Picture Galleries > Making Chilled Iron Wheels
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pattern 1.jpg
Our carefully made pattern was set in an external pattern that formed the separaion surface for the two halves of the mould. This has 4 hemispherical locators on it that will eventially locate the other half of the mould accurately.
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tram wheel 4.jpg
This shows a 'chill'. The idea of this is that a ring of 'chills' which have a 'negative of the desired wheel profile on them are placed in a ring as part of the sand mould. When the molten iron hits the 'chill' it solidifies quickly and the crystalline structure of the wearibg surface is altered so that it becomes very hard. If broken open the 'chilled' portion is white in colour compared to the grey of the rest of the casting.
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tram wheel 5.jpg
When the upper half of the mould had hardened it was turnedupside down and a moulding tray for the lower half was built on tiop of it. This has a grid in its base that the sand would stick to swo that the whole mould can be moved by crane the right way up. The chills were carefully placed in position around the rim of the pattern. Spaces were left between them to allow for expansion of the chills during the casting process.
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Pouring the sand for the lower mould
The sand was then poured into the frame to set with the chills in position. Again this was done a bit at a time with each batch being compacted before the next pour. The process is still know as 'ramming' from the days when green sand was used with no catalyst when the sand had to be 'rammed' to make it compact and stick.
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Mould label
It was greato see the societires name on the label attached to the mould. A real sign of progress in the restoration of 107. The colour identifies the type of metal to the foundry workers.
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When the two halves of the nould had been finished they were placed on top of each other then a ton and a half of extra weight was placed on top to stop the upper part of the mould floating off the lower part when it was filled with molten iron. Here the mould for wheel 1 has been prepared while the mould for no2 is being finished.
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Here the lower mould has been coated with a fireproof mixture to stop the iron buring the surface of the sand when it is poured. The 6 chills are seen in position around the rim of the whel. Their size casued problems with expansion and they were later cut in half to leave 12 smaller gaps around the mould.
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At last the first melt of iron was ready in the cupola and this shows it being tapped into a ladle.
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The linig ws then set on fire to leave the fireprooofing surface on the mould.
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Finally the first pour was made into one of the tram wheels. The wheels were cast in pairs as the two that are free to rotate on the axle have long hubs and the two fixed ones have short hubs.
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However before being poured the molten iron was used to 'wash out' a crucible that had been used to produce a high chrome iron on a previous job. This added a bit of extra chrome to our metal. The idea of using molten iron to wash something out took a bit of getting used to.
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img00037.jpg
If I can ever get the software to let me move this image to the top it should be the first picture. 2 years of research went into producing a CAD drawing of a Millers no 3 Chilled iron tram wheel. This drawing was delivered to H Downs and son at Huddersfield who contracted out the pattern making to Gerald at Heritage Patterns in Meltham. here the pattern is shown part made. It is built up of layers of plywood laminated together then turned to the correct profile on a lathe.
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Anothe shot of the pour in process. Advice on shutter speed from the foundry owner produced this shot.
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The final pour was a test piece poured from the same lalde so that a matrial certificate with such things as the chenical composition and tensile strength can be given in the safety approval proces which is to come for passenger carrying.
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tram wheel 20.jpg
Finally we got the call that the foundry ahd 4 good wheels and so I wet to pick them up. It was a get sight to see a set of 4 chilled iron wheels ready for 107. 2 years of research and effort have finally produced half a ton of cast iron that is fit to carry a horse drawn tram.
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Having seen the wheels put onto the Transit by a forklift we had to get them off by muscle power only. Fortunately Gravity came to our aid and we slid them down two of 107's original corner pillars then rolled them into store.
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After a quick coat of primer to protect them it was a great feeling to see our new wheels with the letterring showing.