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Author Topic: hotbulbs  (Read 10311 times)

cylinderheadnut

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hotbulbs
« on: April 29, 2012, 11:03:22 PM »
Is there any benefit in running  a 2 stroke semi Diesel hot bulb engine on waste oil, they say the things can run on various oil fuels. would this avoid injector / pump problems , and be a simpler set up.

38ac

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Re: hotbulbs
« Reply #1 on: May 14, 2012, 02:26:23 PM »
Cant answer that but sounds interesting. I happen to own a 12/14 Petter S oil engine that I just got running well. Spares for it are both hard to find and $$$, none here in the states, all must come from over there  so I am afraid to try anying but #2 diesel or kerosene. Some were called crude oil engines were they not?? Seems like used motor oil and crude would go hand in hand? But maybe not? What type of hot bulb do you own?
Collector and horder of about anything diesel

cylinderheadnut

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Re: hotbulbs
« Reply #2 on: May 24, 2012, 09:32:52 PM »
12/14 Petter S's are like gold dust even over here, i'm trying to get a similar Seffle, Sabb, Bolinder ect sent over from Sweden, where they're 10 times cheaper, and quite common, for use in my boat, no luck yet.

Thob

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Re: hotbulbs
« Reply #3 on: May 25, 2012, 02:51:46 AM »
I don't have any direct experience with hot bulb engines, so I can only repeat what I've read about them.

Most hot bulb engines are low compression, around 5:1; as a result, they don't have the high efficiency of a true diesel.  That may not be a problem if your fuel is "free"*.

Hot bulbs tend to get cold when the engine is lightly loaded, to the point that they will quit if left to idle for a while.  Running them under heavy load can cause the bulb to overheat.  They work best at a constant load.

The hot bulb engine still requires some kind of injection, although they typically don't use as high an injection pressure as a diesel.  They might tolerate poor fuels better, but would still be subject to corrosion (especially from acids in WMO).
 
Part of the problem with using waste oil is going to be carbon and ash.  Both can kill an engine.  If the carbon builds up mostly in the hot bulb, it might not be too difficult to clean out on occasion.  But I suspect that the carbon would still get on rings and valves, requiring frequent cleaning.  And the ash is going to go everywhere you don't want it to (rings, crankcase), and it's abrasive.

A big part of the equation is going to be if you get your fuel for free, and can tear down and fix the engine cheaply and often, then it might be economically feasible.  But most hot bulbs are ancient machines with few spare parts available.  I would think they would be expensive to repair.

Don't let me discourage you - if you can get an engine and afford to play with it, let us know how well it works.  I suspect you'd be better off with an Indian Lister clone and plenty of spares.  Lots of people around here have real experience with that, and can advise you on what works.

*-even "free" fuel costs money - collection, filtering, centrifuge, etc.
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38ac

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Re: hotbulbs
« Reply #4 on: May 25, 2012, 01:30:04 PM »
12/14 Petter S's are like gold dust even over here, i'm trying to get a similar Seffle, Sabb, Bolinder ect sent over from Sweden, where they're 10 times cheaper, and quite common, for use in my boat, no luck yet.

I am told by my Brittish advisers that mine is the rarest of rare being a horizontal?
Collector and horder of about anything diesel

Sfene

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Re: hotbulbs
« Reply #5 on: May 25, 2012, 11:56:44 PM »
I wonder if anyone has tried to convert a Listeroid to hot bulb ignition? Replace the changeover plug to a hot bulb. Maybe advancing the injection timing long before tdc, the hot bulb being large enough to reduce compression to avoid preignition.....

Just a thought, maybe fun to try one day...

Tony

BruceM

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Re: hotbulbs
« Reply #6 on: May 26, 2012, 01:44:49 AM »
Or the modern version of hot bulb:

smartplugs.com

Alas, they're not selling them anymore.  I made one of these from Mark Cherry's first patent and converted a gas outboard (Honda 4 cycle 2 HP) to alcohol fuel.  It worked very well.   Same concept as hot bulb but uses a platinum element, heated with a very small current for some fuels.  The tube length and element temp affect timing.