Minecart with Furnace

A minecart with furnace is a self-propelling minecart with a furnace inside. They can be used to move other minecarts.

Obtaining
Minecarts with furnaces cannot be retrieved by attacking them, as they drop a minecart and a furnace when broken. Despite this, they are renewable since the player is easily able to recraft them.

Usage
Minecarts with furnaces are placed the same as other minecarts. It does not have a graphical user interface, unlike a furnace.

Minecarts with furnaces can be powered, done by feeding fuel (coal or charcoal) into the furnace minecart with the button. The fuel is consumed immediately and it starts to move in the same direction the player clicked toward. Pressing always turns it to that direction, even when not holding coal.

Any piece of fuel, added at any time, increases the total range by an additional 3600 ticks (equal to 180 seconds or 3 minutes). The upper limit is 32767 ticks, approximately 27 minutes.

When powered, minecarts with furnaces cover 240m per minute (about 4 m/s, slightly slower than walking speed) or 720m per piece of coal. They do not accelerate beyond this speed when going downhill or on active powered rails, and as long as they remain powered, they do not slow down when going uphill, on inactive powered rails, or when pushing or pulling other minecarts.

If a powered furnace minecart gets derailed and then pushed back onto a rail, it starts moving again in the direction it came from (or is going to?), so they are not easily turned around in this state unless a player is nearby to redirect it with.

Minecarts with furnace can climb up steep inclines while pushing other minecarts for as long as they have fuel. If a minecart with furnace reaches a slope while pulling another minecart, the pulled minecart is switched to the forward position so that it can be pushed along the slope instead of pulled.

When a minecart with furnace bumps into another minecart or multiple minecarts, the other minecarts are pushed forward with great speed. The furnace minecart continues on with its own speed. Because of this speed difference, some of the minecarts may end up inside unloaded chunks on straight tracks.

Train mechanics
A furnace minecart can be made to pull up to four other minecarts. All minecarts in this train move at the constant speed of the furnace minecart. Trains are formed when a minecart is pushed into the back of a powered furnace minecart or a short-enough train. These shunts are fragile at best and easily come undone, but some methods are stronger than others. For example, pushing a minecart into a furnace minecart and then powering the furnace gives a weaker shunt than pushing the furnace minecart into the other minecart against a wall, and then powering the furnace in the other direction.

Pulling a minecart with TNT causes it to explode.

When a train comes to a turn, the shunt comes undone with the pulled minecart jettisoned backward. The correct way to make such a turn is having the shunt undone before a turn, and then make the two rejoin on a straight rail later by having the pulled cart catch up with the minecart with furnace.

Since the train runs slower on a fully powered track than a normal minecart (~5 m/s compared to 8m/s), a train pulled by an unpowered furnace minecart is ideal for AFK farms involving breaking or placing blocks like nether wart.

Properties
The coal is not stored as an item in the Entity, but in the object data in the fuel property as a time in ticks. Fuel is a short value, i.e. a maximum of 32767 ticks, which is less than 30 minutes. However, alone doesn't make it go since it doesn't have a direction. It can be right-clicked on a track to give it a direction, or it can be summoned with the properties PushX and PushZ set, which are responsible for the direction. Note that the  property every entity has allows for movement of the minecart, but it won't give the minecart the direction it needs to move on its own.

Entity data
Minecarts with furnace have entity data associated with them that contain various properties of the entity.

Trivia

 * The minecart with furnace is excluded from on purpose. In a tweet, Jeb considered removing it from.