Mechanic - Auto, Marine, Aviation

Tools in this group

• Marine Prop Slip - Theoretical speed, slip percent, and planing vs displacement category from RPM, gear, pitch, and GPS speed.
• Engine Displacement and Compression Ratio - Cubic inches / liters and static CR from bore, stroke, chamber, gasket, deck, and dome volumes.
• Bolt Stretch and Clamp Load - Clamp load from F = (stretch * area * E) / grip; cross-check torque.
• Driveshaft Critical Speed - Euler-Bernoulli first-mode critical RPM with safety-factor recommendation.
• Fuel Energy and Range - BTU and kWh from tank and LHV; range from tank * mpg * load factor.
• Tire Size and Effective Gear Ratio - rev/mi for old vs new tires, effective ratio, cruise speed, recommended axle ratio.
• Brake Pad Lifespan and Heat Capacity - KE per stop, rotor temp rise, wear per stop, estimated pad life by material.
• Valve Flow Coefficient (Cv) - Solve the liquid sizing relation Q = Cv x sqrt(dP / SG) for Cv, flow, or pressure drop; the gas / compressible regime is flagged. Per ISA-75.01 / Crane TP-410.
• Screw / Auger Conveyor Capacity - Volumetric capacity (ft^3/hr) from diameter, shaft, pitch, RPM, and trough loading, and mass rate from a bulk density. Per the CEMA Screw Conveyor standard (Book No. 350); loading fractions user-supplied per CEMA class.
• Horsepower from Torque and RPM - Horsepower, kilowatts, and a solve-for selector across HP, torque, and RPM via HP = Torque * RPM / 5252.
• Volumetric Efficiency and Airflow - Theoretical and actual induction CFM and volumetric efficiency from displacement, RPM, and cycle, with VE above 100% allowed for forced induction.
• Gear-Ratio MPH from RPM - Road speed (or RPM), wheel RPM, and tire revolutions per mile from engine RPM, transmission and axle ratios, and tire diameter.
• Machining Speed and Feed - Spindle speed (RPM) from surface speed (SFM) and cutter or work diameter, plus feed rate (IPM) from the number of flutes and chip load per tooth (first-principles cutting geometry; Machinery's Handbook speeds-and-feeds method).
• Drill Point Depth - Drill-tip allowance (point length) = (diameter / 2) / tan(point angle / 2) and the tip depth to reach a desired full-diameter depth, for 118 / 135 degree and custom drill points (first-principles drill-point geometry).
• Cut Time per Pass - Cut time per pass and total time from cut length and feed rate: feed_IPM = RPM x IPR (or entered directly), t = length / feed_IPM, total = t x passes (first-principles distance over feed rate).
• Material Removal Rate - Material removal rate (MRR) in cubic inches per minute for milling (WOC x DOC x feed_IPM), turning (12 x SFM x DOC x feed_IPR), or drilling ((pi x D^2 / 4) x feed_IPM) (first-principles swept-volume geometry).
• Theoretical Surface Finish - Theoretical turned surface finish from feed and tool nose radius: peak-to-valley Rt = f^2 / (8 x r) with an estimated Ra ~= Rt / 4, in microinches and micrometres (first-principles scallop geometry).
• Taper per Foot and Angle - Taper per foot, taper per inch, and the included and per-side angles of a taper from the large and small diameters and the length: TPF = 12 x (D - d) / L, angle/side = atan((D - d) / 2L) (first-principles trigonometry).
• Dividing-Head Simple Indexing - Simple (plain) indexing on a 40:1 (or custom) dividing head: crank turns per division = ratio / N, plus the exact full-turns-plus-holes setting for each supplied index-plate hole circle that divides evenly (first-principles ratio arithmetic).
