This instructable will show you how to build a wide open throttle switch that activates 2 separate switches. This unit is mainly focused on race cars or seriously fast street vehicles. It is made to mount on to a carburetor stud of a Holley Dominator style Carb. I use it for nitrous activation and methanol injection activation. The reason for 2 switches is so you can wire the system to activate your alcohol injection when your nitrous is not armed. It also allows for a very robust redundant wiring of your nitrous system just in case 1 of the switches happens to fail, which can and does happen with the violent vibrations of drag car engines.
The custom pieces of this switch are 3d printed and include a base and the arm. The switches can be purchased from race car part retailers or various retailers such as McMaster Carr. The shouldered screw was purchased at a local hardware store.
1 x 3d Printed base, I recommend ABS plastic for heat resistance and 100% infill for strength.
1 x 3d Printed arm, also recommend ABS with 100% infill.
1 x 10-24 shoulder screw with 1.5" shoulder length, .247" diameter shoulder for .003 clearance in a .250 hole.
2 x button switchs, I purchased from Tim McAmis race cars part # NEW-A-20GQ-B7K
Step 1: Threading the Base and Assembly.
This is the only fab work to be done on this project, you will need a 10-24 tap and simply tap the hole where the shoulder screw installs. Then take your 2 switches and install them into the 2 large diameter holes and secure with included nuts. Then simply set the arm into place and tighten the shoulder screw, make sure you use a super glue as thread locker so it does not come loose.
Step 2: Watch This Video to See What It Looks Like, and a Tutorial of Features.
This video shows how I mounted the switch, also pay attention to the arm position which should work fine for all dominator carb's but feel free to adjust to your liking.