By Julius de Waal - part one

Richard Trevithick’s dredging engine is one of the iconic engines from the earliest days of steam.

Trevithick realized that his innovative high pressure steam engines could be put to many different uses. In early 1806, Trevithick successfully submitted proposals to the lighthouse organization, Trinity House, for dredging aggregate for ships’ ballast, using steam power.

He mounted a high pressure engine and a side chain of buckets on the 21.3m long gun brig, Blazer, loaned to him by Trinity House and which he later bought for £300. The six horse power steam engine was built at Hazeldine & Co in Bridgnorth and had a 200mm diameter cylinder with a 910mm stroke.

The dredger worked in September and October on Barking Shelf in the River Thames. It was a technical success. However, the engine couldn't raise aggregate at the rate Trinity House required and, after further trials in December, Trevithick built a larger engine.

The following year he mounted the  larger  engine in ex-navy vessel, Plymouth, which went to work on the Thames at Limehouse. He  sold both ships to contractor Hughes, Bough & Mills who re-modelled the Plymouth, installing a bucket chain on both sides and fitted a 16 horse power engine by Matthew Murray.

Julius’ drawings are in metric based on the original by Tom Walshaw (Tubal Cain). Castings are available for the original, although fabrication should be possible. Click on drawing to download - for personal use only.

See part two here.