Scavenger Workshop

Info. from Devin's posts on Astromech.net

Its been a while since I've posted, but I've been doing lots of work around these shells and now ready to share some progress (bonus at the end).

What is strength?
First, lets talk about what shell strength means.
Because shells float on the drive systems; when we are talking about strength we are talking about impact strength, not structural strength.
Meaning you should really only be concerned with if dropping or hitting shells against objects will crack or break them in some way, and less concerned if strapping them to my own feet and doing jumping jacks for a few weeks without damage is possible.

So keeping that in mind; when we are talking about welding or brazing shell parts together for maximum strength, we are really talking about strengths far beyond our practical needs. However, like I said before I would explore all options and document it for you all, so lets begin:

Welding
People who wish to weld their shells together should know that welding aluminum is not easy, can be expensive (requires consumable argon gas), requires a jig for our shell shapes and you need skill. For me, I didn't have the time or money to invest into a proper TIG argon setup to weld these parts, and started to reach out to local welders in my area for quotes.

Here is what I learned from local welders, the price was steep (as I figured) but I learned it was steep cause the odd shape and number of parts these shells have requires a jig to hold the parts in place while doing the weld.

I never returned to my local welders who quoted me with a jig idea I had, but I did in fact go out and try to solution a DIY jig for others here who are experienced welders. The simplest jig I was able to build for my shells was one made with steel wire that loops around the dry fitted shell, through the side plate holes and twisted ends together tight in the middle / under shell. Do this two times on sides, and once down the middle until effectively you have built a wire cage around your shell holding it together during the welding process.

Brazing
Brazing is like welding, but is dedicated to aluminum and can be done with a simple propane torch and rod. Brazing requires you to heat up an area in question till the brazing rod's melting temp is met and you carefully melt the rod across the seam(s). On paper, brazing seems to be a perfect match for our application, however in practice issues come up.

Because we have so many parts to these shells, the idea of being able to heat up one or another area and hit all seams at once is not possible. So in order to do this, you will have to re-heat a number of areas which effectively will undo previous seams and exponentially makes the job harder as more parts get added.

As mentioned above, people who wish to still braze their shells might also find using thin steel wire to build a cage around your shell as a JIG a good approach but you have been warned.

Epoxy
JBWeld offers a steel version (red brand) of their metal joining epoxy that has a tensile strength of +5k. This is a two part epoxy that has actual metallic properties in their black steel part which helps create really strong bonds to metals. It requires you to put out two bead size drops of each part, mix to a light gray color and apply. Cure time is about 4 hours (fully in 24 hours), and you get about 40mins of wiggle room to make fine adjustments.

JBWeld requires no special equipment, no real skill and can be done in a small work area if needed. However JB weld will require a two part surface cleaning process and seams will need to be hit maybe more than once to first make a bond, and second to fill seams in as a filler build up.

As previously stated, our shell's practical strength needs really only requires them to not fall apart or break/crack on impacts and drops, not to be able to drive cars over them.

So going forward, I went with JBWeld Steel Brand (red brand) which I can confirm works great and extremely solid (yes I tested my own weight on them even). If you still want welds, but don't have the equipment you might find this route of doing shells yourself pretty expensive as you will need to outsource that welding to someone local. A cheaper route at that point is to buy them welded, sand blasted and carefully crafted in full from https://www.commandoeight.com/ankles-and-feet

Tools Required
- Metal file
- Steel Brush
- Painters Tape
- Acetone Cleaner
- Paper Towels
- Toothpicks
- JBWeld Steel Brand x2
- Duct Tape
- Razor Blade
- Drill with stepper bits
- Metal Square tool x2

The carts Devin setup for sendccutsend are here:
- Center Foot Shell Cuts (3mm/6061): https://cart.sendcutsend.com/vnfhbkm4xgne
- Outer Foot Shell Cuts (3mm/6061): https://cart.sendcutsend.com/vaumtlznhsjm

I also found the nested flat files for these and with some help we got the files already worked for xometry but had an issue on sendcutsend but are now working on this version.
INCHES REV5 TABBED 3 SHELLS-ajc.dxf
INCHES REV5 CURVED PARTS-ajc.dxf

Center Shell

Start off by doing dry fits of your center shell using tape to hold it all together. You will find some, if not most parts are a little tight and you will need to file down any of the rough edges of the tabbed connecting parts.

This process is fast, and should only require a swipe or two across each touching surface with your file: Next, we are going to work on the center shell's skirt.

