Cara Kerja Mesin 4 Tak dan 2 Tak

Cara Kerja Mesin 4 Tak

Mesin 4 tak adalah sebuah mesin dimana untuk menghasilkan sebuah tenaga memerlukan empat proses langkah naik-turun piston, dua kali rotasi kruk as, dan satu putaran noken as.

• Langkah hisap

Tujuan langkah hisap yaitu memasukkan kabut udara – bahan bakar ke dalam silinder.  Sebagaimana tenaga mesin diproduksi tergantung dari jumlah bahan-bakar yang terbakar selama proses pembakaran.

Proses hisap :

1. Piston bergerak dari Titik Mati Atas (TMA) menuju Titik Mati Bawah (TMB)
2. Klep inlet terbuka, bahan bakar masuk ke silinder
3. Kruk As berputar 180 derajat
4. Noken As berputar 90 derajat
5. Tekanan negatif piston menghisap kabut udara-bahan bakar masuk ke silinder

• Langkah kompresi

Dimulai saat klep inlet menutup dan piston terdorong ke arah ruang bakar akibat momentum dari kruk as dan flywheel (noken as).

Tujuan dari langkah kompresi yaitu untuk meningkatkan temperatur sehingga campuran udara-bahan bakar dapat bersenyawa. Rasio kompresi ini juga nantinya berhubungan erat dengan produksi tenaga.

Proses kompresi :

1. Piston bergerak kembali dari TMB ke TMA
2. Klep In menutup, Klep Ex tetap tertutup
3. Bahan Bakar termampatkan ke dalam kubah pembakaran (combustion chamber)
4. Sekitar 15 derajat sebelum TMA , busi mulai menyalakan bunga api dan memulai proses pembakaran
5. Kruk as mencapai satu rotasi penuh (360 derajat)
6. Noken as mencapai 180 derajat

• Langkah tenaga

Dimulai ketika campuran udara/bahan-bakar dinyalakan oleh busi. Dengan cepat campuran yang terbakar ini merambat dan terjadilah ledakan yang tertahan oleh dinding kepala silinder sehingga menimbulkan tendangan balik bertekanan tinggi yang mendorong piston turun ke silinder bore. Gerakan linier dari piston ini dirubah menjadi gerak rotasi oleh kruk as. Enersi rotasi diteruskan sebagai momentum menuju flywheel yang bukan hanya menghasilkan tenaga, counter balance weight pada kruk as membantu piston melakukan siklus berikutnya.

Proses langkah tenaga :

1. Ledakan tercipta secara sempurna di ruang bakar
2. Piston terlempar dari TMA menuju TMB
3. Klep inlet menutup penuh, sedangkan menjelang akhir langkah usaha klep buang mulai sedikit terbuka.
4. Terjadi transformasi energi gerak bolak-balik piston menjadi energi rotasi kruk as
5. Putaran Kruk As mencapai 540 derajat
6. Putaran Noken As 270 derajat

• Langkah buang

Tujuan dari langkah buang yaitu untuk menghasilkan operasi kinerja mesin yang lembut dan efisien. Piston bergerak mendorong gas sisa pembakaran keluar dari silinder menuju pipa knalpot. Proses ini harus dilakukan dengan total, dikarenakan sedikit saja terdapat gas sisa pembakaran yang tercampur bersama pemasukkan gas baru akan mereduksi potensial tenaga yang dihasilkan.

Proses langkah buang :

1. Counter balance weight pada kruk as memberikan gaya normal untuk menggerakkan piston dari TMB ke TMA
2. Klep Ex terbuka Sempurna, Klep Inlet menutup penuh
3. Gas sisa hasil pembakaran didesak keluar oleh piston melalui port exhaust menuju knalpot
4. Kruk as melakukan 2 rotasi penuh (720 derajat)
5. Noken as menyelesaikan 1 rotasi penuh (360 derajat)

• Overleving

Overlap adalah sebuah kondisi dimana kedua klep intake dan out berada dalam possisi sedikit terbuka pada akhir langkah buang hingga awal langkah hisap.

Berfungsi untuk efisiensi kinerja dalam mesin pembakaran dalam. Adanya hambatan dari kinerja mekanis klep dan inersia udara di dalam manifold, maka sangat diperlukan untuk mulai membuka klep masuk sebelum piston mencapai TMA di akhir langkah buang untuk mempersiapkan langkah hisap. Dengan tujuan untuk menyisihkan semua gas sisa pembakaran, klep buang tetap terbuka hingga setelah TMA. Derajat overlaping sangat tergantung dari desain mesin dan seberapa cepat mesin ini ingin bekerja.

manfaat dari proses overlaping :

1. Sebagai pembilasan ruang bakar, piston, silinder dari sisa-sisa pembakaran
2. Pendinginan suhu di ruang bakar
3. Membantu exhasut scavanging (pelepasan gas buang)
4. memaksimalkan proses pemasukkan bahan-bakar.

