A terrain robotic platform must be able to handle different environments and be able to go over obstacles. While looking for such a platform for an upcoming robotic project, I came across a specific class of RC models – CRAWLERS. RC Crawlers are characterized by the following:

- RC crawlers are usually slow (hence the name) but have high torque and are able to climb over obstacles
- Because they are slow their ESC has no latching brake in other words if you move in forward and then in reverse. With a traditional car ESC this will put the car in brake mode and you must move to neutral position and then again in reverse to actually go in reverse. This is not the case with crawlers, if you move the stick in reverse, there’s no brake that you have to reset by going in neutral – it goes in reverse right away. This is a good feature of ESC for a robotic transform.
- Crawler have flexible and tilting body and wheels to conform to the terrain.

To start my initial testing I picked one of these Crawlers (called MAD TORQUE by Exceed), this is a 4WD crawler with a nice modular design:

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The first problem I came across is that this crawler was not able to climb over standard stairs. If this robot will be used indoors it will need to climb over stairs. The problem – forward wheels are able to climb over first stair however the back wheels are too close and are unable to push the car further.

The solution I found is rather interesting and very easy to implement. Because of the its symmetrical design I was able to get spare parts and increase the body size in a snap:

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If you use the box as reference you’ll see that the body is now longer. This was achieved by adding an additional pair of body frames that are connected with a repurposed battery bracket part (I tried to use spare parts from the model to keep same nice color).

Interestingly the canopy fitted perfectly over this enlarged mod:

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So I am very happy with the results. It almost looks like this car was supposed to be like this. I purchased a 1/8 crawler and after this easy mod it now looks more like a 1/5 size.  The car is able to handle the stairs without a problem (see video for full demonstration).

Can’t wait to put some sensors into this and turn it into an actual robot !

P.S. yes I was tempted to add larger wheels to this, unfortunately the gears are not designed to handle them and they broke. I am fine with the small wheels anyways, they give more torque than the larger wheels with the tradeoff of slower speed.  To compensate for the slow speed I upgraded the battery from the stock 7.4V to a LiPo 3S (11.4V), the stock ESC handles it without a problem and not even getting too hot.

Hope this helps someone, happy RC modding !

Cheers,
-s