Steve Nelson's R2D2 Build History, Documentation and Archive

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Fabricating Foot from Prints

After meeting a bunch of great builders over at the gathering at Mike Senna's house I was itching for a parts run to happen on feet. I checked around and saw that a foot run wouldn't be for a while, so decided I could make them from scratch with the blueprints that are on the club Yahoo group.

After studying the prints, I gathered a few materials I had lying around and started to create the pattern. First off I made a base flat to measure from and then slats flat and angled to form the base of the foot.
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Then to make the curve for where the battery box attaches I got a piece of ABS pipe with an inside diameter of 3" and prepped and marked it with a line to cut a quarter piece.
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Here you see how it will go together with an assembly template I made. I might even use the template to sweep Bondo over some of the surfaces when the time comes.
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I finally got the order of glue I was waiting for today so I can get back to building the pattern for the outside feet. I had some of the pieces cut and ready to glue and had bought a small set of files in preparation. Here you see one slot cut in the bottom trim piece that will go on the piece you see in the picture above. I'll need another after this one for the other side, and two smaller ones for both front and back.

Pattern making is slow! Rule of thumb is a month for the pattern, a week for the tool, a day for the part. This will take me much longer because I'm not on it full time, don't have a proper shop, and it's been 14 years since I've done this.
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I finished the pieces for the bottom of the foot, and assembled and set two up at the right angles. It's finally recognizable as R2's foot. To me.
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The last 3 days I've been sequestered in the garage, my computer here to my right with club blueprints burning my screen. I'm delighted to be patternmaking again! It's become an obsession! Grabbing any scrap of wood I could I managed to draw the side piece to the foot...
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I knocked the bottom out of a drawer to get a thin material to fabricate the step, cut and glued it to the side piece, set the angle and bonded it in place.
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A thick chunk of an old waterbed frame, the quarter radius of ABS pipe I cut last week, some assorted scrap and bondo, and many joyful hours of tedious measuring and viola! A rough, unfinished, almost completed pattern of R2's foot! It will be at LEAST 2 weeks of work to finish the pattern. I'll be lucky to get that much time spread out over the next month. I was going to build tonight but seeing the time and the fact I've got to get up at 4:00am to take someone to the airport, I had better pack it in 'til tomorrow!
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After many long hours of tedious yet fun work I got the pattern done and waxed with the first coat of mold release.
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If it weren't for the slots in the bottom trim of the foot that not only are 90 degrees to the face they are cut in and about .2 deep, but the bottom also slants down, I could make a simpler tool. This is one of the more complex pieces of tooling I've made, which is why it's taking me so long.

Since I can only pull a tool away from the part 90 degrees (directly away from) the bottom trim on each side, each bottom trim piece needs a separate piece to the tool! I sat and looked at it a real long time after I waxed it for the first time to be sure, and will still probably pull the pattern apart when removing the tool from the pattern regardless.

First I'll make 3 dams for the outside (left side on the picture above) bottom trim - two from the bottom corners out to the edge of the base, and one at (and splitting) the angle of the face with the step. All dams will be 1.5 inches, same as base, and each get a dimple with a large drill bit on the flange to lock the tooling in place when bolted together later.

Second will be the big flat side with the step. (I'm making a separate tool for the removable panel which will include the half moon, and other details.) Bottom dam is the now dimpled trim flange from the first layup, sides are dams going up and out 45 degrees from corners, and top will be a flat piece anchored in the groove, going straight up, so this piece will incorporate the .75 side of the top. I'm doing this to be able to get flex in the tool because only a few thousandths draft isn't enough and I want the tool to flex at the channel to help remove the part.

Pieces 3 and 4 are the front and back bottom trim pieces.

For tooling piece 5 I can set the pattern outside flat face down to do the inside bottom trim.

Six and last piece: The front and back face, the slot in the top, the inside face with the 1.5 radius is all in one piece.

