January 2004

Bearings and pulleys

Nigel in work made me a bearing support platform on the fly-press. Itís a simple piece of equipment but it does the job, didnít take long, and the result was perfect. Thanks mate.

I deliberately made the lower bearing support platform a few millimetres too low, so that I could use 1.5mm and 3mm shim plates to raise the bearings the exact amount to provide the correct belt tension. (If I had made it too high, the belt would have been too slack and I wouldn't be able to increase the tension).

With the bearing platform inplace I could then attach the pulleys and belt for the first time. It took a bit of adjustment, and needed 2 shim plates. But, on checking the belt tension, it seemed that the lower pulley was being pulled upwards at an angle. On closer inspection, the slight belt tension was distorting the angle bracket slightly, and the face of the lower pulley was no longer at 90 degs to the frame. If it did that under very mild tension the metalwork was obviously not strong enough and needed strengthening.


So I welded on bracing pieces made from angle and tried again. This time the platform didnít distort, but the belt was too tight, so off it came and I added another shim and refitted the belt. Was the angle strong enough? Probably. 1 inch square section tubing would be over the top, as these pieces are in tension.

Flow straighteners and cones

The flow straighteners are glass-fibre mouldings that are fixed inside the duct behind the fan pulley. They turn the rotating air flow from the fan blades into a straight flow. These (allegedly) give more thrust and better steering.

The 5 glass fibre flow straightener blades I bought from K&M were difficult to fit. The idea is that the blades should all join together at the centre of the duct and form a half cone, which then joins onto a separate one-piece half cone and this whole assembly sits behind the fan pulley. I trimmed-up the rear half cone and cut a disc of MDF to brace its base so that it could be fitted correctly, but there was no easy way of aligning the angle of the end of the blades to the inside of the duct. I decided I'd come back to that at a later date

I also have a "full cone" from K&M which sits in front of the top pulley. It is a stationary component and it helps to direct the air around the pulley and fan hub and through the fan. I cut the rear end to mount the cone over the fan shaft cross member, then welded a pair of short brackets to the front of the fan shaft cross member to support the half cone. This was then drilled and tapped holes for M6 screws. Now that looks the biz!

Skirt fixing

I am using a 57 segment skirt, bought pre-made from K&M. So whatís the best way of securing the skirt segments to the edge of the hull? Clamping seems to be the favoured method, rather than putting screws through the skirt material.

As I had a spare long length of plastic gas pipe I reckoned I could cut this up to make some curved strips which would have a natural bend. Making 57 skirt attachment strips was a pain, but I could do this in a warm lounge in front of the TV. Using a template meant I could drill the attachment holes very quickly, and any strip can be used in any location. Taking the template idea further I made a frame-drilling pattern, and drilled a series of fixing holes in the outer frame to the same pattern for every segment. I tapped each hole M6, so fitting a skirt segment should be quick.

The lower part of each segment will be attached to the hull via P-clips, so I drilled more holes in the planing panels. These holes will eventually be backed by metal washers to spread the load of the P-clip.

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