For a very long time, I had been trying to find a project that will challenge my CAD design skills. As the winter comes I come up with an idea to create a 3D printed snowmobile! Sound cool? Isn't it? I spend some time on drawing how it could look like then a looooot of time in Fusion360 and few days on printing. And here it is a really decent, quite big 3D printed snowmobile that I designed. I am proud of it, and hope you will like it :)
Step 1: Watch the Video!
Watch the video because it's cool, or at least I hope so :)
Step 2: Parts
Here are the parts that I used:
Springs: https://goo.gl/8qZqHe X4
608ZZ bearing: https://goo.gl/H3qrS8 X4
623ZZ bearing: https://goo.gl/RynV6G X2
M3, M5, m8 nuts
You can find all of the STL files above or on my Thingiverse account: https://www.thingiverse.com/thing:3348976
Most of the parts were printed on this printer: https://goo.gl/JnA9vh
For this project, I used a custom Arduino board that I made, but that's the project that I am still working on so it isn't published anywhere. You can use any Arduino board with a DC motor controller instead of it.
Step 3: Assemble Back of the Snowmobile (track)
The first thing that we have to assemble is the track mechanism, there are two tensioners some gears to power that and few other components.
Start by putting in two long parts 608zz bearings. You may need to sand down the hole for them a little bit. Best way to put bearings in place permanently is to use a vise just like I did. Then connect the pair of wheels together with small 3d printed distances (see images above). For that, I used M3x8mm screws. Also, make sure that you used proper distances for each wheel pair.
Grab M8x100mm screw and put on it small gear, add a washer and put it in bearing, add another washer, put a pair of gear wheel on the screw and again washer 3D printed part with bearing, washer and nut. Do the same with front stretcher but instead of gear wheel use stretcher wheel (bigger one).
Fix stretcher mechanism arms to the left and right part. Inside both of them, we have to put a 623ZZ bearing. Instead of a vise I used a small clamp here.
Join top stretcher wheel to the arms through bearings with M3x30mm screw.
And that's it for the track drive mechanism (back of the snowmobile). This explanation may not be easy to understand, sorry for that :) Check out my video, it's easier when you see what I am doing then when I try to explain it.
Step 4: Steering System
In order to control the snowmobile, we have to be able to turn left or right. Snowmobiles turn thanks to skids on the front. I struggled a lot with a design of steering system for this project, I wanted to make a suspension for both skids but also control them with a servo motor. Finally, I designed a simple, flexible solution that can be easily controlled with a servo motor and use simple springs as a suspension. Here is how to assemble it:
Fix servo motor to the main body (the biggest 3D printed part) with 2 screws.
Now we can connect damper support, skid support, and steering joint together, for that I used M3x20mm screws.
With M3x16mm fix skids to the skid support part, you don't need to use a nut there, but if you want you can use a longer screw with a nut.
Here is an interesting part. Because damper support has to be able to move I decided to use a different type of connection here. Instead of a screw, I used a piece of filament that I can put in a hole and press on both sides with a hot flat screwdriver to create "rivet". It works really well, it's cheap and very uniform while designing you can use any length you want. We will connect pieces of track exactly the same way.
Connect a steering joint connector to steering joints with two M3 screws. The steering system is almost ready the last thing to do is to fix servo arm to the servo.
Step 5: Suspension
You may say that this is an overkill for this project and that we don't need a suspension. And you are right but I wanted to have a suspension, to make it more professional and again challenge myself with designing. It was totally worth it! It works great and looks just as good. Just two springs and suddenly it looks less toyish :)
Step 6: Motor and Gear
Before putting a track in place we have to fix the motor, later it would be harder. Use M3 screws and secure them with nuts on the other side. Remember to put on gear and also secure it with a screw.
* On the images you see different gears then what you can find in STL files. After some tests, it turned out that this gear ratio is too big for this motor and I had to design new gears, now it works fine. Just wanted to clarify that so that you are not confused.
Step 7: Track
Put two springs between right, left part and stretcher arms. We will use the same method of connecting stuff together with a filament instead of screw. Grab an old flat screwdriver, heat it up, put a piece of filament in the hole of the track and melt both ends of the filament. We need to connect 24 pieces of track that way. To close the truck loop put it on the back of the snowmobile and do the create a rivet. Make sure that truck can move freely.
Step 8: Join!
Now we can join main body to the track mechanism with M5x12mm screws. I also secured this screws with nuts on the other end.
Step 9: Electronics
Electronics would be very simple but because I used a DC motor it's not that simple. Servo is connected straight to the RC receiver but another channel of the receiver is connected to my custom PCB that has a built-in H bridge, there is also atmega328 with Arduino bootloader. You can do the same with the normal Arduino board and a dc motor controller. I am still developing this board and it's not ready yet, I will make a video about it once it will be finished. As a battery I used 3S Li-Po. If you would change this motor to a BLDC motor that is controlled with ESC it would be way simpler to control and you wouldn't even need an Arduino for that. Code that I wrote can be found below. I am not really god with that RC stuff so I am not sure if this explanation of connecting that is proper. It's also hard to do any schematic in fritzing for that so if you have any questions, just ask in the comments.
Step 10: Paint Front Part (optional)
This step is optional. Because of the printing orientation of the front part, there was a lot of support material that is hard to remove. The finish of this part was really poor I decided to sand it down, fill and paint it. It took some time but definitely looks much better now!
Step 11: Conclusion
Check out my video to see how this snowmobile works. It's really cool to drive it and that was a fun but also challenging project for me. I am really happy that it works so good. As for now I don't have any stronger motor so I have to find one and update this project to make it faster, a lot faster :)
I hope you enjoyed this instructable. Let me know in the comments what you think or if you have any questions! Thanks for reading :)
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