- Load rating: 20 t per roller, no recirculation
Each 90 mm diameter crowned roller uses two rows of tapered bearings with a combined static rating of 196 kN. Four rollers carry 784 kN—enough for a 40-ton mandrel plus 5-ton carriage. Because rollers rotate rather than recirculate, there is no ball-to-ball collision, so dynamic capacity equals static; life at 2 m/s calculates to 96 000 km—well beyond the 20-year facility plan. Compare that with ball blocks where dynamic C is only 60 % of C₀ and you need six blocks to hit the same life. - Contamination immunity in a clean room
Carbon-fiber dust is abrasive but non-magnetic. A sealed recirculator would ingest particles and degrade in 2 000 km. The rail-with-roller design mounts the rollers above the rail; gravity plus a stainless scraper shunts dust away. Particle counts inside the envelope remain within ISO 5 limits, eliminating the need for positive-pressure bellows that cost $12 k per axis. - Rail straightness ≤0.3 mm over 10 m—without grinding
The 100 m runway uses 10 m flame-cut segments stress-relieved at 620 °C. After finish milling, cumulative straightness is ≤0.3 mm; the 3 mm crown on each roller absorbs the error so the carriage floats without bind. Installation tolerance is ±1 mm vertically, ±2 mm laterally—coarse enough to mount on a standard concrete floor anchor pattern. Laser trackers confirmed positional repeatability of ±0.25 mm over the full 100 m, adequate for the ±1 mm autoclave pickup window. - Zero grease, zero sparks
Aerospace forbids lithium grease because out-gassed hydrocarbons contaminate composite pre-preg. The rollers run dry on a PTFE-impregnated raceway; break-away torque is 18 Nm per roller, rising to 22 Nm at full load. Coefficient of friction 0.007—half of steel-on-steel slide ways—so a 3 kW servo motor accelerates the 45-ton mass at 0.2 m/s² without help. - Thermal growth handled by floating rail
The clean room holds 23 °C ±1 °C, but the autoclave hall cycles to 35 °C. A 100 m steel rail grows 12 mm. The design fixes one end and floats the other on Teflon-lined shoes; the roller carriage simply follows the rail, so no axial stress transfers to the building frame. A magnetic tape scale mounted alongside the rail compensates thermally in the servo drive, holding final positioning within ±0.1 mm. - Maintenance interval: 10 years, visual only
After five years and 120 000 km, roller bearings still show <0.02 mm axial play—below the 0.1 mm replacement threshold. The only scheduled task is annual visual inspection and a wipe-down with isopropyl alcohol. No grease lines, no injector pumps, no quarterly PM sheets.
Key takeaway
A rail with rollers scales all the way from granola bars to 40-ton airplane wings when you match roller capacity to static load, crown the wheels to swallow rail straightness and keep contaminants out by geometry instead of seals. The payoff is not just lower purchase price—it is the elimination of maintenance inside expensive real estate like clean rooms or autoclaves.
A rail with rollers scales all the way from granola bars to 40-ton airplane wings when you match roller capacity to static load, crown the wheels to swallow rail straightness and keep contaminants out by geometry instead of seals. The payoff is not just lower purchase price—it is the elimination of maintenance inside expensive real estate like clean rooms or autoclaves.
Need rollers sized for your mega-load? Punch mass, speed and acceleration into the tool at https://yhlinear.com/product; it returns the smallest roller diameter, required quantity and even the part number for the stainless scraper—no overkill, no surprises.