• Roller Chain Length in Pitches (ANSI B29.1) - The even-link round-up and corrected center distance people skip: L = 2(C/p) + (N1+N2)/2 + ((N2-N1)/(2 pi))^2/(C/p) pitches. The count must come out EVEN -- an odd count forces a weaker offset (half) link -- so it is rounded UP, and then the center distance is recomputed so the chain fits with proper sag. A 17-to-51-tooth #40 drive (0.5 in pitch) at a 30 in center is 154.49 pitches -> 156 to order, with a corrected 30.38 in center (0.38 in of take-up the skipped step misses); pull the center to 20 in and it is 114.73 -> 116 pitches, 20.32 in corrected. Keep the center at least ~30 pitches for wrap. A design aid; the sprocket selection and take-up govern.
• Tap Drill Size - Tap drill diameter for a target percent of full thread on a 60-degree (UN / ISO metric) thread: % = 76.98 x (D_major - D_drill) x TPI, so D_drill = D_major - % / (76.98 x TPI), with the nearest 1/64 in fraction (the named letter / number drill is a chart lookup) (first-principles thread geometry).
• Spur Gear Tooth Geometry (Diametral Pitch) - From the diametral pitch Pd: pitch dia = N/Pd, OD = (N+2)/Pd, addendum 1/Pd, dedendum 1.25/Pd, whole depth 2.25/Pd, root (N-2.5)/Pd, center distance (N1+N2)/(2Pd). Pd 10, N 40, mate 20 -> PD 4.000, OD 4.200, center 3.000 in; a finer Pd 20 halves every dimension. A shop aid; the gear drawing and AGMA govern.
• Rolling-Bearing L10 Rating Life (ISO 281) - The cube law that punishes a bearing overload: L10 = (C/P)^p x 10^6 rev, L10h = L10 / (60 x rpm), with p = 3 for ball and 10/3 for roller bearings. A ball bearing (C = 5,000 lbf, P = 1,000 lbf, 1,750 rpm) lasts 125 million rev = 1,190 hr; a 25% overload to P = 1,250 lbf drops it to 64 million rev = 610 hr -- the cube law turns a 25% load increase into a 49% life loss, which is why a small alignment or belt-tension improvement pays off. Basic L10 assumes clean, well-lubricated operation (contamination needs the modified aISO life) and is the life at which 10% have failed, not the average. A planning estimate; the mounting, lubrication, and application govern.
• Countersink Diameter and Cutting Depth - Dialing a Z-depth when the print calls a diameter: the print gives the finished countersink diameter, but the machine is set to a plunge depth, Z = (D_cs - d_hole) / (2 tan(angle/2)). A 0.500 in countersink, 82 deg inch head, 0.250 in pilot hole needs 0.1438 in of plunge; the same diameter with a 60 deg tool needs 0.2165 in -- a shallower angle drives the tool half again as deep, so the angle callout matters as much as the diameter. 82 deg (inch flat-head) and 90 deg (metric) are NOT interchangeable -- mismatched screw and sink never seat flush, and a few thousandths of over-plunge sits a flat-head proud or buried. A setup aid; the tool geometry and the fastener callout govern.
• Shaft Key and Keyseat Size (ANSI B17.1) - The band-table width and H/2 depth machinists mis-read: ANSI B17.1 sets the standard key width from the shaft-diameter BAND, not exactly D/4 -- a 1 in shaft (over 7/8 to 1-1/4) takes a 1/4 in square key, cut to a 0.125 in (H/2) shaft keyseat depth (over-cutting off the full key height weakens the shaft). Key stresses: shear = 2T/(D W L), bearing = 4T/(D H L). At 1,000 in-lb over a 1.5 in key the shear is 5,333 psi and bearing 10,667 psi (both well under a steel key); but a key longer than the hub adds no capacity -- a 1.0 in hub sets the working length, raising shear to 8,000 psi. Square-key model; the allowables and fit class govern.
