Saturday, 29 August 2015

972CUF - August 2015

Work on the rear axle has continued since the last update in May, becoming rather a painful saga. After the refurbished hubs were put up, it was found the replacement brake drums wouldn't fit: they were binding on the new brake linings. Odd, as all of the replacement parts were new and within the manufacturer's tolerance. This vehicle is a side project, but quickly became the focus of attention for several staff for many, many weeks. The hubs were taken down, bearings rechecked and refitted; the brake pins and bushes checked for excess play - nothing amiss here; the brake shoes were swapped for others, again no difference; then, the brake drums were slightly turned down and checked for ovality. Finally, the near-side went together perfectly - ah, we thought, the off-side would be a doddle. Wrong. (The off-side hub is seen here, once more removed).

Hours more were spent carrying out checks. Finally, micrometer checks to the wheel studs (to which the wheels are fixed), revealed small variations in measurement between each stub.  This variation prevented the brake drum from sitting true. This bus has not yet joined our operational fleet since being purchased from its previous owner, and this sort of check is imperative to ensure future safe operation. It would seem that sometime in the past, the off-side rear wheel assembly has been strained, possibly due to hitting a severe pothole or similar. There was nothing for it but to change the studs for new ones; fortunately, these were in stock, purchased as part of an auction lot during the sale of items from the former Southdown garage at Hilsea. Here is a close-up shot of one of the wheel studs, and next to it the hole where one has been removed. Finally, we can report that the work was successful and at last the rear wheels are on!

PUF161H - July 2015

Much of the mechanical overhaul is complete, save for one or two jobs which need to be tackled nearer the end of the project. Earlier, when the front axle was checked, we found excessive play in the king pins. These are large steel pins fitted to each end of the front axle and enable the wheels to steer left or right. Too much lift or tightness can usually be adjusted through adding or removing shims. However, too much sideways play often suggests the pins are worn. Dreading the task ahead, much to our delight we found that new king pin sets are still available and very reasonably priced at that! A small miracle considering the vehicle is over 45 years old.

First, we stripped out the old pins and removed the stub axle. This is a daunting job, as king pins often seize in position. However, a few taps and out they came, much to the relief of the people involved. The first two pictures show one of the stub axles after removal of the pin. In the first. the wheel bearings run on the polished surfaces on the right hand side; in the second, the apertures in which the pin sits and upon which the stub assembly swivels can be seen. Photo three shows the end of the axle into which the pin slides.

Below: a pandora's box of replacement parts! The old pin is to the left; in the box is a new pin, new brass bushes, seals and grommets. 

And finally, the wheel assembly refitted, free from side-play.