Need help with my project

I need a robot with the following specs to complete my project:
1. Strongly prefer width of less than 3.5", the smaller the better
2. Able to push 2X4 wood block of about 4" in length. The wood block will be in a tunnel, so there is no concern about side way movement. 3. Simple linear movement only, and only need to push the wood block repetitively about 3.5" each time, but speed and interval must be programmable 4. Prefer ready made to complete my project sooner
I am thinking there must be programmable toy cars/bulldozers that can do the job, but I can't find it so far.
Please help. Thanks.
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snipped-for-privacy@yahoo.com wrote:

Try LEGO Mindstorms. You might be able to borrow a friend's, or buy one used on eBay. You ought to be able to pick one up for about $100, perhaps less, depending on condition. You can program it to do what you outline. Width, when motors and wheels are attached, is about 3.5", and you can construct it in about 20 minutes.
-- Gordon
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