It should be noted that these are the OFFICIAL versions. Local armorers often converted guns on their own, and you see much variation.  If you do a Google search, you'll find a lot of variations.

This works to your advantage.  You can make minor changes in the design to make your replica easier to construct, and it won’t necessarily be wrong.

For the reenactors and the cosplayers, I regret to say I’m not covering the Infantry Lewis in this document.  However, that big cooling jacket is probably fairly easy to do with PVC pipe.  What I call the "Barrel Holder" (see the construction section) can have the bracket "ears" taken off and can be resized to fit inside an available size of pipe (probably the 3" inside diameter type).  

The stock will be more difficult.  I have made stocks like this using a sandwich of wood.  The width of the Lewis at the stock interface is 1.5 inches.  Take a 1/2” piece of pine, glue a 1/2” piece of balsa to either side, and start carving and sanding.  It’s really not that hard.

Replicating the Lewis Gun

There are several factors involved in replicating the Lewis Gun. The primary one is the desired accuracy.  You have to decide if you're looking for "20 Foot", "10 Foot," "Five Foot," "Three Foot", or "Hands On" accuracy.

A "20 Foot" Lewis gun will look real to an observer 20 feet way, a "10 Foot" one at ten feet, etc.

However, this does depend on the KNOWLEDGE of the observer.  Someone who KNOWS Lewis Guns will be able to tell that a "Ten Foot" replica is wrong, even twenty or thirty feet awa

When I make replicas like this, I shoot for "three foot" accuracy...basically for a visitor to step into my home office, see the replica perched there, say, "Holy S***!"...then, depending on their background, they notice the discrepancies as they come closer.

Now, SHAPE-wise, I think my Lewis replica is pretty good.  But you can easily take my design and "hyper-detail" it...add features that make it more and more realistic.

There are a couple of companies out there who cater to Lewis replica builders.

The Replica Plans company sells Lewis Gun plans (which include CAD files) for just $10.  The pictures they have on their web page shows an excellent model.  I actually found this site AFTER starting my own replica...I probably would have bought the plans.

The second replica is done by Foxflier.  They sell ABS-plastic kits of the Infantry and aircraft Lewis Guns.  The full kit is only $140.  They even have a 7/8ths scale version to go with the 7/8ths scale CIRCA Nieuports.

So...why did I design my own?

I wanted something in between these two products.  The Replica Plans version would require a lot of metal working that I wasn’t capable of.  The Foxflier one is a five-to-ten foot model; it looks good on the wing of a Nieuport, but the ABS molding softened the edges of everything.  The picture on the right shows the housing for the tension spring for the Lewis, with the little "dial" that is used to keep the spring tight.  The dial is a separate piece...but notice how the molding just blends it into the rest.

I'm not knocking the Foxflier kit.  A lot of folks have done very nice guns from them, nothing keeps you from adding hyper-detail.
 
But I wanted a replica with sharp edges that would still look (pretty) real from just a couple of feet away.

So I started building my own replica from wood.  But I bogged down after a bit.  There are a lot of fine, fiddly-bits that go into making an accurate replica.  And these were difficult/time consuming to do by hand, out of wood.  I realized that I wouldn’t be able to get the kind of detail I was looking for, and set the project aside.

Then, right out of the blue, my wife gave me a 3D printer for Christmas.

Here was a way to DO those little fiddly bits.  I’m a member of the Experimental Aircraft Association, and one member perk is the educational version of Solidworks, a very powerful CAD (computer-aided design) tool.  If you’re buying a copy outright, Solidworks costs $10,000…yet, as an EAA member, I could download a free copy!

So I started teaching myself Solidworks, which was kind of a slog since it’s a professional tool, not designed to molly-coddle ordinary mortals.  As I got better at it, I realized that more and more of the Lewis Gun design could be printed on my Epson 3D printer.  I replaced several parts I'd already made from wood with 3D-printed versions.

Unfortunately, there were some limits.  My printer could handle objects only ~7” or so in length, and many parts of the Lewis are longer than this.  But… most of the big pieces were pretty simple, so I could still do them in wood.  Or do them with the 3D printer in two parts.

