I made a bit of progress tonight getting the center foot ball casters replaced with regular wheel casters.

One of the issues with using wheel casters is finding one’s that will fit. Many builders opt to use smaller 2″ or sometimes 2.5″ casters, but I really wanted to maximize the size to help with difficult terrain. I was lucky to get some of the magical 3″ casters from the Ace Hardware store down in So Cal with the help of a friend.

At first I thought they weren’t going to fit, so I double checked with Victor to confirm that he and Mike really are using 3 inchers. He assured me that they were and sent me some current photos to prove it, along with a few suggestions and tweaks they used to get them to work.

My plan is that any mods I make will not interfere with me going back and installing the original ball casters – just in case the new one’s do not work. e.g. I’ll be using the same mounting plate but will drill some new mounting holes.

I knew I had to remove some of the lip on the front and back of the JAG center foot shell – which I did with the Dremel and a file.

I also had to remove some of the casters mounting plate to allow it to sit closer to the edge of the foot shell.

It wasn’t important to keep the mounting holes as I’d planned on drilling new one’s to match the original mounting plate used with the ball casters.

Here’s the first real test fitting before any holes were drilled

Like an idiot I forgot to take photos of the new casters bolted into place, but I did shoot this short video showing them in action

As I show in the video, ground clearance is now 1.5″ as opposed to the 1″ I had with the ball casters. But this maybe a good thing as I plan on adding an extra “skirt” at the bottom of the foot shell to mimic the center foot as seen some of the movies.

It was getting late, but I did get the foot mounted and a quick test run highlighted a problem with the rear caster not spinning fully. I’m really not sure why it’s not keeping up with the front. It spins freely when I move it by hand but when I run the droid it seems to stick to one side and drag. If I spin him enough it’ll rights itself and sometimes it does keep up.

Here’s quick shot of it sticking – I was trying to do a right turn when this happened.

I suspect it might be something to do with the fixed angle in the outer feet/legs, using wedges, which should be an easy test to see if it’s the problem.

I also need to add some wedges to the front foot to stop it tipping. With the three original ball casters located in the extreme corners of the foot this rarely happened – but now with the casters closer to the center it tips/drags very easily.

I finally got time today to do some overdue maintenance.

I started off with the biggest issue that would most likely stop me going out again anytime soon – The center foot. At the museum event last week I’d noticed it was jittering way to much – it was probably the cobble stones that finally pushed the casters over the edge.

On the bench – I was surprised to find the two rear casters still in good condition and span fine, but the front one was in sad shape and would not move without some force. It has several gashes, dents and cracks – which isn’t a surprise really considering how hard I’ve been driving him this last year on all sort of surfaces.

I opened up the housing and on closer inspection it was obvious why it wouldn’t turn. It had developed a bulge and become pear shaped.

I could just replace it with another ball caster, but it would fail again. I’ve been planning on trying out some regular swivel casters for sometime, so later this week I’m going to try and get them mounted. The issue will be trying to get them to fit in the foot shell and maintaining the same clearance as before.

Another quick post with old work, this time on how I attached the battery harnesses to the boxes.

If you’ve been reading any R2 blogs for any length of time you’ll notice that most builders love silicon. It’s a very versatile and used to attach all sorts of things on your droids.

I’ve found out the hard way that not all silicon is created equal. Victor highly recommends GE Silicon II, and I have to second that. I’ve tried the generic brands and found they sometimes do not dry as well, especially if it’s a used tube, and often it will not bond well to aluminum or pull away after a while. This could be my lack of experience, but I’ve yet to have a problem when I’ve used the GE product.

I don’t think you need much silicon to hold the battery harnesses in place. I decided to add some to the top and the back side of the top swivel bracket.

And then gooped inside the lower bracket

I then moved the around until I was happy with the position and clean up the excess silicon before it had time to set.

Here’s a quick run down on how I attached the battery boxes to the feet.

I have the steel feet from JAG which include pre-cut key mounting holes for the battery boxes. I’d already fixed screws to the boxes when I cut out the holes for the motors.

But one of the problems with using the screws/key holes is that’s it’s almost impossible to set them correctly to get the boxes to fit (and hold) the boxes tight to the feet. I think if I didn’t have the NPC motors sticking well into the boxes, then the setup would work, but with the motors in place just getting the boxes on is challenge enough – without worrying about the key holes.

