Help with home robot

Hello friends

I hope you are very well, I take the liberty of writing to request your support.

I tell them that I’m starting a home project, my son likes fighting robots and we want to make one; I just need help with ideas to create a hammer (although it does not have much force), that the hammer can strike a little. I do not need code, only that they support me with materials, what types of motors etc. (we think using a meccano you have).

First of all, Thanks

(attached sample image)