Scrapper 29 (oz13718)

About this Plan

Scrapper 29. Model aero engine.

CAD drawings by Ron Chernich. Article by Tim Dannels.

Quote: "The Scrapper .29 by Tim Dannels.

The Scrapper engine was manufactured by The Woodbridge Manufacturing Co in late 1944 and early 1945. They were built in Manchester CT, and like many of the model engines in the period when World War II was winding down, they were first built sort of on the sly - in this case in the early morning hours of the 3rd shift at the local Pratt & Whitney Aircraft Company.

The original Scrapper .29's apparently ran quite well according to the reports of owners. Most were well made and had good performance. Production figures are not known, 2000 engines is an approximation, but there seem to be quite a few in collections.

The crankcase and front shaft housing were rough sand castings with considerable machining done to clean them up. The rest of the parts are machined from bar. The cylinder is blind bore. The piston originally used featured a ball and socket arrangement somewhat like the modern Cox engines except that the socket was a separate piece, peened into the top of the piston. The Motor Boys version utlitzes a standard wrist pin and rod arrangement. A poppet valve in the intake served for fuel induction, somewhat like the M&M engine.

Further development of the Scrapper by Woodbridge Manufacturing was in the form of an engine called the Super Scrapper. This engine was advertised quite extensively, but very few were actually produced beyond the prototype and experimental stages. Woodbridge was a small company and could not sell enough engines to pay the bills. Names of the designer of the Scrapper and Super Scrapper are not known.

As a side note, the individuals who were building the Scrapper and then promoted the Super Scrapper tried again, a few months later in 1946, to market a model engine. This one was called the 'Bobcat' and was a .42 cu in displacement engine. It was marketed under the company name of Stenmoor Manufacturing Co. The overall design was similar to the Super Scrapper. It had dual exhaust stacks, timer and needle valve located in the rear and a blind bore cylinder. Once more, only a few experimental and prototype engines were built. There just was not, as in the case of Woodbridge, enough money behind the company to get itself established. The glut of model engines in the immediate post-war period left no room for small speculators.

The Original Scrapper, when properly adjusted and tuned was a good performer, but sales and advertising could not match the big names like Ohlsson & Rice, McCoy, Forster, Delong and others. Like so many others, they just became entries in a historical listing."

Direct submission to Outerzone.

Note this plan (and article) is an extract from the MBI (Motor Boys International) Model Engine Plan Book, 2nd Edition. This was originally published through the MEN site run by Ron Chernich, see http://www.modelenginenews.org/. Also see Mary's page on RCLibrary https://rclibrary.co.uk/title_details.asp?ID=2122 which hosts a copy of the book as submitted from MBI by Ken Croft, in accordance with Ron Chernich's wish that from 2013 onwards the book should be available, freely, to everyone as a PDF download.

Supplementary file notes

Article.

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