I decided to leave off the front and back rear strip details in case I wanted to buy or make aluminum ones later. Below is another pic of the completed pattern.
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Well, I finished up making the dams, sealing and bracing with clay and superglue last night. I put the PVA over the wax with a brush because I still don't have the green wax and will need to finish sand the tooling anyway. Here are 2 pica of the first stage of the tooling build:
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I've got the tooling gellcoat pigmented blue. I'm waiting for the gellcoat to tack up right in this pic, then I'll do the fiberglass matt to about 1/8 inch. This will be piece one of a 6 piece tool.
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I think I might have over catalyzed the resin - it got SMOKING hot! I think it will be ok, though. The pic below shows the pattern with the dam around the first tooling piece which I had to trim on the bandsaw because it kicked so quick I missed the window to knife trim! I'll remove the clay to use over, same with the dams.
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Next, piece 2, the opposite side. The trim below the battery box gets a separate piece of tooling. I'm making the top dam on the same plane as the underside of the battery box so I can get small wedges between the part and tool for easier removal of the part from the tool. I'm taking a break to update this blog while the final coat of PVA dries. I have a coat of wax buffed, then PVA, another coat of wax not buffed out, and a final coat of PVA. That's how I'm doing all the releasing because I still don't have green Partall wax. I will need it when I make a part.
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I've just spent the past hour looking at this thing and have decided I had better make it a 7 piece tool. This has just become the most complicated set of tooling I have ever made. Well, maybe the tooling for the full-sized X-38 I worked on that Fiberset, Mojave, did for Scaled Composites was a little more complex - but for SMALL tooling, this is the max!

I'm thinking I better make a separate piece for the slot, to better remove the part from the tool. With that additional piece able to be removed it will be much easier to run parts out of this tool. Already I've changed the order of what piece gets made first and second etc. It seems it's all coming back to me after not doing this for over a decade. I always was good at making tooling on the fly, deciding what the next step was while finishing the step before.

I trimmed and cleaned the 2nd piece and planned what I'll do next. Would have cut the dams but it was after 10 and it make a racket. Sat and looked at it to work out the best way to proceed. Note the 2 small dimples and the half moon dimple in the sides of the tool where I'll drill and bolt together. That's to insure it will only go together correctly aligned.
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Here's a shot of the dams in place for the step side.
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And this is released, matt cut, and ready to layup.
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Done with the outside face that gets the door, I went ahead and built the dams for the center slot. This was an after thought as I began to see that the part would be difficult to remove otherwise. Here's a shot of piece 3 on that face, with the matt cut for the slot.
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After the slot layup, I did the other two trim pieces so the base of the foot would be complete.
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And finally, the seventh and last part to the foot tool, is seen here covered with gellcoat and ready for glass.
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After trimming the edges, drilling and bolting at the stress points, and cleaning it up a bit, the tool for the foot is now complete. Polyester will shrink 4-6% so I'll leave the tool bolted on the pattern for a couple of days. The next step will be making the pattern for the foot panel while the tool fully cures.
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Started on the foot door panel pattern a couple of days ago. It went really good. I found the right thickness materials and cut all the pieces. The moon was a challenge because of not having the right tools for the set up, but I was able to make due with my 123 blocks and a small aluminum plate. This is what it looked like with the pieces placed on the panel face.
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Just finished it up by gluing it on a board which will add the step to the panel. I'll scribe a trim line in the tool after I pull the pattern out of it. This pattern will most probably get destroyed when removing it from the tool as there is negative draft all over the place. I'm still going to wax the hell out of it, then give it multiple alternate coats of PVA and wax.
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Finished up the pattern for the foot panel with some clay to seal some gaps between materials and released it before covering it with gellcoat. Cut matt and prepped everything, let gellcoat tack and did the layup.
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While the panel tool was curing I carefully took the tool off the pattern for the foot. It pretty much destroyed the pattern but I was expecting that. I wasn't expecting there to be mold lock on the slot piece, however. I'll have to devise a way to get draft on the tool so I can get the part out.
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Next is the arduous task of finish sanding the tool. The pic below is the tool with the outside piece trimmed for the panel and almost completed.
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I'm still finish sanding and I'm finding delams. I'll fill with Bondo and set aside and do another piece til it's ready to sand. I'll rotate this process and have 3 pieces of tooling in process at once. I have 2 pieces "done" (meaning the flaws are small enough to live with). I've resigned myself to the fact I'll have to touch-up sand with 400 grit - or even 320 - when I pull the part from the tooling.
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I decided to pull the panel tool off the pattern. Had to see what it looked like. Chipped near the moon when pulling it. Looks, ah, OK - really rough and with chips. I wish I had taken more time with the patterns. The wood grain is killin' me! I obviously have not gotten my chops back yet.
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Here's a shot of my work bench with a slew of custom made sanding blocks and tools, the pieces in work, and the done pieces to the right above my magnifying glasses.
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I have backing on the panel tool to stabilize it while sanding, and have fixed about half the flaws. It may look good to an untrained eye but it's giving me fits!
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I haven't worked on my build or updated here in a while and I was starting to dream about the next steps I had to take. I finished patching the foot side panel tool today and threw a couple of coats of Meguiar's wax on it. Next is the Partall wax, then maybe some PVA (poly vinyl alcohol)...
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By the way, I'm not in the garage for this. I've brought things up one by one into my apartment. Didn't plan this, but just started by needing to rinse off the tooling and plan what I was doing next. Then measuring, then sanding, then WTF! get the bondo and set up some lights around a card table! You can tell I'm single. A wife would have already thrown me out and I'd be sleeping in the garage.
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Here are 2 shots of the completed Outer Foot Side Panel Detail Tooling Inserts. R2
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Next I had to fabricate the pieces that will form the Outer Foot Side Panel Detail Through Tabs. Then I was able to scribe on the Detail Inserts where the through slot will be cut in the Side Panel. I wanted to make a jig out of only 2 pieces, but couldn't find the right stock. I'll fasten the 6 small pieces of angle aluminum together later. R2
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Detail Tooling Insert scribed. I made the Tooling Inserts slightly indented so there will be a slightly raised platform where the Detail will slide so it won't scratch the Panel when moving. R2
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Here's another shot of the jig so you can see the scribe lines. R2
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This step is now complete. I documented the dimensions on the tooling and will draw up prints later. R2
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I joined the jig with bondo and superglue so now it's in 2 pieces. It's a lot easier to see how it will form the tab now. R2
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Waxed twice, tool and jig released and prepped, glass cut, next step is the white gelcoat. I've decided to layup with the white gelcoat instead of polyester resin since they are basically the same except for the pigment.

