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.

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.

I was going to add a few more coats of paint to the skins today, but on close inspection in the daylight they looked fine. A lot of the dust spots I was seeing yesterday just rubbed off with my finger now that the paint has had time to dry. I’m going to leave it a few more days before I attempt to remove the masking tape, as it’s been pretty cold and I’m not sure how the paint cures in this sort of weather.

I’ve decided to re-assembling R2. Started off with something easy - the center ankle as it’s relatively simple and self contained. I need to get him back on 3 legs to start laying out the electronics again. I’m probably going to move things around a bit, for example I know the speed controller can’t stay where I had it on the back mounting plate as it now hits the skins. It may end up on the back side of the plate or somewhere else internally. I also want to build in some sort of switch and circuit to allow me to charge the batteries in place rather than having to remove the cables each time to clip the charger on.

I’ve been paranoid all week that I’m going to ding or mark the paint, and tonight I had to moved passed that. Right off the bat there was no avoiding dirty fingerprint from the grease when handling the new white paint, plus I scratched a some paint off trying to get the ankle to fit back in the foot shell slot. I really should have filed down the metal parts a long time ago to compensate for the added paint - but I didn’t. I’m sure it going to wear off in this spot anyway, but don’t ya hate it when something like this happens?

I’m glad now that I didn’t get things powder-coated and at least I can touch it things up myself if I need to.

I’m going to have to keep an eye on the foot shells as they’re steel and prone to rust, especially where I live on the coast. It’s ironic that one of the reasons I went with an aluminum droid was because wood warps so easily here, even when sealed, and now here I am worrying about rust from the salt air. I may just grease up this area when I get around to weathering him.

I also noticed that nearly all of my ankle cylinders are scratched up and should really be repainted, but I’m not going to do it this time around.

I used silicon to attach the foot strips to the foot shell. I should probably tap and screw them on, but I’m feeling lazy and really want to see this done. I roughed up the two surfaces and taped on the strip. I’ll probably know tomorrow if it works.

I think it looks pretty cool all put together don’t you think?

One last thing while I remember, don’t forget to use screw Loctite or something similar. I missed a few screws in the feet before C4 and lost nearly all of them by the end of the week.

I’ve had an incredible busy weekend working on R2. I’m getting close to re-assembling him with all the skins and parts bolted on and everything painted.

If you’re browsing the gallery for new photos you’ve probably spot a lot of new work over the weekend. I tend to upload photos quicker than I can blog them here

Throughout the 4 day holiday weekend I’ve been slowly prepping and painting everything that I could, including the legs, feet, ankles etc. Every time there was some downtime I’d turn around pick something up of my paint table, take it outside and give it another coat. I must have applied 3 or 4 coats of the white by now. The paint job isn’t perfect but it’ll do for now, plus I’ll probably be weathering him at some point soon.

I also finished painting all the remaining blue pieces, mostly body detail parts like the octagon ports, power couplers and vents . Once the skins are done and fixed to the frame I’ll be in good shape to start mounting the parts.

I started to use a self etching primer on some of the latest alu parts. I’d been looking for a self etching primer locally for a while and I finally found some in stock at Kragen’s. The problem with the small local auto places is that they seem to only carry one can of some paints, and refuse to special order - so each time I looked they were out. Anyway, it got lucky this time and I picked up the Duplicolor primer (olive green top.) You can see the olive colored parts in the first photo.

I guess my new hypo blue formula is

Duplicolor Self Etching Primer - wait 30
Rustoleum White Primer - wait 30 (maybe apply 2nd coat after 15 mins)
Rustoleum Purple - wait 30-45
Duplicolor - wait 30-45
Rustoleum Clear Coat (maybe two coats)

The biggest thing I probably worked on was gluing the skins together. I’d flip flopped a few times on how how I was going to do this. I really like how Victor has left the inner skins unpainted to show off the panel detail. But having an aluminum frame makes it a lot harder to mount the skins separately, so I’d probably need to paint them in one go. I’d considered using silicon to bond things together, but from some tests I’d done with some of the doors panels, it delaminates at the edges too easily. Cleanup is also hard and it’s difficult to remove all the excess silicon. If you’ve ever tried to paint over silicon you’ll know how bad that can be. The door panels I’d glued together had small fish-eye marks once I painted them. I think I can work around it, but all the other panels will be epoxied I think.

After a bunch of emails back and forth with friends, and a phone call or two - In the end I opted to use a cheap home-brand 60 minute epoxy from Ace Hardware. It’s supposed to setup in 60 minute, hard to the touch/movable in 4 hours and sets fully in 24, but even after 2 hours it was still very soft. Which was good news as it allowed me plenty of time to clean up the excess that squished out. I only had enough clamps for one half of the skins so I tackled the back set first. I’m hoping to get to the front set tonight then on to mounting them on the frame.

I think in the end there was over 60 clamps, paper snaps and clothes pegs stuck to the frame.

This morning the skins had definitely stiffened up, and I’m glad that I’d made sure they were sitting in the correct curved shape I marked on the workbench before going to bed.

Talking of mounting the skins I’ve flip flopped on how best to do this too. Like anything to do with R2 building there always more than one way to go, and there is never a right or wrong answer. I have skin mounting systems from Daniel and Darren, both are very different with pros and cons to each. Darren’s quick snap mounts are made from plastic and allow quick and easy removal, where as Daniel’s are aluminum and require screws to hold everything together. Having experimented with both I’m opting to go with Daniel’s mounting blocks for now.

I also worked on getting the skirt finished this weekend. I didn’t quite finish it ready for painting, but I did get the strips mounted. It probably took close to 4 hours to drill and tap all the small holes.

I started off by marking up where the strips would go and drilling a series of holes.

I then clamped each strip one by one into place, center punched through where the strip needed to be drilled, tapped the hole, reattached to the skirt, repeat for the second hole. That’s a total of 48 holes and 24 taps needed. I also had to cut down each screw as they were too long!

The holes in the strips do not go all the way through, so tapping them was hard and didn’t leave much for the 4-40 screws to hold onto.

Each strip had to be tweaked and filed to get it to fit, and due to the construction of the skirt, some strips are too long and need filing down in length. I’m also going to have to bondo/fill in the gaps before painting.

I’m sure there was more done this weekend, but that seems to cover most of it for now.