This Instructable is on my Lego semi truck with two grain trailers behind it. (also called a super b or a b train) There are two kinds of grain trailers: open and closed ends. These are closed end trailers. I decided to go with a lid on the top instead of a roll cover, and they empty on the bottom with two slides. I made a bin that you drive under to fill up the trailers. Hope you enjoy it!

Step 1: The Semi

The semi is quite easy to build, and this one is quite similar to the semi trucks in my other Instructables. I have a single cab with step by step instructions on how to build it so you can use that and add a sleeper if you like. This semi is very low and sleek looking (which i like) however you can customize it if you want it a bit higher. It has a beam 2 flat pieces high through the whole semi, and the front uses fenders and the piece in front of the fenders for lights. I put an additional 6x2 bumper on the front. Once the main cab is built on top of the beams i start working underneath of the beams to finish off the bottom. The smoke stacks are a technic stick and a connector put into a 1x1 with a hole. I had first built a triple axle for the semi but then the grain trailers were too far a way from the cab which doesnt look nice. Moving on...

Step 2: The 1st Trailer

The first trailer is a little odd looking but that is how it is in real. You need two of the three axles to be behind the box and one under the box. The reason for this is because the 2nd trailer needs to connect behind it with a swivel hitch. The top of the trailer is flat pieces 6 wide, and leaving a hole in the middle for the lids. on both sides of the lid is a rounded off 4x2. the lid is a 4x2 with a handle on both sides and a 2x2 in the middle. This just sits nicely on the hole and is easy to open. The emptying system starts with a little wall angled off with a 2x1 with a little tab. After a 2x4 hole, there is another wall, this time double the width and have a tab on both sides. After another 2x4 hole, there is a wall just like the first one. The slides have the flat L piece on the end and the rest of the 6x2 is smooth pieces. This slides in and closes off the hole. The inside has angled 'roof pieces' on either side and a roof ridge on a 4x2 between the two openings. This makes the grain drain to the holes, and there won't be any stuck in the corners. (they have this in the real trailers too.)

Step 3: The 2nd Trailer

The second trailer doesn't look as odd as the first. It has two axles and both are under the rear of the trailer. The lid and drainage system is identical to the 1st trailer except for one thing. On the first trailer there is a smooth 1x4 on each side of the holes. In the 2nd trailer there is a 2x4 on the one side and nothing on the other side. This is because the holes and walls on the bottom had to be a certain distance away from the front so it could swivel without hitting the trailer in front. If i had moved it one more to the front it would have been hitting so that is the reason for the off centered lid and holes.

Step 4: The Bin

The bin is where the trailers are filled up with grain. It uses the same technology as the trailers with roof pieces to drain the grain down to the bottom. It has a slide also, with a tab inside so it stops when it is all the way closed and all the way open. This way the slide doesnt come all the way out. The bottom hole is as low as possible so there is barely any spill when you load up the trailers.

Step 5: Filling the Bin

I used some dried soybean seeds (I think) for the grain. You can also uses iron on beads, rice, corn, or anything along that line. The top of my bin is closed off with a little hole, and i used a funnel to fill up the bin. You can also leave a big hole for easier filling or whatever you like.

Step 6: Filling the Trailers

Filling the trailers and not spilling can be a challenge at first. If the openings are lined up on the bin and trailer there should be no spill. Just line them up and pull the slide. when it is full, close the slide.

!!!IMPORTANT!!!

*Overfilling will cause spills*

*Don't pull the slide slowly or only half the trailer will fill up*

*Trailer will not fit under bin with lids on*

Step 7: Emptying the Trailers

This is very easy. Pull the slides out of the bottom and wiggle the semi back and forth a little bit. Then drive forward and the bumpers fill push the grain into two strips. Have something to push it on a pile and put it back in the bin. (LEGO Front end loader? Hands? Dust pan?)