Banebot 56mm gearbox - double D - RELOADED

[eugenebrooks]

At this point, we have machined carrier plates and axles out of the 4130 steel that we have on hand, using a square broach for the carrier plate. We have hardened at 1600F with an oil quench, and tempered at 800F.

A link to a table showing the strength characteristics of 4130 as a function of the temperature for temper is shown below:

http://www.eng-tips.com/viewthread.c...=116052&page=4

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Following is a listing for tempered 4130 steel:

UTS YS

C F MPa psi MPa psi El RA HB

205 400 1627 236 1462 212 10 41 467
315 600 1496 217 1379 200 11 43 435
425 800 1282 186 1193 173 13 49 380
540 1000 1034 150 910 132 17 57 315
650 1200 814 118 703 102 22 64 245
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The yield strength at this temper is 173,000 psi and the elongation at break is 13%, not too brittle.

We have assembled and broken in the gear boxes using no load and 8 volt power, running both ways until the gear box "sped up" from the polish established on all the parts. This was about a half hour in each direction. We then inspected for any evidence of metal chips, and installed them in the robot.

We should get a day or two of testing by Monday. After some agressive testing, we will report the results.

The material is from McMaster and you can make these parts easily if you have access to a lathe, a mill, and a heat treating furnace. This approach to the problem is best described as Dr Joe's plan C. If you don't have this equipment, I would suggest that you head to a local machine shop that can heat treat with suitable material and the existing parts to copy with the modified square hole setup.

If I bought material just for this task, I would use 4340 steel and suitably adjusted hardening and tempering temperatures in order to get a little more strength while maintaining toughness.

Well, I would really use maraging steel from http://www.onlinemetals.com if I ordered material just for this, but I won't get into that.

Eugene