Powered Rail

A powered rail is a type of rail that is used to decrease or increase the momentum of moving minecarts. When powered with redstone, powered rails will speed up any minecarts passing over. When turned off, they act as "brakes", and will slow down moving minecarts to a halt.

Crafting
Powered rails are crafted similarly to normal rails, but uses gold instead of iron, and adds redstone to the bottom.

Effects


Powered rails have two possible states: on or off.

A rail that is "off" slows any passing minecart by applying a frictional force. The force is generally strong enough to bring a moving minecart to a complete stop, or to hold a minecart in place on a slope. However, after going down a slope of 80 or more rail blocks, one non-powered powered rail cannot stop minecarts.

A rail in the "on" state will accelerate a minecart if any of the following is true:


 * 1) The minecart is already moving, in which case the cart is accelerated in the direction of motion.
 * 2) The minecart is stationary, but one end of the powered rail is up against a solid block. In this case, the cart is accelerated in the direction that is not blocked.
 * 3) The minecart is stationary, but the powered rail is on a slope. The instant the powered rail is activated, the brake is released and the cart will start moving down due to gravity. As the cart is now moving, rule (1) applies and the cart is accelerated in that direction.

The second and third cases can both be used to create simple stone button-activated launchpads. When the powered rail is off, carts are held in place, providing a safe way to load and unload carts without them derailing.

Powering
Power can be transmitted to the rail from any of the six adjacent positions (above, below, or any side) in the same way redstone is powered.

Powered rails will propagate power to each other if they are adjacent and part of the same track, for up to 9 blocks from the power source (1 being powered directly which is propagated to 8 adjacent rails). They will also receive power from any adjacent detector rails (when a cart passes over it), even if they are not part of the same track (which follows from the rules above). Because the detector rail powers attached rails, it could be used to activate power rails only when necessary:


 * For one-way travel, place a detector rail before the powered rail
 * For two-way travel, place a detector rail on both sides of the powered rail

In practice it is far more efficient to have powered rails constantly active using other means:


 * Place a redstone torch either next to the powered rail or two blocks underneath it or use powered redstone wiring to achieve the same effect
 * Place an activated lever on the bottom side of the block the powered rail is on (cheapest, only requires a stick and a cobblestone to make)
 * Place the powered rail on a block of redstone

Momentum
The speed of a cart which is boosted using Powered Rails is calculated to be at the maximum of 8 m/s, however the cart maintains an internal "momentum" value that keeps the cart at the maximum speed of 8 m/s until the excess momentum is depleted.

A single powered rail on flat ground against a stop block gives an occupied cart enough momentum to travel 80 rail tiles on a flat surface, or 8 tiles for an unoccupied cart (in Beta 1.5, this was 64 blocks and 8 blocks respectively). Tests show that putting several powered rails in a row has observable diminishing returns with each additional powered rail on how much farther a cart will travel. This implies that the momentum gained is smaller if the cart's speed is faster and vice versa.

Tests show that climbing slopes impact momentum severely, thus the cart speed plummets fast. However, if there is enough surplus momentum, carts will travel up slopes with ease. Conversely, carts traveling down slopes gain momentum. Downward sloped powered rails will add both the momentum from the rails and the momentum from going downhill to your cart.

Climbing slopes


Launching from rest via four powered rails, an occupied cart has enough momentum to climb a 1/1 slope 10 blocks high without further boosting and then travel horizontally at a very slow speed for at least a dozen blocks before coming to a stop. Such a cart does not have enough momentum to climb an 11 block high slope. An empty cart in a similar setup will only climb 5 blocks and then travel a few blocks horizontally.

When minecarts travel upslope without having sufficient stored momentum, a powered rail is needed 1 every 4 blocks to sustain movement all the way to the top of the slope, Alternatively, 2 every 8 blocks are somewhat easier to supply power to. However note this is a worst-case scenario where there is no momentum to start with.

If working with empty carts (for instance, a storage cart transport system), 1 powered every 2 blocks is necessary to sustain movement. To minimize powering requirements, 2 powered followed by 2 unpowered can also be used (analogous to loaded player-carrying carts).

