This project is a look into my development process. It is an exploration into a new class of radio controlled “Rock Crawlers”.

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Quadrocker, a controllable figure add-on for the RC crawler.

Concept:

The idea is that controlling a truck is fun, but if you could somehow lean as if you were on a lightweight atv then it would be even more fun! Compared with R/C Helicopters and Airplanes, R/C Crawling uses fewer channels and requires you to think about less at once. That was one of the reasons I like it more than racing rc cars. Now, don’t take offense, I know once you start channel mixing with digs and all that it gets more complicated. I like the simplicity and intuitiveness of no dig, but being able to force the weight of the vehicle to change in some way.

Sure it has a higher center of gravity which makes it more difficult. I know, but screw it, it’s really fun.

Motor on axle crawlers have made ridiculous things climbable. Nonetheless, lots of people are into scale crawlers which includes adding unnecessary weight onto the trucks center. As with the other car types -sportsman, super, mini, etc- This driving would be in a different class that is yet to be defined. I am calling this class Quadrocker. I imagine that it will look a lot less ‘scale’, if you could call it that just as competition crawlers have lost much of their truck-like appearance. For v1 I have tried to make it look relatively real so people get the concept. I could see making it very untruck-like or very scale depending on personal preference.

Here is a compilation of crawling videos. You can get the idea but it obviously needs a lot of work. The head should be able to pitch at a greater angle, a wider stance, more weight in the wheels, etc.

Quadrocker Micro Crawling R/C Controllable ATV – YouTube
If anyone besides me wants to pursue this folly, here are a couple of the hypothetical rules.

Competition Rules:

An agreed on amount of weight must be mounted to the chassis midpoint. This mass can be controlled in any way.

The mass center must be in the center + or – 1cm

The mass must have the same length width and height + or – 1cm (no long things)

The mass must be an agreed on height from the center of the wheels

Here is an example image:

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But I digress, There is no competition when there is only one of these out there.

Even before people were RC crawling I wanted to have an atv with a rollcage that I could crawl with . It would be 4 Wheeling and atv combined. Or, Trials Biking with 4 wheels and a motor. The rig could be tweaked with your body weight. The issue is opposite of the micro rc version. The rig would weigh too much vs your body weight.

I’ts possible I will try to build a 1:1 scale in the future. A superlight 4×4. Also with a roll cage because I will flip it. That would require a lot of funding. I was thinking kickstarter but that would require a lot of work.

One of the inspirations for this concept was the genre of videogame that use lean forward/lean back game mechanic. Games like excite bike (NES), Trials HD (Xbox Arcade), Exite Truck (Wii), Toy Stunt Bike (iphone), MX Mayhem (iphone) to name a few.

These are screen grabs from Trials HD:

centered:
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forward:
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back:
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I figured I could use two servos to control the body and have a lead filled head at the top.

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At first I used parts from my other RC build Joywrex’s Creeper Build (First RC ever). I realized that if the servos were bigger than micro sized then their weight would require me to add a lot more weight to the head and so i decided to avoid that by building the first prototype with the smallest car possible. A Mini RC size would probably be better in the long run, the micro itself is too light.

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Enter the Losi Micro Crawler. This specimen was sold on RCCrawler to me by SNCrawler

Now I know that ATV’s don’t usually have straight axles for the front and rear suspension. Maybe they should. Body weight counts, just as much as much as I’d like. The grizzly is close; power steering, 4 wheel drive.

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Taking the time to learn about what electronics I would need was bringing me down so I went to toys’r’us and found just what I needed to start thinking about sizing.

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After removing all of the extraneous parts I was left with this.

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Naked Micro. About to get a lot heavier…

Shout out to hotglue. I love it. It is great for mocking things up quickly. Also, having a large (electric) and small (butane) heatgun makes it easy to adjust or remove bits.

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The Micro has a reveiver esc combo board which was not good for me because I am adding two channels to control the rider.

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Iteration 1 of the torso yoke. It’s good have cad skills. I recommend solidworks. It’s really intuitive. At least compared to others. I order the prints online. It’s pretty cheap considering I don’t kneed a machine shop or even a garage. I have used lots of services. Shapeway’s is a good one. They can print or otherwise form a large selections of materials. Check it Shapeways – Customize and create 3D printed products. Welcome to the Future of Stuff.

It’s worth getting their sample pack of materials if your interested. It’s $30 though.

These two parts were $15

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Head on a spike

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Servo housing v1

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Torso yoke v2 and

Servo housing v2

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Torso yoke v3

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I made a platform for the servos to sit on using shapelock. I heat it up with my trusty heat gun then sculpt it with my burning fingers. It’s like shapeable hotglue to make hard parts out of.

