame is milled, but these make no functional difference that I can see. The cam is slightly different, and the cam safety is made out of a heavy stamping with a turned pin attached, while the A4-816 cam is a cut extrusion.

I consider these two ascenders to be interchangeable. Neither has a clear advantage over the other.


A4-816 L
(#148)

Front View: Closed Rear View: Closed
Front View: Closed Rear View: Closed
 
Front View: Open for Rigging Rear View: Open for Rigging
Front View: Open for Rigging Rear View: Open for Rigging

Technical Details

I acquired my Single Rope Technique A4 816 L from Single Rope Technique in 2000.

The Single Rope Technique A4 816 L is 116 mm. tall, 80 mm. wide, 43 mm. thick, and weighs 292 g. The rope channel is 18 mm. wide. The cam radius increases from 41 to 61 mm. over an angle of 41°, giving a 29° cam angle. The tooth pattern is (3.4)^2(5.4)^2(3.4)^2(F). The cam safety is stamped stainless steel with a turned knob attached, and hinged from the bottom of the cam.

The rear of the body is stamped with "S.R.T.," "AUSTRALIA, "EQUIP." and "19925201." The cam has a raised up-pointing arrow labeled "UP" in raised letters, and "S R T" in raised letters.

Comments

The SRT catalog lists this as the A4-816 R, but the receipt listed it as an A4-816 L. I think that the latter makes more sense, but it doesn't really matter what you call it - its a larger Version of the A1-811 (now called the A4-811 R, or is it L?) that can handle 8 to 16 mm. ropes for the "bigger is better" crowd.