MadModder

I'm familiar with the Imbert etc gasifiers, and am not an enthusiast. Same for veggie diesel, though a little more sympathetic if the resource is plentiful and available. I was once roped in (as you say) to a veggie oil CHP scheme to produce power commercially. Well not roped in so much as offered a lot of money (to me) to design a couple megawatt plant for supplying a local yogurt company. My first question before I accepted the job was, where are you going to get the oil and how much will it cost? "Oh don't you worry about that, um Canada, we are working on that part of it, your job is just to come up with a plan, equipment, costs, etc." So I eased on in, with some trepidation, but I did need the money. A year later, when I had all of the plans, all of the costs to build, had worked out hourly demand schedules, maintenance costs, etc for the big final presentation, I asked again, what are the oil sources, and what is the cost per gallon so I can give final figures. "Oh, we're going to have that shortly, can you just leave that part out?" This time I said no. "Please, it's coming. We're finalizing..." No, I need those figures now.

Well of course they didn't have anything. The best they could come up with was inadequate supply at a staggering price. Something that seemed obvious from the start. I was paid all along, no hard feelings towards me, my plans and cost figures were considered very complete, but the two "oil" guys who'd promoted the whole idea got the hairy eyeball at that last meeting. Oddly enough the principal never fired them, and they continue to this day planning useless stuff. It's a wonder to me!

That engineer stuff you're talking about.....that sounds like fun!

So soapy water tells me that the leaks are where the diaphragm meets the chassis - just squashed by four bolts clamping the chamber upwards.

Dismantling proved a tad tricky and unfortunately resulted in me breaking the gas chamber exhaust port brass fitting - but that's why we have lathes - make another - done 

Close examination of the rubber showed that as well as the leak round the circumference there was a split in the middle that oddly didn't go all the way through.

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Rubber was 2 mm thick so I ordered some up which took ages to arrive and was actually 2.2 mm - never mind - press on and see if it works.

Well it did on compressed air on the bench but NOT on propane - more investigation required. It turns out that the genuine Zon pressure regulator that is supposed to output 1.4 bar was only putting out 0.5 bar - no wonder it's not working

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Now the pressure gauge has a bespoke needle vale attached to give a very throttled output as this regulates how frequently it goes bang.

Opening up the regulator I found it full of water 
Cleaning it all up and reassembling it now will only give 0.75 bar at max adjustment - adjustment is supposed to be sealed but we are Engineers aren't we - it's only a screw!

Lots of fiddling and multiple dis-asembly and reassembly later I got it up to just over 1 bar but only by the expedient of packing the main spring with a big fat washer !

Does it work - yes by heck it does 

Somewhat louder than a twelve bore shot gun, as set it cycles every two minutes with the needle valve as open as it will go. First 'shot' purges air from the pipes but after that off it pops nice and regularly

These work by squirting a charge of propane into the barrel and igniting it with a piezoelectric crystal that generates a spark.

First - clear the packed spiders webs from the barrel - done 
Second - check that the piezoelectric crystal works - done 
Thirdly - get a suitable small propane cylinder - Facebook Marketplace provides 
Fourthly - connect up and try it - failure, internal mechanism doesn't cycle despite gas coming from the regulator.

OK - get it on the bench, rig up a compressed air supply at the required 1.4 Bar pressure and try it again - obviously it's not going to go bang as only on air. Yes it cycles the mechanism but leaks are apparent round the diaphragm.

The diaphragm is key to the whole operation - gas enters a chamber whose lid is rubber this bows upwards under pressure and latches a spring loaded device that releases the propane charge into the barrel then clouts the piezoelectric device making it go pop.

We have a crow problem - they eat more chicken feed than the chicken do and it has to stop !

Over the years we've tried various remedies:

Fake Owls that nod and turn their heads - OK for a while but the keep getting blown over by the wind
Friend with a 12 Bore shot gun - OK for a while but the effect wears off
Slow Match rope of bangers designed for the job - highly effective but once lit they keep burning for several hours.

Now not wanting to overly disturb our holiday cottage guests I wanted something that I could start and stop at will (ie when they are out for the day). As I don't want a shot gun on the farm I investigated propane fired crow scaring cannons. They seemed ideal apart from the price - over £400 for a set up.

So an eBay - "Spares or Repairs" one for £50 seemed a far better candidate - surely they can't be too complicated can they ?

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Well it duly arrived - time to start poking around   

Nice choice of the Lister clone Steve, I used to be in contact with Ken Boak many years back.  He used to be a UK guru on Lister CHP use.  I still have a Petter AVA1 and alternator under a tarp that has to go at some time.   It was part of a design project I got roped into 😅 during the "Great Veg Oil Rush"  All the new stuff has pretty much made those ideas obsolete now, allowing silent running.

Thanks for the power revelations Steve  once my ribs stopped hurting I could see scope for you saving a wee bit of power 🤣