Back when I was in school I worked a couple of summers working in a scrap ward. Here was the method we used which Never failed.
Keep in mind this is cars/ trucks I am talking about, but I know the principal is exactly the same.
Loosen off the nut holding the steering wheel on, but don't remove it. Only back it off until it is flush will the end of the steering column. Then get two large ball-pein hammers, then sit in the driver's seat, then slide forward so you can both your knees/ lower thighs to the back side of the steering wheel (like at the 9 o'clock and the 3 o'clock position) and apply a strong pressure with both your knees/ thighs. Then rest one of the ball-pein hammers on the end of the steering shaft w/ nut and with your one hand, then pound that hammer's ball end with the other hammer. Really stubborn ones will take two three good solid wacks; no steering wheel will refuse this persuasion!
