The fitted Bosch AL298X.

Correct the alternator’s position.

The previous whole-car alternator sat too low and too far rearward against the existing engine-bay photographs. Reviewed casing surfaces and seam tracks in the shared 14-view reconstruction now guide a rigid unit translation of −38 / +141 / +80 mm along the provisional engine X/Y/Z axes. These are conditional photo estimates, not measurements of the installed car. The engine/body frame and every retained component dimension stay.

What the photos support

Reviewed rear silver-shell points guide a circular section with its axis held parallel to engine Z. Front and rear stator seam tracks guide the longitudinal shift. The selected shaft X/Y center is 140 / 52 mm in this conditional frame. The original casing, rotor, fan, pulley and pivot comparison shapes move together as 13 native groups; the original detailed engine export remains available in its historical source pose. The retained 25 mm stator band is longer than the reconstructed visible seam interval, so this is a pose correction rather than a fitted casing survey.

The connections remain open

The revised alternator pulley plane is 80 mm ahead of the retained crank/pump belt plane in the model. The old complete belt and engine-side lower bracket/adjusting link therefore remain separately selectable unresolved comparisons, hidden in the assembled whole-car view. No new belt, stretched bracket or invented support closes that discrepancy. The engine, pump, crank and body are not moved to force a join.

The sampled plate/case overlap falls from 5,793 to 487 mm³, but at that revision the old whole-car upper-hose reference intersected the case by about 13,418 mm³. That hose conflict, the remaining plate contact and the drive/support gaps are reconstruction errors, not actual-car interference or clearance findings. That upper-hose conflict is superseded by the new photo-guided outlet and visible hose, which no longer intersects the sampled alternator. The old drive/support boundaries remain unresolved; the newer hose exposed the independently placed radiator/pump references. The subsequent cooling-frame revision relocates the retained-size radiator and reveals the hose; pump/front-drive and hidden circuit registration remain unresolved.

Workshop limit: this pose helps locate the unit and surrounding obstacles. It does not establish loaded support, fitted fasteners, electrical compatibility, tool access, a verified release order or a removal path. Display separation remains illustrative.

Look at the installed assembly

Specifications versus measurements

The Bosch AL298X product photographs show the front casting without a pulley from several angles. They establish that three-opening front-face layout and upper ear as catalog topology, but provide no scale; the installed remanufactured case must be compared with those views before treating even the shape as a match.

The J&N 400-30029 listing cross-references AL298X but describes a different replacement unit. It warns that its 17 mm shaft will not accept an OEM pulley with a 15 mm bore. Those are dimensions of the J&N comparison, not measurements of this Bosch alternator; the warning is a reason to verify any proposed pulley transfer.

NAPA’s AL298X listing also needs care: it says the pulley is not included while simultaneously supplying a 71 mm pulley diameter, a six-groove serpentine type and a 22SI series. Those pulley fields do not describe the single V-groove pulley visible on this car or Bosch’s 1V catalog description. Do not use that listing to size this car’s pulley, belt or shaft; measure the installed assembly and check the proposed replacement’s actual specification.

Replacement stator dimensions: a closer AL298X comparison

IAT's replacement-stator catalog (PDF page 4) lists part 07118 for Bosch AL298X: 108.25 mm outside diameter, 73.95 mm inside diameter, a 20.55 mm lamination stack and 36 slots. The public CAD now uses the listed diameters instead of a generic 17/18ACR comparison. Its 25 mm visible dark-band length is still estimated from owner photos; the catalog's lamination stack and 35.60 mm exposed-stack figure do not identify the gap between the two silver castings. The remanufactured stator installed on this car has not been inspected or measured.

Do not mix internal parts by complete-alternator cross-reference. IAT’s Lucas 17/18ACR replacement rotor 17402 (PDF page 10) has an 83 mm outside diameter. That is larger than the 73.95 mm bore of its Bosch-family stator 07118, so those two catalog parts cannot be an internal pair. Broad complete-unit interchanges involving AL298X or Lester 14029 do not resolve which core this remanufactured unit contains. Before ordering a regulator, rotor, stator or bearing, document the installed casing and internal part numbers or have the unit identified on the bench.

Inside the alternator: rotor study

The CAD now separates the rotating shaft and opposed claw poles from the case, with selectable field-winding and slip-ring envelopes. Bosch’s alternator cutaway supports that arrangement. The 1977 Midget parts list names rotor 37H4196 for the original 16ACR assembly. Neither identifies the rotor inside this car’s remanufactured AL298X. A J&N interchange note says an original Lucas-family pulley fits a 15 mm shaft, while its 17 mm replacement needs a different pulley. The virtual shaft and pulley bore now use that 15 mm comparison, which has not been measured on this Bosch reman unit. Pole shape, ring dimensions and the internal air gap are estimates; use the view to understand function, not to order internals or machine parts.

