AJS POR­CU­PINE

A fast and flawed 1950s Grand Prix racer

Cycle World - - Contents - By KEVIN CAMERON

Here in all its dark, fluid grace is the AJS Por­cu­pine, a par­al­lel-twin that was Eng­land’s post­war bid to rise above the lim­ited power of tra­di­tional Bri­tish rac­ing sin­gles with more cylin­ders and higher revs. In 1949— the first year of the new FIM world cham­pi­onships— rider Les Gra­ham would give the Por­cu­pine its only cham­pi­onship. The bike in these pho­tos was not the cham­pi­onship-win­ning 1949 E90, but rather the last re­design in 1954 with 45-de­gree-in­clined cylin­ders.

The name—por­cu­pine—orig­i­nated with the quill-like spike finning be­tween the pair of cam cov­ers of the orig­i­nal en­gine, whose cylin­ders were just 15 de­grees above hor­i­zon­tal.

In the 1920s AJS had led the high-tech de­vel­op­ment of over­head-valve and then over­head-cam rac­ing sin­gles in the Isle of Man TT races. The Col­lier broth­ers, who joined AJS, Match­less, and Sun­beam into As­so­ci­ated Mo­tor Cy­cles (AMC), had them­selves been pre-world War I TT winners.

The Por­cu­pine’s usual ori­gin story is that it was sketched on nap­kins dur­ing tea breaks as World War II raged on. In fact, its cre­ation was more de­lib­er­ate. In 1939, AMC’S Don­ald Heather had teamed for­mer Nor­ton race boss Joe Craig with drafts­men/de­tail de­sign­ers Vic Webb and for­mer Vincent en­gi­neer Phil Irv­ing in an off-lim­its draw­ing of­fice. The main task of that of­fice, Irv­ing says in his au­to­bi­og­ra­phy, was “mainly the de­sign of a racer-type named E90S, the ‘S’ stand­ing for ‘Supercharged.’”

The goal of the E90S was to over­come the mul­ti­cylin­der head start of BMW (which won the 1939 500cc TT with a supercharged flat-twin) and Gil­era (which had won the 1939 Euro­pean cham­pi­onship with a supercharged four).

Why a twin? AJS had shown an air-cooled V-4 street bike at the 1935 Olympia Show, then in­vested much ef­fort in try­ing to race it in var­i­ous forms. What did the V-4 teach them? That adding com­plex­ity in­creases a bike’s weight faster than it im­proves its per­for­mance. Rider Wal­ter Rusk on the supercharged and liq­uid-cooled AJS V-4 was as fast as the Gil­era at the 1939 Ul­ster Grand Prix, but the bike re­mained a mon­ster to handle. Harry Col­lier’s re­sponse was to be­gin de­sign­ing a supercharged in-line triple. The en­gine was mounted “head­first” to deal with the ex­tra heat of su­per­charg­ing—its cylin­ders hor­i­zon­tal so air would di­rectly hit the cool­ing fins be­tween its cam boxes.

Other teams ad­vanced more rapidly. Nor­ton’s new Rex Mccand­less-de­signed “Featherbed” twin-loop chas­sis made the Manx faster. Ge­off Duke would eas­ily have been cham­pion on a 500 Manx in 1950 had his tires not de­lam­i­nated (cot­ton plies at 150 mph!). Gil­era and new­comer MV Agusta saw that han­dling makes power us­able. Both “Nor­tonized” their air-cooled in-line four frames as fast as they could—aban­don­ing spindly pre­war chas­sis, jerky fric­tion dampers, and an­ti­quated girder forks.

In the 1950 TT, the Por­cu­pine’s best finish was Gra­ham’s fourth—be­hind three Featherbed-framed fac­tory Nor­ton sin­gles.

In the 1947 Isle of Man TT, Les Gra­ham was pushed down to sixth by a crash, then had his chain run off.

Af­ter a year’s ad­di­tional de­vel­op­ment, none of the Por­cu­pines fin­ished in the 1948 TT. Un­like Nor­ton or Ve­lo­cette, AJS had no con­tin­u­ing in-house rac­ing know-how. AMC boss Don­ald Heather there­fore asked Matt Wright (lately re­turned from Vincent) to take over de­vel­op­ment. He fur­ther adapted the Por­cu­pine to un­su­per­charged op­er­a­tion, first re­duc­ing valve an­gle to 79 de­grees, and then adding a de­flec­tor in each port to en­cour­age tur­bu­lence and im­prove com­bus­tion.

