Finally got tired of the single caster in the center foot. My droid is styrene (Dave Everett’s plans) so it weighs just 89 lbs. Its been a solid droid for the last two+ years. However, you can see in the video it does not do well on cracks/lips so door transistions, sidewalks,etc are a nightmare. Decide to go with the vex setup using Kevin Holme’s bracket, added additional brackets so that its all metal from the center ankle bolt down. Then used Michael Baddeley’s center… foot 3D model, and modified it to fit my custom setup using Fusion360. The new center foot adds 3.5 lbs so now it weighs 92.5 lbs.
Printed the foot at 15% infill / 4 layers / 0.25 layer height, and then printed the sides at 15% infill / 4 layers / 0.1 layer height to smooth out the curves of the half moons. The left side is glued on, the right side is held on by magnets (mounted in the insets). The foot is solid!
There is access to the bolt to install/remove the bolt (and its large enough for a socket to fit over the bolt head), plus there is a hole for a screw to lock the ankle/foot, it also includes a slot for a washer and the nut.
The video shows the clear difference between the two. Now just need to prime/sand/paint and it will be show time! Also thanks to Greg Tracy for the huge assist on my build in the first place.
Kevin Holme’s bracket – $35 http://holmemadeparts.com/Front-Foot-Vex-Wheel-Bracket-Vex-Plate.htm
4 – 4″ Omni-Directional Wheel – part #217-2584 – $18/each – $72 https://www.vexrobotics.com/vexpro/motion/wheels-and-hubs/omni-wheels.html
4 – Flanged Bearing – 0.375in x 1.125in – part #217-2732 – $3/each – $12 https://www.vexrobotics.com/bearings.html
1 – Angle Bracket (Lowes) ML24-TZ 2″x2″x4″ (cut in half) – $2 https://www.lowes.com/pd/USP-2-in-x-2-in-x-4-in-Triple-Zinc-Angle/50325313
2 – 3D Printed 0.5″ versahub
2 – 3/8″-16, 3.5″ long bolt – part# 91257A639 – $1/each – $2 https://www.mcmaster.com/#91257A639
2 – 3/8″ washers
2 – 3/8″-16 Locknut, heavy vibration – part# 94820A242 – $1/each – $2 https://www.mcmaster.com/#94820A242
6 – #6-XX, XX long screws, through VEX wheels to tie together
4 – #10-1/2″ bolts
4 – #10 nuts
Center Ankle Bolt
1 Shoulder Screw – part# 94496A540 – $7 https://www.mcmaster.com/#94496A540
1 3/8″ Washer
1 1/4″-20 Nut
3D Print Files:
Ran into a problem with the Banebot wheel/hubs on the jaycar motors. No matter what I tried the hubs would eventually slip on the drive shaft. The drive shafts of the jaycars are keyed, but the banebot hubs are not and require a set screw. I tried dimpling the set screw, using loc-tite, etc with no success. Eventually the hub would come loose and slip.
I decided to go with DFRobot wheels (KIT0044) which came with a keyed hub, so I ordered 4 thinking I’d use 2 wheels and have 2 spares. Turns out I ordered 4 sets of 2 wheels. Cost for two wheels and hubs was $39 with shipping.
Got the wheels and used some of the free time over the holidays to install them. Since these wheels are slightly larger than the banebots, I had to remove about 1/8″ on either side for clearance, but since its styrene it didn’t take too long. Here are pictures of the before/after:
The worse part of the hub slipping was the hub would then get stuck on the shaft. I would remove the set screw and still could not get the hub off the drive shaft. Which in turn meant I could not remove the motor from the mount plate. Thankfully my friend Greg cut me two more sets of mount plates and I purchased two new jaycar motors. Now I have spares! Here is the destructive testing I did to remove one of the hubs, still have one more to go.
Picked up four 12″ braided stainless steel faucet supply lines from my local hardware store. I’ve seen various lengths described on the boards but decided to go with 12″. In hindsight it may have been cheaper to go with 24″ and cut it in half. The cost was $5/each for a total of $20.
I’ve seen various ways to connect the hose to the knurl fittings, and the fittings to the foot/battery box. I also saw a few come lose at Celebrations by catching on things or being knocked off by other people.
