What This Book Actually Is
The Mechanisms And Mechanical Devices Sourcebook is a supplemental reference for the Star Wars: Edge of the Empire RPG from Fantasy Flight Games. It covers droids, vehicles, heavy weapons, starship systems, and the mechanics for building or modifying equipment. It slots in alongside the core rulebook and the character guide, though it really only matters if your table is doing engineering work or playing characters who spend time under the hood of something. It is not a standalone product. If you hand this to someone who has never played Edge of the Empire, they will flip through it for about twenty minutes and put it back on the shelf. The system language assumes you already know what a Difficulty check looks like, what Force Points do, and how talent trees work. That is standard for FFG sourcebooks, but it still worth noting upfront so nobody buys it by accident.
Mechanisms And Mechanical Devices Sourcebook
Everyone searches for this exact title, so I am putting it here so the search engines stop wasting your time. The book runs roughly 144 pages. The layout is consistent with other FFG RPG sourcebooks — color-coded sections, stat blocks in boxes, tables across two columns. Some of the pages are mostly reference charts. The best use of the book comes from the chapters on custom gear creation and the droid building rules. The biggest mistake I see is when Game Masters pull this book out mid-session and start flipping through pages while the players wait. That kills momentum. The reference tables in the back are useful, but only if you have already decided which one you need. I keep the droid customization tables and the vehicle weapon hardpoint chart on my desk before the session starts. Everything else stays in the box. When you are building a droid for a player character, the process takes about ten minutes if you follow the book straight through. It takes about forty-five minutes if you start debating whether a Protocol droid should have access to weapons-grade programming. The rules are clear on this. Protocol droids cannot equip combat subroutines by default, but they can if the GM allows an exception during character creation, and that exception usually costs a talent point or a significant resource hit. I recommend enforcing that cost. Players will try to optimize past the intent if you let them.
For ship modifications, the book gives you a framework but not a complete list of every possible upgrade. That is intentional. The system expects you to adjudicate new modifications rather than wait for an official release. I have seen tables grind to a halt because someone wanted to install a modified hyperdrive motivator and the GM did not know the rules for that. The workaround is simple. Borrow the rating progression from an existing ship component and adjust the Cost and Difficulty values by one step. A Class 1 hyperdrive modification that was previously Class 2 stays Class 2 in game terms, but you charge double the credit cost and increase the Engineering check Difficulty by two. This keeps the book honest without inventing new mechanics on the fly.
Get the Full Details
The Droid Building Rules Are Where Problems Happen
I spent three sessions trying to build a modified AST-Medical droid for a player who wanted it to double as a field medic and a combat medics unit. The book lists the base AST medical profile, but the modification section does not account for dual-role specialization cleanly. I ended up splitting the droid into two separate skill specializations and gave it one full medical package plus a weak defensive programming package. It worked, but it took two hours to balance. If you are doing this for a low-level group, do not attempt a dual-role build. Pick one role and stick to it. The book works best when you are making straightforward variants, not hybrid designs. Another edge case is the skill override rule. The book allows certain droids to use alternative skills instead of their default programming, but the wording is vague about what counts as equivalent. I once had a player argue that an Astromech should be allowed to replace its Repair skill with Piloting because both involve mechanical systems. The rule text does not support that. Repair and Piloting are separate skill groups with different specializations. I denied the request and pointed to page 67 of the sourcebook, where the specialization chart clearly separates them. That conversation ended quickly after I showed the chart.
Vehicle and Ship Modifications
The vehicle chapter is dense. There are hardpoint charts, mounting templates, and compatibility tables that overlap in confusing ways. The ship chapter is better organized but less comprehensive. If your game involves space combat regularly, the sourcebook will save you hours of homebrewing. If your campaign is ground-focused, you will barely open that section. One thing the book gets right is the weapon synchronization rules. When you mount multiple weapons on a single platform, the targeting system must coordinate fire. The book gives you a clear table for how many weapons can be synced based on the platform's size class. Beginners often miss this and try to mount six heavy laser cannons on a Landspeeder. The book will tell you that is impossible without a Size Class increase, and the Size Class increase requires a corresponding boost to the power plant. That chain of dependencies is easy to forget during character creation. Write down each step as you modify a vehicle. Do not rely on memory.
What This Book Does Not Cover
There are gaps. The book does not include rules for cybernetics. That belongs in the character sourcebook. It does not cover Force-sensitive equipment. That is handled elsewhere. It does not provide adventure hooks or pre-built scenarios. If you want ready-to-run content, this is not the book. It is a toolbox, not a campaign. I have seen new GMs complain about this, but it is the same structure as every other FFG supplement. The expectation is that you use the tools to build your own content. Another limitation is the credit economy. The book provides price tables, but those prices assume a relatively stable galactic economy. If your campaign takes place during active warfare or in a lawless sector, those prices are wrong. I adjusted all vehicle and droid costs by thirty percent upward during the Outer Rim campaigns I ran, and downward by twenty percent in Core World settings. The base numbers are fine for a Corellia-based game. They fall apart in the Slice or the Outer Rim Territories.
Where To Get It
You can find the Mechanisms And Mechanical Devices Sourcebook on DriveThruRPG as a PDF, and in print from most major RPG retailers. The digital version is around thirty dollars. The print version runs closer to fifty. If you are buying used, expect to pay between fifteen and twenty-five dollars depending on condition. I recommend the PDF unless you plan to reference the book frequently during sessions. The paper copy is heavy and the binding does not lay flat, which makes it frustrating to use at a gaming table. I keep mine on a tablet and flip through the PDF between scenes. If you cannot find it, the title is sometimes listed as part of the Edge of the Empire Enhanced Edition bundle. That bundle includes the core rulebook, the agent companion, and this sourcebook together at a discount. It is worth checking if your group is starting fresh.
Bottom Line
The book is useful. It is not essential. If your table plays droids, builds vehicles, or modifies starships, keep it open on the table. If your game is mostly social and diplomatic, skip it. The rules inside are solid, the price is fair for what you get, and the reference tables are accurate. Just do not expect it to solve problems that belong in other books. It is a mechanical reference, not a narrative guide. That is the only expectation that consistently causes disappointment.
