Indestructable Wooden Tractor Toy

Pretty much exactly 1.5 decades!!! ago I built this wooden tractor & trailer toy and gave it to my newborn and 2 year old nieces as a present. After 14 years of abuse from my two nieces my brother's family passed it down to my 2 and 4 year old sons to play with. So far it has survived another year and truly deserves the certificate "Indestructible".
The intensive playing and "quality control testing" during the past 15 years is indicated by (i) almost polished wooden surfaces due to constant use, (ii) pen markings, and (iii) other marks that look like the tractor had an accident with a hammer at one point in time. However the tractor survived unphased. Not a single part has been broken.

In this instructable I am reconstructing how I built the toy back in the day. I am showing current photos of the assembled toy, 2D drawings of all the individual parts (except the screws), and step by step assembly instructions drawn from memory and illustrated by SolidWorks 3D drawings and photos as much as possible.
Note that the dimensions are all metric since this indestructable tractor was "Made in Germany". However, the thickness of most boards and dowels is not very critical and all dimensions can be adapted to the materials, hole saws, drills and screw sizes that are available to you. In my drawings I show mm units together with [inches] for your convenience.
I hope this instructable will lead to more kids enjoying more wooden tractor toys in the future.
If that is the case, please share your pics and comments.

The tools I used:
Hole saws with 50mm [1.969"] and 62mm [2.441"] diameter
Jig saw with thin blade that allows cutting relatively small radii in wood
Hand saw
Sand paper
Drill press (not shown)
Wood drills or general purpose drill bit set
Centre punch
Hammer
2 Clamps
Wood glue
Level
Callipers
Ruler
Lathe (for metal hitch, not shown)
File for metal
Small vice
Aluminum or Wood brackets to protect wood from marks when clamping down parts in vice

In this section I am listing the materials that I used. Other than the screws and dowels, I only used materials that I had lying around.
Note that the wood and dowels are easily exchangeable with other thicknesses / diameters. So are the screw dimensions. I'll point out on a few occasions what hole dimensions you'll have to adjust to accommodate different screw sizes. Please let me know if you have any specific questions.

Wood:
Here is a list of the thickness of all the wood pieces that I used. The exact dimensions can be taken from the drawings shown in the next step:
9.5mm [0.374"] thick for "Tractor Top"
13mm [0.512"] thick for "Tractor Frontwheel"
16mm [0.630"] thick for "Trailer Axis"
20mm [0.787"] thick for "Tractor Front Axis" and "Trailer Wheels"
25mm [0.984"] thick for "Tractor Side"
28mm [1.102"] thick for "Tractor Backwheel"
30mm [1.181"] thick for "Trailer Cart"
38mm [1.496"] thick for "Tractor Main Body"

Wood Dowels:
These or very similar sizes should be available at any department store such as Lowes or Home Depot. You can also find them at arts and craft stores or online. The picture is just an example to show that they come in various diameters.
8mm [0.315"] diameter, total length about 2m [7'] for "Tractor Top Support", "Tractor Steering Wheel Shaft" and "Trailer Rods".
10mm [0.394"] diameter, total length about 0.6m [2'] for "Tractor Steering Mechanism Axis" and "Tractor Trailer Railing"
25mm [0.984"] diameter, total length about 50mm [2"] for "Tractor Steering Mechanism Bottom", "Tractor Steering Mechanism Top", and "Tractor Steering Wheel"

Metal:
Bar 15mm [0.591"] wide, 2mm [0.079"] thick for "Trailer Hitch"
Plate, 1mm [0.039"] thick for "Tractor Hitch"
Rod 6mm [0.236"] diameter, 44mm [1.732"] long for "Tractor Hitch Pin"

Hex Lag screws:
I am showing some examples for hex lag screws in the picture. They are not the ones I have used for this toy, but rather to give you an idea what these screws look like. I used:

2x 5mm [0.197"] diameter, length 35mm [1.378"] with min. 15mm [0.591"] no thread area
2x 5mm [0.197"] diameter, length 45mm [1.772"] with min. 20mm [0.787"] no thread area
2x 5mm [0.197"] diameter, length 60-70mm [2.362-2.756"] with min. 35mm [1.378"] no thread area

The 5mm [0.197"] screws have a nominal diameter of 5mm [0.197"], and a core diameter of 3.5mm [0.138"]. Because of these dimensions, I drilled all clearance holes for the screws with 6mm [0.236"] diameter and all pilot holes for fastening the screws with 3.5mm [0.138"]. If you have a wobbly drill, use slightly smaller drills for the pilot holes to assure a tight fit.