When traveling up a slope at full speed (8 m/s) one powered rail will maintain full speed for two blocks high, meaning that alternating between powered and unpowered rails will maintain full speed up a slope. Consecutive powered rails on a slope will add more momentum, so eight powered rails can be followed by 8 normal rails, and full speed will be maintained while traveling up the slope. Less momentum is gained by each consecutive rail as the strip gets longer.

Optimal Use
A test was conducted by building straight tracks 2000 blocks long on level ground with different intervals of powered rails. The time to travel the full 2 km length on an occupied minecart was recorded with each interval. The following table lists the results:

3 powered rails in a row on flat terrain is sufficient to boost a minecart from rest to the maximum speed of 8 m/s.

Thereafter, the optimal spacing of powered rails on a level track is to use 1 every 38 blocks (that is, a repeating pattern of 1 powered rail followed by 37 normal rails, then another powered rail, and so on) which maintains a constant minecart speed of 8 m/s. If gold is in short supply, it is possible to use powered rails with more space between them at the cost of reduced overall speed.

However, the optimal spacing of torches is 1 every 13 blocks in order to keep the entire track lit at lightlevel 8 and above. So for aesthetic purposes, it might also be desirable to space out powered rails every 39 blocks with minimal speed losses, or to space them out at 1 every 36 blocks with torches 1 every 12 blocks.

An optimal use requires the synchronization of minecart movement and powered rail placement; moving a powered rail a single block forward or back along a track can make a significant difference. This is because the momentum of a minecart is increased per tick (=1/20 of a second) the cart spends on a powered rail (by 0.9 m/s for occupied carts). When a cart travels at the maximum 8 m/s on a straight track, it alternately spends either 2 or 3 ticks on each block. For an optimal placement, the powered rail must be put where the cart spends 3 ticks, otherwise one third of the boost is wasted.

A diagonal track is a track that consists of the pattern 'left corner' attached to a 'right corner' attached to a 'left corner' ... and so on. When minecarts travel on a diagonal track, the camera is held steady in the diagonal direction and the minecart visually travels diagonally along the track as well. The speed limit of minecarts is actually 8 m/s per cardinal axis, thus when traveling on diagonal tracks, the cart will travel 8 m/s in both cardinal directions of travel to result in a net vector of 11.3 m/s.

Because of this difference, there is also a difference between the optimal spacing of powered rails when used on a diagonal track when compared to straight travel on flat terrain. This is currently undetermined to high accuracy but is roughly 1 every 52 blocks.

There is also a difference in unmanned or storage mine carts so it is advisable to use a shorter interval if these carts will be used on the track.

It seems as if the optimal Powered Rail placing interval to make storage mine carts move is 4 (1 Powered Rail every 4th block). Compared to shorter intervals the reduction in speed is minimal. The maximal possible interval seems to be 9 as the minecart will not reliably reach its destination when using higher intervals.

Usage of detector rails
A Detector Rail will power 4 adjacent blocks and 2 blocks below it when a minecart, occupied or empty, is on it. This makes it possible to activate powered rails inline without redstone torches or wiring.

A detector can be used to activate adjacent powered rails. However, if the detector is used to activate more than two or three (depending on approach speed) powered rails, the rails will deactivate before the minecart reaches them, bringing the cart to an immediate stop.

One-way powered rail lines can be created by placing a detector rail before a powered rail. This way, occupied carts will only be boosted if they are traveling the proper direction. Carts going the "wrong" way will be brought to a stop because the powered rail is inactive.

Although inefficient, A two-way rail line can be created by placing detector rails on either side of the powered rail.

Alternately, placing powered and detector rails on a 1x1 slope will not propel a cart more than 3 blocks upward if there is not enough initial momentum. The cart will lose too much speed on the incline, meaning it can't make it from the detector rail to the powered rail before the powered rail returns to the "off" state. If the cart is in a train of two or more carts, the last car in the train will become stuck instead.

A detector rail could also be used to activate an event based on a cart's location. For example, a fail-safe can be created to release a stopped cart in order to prevent a collision with an arriving cart. The arriving cart passes over a detector rail, activating a powered rail that boosts the resting cart away.