Using a steel brush (picture has sand paper which also works, but steel brush is way better), we want to clean all our surfaces from dirt and the ever present oxide layer on aluminum.

Make sure to get sides and in tabs real well. Once you have scratched up the surfaces well its time to wash these scratches. Using a glass bowl (and a well ventilated area) pour out some acetone cleaner into the bowl and either directly dip parts into, or use paper towel to soak up acetone and wipe down the scratched surfaces well.

You will notice a lot of previously unseen black gunk come off at this step, keep cleaning till surfaces wipe nothing off. Next, put out two beads of JBWeld two part epoxy and mix the parts together until its a gray color. Using a toothpick apply a generous amount of JBWeld to the touching faces of front and back skirt plates and then slot all four parts together.

Tape corners together and use your two metal square tools to keep 90deg corners and parts square: Once the skirt has completed drying (least 4 hours), we move on to the skirt support triangles.

Begin by cleaning all the faces of these support triangles that meet with the faces of the skirt, as well as the skirt faces using our steel brush and acetone again. These skirt supports do not go on the bottom (narrowest point of skirt closest to the ground), but instead go up at the top of the skirt (widest point of the skirt furthest from ground).

So flip the skirt upside down (if not already), apply JBWeld to each triangle face, and while on a flat surface, drag the parts into each of the four corners of the skirt and let them dry.



Next lets work on the side plates.
Start by applying some duct tape to the plate across the cut line exposing the tabs we need to cut out: Next, with a towel between the plate and vice teeth, clamp the part in place and cut through each tab:

Once tabs have been cut through, we need to remove the duct tape and with our file smooth out the tab leftovers: Now carefully put the center plate back in place and try your absolute best to re-space/align these two parts from one another and then add back two pieces of duct tape again to keep that center part positioned. Great, next grab the inner-wall lip plate and begin cleaning the two parts with our steel brush. Focus on the overlapping lip where the two part's faces will touch rather than the whole plate: Wipe down the parts using acetone and clean the surfaces good: With surfaces clean, mix up some JBWeld and apply it to the lip plate. When applying JBWeld, make sure to apply it to the whole surface evenly with no gaps or light spots. Once JBWeld is applied, bring the two parts together and use bolts and nuts to hold them in place: With bolts in place, take two more pieces of duct tape and apply them in the same spots as the ones now, but now make sure to wrap it around tightly to the other side to assist at keeping the parts together while drying.

(I also apply a third piece of duct tape to the bottom to ensure its got a good contact all the way around.)

Now carefully (before done drying in the next 24 hours) flip the plate over and remove the nuts and bolts / peel away just enough of the tape to allow the center plate to be removed with a knife wedge so: Now grab a paper towel and clean out the inner part and now removed center plate: Once done cleaning, you can re-wrap the duct tape around the drying part and let it sit for a good 4 hours.

After this is done drying, remove the tape and begin cleaning the back surfaces where this inner lip plate now meets the outer wall plate:

Once cleaned up, lets mask off the inner lip / outer plate, leaving just the area we want to apply more JBWeld:
Once applied, I liked to wait a good 20mins before peeling the tape off to give the JBWeld a thicker consistency when peeling but to each their own. DO NOT wait till its fully dried to remove tape.

With that, you have completed one of the two side plates for center shell, so simply repeat these steps for the second side plate and then proceed.

Ok, once you have both center shell plates completed its time to move onto the shell ankle centers.
Start by drilling out the bolt holes for your center shell ankle walls to match the size bolt you will be using for your center leg:
Make sure to stop and test fit the bolt as you go, you don't want slop here but you also should be able to freely slide the bolt in and out:
Great, with the holes now drilled lets clean the ankle parts up with our steel brush and acetone once again and JBWeld our two walls:
In the pictures above I'm using them welder magnets simply as weights and then used my square tool to make sure every thing was squared up while drying. Its pretty important that these walls be as perfect to 90deg as you can get them while drying.

Great, with the two walls fully dried we move onto the center plate that connects these two walls:
Again start by cleaning the plate and then applying JBWeld to the faces that will meet:
Taking the center ankle plate from one of our outer foot shells, we can use it as tool to help square up these walls while this dries. Just make sure to check it on both sides and more than once while drying:

k, with the ankle completed and dried, we can now focus on the walls. However before you do so, you need to make an access hole on one or the other of our side wall's inner lip.

This hole should be the same size hole as we made in our ankle walls and done so prior to putting the shell together any further.

