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R/C 1:7.5-scale Ariel Atom

I'm designing a scale model of the Atom and making it remote-controlled.

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This is an ongoing project of mine that I wanted to share. I'm making a smallish scale remote-controlled model of the Ariel Atom sports car, with a 4-wheel independent pushrod suspension, brushless electric drivetrain in the rear, and a shiftable on-the-fly 2-speed transmission.

I started this in college and on a college budget, so I've been working with as few physical parts as possible to keep costs low for now. There also wasn't a huge R/C community to pull from there, so if some of this turns out to be crap, I'd greatly appreciate it if you let me know.

I would say I'm two years of sporadic work into this, between classes, other projects, and various life obligations like employment, bills, and sleeping. Currently I'm using a copy of SolidWorks 2014 as that's all I could get my hands on, but I've been making parts in 2011 through 2013 and updating them as I've been editing them.

I hope to start physically prototyping things soon. Just how soon remains to be seen.

Frame

Ultimately, I have been looking at using some sort of metal (steel or aluminum) tube in a combination of 5/16", 1/4", and 3/16" sizes for the frame of this beast. The frame's tubes in the model have been sized accordingly, albeit solid for model simplicity. CFRP was mentioned and that's an interesting proposal, I would probably wrap a 3D printed frame due to its complexity rather than make all the tubes separately and bond them together. I have also given some thought to making forms for the handful of complicated parts and heat-bending plastic tubes to the right size. I don't know why I didn't think of that earlier, since it's super cheap and shaping tools are super cheap. More research is pending.

When mounting points for hardware and panels are more in order, I'm planning on 3D printing it as a sanity check step. Shapeways currently wants more than $400 for the entire frame as one plastic piece as it's big enough to be priced by build volume and density (LxWxH is about 40x19x15 cm or 15.8x7.3x5.7 inches, 1.84% density). I'm looking into getting a printer and running it off in two to four pieces, and bonding/fastening them together for the prototyping phase.

Cosmetics

The panels play a key part in the look of the Atom, along with the exposed exoskeleton. I've been designing parts based on reference images to the best of my ability, and I'm constantly tweaking them as I get better ideas and improve my CAD skills.

I plan on 3D printing these parts, with sanding and painting where appropriate. Attachment points are still largely up in the air until I settle on their designs and the mechanics underneath.

Wheels

The wheels have been designed to accept a standard 12mm hex hub and fit into 52x26mm on-road RC tires. This was actually a critical factor in vehicle scale, as I wanted to keep the wheel diameter to scale with the rest of the car. Initial material plans are FDM ABS/PLA to check tire fit with the hope to CNC them out of aluminum. Any (hard) testing will likely be done with off-the-shelf RC wheels unless those 3D printed ones turn out to be really balanced and durable.

Drivetrain

I'm currently designing a two-speed transmission for the rear wheels, to allow for a more manageable gear ratio for demonstration purposes and one for winding it up outside with enough space. The current design is a two-stage reduction, the first being through a MXL-sized belt drive to the transmission, and the second through one of the two gears.

I'm also designing the rear differential, as places like Traxxas and Tamiya don't post dimensional drawings of the parts they make, only what they fit in. Which is fair, I suppose, but frustrating. Many of these also have the cups for the universal joints located very far inboard.

Suspension

I've designed the majority of the front suspension parts using McMaster-Carr 3D part models for things like screws, nuts, and bearings. Currently the camber is adjustable via a thumb nut and threaded ball joint that are held by the upper A-arm.

I also have a pending redesign of the lower A-arms and hubs at the front to allow for adjustable caster.

All four corners have independent pushrod-style suspension, just like the real deal. Hopefully I can find some fitting off-the-shelf parts (coilover shocks, pushrods, ball joints, etc), but I've not had a ton of luck so far. I have mock-ups to gauge location and size in the meantime. There's also currently no anti-roll bar in the front or back, but I may add them later.

Electronics

I have been using a 4074 (40mm diameter can x 74mm can length) brushless inrunner for reference for the drive motor, which just fits inside the rear frame. There's space above the motor for the controller, as well as between the front of the motor and the seatbacks, depending on its size. If it's above, the scoop could act as an air duct for the heatsink, with a small muffin fan built in. If it's behind the seats, air from under the bodywork could cool things, but there would need to be some impact/dust...

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  • At long last, updates!

    kevinj07/10/2015 at 17:55 1 comment

    It's been awfully stale in here, partly because I didn't have a CAD environment set up for a while, and partly because life's been busy. But I’ve seen all the follows (thanks everyone!), and it's been a good push to post an update on things.

    I've been tinkering with a lot of the finer points of the model, so that I can finally sort out some critical details, like the steering and how parts are actually going to connect together.

    Here's how it looks now:

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Kellz wrote 01/12/2019 at 05:47 point

Kevin, did you ever finish this project? 

  Are you sure? yes | no

Adriano wrote 12/28/2016 at 12:29 point

How do I get this
project? I'm trying to make an ariel atom, my email kalungafw@hotmail.com

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jay.mistry1110 wrote 01/06/2016 at 09:57 point

I want to Built an actual replica of Ariel Atom but don't have any dimension.

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zakqwy wrote 09/30/2014 at 20:54 point
What are you planning to use for frame materials? CFRP? Welded steel tubing, like the actual car? What drove the decision to include a transmission?

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kevinj wrote 10/01/2014 at 03:06 point
I haven't gotten the chance to put up more detail yet, but ultimately, yes, I was thinking of doing welded steel tubing. For the prototyping phase I'm thinking of doing halves or thirds of the frame out of ABS or PLA. The frame in plastic, in one piece, on Shapeways was over $400. I hadn't thought of CFRP before, though.

I decided to do a transmission for two reasons:
I want this thing to move at a manageable pace, and be able to kick things up a notch.
I also wasn't ever able to find dimensional drawings of diffs and the like from places like Traxxas, so I figured if I was making a diff and case, I might as well go for a transmission, too.

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zakqwy wrote 10/02/2014 at 23:32 point
Good deal. Shapeways isn't cheap but they make great models.

In my experience, 316 stainless is chosen for its corrosion resistance and cleanability. 4340 might be a better choice--easier to weld, much stronger, less brittle. You could powder coat the frame to prevent rust.

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kevinj wrote 10/05/2014 at 21:51 point
Thanks! 4340 sounds solid. Full disclosure, though, I don't have any tube bending or welding experience yet, and I know no amount of reading will compensate for experience. I'd be up for a membership and classes at a TechShop but not when the nearest one is five hours away in DC. Plus my location and workspace availability are up in the air in the nearish future, along with some long distance moving, so I'm not super on board with getting a welder if I won't have anywhere to use it for a while.

I think CFRP or fiberglass might be a good middle ground for more strength than plastic and better accessibility to tools and training. I'll have to look into it more, especially for this complex a structure. That might be the point at which I get the frame printed off from Shapeways and go about reinforcing it.

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