Additional properties


Curved power rails only exist in the case where the final direction is towards the east (with the powered rail appearing in the north-south orientation), or in a T-junction where one path faces east along a north/south track. It is possible to make a one-way curved railway using power rails, but not a bi-directional one.

When placing rails, regular rails prefer to curve towards the powered rail. In cases such as these, the south-west rule applies.

A cart traveling on a powered rail that collides with an object (wall, single block, player, other cart) will reverse direction. It will not reverse direction if it collides with a translucent block, such as Stone Slabs or Glass. If a track including powered rails is bordered by blocks acting as "buffers", the cart will indefinitely continue back and forth along the track. Having carts interact with each other on a short track designed this way can be used to chain multiple carts together as a "train". Once aligned, they will all move together at relatively the same speed.

How far the charge passes down adjacent rails is independent of the length of redstone wire. Even if the rails are connected to a redstone torch by 15 blocks of redstone dust, the 8 adjacent rails will still be powered normally despite the fact that they should be out of range for the torch.

Stop points
It is possible to make points in your track where a cart is stopped and then jumpstarted again by player input. This can be useful for creating checkpoints to certain sites of interest in your world. This can be done by using two powered track pieces on a one block incline, by having the first powered track piece going down, with the second powered track piece at the bottom and a button placed alongside the second powered track piece, so that the button is directly above the track. You can see an animated example of this stop point if you click on the image to the right.
 * Stop Point.GIF

When the cart comes to this point it will stop On the incline, allowing the cart to use gravity to start the boost when the button is pushed. Players can then either stay in the cart and carry on to the next stop, or leave the cart at the station for themselves/other players to use later.

A "two-way" stop can be made by combining two of the normal stops with a detector rail in between. This will pause a minecart travelling in either direction and allow them to be restarted by pressing a button.

Starting boost
To create a simple initial boost device using 2 powered rails, dig a hole 1 block deep and 2 blocks long. Place the powered rails inside the trench, connect one end to the track that you wish the mine cart to exit. Finally place the mine cart on the powered rail. Once power is applied to the rail the minecart will be boosted out.

Momentum boost/Climb boost
Note: This trick seems to be outdated in the 1.5 update.

It is possible to reach a remarkable height with just using 4 powered rail by using a 3x3 loop with 4 powered rail that is connected with a T switch to the slope. A cart is placed on the loop and allowed to spin around for a few seconds to build up momentum beyond the speed limit. The best practice is to have a switch with a delay to switch the T section to alternate between a loop and the uphill section. The player switches the loop so it will go uphill, because of the delay the player can get in the cart and the cart will loop a few times building up momentum until the delayed switch of the T-section shoots the player uphill. With just a few seconds of building up momentum, you will reach the cloud layer if sea level was used as starting point. You can make a loop with 3 rails instead of four which is more effective, as seen here. You can implement this trick in a minecart arrival/depart station, as seen here. You can avoid using stacks of redstone for delay repeaters by using a water timer, as seen here.

When making use of this mechanism (assuming the delay it takes for a dispensed item to travel in 8 blocks of water and without additional friction); an occupied minecart will travel at full speed for approximately 330 blocks on a flat horizontal surface (after which momentum loss will become visible as a loss of speed will occur). When making use of this same mechanism to gauge vertical climb at full speed before speed loss occurs - one can observe an occupied minecart able to climb approximately 60 blocks before speed loss occurs.

This leads us to surmise that: Each block climbed vertically consumes approximately the same momentum as travelling 5.5 blocks horizontally. With this knowledge in hand, it is easy to calculate whether the distance you wish to traverse can sufficiently be overcome with this booster; and whether additional support will be necessary.

Trivia

 * For comparison of speeds, walking speed is about 4 m/s (4.27 exactly), thus using powered rail to speed up will almost double your traveling speed.
 * In the game code, powered rails are referenced as "goldenRail".
 * Powered rails were originally a suggestion for golden tracks.
 * A redstone torch or any other power supply will only power a powered rail for 9 blocks, unlike the 15-block range of regular redstone.
 * If you put down a row of powered rails and put another one in a different direction at the end of the row, a minecart will turn like a normal rail.
 * Creative Mode Flying is faster than traveling by powered rail.
 * In pocket edition powered rails are always powered.