Cara kerja mesin 2 TAK

Jika mesin 4 tak memerlukan 2 putaran crankshaft dalam satu siklus kerjanya, maka untuk mesin 2-tak hanya memerlukan satu putaran saja. Hal ini berarti dalam satu siklus kerja 2 tak hanya terdiri dari 1 kali gerakan naik dan 1 gerakan turun dari piston saja.

• Langkah pertama

Piston bergerak dari TMA ke TMB.

1. Pada saat piston bergerak dari TMA ke TMB, maka akan menekan ruang bilas yang berada di bawah piston. Semakin jauh piston meninggalkan TMA menuju TMB, tekanan di ruang bilas semakin meningkat.
2. Pada titik tertentu, piston (ring piston) akan melewati lubang pembuangan gas dan lubang pemasukan gas. Posisi masing-masing lubang tergantung dari desain perancang. Umumnya ring piston akan melewati lubang pembuangan terlebih dahulu.
3. Pada saat ring piston melewati lubang pembuangan, gas di dalam ruang bakar keluar melalui lubang pembuangan.
4. Pada saat ring piston melewati lubang pemasukan, gas yang tertekan dalam ruang bilas akan terpompa masuk dalam ruang bakar sekaligus mendorong gas yang ada dalam ruang bakar keluar melalui lubang pembuangan.
5. Piston terus menekan ruang bilas sampai titik TMB, sekaligus memompa gas dalam ruang bilas masuk ke dalam ruang bakar.

• Langkah kedua

Piston bergerak dari TMB ke TMA.

1. Pada saat piston bergerak TMB ke TMA, maka akan menghisap gas hasil percampuran udara, bahan bakar dan pelumas masuk ke dalam ruang bilas. Percampuran ini dilakukan oleh karburator atau sistem injeksi.
2. Saat melewati lubang pemasukan dan lubang pembuangan, piston akan mengkompresi gas yang terjebak dalam ruang bakar.
3. Piston akan terus mengkompresi gas dalam ruang bakar sampai TMA.
4. Beberapa saat sebelum piston sampai di TMA, busi menyala untuk membakar gas dalam ruang bakar. Waktu nyala busi sebelum piston sampai TMA dengan tujuan agar puncak tekanan dalam ruang bakar akibat pembakaran terjadi saat piston mulai bergerak dari TMA ke TMB karena proses pembakaran sendiri memerlukan waktu dari mulai nyala busi sampai gas terbakar dengan sempurna.

Top 13 Polar Super Vehicles from Antarctic

Living and working in a polar region like Antarctic isn’t just walking around in layers upon layers of protective clothing. Sometimes you need to cover long distances and that’s where all the exciting polar vehicles come in handy.
After some research, I found out that the people in Antarctic have lots of vehicles to play with. All of them are far more exciting that the car in my garage, so I couldn’t resist making this top 13 of the most exciting polar vehicles in Antarctic.

13. Science Support Vehicle

A heavily modified Ford truck for the Moon Regan expedition. It comes with six-wheel drive, a 7.3 liter V8 engine and a total length of 6.5 meters. Total weight is close to 5 ton.

12. Piston Bully

A common general utility vehicle in Antarctic. The Piston Bully can also be found in less exotic locations working on ski slopes and mountain trails.

11. Double Hagglund

Swedish all terrain vehicle. It is available as both a single section and double section vehicle. The one pictured here is the double section version – apparently there is an engine in both sections of this vehicle!

10. Delta Truck

Big-wheeled truck that is being used to transport up to 20 passengers around in Antarctic. It doesn’t have any belts, so it cannot be used in deep snow.

9. Spryte

A belted vehicle for transporting passengers around. A nice alternative to the Delta if the conditions require it (deep snow, creavasses and so on).

8. Terrabus

The Terrabus is one of the rarest vehicles in the world. Apparently there exist less than ten of these vehicles in the world.
The Terrabus was originally designed for tourists, but now they are almost exclusively used on polar bases in Antarctic.

7. Tucker Sno Cat

A bit like the Mattrack Truck below, but with bigger belts which makes it perform better in deep snow and more able to cross creavasses. The Tucker Sno Cat is born with belts on – it’s not a modified vehicle where belts have replaced the normal wheels.