The picture to the right illustrates the issue.  These are the components that fit at the end of the receiver where the gas tube and barrel emerge.  You can see the simple wood version I did…next to the version generated by the 3D printer.  The vertical shelf would have had to have been a piece of 1/4” wood glued to the base piece.  The 3D version is much, MUCH better, especially as I was able to quickly change the design as research showed what the actual piece looked like.

And it was a LOT easier to re-do parts when I found errors.  The shelf on this receiver end was too long.  I went back into Solidworks, edited the part design, sent it to the printer, and had a new one in a bit. 

A similar mistake in wood might not have been too difficult to fix.  But imagine finding, for instance, that the two holes had the wrong spacing?  The whole part would have probably had to have been scrapped.  Instead of just making a minor change on the computer, and re-printing it out.

So...ultimately, how accurate is my design?

Dimensions, etc. are pretty close.  I have an image of an original Savage Arms three-view drawing, which I imported into a image tool and resized so I could directly determine the sizes and shapes of various components.
 
Otherwise?  Well, I’ve taken a lot of liberties in the name of making the replica easier to build.  Primary variations have to do with the surface detail on the receiver, the main body.  I’ve taken some short cuts there.

MOST people who see your replica, or the pictures of it, won’t be able to tell the difference.

If some aspect bugs you…well, then crank up Solidworks and fix it.  That’s the beauty of this project; it generates a good base for doing some fine detail.  For the Solidworks
design I posted, the receiver is just a simple 1"x2"x11.5 block of wood...but two side-pieces are attached.  These side-pieces implement the surface detail I made in wood for my model, but you sure can modify them if you wish!

Safety

I need to mention a few things about safety.

First, I designed this gun to sit on a shelf on display, NOT on the upper wing of an aircraft.  If it’s going on an airplane, you need to make sure that your version is strong enough to go to the aircraft’s redline.

My version uses a short 1/4” threaded stud to hold the ammunition drum in place.  This is, especially, NOT adequate for aircraft!

When I was assembling the replica, I set it on the rear handle  I had to apply some pressure to get a screw started… and the lower part of the handle broke.

If you’re going to put this on an aircraft, it’s your responsibility to ensure it’s airworthy.

Second, understand:  To your local police, there ARE no fake wooden machine guns.  If you, just for a joke, strap one of these to the hood of your car and go for a drive on Saturday night, you will likely be met by a SWAT team. 
Cops WILL assume your gun is real, and react accordingly.  I know people this has happened to.

You’re not likely to trigger such a reaction if you’ve got the correct historical context…the gun on the wing of your airplane, or you and your friends in WWI uniforms or at a Star Wars convention (notice many convention sites ban weapons, though, even fake ones). 

Otherwise, I highly recommend you keep the replica out of the public eye.  In addition, there are some countries that ban replicas like this, even non-firing ones.

Make no mistake:  This is NOT a real machine gun.  It’s made of wood and plastic, and can’t even chamber a bullet, much less fire one.

But you always have to be aware of people’s perceptions.  The above picture was taken in my garage with the door closed.  I took the replica to the airport and took another picture of it on the wing of my airplane.  I had the door closed to set up the photo, then opened the door for (literally) two minutes to take the picture.

So BE CAREFUL.

On 3D Printing

One thing to be aware of is that the typical 3D printer is going to take a LONG time to print these parts.  The Barrel holder alone took 14 hours.  Most parts took, typically, 4-8 hours.  Even as I write this, my printer is cranking out the back end of a Flash Gordon spaceship ~6 inches long...and it's going to take nine hours.

So if you and a couple of buddies decide to chip in together and build several guns…well, it’s going to take a while.

If your printer has a “Generate Support” function, you’re probably going to need it.  The most common type of printers can’t directly print things unless they are propped up while printing.  Think of printing a bolt, with its head up.  The printer can’t print on air, when it’s trying to print the bottom of the bolt head.  So you have to enable the Generate Support function so it adds lightweight struts to hold things up.
 
When you get done, this can be a bit dismaying.  You see a blob of plastic, not the finely detailed part you expected.

It’s in there…it’s just buried behind a batch of temporary struts.  If you start picking at it with the point of a knife, these temporary supports pop out.  It’s not 100% perfect, but I’ve been impressed at the quality of some of these pieces.

