Rig Zero / Design Gate 02

Detailed design and procurement

A quote-ready specification for safely characterizing one magnetic wheel and drive module. A user-designated qualified reviewer recorded an internal review for controlled RFQ issue. This is not an independent approval. Supplier selection, purchase, fabrication and bench evidence remain open gates.

Internal review: controlled RFQ issue (not an independent approval)Internal review recorded — not an independent approvalRFQs not yet issuedNo purchase or test authorization

Preliminary Load Case

Selection target

Full crawler target mass15 kg maximumStatic weight147 NFour-wheel equal share36.8 N/wheelPreliminary safety factor3.0 minimumUneven-load allowanceUse 50 N/wheelRig Zero retention target≥150 N/wheel

Planning calculation only: 15 kg × 9.81 m/s² = 147 N; conservative 50 N wheel share × 3 = 150 N. Dynamic loads, gaps, coatings, curvature, impacts and tether loads require separate analysis.

Motor Target

Drive requirements to solve

  • 24 V nominal brushless geared drive with encoder preferred.
  • Wheel speed target: 0–0.15 m/s for inspection control.
  • Hold position without uncontrolled rollback on approved surfaces.
  • Controller must report current, speed and faults.
  • Thermal limits and duty cycle must come from the selected motor/gearbox data.
  • Brake or non-backdrivable strategy requires analysis; magnetic adhesion is not a brake.

Candidate Selection Matrix

Research leads—not approved suppliers

Magnetic wheelCustom permanent-magnet assembly quoted against ≥150 N target, working gap, coupon thickness, coating, curvature, temperature and shaft interface.RFQ first
Motor familyCompact flat BLDC with encoder and appropriate gearbox; Maxon EC-flat documentation is a comparison reference, not a final selection.Size from torque
Load cellTension/compression cell sized so expected force sits in a useful portion of calibrated range; FUTEK LCB200 is a form-factor reference, but 1000 lb may be unnecessarily large.Range review
Existing systemsNexxis BIKE, IMB Explorer and MAGNI demonstrate magnetic-wheel, modular NDT and remote-inspection architecture.Benchmark only

Fixture Architecture

Guarded force and motion rig

Remote controls
E-stop / isolation→Motor controller
current / encoder→Wheel module
guarded carriage→Steel coupon
known surface→Load cell
calibrated evidence

Procurement Gate

Before any purchase

  1. Mechanical reviewer confirms load cases and fixture concept.
  2. Safety reviewer closes guarding and isolation requirements.
  3. Send identical wheel RFQ package to at least three capable suppliers.
  4. Receive holding-force test conditions, drawings, tolerances and magnet material.
  5. Select load-cell range after expected test loads are signed.
  6. Verify motor/gearbox continuous torque and radial-load compatibility.
  7. Record lead time, warranty, country of origin and replacement availability.

Decision Rule

No single catalog number is “the answer”

Choose the lowest-risk combination that meets the documented load case with testable margins. Reject any quote that states holding force without steel thickness, surface gap, pull direction and test method.

Pass Complete data, compatible interfaces, traceable testsClarify Promising but missing a required conditionReject Unsupported force claim or unknown safety boundary

Engineering Review Files

Prepared for independent review

Review packageScope, disciplines, questions and gate decision. Available on request.Calculation recordPreliminary 150 N basis and unresolved load cases. Available on request.Reviewer invitationDraft request with response fields. Available on request.Review agendaProposed sequence and decision boundaries. Available on request.Review signoffBlank decision record for named reviewers. Available on request.Controlled project recordMachine-readable status and evidence boundaries. Available on request.

Controlled RFQ Package

Drafted—not issued

Draft cover letterCommon non-binding supplier request. Available on request.Wheel RFQ requirementsInformation every supplier must answer. Available on request.RFQ issue logThree blank supplier records marked not issued. Available on request.Component matrixCandidate categories and required evidence. Available on request.Bid evaluationCommon weighted comparison structure. Available on request.Procurement checklistApproval and receiving controls. Available on request.Test-data templateRepeatable future test-record schema. Available on request.

These documents enable a controlled next step. They are not reviewer approval, supplier contact, a quotation, an award, a purchase order or test evidence.

Official Manufacturer References

Benchmarks used for this gate

Nexxis BIKE platformIMB ExplorerMaxon EC-flat referenceFUTEK load-cell reference