Today I saw a post about extended booster covers and jumped on it! I thought I was going to have to make the pattern and tooling for them since I'm planning on making the struts operating shock absorbers. I am glad to see I'm not re-inventing the wheel here. I'm just going to have to make a bracket or sleeve for the booster to slide in below the ankle bracelet now. That's going to save me a couple of months worth of work! I'm still working on how the quick disconnect will work where I'll have the feet come off when they need to be switched between carpet feet, parade feet, and tank treads.
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Here is the proof of concept on the detail tabs. I made it out of the gelcoat and 4 layers of glass. I'm going to make the actual 4 details out of polyester and matt with the gelcoat only on the front and side faces. I'll use 5 layers since 4 apparently was not enough. It trimmed down nice and I'm hoping to finish the details up and make the 2 panels by the end of the month.
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By the way, I'm so afraid of missing the UPS guy - or postman, or FedEx guy - that I built a post box for packages in case I'm not home when my booster covers come. Note the gap on the upper left of the door; that's what happens when you use warped wood.
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Proof of concept out of the way and it's time to make the 4 details. First gelcoat goes in the detail recess.
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Cut glass and prep and release the Tab Jigs.
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Layup and clamp the part.
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After cure pull the detail off the tooling and pull off the jig.
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Then cut and sand off the flashing and trim the tab to size.
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With the 4 details done I cleaned the tooling and put a coat of wax on it, inserted the detail plugs with the scribe lines and waxed them up too. Then I cut some templates for cutting glass.
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"Made it green." (Aerospace reference to coating with PVA.) Released with another coat of Meguier's and then a coat of green wax, then put a coat of PVA on it and let it dry.
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When the PVA is dry I mixed up the gelcoat and carefully brushed it on. I'll let it dry completely since I'm out of time right now. Even if the gelcoat cures completely there will still be enough crosslinking with the polyester to give a good bond. Next I'll cut the glass and laminate the first side panel!
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Got about half way through the lamination and it got away from me. (Notice the solidified resin in the cup on the right?) When it started to turn to jelly I cleaned up the edges and tried to catch it for a knife trim. This shot was taken after I managed to trim up the stray glass sticking out like needles before it hardened. I've got 2 layers down and was going for 4 but I may only do 3 if I get the proper thickness. Since this will be pretty much cured next time I work on it I'll sand off the high bumps and rough it up for a mechanical bond as well as letting the poly crosslink. This will also be a good time to modify the glass cutting templates to better cut the glass on the next Foot Panel.
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Sanded the glass flat and put one more layer just where the matt hits the plexiglass. Made the glass real juicy and clamped it so I'd have a flat surface on the inside of the door. I think I'll be OK with 3 layers for the door 2 for the half moon, and 4 extra in the top detail. Next I see if I can pull the part out of the tool without destroying either. I need one more panel out of this tool.
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I got the panel out of the tooling easier than I thought. The tool chipped in 2 spots on one of the slots in the half moon. I'll glue them back on later.
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Here is the panel before cutting the slots for the detail tabs:
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I carefully cut the slots and fitted the details. It looks like a pretty close match to where they are supposed to be located.
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A shot of the back with the tabs and slots shown:
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Here is how the detail will slide:
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And this is a shot viewing the scribe lines from the detail insert in the tooling that I cut the slot to. Next I'm cutting the slide that will complete the latching mechanism out of material I used to make the pattern for the foot panel as soon I make sure I don't need it for the center foot pattern. I know I'll have to glue strips of glass on the back of the panel to 1) center the panel on the foot, 2) shim the latch slide to clear the foot interior, and 3) to make the channel on the top that holds the top of the panel in. The slide I'm making now is just a mock-up to measure length of slide movement for the latches, and to have something to share with other club members that will stay together and won't fall apart in my hands at the upcoming R2LA 10. If other club members like this latch idea, I'm sure it can be done with aluminum, styrene, and wood feet as well. Please let me know if I can help.
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OK, I found a piece of the pattern for the foot panel and decided to sacrifice it for the latch slide, the shims, and the top channel. I'll use something else for the center foot. I'm using soft wood and tacking it down with superglue as proof of concept for the interior of the foot panel.
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Here is the layout I've decided on for the latch slide and shims. The top 2 pics are in the open position and bottom 2 are when closed. I've already decided on a dimension modification to the size of the step that the panel will sit on, and thus change the placement of the shims. The proof of concept appears to work and I play with the latch like a little kid opening and closing them, watching the slide from the back and the details on the front with the glee of a kid with a new toy on Christmas.
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And finally, here's a better view of the channel at the top of the panel that will need to be placed in first before sliding the details down to lock the panel in place. Next I work on the tooling for the foot so I have something to put the panel in.
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I'm currently sanding and filling voids in the foot tooling, but inbetween letting the Bondo harden I've been working on the door tooling, cutting more glass, releasing and gellcoating the tool and making the other door panel.
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Here are a couple of shots of the cured panel. The first is right when I pulled it from the tool. See the broken slot piece in the groove of the panel? They both broke off this time.
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You can see the flashing I'll have to sand off better here. Also I see some Bondo on the right of the half moon this will have to be replace on the tool. I may alter this tool to fabricate the 2 panels for the center foot. When the time comes, so will glue the broken pieces back before putting the tooling on the shelf.
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Holy freaking cow! I got home and lo and behold my extended aluminum struts had arrived USPS! They were packaged well and the top was EXTREMELY well protected with a dipped on protective coating!
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The first thing I did was put the spring in and test the compression wondering how heavy the droid will be at that point thus how compressed the spring will be in a static state.
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Next I got out some drawings and my calipers and checked to see how much will be below the ankle bracelet. Club spec calls for 4.250" of the bottom section to be above the bracelet, and in addition, a .450" length of the smaller section just above it. The extended struts are 5.500" long and next section is .950 to 1" with the spring uncompressed, therefore, 1 and 1/4 of an inch of the strut can go past the bracelet when the spring is compressed about a half inch. Now waiting for the booster covers.

