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Unread 05-02-2007, 14:23
eugenebrooks eugenebrooks is offline
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Re: Banebot 56mm gearbox - double D - RELOADED

Quote:
Originally Posted by jskene View Post
With reference to Dr. Brooks' table in the above post of various steel properties, what degree of hardness do we need in the gearbox plate? This will help us decide which metal to start with.

We have access to a waterjet and a computerized furnace, and hope to make some parts. Hopefully we can make several.
Reading from Mil Spec MIL-H-6875H

4340 1550F soak for half hour, oil quench, 850F temper, tensile is 200-220 ksi
4130 1600F soak for half hour, oil quench, 850F temper, tensile is 160-170 ksi
4140 1600F soak for half hour, oil quench, 850F temper, tensile is 180-200 ksi

Seal the parts in a stainless bag, flushed with argon, that is easily cut with shears while glowing so you can drop the parts in the oil quickly without them cooling off in air before the dunk. Tempering cooler will increase strength, but as you approach 700F the parts become brittle. These strengths are way above the strength of the factory shaft. You should make both parts, and use a square hole, to get the full benefit of the improved materials/geometry.

Last edited by eugenebrooks : 05-02-2007 at 15:39.