How do you make a ultra-compact repeating signal for dispensers?

My friends and I are working on a TF2 map in Minecraft, essentially making different weapons and abilities for classes.

One of the classes we were working on was the Engie, and in Minecraft, there's really no way to make a very compact repeating mechanism.

We already have the dispenser thing set up (dispenser + splash potion of health), but for a turret, we're looking for the most compact way to make it "repeatedly" shoot out arrows.

Probably the most compact design I know is like this:

W-W-B
W-R-T

W = Redstone Wire B = Any solid block R = Repeater T = Redstone Torch

Taken from minecraftwiki.

use a piston repeater

it works on the principle that a solid block transmits power but air doesn't moving the block disrupts/establishes the signal

This one is very compact and can shoot 20 arrows per second.

L:Lever
R:Redstone
BR:redstone on block
RT:redstone torch
D:dispenser
RP:repeater

      RT-BR-RT
  L-R-R-R-R-R-R-RP-D
      RT-BR-RT