Banebot 56mm gearbox - double D related

[eugenebrooks]

Originally Posted by Joe Johnson

#2 I am thinking that we should have a target hardness of RC 40. This is a Tensile yield of 180Ksi (1250 Mpa). Is this too brittle? I am thinking it is probably ok. My reasoning is that I know that Forkbolts for car door latches are hardened to RC30-38. If RC38 is good enough to take the impact loading from a car crash, I think that RC38 is not too far. It is a small step from 38 to 40. Please share your educated gut feelings with us (provided you have an educated gut).

Joe J

Joe,

A target harness approaching RC 40 should be fine. We have run
welded axles, 4130 flanges welded with 4130 rod onto 4130 axles
for several seasons. We harden these and then temper at 800F.
Tempered at 900F, a little softer, the RC is 36 and the tensile yield
strength is 161,000 psi. We temper at 800, slightly off the charts, so
to speak, but safely above the brittle zone, to get just a little more
strength. We have bent these axles in competition with direct robot
impact on a cantelevered wheel setup, but have never broken one.

Hardening the carrier plates to a value approaching RC 40 is probably
just right. Using 4140, or even better 4340, is best for this application.
We are using 4130 because this is the material we have on hand.

Here is a link to useful heat treatment info:
http://www.aerospacemetals.com/steelalloys.html


Eugene