liners are use in the inside the cylnder body, inorder to maintain the life of the cylinder

1. AUTOMOTIVE ENGINEERING
Unit 1
Engine components, cooling and
lubrication systems
Topics;
1. Liners
2. Piston
3. Piston slaps

2. CONTENTS
1. LINERS
2. TYPES OF LINERS
3. COMPARISION ON TYPES OF LINERS
4. PISTON
5. CONTROLS OF PISTON SLAP

3. LINERS
• Liners is a hollow cylinder part, it is pressed into the
cylinder holes.
• Its form a barrels and reduces the cylinder wears.
• Life of cylinder bore is increases.
Fig 1 cylinder liners

4. Contt…
• Liners are replaced when it is wear out.
• When cylinder block is re-bored, liner are used to
restore the original size.
• Liners is hardened by chromium platting.
• It improves the resistance to wear and corrosion.

5. Fig 2 liners

6. Types of liners
• There are two types of liners
• Dry liners
• Wet liners
• Dry liners:
– Dry liners are thin and use block metal for full length
support.
– This are in the form of barrel, and flanges is provided at the
top.
– It keeps the liners in position.

7. Fig 3 Dry liners
Contt…

8. Contt…
– Both outer and inner side of liners are machining
accurately.
– Because of better contact with cylinder block.
– By shrinking the liners is put into the cylinder bore.
– If liners are loose fit with cylinder block
• Poor heat dissipation.
• It result higher operating temperature.
• Improper lubrication results piston scuffing.

9. Contt…
– If liners are Too tightly fit
• It produce distortion of cylinder block, liner cracking,
hot spots scuffing.
Fig 4 piston scuffing

10. Contt…
• Wet liners
– It is pressed into the bore and supported at top and bottom
only.
– Liners makes direct contact with cooling water on the outside.
– Hence don’t required accurate machining on the entire outer
surface.
– Three groves are provided at the bottom.
– In this middle is empty and top and bottom are inserted with
rubber packing.

11. Contt…
Fig 5 wet liners

12. Comparison of Dry and Wet Liners
Dry liners
• They may be provided either
in the original design.
• No leak proof joint is required.
• Construction is not simple.
• It does not make direct contact
with cooling water.
• Accurate machining in both
side is necessary.
Wet liners
• Have to be included in the
original design.
• Leak proof required.
• Construction is simple.
• Cooling water is in direct
contact with liner.
• Accurate machining in both
side is not necessary.

13. Piston
• It is a reciprocating part of the engine.
• It converts the combustion pressure in the cylinder to a force
on the crank shaft.
Functions
 It forms seal in the cylinder to avoid entry of combustible
gas into crankcase.
Transmit force of explosion to the crankshaft.
It acts as bearing for the gudgeon pin.

14. Contt…

15. Contt…
Fig 6 Typical piston

16. Contt…
Fig 7 piston Fig 8 piston with connecting rod

17. Controls of piston slaps
• Aluminum alloy piston with cast iron cylinder has a
drawbacks.
• If cold clearance is given , chance of danger of
seizure at high operating temperature.
• If it kept large engine knocks or slaps when cold .

18. Contt…
• Different methods are used to over come this difficulty.
They are
 Cutting horizontal slots
This makes heat away from the lower part of the piston
By cutting horizontal slots in the portion just below the oil
control ring,
Skirt portion does not become very hot
Fig 9 horizontal slot in piston
slot

19. Contt…
 Heat dam
Cutting a grooves near the top piston
Heat flow to lower part of piston can be reduce.
Piston skirts runs coolers
Fig 10 heat dam

20. Contt…
 Vertical or T slots
The top of T tends to retard the heat transfer from
head to the piston skirt.
It allows piston skirt without increase in diameter.
Fig 11 T slots in piston
T slot

21. Contt…
 Split skirt
Skirt is either partially or completely split.
When piston is warm and begins to expand, it cannot
bind in cylinder.
Fig 12 partially split piston Fig 13 completely split piston

22. Contt…
 Tapered pistons
 Crown side is being smaller in dia than the skirt end.
 Crown expose to high temp than skirt, that side expand more
than skirt side.
 Then piston dia is uniform under operating condition
 Special alloy pistons
 This alloy have coefficient of expansion nearly equals to that of
cast iron
 One such alloy is “LO-EX” alloy
 It consist of 12-15% silicon, 1.5-3%nickle, 1%magnesium and
copper.

23. Contt…
 Wire wound pistons
A band of steel wire is wounded between the piston
and oil control ring.
Thus restricting the expansion of skirt.
Fig 14 wire wound piston

24. Contt…
Bi metal pistons
Both metal steel & aluminum.
Steel for skirt
Aluminum alloy for piston head and pins
Steel have low coefficient of thermal expansion
Fig 15 bi metal piston