Marine transmissions

1. Explain the different type of gear selection systems

A)  in outboard gearcases and stern drivers.

B) Inboard marine gearboxes

2. What type of gears are used in outboards and stern legs?

A) Give an explanation of why manufacturers choose this type of gear

3. Explain what a duo propeller system is and how it works/operates

4. Why would a V drive be used instead of a standard shaft drive system

5. Compare a jet unit with a surface drive unit and give reasons why you would choose one system over the other

Engine reflection 2

I worked on an inboard motor before working on a gear case for an outboard motor, what I had to do was to make sure the engine drive sprocket was square with the drive shaft sprocket with out any restriction when you turn the driven shaft. I measured the diameter of the drive sprocket and use a DTI gauge to check the amount of runout it had which was 0.03mm. By using spacers, which were little plates of metal, i inserted them in where the engine mounts were to get the engine lined up with the propeller shaft properly.

I also used a feeler gauge/flare gauge and placing it between the drive and driven sprockets to check if there is any deflection between the two, if the flare gauge gets stuck in one place, but is fine as the rest of the shaft spins, that means that the engine isn’t inline and will have to be adjusted, either spun left or right slightly, tilted up or down. or moved to a side then twisted round slightly to match perfectly.

Engine Overview/Reflection

When us students came back from semester break, we were each partnered with a person and given each a motor to work on. So what happened was that each of us worked on a different part of the engine e.g: when i work on the engine, my buddy will work on the head block

After the engine block, I moved onto the engine head block and worked on that also. Same as the engine block i had to dismantle components from the block, but this time, I removed:

4 Valves (2 inlet and 2 exhaust)

4 Valve springs (2 inlet, 2 exhaust)

8 Valve collets (2 per valve which lock the valve keeper onto the valve)

6 Retainers (1 for each exhaust valve, and two for each inlet valve)

After the dismantling, I started to record some measurements, such as:

. The taper ovality of the valve guides. (any ware caused by the valve movement)

. The engine head warp. (warp is where the block would have changed shape slightly due to temperature changes)

. The valve stem warp. (measuring 3 different places down the valve stem to check for any bending)

. Working out the clearance between the valve stem and the valve guide. (this is done by taking the measurement of the valve thickness and the measurement from the valve guide, and misusing the valve stem measurement from the valve guide measurement)

. Checked the valve seat and angle.

. Checking the sureness of the valve spring. (this is done by lining the spring up with a square and using a vernier calliper to do the measurements)

. Checked the length of the valve spring.

. Checking the valve height when installed by removing the spring and using a vernier calliper to to place on the spring seat and bring the body up to the height of the keeper

. Checking the spring tension with and without the retainer.

. Calculate the lift of each camshaft lobe in millimetres

. Checking the taper ovality of the camshaft bearing journals.

. Checking the camshaft bearing run out by using a DTI gauge.

. Checking the clearance of the bearing oil clearance by using a plastigauge.

. Checking the cam pad thickness and clearance when installed.

Then after all this i put all the components back into the camshaft head and then me and my buddy pit the engine back together and timed it up accordingly.

TTEC 4852 Marine Business Practice

Business Requirements: (general business)

Consumer Guarantees Act:

Fair Trading Act:

 

Industry Rules, Regulations and Legislations: (Marine industry)

Health and safety Employment:

Council By-Laws:

Dangerous Goods:

Equipment Certification:

 

Trailer Service Regulations: (Marine trailers)

Land transport riles and regulations:

Traffic regulations:

 

Your assignment requires you to:

Access all above information from whatever source suits you.

The information DOES NOT have to be in your own words but MUST BE as it is written in the official document or information.

You may not download the information as you see fit, but it MUST ALL be in the same FONT etc.

You must put all the relevant information under the headings above, i.e: Business requirements etc.

You must provide all references as to where you accessed the information, I.e: websites etc

The assignment must have a cover page.

The assignment must have a contents page.

