Thursday, 23 May 2019

Sorry Sir, we don't make that part anymore

We're late cutting the grass in the orchard this year.  Essentially I've been busy on other projects and "the grass can wait".  One of the neighbours kindly helped me out one recent weekend by mowing approximately two thirds of the grass using our Hyundai Field Trimmer. Considering he'd never used it before, he did a really good job. Thank you Ian!

After we'd packed up for the day, I thought it was about time I gave the machine its annual service. This normally just changing the oil, which is messy because the drain plug is not well positioned on the Hyundai.  Now I use an oil vacuum pump which makes life a lot easier, but you have to remember to measure the amount of oil you've removed. When filling with fresh oil it needs to match the amount you remove. Over filling creates some spectacular smoke clouds from the exhaust if you operate the trimmer down a hill slope.

This year I decided to change the spark plug and the carburettor air filter. The plug change was easy, though it did highlight the spark gap on the old plug was too wide. A correctly gapped plug made a good improvement to the starting process. I also looked at the air filter. It was quite dirty so it definitely needed a change. I'd ordered a replacement air filter a couple of weeks before, and had it ready. Unfortunately when I came to swap out the old and new filters, I discovered the new filter was too small, by about 1 cm in width and breadth. It wouldn't lodge securely in the filter holder on the field trimmer. I  took some photo's of the parts and contacted the suppliers. "I'm sorry, it looks like we sent you the wrong filter. We'll post you the correct one immediately."

I waited a week, but nothing arrived, so I contacted the distributor again. "We have sent you one, but it must have gone astray in the post. We'll send you another by tracked mail."  Sure enough, a couple of days later the new filter arrived.  It was still too small, the same size as the original one they'd sent to me. I made contact again and we agreed that Hyundai had probably changed the design of the air filter and housing.  I'd purchased the machine in 2014, so I was disappointed the spare part was no longer available. However, by good luck, my workshop is set up for resin casting and making Silicone Rubber moulds. I told the distributor, not to worry and that I would cast a mould in silicone rubber to adapt the new filter block to make it suitable for mounting on the "old" field trimmer.

When I checked my supplies of silicone rubber, I decided not to open an expensive new can of the component parts, but that I'd just use bathroom silicone sealant. It is essentially the same as silicone rubber, but uses moisture rather than a catalyst hardener to cure to its tough rubbery state.

Draw around original filter shape on to polyethylene plastic


Cut a cardboard template to the shape of the base

Build a plasticine mould to the outline on the plastic

Position the new filter centrally in the outline

Hold the filter in place using a weight, then apply silicone in the gap

I left the assembly overnight and extracted the casting later in the morning. The silicone had hardened quite well and is a very close fit to the replacement filter. It is now installed and working well in the Hyundai Field Trimmer.

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