Head-mounted binoculars

Project  / Project number: CB 1715  /  Status:

0

The challenge

Following an aneurysm some years previously, the client has near-total paralysis of her right hand. She is a keen member of a bird-watching group, but had been finding it impossible to hold her binoculars steady with her left hand only. She approached Remap with the idea of mounting binoculars on a bicycle helmet or similar device. She wanted to be able, using her left hand only, to swivel the binoculars up from her spectacles to walk short distances, and to remove them altogether with a quick-release clip for walking between bird-watching sites.

The solution

Over a period of about ten months the project evolved through several stages and the client purchased much lighter binoculars, weighing about 330g in contrast to her old ones which weighed 780g.

A cheap builder’s face shield was purchased, and the shield and brow-guard were removed to leave the plastic head mounting, weighing only 90g and with an adjusting knob at the back which could be operated with one hand.

.

.

Initially an experimental frame was constructed of aluminium angle and fitted with binoculars for testing the concept. The binoculars swiveled upwards around the face shield’s pivot axis just above the user’s ears, so that they came down almost vertically to the user’s spectacles and pushed down on them, which was unsatisfactory. This showed firstly that the pivot axis needed to be further forward and higher, so that the binoculars would approach the user’s spectacles almost horizontally, and secondly that, to avoid neck pain, the device would need a counterweight behind the head.

.

.

The next attempt involved a horizontal main pivot axis 90mm above the sight line and vertically above the front surface of the user’s spectacles, so that the binoculars would approach the spectacles horizontally when lowered. This axis was supported from the head mounting by a structure made of 3mm acrylic sheet, with provision for adjusting the fore-and-aft position of the main pivot. The binoculars were fitted with a clamp made from bent Meccano strips, attaching them to an acrylic tongue 80mm long and 3 x 20mm in section. This fitted into a support arm pivoted on the main axis, the pivot pin being a piece of 1.9mm bicycle spoke. The tongue was retained inside the arm’s slot by a release catch with a spring at its pivot. Tension springs helped to lift the support arm with the binoculars to the raised position.

Testing of this Mark 1 version showed some problems. The support arm, when without the binoculars attached, flew up so fast that it broke the main structure. With the binoculars attached it was difficult to bring to the viewing position. The Mark 2 version had a redesigned structure with the same main pivot position but different spring geometry. It performed better, but could not hold the binoculars in the raised position when the user walked. A spring catch was therefore added to hold the arm in the raised position, and the spring geometry was further amended to produce the successful Mark 3 version.

This final version of the device weighs about 520g, including the 160g lead counterweight, so the device with the new binoculars, at 850g in total, is not much heavier than the client’s old binoculars (780g). Like an animal produced by Darwinian evolution, the Mark 3 device inherits some sub-optimal features from its forebears. A future Mark 4 device, if it were ever built, could be somewhat neater and lighter while retaining the successful geometry of Mark 3.

The benefit

The client can now join fellow bird-watchers on trips, moving easily between hides or other sites and then bringing her binoculars to her eyes, adjusting them with her left hand alone, and then watching birds in comfort without the use of either hand. She is delighted and has taken the device to the USA on a prolonged sojourn there.

Leave a Reply

Your email address will not be published. Required fields are marked *