56 Terrier Motorcycle

FRS 106, Michael Littman – Spring 2014

Bottom End

Bottom End of the Triumph ’56 Terrier

Overview of the Oil Delivery System

Left to Right (including Photo bombers marked with Asterisk): Jordan Radke, Sharon You, Daniel Yang*, Manbir Gulati*, Kirk Robinson, Random Engineer*, Mackenzie Blanz, Ben Gaylord

A few weeks ago, our group conducted a test to ensure that the oil pump assembly was working properly. The test consisted of stripping the engine case of parts except for the oil pump and oil line, and inserting a mock distributor, which was attached to a power drill. The drill spun the distributor, which in turn powered the oil pump. Oil was then inserted through the input oil line. A positive test occurred if the oil was sucked through the pump efficiently. The first few tests were unsuccessful. This was because the interior of the oil pump was dirty, clogging one of the ball bearings. We disassembled the entire oil assembly, cleaned it, and then rebuilt it. After this the test was successful.

  • Larger cylinder displaces 4.6 mm, and its diameter is 7.9 mm
  • volume displaced per oscillation: (PI*(7.9/2)2)*4.6 =  240.1812 mm3
  • Smaller cylinder displaces 5 mm, and its diameter is 6.3 mm
  • volume displaced per oscillation: (PI*(6.3/2)2)*5.0 = 155.862
  • 6000RPM

The pump has two pistons, one large and one small. The smaller is the feed plunger, and oil goes from the oil tank to the feed plunger, initally pressurized by gravity alone. The feed plunger’s smaller area means that it pumps a smaller volume of oil. However, it pumps at a higher pressure than the larger piston. This is because pressure = force/ area, so reducing the area increases the pressure. The scavenge plunger pumps oil from below the scavenge filter, which is below the crank, and then goes through the pump and back up to the oil tank. The scavenge plunger is larger because it’s primary purpose is to pump out all the oil that it can. Having a larger diameter cylinder results in a greater volume of oil pumped, but at the cost of lower pressure. However, the force only needs to be high enough to pump the oil to the oil tank.

Gaskets & Creo

CAD in Motorcycle Restoring

by MGM

Gaskets, in the case of our motorcycle, are seals that are placed between the metallic surfaces of the engine so as to prevent oil from leaking. They are generally disposable, so we make our own so that they might last longer and be of a desired quality.

By working on Creo Parametric 2.0, CAD software, gaskets were created to exactly fit the dimensions of our motorcycle’s crankcase. First, the holes for the bolts on the crankcase were each assigned an (x, y) position on a coordinate system, so that they could be arranged in the coordinate plane in Creo. Then, their diameter and the width of the metal were all taken and used to give dimension to the gasket. Finally, after many adjustments to accomodate the exact shape of the crankcase, the gaskets are ready to print. Two were made.


Ben and Kirk

Roles of the transmission:

  • – Allow you to stay in the power band at a wide range of speeds
  • – Provide a gear reduction, so wheel speed is slower than engine speed
Main and Lay Shafts

The spinning motion from the engine comes into the main shaft (on the top in this picture) via the clutch, which it is connected to.  The gears on the main shaft then spins the layshaft, which in turn spins the right most gear on the main shaft, which actually spins independently of the main shaft.  This gear is connected to a sprocket which spins the rear wheel via a chain.

This diagram shows how rotational motion of the crankshaft, which is spun by the piston, is transferred to the spinning motion of the wheel.  At each stage of the transferal of rotational energy, the a gear reduction is used to change the rapid speed of the crank to the much slower speed of the wheel.  The number of teeth can be used to determine the ratio of number of rotations of one gear per number of rotations of the other per unit of time.

Gears: This graph represents the gear ratios in the format of engine RPM vs miles per hour of the motorcycle.