*Note the drawing has the placement of the .450" measurement in the wrong spot. It should be in the space to it's right.
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Been finishing the foot tool over the past 2 weeks. Tomorrow evening is the dinner for R2LA 10 and I was hoping to have a foot shell ready but life got in the way! I'm making all the rookie mistakes I made when I first started tool making. The pattern wasn't smooth enough, the tooling was made too fast and I got delams in the glass, I didn't finish sand well enough - basically I was in too much of a hurry! Good thing I only need to pull 2 foot shells out of this tool! When I go to make feet with a parade drive, and another set for sand, then I'll take my time with the new tools and maybe even use epoxy so it won't shrink as much, and it gives me a little more time before it cures. As you can see the tooling looks kinda hammered.
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In spite of realizing the part won't pop out of the tool as a finished part like it should, and will take sanding and finishing, I'm going ahead anyway. Here is the tool in the 2 pieces I'll layup the part on all waxed with a coat of Meguier's, a coat of green Partall wax, and a coat of PVA.
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Next I gave it a coat of gelcoat and let it set. I thought it was a bit thin so I gave it a second coat - like an IDIOT - and it began to alligator on me! Now I panicked and dove right in.
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First I did the bottom of the door piece, filling in the grooves around the rectangles, then I put 3 layers of glass around the lip of the top. Then I filled in the bottom 3 sides of the rest of the shell, put the tooling together, and placed one piece of matt on the inside of the top groove and put a sanded aluminum plate over it. What a freaking mess! I'll let it cure and finish the rest later. Right now it's late, I'm full of itchy glass, and I need to crash.
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Here's another angle - you can see the place where it began to alligator at the top under the slot where the ankle fits.
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Catching up:
I finished the part the night before R2LA 10 and it cured over night. That morning I broke it out of the tool, sanded off the flashing and brought it and my door panel to show there. It was gratifying to see the positive reaction, and I was even asked about doing a "run" of foot shells. (The tooling wasn't made to support a run, but if more guys ask me, I'll check out what the club rules are and make tooling that will support a production run.)

