Wheel Nut:
Old John:
Wheel Nut:
Its a simple butterfly valve like a carburettor choke that slows the air getting past, its just back pressure that slows the vehicle or in the case of a DAF stops the engine.It is not linked to the gearbox, axle cooling system or anything else, it sits in the exhaust manifold, the higher the engine revs the more efficient it is.
I beg to differ regarding the exhaust brake not being connected to anything else.
Of course it is. It’s "connected"to everything, or it would have no effect at all on the progress of the vehicle. The Instant that you lift your foot off the accelerator, instead of the engine working to turn the wheels, the inertia of the vehicle is working to turn the engine, (provided that the vehicle is in gear and the clutch is engaged) , the effect of any system apart from the wheel brakes depends entirely on that connection. So, from the friction of the tyres with the road, all the way to friction between the clutch components, everything requires to be connected for any of these systems to have any effect on the progress of the whole vehicle.The OP asked about an Exhaust Brake, not an Engine Brake - VEB or Gearbox Retarder. You also had the option of the Telma type on coaches which were a magnetic force on the prop shaft.
Remember the Spanish trailers and
rigids with the glowing disc brake on the rear axle. It was a similar set up as a Vanwall race car. A disc brake on the tail shaft of the gearbox which slowed the engine and wheels together.Comparing a gearbox retarder, Jacobs, VEB, or TELMA to an exhaust brake is akin to comparing a ratchet handbrake on a PSK to a wax thermostat.
A middle aged driver may remember the exhaust brake on a Volvo F7 - F10. A button on the floor and a switch on the dash. It was orange and had a safety catch on it.
Can you explain what it was for?
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Fair point, but I think both Dan and I explained the workings of an Exhaust brake quite clearly.
I have seen Spanish trailers up this way, the ones that carry live shellfish particularly, usually from around the Asturias region. Seems to be less common now, but some of them had retarders on one axle of the trailer. It was a great idea, and I think that they were usually electromagnetic (Telma) types. Some of the tractor units had them fitted also. They worked on the same principle as an electric motor, but in reverse, and it may have been the rotor of the retarder(the part attached to the prop shaft) which you saw glowing. I’m not sure.
Perhaps it is less common now as engine brake and other retarder systems have got so good.
Re. Volvo exhaust brake controls. I don’t know. I had an F86, then had lots of UK produced trucks until I went back to Volvo with FL10/FM12/ FM13, so I know little or nothing about the F range trucks.
I have an oldish R type Scania now which has a hydraulic retarder on the gearbox. It’s very good, but no better than the Volvo engine brake.
I feel that these systems should be standard fitting on all heavy trucks, as, used properly, they really are a great asset to safety. As an example, I run heavy most of the time on very hard roads. The truck has done around 70 thousand K since I had new discs and pads fitted to th drive axle, and the pads still have 80% material remaining.
), wonder how they’d have got on back in the days of drums all round and manual adjusters 
