3D Printed Lights for Lexan RC Bodies

Why Print Headlights: Depth > Decals!

Because decals make a model look like a kids toy, but real lights are real serious! ;-)

When it comes to scale RC trucks there are two kinds of bodies.

• Injection-molded ABS "hard bodies" can have a lot of detail, but are generally expensive and also far more delicate, they are less suitable to taking abuse on the trail.
• Vacuum-formed lexan bodies on the other hand are less detailed (due to the process they cannot have recesses or overhangs) but can take a ton of abuse without breaking, and are very light-weight, making them suitable for competition.

One way to add a lot of realism to a lexan body is to add the small recessed pieces, such as headlights and tail lights. In this Instructable I will show how I designed and 3D printed such lights for the Redcat Gen7, arguably the best bang-for-your-buck RC scale crawler. The process can easily be adapted to any other lexan body

Get the Files

If you would just like to print and install the Redcat Gen7 headlamps, then you can find the files used in this project here:

• Tail Lights for Redcat Gen 7
• Head Lights for Redcat Gen 7

Here is a link to the whole collection of parts I have created for the Gen 7 so far:

• Redcat Gen 7 3D Printable Parts

Materials

Of course you can use whatever materials you like, but these are my recommendations

• Tail light lenses: Rigid.ink Transparent Red PETG
• Head light lenses: Rigid.ink Natural PETG (natural = transparent)
• Light Buckets: Rigid.ink silver ABS
• Grille and Support piece: Anything really, but I use clear PETG sprayed black since it is tough and easy to print.

IF YOU CUT YOUR RC BODY OR HUMAN BODY IN HALF IT AIN'T MY FAULT, THIS IS ALL AT YOUR OWN RISK, SO CHOOSE CAUTION (DUH!)

Of course you can skip this section if you just want to print and install the headlights that I designed on you Redcat Gen7, but if you would like to design headlights for a different model then here are some pointers.

Design Tool

I used Autodesk's Fusion 360.

Consider your material

The rigid.ink Transparent Red PETG has a wonderful deep red colour, which becomes almost opaque when more than 1mm thick, so the lenses had to be thin. When Designing thin parts I always use even multiples of the nozzle size, so I chose to make the lenses 0.8mm thick.

For the buckets I chose to use silver ABS, so as to avoid having to paint it. These could even have been acetone smoothed, but in the end I decided it wasn't needed.

Print Orientation

When printing lenses the print orientation has a number of consequences, so design them such that they can be printed in the desired orientation, even if that means trimming after printing.

• Any blemishes from support material they will be very obvious when the lens is lit from behind.
• The print lines can be used to simulate extra details.
  • I chose to print the headlights flat on the bed, so that they would have concentric rings.
  • I chose to print the tail lights vertically so that they would have horizontal lines, which I think look quite realistic.

Tolerances

It is always important to consider tolerances for parts that need to fit together. You can see in the section views of the Fusion360 screenshots that I allowed a 0.15mm tolerance between the edges of all of the lenses and the buckets they need to fit into.

Hide the Cuts

It is next to impossible to make perfectly clean cuts in a lexan body, so I designed all of the lights with a small flange which would overlap the cut edges, giving about 0.8mm of leeway. These flanges are a nuisance to print, since they require supports, but they are worth it for the final look.

Fitment and Attachment

You will only get one shot at cutting your RC's body, so you need to make sure that it will be right and will last.

I designed a backing plate that supports the headlights (and the custom grille) at the same time as providing a template for the hole that needed to be cut. The buckets actually glue into this plate rather than the body, meaning that if they need to be replaced it can be destroyed, rather than the body.

For the tail lights I printed a cutting template, which can be used to mark the holes to be cut, ensuring that they are the same on both sides of the body.

Orientation

• Print the tail lights vertically, as shown, using a brim for stability if necessary
• Print the head lights flat on the bed, to provide a shiny clean surface on one side
• Print the tail light cutting template vertically
• Print the grille with the mesh flat on the bed. Only use support around the outer flanges, not under the mesh

Use the templates

• The backing plate for the headlights and grille also forms the template for the cuts, so it should be glued in place first (I used hot glue, but be cautious, it can take paint off)
• Use the tail light template and a permanent marker to draw a cut line

Cutting

See warning on first page, I take no responsibility if you get blood on your RC (seriously though, you can slip easily, be careful), on the other hand, the Gen 7 is waterproof, so you should be ok.

• Start by drilling small holes at the corners of all of your cut lines, these will help you start the cuts but will also (usually) help you stop cutting, since it is very easy to slice too far when cutting an RC body
• Cut using a sharp box cutter or small strong curved scissors
• Cut slowly
• Cut too small rather than too big, you can easily go back and shave off more

Glue

I used superglue in very small amounts, to glue all of the parts in place, beware that it can damage the paint on the Gen 7, so use it sparingly.

Superglue is also useful for gluing your fingers back together when you inevitably cut them in this process.

The details of powering LEDs are perhaps beyond the scope of this Instructable, you can easily find other detailed instructions here on Instructables or on the web. Here are some points to consider though.

BEC or Battery?

You must choose if you want to power the LEDs off the 5V from the ESC/BEC, or directly from the battery (voltage varies depending on chemistry, NiMH vs. LiPo, and number of cells).

I chose to use the spare channel on the Redcat ESC to power my LEDs and it is working perfectly.

Advantages of using 5V from BEC/ESC

• Output is always 5V - If you power from the battery you will need different resitors depending on the voltage, I prefer to be able to swap between 2S and 3S batteries as I see fit.
• Easy to plug in if you have a spare channel (I just modified a servo cable), didn't need to splice into the battery cable

Disadvantages of using 5V from BEC/ESC

• Additional load on the BEC regulator (but not much, <100mA in my case)
• You waste a channel on the RX (unless you use a servo y-splitter cable)

Choosing LEDs

My light buckets are sized for 5mm LEDs, two for each tail light and one for each head light

Head lights

I chose high bright white LEDs, running at about 20mA, since these have a voltage drop over 3V I had to run them in parallel, each with their own resistor.

Tail lights

The tail lights do not need to be very bright, so I used some nifty LEDs that have an internal resistor, designed to provide ~16mA at 5V, which made the wiring super simple. Obviously all four are then in parallel.

Installing

Once you have tested that your LEDs work, go ahead and super glue them in place.

I then sprayed the back of them with black paint, to prevent the light leaking out in the wrong direction.