Pie crust tanks
Engineer and Velocette enthusiast Rob Drury contacted with the following email regarding Norton (and other pie crust tanks). I’d referred to the ‘extra-large’ Norton factorymade pie crust tank fitted to George Tucker’s 1929 Brooklands 200-mile racing Norton outfit depicted.
Rob writes: “In the period pie crust tanks were used, the fuel and oil tanks were made in tinplate and soldered. A soldered joint needs a reasonable surface area for the solder to be drawn into by capillary action. Typically, this means that at least one flange will be formed at a simple corner and solder drawn in between the surfaces.
“Tinsmiths generally used interlocking joints to hold the material together – grooved seams, peened joints or knocked up joints and then made into liquid tight vessels with solder. The body of many ‘flat’ tanks was made in one piece with a grooved seam running the length of either the base, or more typically the top. The grooved seam was frequently inverted to make the outside face flat.
Nortons will have adopted all of the customary practices for making a soldered tank, but soldered additional angles around the base and other stressed points to make them more resistant to cracking, particularly on competition motorcycles.
“The wavy edges of the angles were not decorative but simply a way of letting the angle be shaped around curves as the tinsmith soldered them in place. The reduced height in the bottom of the curve lowered resistance to stretch or compression at that point and allowed the angle to conform to the shape of the tank, with light hand dressing.
“I served my time as a sheet metal worker in a shop that still did quite a lot of tin smithing. It was very good work for teaching accuracy and neatness. Apprentices were kept at this work until they were regarded as being fit to learn other skills.”
Thank you, Rob, for your insight into making pie crust tanks.
We as a family were lucky to be able to draw on the welding skills of European Trials Champion, the late Don Smith and gained another skill appropriate to tank repair. Over 25 years ago, we presented Don with a Gold Star tank from which an errant soul (previous owner) had cut out an oblong, near postcard size section from the base. Not only was this lost, but the past owner hadn’t removed the two dents he’d accessed by removing the base section.
Having learned a little panel beating when helping repair a crashed Austin Healey Sprite and then a VW Beetle, I removed dents with panel beating hammers and dollies and then made a replacement section, which I thought a pretty neat, tight fit. DR surveyed the welding job for milliseconds before asking ‘which ‘xxxxxx’ cut out the panel.’ “Previous owner” Peter and I stated firmly. Okay, said Don, who ground a little more material from two edges of my panel to make a loose fit, then welded it home. He then instructed: “If you need to do this, this is how,” and he demonstrated on an old unwanted tank:
* Mark out panel
* Cut three sides Heat remaining marked line to cherry red with welding torch and used fine nosed pliers bend panel outwards Complete panel beating or other task from inside tank Heat remaining panel ‘marked line’ with welding torch and ease back in position Weld three cut seams