The SAK CS:R Center Foot

Mechanical Parts

There are several parts that you will need to complete the Center Foot Assembly.
updated 09/18/18

Caster Version
Colson Caster 1 Series Threaded Swivel Stem Caster
with a Performa Rubber (Flat/Grey) 3 in wheel
Part # 1.03054.441 MTG55 Note:  3/8-16  1.25 in stem
I bought mine on eBay from :
search for "Colson Swivel Stem Caster with 3" Performa TPE Gray Non-Marking Wheel"
they take best offers for 10-15% less, particularly if also buying wheels for the outer feet
at the same time (also combines shipping)

Vex Omni Wheel Version
based on work published by Kevin Holmes
uses 4 inch Omni Wheels
4 x  217-2584   4" Omni Wheel -
4 x  bearing (#2732):
1 Pack of  Spacer (#3260):

Omnitrack Omnicaster Version
need 2 - OC55 casters

Dimensions: 3/8" dia. x 1/16" thick - Grade N52
K&J Magenetics part number D61-N52
you'll need 8 - buy some extras! - also used in the Outer Foot Shell

two 3/8 x 4.0 inch bolts for axles and nylock nuts (vibration proof)
[thanks to Matt Gates for noticing the error - originally said 3/8 x 3.5in!]
four 1/4-20 x 1 inch bolts and nylock nuts -
to fasten either caster mount or wheel mounts to shell

I have an aversion to installing bolts in holes threaded into styrene parts when the bolts are under stress.
In order to attach the Center Foot to the Center Ankle I'm using a 3/8 x 1 in. aluminum spacer in the ankle
and a pair of 3/8 shoulder bolts in the foot shell.

The Shoulder Bolts
Shoulder bolts, Allen, Alloy steel black oil finish, 3/8" shoulder (5/16"-18 thread) x 1/4"
QTY 2 - Bolt Depot part# 14069

The Aluminum Spacer
Used as an insert the spacer goes into the Center Ankle to hold the shoulder bolts.
QTY 1 - Aluminum Spacer #AS38-14-64 For  1/4" or 6mm bolts 
OD = .375 (3/8") 9.53mm
 ID = .257 6.53mm
 L = 1.000 (1")  25.4mm
curiously enough the ID on this spacer (.257 in.) is exactly the size you would have to drill in order to tap it for a 5/16"-18 thread.
I can provide tapped spacers, with or without the shoulder bolts, at nominal cost (and a lot cheaper than buying the tap!)

I used both Weldon #3 and Weldon #16 cements for the assembly. Each at different points in the assembly process. You should use both, or equivalent cements.

A Note on suppliers cited
I have no relationship with any of them, except as a satisfied customer. Most were chosen because of their low prices, no minimum quantity order requirements, and cheap shipping.