I am planning on making a pair of rudder pedals from scratch. I don't know whether they should be hinged, or slide forwards and backwards.
On real aircraft, how do they work? Does it vary from plane to plane?
I've never seen "sliding" rudder pedals in a light GA plane - though there may be such designs in transport aircraft, especially fly-by-wire planes.
If you're looking for simplicity for a homebuilt aircraft or simulator I'd go with hinged pedals pivoting at the floor similar to what you'll find on a Piper Cub (which can be made by welding tubes together into an
I shape), or any number of similar floor-mounted designs:
(As shown in the first picture, toe brakes can be easily retrofitted onto such a design, and as shown in the second you can mount square pedals on them if you want to, though the round bar has some advantages.)
Sliding pedals are very unusual - I do not know of a single aircraft which uses them. It is also mechanically more complex and fragile - you would need to keep all those sliding lines clean, at a section of the aircraft where dirt is most common.
But there are three different ways to hinge the pedals. The most common one is at the bottom, but they could also be mounted on a crossbar. By using two crossbars, you get a parallelogram wich helps to keep the pedals at the same angle.
This picture shows the "cockpit" of the schooling glider SG-38, simply because it doesn't hide anything. As you can see, the pedals sit at the ends of the parallelogram, and you could add another hinge at their base easily for activating brakes (which the SG-38 did not have). Now you would have two degrees of freedom which make controlling two separate functions easy.
The third way is to hinge the pedals from the top. This again helps to add a second degree of freedom, especially when the top hinged mechanism uses two parallel rods to again ensure a constant angle of the pedals, independent of their position relative to the hinge point.