Let's Make Robots!

Building the perfect Beast (robot chassis)

2012 may be the year of the Dragon for China but it is the year of the robot chassis for me. I am trying to create a new range of robot chassis's and I'd like to know what features my robot building friends would like to see in a chassis. Obviously low cost and high quality are preferable but what else?

For example size? As far as I can see there is already a range of sizes on the market. Is there a size that's missing? I was looking at some cool wheels that were about 250mm (10 inch). Would you want a huge chassis and for what purpose?

Features? Is there a feature that you want but can never find on a chassis? More mounting holes, built in battery charger or motor driver?

Clutches? many gearboxes, even with metal gears can be damaged through accidental collisions or child abuse (the child abuses the robot).

Encoders? single pulse, quadrature, what is the minimum resolution?

Wheels? big, small, thick thin, mecanum, omni, wheels with retractable claws, what is missing from the online range?

 

To give you some idea of projects I am working on so far:

  • Low cost, miniature 6WD Wild Thumper.
  • New improved QuadBot chassis with clutches on all servos to protect the gear trains.
  • Robot hand/wrist with full range of movement (13 DOF).
  • An advanced balancing chassis with sensors.

Tell me what you want in a robot chassis.

 

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Please can you tell me where can i found it on sale preferabily in Europe due to border taxes

Robosavvy in the UK sell them.

I really like the picaxxo chassis that gareth has hacked into the propaxxo. if it is possible for the chassis design to be modified for the propeller i think you would have a serious contender to the boe bot.

The picaxxo chassis (as it appears to be called now) is truly one of the most versatile bases i have worked with.

  1. The top half has amazing space for development (plus picaxe sockets)
  2. The bottom half contains an intergrated motor/gear/H-bridge (plus picaxe sockets)

I have modified the 40pin socket to accept a Propeller chip indeed..... just by cutting some tracks and re-routing the power supply.

This base is easy to mod and adapt in many ways...... My hope is you stick with this general idea for the perfect beast.

Wishes :- bigger motors - room for bigger wheels - adjustable gear ratios - bigger H-bridge - wheel encoders - better castor system for third wheel.

This morning I woke up with an idea for the perfect multipurpose, multi-configurable robot chassis. It will incorporate many of the ideas I have read here. It should even go some way towards apeasing one reader who sent me several emails on the subject (you know who you are :)

Not sure when I will get it started as I have 3 chassis prototypes now that I am working on. First I need to find a better wheel (and castor).

Oooh. . . .

BTW :- The rubber squashy air wheel you show in the above picaxxo base is fantastic, really it has good traction on all surfaces and i get no slippage ..... so please lean into this direction .... just bear in mind that if someone wants bigger diameter wheels then the chassis wheel cutouts would need enlargement ;-)

Views on castor and slider type 3rd wheels.

The chassis in question works really well because you have arranged the drive wheels and axle very close to the center of the base chassis, which means that it turns around its self (ie "on the Spot"), most desirable when trying to escape from a tight spot, also the chassis is oval-ly roundish which is a big plus factor too.

Muse_ings :-

I am torn between three  wheel systems here:-

  1. Castors are in general great - and provided they are pushed to the ground (by weight of robot) the many bearings inside make for a light movement, however they can generate a bit of noise as they have to work dry (without oil)
    ... Maybe a smaller plastic one would better or a coated ball type out of an "olde worlde" mouse ....(encoded numnumnum)
  2. Slider :- i have used plastic skids and also polymorph dished type sliders..... anything that glides frictionless , they also work well but at the price of causing a small amount of drag..... slippery PTFE or nylon would be in right direction.
  3. Omni wheels :- you have proved ....and me too .....are tops for turning and fine control on most surfaces, the advantage is they slip....yes advantage.....when one omniwheel drives the second takes up the slack due to the many floating miniwheels, which means the are perfect for skid steering "period"

This chassis was designed a long time ago and only a few samples were made. The bottom deck which has the power supply and motor driver IC was designed purely for picaxe IC's. It also has a 3.5mm stereo socket for a picaxe programming cable with the required resistors all wired up and ready to program a picaxe processor on either deck.

The top deck PCB should only need minor modification according to Gareth to make it perfect for the propeller IC. If we do re-release the chassis then it will probably include our new hall effect quadrature encoders.

This first photo shows the built in 5V regulator and motor controller.

The second photo shows where a picaxe 08M,08M2,14M,14M2,20M,20M2 would fit. You can also see the extra long headers that join the top and bottom PCB's. This header brings power, programming RX/TX and motor control pins to the upper PCB.

The third photo shows the top deck with sockets for a Picaxe 28X1, 28X2 ,40X1 or 40X2 processor. By modifying the PCB slightly, a propeller IC would also fit up top.

 

I power mine with Lipos now and i have included a safety fuse on the motor control board.

I just love those pictures..... it just goes to show how may holes are crying out for components ..... not to forget that its easy to install line following detect IRs underneath as there are through plated holes everywhere .....YAY .... please make this a feature on the perfect Beast board.

The mod for propeller is dead easy and would only take a number of strategically placed jumper connections..