It's a good idea to test how well your pilot hole works with your screw. Grab a piece of wood, drill a hole. Screw your hex lag screw into it. It should go in nice and tight. If it goes too loosely, switch to a size smaller. If it is too tight, the wood may crack. Pick a size larger.
Also, I remember that I was concerned about thread sticking out into the "bearing area" that the wheels turn on. I was able to find 5mm [0.197"] screws that had the appropriate shaft length to prevent unnecessary friction.

All 5mm [0.197"] metric screws can be substituted with 1/4" hex lag screws. The nominal diameter is 6.35mm [0.250"] and the core diameter is 4.394 [0.173"] according to this link. For 1/4" screws the clearance holes need to be about 7mm [0.276" = ~9/32"] and the pilot holes 4mm [0.157" = ~11/64"].

Screws for fastening the hitches:
To fasten the hitches to the tractor and the trailer I used "Oval Head Screws for Sheet Metal", because I had them in my stash.
You can get them at any convenient store such as home depot or lowes.
Since I don't have a picture, check out this McMaster link that shows a CAD drawing of a similar screw size than the one I used for the tractor.
Whatever screws you use, make sure you check your hole sizes and adjust them accordingly.

Washers:
I used 14x M5 washers. They should be available in any hardware store or here.
You need to substitute the washers with standard 1/4" washers if you pick 1/4" screws.
By the way, a good resource to look up washers and screws and other stuff is the website www.mcmaster.com. They have all kinds of different stuff, often with CAD drawings where you can check out the details. For example here is their page for metric washers.

In this section you'll find a list of the parts you need to make, the quantities needed, and their CAD drawings.
I am showing one example drawing as picture to give you an idea what the pdf files look like.

Tractor
The tractor is built out of a total of 18 wooden parts, 2 metal parts, 10 washers, and 6 screws:
2x "Tractor Backwheel"
1x "Tractor Front Axis"
2x "Tractor Frontwheel"
1x "Tractor Hitch"
1x "Tractor Hitch Pin"
1x "Tractor Main Body"
2x "Tractor Side"
1x "Tractor Steering Mechanism Axis"
1x "Tractor Steering Mechanism Bottom"
1x "Tractor Steering Mechanism Top"
1x "Tractor Steering Wheel"
1x "Tractor Steering Wheel Shaft"
1x "Tractor Top"
4x "Tractor Top Support"

Trailer
The trailer is  built out of a total of 18 wooden parts, 1 metal part, 4 washers, and 2 screws:
1x "Trailer Axis"
1x "Trailer Cart"
1x "Trailer Hitch"
2x "Trailer Railing"
12x "Trailer Rib"
2x "Trailer Wheel"

Cut all dowel pieces to length using the hand saw or a band saw if you have one. DON'T use the Jig saw. It is dangerous and the potential time saving is not worth the risk. Remember that when you cut something you remove material. To get the same length for multiple pieces, mark the length of the first piece you are cutting from the edge, then cut it. Use this first piece as a template to mark the next piece. That saves time and creates a good reproducibility.
For cutting you can hold the dowels with a small vice. Use aluminium or wood pieces between dowels and the chucks of the vice to avoid leaving ugly marks.
Also, remember this is a toy. After cutting the dowels carefully sand the cutting surfaces and edges with the sandpaper until the risk of splinters and sharp edges is completely eliminated.

8mm [0.315"] diameter dowel pieces:
4x "Tractor Top Support" => 70mm [2.756"] length
1x "Tractor Steering Wheel Shaft" => 50mm [1.969"] length
12x "Trailer Rib" => 120mm [4.724] length

10mm [0.394"] diameter dowel pieces:
1x "Tactor Steering Mechanism Axis" => 87mm length
2x "Trailer Railing" => 250mm [9.843"] length
After cutting, clamp one of the "Trailer Railing" parts horizontally into the vice again using protective aluminum or wood brackets. Wood brackets are actually preferrable in this step, since they are much less threatening to your drill bit in case you get accidentally out of alignment.
Place the dowel part exactly parallel to the drill press table again using the level. Mark the six hole positions shown in the drawing for "Trailer Railing". If you are using general purpose drills, use the center punch and hammer to create an indent at the exact drill location. You don't need to do this if you have wood drills that have a little protruding center part that prevents walking. Confirm that the part is still parallel to the drill press table and has not moved when using the center punch. Set the depth gauge of the drill press to drill 5mm into the dowel. It may be a good idea to drill a test hole into a leftover piece of dowel material before drilling. Drill the six holes.
Repeat with second 'Trailer Railing' part.

