Let's Make Robots!

Tri-wheel stair climber

It seems to me that for a robot to be really useful in the home or workplace then it must be able to handle stairs. With this in mind I want to design a stair climbing robot chassis. This robot is my first experiment with Tri-wheels.

The chassis is just 4x Wild Thumper 75:1 motors driven by a Wild Thumper controller in a clear acrylic base. As this is only an experimental platform for the wheels I am controlling it with a TV remote and an IR receiver.

This first set of Tri-wheels is made using a new 80mm diameter wheel that has been produced by DAGU. The gears are steel to handle the high torque required when climbing.

The clear triangular frame is made from 3mm thick milled polycarbonate. I used CNC milled polycarbonate instead of laser cut acrylic because it is tougher. The acrylic is fine for the chassis but too brittle for the wheels. All shafts are ball raced to reduce friction.

You can see here that the chassis consist of 4 ribs, a top plate and a bottom plate. They are all held together by 56 small steel angle brackets and 112 small M2x5 screws that give the chassis good strength and rigidity. In hind sight I could have used less but this is just a prototype.

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If you make the chassis longer, and able to fold at the middle, you would be able to climb much higher stair without make the tri-wheel larger by it self.

But it would require some work on the software side to make it auto adaptable to different stair heights.

The longer the wheel base the worst the robot handles corners such as stairwell landings. Ultimately I want to use only two Tri-wheels and a balancing system so that the base is smaller and can corner better.

The current base is only testing the wheel dimensions, torque, etc.

Cool idea. I agree-stair climbing is important for a homebot. This solution is probably more dependable than the spider security models. I can't wait to see the results.

The Tri-wheels are not a new idea. For now I am just testing the grip of the tires and various dimensions. This wheel will only be able to climb stairs of about 150mm (6 inches) in height. This limitation is due mainly to the size of the gears I am using.

If all goes well then in later models I will use larger gears (and maybe wheels) that can handle stairs up to 200mm (8 inches) high.

Most newer stairs here in the US are 7-11 seven inches rise 11 inches tread, so this might be tough if you want to sell it here you will have to have gen 2, [on the other hand Oddbot I so want to make a Mars Rover kind of thing or out door bot out of these], older stairs tend to have higher rises and shorter treads might affect the bot lenght, CTC will know more than me about stairs, I do heat and A/C but built my own home a few years ago so thus the stair thing, my basement has 10' ceelings


This prototype is using gears I had available so I think 150mm (6inch) will be it's limit. From my research, the U.K. had the heighest legal riser height of 220mm (about 8.5inch).

If all goes well and I develop this into a product then I will have to use bigger, lighter gears or a belt drive. The steel gears are too heavy. I will also need to experiment with different tires to see what gives the best grip on smooth stairs.

Damnation Alley, you may want to consider adding a pivot to the middle of the chassis to give it the ability to turn, or, keep the mass low so it can skid steer.

I read that book. It does seem to have the same form as the vehicle on the cover. Damnation Alley, holy.

Ultimately I am working on a balancing robot using a Tri-wheel. This would not need the center pivot.

i needed this and i still do... i dunno what it is called so when i look for it i had to describe it and i always end up being shown a random set of gears