Speaking of quality, Solidworks does take a shortcut to avoid drawing smooth curves.  What will happen is that you’ll get a part out, and what should be a smooth edge has facets…little flat areas that join together.

In Solidworks, click the “Option” button (the button at the very top that’s shaped like a gear) and select the “Document Properties” tab.  Click the “Image Quality” option.  Move the top slider all the way to “High.”

When you’re combining 3D printing and standard wood parts, things can sometimes get a bit weird.  Do test prints if you’ve got somewhere with a tight fit.  The sizes of the wooden dowels can vary a few thousandths from the "nominal" one-inch, and might not slip onto your printed parts as well.

But I don't have a 3D Printer!

This makes doing the parts harder.  :-)

However, you can still use Solidworks to generate dimensioned drawings, if you wish to  scratch-build all the parts.  There are companies that will take the digital parts and print them for you, but of course, that's likely to be costly.

Construction

The figure below shows what I call the various portions of the replica.  The “Main Body” is the receiver, the “Barrel” is above the “Gas Tube”, the Top Plate supports the drum (not shown) and includes the base for the main sight.  The Hand Grip includes the trigger, and the “Spring Housing” with its wind-up dial set right in front of it.

The “Barrel holder” slides over the spacers.  It butts up against the shelf coming out of the receiver.  The end surface of the spacers is just slightly inside the holes in the Barrel holder.  The both spacers have 1/4” holes in the end to take a dowel.  The barrel and the gas tube include matching holes, and they epoxy to the ends of the spacer.  You might have to shave the barrel or gas tube slightly to get it to butt up to the end of the spacer, if the dowel holes in the middle are slightly off.

The Barrel Holder includes a provision for a countersunk #6 screw between the flanges at the bottom.  The screw runs through the holder into the gas tube spacer.  Those longer flanges are the main attachment of the replica to the mount, by the way.

You’ll note an item called “Combined Fillet Rings”.  These provide a fillet for the tube spacer join with the Receiver End.  You could do this Bondo or similar, but this is easier.

Barrel and Gas Tube Spacer Construction

Now:  I made the barrel and gas tube spacers on a lathe.  I’ve included Solidworks models for these, so you can probably far more easily print them out than go buy a lathe.  If I were to build a second Lewis, I’d do it this way.

HOWEVER:  The attachment of the spacers to the body, and the barrel and gas tubes to the end of the spacers, is probably the most critical portions of the design, as far as the STRUCTURE are concerned.  The barrel and the gas tubes themselves attach to the spacers using short 1/4” dowel pins.

This is adequate for a ground display, or running around in trenches with re-enactors, or marching through a convention with your fellow cosplayers.  I am, though, skittish about this for replicas intended to be mounted to actual aircraft.

I think the turned wood versions are stronger than a 3D printed version would be…but you’re still stuck with the interface between the spacers and the tubes.  I think epoxy probably works better between the wood spacers and the wood barrels, vs. a plastic 3D printed spacer and the wooden barrel/gas tube.

If you’re intending to mount this on an aircraft, come up with ways of beefing up this interface.  Possibly use a 1/4” steel rod into the main body, through the inside of the spacers, and an inch or three into the barrel and gas tubes.

There are other options, too, which I’ll discuss in the next section.

By the way, these spacers and the barrel/gas tube require a hole drilled into the ends dead-center to take the dowel that connects them to the other portion.  There are three Solidworks “Drill Guide” parts….one for 3/4”, one for 1”, and one for 1 1/4”.  These are like stool caps.  They slide snugly over the end of the wooden dowels, and including teeny tiny hole dead center.  Use that for drilling into the exact center of the rods.

Barrel and Gas Tube

While I include a Solidworks version in the package, the “Gas Tube” is a 3/4” wooden dowel, and the barrel starts as a 1-inch dowel, tapered from one inch at the receiver end to 5/8th at the muzzle.

One of the classic features of the Mark III Lewis is that tapered barrel.  I love the look, and actually bought a small wood lathe specifically so I could taper a dowel to get that look (I’m always looking for an excuse to buy tools).  This figure shows the stock barrel system. By the way, see the nut at the base of the barrel?  Completely non-functional.  Just glues in place as a bit of additional detail.