Project Baja Racer

Hey guys,

This is project Baja Racer, the W2D-IV (Wrench To Drive 4). It's a 3D printed crawler/bouncer that can use clone SCX10 or WLToys 12428 drive train parts. The vast majority of the car you print yourself. The 3D files are available on Thingiverse or Cults 3D.

On to the Baja Racer...

Body

The Shell is VW Beetle inspired but diverges quite drastically in places if you look closely. I went with a cage because bodies are expensive and I wanted to design a car that is cheap to build and run but still looks cool. I'm hoping that I can skin the cage with body panels and it will hold up well enough to get a passing grade from the bashers, but we shall see. So far, the TPU skin panels I made are okay but not as nice looking as I'd hoped. They are durable and mounting with hot glue doesn't seem to be a problem, which means that if it ever is due to breakage, the ability to fix easily will be nice.

Chassis

The chassis is a beefy 3D printed ladder frame that is crawler compatible, meaning you can most likely adapt it to suit most 1/10 scale crawler drive trains, but it is more suited to a racer type car because it doesn't facilitate easy inboard servo mounting. Front or rear mounted motor placement is also likely to be a bit of a challenge unless you design your own cage. However, if you want to take it to the next level, the modular suspension mount design allows you to create your own custom front and rear sections relatively easily.

I designed the shell to mount with hook and loop (Velcro) by sitting on the rock sliders which are attached to the frame rails.

Seemed like a good idea, works okay, not as well as I'd hoped
I designed a couple of cross braces and alternate front/rear cage sections to facilitate a more conventional post mount setup

The post mount setup will work with body shells relatively easily

you may need to use 3D Builder in Windows 10 (or some alternative) to stretch/tweak the mounts

The post setup will be quite durable if you print with TPU (Solutech flexible) filament. With PLA I suspect it will be okay but not great in terms of durability, with better durability if you use light axles/wheels and a little less durability with heavy axles/wheels. I've broken two or three PLA body mounts in hard crashes, but those crashes also broke injection molded plastic parts so I don't consider them failures, just not as good as one might hope.

The shock mount geometry is not quite as good/tune-able as I hoped, but the modular shock mounts make changes easy so I'm not too worried about it

the width at the shock mounts is a little wider than normal for a crawler but it works fine

The shorty battery tray that mounts between the frame rails works well
The long battery tray that mounts above the transmission along the length of the chassis (more to the rear), is a pain because you have to take more apart to mod the gears etc. The battery does slide in nicely from the rear.
Articulation is a little lacking but I think it's because the links I bought are binding against the transmission/suspension mount (I thought binding slightly, but I think binding for reals).

I tweaked my 12428 Honcho conversion suspension and it works great and there is no reason this beast should work any less well, so I think I just need to tune it a bit

I now appreciate that the center mounted transmission makes electronics/battery placement a bit more of an adventure with no cab floor boards to default to. Mostly it's only a problem if you want a setup that requires wires running the length of the chassis for one reason or another and even then, only if you want nice easy access without taking the cage off. Running like any crawler with the body more or less locked down, it's not any different in terms of hassle.

Drive Train

The two drive train options are SCX10 clone based and WLToys 12428 based.

You can easily order SCX10 (or compatible) axles, links, drive shafts and center gearbox to get yourself up and running
For the DIY crowd, you can put WLToys 12428 gears into 3D printed axles and center transmission for the ultimate budget approach

There's no servo mount for my axle housing project as of this writing so you'll have to come up with something if that's the route you go

Going the SCX10 route costs about $150 and going the WLToys route costs about $100.

My advice is simple: If you have the budget, go with the best parts you can rationalize. If you're on a budget, the 12428 approach works but you will break the odd part and need to upgrade along the way. For most people who love the hobby, that's a big part of the fun. Bodies are pretty pricey these days and that's where this project really starts to save you money. If you dig my cage or want to design and build your own, I think this project is not a bad starting point as far as chassis' go.

You can pretty much buy a printer and the various parts that you need and build this car for about the cost of a Traxxas TRX4 (full meal deal, not the Sport version). If DIY doesn't rev you up, it it makes more sense to buy the crawler you want, but building your own is pretty fun. Obviously, you can always spend more in this hobby, but the way I see it, worst case, TRX-4 money is your entry point. If you have access to a printer, things obviously get cheaper and DIY starts to make more sense from a dollars perspective.

Basic Printing Tips

Lay those tube shaped bits down flat so that you get the runs of plastic in the direction that you need strength. Make sure the heat is a little high so that layer adhesion is as good as you can possibly get it (I run at 215 for this stuff and 205-210 for pure appearance). Use the most bendy plastic that you've found because RC parts take heavy hits and brittle parts are the worst.

Stuff You'll Need

- Drill and small bits but you can get by with a rotary tool (trying to get all the holes to print perfectly never seems to work out)
- Allen wrenches (M2-M3 sizes)
- Phillips and flat blade screw drivers
- Cutters
- Pliers

- Hot glue gun
- RC car wheel wrench (that corny little one everybody has)
- Soldering iron (if any parts you buy need soldering or you need to take apart locktited parts)
- Screws (M2-M3)
- Grease

Stuff You'll Like to Have

- Allen wrench drivers/bits
- Rotary tool (Dremel) with grinding/sanding/cutting wheels because cleanup of parts takes waayyy longer without it
- Electric screw driver