Absolutely No Paradox by Lester Del Rey - If time-travel is possible, then why haven't we been visited by people from the future? But Pete LeFranc found the answer to that.
The old men's section of the Arts and Science Club was always the best ordered. The robots somehow managed to avoid clanking there; the greensward beyond the veranda was always just right, and the drinks were the best for six counties. Old Ned Brussels touched his glass to his lips appreciatively, sighed in contentment, and waited for some of the other oldsters to break the silence.
Finally, Lem Hardy took the plunge. "He did it," he announced, referring to a conversation of weeks before. Then, at their puzzled looks, he amplified. "My grandson, damn it! He's got a time machine—it works. Sent a cat four days up, and it came through unharmed."
The glass fell from Old Ned's hand, bouncing on the floor, and spilling good liquor. A robot came forward silently to clean it up, but Ned didn't look at it. "Four days doesn't mean a thing. Lem—is that kid planning on trying it out?"
"He's going to try it next week."
"Then for the Lord's sake, stop him! Look, does it work like this?" His fingers slipped over the pencil smoothly, as they had always done when he worked, drafting robot bodies in the old days. A rude schematic seemed to grow almost instantly on the paper.
Lem took it, then stiffened suddenly. "Who told you?"