6. Foremost Nodwell

The Foremost Nodwell is a belted vehicle that is mass produced like the Piston Bully and the Tucker Sno Cat. The Foremost Nodwell pictured here is a fire truck (who would have guessed they had fire trucks in Antarctic).

5. Foremost Cheiftain

Another polar fire truck from Antarctic. This one is a slightly bigger Foremost fire truck that is used on airfields.

4. Mattrack Truck

A standard truck where the wheels have been replaced by mattrack belts. The company Mattrack can apparently do this to any kind of 4×4 vehicle – from ATVs to 20 ton trucks.
The short belts allow the Mattrack Truck to drive almost anywhere unless the snow gets to deep. If the snow gets to deep, longer belts are required (like on the Piston Bully). The short belts also make Mattrack Truck able to cross small creavasses, while larger creavasses require longer belts.

3. Mars-1 Humvee

Experimental exploration vehicle based on the Humvee ambulance design. Modifications include mattrack belts and a big rear cab with work and living space for up to four researchers.

2. Snow Cruiser

A classic vehicle that was constructed in 1939. It had a length of more than 18 meters and was more than 6 meters wide. It was powered by two 6 cylinder engines with a total output of 300 hp.
Unfortunately the Snow Cruiser failed to live up to the expectations. Once it arrived in Antarctica, the tires sank deeply into the snow and ruined any performance this vehicle might have had in areas without ice and snow.
And yes, it is a small plane that is being carried by Snow Cruiser!

1. Concept Ice Vehicle (CIV)

An ultra-light concept vehicle that runs on bio-fuel. It weights only 360 kg, so it can be dragged across the ice if necessary. Top speed is an impressive 85 mph (most other polar vehicles cannot go faster than around 30 mph).
The CIV is being used as part of the Moon Regan expedition (like the Science Support Vehicle at the top of this page).

Top 10 Heaviest and Biggest Military Tanks Ever

Military tanks are an impressive sight that makes enemy infantry shake in fear, but sometimes that isn’t enough. Sometimes you need to make the enemy flee in terror. That’s where the super heavy tanks come in.
Super heavy tanks is the classification for the heaviest and biggest military tanks. Almost all of the super heavy tanks were constructed by mad engineers around the time of WWII. Especially the Nazi engineers where more crazy than most – or maybe they were just allowed more freedom in a desperate attempt to turn the tide of the war.
Here are the top 10 heaviest and biggest military tanks ever.

Landkreuzer P. 1500 Monster

In 1942 Hitler approved the design and construction of an extremely large tank, but the project was cancelled in 1943 before any actual construction had begun. The tank was supposed to be more than fifteen times as big as a normal tank and it should have been armed with a 800 mm Krupp cannon (the main cannon on a normal tank like the M1 Abrams is 105 mm).
The 800 mm Krupp cannon is the largest artillery weapon ever built. Each projectile weighted 7 tons and it could be fired up to 37 km (23 miles). I haven’t seen any pictures of the Landkreuzer P. 1500 Monster, so you must make do with a picture of the Krupp cannon (check out the soldier in front of the cannon).


Landkreuzer P. 1500 Monster
Germany, 1942 – 42 meters long, weight 1500 ton, crew 100

Landkreuzer P. 1000 Ratte

The Ratte was very similar to the Monster. It was also designed in 1942 and it was also cancelled within little more than a year. Unlike the Monster, the Ratte were supposed to be armed with a warship turret with two 280 mm cannons. Other armaments on the Ratte would have included a 128 mm cannon, eight 20 mm anti-aircraft guns and a few 15 mm machine guns.




Landkreuzer P. 1000 Ratte
Germany, 1942 – 35 meters long, weight 1000 ton, crew 20
Some German guy have built a model of the Landkreuzer P. 1000 Ratte. His last picture of the model really gives you an idea about the size of this thing.

Panzer VIII Maus

The Panzer VIII Maus is the biggest tank ever built. It was small compared with the Monster and the Ratte, but still three times bigger than a normal tank. The design was complete in 1942 and production started in 1942, but only two were completed before the war ended.
The completed tanks were armed with a 128 mm primary cannon and a 75 mm secondary cannon.




Panzer VIII Maus
Germany, 1944 – 10 meters long, weight 188 ton, crew 6

E-100 Tiger-Maus

A super heavy tank very similar to the Panzer VIII Maus. This project was also started in 1942, but no models were ever completed. A single hull was built in 1944, but no turret was fitted before the war ended.
The E-100 Tiger Maus was supposed to use the same turret as the Panzer VIII Maus. Thanks to a lighter weight, it would have been faster and more practical on the battlefield than the Panzer VIII Maus.


