| No
specific legislation applies but the use of products complying with
BS A.U. 24a 1989, which specifies the pin/hook and eye dimensions,
together with throat clearances of the jaw to ensure adequate articulation,
is strongly recommended. |
| The
eyes normally used in the U.K. have an internal diameter of 30,
40, or 50mm and are used with either a towing jaw, a combination
jaw/towball or occasionally a hook. There is also the 76mm Nato
eye used by the Armed Forces, usually with a military style pintle
hook. |
| The
British eyeshafts have a round or toroidal section eye and are used
with a parallel type pin with sufficient clearance in the eye to
permit the correct sequence of towing on the pin and braking on
the jaw. If the pin is too large or the clearance between the jaw
and pin too great, then both towing and braking loads will be put
onto the pin. |
| A
40mm DIN eye, commonly used in Europe, has a hardened steel bush
fitted to the internal bore and is designed to be used with a special
pin that has a bulbous or reinforced section, around which the eye
can pivot. Because of this it is ESSENTIAL that a 40mm DIN eye is
NOT used with a British style parallel pin, as the sharp edges of
the bush will cause accelerated wear of the pin, with possible serious
results. The incorrect combination can also often prevent full articulation
of the eye within the jaw, leading to rapid coupling wear and possible
chassis damage. |
| If
a trailer of less than 3500kg gross weight is to be towed by an
H.G.V. it is recommended that an eye is used in preference to a
50mm ball coupling. In this way the overrun coupling is better able
to withstand the additional forces imposed on it by the harder suspension
and possible extra overhang behind the rear wheels on the towing
vehicle. |
|
|
|