This hole should just barely be covered up by the outer plate once on, so keep checking as you go to make sure you have not drifted up too far.
I made the mistake of not realizing I needed this hole until after I had finished putting everything together.. silly me (aka don't do that!).

Start by re-bolting our side plates to our walls again:
Then begin cleaning all the connecting edges of all walls and newly finished top ankle using our steel brush an acetone. You really make sure these are clean at this part of the build:
Now with parts cleaned well, dry fit the walls together (using duct tape) and then tape it down on three sides to your work surface:
Great, now with the one side that is not taped down to your work surface, carefully undo the side tape to the point you can slip out the front or back wall:
Apply a generous amount JBWeld to the wall's faces that will touch with the side walls, and put the wall back in place:
Grab a paper towel and wipe down the excess really good:
Great, now re-apply tape to the side that needs to dry, and begin working on the opposite side. Once both front plate an back plate are JBWelded and taped back into place, go ahead and apply a good amount of JBWeld to the remaining top seams on the ankle:
Although not in the picture, I used masking tape once more before filling in the top ankle seams.

Next, we move onto skirt details.
Begin by cleaning the tab surfaces of the meeting corners and use a file if the tabs are too snug during a dry fit.
Next apply JBWeld to the two shortest detail plates and fit it all together and clean off the excess:
Using our square tools again, square up the corners as best you can and also apply 4 strips of tape at the spots you see in the picture below:
Finally, let this all dry and keep checking on the how square the corners are over the 4 hour dry period.

Once done (24 hour dry), its time to slip it onto our skirt and test fit it. I had to at this point really work at filing down any bumps or excess JBWeld on the inside of these four detail parts before I could get it all the way on to the skirt.

A target fit on the skirt is one where the detail is ever so slightly sitting above the skirt walls, not flush nor below; it needs to sit ever so slightly above support walls. If after filing and fitting you are nearly there, get a hammer and lightly tap the corners down till again the detail walls are slightly over the support walls:
Great, now take a marker and mark off the bottom of the skirt

Now pop off the skirt details (hammer lightly if needed) and using tape, mask off the area we don't want JBWeld to get on:
Now lets clean the inside walls of our skirt detail with our steel brush and more acetone. For this, we are not focused on the entire inside surface of each detail, but instead just the large spaces between holes all the way around. Once done cleaning, apply JBWeld to these cleaned spaces:
Finally, carefully slipping the skirt details back onto the support walls trying not to wipe the applied JBWeld to the tape until you again have the skirt detail walls slightly above the support walls again. Hammer corners will most likely be needed now if not before due to the JBWeld in place.

Now wipe down and clean off any excess JBWeld. Peel off the masking tape and apply some legal clips to keep the walls all touching while drying.
After about two hours of drying, get a toothpick and try and clear away any excess JBWeld found in the detail holes. Its important to do this before the JBWeld has completely dried or else its pretty hard to get that excess out of that small area, so do it while is soft like a clay (2 hour mark).

After the skirt has finished drying, its time to put together our top shell and bottom skirt finally.
There is nothing special here, you just want to clean each touching surface with our steel brush again, wipe it down with acetone really good and mask up the sides of the skirt and top walls with tape.
Once masked up, apply a really very generous amount of JBWeld to the top of the skirt, right into the crux of where skirt walls and detail plate walls make a v shape. You really want scrub the JBWeld into the skirt seam making sure that everything is really filled up and no hidden air bubbles are found.
Once you have a thick seam of JBWeld around the skirt top, take the shell walls and carefully place it on top of the skirt and adjust as you see fit. Once you like the fitting go ahead and clean up any excess JBWeld using a razor blade or paper towels. The idea ultimately here, or with additional applications of JBWeld is to build up a surface flush with the walls along this seam between top shell walls and bottom skirt, so using a razor blade here to flush things out is the best tool. Also, there is no need to wait till this dries before filling in these seams more and making flush with razorblade; if you need to squeeze out more JBWeld and do so now, I recommend doing it.

Great, and with that we let our nearly completed center shell finish drying.

Our last parts are the center shell side wall details and front back strips.

Before we begin cleaning these surfaces however, you will need to file down the edges of the center ankle's corners flush with the front and back plates:
With these filed down, lets begin cleaning our surfaces with our steel brush and acetone once more. You will want to apply JBWeld to the detail parts, not the shell, and do so making sure all of the surface is covered in JBWeld.

