Wednesday, 19 August 2015


As you know, in the middle of last week I ordered the metal that I intend to use as the basis for the tube bundle thrust chamber.

The 316L tube and hollow bar arrived today. The hollow bar came from Schoeller Bleckmann in Oldbury and the tube from Steel Express in Wolverhampton. I also ordered a piece of 316L plate. This didn't arrive today so I will have to chase it up tomorrow.

The hollow bar is 212mm OD x 170mm ID. Here is a photograph of it sitting in it's protective sack. It was too heavy to lift out...

This has to go in the lathe somehow. My current thinking is to drill and tap the piece and then bolt it directly to the faceplate.

Here is the 316L tube, it is 10mm OD x 2mm wall:-

These tubes will need to be cut into near enough identical lengths. I have decided to make a cutting jig based around an angle grinder to do this.

The jig will be composed of a section of aluminium angle welded to an aluminium plate. This angle will act as a sort of V block to hold the tube being cut. Sections of  drilled and tapped aluminium flat bar will be welded on to the angle to form a clamping feature. The angle grinder will then be mounted on a pivoted bracket, enabling repeatable cut off to be achieved.

Here is the base plate of the jig:-

This picture shows the angle with a piece of flat bar showing how this will be mounted to form a clamp:-

I milled the flat bar sections square - not strictly necessary but it made me feel better:-

Here is a final shot of the angle and plate trialled up with a scrap piece of angle to show the position of the angle grinder bracket:-

I will also have to make a tube bending jig, so there will be plenty of practical updates over the next few weeks. Once the jigs are made, I can trial the actual tube fabrication process.

Keep watching.

Wednesday, 12 August 2015

Step Off

Today has seen the completion of the stepper control box. The electronics and power supply are now mounted and wired in to the switches on the front panel.

The power supply was fitted using 6BA bolts. As mentioned in the last post, the mains lead enters the enclosure via a strain relief gland.

Here is a photograph showing the internal set up of the electronics and power supply:-

Here is another photograph showing a side view of the electronics installation:-

And finally, a shot of the completed system in it's entirety:-

The control box was connected to the stepper on the rotary table. A full functional test was successfully carried out.

With this tool now complete, attention can again be turned to the design and development of the tube bundle thrust chamber concept. It also means the end of step related punning post titles. I can almost hear your sighs of relief. 

Tuesday, 11 August 2015

Three Steps to Heaven...

Greetings, dear reader. I am back in Blighty again and ready to resume rocket engine related activities.

To that end, I have done some more work on the rotary table control system. I'm putting together the control box that will house the power supply, switches and electronics.

Here is a photograph of the front panel, showing the LCD display, menu scroll through paddle switches and menu select button:-

The rectangular holes for the LCD display and the paddle switches were created on the milling machine. The paddle switches snap into the holes and are held in position by integral spring clips. The LCD is bolted in place using the protruding 6BA bolts that hold the PCB stack together. Here is a photograph showing the arrangement of the electronics and switches on the rear of the panel:-

The power supply will be fitted in the space next to the switches. The mains lead will enter the enclosure through a strain relief gland. A socket will be fitted for the stepper motor drive pulses.

I'm looking forward to getting the control box finished. The automated rotary table will then be ready for use. Just in time, as I am now going to order the material to begin the construction of the tube bundle thrust chamber.

Look out for more updates over the next few days.