Tuesday 29 March 2011

Drive Shaft Fitting Time

I have been waiting for an engineer to fix a date to come and fit the drive train. Despite several calls it was, clear I was getting nowhere so as usual its back to self reliance.  I do get fed up with this culture that seems to prevail these days where instead of saying straight out no I don't want the job, or even I can't be bothered, people just string you along in the hope you will get fed up.  I never run my business like that.  Its a waste of everyones time and effort. Rant over :-)

I never really had any problem with the task. It's simple engineering which I am experienced in.  My main concern was doing the work myself and invalidating the warranty.  I have sorted this issue now.

So today I picked up my key piece of kit for the job.  A turned collar made by a local engineering firm.

The shaft, the collar and the gearbox to flex drive adapter

Here's what the collar does.

The collar centers the shaft on the adapter plate

The fit is a tight one or an "interference fit" to give it its correct term.  With that done I was able to to bolt the adapter plate to the gearbox flange and have the shaft now perpendicular to the thrust line.

Although the shaft will have a flexible coupling its important that the shaft is set without relying on the flex to take up any inaccuracies.  With the shaft set right "solid" the flex coupling will work a lot better and a lot less hard.

This is the stern tube

I had done my calculations when I made the engine mounts and provisionally adjusted the engine mounts I had no idea I had got it so near.

See the tiny gap at the bottom?

I put two bolts in the top at 10 and 2 o'clock only finger tight this was how near my calcs were.   Don't you just love trig?

A few turns down on the front engine mounts and this gap closed up and a third bolt was put in finger tight at 6 o'clock.  I then rotated it by hand to feel for any tight spots, but all was smooth.

All that remained was to make sure the engine was set square on the engine mounts and the shaft was central to the boat.

 Starboard 203mm

 Port 203mm

 Zoom this picture up

Next job is to weld it all in position.

In preparation for work on the stern tube and later the rudder I had to have a space excavated under the back of the boat.  Frank and his trusty mini-digger once again obliged.


  1. Perfect :))

    Now that had to make your day.

    Bill Kelleher

  2. Well it did surprise me to say the least. More that I got the trig right than it was so close.

  3. Surprisingly enough that's not the first time I've seen an excavator dig out space to work on a boats steering gear! ;-) Nice job Kev, the planning certainly looks to have paid off nicely. A nice straight drive train will be a happy drive train. I went a slightly different route and bought a Python drive (thrust bearing and CV joint).

  4. I will be having a flexible drive between the gearbox and the shaft.