For pictures from R2LA 10 click here: R2LA 10

Next, I cleaned, waxed, and released the tooling. Here's a shot of it ready for gelcoat next to the first foot shell.
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I then brushed on the gelcoat for the second foot shell, waited a day, and did the layup. This shot is interesting in that you can see the amber color of the glass that's kicking, and the blue-green tint of the glass that's still wet. For some reason I thought it would be a good idea to mark the two aluminum plates on either side of the groove for the ankle bolt in one inch increments.
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What's NOT interesting is that I was eye-balling the ratio of catalyst and apparently under-catalyzed the side pieces! They took a really long time to kick, and I may have to cut out parts and patch them! Another rookie mistake that shows I still have a ways to go to get my chops back!

While the second foot shell was curing, and after careful consideration, I decided to re-do my dome. At R2LA 10 I had the opportunity to examine a few pie panels and found that the only one I cut from my present dome was much too small for the accessories made by the club. I remember a trick from my aerospace days of laying up the panels first, then the dome around them. I began by scraping off the 35-year-old masking tape.
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I plugged the holes with Bondo and I washed off the dried tape residue and silver paint with acetone. Next I'll contour sand where the cutouts were and finish the dome as I would a pattern. I've got to decide wether to add the 2 rings between the dome and body now or add them later. I still need to make a tool for them and it may be easier to make them all at once. Or maybe not.
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Here's a couple of shots of what the foot shell looks like before I sand off the flashing:
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Here I'm trimming to the scribe line I put on the tooling, which transfered to the part.
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Now R2 has feet. Drilled a 1/4" hole through for a bolt and wing nut and it's a tight enough fit to stand the droid without a face plant. I'm guessing by the pictures I found that the through holes are centered in the slot. I couldn't find any measurements on any of the prints I scoured, so I just guessed at this. Since I scraped the 35-year-old masking tape off and washed off the silver paint and black marker from the dome, it looks a lot less R2-ish, but---
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---from this angle you can see the new parts - the glass skirt and feet - look pretty nifty! The feet fit nicely on the mock legs I painted last year. Note the aluminum strut I bought and have taped to the leg with packing tape.
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I'm pleased with the simplicity of the latching mechanism, and how it will work with styrene, aluminum, and whatever else you build with. (My initial prototype was in wood.) I have the measurements on a picture above for the details that slide and for the through-hole, and the next picture up is a template you can print, cut, and use for the 7 interior pieces I made from fiberglas stock I made shown here:
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Here's the template you can print, cut, and use for the 7 interior pieces I made from fiberglas stock. Print at 103% and I think the scale will be right. I included a scale in inches to give you a reference. If I ever leave something out, please ask.
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