Sabb Semi-diesel

I've had a chance to play with this now, and it has some features that I hadn't come across before. I was expecting to have to strip it down before doing much else, as it had stood for a while. As it turned freely, and the lubricator was passing oil freely to all points, I decided to see if it would go, after cleaning out the lubricator & flushing the fuel system through, and checking inside the crankcase that it wasn't full of nasties or the big end falling off

The sprayer is different from any semi-diesel sprayer I've seen before. The jet looks suspiciously like a Primus stove jet, giving a solid stream of fuel directly into the cylinder when on load. I can't imagine that gives very good combustion, but they made these things for over 30 years, I'll have to wait & see on that. For starting & idling, an angled, convex deflector is swung into place beneath the jet. This turns the solid jet into a spray, which is now directed onto the walls of the hot bulb (one side only) and the heated plug. Starting routine is to heat the plug, prime the hot bulb with fuel & then swing the engine hard against compression in the opposite direction to normal running. The fuel already in the cylinder should then burn, forcing the piston back off compression hard enough to take it over compression in the proper direction.The book says to get the plug red hot, I only had a little MAPP gas torch handy. This would get the plug to a dull red, & there was absolutely no life at all.

Yesterday I got the proper Sievert propane torch back, & tried again with the starting plug properly red. Instant results! A bit too lively though, as it ran away for a few seconds on the accumulated fuel & lub oil in the cylinder & crankcase from previous attempts, and from making sure that everything was very well lubricated. It is a hazard with this general type of engine that there is no way to control them in that situation. Particularly exciting in this case, as it was just bolted to the two pieces of 5" x 5" timber that it came on & did a merry dance as I tried to hang on to the fuel pump lever to keep any more fuel out of the cylinder.

Another try a bit later was much more controlled, but it really needs fixing down to the floor before a proper run!! Playing was actually ended when the lubricator bracket fell in half. It's a cast iron plate bolted to the side of the cylinder, & it's been repaired in the past by some rather feeble brazing. The stress of 250 miles on a trailer & then being shaken around on the floor proved too mush for the repair.

The governor will also need looing at. The book describes it as a Pneumatic governor, but it's nothing like the CAV type used on some Perkins & Bedford engines. All it consists of is a dashpot with bicycle pump type leather plunger, with an adjustable bleed valve. This controls what they call a 'pendulum', basically a spring-loaded crank which reduces the stroke of the fuel pump if the engine is running too fast so that the dashpot piston can't keep up. Has anyone come across this idea on other engines?

So far, I'm very pleased with the new toy.

I'll try to sort out some pics next time I play.

Cheers Tim

Reply to
Tim Leech
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It may be completely irrelevant but the Ogle nozzle looks just like a Primus jet. However the interior end is coned and there is a conical ended, and grooved, "needle" behind the jet in the sprayer body. The "needle" is missing from Dan's example which is presumably why he's never been able to get it running. regards Roland

Reply to
Roland and Celia Craven

Very interesting, Tim, thanks. I can identify with the dancing semi-diesel scenario.

The first time I got my Petter S going, after sorting out a fuel pumping problem, I also had a few failed efforts to start because the hotbulb wasn't hot enough.

When I did eventually get it hot enough to run, there was enough unburnt fuel in the cylinder to drive a small ship. The engine picked up revs, and it and the trolley and the water tank jigged up and down with it, throwing water around all over the place. Fortunately, I had the presence of mind to open the half-compression tap and grab the fuel lever. I gather from Roland and Philip TE that this is not altogether unusual for an S-type initiation.

Regards, Arthur G

Reply to
Arthur G

Sounds like fun! ISTR the ebay description referred to paraffin start - diesel run, not so I take it? I'd like to understand the dashpot governor better.

Reply to
Nick H

The vendor (the owner's brother) who did the description wasn't familiar with the starting process, but knew there was paraffin involved somewhere. The engine would have been supplied new with a paraffin blowlamp for preheating, but that's long gone.

I'll try to do some pics showing the governor, in the fullness of time. In the meantime,

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shows the component parts. Best of luck trying to understand it from that

Cheers Tim

Reply to
Tim Leech

"Tim Leech" wrote >

Ah, I see. I was envisaging some sort of Brons style paraffin cold start system!

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Err, thanks, and an assembly drawing perhaps?

NHH

Reply to
Nick H

There's nothing missing on this one, it really is just a plain jet, and the book specifically refers to a solid jet of fuel being the proper state. One bit of sophistication, though, is a spring loaded ball valve behind the jet to prevent dribble.

Cheers Tim

Reply to
Tim Leech

in the cylinder to drive a small ship.

and down with it, throwing water around

half-compression tap and grab the fuel lever.

S-type initiation.

I was told once of a proud owner chasing his wildly revving 12/14 hp S type round the yard. It was running so fast the Calibrater handle was a blur. The only way they could stop it was by chucking buckets of water in its general direction to cool the hot bulb down enough to stop it igniting the fuel.....

Regards

Philip T-E

Reply to
ClaraNET

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