25mm [0.984"] diameter dowel pieces:
The three dowel parts with a 25mm [0.984"] diameter all need a center hole drilled before you can cut them:
Find a dowel piece that is at least 50mm [1.969"] long. On both of the two flat sides, mark the middle of the dowel with a pen. Depending on your drills, use the center punch to indent the drill location.
Clamp the dowel into a vice with the marked flat side up. Make sure it is exactly vertical using the level.
Clamp an 8mm [0.315"] drill into your drill press. Make sure your drill is aligned and centered with the dowel. Drill a 10mm [0.394"] deep hole into the center of the 25mm [0.984"] dowel.
Take the dowel out of the vice and turn the other flat side to the top. Use the level to put the dowel into an exactly vertical position.
Exchange the 8mm [0.315"] drill in the drill press with a 10mm [0.394"] drill. Center and align your dowel and drill.
Measure the width of the blade of your hand saw. Add this width to 36mm [1.417"] and drill this depth into the center of the dowel. For example if the blade of your hand saw is 2mm [0.079"] wide, drill 38mm [1.496"] deep into the dowel.
Now cut
1x "Tractor Steering Mechanism Bottom" => 25mm [0.984"] diameter, 21mm [0.827"] length
from the side with the 10mm hole, followed by
1x "Tractor Steering Mechanism Top" => 25mm [0.984"] diameter, 15mm [0.591"] length.
Finally cut
1x "Tractor Steering Wheel" => 25mm [0.984"] diameter, 8mm [0.315"] length
off of the other side.
Sand all parts carefully.

In my case the "Tractor Front Axis" and "Trailer Axis" were leftover wood pieces that I only had to cut to length. They can, of course, be cut out of board material as well.
For the "Tractor Front Axis" my dimensions were 20mm [0.787"] x 20mm [0.787"] x 73mm [2.874"]. This can easily be substituted by a 1x1 bought at Home Depot or Lowes which according to this source is 19mm [0.748"] x 19mm [0.748"].
For the "Trailer Axis" my dimensions were 32mm [1.260"] x 16mm [0.630"] x 84mm [3.307"].
You could also use a 1x1 for this part.
However, ensure that the length specifically of the "Trailer Axis" is at least 3mm [0.118"] wider than the width of your "Trailer Cart".
Mark the length of your pieces.
Clamp your wood down onto a solid surface and cut it carefully with your Jigsaw.
Carefully deburr all edges with sandpaper.

Drilling:
Mark the centre of the smallest sides of the "Trailer Axis" to prepare for drilling a pilot hole for the screws. As before, depending on the drill you have available, use the hole punch to indent the location.
For 5mm diameter hex lag screws use a 3.5mm drill diameter.
For 1/4" screws use a 11/64" drill diameter.
Using wood or aluminium brackets as protection, clamp the part vertically in your vice, using your level to align it. Align and centre your drill above the part. Drill.
Although the drawing shows a specific depth, which fits to the screws I used, you can drill this hole as deep as you like. You can even make it a through hole. This hole will prevent the wood from splitting when a screw is inserted. If your drill is too short for a through hole, repeat the procedure on the other side of the part.

Repeat with "Tractor Front Axis". Additionally mark the centre on one of the longer sides. Again use a centre punch if necessary to prepare for drilling. Set your depth gauge to drill 10mm [0.394"] deep into the piece.

Check Your Hole Saw
Take a look at your hole saw and measure the diameter of the center drill. Record this number somewhere. The diameter of this drill may force you to change several hole dimensions and potentially even the screw. In my case it was approximately 6mm as indicated by the play of the wheel on the shaft of the 5mm screws that I used.
You'd like your screw diameter ideally to be 0.5-1mm [0.020-0.039"] smaller than that diameter. The resulting play will allow for well turning wheels without the need to perform perfectly straight holes.

