Knock Knock who's there....... Engineering Report No 12

I believe every one is aware that since February 2003 when the new engine was first connected to the prop shaft there has been a knock. Not just a comforting reassuring sort of knock, which is quite common with marine power units but a knock that tells you there is 'somat up' After much trial and error and seeking advice the knock was traced to the stern tube bushes. President was docked last November and the stern tube and the prop shaft was removed and delivered to a workshop in Tunstall. New bushes were made (3" X 6" approx) and a new tail shaft. A new connecting pulley was fabricated which uses an expanding insert to join the 2 shafts together. Also a new thrust bearing was fitted. When the new bushes were fitted to the tube seals were fitted to prevent the loss of grease and the ingress of water and silt into the sleeves. This will reduce the need to constantly pump grease into the stern tube.

Success, but...

Once the stern tube was fitted President was returned to the museum and the new transmission assembly installed and tested YEEESsssss No Knock, but a rattle. Close investigation showed that it was coming from the hardy spicer joints and the splines. The speed of the engine and the resistance of the prop were creating an imbalance and this was causing the prop shaft to rattle.

The possible answer was the flywheel. I have always considered that the flywheel I fitted last year was too small. Where do you get a flywheel? There was space for a 26" by about 4" wide( 66 x 10 cm ) flywheel. David Powell saw an advert for marine engines so a swift call to Simon Jenkins produced a flywheel, which appeared to fit the bill. Simon operates from a remote farm in Shropshire near Eccleshall. A quick telephone call and a visit and one flywheel 'by gum it were a brute' a good 3 cwt. ( 150 Kgm) Simon took pity on my C5 and offered to run it to the engineering company for a small charge. Once there it was machined to fit the shaft on the engine.

The next job was getting it to the museum and fitted to the engine. I gingerly decided to have it loaded into the back of my C5 which appeared to be quite happy and delivered it to the boat on the 3 April AGM day. Using the dockside crane and many willing hands we lowered the flywheel into the hole, and it fitted perfectly.

Would the flywheel do the job?

My next priority was the annual survey and steam test. The survey was done on the 7 April and the boiler declared sound. On Easter Saturday I boxed the boiler up and filled up with water. As the steam test was scheduled for Tuesday I steamed on Monday. A few weeps from the mud holes but as gaskets bedded in they soon stopped. Early evening the magic moment came.

It worked.

We had a test run to Factory and back. The engine runs smooth and is very easy to control and will now run with approx 60% cut-off, what on earth is that I hear you cry, read all about it in the next Steaming Up.

David Stott