• Radial Chip Thinning Feed Compensation - The feed correction the speeds-and-feeds tile never makes: at a radial width of cut below half the cutter diameter, the chip is thinner than the programmed feed per tooth, so RCTF = 1/(2 sqrt((ae/D) - (ae/D)^2)) raises the feed to restore the intended chip load. At 10% radial engagement RCTF 1.667 (feed two-thirds higher); at half immersion RCTF 1.0, the crossover where compensation stops. The basis of high-feed and trochoidal milling, and the difference between a light pass that rubs and one that cuts. Radial thinning only. A shop aid; the tool maker's chip load governs.
• Boring Bar / Tool Overhang Deflection and L/D Limit - Why a long boring bar blows the bore and chatters: the tool is a cantilever, delta = F L^3/(3 E I) with I = pi d^4/64, and the L/d ratio sets the chatter risk (steel stable to ~4:1, carbide 6-8:1). A 0.75 in steel bar 6 in out under 100 lb deflects 15 mil (L/d 8, chatter territory); choke up to 3 in and it drops to 1.9 mil (the L^3 law) - the overhang, not the force, dominates, why 'shorten the tool' is the first fix. Static solid-round model, not a stability-lobe analysis. A shop aid; the tool and setup govern.
• Ballnose Milling Scallop Height from Stepover - The 3D-finish trade every mold toolpath makes, which turning-surface-finish never covers: a ballnose of radius R stepping over by s leaves a scallop h = R - sqrt(R^2 - (s/2)^2), or the inverse for the stepover that holds a target scallop. A 0.5 in ballnose at 0.030 in stepover leaves 0.45 mil; double the stepover and the scallop quadruples (the s^2 law) - a tighter stepover buys a finer finish at the cost of cycle time. Theoretical flat-surface cusp, not Ra. A shop aid; the real finish depends on the tool, deflection, and slope.
• Fuel Injector Size from Horsepower, BSFC, and Duty Cycle - The first spec of any engine build or boost upgrade, which the displacement and horsepower tiles never give: each injector must flow lb/h = HP x BSFC / (n_cyl x duty). A 400 hp V8 at BSFC 0.50 and 80% duty needs 31.3 lb/h (328 cc/min) per injector; add boost (BSFC 0.60) and it jumps to 37.5 lb/h - a 20% bigger injector for the same power, why a boosted build steps up injector size before adding power. Port injection, entered BSFC; not rail pressure or DI. A tuning aid; the measured fueling and the tuner govern.
• Mean Piston Speed and RPM-Limit Reading - Whether an rpm target is safe for the stroke, the single best predictor of reciprocating stress: MPS = stroke_in x RPM / 6 (ft/min), independent of bore. A 3.48 in stroke at 6,000 rpm runs 3,480 ft/min (street/endurance); rev to 7,000 and it hits 4,060 (performance) - and a longer 4.00 in stroke would already sit at 4,000 at 6,000 rpm, the trade a stroker accepts. Street builds stay under ~4,000, performance 4,000-4,500, race over 4,500. Average, not peak; guidance bands. A shop aid; the component ratings govern.
• Horsepower from Quarter-Mile Trap Speed - The dyno-free power check a racer runs off the timeslip: Hale's HP = weight x (mph/234)^3 inverts the quarter-mile trap speed to horsepower. A 3,200 lb car trapping 108 mph made 315 hp at the wheels (companion ET 12.6 s); a 7 mph faster trap (115 mph) implies 380 hp, a 20% jump - the cube law that makes trap speed, not ET, the cleaner power indicator. Empirical fit to typical cars, wheel power, not a substitute for a dyno. A hobbyist estimate; the actual dyno measurement governs.
• 2K Paint Mix Ratio - The hardener and reducer to add and the total batch from a ratio like 4:1 or 4:1:1 and a measured base-paint volume, in fluid ounces and milliliters. Ratios are by volume.
• Hydraulic Pump Drive Horsepower - Fluid HP = gpm x psi / 1714, drive HP = fluid HP / efficiency. 10 GPM at 2000 psi, 0.85 efficiency -> 11.7 fluid HP, 13.7 drive HP (size the motor to 13.7 and round up); at 100% efficiency the 2.0 HP gap is the pump loss. A sizing aid; the pump and motor data govern.
