Bit random I know, but I was having a rummage in my memory today, and started thinking about the foden my dad used to drive for slater’s transport (HVY360N if anybody’s interested). The parking brake on it had a ‘J’ sort of arrangement to it, with park over and to the side, from where you’d move it to the unlock positio, and then half way up to the off position. All the way back was the auxiliary brake.
How did these work? From what I remember, there was a whistle when they were applied - was this air exhausting from the spring chambers, rather than air going into the service side (if that makes sense?). Did they use the springs to park on, with the unlock position re-pressurising it to release the brakes? Or have I got it all wrong? (Wouldn’t be the first time[emoji3] )
Thanks
Gary
These were called Lock Actuators and it is many years since I last even saw one. They were common on Fodens, Bedfords, Atkinsons and IIRC Commers. They were an early attempt at a mechanically-held air-assisted park brake. They were a PITA and not very reliably effective. The brake chamber had three ports. After writing out a description of how I recall them working I have now found a proper one from Heavy Vehicle Technology with diagrams so scroll down the pages to follow.Look for figures 369 and 377/8/9. The driver’s hand control valve operated against a resistance to ensure that everything happened in the right order, this was checked on MOT and lack of ‘damping’ was a failure. I think we used to have to top up the oil in the hand valve? 
Sometimes to release them you had to hold the lever in position while the air built up. Yes they did whistle.
books.google.co.uk/books?id=ZLJ … er&f=false
Remember having one of that type on a ‘K’ reg Atkinson 8 legger, the secret was to go through the release sequence slowly or you would have to start again and mess it up a second time and you would have to wait for the air to build up before the brakes would release. In reality it was only any good as a parking device and I used to use the foot pedel to hold the truck at traffic lights etc, but it was an improvement on the multipull cable handbrake which could be released before the air built up and leave you with no brakes as the spring chamber safety type were not in general use. Happy days. 
Many thanks for the replies - of course, the downside is that I’m going to have to get that book now, as I found it fascinating to look through! 
S80 had one of these, i liked how they worked, a straight pull for the secondary brake…resistance damped so there was some feel in it, then round the corner for the full parking brake.
Did Clayton Dewandre make them ?
Very fail safe i thought as a driver, no danger of using the secondary if needed and accidentally knocking it fully over to park brake, which given a whack on a kerb or similar with some of the other designs was a possibility.
Someone jog my memory here please, i drove S39 40 and 80’s.
39 had rod lever transmission park brake (brake drum behind the diff) and a seperate dead man on that big lump of steel casting posing as the dash all bolted to the solid cast steering column in turn bolted straight to chassis, 80 had the aforementioned J-type parking brake, but buggered if i can remember what the S40 had, it didn’t have a transmission brake as i recall but neither did it have the round the corner J brake of S80.
We only had Foden eighwheelers at Ballidon so I didn’t encounter that system. The S36/39/50/40 models we had all had the drum handbrake on the first diff, however they also had the triple chamber front brake chambers on the first two axles that operated as a secondary brake from an air valve on the handbrake lever. This only worked while the driver was pulling the lever hard, when parked up ‘on the ratchet’ it only operated the drum transmission brake. This was either soaked in oil or seized up, we used to strip them down at test time and the day they went for test was about the only day they worked!! You couldn’t use it on the brake rollers so we used to run the truck up the test slope at the station while half loaded, then put a pipe on the handbrake and stand up in the cab pulling like hell. We also had to swing our legs out of the door so the tester could see that we were not pressing the brake pedal with the ignition switched off, then when he was satisfied the problem was trying to get the ■■■■ handrake off again!!! 
The S80/83 models had conventional spring brakes on the 2nd,3rd and 4th axles, the later rubber suspension versions had the rear axle ‘reversed’ so that the brake chambers stuck out at the back which preventing the vehicle being able to tip into paving machines as the chambers fouled the rollers on the paver. The Haulmasters and the Paccar range were then fitted with spring brakes on the first three axles and a single chamber on the 4th axle which gave clearance for paver work.
Pete.
windrush:
We only had Foden eighwheelers at Ballidon so I didn’t encounter that system. The S36/39/50/40 models we had all had the drum handbrake on the first diff, however they also had the triple chamber front brake chambers on the first two axles that operated as a secondary brake from an air valve on the handbrake lever. This only worked while the driver was pulling the lever hard, when parked up ‘on the ratchet’ it only operated the drum transmission brake. This was either soaked in oil or seized up, we used to strip them down at test time and the day they went for test was about the only day they worked!! You couldn’t use it on the brake rollers so we used to run the truck up the test slope at the station while half loaded, then put a pipe on the handbrake and stand up in the cab pulling like hell. We also had to swing our legs out of the door so the tester could see that we were not pressing the brake pedal with the ignition switched off, then when he was satisfied the problem was trying to get the ■■■■ handrake off again!!! The S80/83 models had conventional spring brakes on the 2nd,3rd and 4th axles, the later rubber suspension versions had the rear axle ‘reversed’ so that the brake chambers stuck out at the back which preventing the vehicle being able to tip into paving machines as the chambers fouled the rollers on the paver. The Haulmasters and the Paccar range were then fitted with spring brakes on the first three axles and a single chamber on the 4th axle which gave clearance for paver work.
Pete.
Fascinating snapshot of the time Pete. Why should we make that effort to ‘get it through the test’ - then leave the driver to cope without it for the rest of the year? But we did! To be fair, brakes were improving in the early seventies. I think the spring actuated brake, which required positive air pressure to stop it coming on may have been the biggest advance, although they weren’t fitted to trailers at the time.
I was lucky and didn’t suffer from brake fade, apart from one occasion on the long descent into Damascus where the old bum was definitely going ‘half crown-tanner’ - and even that was arguably my fault, the trailer brakes needed adjusting and the tractor, an F88, which to be fair, didn’t have the best brakes to start with, was doing all the work!
Eddie Heaton has reminded me of a couple of occasions where he struggled, and I hope he won’t mind me repeating his words here:
I’ve experienced brake fade myself on a number of occasions in an 8 legger GUY invincible tipper. A couple of times dropping down into Macclesfield off the Cat and Fiddle, when the only thing you can do is to sit there long enough for them to cool down before you make the final descent. On another memorable occasion, it happened to me as I was dropping down into Glossop from the snake pass. There was a group of what appeared to be student types strung across the road holding clip boards, as though they were conducting some kind of census. I was fully freighted at the then limit of 24 tons. I had no chance of stopping and was frantically flashing my headlights to warn them to keep out of my way. Fortunately there was a copper with them who grasped the situation, clearing them to one side as I went thundering past in a cloud of white smoke, managing to bring the thing to a halt just before the steep drop through the town centre. Not an experience I would like to repeat
John