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Motorcycle Headlamp Filament

A fifty (yes, 50) year old Harley Davidson motorcycle (antique) was being driven near the city limits of a rural town. A pickup truck reportedly pulled in front of the motorcycle and a collision ensued. The truck driver claimed that, although it was required by law and it was dusk, the motorcycle headlamp was not operating. The motorcycle headlamp is shown in Photograph A.

Overall view of Harley Davidson headlight.
Photograph A Fifty year old Harley Davidson motorcycle headlight.

Visual examination of the headlamp indicated that the headlamp bulb located at the base of the headlight was still intact. That is, the headlamp bulb, located at the base of the headlight was still intact. A close-up view of the headlamp bulb is shown in Photograph B.

Headlamp of Harley Davidson light bulb.
Photograph B Headlamp bulb with curved and distorted filament.

In Photograph B a portion of the headlamp filament is noted at the base of the headlamp bulb. An arrow denotes the curved filament. A new headlamp bulb and filament are shown in Photograph C.

New Headlamp bulb and filament.
Photograph C New headlamp filament, straight and undeformed.

It is clearly evident that the new headlamp filament is straight and un-deformed. An arrow in Photograph C denotes the straight, un-deformed filament.

When a headlamp is illuminated, the filament will have a temperature of over 5000°F. If the velocity of the filament is suddenly changed, i.e., by an impact, the filament will deform (bend) before breaking. If the filament is cold, no filament deformation will be noted.

A report highlighting the hot filament deformation was issued and the matter was resolved.

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J.E.I. Metallurgical, Inc.

5514 Harbor Town
Dallas, Texas 75287

Phone: (972) 934-0493
Fax: (469) 737-3938
Email: r.c.jerner@metallurgist.com

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