"Trailer Wheel"
Attach the 62mm [2.441"] or similar diameter hole saw to your drill press. Place an old but flat piece of wood on your drill press table. Lay the 20mm [0.787"] wood or the substitute wood thickness of your choice for the "Trailer Wheel" on top and secure it with clamps. Drill through the first layer of wood. Carefully remove the wood disk from the hole saw and sand it until all sharp edges are removed.
Repeat to make the second wheel.

"Tractor Frontwheel"
Use the same procedure than for the "Trailer Wheel" using the 50mm [1.969"] hole saw and a 13mm [0.512"] thick board.

"Tractor Backwheel"
Track down a cylinder that has a 100mm [3.937"] diameter. Grab the 38mm [1.496"] thick board and mark down a couple of perfect circles. Mark the centre of the circle. Clamp the board onto a table so that it hangs over by more than 100mm [3.937"]. Put a thin wood saw bit into your jigsaw and cut around that perfect circle as good as you can. It won't be as perfect any more, at least mine wasn't. Improve it by sanding it for a while. I did it by hand and it worked just fine. Not perfect, but tractors like to bounce around a little anyway. Drill a 6mm [0.236"] hole in the middle and your first back wheel is done. Adjust the hole diameter to 7mm [0.276" = ~9/32"] if you intend to use 1/4" screws.
Repeat to make the second.

"Tractor Side"
Draw two outlines of the "Tractor Side" onto a 25mm [0.984"] thick piece of wood. Clamp down the wood and cut out the shape using the jigsaw.
Sand all edges to a round and smooth finish.
Mark the locations of the three holes on each piece, first with a pencil, then if needed with the centre punch.
If you are using 5mm [0.197"] screws like I did, put a 3.5mm [0.138"] drill into the drill press. For 1/4" screws select a 4mm [0.157" = ~11/64"] diameter drill. Drill the single through hole on the large side of each piece.
Exchange the drill with a 9mm [0.354"] drill bit.
Set the depth gauge of your drill press to 12mm [0.472"] from the top of the piece.
Drill the holes into the top.
Pick a countersink or a larger drill, put it in your drill press and add a small champfer to the holes in the top.

"Tractor Main Body"
Draw the outline and hole locations of the "Tractor Main Body" onto a 38mm [1.496"] thick piece of wood. This is the thickness of a 2x4 by the way as shown here.
Clamp your wood piece onto your work area. Prior to cutting each line, ensure that the blade of your jig saw won't cut into your work surface.

The entire "Tractor Main Body" fits into a rectangle with dimensions 230mm [9.055"] x 75mm [2.953"].
Cut out the three sides of this rectangle that are orthogonal to each other, i.e. the bottom, back and top side of the body.
Next, cut the front line of your tractor. The angle of this cut is slightly smaller than 90 degrees.
Now cut along two round sections for the front wheel part as well as the passenger area. Hold your jig saw steady and move it very slowly along the line. Blow away dust as you are sawing. When you are done, pat yourself on the back, grab some sandpaper and round off all edges and cut surfaces to a smooth finish.

Mark the hole locations for the steering mechanism, the steering wheels, and the hitch. No need to mark the holes for the wheels, they are drilled later during the assembly and not now.
Use a centre punch if you are using general purpose drills to make indentations at the drill locations. This includes the location for the steering wheel.
Put an 8mm [0.315"] drill bit into your drill press.
Secure your work piece, bottom down, in your vice. Ensure it is level and well clamped.
With your drill press, drill the large through hole for the hitch that is between the two smaller holes.
Measure the core diameter of the screws you like to use for the hitch plate.
Select the appropriate drill and put it into your drill press.
Set your depth gauge to less than 9mm and drill the two pilot holes for the hitch plate.
Select an 11mm [0.433"] drill bit and put it into your drill press.
Drill the through hole for the steering mechanism.

