I've purchased and I've operated expensive machinery and I've seen what happens when people don't take appropriate safety precautions. He could have built an e

I've purchased and I've operated expensive machinery and I've seen what happens when people don't take appropriate safety precautions. He could have built an enclosure and put this on a table similar to what is used in lab experiments. But please tell me what this has to do with whether I have personally tried to build, in particular, engines?