Sunday, March 5, 2023
Greenwich armour project - Facts and figures.
Friday, October 22, 2021
An Apollo Hatch
Long before computer operated mills (CNC) all of this was done using "a meat computer"; the guy turning the handle, knew how far to turn it.
As a kid, I hung around my dads aerospace machine shop, and watched guys on old Bridgeport mills, turn blocks of metal into amazing mechanical shapes.
The main hatch of the Apollo Command module, that took men to the moon, was a beautiful piece of mechanical art. Fabricated by guys like the ones who worked for my dad. These unassuming guys, in their plaid shirts, oil stained leather aprons, cigarette in their mouth and a cup of coffee on a nearby bench, created the millions of parts to America's Apollo Spacecraft, with no computer operated machines, just their skill and experience.
Know as the "The Unified Hatch", this was a 350 pound, quick opening "vault door".
It was called the unified hatch, because the original design, was actually 3 separate hatches, all of which had to be opened by the astronaut, in order to exit the spacecraft. After the tragic accident of Apollo One, in which a fire developed so quickly, that opening these hatches was impossible, NASA required a new design that could be opened quicker.
The redesigned hatch could be opened in around 3 seconds, and get out of the spacecraft in less than 30 seconds. A great improvement over the 60-90 seconds for the original design.
Utilizing 15 latches, a mechanical gearbox, a counterbalance system and a gaseous nitrogen operated piston, this was an incredible piece of engineering and machining.
This is the hatch from Apollo 11, which is now on display in the Smithsonian's Air and Space Museum. |
In early 2019, I was talking with one of my clients, who had purchased one of my replica Apollo spacesuits, about the amazing accomplishments of America's industry, in designing and creating the massive amount of technology and hardware for Mercury, Gemini and Apollo spacecraft, in only 9 years. We both were fascinated by the spacesuits the astronauts wore, but at some point in the conversation I brought upon the Command Module hatch as one of my favorite pieces from the spacecraft. He agreed and I mention how I had wanted one, just to hang on my wall, to showoff the skill of the 1960's machinists I admired as a kid. He said it was one of his dreams as well, them paused, and asked, "do you think you could build one?" At first I thought, no way. Those guys were far more skilled at machining than I'll ever be, but then realized that much of their skill and experience is sort of "captured" in the computers that run CNC mills and lathes today. For 40 years, I have been building things for film, museums and some for aerospace clients, and I thought well you have figured out complex projects in the past, why not this.
I told my client, that I thought I could....but it would be very expensive. He asked how much. I gave him a ballpark, thinking I could wriggle out of telling him I could build this, and he said, OK, think about it and give me a formal quote.
Once I had the check in my hand, I realized there was no way of getting out of it. So, like with any project, you start by gathering images and information. Having spent 30 years building replica space hardware, I have become friends with a number of retired aerospace people, and collectors. I have built full size Lunar Modules, both interior and exterior, along with replica's of just about every spacesuit that has gone into space. But, I hadn't done anything from the Command Module before. Well I had to start somewhere, so I reached out to my usual sources. Information was slim, but I did manage to acquire some original drawings and spec sheets on the hatch, alone with some high quality images of the individual hardware elements. There was also an Apollo hatch near me in the California Science Center, which I have done work for.
One big advantage I had (which had not occurred to me initially) was having grown up around the type of shop that built parts like this, I was recognizing machining details, edge treatments and surface finishes as I was looking at the photos.
Real Apollo hatch in the California Science Center |
Gearbox detail of the Apollo hatch in the California Science Center |
My replica of the Apollo "Unified" hatch. |
Monday, March 22, 2021
Greenwich armour; Nearing the finish line.
Monday, June 8, 2020
Greenwich Armour- One step at a time
I have been asked many times about the process for etching and plating, which I have mostly addressed in earlier posts. This is my first time doing anything like this, and as I have progressed, I have discovered better or more accurate (to the original armour) ways to do this. I have tried to update the techniques whenever I have found something that works better.
At some point, at the end of this massive project, I will have to post a synopses of the techniques I use and see how my experience over the course of a couple of years working on it, have changed my approach.
