I had to do a search to find my previous posts in Nov. 2008. It has been so long since I last posted. The work only resumed when the weather go too bad to do things outside, about October I think. My generator set was in the idea stage then and it went through various unsuccessful stages from which I had to retract and a lot of it, with photos, is on my website : http://www.maribelecosystems.com/OldEngines.html
Since the last entry on the website I have got the thing running quite well and the end design is that the engine has a larger pulley on the shaft with 3 belts to give the correct alternator speed at about 1000 rpm. I was talking to someone who seems to know his Perkins P3s and he said it probably was from a tractor which could be set on a hand trottle to run at 1000 and at this speed it would probably still develop between 20 and 30 HP. It is very happy at this speed and considerably quieter, than it was when running at 1500. It is now bolted with 1/4 inch rubber sheet packing directly to the bed and is very firm, but not absolutely rigid. This is how it seems most comfortable. I have also got the beginnings of an exhaust pipe and a silencer will be welded in between the two mounts for the flexible pipe as it is, above the alternator.
The main problem now is that on trying to start it, the weight of the alternator rotor is an awful lot, especially geared up a bit and - even worse for the starter, is the extremely low temperature in my workshop, lately, which thickens the engine oil to the consistency of treacle!
I fitted a glow plug from another engine into the block drain plug and I warm the whole block now, using an 8 amp battery charger
I am still thinking about this and have now rigged up a system like a clutch so that I can start the engine, - de-coupled from the alternator. It consists of 3 belts quite a bit bigger and an idler that can be screwed in to push the backs of the belts in to tighten them as soon as the engine starts. I have not tried this yet, but I don't see why it shouldn't work. I have an old Condor mower that uses a belt tension idler to act as a clutch. That's where the idea came from.
The engine - at the moment has a closed cooling circuit which only hold about a gallon, with no radiator, as it will be a CHP system, so it only runs for about 10 mins before it starts to overheat. However I did get the alternator up to speed and had a bulb between one phase and neutral. Without any excitation at all it was about half bright. I connected 2 bulbs in a series circuit with the shed single phase and got the speed correct and then tried connecting a low dc voltage to the excitation winding. Although I would have expected it to require what was marked on the plate of the excitation generator, i.e. about 16 volts at 1.8 amps. It went right up to full voltage with only 6v from a dual voltage battery charger. After I had put a proper 3 phase socket on the side of it and wired that and a 13a single phase one, I connected the output to my Denbigh mill and sure enough it ran perfectly OK, - albeit backwards!
The question is, will this be enough? I can easily measure this voltage and then feed an appropriate amount of real DC from a sort of zener stabiliser, or will it have to be a "proper" AVR ? I reckon the actual speed will be quite stable as it is set by the diaphragm operated fuel injection pump and I did not notice any variation when switching the mill on and off. The lathe might be another matter though, - ideally I would like to run it on the 7 1/2 hp setting to get the full capstan speed of about 1000 rpm. Up to now I could only run on the 3Hp position - top speed 500 rpm. Went I get it starting easily and with more cooling I shall connect the Herbert to it. That may take the wind out of it's sails!
Next time, I am going to put in the cooling system a heat exchanger with a central heating pump controlled by the water temp pumping water from a big 40 gall drum, through it. This will allow me to run for much longer.
The chassis is off the ground on timbers, now as when I was pushing it into the workshop both the castors got stuck and all bent, I was on the tractor so I couldn't see what was happening. I really need some heavy duty ones under the Alternator end, as it is really heavy. I may even have to fabricate some disks wheels out of steel plate as they will only be used on concrete. Castors would be better but have you seen the price of them? That end of the frame is easily a ton.
Thanks for any comments, regards George.