Tuesday, 18 May 2010

Tweaking my nozzle

The tapered reamer I ordered arrived:

This is a low quality hand reamer but was sufficiently sharp to cut a taper into the Delrin. This taper has a 3mm minimum diameter so I shortened the nozzle to minimise the run length of the final diameter, although the nozzle still has about a 1.5cm run of 3.5mm diameter.

Here the reamer has been laid alongside the nozzle with the end of the reamer at level with the end of the taper inside the nozzle.

I tested this today at 90psi and got 50 feet out of it with a 45 degree nozzle angle. This is a definite improvement to a nozzle with a constant internal diameter. However, I am still not happy with the way the stream is breaking up.

I'm going to try the following:

  • Examining the taper inside the nozzle showed that I had left a burr on the nozzle inlet and outlet orifices.These need to be removed.
  • Reduce the run length of the final 3.5mm internal diameter of the nozzle so that the end of the taper meets the end of the nozzle.
  • Taper the outside of the nozzle in case there is some air turbulence..
  • Put an internal chamfer on the outlet orifice.
All these are easy to implement and the weather is forecast to be warm this weekend....maybe I can use it in anger....?

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