For now, I have a list of all the steps from getting the heat-treated piece of armour, to the final assembled piece. (For those of you who make armour, some of these steps listed are obvious)
The decoration (etching, gilding & bluing) involves 40 steps for each plate:
Greenwich armour Decoration steps (after heat treat)
1. Polish with 400grit greaseless compound
2. Polish with white “stainless” compound
3. Pattern sunken areas for artwork with masking tape
4. Scan masking tape patterns
5. Draw or modify decoration artwork (on computer) for unique areas of the plate to be masked.
6. Cut vinyl decoration masks
7. Weed vinyl & add peel cover
8. Clean steel with acetone
9. Apply vinyl’s to steel plates. (Figure 8, wavy and vine patterns)
10. Adjust vinyl, trim overlaps
11. Clean surface with alcohol & window cleaner
12. Add dots and any missing artwork (averages 100 dots per inch of decoration)
13. Let dry 10-15 hours
14. Mix paste batch let sit for 3 hours, remix
15. Apply 1st paste batch- let sit for 2 hours
16. Remove paste
17. Apply 2nd paste batch- let sit for 2 hours (fix dots as needed)
18. Remove paste - rinse with water & dry
19. Apply 3rd paste batch- let sit for 2 hours (fix dots as needed)
20. Remove paste - rinse with water & dry
21. Apply 4th paste batch- let sit for 2 hours (fix dots)
22. Remove paste - rinse with water
23. Clean off vinyl decoration masks and dots (very hot water and soft metal scraper)
24. Dry part and remove large area masking
25. Assemble part to check artwork alignment
26. Power wire wheel etched areas (from all four directions)
27. Thoroughly clean with acetone, window cleaner and alcohol
28. Paint black paint (Rustoleum high temp black) onto specified areas (let dry for 12 hours)
29. Wet sand etched areas with 2000 grit paper removing over-paint
30. Mask areas not to be plated, with nail polish (dots and edges)
31. Electro clean surface to be plated (Heated to 160 degrees F.)
32. Rinse with distilled water
33. Nickle plate
34. Rise with distilled water
35. Gold plate
36. Strip nail polish masking with acetone
37. Tape off plated areas with masking tape
38. Re-polish areas to be blued
39. Put in oven at 290 Celsius until correct blue color is achieved then remove
40. Spray with surface protectant.
Part is ready for straps, linings & assembly
This requires
1. Cut buff leather strap (first find true "buff leather")
2. Split it to to half thickness
3. Cover with antique French burgundy velvet ribbon and sew in place
4. Make strap ends in brass
5. Solder brass 10mm caps on rivets
6. Scothbrite then wire brush surfaces of all (buckles, strap ends, rivets)
7. Rinse with distilled water
8. Nickle plate
9. Rise with distilled water
10. Gold plate
11. Rivet buckles and straps in
12. Rivet armour plates together (Also add articulation leathers)
Here is the size of the dots needed. (and the ones shown here are a touch larger than the original)
These are added one at a time with a needle bottle with a 27 gauge needle. (McMaster-Carr PN-1902T341)
I was using nail polish, but recently, I have switched to a marine paint made by Duralux (purchased - Home Depot-online)
The paint seems to be more durable (against the salt paste) and flows better with the needle bottle than the nail polish.
Here is the right arm complete. (The left is waiting for it's last 3 rivets, I can fit the mounting pin for the jousting Passguard)
I have added elbow straps, even though there seems to be evidence they did not originally, but since I am unsure of this, I added them. If they prove useless, I can cut them out at a later date.
Next, the Pauldrons....
Wednesday, December 11, 2019
Heat treating armour - A modern way
Without going into too many technical details of what heat treating is, let me outline the process for those unfamiliar with what's involved in heat treating steel. However, first off, I am not an expert in heat treating, so forgive me if I get some technical bits wrong here.
The basics of Heat Treating steel.
First: Heat the metal to the correct temperature, this varies with the type and alloy of metal being hardened, but with steel you are in 1500-1650 f / 815-870 c temp range. In addition; The amount of time at that specific temperature is important.
