Cylinder Re-Bore
Over the past winter we have carried out several improvements to our Garrett tractor “Adventurer”. We started with removing the rubbers from the rear wheels and then Richard Maskell fitted full-width steel tyres so we could have rubbers moulded onto the rims. The wheels came back from Reliant Rubber at the beginning of December and work painting began. All filler had been removed prior to having a coat of primer, so trying to get rid of the worst pitting has taken some time.
At the same time work has been carried out on the motion. My son Hugh persuaded me that the low-pressure trunk guide should be re-bored and have new slippers fitted to the crossheads. One thing led to another and when we started dismantling it became obvious that both trunk guides should be re-bored and all the pins in the motion should be replaced. Both trunk guides went to Neil Gough in Sussex and whilst the work was being carried out, we thought we would hone the bores of the cylinders and fit new piston rings.
Careful measurement of the bores revealed considerable wear and the low-pressure cylinder was far from round. Arrangements were made with Neil Gough to bring his mobile boring machine and do a proper job. When he arrived, he immediately realised that he could not mount his boring machine on the front of the cylinder because the chimney and the chimney base were in the way. Once these were removed, he made a start setting up, bolting onto the studs of the end covers.
By the early afternoon of the first day, the first cut had been made on the high-pressure bore. Fortunately, it didn’t take long for the bore to be made perfectly round again with a good finish. Work then moved to the low-pressure bore. The setting up time was reduced but there was not time to start machining until the following day.
On the second-day work started on machining the low-pressure bore and the first cut revealed the cylinder was almost oval-shaped. This required a lot of machining. When completed both bores had a good finish but the final stages consisted of honing to leave a well-polished appearance. Careful measurements were made and now, the new piston rings are on order and will be fitted as soon as they arrive.
Most of the motion has already been replaced with new motion pins, die blocks and re-machined Stephenson links all work that has been carried out by Hugh. Our own DIY case hardening has now been greatly improved. The pins are packed in charcoal with pieces of leather and sealed in a steel box. The next stage is to heat the box in a fire until it is red hot, keeping it like that for a couple of hours or so. It works a treat. When the pins are cool, they are removed from the box and then heated until red hot before quenching.
I hope by the time you read this that the Garrett will have already completed a few miles on the road. Fuel and water consumption have never been bad usually covering at least 30 miles on six bags of Andy’s best Welsh dry steam coal and managing over 20 miles on a tank of 145 gallons of water. However, performance should be greatly improved.
Mike Dyson
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