This is a update on the completion of the Feifil Units for the Early Tiger 1. Those that have followed my posts will know that I had a problem with the elbow joints on the solid hoses. I have now made white metal parts which will not melt during the production of the spin casting mold, the mold for these parts will be made next week. This will complete all white metal cast parts.
The other problem has been how to produce the flexible hoses for the top deck. This I have pondered over for a long time trying to figure out how to produce them to give the correct look by following the contours of the engine deck as they should. I have three choices of material, white metal, rubber urethane and resin.
New white metal elbow hoses show with all other parts that make up the hose.
Advantages and disadvantages of materials
1. White metal.
Disadvantages. Heavy, difficult to cast hollow to reduce weight, will not bend easily and likely to break, casting lines on two sides difficult to remove flashing from detail of hoses.
Advantages. Accepts all types of paint is about the only advantage.
2. Urethane rubber
Disadvantages. Difficult to pour, casting lines on two sides which would be near impossible to remove from detail of hoses, cannot be painted with regular paint as it would flake off of the flexible hose.
Advantages. Flexible.
3. Resin.
Disadvantages. Not metal. Will be cast as a straight hose. Due to the design of the hoses minor air bubbles in resin are likely.
Advantages. Easy and to cast, accepts all types of paint, can be bent to conform to deck contours. Easy to cut and work with.
I am going with resin to make the hoses and will produce the first molds next week. Here is how I will over come some of the disadvantages.
Casting line.
Regular two piece casting mold leave a casting line on two sides of the part. These will be made in a solid mold which will be cut on one side only to remove parts from mold, the casting line can be positioned at the bottom of the hose so it will not show
Air Bubbles
I will use a low density resin mix, almost like water when mixed for pouring, type resin as every rib in the hose is a potential air bubble trap. The water type mix should alleviate most of them. The parts will pressurize during curing which should get rid of the rest of the bubbles, but a few may remain. Once I have done some sample pours I will post results here.
Cast straight hose.
Resin is effected by heat as most of you know, however the resin I use is not effect by the hottest days anywhere in the world if correctly cured. I did a test on a piece of 3/4" diameter resin today, about the same size as the hoses. Not this resin part I used was a sub-master part to make the Flak 38 trailer yoke and was never heat cured, it was cast about 4 years ago. I placed it in a oven at 150 degrees F (65 degrees C) for 30 minutes and was not able to bend it. This proves my observation in another post on Resins "Good, Bad or Ugly". I then reheated it at 300 degrees F (149 degrees C) for 15 minutes and it became soft enough to bend. I tried to bend it and it broke in half, tried to bend it to far. I then took one half and bent it as shown in the pictures below. This bend is over what will be required to match the contours of the engine deck. I ran cold water on the part to cool it quickly and once cooled it retained it's new shape, after 6 hours it was still the same. Full instructions on how to fit the hose will come with the sets. A brief instruction is cut and match the length of the hose once all metal parts are fitted, heat hose at 300 degrees for 15 minutes, fit hoses to metal parts and clamp in place, allow to cool and you are ready to paint.
Heat test pictures.
Regards
Mike
