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FTC transfer builder

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Arrow keys move a focused axle one grid step. Enter opens it in the editor, Escape closes the editor.

Results

Axles

Wheels and rollers

Belts

Gears

Method and sources

Speed through a stage

A belt keeps the direction of turn and a gear mesh reverses it. Either way the speed changes by the tooth ratio, with T1T_1 teeth on the driving side and T2T_2 on the driven side:

n2=n1 T1T2n_2 = n_1\,\frac{T_1}{T_2}
n2=− n1 T1T2n_2 = -\,n_1\,\frac{T_1}{T_2}

The first is a belt, the second a mesh. Every part on an axle turns with that axle, so a wheel turns at its axle's speed.

Ratio and torque

The ratio of an axle is motor speed over axle speed. With no losses, torque grows by the same number:

R=nmotornR = \frac{n_{\text{motor}}}{n}
τ=R τmotor\tau = R\,\tau_{\text{motor}}

Every real belt and gear stage loses some of that, so read the torque column as a ceiling.

Surface speed

A wheel of outer diameter DD in millimetres turning at nn rpm moves its rim at

v=πDn60v = \frac{\pi D n}{60}

millimetres per second. The motor speed is its free speed times the running percentage, so set that under 100 to model a motor working under load.

Belts

Each belt runs the belt calculator's exact length on the spacing you dragged, then picks a stocked belt by the same rule: the closest belt within your fit tolerance, otherwise the next longer one. Snap moves the driven axle to the spacing that belt runs at, found by the same Newton solve.

Under 6 teeth in mesh on the small pulley is flagged, because Gates derates a belt below 6.

Gear spacing

Two gears of module mm mesh at

C=m (T1+T2)2C = \frac{m\,(T_1 + T_2)}{2}

With a module on both gears and the lock on, dragging either axle swings it round the other at that spacing. Without a module the pair sets a ratio only, and the diagram draws the pitch circles your spacing implies, at m=2C/(T1+T2)m = 2C / (T_1 + T_2).

Loops

Speed spreads out from the motor one link at a time. A link between two axles that already have speeds closes a loop. If both paths give the same speed the loop is only redundant. If they disagree the train cannot turn, and the link is marked in orange. Three gears meshed in a ring always disagree, since each mesh flips the direction.

Motor speeds

The motor list holds the free speeds the drivetrain calculator uses, each traced to a vendor page in its research notes. goBILDA's cartridges are listed at the output speed goBILDA prints for each one. For anything else, pick Custom speed.

Grid

The 8 mm grid is goBILDA's hole pattern. A dragged axle lands on the grid, arrow keys move a focused axle one grid step (1 mm with the grid off), and the X and Y fields take any value.