Let me see if I got your question right: you want to activate a relay for periods shorter than one second even though the relay itself is activated by a 1 second long pulse from the receiver?
You could do this by the receiver triggering a one shot multivibrator, the pulse output of which is adjusted to the duration you want. You need a retriggerable one shot, I think the 4528 chip is a dual retriggerable one shot, so it resets itself for the next trigger input once the one shot pulse had expired.
You still need to wait at least one second before the next pulse from the receiver can repeat the cycle.
Of course, the chip output cannot drive a relay direct, you need at least a transistor driver (and a reversed diode across the relay coil for EMF suppression).
There is a limit for how short a relay can reliably stay on, someting to do with the mechanical inertia of the design. For real short on times you'd need an electronic switch but by then you run into the inertia problems of the motor itself.
Good luck with that one,
Klaus