A little metalwork

Starting to replace the air pipes I need first to get all the relevant parts back onto the chassis. This is a double change over valve (COV) that allows one of three air supplies to release the spring brake on the back axle.

Originally it was mounted on solid air pipes in the nearside chassis rail

But since I am using mostly nylon pipes now it needed a something solid to mount it

So I made up a little bracket in 3mm steel.

Should do the job!

Air pipes #1

I have started to replace the air pipes. The first section runs from the compressor to the small condensate tank behind the front bumper. 

The pipe from the compressor is deliberately long; it runs all the way round the back of the engine, through a hose to the offside chassis rail and back across the front cross-member. This is to allow the air to cool as much as possible before it reaches the tank. I reused the first three metres of so of steel pipe (with a coat of paint) because this can easily withstand the heat. Nylon pipe would not be suitable for this.

The steel pipe ends at a non-return valve behind the front cross-member.

I replaced the valve innards

The original steel pipe to the tank looks like this

Somewhat rusty and because I had moved the pipework to clear the new clutch master cylinder it didn't fit any more. So I replaced it with 5/8" nylon.

The ends used a 3/4" UNF thread and sealed with brass olives. I was able to reuse the tube nuts and just added new olives and an inner sleeve to support the nylon

I also refitted the safety valve and a schrader valve which I assume allows the system to be pressurised externally; that could be useful for leak testing.

Finally a nice new automatic drain valve. The old one clearly was not working because the tank was half full of water when I took it off.

Air tank inspection

A few readers were worried about the state of the air tanks on an old truck like this - that they may be badly rusted inside and unsafe. So i bought a cheap USB endoscope on fleabay 

I could then inspect the inside of the tanks. The image quality is not great and what makes the camera had to use is that there is a time lag of several seconds for the images displayed on the attached laptop.

It was good enough to see that the innards were not badly corroded - some surface rust and a fair amount of black gunge

A little more painting

I've been a bit lazy over the winter months but the other day got some more bits painted

Backing plate for the offside front brake

Air tanks

Then I refitted the air tanks

and also the new cab rubbers

Clutch conversion part 1

I did some work on converting the clutch to include an air servo.

The original clutch mechanism was simply a bar joining the pedal to the release lever and was fiendishly heavy: you had to brace yourself against the seatback to move it. I picked up a new air servo on ebay some time ago; I think it's a Man Diesel part

This servo is operated by hydraulics so the pedal needs to activate a master cylinder instead of the old push rod.

I picked up a master cylinder and clevis from these people carbuildersolutions.com

This has (I think) a bore and stroke that will match the servo.

The original clutch pedal needed bending slightly in the vise and thinning down to accept the clevis. I reamed the hole out to 7/16"

and made a brass bushing for the clevis pin

Quite a milestone actually because it is just about the first successful thing I have made on my lathe!

The spring loaded 'captive' pin for the clevis is a really neat idea: mush easier than messing about with split pins.

So flushed with success I made a steel pushrod complete with 5/16" UNF thread cut on the lathe (woohoo!)

The whole thing sits on the truck like this

I'm not sure that I have the pedal stroke correct but it will be good enough to get started. It's difficult to tell without the cab on and the other pedal fitted and so on.

Reassemble the n/s front brakes

With a handful of new parts to fit I reassembled the offside front hub and brakes.

New wheel cylinder in place; the original was scored and leaking. One piston was seized and you could see that only one brake shoe was contacting the drum. There is plenty of wear left on the linings so I simply gave them a clean up with a wire brush.

The adjuster mechanisms go through the back plate and are held in place with a double coil washer (I think it's a Thackray washer), a dished washer and a circlip. It sits in a recess in the back plate and I could not get it anywhere near on

I made a special tool on the lathe that would compress the spring and washer while I fed the circlip in from the side

This worked well enough.

Here are the completed brakes and hub

Footbrake Air Valve

I stripped down the foot-brake air valve.

Inside it looks like this

There are air two chambers one of which was quite clean and the other was full of white powder. The cylinder bore seemed good but then I noticed that it was cracked

so I ordered a new part. Came across one of those strange bits of pricing. A rebuild kit which by me reckoning contains a handful of o-rings and a filter is UKP128. The bit you see in the lower pictures is called a foot-brake 'portion' and is UKP 230 complete with all the internal bits and the entire valve which includes the angle bracket that you see in the first picture is UKP403

It seems that the portion is by far the best buy so I ordered one of those.