REV vs goBILDA build systems

Most FTC robots are built mainly from one of two kits of parts: REV Robotics' DUO build system and goBILDA. Both are proven at every level of competition. They are built on different ideas, though, and nearly every "why won't this fit" moment in a mixed-parts bin comes from those differences.

REV DUO: extrusion first

Extrusion

An aluminium rail with T-shaped slots running its whole length. Screws slide along the slots, so a bracket can be fixed at any position, not just at pre-drilled holes.

• Structure: 15 mm × 15 mm aluminium extrusion with slots on all four sides, plus 15 × 45 mm C-channel and 45 × 45 mm U-channel for stiffer parts of the robot.
• Hardware: M3. REV's standard screw is an M3 hex-head cap screw, turned with a 5.5 mm nut driver, which slides into the extrusion slots.
• Hole patterns: brackets have M3 holes on an 8 mm pitch. The "motion pattern" is a ring of M3 holes on a 16 mm circle, used to mount shaft parts. Channel carries an extended version with 9 mm bearing seats every 16 mm.
• Shafts: 5 mm hex, stainless steel, cut to whatever length you need. Mostly plastic (Delrin) bearings, with ball bearings available for high-load or high-speed shafts.
• Power transmission: #25 chain and GT2 3 mm timing belts.
• Motors: the HD Hex motor with UltraPlanetary or spur gearboxes, and the smaller Core Hex motor.

The big advantage is adjustability: slide a bracket to tension a chain, nudge a gear into mesh, move a mechanism 5 mm without drilling anything. The cost is that nothing is pre-located. Lengths have to be measured and cut, and Game Manual 0 notes that parts on extrusion tend to loosen over time and the 5 mm hex shaft can bend if it is long.

goBILDA: the pattern first

The goBILDA pattern

4 mm holes on an 8 mm grid, with a 14 mm hole for a bearing and a ring of mounting holes around it. Almost every goBILDA part carries the same pattern, so parts line up with each other automatically.

• Structure: U-channel, 48 mm wide, plus thinner "low-side" channel and goRAIL extrusion when you want slide-and-fasten adjustability. Threaded parts such as goRAIL use goBILDA's 16 mm square pattern.
• Hardware: M4. goBILDA lists a 3 mm hex key for its M4 socket heads and a 2.5 mm key for its button heads.
• Shafts: 8 mm REX (a 7 mm hex rounded to 8 mm), also the output shaft of goBILDA motors, and 6 mm D-shaft. Mostly clamping hubs, so very few set screws.
• Power transmission: 8 mm pitch chain and 5 mm HTD timing belts (goBILDA also sells 2 mm GT2). Game Manual 0 notes that goBILDA's chain and belts land on correct centre distances on the pattern, so you rarely have to calculate them.
• Motors: Yellow Jacket planetary gearmotors in a wide range of ratios, from 30 RPM to 6000 RPM, which can mount directly to the channel.

The big advantage is that things go where they are supposed to: if the holes line up, the chain is tensioned and the gears mesh. The cost is that you can only put things where the pattern allows, so in-between positions need an adaptor, a slot, or goRAIL.

Side by side

	REV DUO	goBILDA
Main structure	15 mm extrusion + 45 mm channel	48 mm U-channel (+ goRAIL extrusion)
Positioning	Anywhere along a slot	On the 8 mm grid / pattern
Screw thread	M3	M4
Standard shaft	5 mm hex	8 mm REX, 6 mm D
Chain	#25 (1/4 in)	8 mm pitch
Timing belt	GT2 3 mm	5 mm HTD (also 2 mm GT2)
Motors	HD Hex, Core Hex	Yellow Jacket range
Strength	Extrusion is lighter; channel adds stiffness	Channel is stiff and strong
Learning curve	Steeper — more measuring and cutting	Gentler — parts line up

Game Manual 0 describes REV as slightly cheaper with a steeper learning curve, and goBILDA as a little more expensive but quicker to learn. Neither is "the good one." Teams win with both.

Mixing the two

Plenty of teams use a goBILDA drivetrain with REV electronics and a few REV parts on mechanisms, or the other way around. It works if you respect what can and cannot cross over.

Things that never interchange:

• Chain: #25 and 8 mm chain have different pitches. A REV sprocket will not run goBILDA chain.
• Belts: GT2 3 mm and HTD 5 mm differ in both pitch and tooth shape.
• Screws: M3 and M4 are different threads. An M3 screw rattles loose in an M4 hole, and an M4 screw will not go into an M3 hole at all.
• Shafts: a 5 mm hex shaft spins loose in an 8 mm REX bore.

Ways to bridge them:

• Pattern adaptors. goBILDA sells adaptors that bolt to REV's hole patterns on one side and present goBILDA's pattern on the other, plus motor mounts for REV motors.
• Pick one system per mechanism. Keep a drivetrain all goBILDA or all REV inside, and adapt only at the joint where two mechanisms meet. Mixing chain, shafts and hubs inside one mechanism is where the trouble starts.

Which should a rookie team choose?

Usually the deciding factors are practical, not technical:

• What you already own. Starter kits, donated parts and last year's robot are worth a lot.
• Who is mentoring you. A mentor who knows one system well is worth more than the theoretical advantages of the other.
• How your team likes to work. If you love adjusting and iterating at the bench, extrusion suits you. If you want things to line up without measuring, the pattern suits you.

Whichever you pick, learn it deeply. Knowing every part in one catalogue beats knowing half of two.

Check yourself

Your goBILDA drivetrain uses 8 mm chain. A teammate wants to swap one sprocket for a REV #25 sprocket they found in the parts bin. What happens?

• AIt works — sprockets are universal
• BIt will not work — the chain pitches are different
• CIt works if you add threadlocker to the sprocket
• DIt works but runs slightly slower

Check yourself

You need to tension a chain run and you are not sure exactly where the idler should go. Which build approach makes that easiest?

• AExtrusion, because the idler mount can slide along the slot until the chain is tight
• BA fixed hole pattern, because it is always exactly right
• CNeither — chain cannot be tensioned
• DMixing M3 and M4 screws in the same mount

Where to go from here

That is the mechanical track. You can now pick a drivetrain and gear it, size a lift or an arm with real numbers, and build all of it so it lasts. When you are ready to design your own parts instead of bolting kits together, the CAD track shows you how to model them first — starting with supplier part libraries.

Sources and further reading

• Game Manual 0 — Kit and Hardware Guide, REV Robotics and goBILDA
• REV DUO — Structure overview (extrusion, channel and the motion patterns)
• REV DUO — M3 Hardware, Sprockets and Chain and Timing Belts and Pulleys
• goBILDA — The goBILDA pattern
• goBILDA — Pattern adaptors (REV-to-goBILDA adaptors and REV motor mounts)
• goBILDA — 8 mm pitch steel chain and timing belts and pulleys
• goBILDA — Yellow Jacket planetary gear motors