I decide to go with a magnet approach, this way if they get caught on something they should easily detach. In look at the hoses and the fittings I decided to glue the fittings to the feet/battery box and add a magnet to the end of the hoses. So the hose will pull out from the fitting (in theory).
I purchase 8mm diameter ‘Super Magnets’ at Home Depot for $4.
It took a few attempts to figure out exactly how to make it work. I tried just gluing the magnet in the hose, but it kept turning and twisting. The solution was to use a slightly smaller wooden dowel cut to about 1/4″. I glued the magnet to the dowel, and then glued the dowel in the hose. You will also notice I wrapped tape around the hose for two purposes. One was to prevent the braids from separating and the second was to retain the circular shape when gluing in the dowel.
I was going to glue a magnet inside the knurl fitting to give a strong magnet to magnet hold. I decided to just glue in a steel washer for the magnet to attach to as I was having problems getting the right side of the magnet (for polarity) to stay face out, plus the depth of the knurl fitting didn’t conceal the glued part of the hose where the dowel was situated.
I used Citadel Reikland Fleshshade paint that I bought from Games Workshop to color the hoses closer to what is seen in the films. Cost of the paint was $5.
Here is the finished product, looks good to me.
Now that the inner skin is on, I again could not resist putting R2 together. Did this after work, four of my neighbors stopped by and a few honked as they drove by.
You’ll notice I haven’t done anything on the dome……
For the Main Ankles I’m using a 3/8″ threaded bolt, 2″ in length with a steel sleeve for the connection between the main ankle and foot, I didn’t want the bolt threads wearing away the styrene. The bolt has a 9/16″ head which I’ve marked for easy of finding the right tool in the future. I glued the washer onto the styrene facing the battery box, but there is not enough clearance for the nut and washer on the outside face. I’ve drilled a hole in the battery box to allow access for the bolt to be inserted and access to the hardware from that side. It is tight on the outside so getting the nut on the bolt is tricky until it starts getting threaded.
Here is a picture of the bolt/nut installed, notice the 9/16″ again on the inside so I get the right wrench the first time.
I’m going to be using the Jaycar motors ($40/each + $25 shipped) for both feet and the dome as recommended by Dave. I bought a 7mm/8mm ratchet wrench from Sears for $7. It works extremely well for attaching the motor support plate to the foot.
I ordered the wheels (T80P-493BG-HS6) and hubs (T80H-SM61) from BaneBots for $37 shipped.
Looks like I’ll be going with SAE bolts for the ankle/foot hardware since larger metric bolts are as easy to find at Home Depot or Lowes. I also didn’t like the ide of threading the bolts into the styrene so am going to use a bolt all the way through with a metal sleeve to prevent the bolt threads from wearing on the styrene directly.
I’m using a 3/8″ threaded bolt, 2″ in length with a steel sleeve for the connection between the center ankle and foot. I’ve recessed the washers and glued them in place on both the bolt and the nut side to give more metal bearing on the styrene. Since the area is too tight, I cut out the left side panel to allow access to the hardware, it reattaches with rare earth magnets I bought at Amazon.
Center ankle hardware
For the caster, I found a 3″ Waxman rubber caster at Lowes. Wheel diameter is 3″ and the mounting height is just under 3-1/2″. LINK
I had to make my own ‘wrench’ out of styrene since there was not enough clearance for a regular wrench.
Center Ankle hardware: $7
Began working on the main feet and the center foot. These are by far the toughest pieces to assemble because of all the chamfering. Its even more critical because the shells add to the structure of the foot so they need to match up or you’ll need to fill in with scrap pieces. Thankfully styrene and IPS3 makes it easy to ‘patch’ things up when you go nuts with the dremel.
For the chamfering, I tried a ton of ‘tricks’. Turns out the easiest for me was to use the dremel freehand for the first couple passes and then use the file to clean it up.
Sheet of foot pieces
Ordered the following resin parts today.
Under Shoulder Details
Wayne uses aluminum particles in his pieces so they look like aluminum, decided to go this route for the silver parts instead of using Rub-n-Buff that Izzy keeps saying is easy to use…….we’ll see.
Resin parts: $267