Prototype Ant Concept 2. An experimental 4 wheel drive differential steered robot chassis to antweight specifications.

PAC-2 chassis and drive

The PAC-2 idea comes from one of those times when you look at a product and think "I wonder...". Toys 'R' Us sell a range of cheap battery powered cars and buggies. These include uncontrolled and wire controlled machines in 2wd and 4wd configurations. Of most interest to an ant builder is a "Battery powered buggy kit", a 4wd uncontrolled 3v buggy in kit form which retails for an amazing £2 in the UK!

As it stands the kit is of little use to a roboteer. True, it has 4wd with shaft transfer, but it has no steering and no differential. It does, however, provide a source of cheap lightweight rubber tyred wheels - this was the feature which originally attracted me to it. The "what if.." moment came when I considered cutting two of the kits in half and glueing them together back to front to create a 4wd differentially steered chassis.

The result can be seen in the photo above. PAC-2 is a 100mm square invertable robot chassis with a very creditable weight of 93 grammes. For a competition robot there is plenty of surplus removable plastic to reduce this figure. The motors and gearboxes are hidden under the plastic housing and the drive transfer shafts can be seen going down each side.

So if you get all this for 4 quid and a bit of work, where's the catch? Speed. This is a kid's toy. Finesse and manouverability is not in the design specification. So with basic on-off control from 4.8v it moves off like a rocket and would be a sod to control on an antweight arena. The idea is worth persevering with though, and the next step is to run the motors from proportional speed controllers to see if that tames the beast.

Still, 4wd for 4 quid? Had to be worth a second look!