How do you calculate usable torque capacity?

Multiply torque per rotation by available rotations for gross capacity, then multiply by uptime and first-pass effectiveness. With 4 units/cycle, 480 cycles, 90% uptime and 97% effectiveness, gross is 1920 units and good capacity is 1676.16 units.

What is the difference between gross and good torque capacity?

Gross capacity (1920 units) assumes the drive never stops and every rotation is productive. Good capacity (1676.16 units) is what remains after 192 units are lost to downtime and about 51.84 units to below-standard first-pass boring.

What is a good uptime for a TBM main drive?

Utilisation varies widely, but 40 to 60% shift utilisation is common on hard-rock drives once you count all stops. The 90% here is a drive-availability figure for the boring window itself, not whole-project utilisation.

Why does first-pass effectiveness matter for torque?

If cutters skate, clog, or leave the face uneven, some torque work has to be repeated or corrected. At 97% first-pass effectiveness you lose roughly 51.84 units of capacity to that rework across the window.

How can I raise good torque capacity?

Cut downtime losses (better maintenance scheduling raises the 90% figure) and improve first-pass effectiveness with correct cutter selection and thrust control. Both act as multipliers, so gains compound.

Does this account for cutter wear over the window?

Not directly. It assumes a constant torque per cycle. If cutters degrade sharply mid-window, lower the per-cycle figure or split the window at the planned cutter-change point.

Tunnel Boring & Heavy Civil Equipment calculator

Torque Capacity Calculator

Torque capacity here estimates how much usable cutterhead work a tunnel boring machine can actually deliver across a boring window once you discount downtime and rework. TBM engineers and drive planners use it to check whether the main drive can push the required advance through the expected ground before a maintenance stop. Gross torque capacity is what the machine could do if it never stopped and every rotation was productive; the good capacity is what you truly get after uptime and first-pass losses. Sizing this correctly is the difference between hitting a ring-per-day target and stalling in hard rock.

What this calculator does

Estimate torque capacity for tunnel boring and heavy civil equipment using production-ready inputs so teams can confirm whether capacity can cover demand before committing the schedule.
Use it when torque capacity in tunnel boring and heavy civil equipment is being asked to take on more work and you need to know if there is room.
It multiplies torque delivered per rotation by available rotations to get gross capacity, then discounts it by drive uptime and first-pass boring effectiveness to yield usable capacity.

Formula used

Gross torque capacity = torque capacity output per cycle × available torque capacity cycles
Good torque capacity = gross capacity × expected torque capacity uptime × expected torque capacity first-pass yield

Inputs explained

Cutterhead torque delivered per rotation:
Available cutterhead rotations in the window:
Drive availability (uptime):
First-pass boring effectiveness:

How to use the result

Use it when checking whether the main drive can deliver a target advance across a shift or window given realistic availability and ground-driven rework.
It treats torque per cycle as constant, but real cutterhead torque swings hard with ground class, groundwater, and cutter wear, so use conservative inputs for mixed-face conditions.

Current U.S. benchmarks

Steel mill PPI stands at 348.53 (BLS, May 2026), up 6.7% from a year earlier. New factory orders are up 2.3% year over year (Census).

Common questions

How do you calculate usable torque capacity? Multiply torque per rotation by available rotations for gross capacity, then multiply by uptime and first-pass effectiveness. With 4 units/cycle, 480 cycles, 90% uptime and 97% effectiveness, gross is 1920 units and good capacity is 1676.16 units.
What is the difference between gross and good torque capacity? Gross capacity (1920 units) assumes the drive never stops and every rotation is productive. Good capacity (1676.16 units) is what remains after 192 units are lost to downtime and about 51.84 units to below-standard first-pass boring.
What is a good uptime for a TBM main drive? Utilisation varies widely, but 40 to 60% shift utilisation is common on hard-rock drives once you count all stops. The 90% here is a drive-availability figure for the boring window itself, not whole-project utilisation.
Why does first-pass effectiveness matter for torque? If cutters skate, clog, or leave the face uneven, some torque work has to be repeated or corrected. At 97% first-pass effectiveness you lose roughly 51.84 units of capacity to that rework across the window.
How can I raise good torque capacity? Cut downtime losses (better maintenance scheduling raises the 90% figure) and improve first-pass effectiveness with correct cutter selection and thrust control. Both act as multipliers, so gains compound.

Last reviewed 2026-05-12.