spagthorpe viking ds from viking iastate edu dan sorenson ds ryan cousineau compdyn questor org ryan cousineau writes ds riding up the hill leading to my ds house i encountered a liver and white springer spaniel no relation to ds the springer softail or the springer spagthorpe a close relation to ds the spagthorpe viking ds i must have missed the article on the spagthorpe viking was ds that the one with the little illuminated dragon s head on the front ds fender a style later copied by indian and the round side covers no not at all the viking was a trick little unit made way back when forties fifties when spag was trying to make a go of it in racing the first iteration the springer was a boxer twin very similar to max friz s famous design but with an overhead point cam see below for more on the valvetrain the problem was that the thing had no ground clearance whatsoever the solution was to curve the cylinder bores so that the ground clearance was substantially increased springer motor front viking motor front this is roughly the idea except that the bores were gradually curved around a radius as the pistons were loath to make a sharp angled turn in the middle of their stroke the engine also had curved connecting rods to accomodate the stroke the engine stuck out so far because of its revolutionary and still unique overhead cam system through the use of clever valve timing and and extrordinarily trick valve linkage only a single cam lobe was required to drive both overhead valves just as revolutionary was the hydraulic valve actuation which used a pressurized stream of oil to power the waterwheel which kept the lobe spinning over one side effect that required some rather brutal engineering fixes was that until the engine s oil pressure came up to normal the engine s valve timing would be more or less random resulting in some impressive start up valve damage the solution was a little hand crank that pressurized the cases before you started the beast remarkably similar to the system used in new porsches to pressurize the oil system before the car is started the cage however uses an electric oil pump wimps despite this fix the engine had a nasty propensity for explosively firing its valves into the pistons when a cylinder would temporarily lose a bit of oil pressure in a corner the solution was to run even higher oil pressures and change the gaskets and seals regularly this was feasible because it was a racing engine with just a single overhead lobe and no pushrod shaft chain towers because of the hydraulic system the head of the engine came to an almost perfect point lobe xx complex linkage not shown due to valvestems complexity piston note that the tip was not truly vertical it was at about a degree angle to the ground and this drawing doesn t show the curvature because there was none in the head itself the bore curve would start about where the cylinder bore disappears in this diagram the effect of the pointy heads on top of a pair of gently pundits of the day even said sensuously curved cylinders was much like a pair of finned viking horns poking out from beneath the gas tank thus the name the vik was a moderately successful racer lightning fast when it worked but plagued by problems relating to its revolutionary technology eventually it was dumped when spag finally realized that racing was not where the spagthorpe name would be made the machines were raced for another year or two by privateers and their fate approximately six vikings were made plus one or possibly two springers confusing the issue is one old spag staffer who swears up and down that this machine was tooled for production and that as many as twenty or thirty machines may have come off the line however no modern record of a production viking has survived and most motorcycle historians discount this story ryan cousinetc yamaha vision xz black pig of inverness live to ride kotrb ajs c s king rat to work to dod i d be a squid if i could afford the bike flame to ryan cousineau compdyn questor org vancouver bc canada live slmr a if you aren t sliding you aren t riding computer dynamics bbs hst v vancouver bc canada easy access low rates friendly sysop
