First steaming of my Springbok

Yesterday I took my unfinished Springbok to the club and steamed it for the first time, with a temporary water feed to an injector from my riding truck. This is my first engine, but along the way I finished about 3/5 ths of a Blowfly for a young friend, and there were many other distractions. See my profile for a bit more of the story. The engine ran very well indeed and far exceeded my most optimistic expectations. The injector worked reliably and it was very easy to drive. Although only running light and slow, to run in, it used amazingly little fuel and water, greatly helped, no doubt, by 4 radiant superheaters. It needed no blower, and the pressure remained stable. I am absolutely delighted with it. Thanks to Julian for calculating the front end dimensions I used, and to Don Aston for helping me to modify the valve gear. I wanted to get rid of the 26 thou lead, and lengthen the expansion link to get about 75% cut off in full gear. James Sanders made this video:

**LINK**

She looks lovely. It must be supremely satisfying to take the first ride after all those countless hours of work. Well done!

Simon,

I've read your post, watched the video and looked at your public profile. Well done. What a wonderful journey you've been on, with I hope great satisfaction and enjoyment.

Steve

I think you start thinking about the first drive as soon as you have a rolling chassis. I've seen several first drives where the engine has limped back to loco with problems: an eccentric/return crank slipped; a pin fell out; there was a significant steam leak; the valve timing was atrocious etc.. Mine was supremely satisfying because it went so well. The only problem was that one of the lubricators grub screw had slipped (Steam Fittings commercial one) so it wasn't pumping, but I had piped up such that both lubricators went to both cylinders for just such an eventuality.

The journey has sometimes been satisfying and enjoyable, and sometimes frustration and exhausting. Plenty to go but all downhill from here. The tender chassis is made so it will be cab and tender tank now.

Hi Simon,

You have done extremely well there and I very much enjoyed watching the youtube clip.

There have been many Springboks built to Martin Evans' 5"g design, which was a very early design of his circa 1960, and you deserve considerable praise for having noticed fundamental errors in the design/drawings and resolving them.

I remember one particular Springbok built by the late John deBank of the IWMES on it's first few steamings on the track and it seized up solid.

On the other hand I remember driving Alan Killick's Springbok at Beech Hurst (SMLS) and you could drive it on the reverser with an open regulator - a rare treat. Alan's example was not built to the drawings I gathered!

With a Jos Koopmans draughting and Don Ashton input into the valve gear you have something quite special there plus your excellent workmanship!

Cheers,

Julian

Thanks Julian. I wish I knew about the blow down holes in the frames being in the wrong place! I had to make ugly circular extensions to the rectangular holes to accommodate the valves. Clearly Martin Evans did not make a Springbok. In fact, I am informed with some authority that the first Springbok made was actually made here, in Australia but I can't remember the builders name. I would love confirmation of this, if anyone knows. Another problem I did not know about is that the bogie wheels hit the front cylinder covers on a modest curves. This happened on my test run on our largest radius track, and apart from trying stiffer side control springs, I don't know what to do about it.

Some of the changes I was forced to make I was worried would lower performance. The firebox is narrower, because of our 4-9/16 back to back wheel standard and also because of the 4 mm frames I used. I dropped the number of firetubes to from 18 to 16 because 18 did not really fit, with our AMBSC requirement for 3 mm ligaments in the tubeplates (proved unnecessary by Alan Wallace in a scholarly article in AME). Also due to the availability of 1-3/4 clip-lock rings, I increased cylinder bore to this from 1-11/16. The valves also have clip-lock rings. These excellent rings were used in truck transmissions, but no longer, so they are now almost unobtainable.

The valve gear was designed using the Wallace simulator with Don's help. Then the rods and links were cut out to these numbers (rods laser cut, expansion links wire cut. I hacked out one connecting rod just to feel honest!). The valves were then timed by putting them where the simulator said they should be when the piston was in a particular position, e.g., in full gear with the valve measured to be moving the specified 0.685" with a dial indicator, the back port was set to open to exhaust when the cylinder had traveled 92.3% of its travel (measured with a depth gauge). The valves are not set to equal leads, as that did not give the best events with the changed dimensions.