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Patents #2 Valve Actuation, Suck and Blow

February 14, 2010

Valve Actuation, Suck and Blow

Spacke V twin, From Victor Page

Fred Spacke patented a V twin motor in 1914, late in the veteran era.  Spacke’s invention took the typical motor of the era and spun a few parts around sideways.  To understand this phrase, we must first explore a bit more of the history of valve actuation as used on motorbicycles.  By the early 19teens, the automatic inlet valve  (see ) had been eliminated, replaced by cam actuation for the inlet.

A typical single cylinder motor is shown in Figure 2, my Rudge 500cc from 1914.   The inlet valve and its spring , pushrod and rocker are easily seen.  This type of motor was referred to as IOE, for Inlet Over Exhaust.  Another common layout was the Sidevalve layout, with both valves placed side by side.  The Triumph sidevalve motor is shown with two valve springs seen amongst the cylinder cooling fins.

1914 Rudge Multi IOE

Rudge 500cc IOE, from Victor Page

Triumph side valve

The reader may ask, “why all the various methods of valve actuation”.  Good question.  During the Pioneer and Veteran eras, motors were devised from no small variety of inventors, in many parts of the world.  Each idea had its merits, but some had more than others.  The Automatic inlet valve was a low cost solution, but limited the possible amount of air/fuel that could be ingested into the combustion chamber, which directly limited the power and go-fast noises that came from the motor.  Any method of cam actuation was an improvement.  Sidevalves were pretty simple, and allowed the use of common components to save money.  That is, the inlet and exhaust both had the same size of valve, spring, keeper, cam follower, etc.  IOE motors did not have the same economy of scale that comes by utilizing common components, but it did have one great advantage:  valve cooling.  The inlet valve was placed directly in the path of the cool incoming gasses from the carburetor.  Early motors often suffered from broken valves as the valve head fell off the valve stem.  The engineering understanding of steel and metallurgy had not yet progressed enough to ensure that valves were made from material with sufficient strength at high temperatures.  (another example of how  the modern vintagent is spoiled by technology!)   At best, a broken valve required one to open up the motor to pull out the valve bits and replace them.  But at worst, the valve head could bounce into the combustion chamber and destroy the piston and head, or even wedge into place and damage the connecting rod, which may break and blow out the side of the engine crankcase!  So, until the metallurgists found good steels, the engine inventors did their best to keep the valves cool, with the IOE layout being one example.

Spacke patent

Now back to Spacke:  He used the IOE layout for his V twin motor and his patent drawing is shown in Figure 4.  The rear inlet valve can be seen #66, actuated through a rocker which is pushed up from the pushrod #64.  So far, just like the other motors of the era.  But take a close look at that mess below the pushrods!  The pushrod is lifted by a cam follower #60, which is lifted by the face lobe on the camshaft #43.  The interesting part is that the cam shaft is mounted in line with the bike chassis, running front-to-back with the motor.  Four face lobes are on the shaft.  The inlet for the front cylinder is at max lift, shown as a curve intersecting follower #59, while #58 is down on the lobe, keep the exhaust valve closed.  It sounds simple enough once you understand a face cam, but how fun it must have been to fabricate and time all the various face lobes.  More fun details include the skew gears needed to turn the crank motion 90degrees to spin the camshaft #42 and #37.  Don’t forget, then the motion has to turn 90 more degrees to spin the magneto at #51 and #52.  Now the good reader will again ask that pertinent question “Why?”   Hmmm…  Spacke is long gone now, and we cannot get an answer from him.  Possible theories may include that the immigrants to the US Midwest were independent thinkers, or maybe something along the lines of him having lots of free time and a good machine shop…  I’m not sure how quickly those cam followers wore out with the small contact areas and off axis motion rubbing on them with every rpm.   But my friend Matt is rebuilding a motor during 2010 for the Cannonball.  You can follow his progress as he builds and rebuilds his motor and bike on his blog here:

One Comment leave one →
  1. January 17, 2016 10:24 pm

    I know that exposing the valves would help cool them. I wonder why it wasn’t the exhaust valve that was on top. That valve has to handle the flow of hot exhaust gases. It would seem that even if the intake valve would be in the block, it would be cooled by the incoming intake charge. The IOE valve arrangement became an established design before WWII so I guess it was a successful design. There may have been a ram effect from the downward intake charge. I recently saw an article in the British magazine, Classic Car, that featured the post WWII Rolls Royce inline 6. This motor adopted the IOE lay out and was used until the early 1960s when their new V8 was developed. The interesting point was that prior to the war an OHV design had been used. The article stated that the IOE was used because it would run better on the low octane fuel that was available in Britain after the war. Thanks for this great site! I just found it.

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