Once JBWeld is applied, slip some properly sized bolts into the holes of the detailed parts and use them as a guide to line up everything as you carefully apply each part to the shell.
After about 30mins, go ahead and pull out the bolts and check / confirm once more holes are lines up and then put back bolts until fully dried.

Once fully dried, remove bolts and try to clean / fill holes in with more JBWeld and let dry:
And with that, you have finished joining all the center shell parts!

Once fully dried, remove bolts and try to clean / fill holes in with more JBWeld and let dry:
ooks ugly now, but I assure you the remaining work is to just finish building up and sanding down any seams with JBWeld or bondo auto putty, file the edges of front / back detail plates (see google images for reference) and paint with a zinc based boat motor primer (must be zinc primer) before sanding smooth and painting white.

Next up is our outer feet!

Last episode we finished getting the center foot shell all JB welded up.
Next we need to put together our outer foot shells.

First step I took was to put together the ankle walls (which is the same process as our center shell).

However before we do so, we need to prepare our ankle walls for our bolt size.

Remember we scratch up our faces, wipe with acetone, then apply JB weld... this is the way!

Next we work on the 90deg sides using the center plate. Like our center shell ankle walls, it's very important you get a 90 deg out of these sides as this is where our leg ankles will slip into:
Let dry, the flip over to work with wings on flat surface:
Next lets build up our access plate walls which is the same process as we did on our center shells.
Tape them up using duct tape, and while duct taped move over to a vice and hack out the tabs:
Clean the lips of the two plate faces that will meet using our wire brush and wipe down with acetone before applying JB weld:
Once JB weld applied, use bolts to hold / align the two plates as you join them together and let dry.
About 30 /40 mins after joining the two plates, un-tape and carefully remove inner plate to avoid it getting welded in there by mistake.

DO NOT LET THE INNER PLATE SIT THERE FOR THE ENTIRETY OF THE DRY PROCESS!

After these plates are done drying, it's a good time to apply your detail plates to the access plates, but do not install the main shell's front and back details plates yet, the comes later!

(Sorry I dropped the ball here, didn't get a picture of these, but it's the same process as applying detail plates to center shell's access plates)

While these detail plates are drying, lets focus on our shell skirts:
Once dried, we add our corner plates:
Next let's work on our skirt detail plates. Just like our skirt plates above, clean the corners, wipe down with acetone, apply JBweld and use our square tools to keep square.
Once the detail plates are dried we move onto apply more JB weld to the inner detail plates like so:
There is no avoiding a little mess here, but do try to lower the skirt details down evenly onto the skirt plates to avoid the JB weld making into the square holes of the detail plates. Just like our center shell, the addition of a gritty JB weld adds a layer between detail walls and skirt walls, so little tapping of a hammer to get it down all the way was required by me.
Clean off excess and then apply some legal clips around to keep faces touching and flush while drying:
Clean off excess and then apply some legal clips around to keep faces touching and flush while drying:
Just like our center foot, carefully removing one end plate at a time, apply JB weld and put back / tape up until all three sides touching faces are now JB welded.
Wow, making good progress so far!

Having allowed the shell top walls time to dry, we then move onto now joining these top walls and our also dried skirt walls. Scrub away, clean with acetone and apply a good helping of JB weld and simply put the top onto the shell skirt.
Grab the long shell battery box strip plate and use this to gauge the alignment of the top shell and skirt. This battery box strip plate should be 90degs to the shell top (straight up and down if you will) so make adjustments until this is 90 deg and then let the shell tops and skirts finish drying.

Nothing too special here, scratch the surfaces up, clean with acetone and apply JB weld. I used tape to keep it true 90 degs while drying.
Ok now comes the fun part.
Who is ready to bend some metal!!?

The next part we need to work on is the shell battery box plate which meets up against our now dried battery box strip plate. This needs to have a 3" curl bend (2.88" inner bend radius which comes to full 3" outer radius due to thickness of plate). I called a ton of shops in down asking if this bend is something they could do, all of which said no, they only do crease bends not radius or curl bends. Finally though, one shop let me know that the reason they don't do these is cause you can do this with a shop press at home. Which after digging around on the forums a bit actually does concur with another builder who got bends done in the past.

So, I immediately went down to my locate hardware store and forked out cash to get a 20 ton shop press:
2 7/8" (OD) steel pipe:
Two steel L bars:
Here is a full video on how I got my bends using my steel pipe, L bars and shop press.
If someone out there knows of a better / cheaper solution please do share!