• Hydraulic Motor Torque and Speed - Torque = psi x disp / (2 pi) x mech eff, speed = 231 x gpm / disp x vol eff, HP = T x rpm / 63025. 2000 psi, 2.0 in^3/rev, 10 GPM -> 573 in-lb, 1097 rpm, 9.98 HP; doubling displacement halves speed and doubles torque (same power). A sizing aid; the motor data govern.
• Cooling-System Coolant Flow for a Heat Load - gpm = Q / (c x deltaT), c = 500 water / 427 glycol. 150,000 Btu/hr at a 10 F rise needs 30 GPM (water) or 35 GPM (50/50 glycol, ~17% more); a tighter 5 F rise doubles the flow to 60 GPM. A sizing aid; the equipment ratings and fluid properties govern.
• Marine Propeller Pitch Selection - The pitch to swap to so the engine reaches the top of its rated RPM band at wide-open throttle: each inch of pitch changes WOT RPM by ~200 rpm, so pitch change = (target - current WOT RPM) / rpm-per-inch and new pitch = current - change. A 19 in prop hitting 5000 rpm against a 5400 target drops to a 17 in prop; a boat over-revving to 6000 goes up to 22 in. Under-rev needs less pitch, over-rev needs more. A selection aid; a WOT test with the new prop and the dealer's prop chart govern.
• Engine Fuel Burn from Horsepower (BSFC) - The fuel burn in gallons per hour from engine power and brake-specific fuel consumption: lb/hr = HP x BSFC, gph = lb/hr / fuel density (diesel ~7.1, gasoline ~6.1 lb/gal), and run time = tank / gph. A 300 hp diesel at BSFC 0.37 burns 15.6 GPH (12.8 hours on a 200 gal tank); the same power from a gasoline engine (BSFC 0.50) burns 24.6 GPH, 58% more. The burn at the entered power; real duty-cycle burn is lower. A planning aid; the engine's fuel map and a measured burn govern.
• Alternator Charging Load Balance - Whether the alternator keeps up with the electrical load at idle and cruise: it makes only ~50% of its rated output at idle and ~90% at cruise, so balance = output - total continuous load. A 65 A load on a 120 A alternator runs a 5 A deficit at idle (battery drains at stoplights) but a healthy +43 A at cruise; a 160 A alternator turns the idle balance to +15 A. A screening aid; the alternator's actual output curve and the real duty cycle govern.
• Torque Wrench Extension / Crowfoot Correction - The wrench setting a crowfoot or in-line extension demands, which bolt-torque never gives: TW = TA x L / (L + E cos(angle)), the target torque scaled by the wrench lever L over the lengthened lever. A 3 in in-line crowfoot on an 18 in wrench targeting 100 ft-lb means dialing 85.7 - set it to 100 instead and you apply 116.7 ft-lb, a 17% over-torque that snaps small fasteners. Swing the crowfoot to 90 degrees and cos goes to zero, so no correction is needed - the field workaround. A shop aid; the calibrated wrench and the manufacturer's torque spec govern.
• Density Altitude and Pressure Altitude - Why a 5,000 ft strip flies like 8,500 ft on a hot day: the FAA density-altitude method turns field elevation, altimeter setting, and temperature into the performance altitude a chart is entered with. PA = elevation + (29.92 - altimeter) x 1000; ISA = 15 - 2 x (PA/1000) C; DA = PA + 120 x (OAT - ISA). A 5,000 ft field at 29.92 and 95 F is 30 C warmer than standard -> DA 8,600 ft, so lift, engine power, and prop thrust all fall as if 3,600 ft higher; a cold -5 F day drops DA to about 1,930 ft, the winter bonus. Dry-air model (humidity lowers density further); the aircraft flight manual and the pilot in command govern.
