I had a lot of fun with Random Orbit mk2 but I decided I wanted to move on and that I couldn’t get it to go much faster so I sold it on.
The last time I saw it the old thing was still going strong. The majority of the hull is about twenty years old by now and it’s not getting any lighter but it still gives me a wee twinge of pride when I see it. In 2008 it was driven be David Northall in the HCGB national championship. It was sold on to race again but I’ve lost touch with it now.
Keep your eyes on ebay.
One of my overriding design ideas for Version 2 was that the duct should be clear of obstructions and that the engine was to be as low as possible and out of the way. To achieve this I decided to put it down in the corner of the craft. In order to get it to fit and too make use of standard length drive belts that didn’t give me much height and so the engine frame couldn’t be the usual chunky steel affair.
Because of this and also because I fancied having a go at it I made the engine frame out of carbon fibre. As you will see, I didn’t think to take a photo (despite it being a thing of beauty), but I did take one of the mould I made it in.
It started with an innocent enough conversation along the lines of “You know Andy, most people with a TZR have a bigger duct”… “Do they? (quick look round) Oh yes.”.
Out with the angle grinder.
Random Orbit version 1 had a 750mm duct and putting 45bhp through that is a bit of a tall order and so I decided to put a bigger duct on. I’d also heard that some time earlier, someone had put a lift duct on a Cyclone and raced it in F1.
I decided I’d have a go at putting a 900mm thrust fan and a lift fan on Random Orbit.
The rules in F3 say that you can run any number of two-stroke engines in any combination up to a maximuim of 250cc but it’s tricky finding a good combination to give lift and thrust so I decided to try a shaft drive.
[note. I’m writing this in 2008 and shaft drive craft are all over the place but when I did this job in 2001ish they were quite rare]
A shaft drive means you can get the advantages of twin ducts on a single engined craft but designing one does make things interesting.
A big note… I didn’t take nearly enough photos and without them it all seems a bit dry so this section is very short.