Just an update on the latest voyages of the Vital Byte.
VB has had a few mechanical and software problems over the last two weekends on the Cygnets Model boat Club venue at Mote Park, Maidstone.
VB had a run of 18 minutes to use up gas in a partly used cylinder and achieved 588RPM max with a gas consumption of 4.3g/min and then, with a fresh cylinder, a 53 minute run at 593RPM max and 3.7g/min consumption. Unfortunately the "A" pump motor blew its fuse and I had to swop over to "B" pump between the two runs.
Inspecting the pump later, I found that the ram was tight because the pump body had become slightly misaligned. With the help of a piece of SteamboatPhil's kindly supplied shim, the body was realigned and was tested OK.
The software recording the engine revolutions (and average RPM) was not working and was found to be due to part of the calculation taking place during the speed probe pulse. The calculation was moved in the software to occur after the pulse and the data is now being recorded properly.
Previously, at Kearsney Abbey, I had been monitoring the ambient temperature of the bow compartment where the gas cylinder is located with a max/min thermometer. Well, as reported elsewhere on this forum, the thermometer melted and it contents disappeared! Therefore, I have made a ventilation hole and an aluminium shield directing the heat away from the cylinder area.
The ongoing problems of putting the engine into reverse were traced to the drive-end "B" cylinder valve timing and also the "A" piston bottoming out, causing stiffness at bottom dead centre.
Having sorted all of the above problems, VB had another outing to Mote Park last Sunday - and what a disaster it was!
I spent the best part of an hour chatting to people about the boat and its computer before I attempted to put her on the water. The pump jammed again and the computer overheated due to the sun shining through its clear plastic cover (it was acting like a greenhouse) whilst it was on the shore. No voyage on that outing.
This time it was found that the pump was fine but the commutator end of its electric motor had become loose and resulted in loss of output. The gas control chip had failed on the steam temperature input of all things. A new motor and gear box was fitted and tested and a new PIC chip fitted and downloaded with the control program.
A fan was fitted to the computer housing for use on very hot days (you can tell this developed in the winter!) and the pump control software was modified to automatically switch to the standby feed pump within 6 seconds of the main pump failing and also a gas valve shut instruction was added if both pumps failed.
Today VB managed a decent run at last. She moved effortlessly between forward and reverse, maximum bow compartment temp was 28degC instead of 50plus and the pumps worked ok. Max RPM was 580 and average was 334. The engine was ticking over at about 50kPa (8psi).
On the water at the same time was the Cygnets 50th anniversary build of HMS Kent, type 23 destroyer. She was having a shake-down cruise before her epic voyage between Tonbridge and Allington Locks, via Maidstone, on the River Medway next Saturday 11th July ( visit http://www.cygnetsmbc.com/
for details of the day). The 12 foot model just cut through the water like a knife through butter, a magnificent achievement.
Vital Byte will be exhibited at the Guildford Steam Rally on the 18th/19th July, I hope to see some Mayhemers there.
Below - the latest VB photo.