How To Make Rudder Pedals

By Bill Spencer

I was going to name this document how to make rudder pedals, but other people have already published their ideas so I am not the first to publish, but I might be the first to build pedals this way, if I am not and you have already published then I apologise and bow down before your cleverness. I was driven to the act of building my own pedals purely on financial grounds, no money! or a lack of it to spare. I have used lack of money as a primary rule thoughout the building and improvement process KEEP IT CHEAP!, and use the KISS principle, (Keep It Simple Stupid). The stupid bit is for my benefit. These pedals are simple to build and even easier to maintain, but a right sod to explain how to build, that's why the description is a bit long winded. A light dusting with talcum powder every now and then and there you are maintenance carried out, no string, no rubber bands, all good mechanical connections. (If you haven't got any talcum powder pinch the wife's/girlfriend she's bound to have some) you just might want to warn your friends about the smell before you sit down for a session, they might think you have gone funny.

These pedals work in a to and fro action rather like the real thing, but unlike other designs it doesn't use string or rubber bands. Not that it can't have them if you want, but I chose to use other items that most people have lying about the house, (Keep It Cheap). What I will attempt to do, is explain how I built my prototype set (picture above); prototype set also explains all the extra holes, (previous modifications that failed). I will give you the sizes I used, but if you want to alter any of the sizes, I will also give you the method for calculating your own figures where required; well I will try. The material I used to build them was 9/m/m ply but it was good quality ply, furniture grade I think someone called it. Anyway I obtained it from a local handicapped workshop who were dismantling ex RAF furniture to use the wood for other things, so really, it's your choice of what you use.

Building The Rudder Pedals

The rudder pedals can be broken down into four components: 1. The Baseboard. 2. The Pedals themselves. 3. The Crossbar. 4. The Electrical bits. A 15 pin D type plug and socket, twin core wire and a potentiometer in the range 47K to 180K ohm.

The Baseboard

The baseboard is just, that a board onto which everthing else fits. 330 m/m wide, 355 m/m long. Onto this are attached four strips 355 m/m long, 12 m/m wide. These four strips will act as the runners which the pedals will slide on and form the channels in which the pedal guides will slide. These four strips need to be attached to the baseboard so they are all parallel to each other. Dimension A represents the width of the pedals themselves. You will need to drill a hole the same size as the bolt you are using for the pivot bolt in the centre of the board.

Baseboard plan view

Baseboard end view

The Pedals

The pedals consist of three items: the pedal base, the pedal footrest and the pedal footrest support. The wording is long winded but it should help you to understand the drawings. Before I forget, another word about the pedals, there are two of them. Unless your name is Jake the Peg then you might need three. The pedal base is 155 m/m long, 100 m/m wide and slides on top of the runners on the baseboard. Attached to the underside of this base are two guides which will fit inside the channels on the baseboard and stop the pedal falling off the edge. The pedal footrest 170 m/m long, 100 m/m wide is what you rest your foot on, or make it longer to fit your foot. The pedal footrest support 80 m/m long 12 m/m wide. This supports the foot rest up from the pedal base at one end as per drawing and is located on the pedal center line. You could use two supports but one works fine, or adjust length to suit most comfy position for your foot.

Pedal end view

Pedal side view

The Pot

The pot is the bit that converts our mechanical movement into electrical signals that the computer can understand. All we are concerned with is how to achieve this, as rotary potentiometers work by turning and thereby increasing or decreasing resistance we need to make the pot turn when we move our pedals. Turning can be achieved by a wheel or a lever arm, as my first attempt used a wheel, I won't bother with that as it was too inconsistant, instead I will describe how to do it with a lever arm which has proved to be more consistant. For a lever arm I can recommend no better item than a LEGO Technic brick, these are manufactured to close tolerances, close for toys anyway, and most people with kids will probably have some. If not you can always go and buy a small box and it will probably have all the parts you need. An alternative is, some toy shops have LEGO spares racks and you could get all your bits like that. OK, advertisement feature over, I used a 1x6 long brick, in LEGO Technic these also have 5 five holes down the side. Drill one of the end holes on the side out to 6 m/m and you should find this is a tight push fit onto your pot shaft. A black Technic connector will form the peg at the other end of the lever that the crossbar will act upon.

The drawing opposite shows how to calculate how much movement we need to incorporate in the crossbar fork to allow the crossbar to operate the pot. L and R are the extremes of travel that the pot moves, C represents the position of the pot when the pedals are in neutral. Dimension X is the length of the lever from the center of the pot to the center of the hole at the other end of the arm that you use to connect to the crossbar.

If you draw a line from L to R and then measure from this line to C this figure will represent the movement we need on the crossbar. The movement in the crossbar is effected by making the fork hole slotted, it will make sense (I hope) when you read about the crossbar. I had to put this bit here as you need this information to make your crossbar. One point to mention here is do not exceed the 45 degree left or right movement for the pot when you are moving it this way otherwise you will come across a phenomenon known as geometric lock. This lock is so strong that they use it to hold undercarriages down on real aircraft, Cessnas to 747s. If you want to make your pedals a different size, width or travel, from the ones I have, then you will have to recalculate the pot travel exercise above.

To mount the pot on the baseboard a mounting bracket such as the one shown here will need to made. Nothing too grand, a bit of metal with holes for the pot and for screws slotted if you want a bit of lee way in positioning.

The Crossbar

This is the bit that links the two pedals together, and rotates around the pivot bolt. Length 330 m/m, 80 m/m wide, 9 m/m thick. You could actually make your crossbar only 25 m/m wide and then use it to move your pot by string, but not if you omit the following step. Where you attach your pedals to the crossbar make the holes slotted, outwards away from the center pivot point. The holes will need to be the same size as the diameter of the screw you are using and the slot should be smooth. This will now allow the pedals to move back and fore and the crossbar to rotate around the pivot bolt. To calculate how long to make the slot make a drawing something like this.

C represents the central pivot point of the crossbar and the lower x is the attachment point on the pedal. The four parallel lines running up the picture are the strips on the baseboard. The upper x is where the attachment will be when the pedal is fully one way. The difference between C and the lower x and C and the upper x is the length of the slot.

On the drawing above the pedal attachment would be on the inside edge of the pedal whereas the prototype it is on the outside edge. Inside and outside edges are relative terms, the attachment point should be directly above the pedals guides. This will mean that you can screw through the pedal base into the pedal guide. If you attach on the inside the crossbar will not need to be as long if attached on the outside.

If you change the distance the pedals are apart then it will change the amount of travel that you have available to you. This change will also affect the distance the crossbar moves the pot. The drawing below will show you how to find the new distance to set the pot in front of the crossbar.

This drawing basically the same as the previous except that the line L and N now represent the crossbar center line. With the pedals in neutral the pedal attachment will be at the lower x while the crossbar fork centre line will be at N. When the pedal is fully forward the pedal attachment point is at the upper x and the crossbar fork centre line will be at L.

To find out where to fit your pot, take a measurement between L and R (see The Pot above) and divide by two. Move up line N until the figure you have just obtained is touching lines N and L respectively, i.e. if your half figure is 10 then 0 is on line N and 10 will be touching line L. This measurement must be kept parallel to line C line p above or it will affect your pot/pedal movement later. Line y is the distance that will result from this exercise and is the distance that the lever arm peg will be. The pot will of course be at the other end of the arm. On the next page is a drawing of what the crossbar should/might/ought look like.

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