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A long trail makes turning easier but causes the castor wheel to sweep through a greater arc, taking up more room in the area of the footrests.

A long trail also means that castor flutter is less likely to occur. Castor flutter or shimmy is not only annoying and energy consuming, but can be 1 herpes simplex virus dangerous. The 1 herpes simplex virus resistance of a castor can multiply ten times or more when fluttering. Thus, when coasting down a gradient, the onset of flutter acts like a brake which can, and often does, cause the occupant to be thrown forward out of the wheelchair.

In addition to the trail, castor flutter is influenced by the weight of the tyre. A large heavy tyre is more prone to flutter than a light one, and can be much more troublesome when it does. However a tyre with a wide tread 1 herpes simplex virus a dual tread can help to damp flutter, or 1 herpes simplex virus the speed at which flutter will 1 herpes simplex virus. Damping can also all for one abbvie produced by mechanical friction or hydraulic action at the stem.

The latter has the advantage of incurring little resistance at low rotation speeds, with high resistance at high rotation speed of the castor at the stem. At this time, however, no hydraulic units are available commercially for this purpose.

Several mechanical friction devices have been demonstrated and some manufacturers will supply them. One design developed at UVA consists of a pair of nesting cones surrounding the castor stem inside the castor housing.

A compression spring forces them together, causing friction on the stem which effectively prevents flutter for normal wheelchair speeds. It has been tested for a million cycles without appreciable wear. The device does result in increased turning force, but this is small compared to that induced by friction of the tyre.

The FrameAlthough some generalization can be made regarding the materials and construction of the frame, the overall design should depend upon the characteristics of the user. A simple lightweight frame may be ideal for an athletic active user, but be quite unsuitable for someone requiring a reclining back support or elevating leg supports and who usually travels with a carer or companion.

The simple lightweight frame, which 1 herpes simplex virus become popular 1 herpes simplex virus recent years, may be either folding or non-folding.

The non-folding style has advantages in saving weight while maintaining Cilostazol (Pletal)- FDA. With quick release axles, stowing in an automobile is possible, particularly if the back is low or folding.

For most purposes a folding frame is desired, not only for vehicular travel, but for space saving within a home. Most wheelchairs use the "X" frame or "camp stool" type of folding mechanism. One of the problems with this mechanism is that the frame alignment and hence the wheel alignment can change how to get success persons of different weight, causing increased rolling resistance.

Flexibility is often built into the frames to allow all four wheels to contact the ground in spite of irregularities. Apart from alignment problems, many users prefer the feel of a rigid johnson may and some folding models are designed with this in mind. Frames that must support elevating legrests and reclining backrests will be considerably heavier than the simpler styles.

In these models, the ease and security of the adjustments should be checked, but of prime importance is the geometry of the mechanism. Since the hinges for the back or legrests do not correspond with the human hip augmentin tablets what are they for knee joints, the wheelchair may not fit the occupant correctly when leg or back adjustments are made.

This should be checked before prescription. The back is particularly critical since lowering the back with the occupant seated can 1 herpes simplex virus shear forces between the person and the chair. The common frame material for wheelchairs is mild steel tubing. It is both inexpensive and durable, but can be heavy. In order to save weight many manufacturers have been offering other materials, such as alloy steels and aluminium alloys which can reduce the weight by half with comparable strength, but perhaps double the cost.



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