W/NG - Air Filter: improving the kit

I saw this air filter on eBay some while ago. It's an Indian made copy of the Vokes air filter used on military bikes towards the end of WW2. It looks OK, but it needs to be treated as a kit of parts to be fettled, supplemented and perhaps bits will need to be replaced...

As the bike has only just arrived from long-term storage the air filter hasn't been near it until today. Let's take a look. 

In this picture I have adjusted the feet so that they lift the main body of the filter clear of the tank. I've fitted the brackets used to retain the filter to the tank more or less in the right position.

The quality of this piece of equipment is nothing to write home about but the main body is more or less ok - the threaded retainers holding it to the tank are awful and are probably not usable. You can see how the misplaced bolt holes do not allow both bolts to be fitted. The retainers don't actually look very much like the originals anyway.

You can see here that the main box is fitted such that the inlet hose going to the carburettor will route down the back of the tank.

Here's another view from above which gives an idea of where the hose will run.

So we need to think about what we're going to use and what we're going to replace. At the moment my thinking is that the retainers will be replaced completely as will the brackets they bolt to on the filter itself. The eBay purchase did not include the hose to the carburettor or the felt filter tubes.

The filter tubes are made from some 2 mm thick felt sheet cut into 3 1/2 inch widths and sewn on the machine. They will be cut to length, turned inside out, and retained with some spring clips.

Here's all five felt tubes cut to length and completed.

I've bought these clips from eBay which look a lot like the original ones, though they are a bit wider. We may have to make a special tool to open them and get them in position!

I can't do much more with the felt tubes at the moment which I really only made to get them off the sewing table and because it was raining. We'll move on to some metal work on the main air filter box.

I've removed the nasty brackets which were braised and riveted to the main box. They are unusable, or at least this one is because the holes are completely out of position and at any rate whilst some of the original WD equipment is quite cheaply made it's not this bad!

Now that I have removed this bracket and flattened it out we can use this as a template to make a new one. I have some excellent pictures of an original Vokes air filter from the WD motorcycle forum.

This is the new one I have made to replace it, cut from a sheet of 1.5 mm steel. The nuts are M6 and brazed in position and the whole thing has been pickled to get rid of the flux.

The clevises supplied with the Indian kit were completely hopeless - way too small for a 1/4" thread or even the M6 thread they were supplied with. Here's the Mini-Lathe in action parting off some new ones, drilled 6.5 mm in the tailstock V-block for clearance on 1/4".

Here they are finished, with the tool that I used to create the dome in the ends. Looks very authentic!

Here are the new straps for the trunnions - these look a lot more like the originals and are a more appropriate size. There will be slots such that the straps can move around on the bracket on the filter body to align the filter retainers with the holes in the fuel tank.

Here they are again coming along a bit further with the slots cut and the holes drilled. These will be slotted eventually and the whole strap will be made a little shorter.

Here's one finished and in place:

Here's the other side. The next step is to fit the hose and see how it is going to pass the seat nose and the tank: