NARROW BOAT ZEUS
Zeus has now been sold. I leave this page here in case there is anyone interested in looking inside a Parsons Marine gearbox. You never know....
David and Kate and the trials of moving a harmonium to their narrow boat.
This page will now be more devoted to the working end of the boat.
Recently the boat developed a tendency to not want go anywhere, this was identified as an intermittent drive through the gearbox to the prop shaft. Initial indications appear to be that the multiplate clutch was worn out as there was little or no adjustment left on the actuating mechanism.
In hindsight now, we should have known better. The gearbox is approx 2.5 feet long and about the same in depth and breadth. This does not include the reduction drive, which adds another 8-14 inches. It does seem more suitable for driving a pit cage with 10 people in it rather than a propeller. As if the canals could wear it out…
So the decision was made that the multiplate clutch needed to be inspected, and as the box was far too heavy to remove from the boat, which is tied up a good half mile from the nearest road. A disembowlement would need to be carried out in situ.
The propellor shaft was disconnected and the top half of the gearbox was removed.
OK now to take the reduction gear off the back of the gearbox. This is necessary so that the entire contents of the gearbox can be lifted out. Various bolts and studs were removed, but try as we may we could not remove the rear cover of the reduction box without a puller.
So work ceased for a week while 7/16 bsf studding was obtained and a bar constructed to take a large nut and bolt. 6 hours so far. Whereupon the cover came off quite cleanly, using the oil seal housing as a part of the extraction device.
There is a large 1.5” nut at the end of the gearbox mainshaft where it pokes through the reduction box, and it was on tight. Probably because it’s thread was whitworth so quite coarse. No tool we had would loosen it. Fortunately the chandler at Shepherds Patch Bridge on the Sharpness Ship Canal, near to where Zeus is tied up, was generous and lent us a brand new socket and long wrench. After some struggle the nut gave up the uneven struggle. That left the lower large reduction gear (see inset above) to be removed. This required putting the hub back on the output shaft, re-attaching the propshaft (after swinging the gearbox to one side, having detached it from the engine) and using a heavy weight to slide back to the end of the propshaft in the manner of a hammer puller. Now the rest of the retaining nuts could be removed. With some judicious persuasion persuasion, the reduction gear was knocked back and off the gearbox. More dismantling (and cursing) and the innards were triumphantly hauled out on to the towpath. Another 6 hours, but much celebrating in the pub now.
Having got the guts of the beast back home, time to take a closer look.
Split it and lo and behold nothing wrong with the clutch plates at all.
But there was a lot wrong with the thrust toggle.
Needless to say this component could easily have been removed from the gearbox without taking very much apart. However perhaps the peace of mind of knowing that the rest of the box is OK does give one confidence for the future.
The new part has been made - £30 for materials and 1 bottle of Barcardi for the making of it. Looking good.
So as a Haynes manual would say "Refitting is the reverse sequence to removal". And so it is - believe it or not. Time to put everything back together was about 5 hours. Care had to be taken in assembling the reduction box as the bearings are a reasonably tight fit in the housings.
Adjustment of the thrust bearing toggles appears to be very fine, a bit like a go-nogo gauge. Keep winding the toggles in evenly and when one can no longer physically select forward gear, back of the adjustment slightly so that you can engage. It is vital that one ensues that all toggles are adjusted to have the same clearance as each other.
The reverse gear adjustment is simply a matter of making sure that the band has a definite clearance from the drum when in neutral and forward, and does grip well when in reverse. Make sure that the band does not have a tendency to grip the drum when in forward gear, it can happen even though it has a clearance in neutral.
Here is the rebuilt engine and gearbox.
As can be seen there is nice flush coming from the blade at a high tickover
Finally, a test run between Shepherds Patch Bridge and Purton Bridge on the Sharpness Ship Canal.