Change your drill bit back to an 8mm [0.315"] bit.
We are now drilling the hole for the "Steering Wheel Shaft", which is maybe the most difficult part of the entire build. It may be good to practice if my suggestions work for you. It may depend on your vice, drills, drill press and experience. I appreciate suggestions to make this particular part a little easier.
Loosen the vice and turn your work piece until your drill is orthogonal to the wood surface. Beware, this is not the drill hole angle indicated by the drawing, but a much flatter angle. We are doing this to prevent the drill to walk. Drill 1-2mm into this direction.
Loosen the vice and change the angle to the one indicated for the "Steering Wheel Shaft". Set your depth gauge to 25mm [0.984"] from the top of the wood surface and drill the hole. Drill slowly and ensure that the drill is not walking.
Almost done. We are now cutting out the recessed area where the hitch is placed at the end of the tractor body.
With the help of a ruler, measure and mark the groove onto the side of the tractor body. Take your jig saw and cut the repeatedly into the part until you get the shape of the groove.
Remove all edges and burrs using sand paper.

"Tractor Top"
Draw the outline and hole locations of the "Tractor Top" onto a 9.5mm [0.374"] thick piece of wood. Clamp down the wood and cut it out using the jigsaw.
Sand all edges to a round and smooth finish.
Depending on the drill you are using mark the four drilling locations with a center punch.
Place the cut out piece on a scrap piece of wood and both onto your drill press table.
Set the depth gauge of the press to drill 6mm [0.236"] into the wood.
Drill all four holes.

"Trailer Cart"
Draw the outline and hole locations of the "Tractor Cart" onto a 30mm [1.181"] thick piece of wood. Clamp down the wood and cut out the shape using the jigsaw.
Sand all edges to a round and smooth finish.
Measure the core diameter of the screws you like to use for the hitch. Mark the locations and indent them with your centre punch.
Select a slightly smaller drill bit diameter than the core diameter of the screws and clamp it into your drill press. Set the drill press gauge to avoid drilling through the wood. Drill the holes for the "Tractor Hitch" into the bottom side of the wood.
Use the centre punch to make a deep indentation for the 12 holes on the top side of the wood.
Clamp the wood into your vice so that you can drill the 22.5 degree angled holes with your drill press. The vice is important so that you can maintain a reproducible angle for all theses holes.
Drill the first set of six holes.
Take the part out of the vice, turn it around and repeat the procedure.

The hitch parts that connect tractor and trailer are the only self made metal parts in the toy. They allow the trailer and tractor to be connected and disconnected. The hitch assembly is kind of nifty because you can't loose any of the parts and because it won't wear out over time.
Other metal parts are the hex lag screws to fasten the wheels, the small screws to fasten the hitch parts, and the washers.

"Tractor Hitch Pin"
I made the "Tractor Hitch Pin" from a leftover rod of stainless steel with 6mm [0.236"] diameter on a lathe of a friend.
Cut a piece off the rod that is (i) at least 44mm [1.732"] long, (ii) long enough to be safely clamped into the lathe, and (iii) that protrudes at least 35mm [1.378"] out of the clamp.
Over a length of 30mm [1.181"] turn down the diameter of the rod to 4.8mm [0.189"].
Cut the rod to a length of 44mm [1.732"] with a saw, and deburr the ends.

"Tractor Hitch"
I made this from a leftover piece of 1mm [0.039"] thick metal. Pretty much any little bit thicker metal should work.
Cut out a 30mm [1.181"] x 20mm [0.787"] rectangle and deburr the edges with a file.
Mark the three hole locations and indent them with the centre punch.
Clamp the piece on a wood piece and drill small pilot holes of approximately 2mm [0.079"] into the three hole locations of the plate.
Switch to a 5mm [0.197"] drill and drill the centre hole. This hole is wider than the thin part of the "Tractor Hitch Pin" and smaller than the thick part of it.
Switch to the drill bit size that fits to your countersink screws.
Drill the remaining two holes.
Switch to a countersink tool and countersink the two "outside" holes.
Deburr all hole parts that were not countersunk.

Combining "Tractor Hitch Pin" and "Tractor Hitch"
Take two approximately 5-10mm [0.197-0.394"] thick pieces of metal that have a width of around 12-15mm [0.472-0.591"].
For best results cut a 2mm [0.079"] deep V shaped groove into one side of each of the pieces.
Take the "Tractor Hitch Pin" and insert it into the "Tractor Hitch" by sticking the side with the small diameter into the centre hole from the bottom, i.e. the side that is not countersunk.
Clamp the assembly between the two V shaped sections of the metal pieces into your vice so that (i) the thin part of the "Tractor Hich Pin" is sticking out the top by 15-20mm [0.591-0.787"], (ii) the "Tractor Hitch" is below the top, and (iii) the surface of the two metal pieces is flush with the surface and flush with the top of the vice.
Bend the exposed top part of the "Tractor Hitch" until it is in an angle of approximately 120 degrees as shown in the drawing "Tractor Hitch Pin curved". You can try to put a metal tube over it and bend it using the lever, or you could use an old fashioned hammer and carefully hammer away. You have bent the piece enough when it cannot slide out of the "Tractor Hitch" without turning it a lot.

