The Steamboating Forum

18ft 6in wooden hull, Stuart Turner 6A fairly standard build.

After a day's running two weeks ago and half of today the boat started to make the occasional knock sound, sometimes sounded like it was something attached to the prop knocking on the hull and other times rather more, I hesitate to say "metallic", it was not obviously so, but it is a hard sound. It is not regular and does not seem to relate to a particular part of the cycle. It is louder when faster but did it when going quite slowly, (We had to get home).

I can not identify a sticking out anything, a bolt in the stephenson gearing for example, catching occasionally.

The only other great change this year was a new H.P. valve stem and gland which meant opening the H.P. chest and also a freeing of the piston rings which meant the taking out of the pistons; Lock Tited back as they came out with the piston rods attached.

Are there known problems if a "D" valve works loose? I am reluctant to strip it all down but this knock sounds potentially expensive!!

Advice Please.

H.P.

Is the knock repetative, say in time with engine revs, or just an occasional one?

Finding noises is all about 'ear', you have to listen while moving about to change it's direction 'til you can close down where it is. Once you have a good idea where it is then you can use a long thin object like a screwdriver as a stethescope (handle to the ear!) to listen to the noise and close it down further (steam-chest, crank, cylinder etc.). Engine noises are not usually intermittant unless the load or rpm changes, so try to make it do it.

As Mike suggests, get a yard stick and put it to your ear and touch check location to where it is the loudest.

Packing too tight can cause a knocking sound, it locks and breaks free at the ends of the stroke. I had that on my water pump following the old rationale "a little does a little good and whole lot does a whole-lotta good" Not always.

-Ron

You may want to swing by your local automotive supply store. Many sell what is commonly referred to as a "mechanics stethoscope". We've been using these for years and they're much more safe and effective when it comes to locating odd sounds, especially on moving machinery. Start from a location further away from the noise and work your way to it from several directions. Sometimes noise can be transmitted from the source and amplified somewhere else in the boat.

https://www.amazon.com/Lisle-52750-Stet ... ref=plSrch

https://www.amazon.com/Wekster-Stethosc ... ref=plSrch

Remember, point the ear pieces towards your face, as that is the direction your ear canal travels. Common mistake is for people to point them towards the back of their head and hardly hear anything.

The ones from horrible freight work well, and cost only a couple of bucks.

could water hammer in the condenser be a cause for this knocking?l; It is not consistent and does not seem to relate to engine revolutions per se.

There is also the odd engine squeak and a stethescope will be needed there. I am injecting oil into the wick oilers and it seems to go somewhere. The only places that do not seem to have an obvious source of oiling are the main bearings, which is strange for and engine that has run for many years to the point of wearing out the gland for the H.P. valve rod.

Thank you for thoughts H.P.

I've been on a boat with a 6A (not important in this example) that has an intermittent knock that is associated with the condensate pump. The owner said that it just does that sometimes and didn't seem concerned. It wasn't the check valves but some sort of issue with a slug of water working its way through the system.

Not having a condensate pump on Folly, I'm not too up on this sort of esoterica.

Yes hot steam hitting cold water will make a knocking sound. I had a condition on the tug where steam was making its way through a submerged thruhull fitting. Sounded like someone tapping the steel hull with a ballpeen hammer at random - not in time with engine etc. You may have a submerged leak in your condenser..

-Ron

Can you run it on compressed air and see if it still knocks? No load conditions obviously but even so I would of expected to hear something especially in conjunction with the screw driver scope method.

Something you might want to look at would be a possible loose piston. Or maybe check your strike points to see if anything has changed.