Ok, so you have made it this far?
Excellent, let's get these curled plates on our shells and JB weld them in place.
Its ok if you have a minor gap at the top when JB welding your curled plates into place, I used clamps to join the faces together while drying.
Holy moly we are getting close!
Next is honestly the most grueling part (I know we just did shop press bends.. how bad could it be right?).

The curl walls are larger than the shell by about 3mm (see image below how edges overlap the shell walls):
I don't know if this is cause of a slip up of the files, or indeed it is supposed to be this way, but here we are. I had to use a file to take these sides down which I admit took a lot of time. This is also where I began filing down all imperfections and making sure transitions from one plate face to another plate edge were smoothed out.
After getting your faces and edges flush, it's time to apply the detail plates on the front and back:
Pay close attention to the bottoms of the outer feet shells, they have a 45deg angle from the front wall that needs to be filed down into place carefully after welding them to the shells. I say after welding them to the shells cause its much easier to see what you are filing 45 deg relative to vs. doing it before welding to the shell.

Next we need to focus on fillers! I understand others out there might opt to use something like bondo auto putty at this point to fill in these spots, however I opted to continue to just use more JB weld. Using a steady hand, time and a razor blade I was able to get all my edges filled in, sanded down and filled up again if needed.

While working on fillers I installed some 3mm x 10mm steel pegs that across all my access plates (both outer and center shells):
The pegs are to be flush with our plates, meaning we only want 3mm of the peg into the plates at all holes. However some holes of the plates are 6mm deep due to having detail plates. On these 6mm holes I used a bolts and screwed them into the correct depth so that my peg was 3mm across all installed holes.
After these have dried, I filled the holes on the front side:
The filler steps are not a quick process using JB weld, but does help ensure even more tensile strength across the whole shell.
This is pretty much where you want to fill up any and all imperfections so really REALLY make sure you are happy with how flush everything is sanded smooth.

But, this is the internet so like magic we move right along like that only took a few seconds:

Ok builders, getting closer now!

After all our filler work is done, it's time to apply some zinc chromate primer to our shells. This stuff is intended to be for boat motors (also aluminum) so its zinc based solution is proven to bond to aluminum really good. If you don't use this stuff, your paint job will forever be subjected to scratching off super easy... as in REALLY easy.

Before we get to using this zinc chromate primer, you REALLY want to clean the shells. Using scotch bright pads, take your time at really scratching everything up clean. Using acetone clean the surfaces off until you don't wire off any more black gunk. I can't stress how important it is to get these shells clean before apply the primer.
Ok, now you have shells clean, put on some gloves and a respirator mask:
If you don't have gloves and a respirator mask you don't get to paint. This zinc chromatic pain is VERY dangerous to your lungs.. like WAY more than any average paint.. DO NOT.. I REPEAT DO NOT PAINT WITH THIS PRIMER WITHOUT WEARING A FULL PAINT MASK (PAPER MASK WON'T WORK!).
I personally found it funny the primer is olive green.. it makes R2 look like he is about to be recruited to the army.
The primer comes out gritty, and even has a tendency to get clogged. If you get a clog, you can take the spray head off and let it sit in acetone for a bit and then clean it out with a push pin or needle.

Once our shells have had two coats applied and fully dried, you will notice the surfaces are going to be REALLY rough. Using some fine sand paper and again our mask, sand down our shell faces so the primer is smoothed out. Don't go down to the aluminum, but do try to get this to be smooth as our next step is to apply our white paint coats.
Next we have a set of 10mm x 3mm master magnets (3mm hole) and will be used to complement our 3mm steel pegs in keeping our shell access plates locked into place on our shells during operation. These master magnets are perfect cause they not only do the job REALLY well, but the magnets are very discreet from the outside once the plates are off.
You want to clean both surfaces before applying JB weld, and apply the JB weld to the master magnets. This process can be a tad messy as the JB weld is a semi-ferrofluid and will try to apply to the edges of the magnet, but using a toothpick apply even coat to the magnet and attach to the inside walls of your shells:
Use the access plates / pegs to align / hold the master magnets while they dry:
Ok builders, now comes the time to apply our white satin paint.

I applied two coats to the majority of the shells (letting dry full 24 hours between coats), with a third coat focused just on the inner ankle walls.
Next, I carefully and evenly used fine sandpaper to sand down the shell detail strips to be as smooth as possible. I then used aluminum tape to cut a strip and apply that super shiny metal look to our details trips.
And that's it; you have completed your shells.
Hope this helps builders out there!