"Trailer Hitch"
The "Trailer Hitch" is an aluminium bar that is 2mm [0.079"] thick and 15mm [0.591"] wide and 98mm [3.858"] long. Given that the length is not 100mm, I think it probably was a leftover piece. However, any bar of similar thickness and length will do.
If necessary, cut your bar to length with a saw.
Deburr all edges.
Mark the hole locations shown in the drawing, then use a centre punch to indent them.
Lay the bar on a leftover wood piece and drill small pilot holes of approximately 2mm [0.079"] into the three hole locations. If you use aluminium you may get away without the pilot holes.
Select a drill bit that is approximately 1mm [0.039"] wider than the wide part of your "Tractor Hitch Pin". In my case I selected a 6.8mm [0.268"] diameter drill bit.
Drill the single hole and deburr it.
Switch the drill bit to a size appropriate for your countersink screws.
Drill the two holes on the other end of the bar.
Exchange the drill bit with a countersink tool.
Countersink both holes, then deburr the other sides.

All the parts are done, let's start putting the tractor together.

Main Body & Sides

1. Take the "Tractor Main Body" and two "Tractor Sides" and align the parts on bottom and end either mark or memorize the areas where they touch.
2. Put a thin layer of wood glue on all touching areas and let them air dry for approximately 5minutes. (Read the instructions on your glue container for best results.)
3. Set the three pieces with the bottoms on a table. Carefully align them, then clamp all three parts together with a couple of clamps.
4. Let dry for 12 hours. I like to highlight this here. Let the wood glue dry very well for best results. I did this religiously for all these parts and it has paid off.
5. Take a drill and deepen the small holes shown in the "Tractor Sides" to protrude into the "Tractor Main Body". Note that the holes that are shown in this part were for completeness only. It is easier to drill them in this step, as mentioned earlier.

Backwheels

1. Take one of the long hex lag screws, i.e. the ones that have a 5mm [0.197"] diameter and are 60-70mm [2.362-2.756"] long.
2. Thread a washer on it.
3. Then a "Tractor Backwheel".
4. Then two washers.
5. Then align the screw with the small hole in the side of "Tractor Side"
6. Take a wrench and screw it in until your screw almost compresses on the washers. Leave enough play for the wheels to turn loosely allowing only a minimum sidewards movement of the wheel.
7. Repeat with other side.

Steering Wheel

1. Take the "Tractor Steering Wheel Shaft", put some wood glue on it, and wait for a few minutes..
2. Slide it into the hole indicated by the pictures.
3. Put some wood glue on the other end of the shaft and wait for a few minutes.
4. Slide the "Tractor Steering Wheel" over it and align the end of the shaft with the end of the steering wheel.
5. Let dry for 12 hrs.

Front Wheels and Steering Mechanism

1. Take the "Tractor Steering Mechanism Axis", put some wood glue on the lower side of it.
2. Take the "Tractor Front Axis", put some wood glue in the large hole in the centre.
3. Take the "Tractor Steering Mechanism Bottom" and put some wood glue onto the bottom of it.
4. Take the "Tractor Steering Mechanism Top" and put some wood glue into the hole.
5. Thread the "Tractor Steering Mechanism Axis" through the "Tractor Steering Mechanism Bottom" into the "Tractor Front Axis".
6. Thread the top of the "Tractor Steering Mechanism Axis" through the hole in the front of the "Tractor Main Body".
7. Put the "Tractor Steering Mechanism Top" on top of the "Tractor Steering Mechanism Axis".
8. Press all parts together. Wipe off any glue that is pressed out.
9. Let dry for 12 hours.
10. Take one of the short hex lag screws, i.e. the ones that have a 5mm diameter and are 35mm long.
11. Thread a washer on it.
12. Then a "Tractor Frontwheel".
13. Then another washer.
14. Align the screw with the small hole in the side of "Tractor Front Axis".
15. Take a wrench and screw it in until your screw almost compresses on the washers. Leave enough play for the wheels to turn loosely allowing only a minimum sidewards movement of the wheel.
16. Repeat steps 10-15 for the other side.