Select rotor in CAD ↗ · Select field winding ↗ · Select slip rings ↗

North American Midget 1500 mounting: catalog correction

The factory Midget 1500 parts list, printed page 183 lists bracket 147899 in the common mounting group and adds bracket CHA304 for USA and Canada. It separates the non-North-American pivot spacer 147483 and bolt HB839 from North American distance tube UKC3128 and bolt HB841. The dimensions and exact placement of CHA304, UKC3128 and HB841 are not established by this list.

The current virtual lower mount includes a 147899-style bracket, a 73 mm comparison tube and a 127 mm comparison bolt. It does not reconstruct the additional North American bracket or prove the hardware fitted to this Bosch AL298X installation. Photograph and measure the complete actual mount before using the model to plan removal or order parts.

Upper adjusting link: visible shape, unresolved fit

The Spitfire 1500 exploded alternator plate, PDF page 102 shows link 156464 at the alternator's upper ear, with separate fixing hardware. The factory Midget parts list calls its link-to-alternator screw HU858; a replacement listing describes HU858 as 5/16-inch UNC × 1 inch. The factory Spitfire 1500 alternator-mounting plate lists SH108251 with NT108041 as a metric screw-and-nut pair, and HU858 with JN2158 as the imperial alternative. It explicitly says the alternatives are not interchangeable. That shared 156464 link is a useful cross-check, but it does not identify the threads on this Bosch-fitted Midget. Measure the removed upper screw diameter and pitch and verify its mating thread before ordering or reinstalling hardware. The previous virtual slot missed the projected ear hole and was narrower than that nominal screw. Its new 44 × 9 mm opening admits the projected screw in plan view only; these are comparison dimensions, not measurements of this fitted link or Bosch installation. The Moss Europe Midget catalogue, printed p. 183 lists BH605181 as the bolt from link 156464 to the thermostat housing on 1500 FP engines, with a lock washer. Rimmer identifies BH605181 as a 5/16-inch UNF × 2¼-inch hex bolt with a ½ AF head. This is a specific place and fastener to check on this car; the fitted attachment has not been confirmed. In the public CAD, the engine-side tab does not meet the modeled housing, the slotted arm is 20 mm ahead of the upper-ear face, and the estimated bend intersects the timing cover. The link remains a recognition shape, not a tool-access guide. Two direct axial measurements can reposition its tab and arm planes, and directly measured slot travel and clear width can reshape the arm in a separate owner STEP; the builder rejects an intersection with the provisional front plate or timing cover. This does not establish the real tab anchor, bend path or fitted fasteners. Record the anchor and upper-link measurements in the CAD worksheet ↗

Record the pivot withdrawal datums

Before a planned removal, identify the fitted bolt-head side and photograph its axis and the first fixed obstruction on that side. Record the straight span from the underside bearing face or the outermost head surface to that obstruction. In the CAD worksheet, explicitly select which starting face was observed; preserve the source, configuration and photo of the endpoints. Record actual under-head bolt length only from appropriate access or a positively identified identical bolt. Measure the real axial head projection separately. In Measurements and model details, select the observed under-head bearing face to furthest head surface datum, then record the projection along the bolt axis. Exclude washers and the socket; preserve the original configuration, bolt markings and photo reference. A supported direct reading changes only that outside projection in an owner build. The public 5 mm head, hex width, shank diameter and mounting plane remain model comparisons until measured.

The CAD panel uses a loaded build’s evidence independently of saved browser notes. Its source mesh determines modeled direction and length. A same-side recorded span with confirmed endpoints bounds viewing movement. An underside-to-obstruction span includes the head, so the modeled head projection is subtracted. A span starting at the outside head surface is already free space, so head thickness is not subtracted again. Older spans without endpoint confirmation remain notes and leave separation illustrative. A side, length or head-projection mismatch holds movement until the source is reviewed or rebuilt. Raw span minus bolt length does not establish head/tool room or an exit path. Legacy rear-only notes cannot substitute for the head-side observation.

Keep lower-mount dimensions independent

Record the clear ear gap, spacer, bracket lug and each internal washer/shim pack from one identified configuration. The owner builder preserves supported readings even when the stack leaves a gap or overlaps; an unmeasured tube stays the 73 mm comparison. It also preserves a supported bolt length and tube diameters when they conflict with provisional hardware or a guessed wall margin. Recheck the observations and model stations before selecting hardware.

The pivot inspector reports source-model axial arithmetic and bolt reach separately from the six-direct-reading comparison. Neither a zero residual nor a bolt projecting beyond the model nut proves fitted clamping, thread engagement, tube strength or a removal path. Older exports without this independent-stack record remain unchecked.

