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Ideas for light weight drive shafts made with Trib-Joins

APPLICATION NOTE: 9

Thin-wall Trib-joins™ made by swaging with a high rate method such as magnetic pulse forming will avoid spring back and is highly beneficial when assembling drive-shafts. Trib-joins behave like very high friction couplings and if these joins are made slightly weaker in torsion than the individual parts, the joins will momentarily yield upon overload and then recover their full strength. This is a highly unusual yet desirable overload safety feature for transmission shafts. The beauty of the Trib method is that very thin drawn or welded steel tube can be used taking advantage of its greater strength and superior fatigue behaviour over aluminium. Furthermore, thanks to the nature of the Trib join, coupling is distributed over relatively large areas avoiding stress raisers due to narrow band welds. For competition purposes the Trib process can be used to join aluminium tube to steel knuckles, done without the need for forming mechanical interlocks, and done more conveniently than impact welding because the joins are made with significantly lower impact velocities and power.

Trib-joins offer many ways of reducing weight and costs in manufacturing. For instance small front wheel drive automobiles often use solid drive shafts of between 25 and 30mm diameter. A pair of these can weigh upwards of 3 kilo. The strength of a of a 25mm solid shaft can be obtained at one third of its weight by using a 50mm diameter tube with a 1.1mm wall thickness and the tube can be economically joined by Trib-joins onto splined stubs for conventional coupling to the constant velocity joins - a potential saving of 2 kilo/vehicle !.

In a design as shown below the thin wall hollow steel shaft may be damped and stiffened sufficiently to survive stone damage by filling with light weight ridged foam.

In the cross section diagram the thin wall tube and stub shafts are sized to about 900Nm maximum torque. The inner Trib joins connecting the stub shafts are sized to about 800Nm. And the outer joins to about 1000Nm.

Thus in the event of a transient overload the stub shaft joins will momentarily yield - BUT DO NOT BREAK OR LOOSE ANY STRENGTH - thanks to the unique ability of Trib-joins to absorb transient energy.

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By using this Trib join construction it would be possible to simply incorporate the constant velocity join satellite ball cage into the tube end thus reversing the arrangement normally employed. This potentially offers further weight saving.

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The TribTech name derives from  "tribos" - Greek for 'rubbing'. 'TribTech' is a trade name used by Ball Burnishing Machine Tools Ltd. Registered Office 12 Brookmans Av. Hatfield, Herts. AL9 7QJ. United Kingdom;  Company Reg. No. 1408807, VAT Reg. No. 421 6210 04; a knowledge based company that develops, patents and licenses technology based on aspects of  tribology, the science of surfaces. All rights reserved by Ball Burnishing Machine Tools Ltd. Last modified: 29th Sept 2016 copyright 1999/2016. The information and data provided herein should be considered generally representative for the tools and technologies described. In all cases users should carefully evaluate the tools and technologies to determine their suitability for a particular purpose. Be aware this site uses cookies, your continued use implies you accept these.