The other problem I had was the boxes were not even close to being straight/true, so when the front was tight to the foot the back had a gap, and vis versa. I’d tried tweaking them without much luck.

Originally I’d tried using some large beefy magnets to help fix the boxes to the feet. They kind of worked, but were easily pulled apart and had a problem getting the front and back to sit flat due to the warped boxes.

Gerard gave me a great tip to just screw the box from the back inside to the bottom of the foot – and it worked a treat.

I just held the box in place, marked and drill a hole in the box and thru to the foot

I tapped the hole from the underside of the foot

I’m still using the side key holes as well, but the new screw holds everything in place and stops the boxes from springing away from the feet.

Related Posts:

• NPC Battery Box Cut Out Template
• Finishing Battery Boxes and Feet

Here’s a great video by Mike Senna on how to pick and fit castors for your center foot.

I’m currently using omni-balls, but I may switch them out soon.

See also

• Proctor Glove Wheel Casters

I’ve been busy the last few days and not had much time for building. I did get to work on the ankles and legs a little bit more and I think I’m pretty much done, minus one small piece that I need to buy something for to fix.

I’ve mentioned this before, but now that the ankles are back attached the to the feet it was hard to slip the battery boxes over the motors.

The right box went on no problem but I had to make a small adjustment to the left one one and open up the hole a tad. I also had to shave a little bit more off the top of one of the motors, to get the box to sit flush with the foot.

The boxes are really springy with the hoses attached and and there is no way the two screws that are supposed to push fit into the slots will hold the boxes flush to the feet. At least I couldn’t get it to work satisfactorily.

I think I’m going to have to come up with another method of securing the boxes, and will probably use some super strong magnets. That way I don’t need to fiddle with setting screws in tight spaces.

I ended the evening with attaching the legs to the ankles. I used pan head bolts, lock washers and fender washers instead of the countersink Phillips. This will hopefully give them more substance and grip on the legs. The 10-24 Phillips work their way loose way to easy even with thread lock glue, and I’ve had a few wiggle loose during a single outing and sheer off. If this fix doesn’t work I’ll knock out the 10-24 threaded inserts in the legs and use 1/4-20’s bolts instead.

I’m going to try and paint the bolts and washers white to hopefully hide them a bit.

That just leave the battery harnesses and back foot strips to silicon in place, and of course the magnets to hold the boxes.

Okay, I promise this will be the last KHF post for a while. I bought a bunch of plugs from Ace and tried them out tonight and I think I’ve found a keeper.

It’s a small nylon plug that normally leafs out when a nail is pushed through, but I removed the nail and tapped the hole for a bolt.

I’m pretty sure it’ll hold for now, but would pull out if I gave it a really good tug. The good thing about this plug is that the expansion happens at the top in side the aluminum KHF holding it snug.

I also tried a small metal wall plug, but it didn’t work so well and deformed when expanded in such a tight space in the tube. I’d probably have to replace it every time I took the hoses off, it also didn’t grip the hose so well as the nylon one.

More re-assembling tonight after painting last week. I did a mix of things from the feet to working on some skin panels.

I got the feet and ankles back together, and using the hex bolts worked out great. It was a breeze installing the ankle details.

With everything R2, there’s always a few steps back with a dozen forward. Today it was the braided hoses. I’d planned on using these expanding rubber plugs to hold the cables in place, but they didn’t quite work as I’d hoped. For some reason rather than bunching up and expanding the nut inside just moved/ripped up the rubber with minimum expansion as shown. The ‘bulge’ at the top being the maximum width.

Back to the drawing board and Ace Hardware tomorrow to look for an alternative. I was tempted to try Douglas Olson’s KHF System again, but space is very tight and they’ll not work for me with the JAG feet and drive system.

The other problem I had was once I tried to install the battery boxes they wouldn’t fit over the NPC motors. All the test fittings I did while filing down the tops of the motors was done without the ankle on the foot, so now I have less room to bend the box over and down onto the motors. An easy fix, but I was hoping to get the feet, ankles and legs back together tonight and now I can’t.

I also worked a little bit more on the frame and got the front vents installed and attached to the frame at last. Not sure how I’m going to fix in the blue surround at this point. Maybe silicon, but I want to be able to remove it easily with the skins. The fit is tight and I can see when removing the skins that it may get pulled off with little effort.