About the Spitfire wiring diagram

The Amicale Spitfire bulletin 62 diagram labels the alternator, warning lamp, battery and other charging/ignition components on a Spitfire 1500. It is a 2001 reproduction with no model-year or market designation; its key includes Italy-only, left-hand-drive-only and overdrive items. It is not the wiring diagram for this Midget. The fitted Bosch AL298X is a remanufactured unit. Photograph its actual plug, terminals and wire colors, then compare with a verified 1975 North American Midget diagram before disconnecting or reconnecting it. See the source applicability notes ↗ The Midget factory manual contents identify the correct 1975 U.S.A. diagram as topic 86.00.03; its circuit page has not yet been inspected. Record this car’s connector in the wiring worksheet ↗

Capture the missing measurements

1. With the engine off and unable to start, photograph the front face square-on, the rear electrical side, both lower ears and the upper adjusting link. Include a ruler in the same plane as each target.
2. Record the outside diameter and axial length of each visible silver casting, dark stator band and dark rear cover separately. Mark the planes used for each measurement.
3. Measure the clear gap between the inner faces of the two ears, both ear thicknesses and the pivot hole diameters. Photograph the bolt head, nut, spacer and every washer or shim before disassembly. Photograph the slotted upper link from the side as well: record which axial face meets the alternator upper ear, the spacer/washer stack at that joint, and where the engine-side tab sits relative to the timing-cover front face. During a planned removal, measure the spacer end-to-end, its outside and bore diameters, and the fixed bracket lug across its flat faces. Record the total thickness of any internal packs at R (rear ear/spacer), M (spacer/lug) and F (lug/front ear), plus each piece’s order.
4. Measure the pulley outside diameter, groove width and pulley-groove plane relative to the front mounting ear. Compare crank, pump and alternator groove alignment on the car.
5. Record whether the fitted pivot-bolt head faces front or rear, the straight space on that head side, and any obstruction. Measure the actual under-head bolt length when safely accessible. The CAD worksheet compares these values. A separate owner build can apply a direct bolt length and observed head side; its 3D slider then illustrates that direction without proving clearance.
6. Photograph the actual rear housing straight on, including connector latch, any separate stud, every terminal and wire, and adjacent clearance. Compare it with the catalog-based 3D rear housing; do not rely on its orientation or cavity for wiring. Enter the observations and photo filenames in the planner evidence log.

The CAD inspector records four case outside diameters and four axial section lengths, shaft-to-pivot distance, front and rear ear thicknesses, clear ear gap, bracket lug thickness, spacer length and diameters, and the pivot bolt’s length and observed head side. Direct values can reshape a separate owner STEP; the public 3D view remains a comparison model. For the lower stack, the builder can also place directly measured internal washer or shim packs at the rear ear, between spacer and lug, and at the front ear. Independent lengths are preserved even when the stack leaves an axial gap or overlaps; no fitted tolerance or closing spacer length is inferred. The CAD inspector reports the signed arithmetic residual G − (S+L+R+M+F) after all six values have supported direct observations and source notes, using the loaded build’s own evidence when one is open; enter 0 mm for a pack only after checking that position. Each positive pack is one selectable thickness envelope: record its individual pieces, order and unknown radial sizes in the source note rather than treating the ring as an identified washer. The front-ear station, bracket foot and mounting centers, upper-link fit, connector terminals, pulley alignment and actual removal clearance remain unmeasured.

A positive residual means unaccounted axial span; a negative residual means the listed pieces exceed the gap. No fitted tolerance or measurement uncertainty is inferred, even when the displayed residual rounds to zero. Record the same assembly/configuration, whether the ear-gap reading was clamped or unloaded, and each actual measuring face. Missing values are not filled from model defaults, inferred spacer lengths or another build's browser notes. A residual alone cannot select washers/shims or establish clamping, radial fit or removal clearance.

Filter position corrected against the bay photos

IMG_6971–6972 and IMG_7041 place the blue PF53 beneath and behind the alternator, ahead and below the distributor. The former engine reconstruction put the filter high on the rear half of the block. Its head, seal, adapter, gasket and canister now move together to the lower/front block-side region shown in the 1500 external-engine illustration, printed page 14.

The new position is an estimate traced from that illustration and checked qualitatively against the owner photos. It is not a factory dimension or owner measurement. The photographed PF53 identity and catalog-size envelope remain distinct from the estimated head and placement. This correction improves the alternator's surrounding layout; it does not establish a hand/tool gap, bolt withdrawal direction or alternator exit path. The upper adjusting-link connection remains unresolved.

Inspect the corrected filter beside the alternator ↗ · Inspect its block-side head ↗

Closed pivot eye and an intact bracket foot

The 147899 reference photograph shows a closed pivot eye, a gusseted support and two fixing holes in the foot. The CAD formerly cut its pivot bore through the lug edge and removed a rectangle from the foot solely to let the comparison bolt pass. Both unsupported features are corrected: the eye is enclosed and the foot material remains.

The restored foot intersects the default long comparison bolt by about 99 mm³ at the estimated assembled stations. That is an unresolved model conflict, not a measured obstruction on your car. A slider animation can pass through material; it does not establish a removal path. The separate native bolt-sweep check now reports the conflict rather than relying on an invented opening.

The catalog photo supports topology, not the modeled 12 mm crown radius, dimensions, mounting coordinates or fitted bracket identity. The additional North American CHA304 bracket remains unresolved. IMG_6853/6894 show the upper arm/fixing, but do not expose a complete engine-side stack; the upper link has not been repositioned to close its unsupported gap.

Inspect the corrected lower bracket ↗