E-100 Tiger-Maus
Germany, 1943 – 10 meters long, weight 140 ton, crew 5

FCM F1

The FCM F1 is the heaviest and biggest tank not of Nazi origin. It was supposed to replace the Char 2C, which is one of the heaviest tanks to ever see combat. Unfortunately France was defeated before the FCM F1 project was completed, so none of these tanks were ever built.
The FCM F1 was supposed to have a 90 mm cannon, a 47 mm cannon and six machine guns. It is worth noticing that this tank was more than 10 meters long, but still only a little bit more than 3 meters wide so it could be transported by train.


FCM F1
France, 1940 – 11 meters long, weight 139 ton, crew 9

O-I

The O-I was a Japanese attempt at building a super heavy tank. It has been reported that one model was completed and sent to Manchuria during WWII, but it is highly unlikely that the rumor is true. The O-I probably ended up as a cancelled project in much the same way as most of the other super heavy tank projects.
The O-I had three turrets. The main turret had a 105 mm cannon, one of the minor turrets had a 37 mm cannon and the other minor turret had three machine guns.


O-I
Japan, 1944 – 10 meters long, weight 130 ton, crew 11

K-Wagen

The K-Wagen was one of the first attempts at building a super heavy tank. Again it was the mad engineers of Germany that did the attempt, but for once it was before the Nazi era.
The K-Wagen didn’t have a main turret. Instead it had four 77 mm fortress guns mounted on the sides and seven machine guns. It is the second largest tank ever built – only the Panzer VII Maus is bigger since all the other super heavy tank projects were cancelled before they could be completed.




K-Wagen
Germany, 1917 – 13 meters long, weight 120 ton, crew 27

T-28 (Gun Motor Carriage T95)

The T-28 was designed by US Military during WWII. It was supposed to be used to break through German defenses and an eventual invasion of Japan.
The T-28 didn’t have a normal turret, so one might classify it as a tank destroyer and not a super heavy tank. This is probably the reason it was renamed from T-28 to Gun Motor Carriage T95 and later back again.
It was armed with 105 mm cannon and a single machine gun. It was so heavy that it had to use four tracks instead of the normal two.


T-28
USA, 1945 – 11 meters long, weight 95 tons, crew 8

TOG2

The TOG2 was the largest British tank ever built. Just like most of the other super heavy tanks, it was designed during WWII. A single prototype was completed in 1941, but no further development occurred and no TOG2 ever saw combat.
The TOG2 was armed with a 76 mm main cannon.


TOG2
United Kingdom, 1940 – 10 meters long, weight 80 tons, crew 8

A39 Tortoise

Another British super heavy tank. The problem with this one was that the first prototype weren’t completed before 1946, by which time the interest in super heavy tank development had disappeared.
The A39 Tortoise was armed with a 96 mm cannon and three machine guns.


A39 Tortoise
United Kingdom, 1944 – 10 meters long, weight 78 tons, crew 7

How Big Were They Really?

Check out this diagram, that I have glued together:


Be aware that the two biggest tanks (Landkreuzer P. 1500 Monster and Landkreuzer P. 1000 Ratte) never made it past the design phase, so they might have ended up looking very different from above. I just glued their pictures together from pictures of other tanks, so you could get an idea about how enormous they were.

Why Did They Disappear?

It is interesting that almost all the tanks in the top 10 were built during WWII. What made the engineers at that time try to build such monsters and why have no such tanks been built ever since?
The main reason for building the super heavy tanks was immunity from enemy fire. A super heavy tank would have featured thick armor that would be impenetrable to most WWII weapons. Being able to move around on the battlefield without fearing enemy fire would have been quite an advantage, but unfortunately it wasn’t possible to be immune from everything.
Enemy aircraft would surely target a super heavy tank on the battlefield, since it would be a big and easy target. Escape would be impossible for most super heavy tanks, since they would to slow to move away from the enemy fire.
Today, enemy fire is much more powerful than during WWII. It is easy to imagine how rockets or missiles could destroy a super heavy tank much easier than a group of smaller tanks.
The lack of defenses against air strikes weren’t the only problem with the super heavy tanks. The construction of such a monster would require enormous amounts of raw materials – something that was in short supply during WWII and probably used better elsewhere.
Another problem would be the transportation of a super heavy tank. Most of them were too big to be transported by train, so they would have to rely on their own ability to move forward. Problem was that most of them were extremely slow, so they might not reach the battlefield before it was too late.
In addition, the super heavy tanks were often so heavy that they would destroy normal roads. They would therefore have to drive through fields and so on, which meant even slower movement than were possible on normal roads.