The Logging A–Frame

A-Frame

An A-frame (now dismantled) on the Vancouver Island coast. (Photograph from MacFarlane collection.)

The logging A–Frame was a structure in general use from 1920 to about 1970. Unlike land-based systems, which yarded logs into a central landing and transported them to water by road, rail, chute or cable, A–frame loggers used a yarder floating on the water to pull logs down to it. The A-frame yarder was usually mounted on a large raft of floating logs and the lines were threaded through blocks hung at the apex of two log spars hung in an "A" configuration. In some installations the A–frame was mounted on an abutment right next to the water.

The impact of dropping the logs into the water was an issue at A–frame operations, as it resulted in increased bark loss and damage to the shoreline in shallow receiving waters. The lost bark accumulated accumulated on the bottom and resulted in the physical smothering of marine organisms and habitats. Water quality was degraded through the decomposition of accumulated woody debris, causing reduced dissolved oxygen levels and the formation of toxins such as hydrogen sulfide. Repeated impacts associated with dropping logs in shallow waters, resulted in physical damage to shoreline sediments, marine organisms and habitats.

When the train arrived in the mill area, there was usually a mill pond to hold the logs. To get the logs into the pond a log dump consisting of a small trestle and some type of yarding device to unload the logs. The most popular and easiest to use was the A–frame and donkey unloader. The donkey engine controlled a cable which was routed up to the top of the A–frame and then down to the log dump trestle. When a log car was positioned next to the A–frame, the cable was sent under the logs and connected to the lower portion of the log dump on the pond side. The cable was then pulled taut by the donkey engine and the logs were forced off the cars into the pond. Most log dumps had a ramp or fence to assist the logs into the pond and prevent kickbacks.


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