• Crosswind and Headwind Component - The wind split pilots misjudge, and the gust that actually counts: angle = |wind dir - runway heading| folded to 0-180, crosswind = speed x sin(angle), headwind = speed x cos(angle). A wind '20 kt, 30 deg off' is only 10 kt of crosswind but 17 kt of headwind. Two traps made explicit: the value checked against the aircraft's maximum demonstrated crosswind is the GUST, not the steady wind, and a wind more than 90 deg off the nose becomes a TAILWIND -- it still adds crosswind while erasing the headwind margin, the setup that overruns a runway. Returns both components with a tailwind flag and a demonstrated-crosswind check. A planning aid; the pilot in command and the flight manual govern.
• Displacement Hull Speed and Speed/Length Ratio - The displacement wall horsepower cannot push through: a displacement hull is trapped by the wave it makes, so hull_speed = 1.34 x sqrt(LWL) knots is a hard ceiling. A 25 ft waterline caps near 6.70 kn no matter the power, until a planing hull breaks free. Enter an actual speed for the speed-length ratio SL = speed / sqrt(LWL) and the regime: SL <= 1.34 displacement, 1.34-2.5 semi-displacement, > 2.5 planing (that same 25 ft hull at 18 kn is SL 3.6, planing, off the wall). A boater reading a prop-based speed without the displacement wall over-predicts a heavy cruiser and over-props the engine. A planning estimate; the hull form, displacement, and power govern.
• Anchor Rode Scope and Swing Radius - The bow-height-and-high-tide scope that keeps an anchor set: scope is rode paid out over the VERTICAL rise from the seabed to the bow roller -- depth PLUS bow-roller height, at HIGH tide, not the sounder depth. In 15 ft of water with a 3 ft bow roller the true vertical is 18 ft, so a 7:1 scope needs 126 ft of rode (a 154.7 ft swing radius for a 30 ft boat); anchoring on 15 ft alone pays out only 105 ft = an actual 5.8:1, the quiet error that drags at 2 a.m. All-chain holds at 3:1 (54 ft rode, an 80.9 ft swing) -- a tighter circle, why it is favored in a crowded anchorage. A planning aid; conditions, bottom type, and skipper judgment govern.
• Turbocharger Pressure Ratio and Charge-Air Temp - Why boost is a gauge number and why it needs an intercooler: PR = (ambient_abs + boost) / ambient_abs, so the ambient must be added before dividing -- 15 psi at sea level (14.7 psia) is PR 2.02, but the same 15 psi a mile high (12.2 psia) is PR 2.23, a hotter outlet for the identical boost. Compressing air heats it: T_out = T_in x [1 + (PR^0.283 - 1)/efficiency], so 15 psi at 80 F inlet and 70% efficiency reaches 250 F -- a 170 F rise from compression alone, why an intercooler is mandatory on a serious build. Reports the compressor-outlet (not manifold) temperature. A planning estimate; the compressor map and engine build govern.
• Crouch Planing-Speed Estimate - The planing top-speed estimate and its diminishing return, the opposite regime from the displacement hull-speed wall: Crouch's formula speed = C / sqrt(weight / hp), in MILES PER HOUR (not knots), with the hull constant C about 150 heavy cruiser, 190 runabout, 210 race. A 6,000 lb runabout with 200 hp and C = 190 makes 34.7 mph; double the power to 400 hp and it reaches only 49.1 mph -- twice the horsepower buys sqrt(2) = 41% more speed, not double, because speed scales with the square root of the power-to-weight ratio. Assumes the boat is on plane (below the planing threshold use the hull-speed tile). A planning estimate; the hull, propeller, and conditions govern.
• Wheel Offset and Backspacing - Converting wheel offset to backspacing, and where the inch hides: offset (ET, mm, mounting face to centerline) and backspacing (in, mounting face to inboard rim edge) describe the same fitment in different units. backspacing = rim_width/2 + 0.5 + offset/25.4, and the rim 'width' is the bead seat -- the wheel is ~1 in wider overall (half an inch per flange), the omission that makes a fitment come out an inch wrong. An 8 in wheel at +45 mm has 6.27 in backspacing and 2.73 in frontspacing; a zero-offset wheel sits nearly 1.8 in further out. A more positive offset pulls the wheel inboard (more fender, less brake/strut clearance). A fitment aid; the wheel, hub, and suspension clearances govern.
