EDITOR NOTE: This is a reprint of a series entitled Just the Tip authored by Thomas Brobst. His ‘make-do-with-what-you-got’ and ingenuity makes for interesting reading and maybe help a poor soul out of a perplexing repair. See if you agree with me this is fun reading.
Just the Tip
Tip #12
Good day, avid readers! Ready for the snow, I trust? After an unseasonably mild winter now we’re bracing for a big Nor’easter! And after a week of spring like weather, no less! It’s enough to make an old British car owner crazy!
This last weekend, however, as if to brace us for the coming storm, was really cold and I, for once, have actually taken advantage of it! Since my MGA is all set for the driving season I have redirected my efforts to my old BMW. Years ago I had fabricated an engine/strut brace for it. One part of it was made from ¾” OD 4130 chrome-moly steel tubing with two 45° bends. I had made the bends with a cheap Harbor-Freight hydraulic pipe bender. See the problem yet? No, it’s not the H/F tool….that did exactly what it claimed. The problem is that I bent tubing in a pipe bender! Why should this be a problem? It’s because tubing is what it says….¾”OD tubing has an outer diameter of.750in. 3/4in pipe, on the other hand, has an outer diameter of 1.050in. WTF!? The inner diameter isn’t ¾” either...except possibly for Schedule 40….but only close). Pipe sizes are nominal and based on ancient, arcane practices that only plumbers, pipe-fitters and alchemists are privy to. The only way to get a .750in dimension on 3/4in pipe is if you cut it to that length!
Original Part with kinked bends Close-up of kinked bend (sorry about the focus)
So why did I buy the wrong bender? Because good quality tubing benders are expensive and this one was only 100 bucks including dies for six sizes of pipe! (With the good tubing benders you need to buy the dies separately.) Plus, I was thinking that maybe the H/F label was a misnomer…..who the heck bends pipe anyway? Isn’t that what pipe elbows are for? So, not for the first time, and probably not the last, I exercised the rule of False Economy by buying the wrong tool because it was cheap. Although the pipe bender did bend my tubing the quality of the bends was embarrassingly bad (read kinked)….hence, this article about how to make it right!
I had heard about old school ways to bend tubing by packing the tube with sand in order to keep it from kinking. Another way was to fill it with water and freeze it. But my tubing was a bit too large for my freezer. Hmmm, how expensive are big freezers…? What? Wait! The weather forecast is calling for sub-freezing temperatures for the weekend! So, I cramped a rubber stopper in one end of my tube, filled it with a few bazillion molecules of H2O and propped it upright outside for the night.
Next day, sure enough, it was frozen solid. I stuck in the pipe bender, gave it the appropriate number of pumps, and lo and behold ….I achieved a perfect bend! Who woulda thought? Now, one word of caution. The frozen “pipe-sicle” melts pretty quickly, especially during bending. The externally applied pressure adds a certain amount of heat that helps expedite the solid-to-liquid phase change (aka melting process). So, have buckets and rags handy.
(Continued on page 15)
|
January 2023