You can get a sample from their website. SHAPELOCK FREE Sample Offer It’s $5 for shipping

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These videos are the first movements while the servo chassis is mounted on the actual micro. “It’s Alive!”

Quadrocker Micro- torso yoke v3 leaf spring test – YouTube

Quadrocker Micro – torso yoke v3 shocks test – YouTube

Quadrocker Micro – torso yoke v3 shocks test2 – YouTube

Quadrocker Micro – Final Weight Wiggle Test.MOV – YouTube

I got some 2S lipo packs to give it more power than the NiMh it came with. Here is a video to understand the difference.

Losi Micro NiMH vs. Lipo batteries – YouTube

Obligatory articulation pictures (not that their any good)

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Heavy legs. They should be vacuformed in the future.

Does anyone know where I can get lighter legs?

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The smallest receiver I could find. OrangeRX. It works with DSM2. Therefore I am getting a Spektrum 5-channel. (DX5e)

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I am using the stock motor and transmission.

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Servo housing v3

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I am unhappy with the shocks the Losi came with and with the head weight you can kinda slouch off of obstacles. I decided that a leaf spring style chassis would spring back more readily. It would feel a little more like an atv. I ordered the DP Torsion Chassis to try out. It is not designed for much heavier midsection so its as good as it can be. I would like to machine out my own design someday.

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Possible receiver placement

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These tires are worn out.

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This project has given me control issues. The only one that is not specifically for this project is the flysky gt3b.

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Weight testing

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It’s looking good so far.

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First iteration of a hollow jacket in place of a body. I suck at sewing.

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And then I filled his head full of lead.

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Once it was filled i covered the lead shot with hot glue to seal it in the helmet.
Torso yoke v4

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Second attempt at a jacket.

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I got some Miniqlo Miclaw tires and weighted them with bb’s. No foam. The are a bit big. Maybe I should switch to the trail trekker tires or lengthen the links. (kinda hard to lengthen the links with the shockless chassis though)

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I painted the wheel weights. The paint scratches easily because I didn’t prime the surface in any way. It’s going to look pretty cool once they get all scratched up IMO. I love this picture. Reminds me of a ring wraith from Lord of the Rings.

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The quadrocker component is surprisingly durable. I am using Tower Power MG90S servos and they haven’t broken. This video is a fall onto carpet from 42”. The only damage was one of the ball end links popped off and the hot glue bond connecting the servo chassis to the driveline broke.

Quadrocker Micro – surpisingly durable – YouTube

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After many Rx placements I finally settled on mounted to the server chassis. I updated the cad to make it fit just right.

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Again, hot glue is awesome. I added some material to the rear body part and drilled a hole for the body pins.

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I picked up some aluminium spindles, just because…

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Added the on off switch to the fender

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Torso yoke v5

I switched to ball and socket style rod end rather than tie rod style. They are lighter and can pop off in a bad crash. The flat side of the yoke is for the screw that mounts it onto the driveline (universal joint)

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Servo chassis v4

Here you can see the front where the body pin screws into and the receiver covers

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I removed the little gas cap and put the body pin through that hole.

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To make the body as light as possible I made a tube from fabric and used thin wire to create the skeleton.

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The legs for the guy are made out of solid rubber so they were really heavy. I scanned one of the legs, and then printed it shelled. So the inside is hollow. It went from 18g each to 7g.

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The time consuming part is painting them. I’ll get to that later.

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Getting ready for V2…

First, I printed a new and improved servo housing.
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Installed the servos. The new one is on the right. I wanted to have both on hand for comparison.
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I am using some stock tf2 driveshafts but I think I will need the junfac style balljoint/pin shafts to move the body around more fluidly.
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Next up, making it work

Positioning the new torso part. Now instead of the servos being on the chassis, they are part of the weight that moves around.
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Here is the old servo cover used to create a platform for the quadrocker figure to sit on. It’s pretty sturdy considering the 3d printed sides are, well, 3d printed. If I create my own chassis these parts would be build in.

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The figure’s shaft is connected to the servo cover. It grabs onto the aluminum with a star washer.

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I can adjust from left to right because of the slot.

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Assembled

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It’s been too long since I worked on this thing. I had some time so I decided to replace the tires with some boggers. They are much smaller and help with the CG.

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I used some 0.040″ wire to make a leaf spring for the rear.

One version:
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Another version:
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Now I need to do the front. So far this is way better than before.
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Here’s another timelapse. I find that the timelapse is a good reference for in the future when I can’t remember what type of glue or something I used in the past.

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This is an ongoing project… To be continued.