Second: Rapidly cooling the piece, by quickly submersing it in a "quench" of water or oil or molten salt (see below)
Third: Reheating the piece to a much lower temperature, in this case 500-750f / 260 - 400c to "temper" it so it is not brittle like a piece of glass. This is where you can control how hard or flexible the piece can be. Either hard like a file, or flexible like a spring. The choice of metal alloy you use is a big factor of these properties.
For my Greenwich armour one of the factors in deciding to use a commercial heat treating company was I'm using a "modern" steel, in this case 1050, and they will know exactly how to process it to the desired hardness. If it's too hard, it will crack when struck, too soft and it will dent easily. 1050 is a close modern equivalent to what the medieval or renaissance armorer was using. This alloy of steel has just enough carbon (.50%) so it can be hardened, but is not an exotic modern alloy with lots of other types metals mixed in.
The big advantage to a commercial company, is the use of modern vacuum or atmospherically controlled furnaces, which eliminates oxygen around the heated part. This keeps the surface from oxidizing or "burning" while it's glowing orange, resulting in a "scale" on the surface.
This way, your piece can be surface finished to bright or polished, and the surface will be undamaged by the heat treating process. It will turn blue, but bringing it back to "white" is pretty easy.
Another advantage, is salt quenching. The advantage here is lowering the thermal shock to the piece being hardened. Going from 1500f to 80f of your oil or water quench tank, is a severe drop and can cause a lot of distortion in the work. In order to harden the steel however, you do not need to drop the temperature by 1400 degrees, you only need a drop of 800 or so. One way to do this, is to heat salt to 600 degrees and quench the piece in that. The only down side to a salt quench is you can't have any plates riveted together or other places the salt can get trapped. Because after quenching, they will thoroughly clean the parts, and any place they can't get to, that traps the salt, will corrode.
Since this process is done on a lot of material in a commercial heat treating facility, it's pretty reasonable cost wise. A batch of around 20 ponds of material will cost in the neighborhood of $200 (This is a bit of a guess from memory, but when I get this next batch back, I'll update the cost)
I-Beam clamp from McMaster-Carr (PN-29915T81) |
On the most recent pieces, in this case the pauldrons, fauld, and arms, I found some "beam clamps" which are used for securing things to metal I-beams. These can be bought on Amazon for around $1 each, but the only ones I found are galvanized, which would have to be stripped off before using them. Another source is the company McMaster-Carr, they have unplated ones for $2.30, so I used those. These clamps come with a 3/8"-16 bolt and nut, so once clamped the nut can be used as a jam nut to lock the bolt in place. These are threaded on both sides, so another bolt can be threaded in from the other side giving you the option to pinch the part between the bolts.
The resulting clamp arrangement means you can now just "Connect the dots" with some steel bar, or in this case square tubing. The clamps can be pivoted to facilitate using a straight piece of tubing to connect multiple clamps like seen above on the fauld lames. Here is the finished bracing.
I try to leave a flat stable surface on one or more sides so the parts can sit nicely in the furnace. Anywhere there are rivet holes between plates, #5 screws are used to secure the plates to each other. While a #5 is an odd size, it is almost exactly an 1/8 inch in diameter, which fits perfectly in the rivet holes. Once the pieces come back from the heat treater, I'll cut the clamps off the frames, so I can reuse them. This also is a great way to use up the short scraps of steel tube our shop seems to generate.
The arms and pauldrons are braced in a similar manner.
For the cuirass, I used a technique I used before, where I make tabs from 1/8" strap stock with holes, that secure to the armour through rivet holes with the #5 screws, and then I connect these tabs with steel tube. In addition, I drill holes in the steel tube and weld nuts over the holes and thread a bolt through and pin the armour. In the case of the cuirass, this requires a frame on the outside as well. I try to design it so I don't have to cut any of the tubes to remove the armour.
In addition, I have added tabs on the front and back of the bottom skirt to trap it against the inner steel frame.
Once these come back, I'll clean the surface back to white (shiny silver) and start the etching.