![]() The box is fitted with a flange on either side: one for positive pressure, the other for negative. The box contains the vacuum motors, and must be airtight to ensure that there is no air leakage. The second major system is the box and its associated attachments. All of these sensors and the motor controller are managed by an Arduino Leonardo connected to a personal computer. In addition to the motor control electronics, our design includes a barometric pressure sensor and thermistor (to convert mass flow to volumetric flow), a differential pressure transducer to measure test pressure, and a mass air flow sensor to measure the actual flow rate. The other motors provided a baseline airflow, and were simply plugged into the wall. To reduce the current that the motor controller would need to handle, we only controlled four of the seven total motors. Therefore, we were able to use pulse width modulation (PWM) to control the motor speed when they are run on DC power. Since vacuum motors are universal motors, they are able to run on either AC or DC. ![]() Building a motor controller severely increases the complexity of the project, but gives more possibilities for convenient automated testing, and more importantly, consistency. This is a valid option, but we instead opted to build a motor controller. Generally, most DIY flow benches modify flow rate by using a manual valving system. Unfortunately, our particular flow bench is unable to reach the industry standard test pressure of 28 in H2O, but it can still test different valve lifts at a constant test pressure, which, along with a bit of math will allow comparison to published values. In order to test different valve lifts at the same test pressure, and to ensure that the test pressure matches literature values, it is essential to be able to vary the speed of the motors. These two components can be worked on independently in whichever order one chooses, but we would recommend working on the electronics first, as once the motors are mounted in the box (and the box is sealed), it is more difficult to perform tests on that subsystem. There are two major components to this project: the electronics and the mechanical construction. However, the instructions presented could easily be scaled up to increase the flow bench’s output. ![]() Our flow bench is only capable of testing small cylinder heads/test pieces. Note that all of the vacuum motors used in construction are recycled, so the total cost may vary depending on what one is able to obtain second hand. This flow bench will use blower motors scavenged from household vacuum cleaners to generate the airflow necessary for testing. More information on what a flow bench is and how it works can be found here: In this Instructable, we will be explaining how one could build a flow bench at home for around $300. ![]()
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