Introduction: Monster Fire Truck From Salvaged Grave Digger Power Wheel
My daughter wanted a Fire Truck for Christmas. The problem was that I couldn't find one that looked decent and wasn't hundreds and hundreds of dollars. Luckily the universe heard my daughter's wishes and sent me an OfferUp post for a FREE Grave Digger power wheel!! How else could that of happened? 😉
I jumped in my car and went to pick it up. I didn't care if it worked or not, I was going to convert it to a Fire Truck anyway. Turns out, it didn't work and it was in pieces. Most people would walk away from this but I figure they saved me a step by taking it apart.
I got it home and did some testing. I found out that there was a bad switch and the sound board was bad. Still I couldn't believe my luck, I was so happy to have it. Most importantly, the motors worked. I got started on the build right away. There was only 3 weeks before Christmas so I had to work fast.
The video is the full build, please let me know what you think. I love to see people's comments and build a little community of makers. This Instructables has more details than the video if you are looking for that. Enjoy!
Supplies
Well, the most important part is the power wheel. Luckily the Grave Digger was already a truck so not a far stretch to make it a Fire Truck. But I'm not sure the power wheel is part of the supplies. In any case, start with a power wheel of some sort, new, old, or salvaged like mine.
The two major parts I bought were the horn and the flashy lights.
Parts List:
- Paint. To freshen up the body and other parts, a nice coat of fresh paint will go a long way to making your vision complete.
- Horn. What is a fire truck without a horn?
- Lights. I think this is a basic requirement for all emergency toy vehicles.
- White LEDs. I added these to the head lights for visual effect.
- 10W resistor. The horn was super loud, so I used this to make is tolerable for a 4 year old to use.
- Stickers. I bought vinyl stickers online. They were perfect for this build. Alternative is you can print and cut them out yourself.
- Reflective tape. Some cool accents for the vehicle.
Step 1: Yes Disassemble !
Too bad Jonny 5, we have to take this all apart. Luckily I received mine in pieces but most likely that is not the norm. Take it all apart so you can see what you are working with and for cleaning. The main reason is for painting. This step might not be necessary if you are not painting all the parts.
Be sure to put all your screws in a safe container. This might require you buy an expensive pint of ice cream to reuse as a container if you don't have one. Sorry to make you do this.
Step 2: Optimus Primer
Next step is to clean and prime all of the parts you plan to paint. This step helps the paint stick to the plastic and adds some durability. It will also help show defects in the plastic if you want to go back and sand them out. Primer gives you a good idea of what the finished part might look like. If the primer looks bad, so will the painted part.
If your plastic is badly faded, you can take a heat gun and lightly melt the plastic back to normal. This isn't a perfect technique but works for most things that are sun faded and can bring back some color. Plus it is way faster than buffing or polishing it.
Step 3: Mask Up and Spray Down
Mask up your part that is. You should also wear a mask too btw. If you are doing a base coat first then going back with another accent color, make the base coat the lighter color. Example: If you have a color palette of white and red, I would do the base coat with white with little to no masking. Then come back and paint the darker red color with complete masking. Dark colors over top of light colors reduces the bleeding color effect.
A tip to spray painting is to do a very light coat at first. I know it is very tempting to want to cover the entire part first pass but that usually leads to paint dripping or cracking. It is ok to not have 100% coverage on the first pass. You will get there with multiple passes and the paint will look better. I usually wait 15-30 minutes between very light coats because they dry pretty quick. This is a good time to practice patients.
Step 4: Loud and Proud
Now we need a horn. Every emergency vehicle needs a horn or siren. Except for maybe the coast guard helicopter. Maybe...hmmmm. Anyway we need to install one for this toy fire truck. I chose a very inexpensive horn on Amazon and it worked perfect for this application. I even created my own sounds using the Arduino for the steering wheel horn button.
It turns out any waveform you send this horn, it will play. There are a bunch of tutorials for playing sounds on Piezo speakers so I just used one of these to play twinkle twinkle little star. Then attached the signal line to the horn amplifier and it worked. I then attached the horn button to an input on the Arduino. Here are the instructions I used: https://www.arduino.cc/en/Tutorial/BuiltInExamples/toneMelody
One issue I had was I set the Arduino signal pin to be an output. When the output is low, it has enough impedance to pull the OEM signals low so the horn wouldn't play anything but the twinkle twinkle little star. To fix this, the signal pin on the Arduino needs to switch from an output to an input when not in use. Then the horn can do what it wants and when the Arduino wants to play, it takes over. Which is really nice because the horn on the steering wheel will override any sounds already playing. 😁
Step 5: Flashy Lights
These flashy lights are very bright and perfect for the transition to emergency vehicle. It is a little disturbing that the advertisement for these implicitly suggests that they should go on your car. Not sure you should install flashing blue and red lights on your car.
The biggest problem was that these lights are only operated with a remote control and we wanted them to be integrated into our power wheel dashboard. Luckily they are being controlled by a one-way 433Mhz bit receiver. Basically any bits you send on one side will show up on the other. This is common with a lot of home automation devices. All I had to do was remove this receiver from the board and decode the messages. This part sounds crazy but was made really easy with this guide.
Excellent Writeup for decoding 433Mhz
After I had the messages I just replayed them from the Arduino when it received a button press on the dashboard. Very cool and surprisingly didn't take much time to do. But that was thanks to the guide in the link above.
Step 6: Undisassemble
Time to find a place to mount everything and put it all back together. I don't know why it takes so much more time to assemble than to disassemble. Same with most puzzles I guess. Have fun with this step, not sure what else I should say about it.
Step 7: Final Touches
I added some reflective tape and some pre-cut vinyl stickers. This little detail added so much more than just the paint alone. It kind of ties the story together. Please don't skip the little details like this. If this were the 80/20 rule, then this step is the 80.
If you do apply tape with a patterns, be sure the pattern is symmetrical on the vehicle. Example, if the tape has arrows, be sure they are pointing the same direction on both sides of the vehicle.
Step 8: Watch Build Video
As always, thank you very much for getting this far. Please watch the video. I try to add humor to it so it is more tolerable. I'd love to get your feedback if you have any. Always trying to improve.
YouTube Link below.
Have a great build!
Second Prize in the
Fix It Speed Challenge
