I would like to install shorter crank arms for a child (stoker on a tandem). I have not yet taken the crank arms off, but I found the pictures below in another thread and my crank arms and chainring look identical. It looks as if the drive side crank arm is permanently affixed to the chain ring, so that I will not be able to replace the crank arm without also replacing the chainring. Am I correct, or is there a way to separate the crank arm from the chain ring and reuse the chainring with the shorter crank arm? I found shorter crank arms at a unicycle shop, as pictured below, but I am not sure if they will work. Thanks.