Wright’s pro­gram achieved 50 hp, but com­pany poli­cies worked against them. Rid­ers were re­quired to use AMC’S own un­ad­mired rear sus­pen­sion units. The use of stream­lin­ing was for­bid­den, and when en­gine air­flow pi­o­neer Harry Wes­lake of­fered his ser­vices, Don­ald Heather re­mark­ably turned him down.

Ev­ery­thing seemed to be go­ing their way in the 1949 TT, with Les Gra­ham and Ted Frend lead­ing 1-2. Then Frend crashed out, leav­ing Gra­ham lead­ing by miles, just 2 miles from the finish. Then the en­gine stopped. With Jock West (TT and grass-track racer who also worked for AMC in sales) trot­ting be­side him shout­ing en­cour­age­ment, Gra­ham pushed in the 2 miles for 10th place. The mag­neto drive had failed.

Gra­ham took sev­eral vic­to­ries (and a re­tire­ment with a split fuel tank) to take the world 500cc ti­tle by one point.

The Por­cu­pine’s 21-inch wheels were now down­sized to 19. En­gine oil was moved to a boat­like un­der­engine sump— to ease start­ing by al­low­ing pre­heated oil to be poured di­rectly into the en­gine. Wheel­base and weight were re­duced.

De­spite such ef­fort, AJS steadily lost ground to the Gil­eras. While Nor­ton’s Craig gained wis­dom from pun­ish­ing dyno-race sim­u­la­tions, po­lit­i­cal forces within AJS looked for some­one to blame for their lack of suc­cess.

For 1952, the ma­chine was com­pletely re­designed by Ike Hatch and Phil Walker, lift­ing the en­gine’s cylin­ders to 45 de­grees. Its cool­ing spikes were re­placed by nor­mal fins. A “softer” chain drive was sub­sti­tuted for the gears that had pre­vi­ously driven the mag­neto. Wright com­mented that “this whole project was a to­tal waste of ef­fort.”

For 1954, AJS hired the man then con­sid­ered to be Eng­land’s top rac­ing-de­vel­op­ment en­gi­neer: Jack Wil­liams. He re­placed the AMC rear sus­pen­sion units with the Gir­lings pre­ferred by ev­ery­one else. Rub­ber sleeves pre­vented the pre­vi­ous “shak­ing off” of the car­bu­re­tors. A new fuel tank, pump, and weir sys­tem (a kind of header tank and dam/ spill­way setup for con­sis­tent fuel de­liv­ery) re­placed trou­ble­some and vi­bra­tion-sen­si­tive float cham­bers.

In the 1954 TT, AJS team rider Derek Far­rant crashed on Lap 1. Rod Coleman ran fifth for three laps but pit­ted with a split fuel tank, com­ing home 12th. Bob Mcin­tyre fin­ished 14th.

As post­war auto pro­duc­tion took sales from mo­tor­cy­cles, GP rac­ing was re­vealed as an ex­trav­a­gance—not the pow­er­ful sales builder it had been in the 1920s. Tri­umph and BSA, who had hit the US bike mar­ket early, pros­pered. Those count­ing on do­mes­tic sales did not. At the end of 1954, all Bri­tish fac­tory GP teams ceased op­er­a­tion.

Had the Por­cu­pine suc­ceeded, it would today be re­mem­bered for its in­no­va­tions—uni­tized en­gine/trans­mis­sion con­struc­tion, gear pri­mary, and a modern chas­sis with hy­draulic-damped tele­scopic fork and swingarm.

There were two rea­sons for the Por­cu­pine’s lack of suc­cess. First, the hasty con­ver­sion from supercharged to un­su­per­charged op­er­a­tion was in­com­plete and failed to in­cor­po­rate best con­tem­po­rary prac­tice, and sec­ond, AJS man­age­ment had made the clas­sic mis­take of ini­ti­at­ing a project that needed more-in­ten­sive de­vel­op­ment than they were will­ing or able to pro­vide.

The Por­cu­pine re­mains a glo­ri­ous relic of an era marked by ex­per­i­men­ta­tion and pos­si­bil­ity and sur­vives to re­mind us of our suc­cesses and fail­ures.

TOP LEFT: Dry clutch, uni­tized en­gine/gear­box and gear pri­mary drive made the AJS ad­vanced for its day. TOP RIGHT: AJS on­slaught at the 1954 Isle of Man TT. OP­PO­SITE PAGE: This 1954 AJS E95 Por­cu­pine was bought by Robert Ian­nucci of Team Ob­so­lete with...

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