The Air Muscle is an extraordinary actuator that is small, light, simple and 'friendly'. It is soft, has no stiction, is easily controllable and exceptionally powerful.

Advantages of the Air Muscle

Lightweight	Air Muscles weigh as little as 10 grammes - particularly useful for weight-critical applications.
Lower Cost	Air Muscles are cheaper to buy and install than other actuators and pneumatic cylinders.
Smooth	Air Muscles have no 'stiction' and have an immediate response. This results in smooth and natural movement.
Flexible	Air Muscles can be operated when twisted axially, bent round a corner, and need no precise aligning.
Powerful	Air Muscles produce an incredible force especially when fully stretched.
Damped	Air Muscles are self-dampening when contracting (speed of motion tends to zero), and their flexible material makes them inherently cushioned when extending.
Compliant	Being a soft actuator, Air Muscles systems are inherently compliant.

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, they contract by up to 40% of its original length. The force it provides decreases as it contracts, and the first few percent of the contraction is very powerful indeed.

The simplest use of an Air Muscle is to move a lever. One muscle will pull the lever in one direction, and a spring can return it. Two muscles will allow the lever to be pulled in either direction, with considerable force. Because the muscle contracts over a known distance, it can be used to provide a safe movement: there is no need to ensure that the lever is not going to be rotated beyond its end-stop, because the muscle will only move the lever to its set up angle.

Air Muscle Construction

The Air Muscle consists of a rubber tube covered in tough plastic netting which shortens in length like a human muscle when inflated with compressed air at low pressure. An Air Muscle has a power-to-weight ratio as high as 400:1, vastly outperforming both pneumatic cylinders and DC motors that can attain a ratio of only about 16:1. It has been in continuous development for advanced robotics work by Shadow since 1982, and is now available for use in a variety of applications as a powerful, lightweight actuator. Air Muscles are normally operated using compressed air in the 0-60psi (0-4 bar) range.

The Core of an Air Muscle is a rubber tube....

....wrapped in a tough plastic weave....

....which shortens in a scissor action when pulled out, just like a Chinese finger puzzle. As the rubber tube fills with air it is forced to expand.

A small Air Muscle, at just 6mm in diameter, has the strength, speed and fine stroke of a finger muscle in a human hand. An Air Muscle 30mm in diameter is capable of lifting more than 70 Kg at a pressure of only four bar, while a large muscle (50mm) has enough power to pull down a brick wall.

Most of the robots built by the Shadow Project are driven by Air muscles, and looking at these will provide much insight on the possible uses of the Air Muscle.

Shadow Air Muscle Range

Thumbnails / Products	Braid Diameter	Length	Air fitting size	Pull at 3.5bar	Maximum Pull
	6mm	150mm  (Stretched)	4mm	3 kg	7kg
	20mm	210mm  (Stretched)	4mm	12 kg	20kg
	30mm	290mm  (Stretched)	6mm	35 kg	70kg
Please note: Muscle lengths differing from the list below can also be supplied.

Notes:

Length measurements fully stretched: are between the attachment points when the muscle is fully stretched and therefore include the muscle ends which do not contract.

Operating restrictions: when not under load, muscles should not be inflated beyond 2 bar. When under load, muscle life may be reduced if pressures greater than 4 bar are used.

Air Muscles are not designed, intended, authorised or warranted for use in life support applications, devices or other critical applications.

Fully stretched 20mm Air Muscle

Fully stretched 30mm Air Muscle

A 30mm Air Muscle Header

The Shadow Starter Kit

Shadow Air Muscle Starter Kit

Quantity   @ £21.00 Add to Cart View Cart

One standard 15cm (stretched) air muscle. Three-way-valve for controlling the air flow. Bottle cap adapter for attaching an air reservoir. Fizzy drinks bottle to be used as the air reservoir. Footpump adapter for connecting a car footpump to the 3mm air line. Tee piece, in case you want to connect one footpump to more than one system. Two releasable nylon cable ties, to attach the muscle to your device. Plus a length of 3mm air line which can be cut and push-fitted into the other components. NB You will need to supply a foot pump for charging the reservoir.