Removable Tractor Top

1. Take the "Tractor Top" and put some wood glue into the hole.
2. Take the four "Tractor Top Supports" and put some wood glue onto their ends.
3. Wait for a minute, then insert them into the holes of the "Tractor Top".
4. Ensure they are all seated well, then turn the entire "Tractor Top" with the attached "Tractor Top Supports" around and place the assembly in the holes of the "Tractor Sides"
5. Do NOT use glue to fasten them. The "Tractor Top" + "Tractor Top Support" remain removable.
6. Let dry for 12 hrs.

Hitch

1. Thread the "Tractor Hitch Pin" of the assembled hitch consisting of "Tractor Hitch" and "Tractor Hitch Pin curved" onto the back of the tractor. The side with the larger diameter is pointing downward.
2. Take the assembly screws and fasten the "Tractor Hitch" to the "Tractor Main Body".
3. Ensure that the hitch pin can be lifted and, when looking at the back of the hitch, a gap can be created to connect the "Trailer Hitch" with the "Tractor Hitch Assembly".
4. Confirm that the "Tractor Hitch Pin" enters the lower part of the hole. This ensures a safe connection between tractor and trailer.

Great, the Tractor is done.

Now it's the trailer's turn.

Trailer Axis

1. Put a thin layer of wood glue on the top of the "Trailer Axis".
2. On the bottom side of the "Trailer Cart" start 110mm [4.331"]  from the back to lay down a thin layer of wood glue in the width of the "Trailer Axis". Note that the front side of the cart has the holes for the "Trailer Hitch" in the bottom.
3. Let the areas air dry for approximately 5minutes. (Read the instructions on your glue container for best results.)
4. Clamp the "Trailer Axis" to the "Trailer Cart". One side of the "Trailer Axis" should be 110mm [4.331"] away from the back side of the "Trailer Cart", the other side should be 103mm [4.055"] away from the front.
5. Let dry for 12 hours.

Ribs & Railing

1. Take one of the 12 "Trailer Ribs" and coat a thin layer of wood glue on one end.
2. Insert it into one of the holes of the "Trailer Cart".
3. Repeat steps 1 & 2 until all ribs are inserted.
4. Take one of the "Trailer Railings" and put some wood glue into its six holes.
5. Align the six holes with the "Trailer Ribs" of one side of the trailer and press the ribs into the holes.
6. Make sure every rib is inserted down to the bottom of the hole and has enough glue for a good connection.
7. Repeat steps 4 - 6 with the second "Trailer Railing".
8. Let dry for 12 hours.

Wheels

1. Take one of the medium long hex lag screws, i.e. the ones that have a 5mm [0.197"] diameter and are 45mm [1.772"] long.
2. Thread a washer on it.
3. Then a "Trailer Wheel".
4. Then another washer.
5. Align the screw with the small hole in the side of "Trailer Axis".
6. Take a wrench and screw it in until your screw almost compresses on the washers. Leave enough play for the wheels to turn loosely allowing only a minimum sidewards movement of the wheel.
7. Repeat with other side.

Hitch

1. Turn over the assembled part.
2. Take the "Trailer Hitch" align the mounting holes with the holes that are in the bottom of the assembled part.
3. Take your countersink screws and fasten the hitch.

Congratulations. Your trailer assembly is done.

Put your new toy on the floor.
Get your behind also down to the floor next to it.
Carefully test the functionality of the hitch by connecting and disconnecting tractor and trailer.
This has to be done on the floor. Otherwise it's no fun.

Grab a bunch of stuffed animals, big Legos or other things you have lying around that are lighter than 45 lbs dumbbells.
Test the load capacity of the trailer by putting stuff on it.
In the pictures you see the tractor still works like a charm with tons of beanie babies and even a 16 lbs dumbbell load.
Before you guys ask, I don't have 10 lbs dumbbells, neither do I own 45 lbs. ones. These are all the dumbbells we have in the house. Which essentially means I am not indestructable, but I still think this toy is.
Have fun playing but don't forget to give the tractor away as a present at one time.
And don't forget to vote for me, so that I might win a T-shirt or something to cover all those muscles that I build up with my 3lbs weights.