Exemplar for internal assessment resource Technology for Achievement Standard 91620
After that was complete, the front edges of the brass cylinder had to be routed off with a
5mm diameter radios curve. In the diagram it said that we had to use a file to do the curve
however Mr.X found out that we can use a router bit to curve out the edges. What I had to do
was place the bass cylinder in the jaws of the milling machine with parallel, after that put the
5mm router bit into the key less chuck and change the speed of the machine to about
620RPM. when the milling machine was all set adjust the z axis to the right depth and also
adjust the x axis to the right mount I needed to come in. both the x and y axis have to be
correct unless I won't get a good round curve. After all of that is set I sprayed some CRC on
the edges so that the cut will be clean and smooth and moved they axis along the router bit
which gave the 5mm radius curve. I did the same with the top edge and the edge of the other
side of the brass cylinder.
The pop test
The PTFE had to make an airtight seal in the brass piston block unless the engine won't run
properly. To do this I had to get the diameter of the PTFE to 10mm that is because the hole
on the brass piston block was ream at 10mm. When I was doing the PTFE I had to
constantly check the measurements of the PTFE using the Vernier’s so that the piston head
will finish at an exact size. To do the pop test I had to attach the piston head into the conrod
with had a M6 thread on it and I had the same thread on the piston head as well. The reason
I had to do threads on both of this components is because if it didn't not a some sort of a
holding method the piston head will come of once it inside the piston block so to prevent that
from happening these two had to be threaded. After that I did the actual pop test using the
piston head which was on the conrod and the brass piston block what I did was I put my
thumb over the exhaust hole on the piston block and then pushed the piston head down so
that the piston block have compressed the air which was inside the chamber and then I
slowly pulled out the piston head and as it came out it made a popping sound which was
meaning that my PTFE/piston head was correct made and it do have an airtight seal. The
reason behind this test was to see that the piston head and the brass piston was made to
size so that it had an airtight seal.
© NZQA 2015
Exemplar for internal assessment resource Technology for Achievement Standard 91620
Honed crankshaft bore which the flywheel and crank plate when through.
The hole which the crack shaft when through the aluminium center block had to be
perpendicular unless it will create friction on either sides of the hole on the aluminium block.
After cutting out the crankshaft over size from a 6mm diameter piece of steel, I grinded off
the edge of the crankshaft so that I have a leading edge which will make it easier to send it
through the crank plate, the hole on the aluminium block and the flywheel. After that I fitted
the flywheel on one side of the crack shaft and then I slide through the hole on the aluminium
block and after that I slide the crank plate on the other side of the crank shaft. Then I turned
the crack shaft using the flywheel couple of times to see if it do create any friction when it
rotating around. Lucky mine didn't have any friction so therefore I think the honed hole on the
aluminium block was done correctly. I was pretty sure that it was strait because when I was
drilling it on the milling machine I used the parallels so that the aluminium body was flat and
levelled. I also had to make sure that the crankshaft was cut out from a strait piece of steel.
The finish size of the shaft have to be 56.47mm long .The reason for doing this test was to
see if the honed crankshaft bore was crating any friction when the crack shaft is going
around inside the hole.
The student undertakes preparation, integration and testing to comply with relevant health
and safety regulations and codes of practice. The student follows classroom rules ensuring
both their own safety and that of others. They use the PPE provided (for example, safety
glasses on DRO lathe) and carry out procedures in a safe manner. For example, they only
operate machines after being trained in their use and operate these within their correct limits
and codes of practice.
© NZQA 2015