The assignment must be bound (not in a ring binder etc)

Gearbox work

  

(image from: http://hyperlogos.org/files/images/78_large.jpg )

1. What type of gears are used for reverse in a manual gearbox?

the type of gear used for reveres is a normal cross cut toothed gear, this allows the reverse idler gear to be positioned easily with the reverse gears on the output shaft and layshaft without the teeth grinding and stripping.Although the teeth are cross cut, there still is grinding when the three gears meet to mesh as the output shaft will still be spinning, when the reverse idler is pushed in to mesh with the output shaft, there is load as the layshaft is suddenly forced to spin the opposite direction.

2. What type of gears are used for all forward gears in a manual gear box?

With the forward driving gears, helical type are used, this means that the gears are diagonally cut, so that the gear has more surface area to mesh with othee gears other than a cross cut gear. This allows the gears to mesh easily without any whining noise like what the reverse gears make.

3. What is the purpose of a synchromesh unit?

A baulk-ring type of synchromesh unit is commonly used to synchronize the speeds of two gears before engagement. When the synchronizer is assembled, the hub is splined to the main shaft, and the engagement sleeve is splinted to the hub. The syncro ring, with recesses to accommodate the ends of the inserts, is located in each end of the hub, and a conical inner surface faces a matching steel cone on the gear.

(info from: http://moodle.student.cnwl.ac.uk/moodledata_shared/cdx%20etextbook/dswmedia/trans/clutchMan/gearLayOp/baulkring.html )

4. what type of bearings do we find in gearboxes

For the first gear, a caged roller bearing is used, as this gear is a high tension taking gear, the rest of the gears use grooves cut into the output shaft and run on a film of oil. This is because they don’t need to take as much load as 1st gear and are designed to spin at higher rpm’s than 1st gear.

5. Give and explanation of a gear ratio

If there are two gears both the same size with equal amount of teeth meshing, the gearing ratio will be 1:1 (1 to1) if however there are two gears at different sizes, (e.g, the driver gear small than the driven gear) than the ratio will be different. the way to work out ratios is simple as seen bellow:

How to get a gear ratio:

Count the amount of teeth in each gear and record weather it is the driver gear or driven gear like so (note, when you have the fraction of teeth from the input, use that as the start of each equation and multiply it by the other fractions you get from the gears*:

Then go to another set of meshed gears on the layshaft and out put shaft and count their teeth and record whether it is the driver or driven gear as stated above: 

Then multiply the two fractions as seen in the fist picture above:

Gearbox study

1. What type of gears are used for reverse in a manual gearbox?

a) give an explanation for your choice

2. What type of gears are used for all forward gears in a manual gear box?

a) give an explanation for your choice

3. What is the purpose of a synchromesh unit?

a) explain the operation of a synchromesh unit

b) what is the purpose of a Baulk/syncro ring

c) how do you check the baulk ring?

4. what type of bearings do we find in gearboxes

5. Give and explanation of a gear ratio

Valve timing

By: Ali, Alex, and Gareth

 

In four-stroke, and some two-stroke cycle engines, the valve timing is controlled by the camshaft, and can be varied by the cam lobes being modified slightly, or it can be varied during engine operation by the relatively new technology of variable valve timing.

An example of valve timing:

 

It is also affected by the adjustment of the valve mechanism, and particularly by the tappet clearance, although, this variation is normally unwanted. In many two-stroke engines, there are no camshafts or valves, and the port timing can only be varied by machining the ports and/or modifying the piston skirt, unlike supercharged two-stroke diesel engines. These engines have a cylinder head and camshaft similar to a four-stroke engine. 

A video explaining 4 stroke and 2 stroke engines

A two stroke Diesel cycle:

Why valve timing is important and valve overlap:

Valve overlap is the transition between the exhaust and inlet strokes and is a practical necessity for the efficient running of any internal combustion engine. It is necessary to begin opening the inlet valve before the piston reaches Top Dead Centre (TDC) on the exhaust stroke. Likewise, in order to effectively remove all of the combustion gases, the exhaust valve remains open until after TDC. Thus, there is a point in each full cycle when both exhaust and inlet valves are open.