Weaver Construction Log

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In June 1952, the British magazine Model Maker commenced a series of articles titled A 1 c.c. C.I. Engine. This series described a simple compression ignition engine (aka "diesel") for home construction. The design was called the "Weaver/Ransom" after the designer and draftsman, respectively. Model Maker was then part of the Model Engineer, Aeromodeller, etc stable but alas, ceased publication sometime in the early 60's. The engine however is still remembered in MICE circles, being often referred to simply as "The Weaver".

This little engine was built and described by Mr Ransom to a design developed over several years by Arthur Weaver for use in rail car racing. Now tether cars are not exactly my cup of tea, but the thought of a 1cc diesel powered tether car somehow seems very "gentlemanly" and very "British". The engine was fully described over three issues to be fully fabricated, that is, no castings were employed. While the original plans and instructions are now very hard to come by, they are probably still subject of copyright held by a succession of owners of the venerable names (currently, this is Nexus Special Interest Publishing), so I'll respect that right and post no scans of the text here.

Weaver's design was published with a flywheel, but I'd seen an example of this engine doing a good impression of a Mills .75 at our local free flight field—that is, starting on the first flip and swinging a large prop at whatever rpm the flier wanted; from a powerful two-stroke to a comfortable, under-compressed, rich, low-rpm four cycle. The builder was Russell Watson-Will. Russell built two Weavers. His second one is the red headed engine at the head of this page.

You may have seen the Weaver Triplets shot before in color on the back cover of SIC, or black and white on the rear cover of MEW. At the time I first met Russell (1994), I was just starting into model engineering and he kindly sent me a copy of the article (he has a magnificent library) and the above photo, saying I should build one. Finally, I did, but was unable to stop at one...

The links at the bottom of this page will take you through the construction of my Weavers, embodying my (unfortunately) usual education-through-error approach. As part of this process, the original plans were redrawn in MBI format, correcting a couple of errors, adding some parts for airplane use and changing the timing to make the inlet and exhaust more generous. They also incorporate a few other minor detail changes to simplify construction as advised by Russell.

This caused an outbreak of Weaver Fever in the MBIs, resulting in examples from Roger Schroeder and Ken Croft. Roger wanted to see how it would look as originally designed, complete with flywheel. If you look closely, you can see that Roger's crankcase is a casting. Ken's example is the one without the flywheel, finished appropriately in British Racing Green. Ken also used one of Roger's crankcase castings, but machined it all over to replicate the original "hacked from the solid" look. He also improved the inlet timing and reports 10,500 rpm on a 7x4 prop. The last Weaver was built by Mr Ken-ichi Tsuzuki (Japan, if you could not guess). If you examine each of the engines closely, you'll see that we all interpreted the head shape slightly differently, as well.


From this index page, you can go directly to any of the Weaver Construction Log building sessions. Each page links to each other in sequence, and to this page.

Cylinder and Head
Venturi and Needle Valve Assembly
Conrods and Crankshafts
Piston and Contra-Piston
Final Assembly and Test Report

I've not bothered with any pseudo-legal voodoo mumble before, but as the hit rate on this site climbs, so does my pulse rate. Somewhere out there is a turkey, so I better state here and now that I am a professional computer scientist, not a professional machinist! If you follow any of my techniques you are probably as gullible as I am. What I'm actually documenting here are all the ways I've found to positively screw up, frequently in a very un-safe manner. Finally, amazed at the amount of time it now takes to backup this site, I have to state the all material herein is Copyright (C) me. If you want to reproduce it elsewhere, please ask first. Only way I'll say no is if you're getting paid for it and I'm not!


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