What would one look like?
A pentagram or pentagon shaped ultimate wheel. 
Maybe the spoke pattern could be a pentagram or the wheel itself could be a pentagon. 
Re: Penultimate wheel
Maybe like this idea by David Stone? It is an ultimate wheel and a unicycle merged into one.
Klaas Bil
Re: Penultimate wheel
Well by definition, it would be the one that came just before the ultimate wheel. So if we go with the theory that the UW was first invented by someone that tried riding their uni wheelset when they had it detached from its frame, then a penultimate wheel would look like a standard unicycle.
Re: Re: Penultimate wheel
Or possibly a penny farthing.
Nah, it’s the next to last wheel in a series, so it’s the 12 foot uni:
Actually, from that perspective it would be the right front tire of the wheelchair.
My ultimate wheel has this design painted on it.
Does that make it near-penultimate?
I was thinking about the idea that some guy came up with a while ago. I’m too lazy to look for the thread, but the idea was that it would be an ultimate wheel with a saddle “floating” on the seat. It would need to be a large diameter wheel because of the lack of frame. The saddle would need a series of rollers or other mechanism to allow the saddle to stay above the wheel.
Someone had a pic of a similar device in a circus.
Yes. When the idea was raised, I was the one who suggested the term “penultimate wheel” for it.
It would be an ultimate wheel without pedals.
You could only wheel-walk it, standing up.
Like a 2 dimentional rolling globe.
I’m gonna have to try this.
You’d need a very fat tire, and big too.
You could probably do it with a car or truck tire.
in which case it get’s to be very close to log-rolling
but on dry land
Stacked Ultimate Wheel i.e. One wheel on top of the other with pedals…Not too sure if that’ll work