Wind instruments

Among the fairly ancient electronics that came with New Morning was a set of Walker wind instruments one of the anemometer cups was damaged there was evidence of it having been repaired and then broken again. It was made of a flexible plastic somewhat akin to polythene which does not generally take very well to glue also the ball race anemometer bearings were worn out. The dials looked OK and the wind vane moved freely without any slack in the bearings and it was obviously a good solid piece of kit, but up to now that is as far as I had got with the system until this last week. The first job was to try and source some new anemometer cups the company that deals with Walker wind instruments could not help but they did offer me a replacement system for about £1500 or a budget system for £1060. Now I have never owned a boat with a set of wind instruments I have found a simple windex quite sufficient however as I had the system I thought I might as well add it to the challenge of rebuilding New Morning.

The first job was to strip and examine the anemometer head this was quite straightforward and it came apart quite easily.

Anemometer stripped

The bearings have a shoulder on the outer race and I thought that they may might have been a problem but I found some on a site called Simply Bearings ordered on Monday afternoon delivered by post Tuesday. The cups were going to be a bit more of a problem. Being an engineer my first thought was to make some new ones, not a difficult task, I decided that they would in all probability be too heavy to give a reasonably accurate indication of wind speed especially, in light airs as I would have probably used a combination of brass and copper, aluminium would possibly have been OK but the difficulty would have been in joining it together. I considered 3D printing however on consulting a higher authority, namely number two daughter who knows about these things, we decided that the shape and the available material would not be compatible there are some very thin sections. Finally I looked at other manufacturers equipment the problem was that they don't give a drawing showing the dimensions  however I came across spares for a VDO anemometer on the Furneaux Riddall website that did give the size of the cups and by a bit of scaling of the photograph it turned out that the PCD of the cups was a bit less than that of the Walker unit but the cups were a bit larger and the boss would need to be adapted to fit so I ordered one I figured that it was worth a try at £8.

The VDO and Walker cups

The VDO cups fit on a fairly thin spindle while the Walker spindle is of a much larger diameter with a hexagonal section to give a positive drive although this is probably a bit of overkill. I opened out the bore of the boss of the VDO cups and then machined the boss of the original cups down so that the new cups were a good fit.

Opening out the bore of the VDO cups

Machining the boss of the Walker cups

Machining completed

Parts assembled

The new bearings were assembled into the housing with loctite as they were sliding fit and then the spindle was replaced and secured with a 'C' clip the second part with the hexagonal section is secured by means of a small roll pin.

Bearings in place

Spindle in place

The anemometer operates on a pulse system or at least I assume that is how it works there is a rotor with 4 lobes that passes through what I take to be a magnetic field.

Rotor showing 4 lobes

Lobes pass through the gap

The body of the anemometer was then fitted back onto the masthead unit with the six countersunk machine screws the anemometer cups were then fitted and secured with the original nut to complete the job.

Complete masthead unit

At the moment I am not sure about the possible accuracy of the wind speed indicator the anemometer cups are larger than the original but the PCD is smaller whether or not they will cancel each other out I won't know until the mast is up  and the system wired up as the masthead unit fits into a multi pin socket on the mast I have no way of rigging a temporary connection. The other deviation from the original is that the new cups revolve in the opposite direction to the old ones I had to turn them over to fit them but as this is a pulse system it should make no difference.

I have connected a 12 volt supply to the dials and the two wind direction indicators do move and the back lighting works so there is every possibility that the system will work once the mast is up I shall be able to check the operation before deciding where to install the dials.

Dials