• Brake Pedal Ratio and Line Pressure - Why doubling the master-cylinder bore quarters the pressure: Pascal's law end to end. mc_force = pedal x ratio x booster; line pressure = mc_force / (pi/4 x bore^2); clamp = line pressure x caliper area; brake torque = clamp x 2 x friction x rotor radius. A 50 lb pedal at 5:1 manual through a 7/8 in master makes 416 psi -> 1,663 lb clamp -> 5,987 in-lb per corner; swap to a 1.75 in master (double the bore) and the pressure drops to 104 psi, exactly a quarter, for the same leg -- the whole manual-vs-boosted trade. The 2 in the torque is both pad faces. A design aid; the pad friction, thermal state, and system compliance govern.
• SAE J1349 Dyno Correction Factor - The dry-pressure correction that makes two dyno pulls comparable: SAE J1349 corrects observed power to a standard day (25 C, 99 kPa DRY). The catch is 'dry' -- subtract the water-vapor pressure from the barometric before applying, because humid air makes less power. P_dry = baro - vapor; CF = 1.18 x (990/P_dry) x sqrt((T+273)/298) - 0.18; corrected = observed x CF. 400 hp at 980 mbar dry, 30 C -> CF 1.0220 -> 408.8 hp; a hotter, thinner 970 mbar / 35 C day corrects harder, CF 1.0444. Valid only ~15-35 C, 900-1050 mbar (flagged outside); the older STD (J607) basis runs ~4% higher and cannot be compared to SAE. A comparison aid; the dyno and correction basis govern.
• Aircraft Weight and Balance (CG Envelope) - The in-gross-weight-but-out-of-CG load weight-and-balance exists to catch: sum the station moments (empty, occupants, fuel, baggage), CG = total moment / total weight, legal only if weight <= max gross AND fwd_limit <= CG <= aft_limit. A 1,500 lb (39 in) aircraft with 340 lb front, 180 lb fuel, 200 lb baggage is 2,220 lb, CG 44.47 in -- legal. Fly lighter but pack 300 lb of baggage aft and it is 2,100 lb (under gross) yet CG 47.24 in -- BEHIND the 47 in aft limit and dangerously unstable. Fuel burn moves the CG, so both takeoff and landing CG must be in the envelope. A loading aid; the aircraft flight manual and the pilot in command govern.
• ABYC E-11 Marine DC Wire Sizing - Why a dockside NEC wire size undersizes on a boat: ABYC E-11 sizes on the ROUND-TRIP length (out and back), CM = 10.75 x current x (2 x length) / V_drop, not the NEC one-way habit -- and the marine allowable drop is stricter where it matters, 3% for panelboard feeders and nav/critical loads (10% non-critical). A 20 A nav feeder, 25 ft one-way, 12 V, 3% has only 0.36 V of headroom -> 29,861 circular mils -> #4 wire (#6 falls short); relax to 10% non-critical and it drops to 8,958 CM -> #10, three sizes smaller. The ABYC ampacity table sets a separate floor the drop size must clear. A design aid; the standard, wire temperature rating, and installation govern.
• Cutting-Fluid Concentration - The running concentration of a coolant sump from a refractometer Brix reading and the fluid's factor, and the concentrate to add (or water to add) to bring it to a target.
• Cutting Power and Spindle Torque - Cutting horsepower, motor horsepower after drive efficiency, and spindle torque from the material removal rate and the specific cutting energy (unit power: about 1.0 carbon steel, 0.33 aluminum, 1.5 stainless/titanium) -- the stall / motor-size check before a heavy cut. The tool and machine govern the real draw.