Monday, 25 August 2014

Bearings & Shoulder Rebuild

A rainy Bank Holiday in the UK, so what a better way to spend the day..... playing with Armdroids of course !!

Its been a while since touching my Armdroid, or the one being restored for The National Museum of Computing, and decided today, I would strip down the base, clean, and inspect every individual part before rebuilding again.

I've not previously covered anything on the Blog about the Bearing Assemblies, so thought this would be well worth some coverage here.

The following picture is a recap from last year, what my bearing assembly looks like:



This is a custom machined from Aluminum which forms the following components: (1) Base Bearing support column, (2) Shoulder Bearing support, and (3) Bearing adjusting ring (pictured with grub screw).  This is complimented by 24 ball bearings fitted around the upper and lower flanges.   Reading the construction notes, I imagine its quite a fiddle to assemble, keeping the ball bearings in place whilst turning over to work on the opposite side.

When first inspecting TNMOC's Armdroid, I always knew there was a difference with the bearings, but couldn't see clearly what was happening under all the dirt 'n grime, but, check this out - beautifully machined from solid brass



...which accepts flat needle-type roller bearings with steel shims for the upper and lower supports:



This is how the top of the assembly looks without the other assembles installed:


I'm guessing a previous owner made this as a repair, or perhaps an enhancement to the original assembly
Update:  After searching the internet and examining further photographs, I've now seen plenty of other examples of this arrangement, implying Colne Robotics introduced this as a later improvement.

The center bore for the cables is a lot narrower than the original assembly which does make feeding of cables tricky.  Another observation with this design - its no longer possible for users to make adjustments here.

The original assemblies can be easily damaged by cross-threading the adjustment ring, so be careful not to over-tighten if you need to make any adjustments here.

Having stripped all this down, gave it a jolly good clean, lubricated all moving parts, rotates like a dream now!

I've added more photographs of the rebuild below - might be useful if your rebuilding your base and shoulder and need a reference.