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The Shadow Air Muscle is a simple yet powerful device for providing a pulling force. It behaves in a very similar way to a biological muscle. When actuated with a supply of compressed air, it contracts by up to 37% of its original length. The force it provides decreases as it contracts, and the first few percent of the contraction is very powerful indeed.

Properties

The Air Muscle behaves in a different manner to the pneumatic cylinder or other actuator. As the Air Muscle contracts under constant pressure, pulling force produced between the endpoints decreases. The maximum possible force at a given pressure is obtained when the Air Muscle is pulled out as far as possible. If the Air Muscle is not taut, then it will not yield its full force.

At a constant pressure, the curve of the Force against Length is shown on the right. Note that, if the Air Muscle is not fully stretched at the start of the movement, initial force will be lost and the Air Muscle will under perform by a significant margin. The relationship between pressure and force is linear at constant extensions. This allows the movement distance to be set by regulating the pressure in the system. Characteristics of pressure, length and force are given below. These measurements are typical of Air Muscles of the specified size.

Percentage Contraction of Active Length for 6mm Air Muscle

6mm Air Muscle	LOAD
PRESSURE	0.5Kg	1Kg	2Kg	3.2Kg	4.6Kg
0 Bar	N/A	3%	2%	2%	1%
2 Bar	12%	10%	7%	5%	3%
4 Bar		20%	20%	17%	11%

Percentage Contraction of Active Length for 20mm Air Muscle

20mm Air Muscle	LOAD
PRESSURE	0.5Kg	5Kg	10Kg	15Kg	20Kg	25Kg
0 Bar	N/A	8%	6%	2%	1%	0%
2 Bar	35%	29%	23%	17%	12%	10%
4 Bar		33%	29%	25%	23%	20%

Percentage Contraction of Active Length for 30mm Air Muscle

30mm Air Muscle	LOAD
PRESSURE	0.5Kg	10Kg	20Kg	35Kg	50Kg	70Kg
0 Bar	N/A	2%	1%	0%	0%	0%
2 Bar	35%	33%	30%	27%	24%	21%
4 Bar		35%	33%	31%	29%	27%

Operational Requirements

The Air Muscle is a pneumatic actuator and so the following guidelines must be adhered to:

• Shadow Air Muscles should generally never be operated above 60 psi (4 Bar)
• When the Air Muscle is not loaded, it should not be inflated above 30 psi (2 Bar)

Over-inflation will cause the life of the Air Muscle to be significantly reduced, and may cause the assembly to burst. The Air Muscle is not rated for use outside the 0-50 Celsius temperature range. Air supplied to the Air Muscle should be clean and oil-free. It is not possible to make a general prediction about the life of the Air Muscle in use; lifespan is dependent on operating conditions and ambient conditions. We therefore do not make any life expectancy statement. (We perform internal tests under uniform criteria to ascertain product consistency with expectations).

Fixtures and Fittings

The 6 and 20mm Air Muscles are supplied with an attached air line of 4mm diameter (Outside) and have looped ends, for easy attachment to hooks or pegs. The 30 mm Air Muscle has an attached air line of 6mm diameter (Outside). The 30mm muscle are supplied as standard with M6 studding. It is possible to supply them with eyebolts if required, or other fittings according to customer's requirements.

• For ordering information, please see our ordering page or use the add to cart buttons below
• Please contact The Shadow Robot Company to discuss your particular application.