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Old 12-26-2016, 09:35 AM   #41
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And the point is? That if you run your boat on the rocks, you're going to have a lot of damage? That's not exactly limited to one form of propulsion.
Bravo !
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Old 12-26-2016, 12:57 PM   #42
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Just to set the record straight Otto Diesel was a refrigeration engineer and then went on to design the first experimental diesels which ran with a 'hot bulb' to ignite atomized coal dust, he quickly found that the engine worked far better on vegetable oils.
The first commercial diesels were fitted by a German truck maker called Bussing, who were granted the right to fix the word Diesel on their truck grilles.
Bussing was taken over by M.A.N Machinenfabrik Augsburg Nurnberg who carried on the practice of fitting a small chrome badge with the words Diesel.
M.A.N trucks now form part of the Volkswagen empire.

Otto Diesel was lost overboard late at night on a cross channel ferry from France to England to exhibit his Diesel engine at the London trade fair.


Incidentally the Volvo IPS contra rotating propellers was invented to drive the torpedo propellers by a foreman at the Royal Arms factory in Enfield, England.
Nothing new, just re inventing the longest serving invention, the wheel, which incidentally was a Phoenician invention.
Apologies for being a smart **ss.
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Old 12-26-2016, 04:49 PM   #43
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Sayswho.
Just to set the record straight Otto Diesel was a refrigeration engineer and then went on to design the first experimental diesels which ran with a 'hot bulb' to ignite atomized coal dust, he quickly found that the engine worked far better on vegetable oils.
The first commercial diesels were fitted by a German truck maker called Bussing, who were granted the right to fix the word Diesel on their truck grilles.
Bussing was taken over by M.A.N Machinenfabrik Augsburg Nurnberg who carried on the practice of fitting a small chrome badge with the words Diesel.
M.A.N trucks now form part of the Volkswagen empire.

Otto Diesel was lost overboard late at night on a cross channel ferry from France to England to exhibit his Diesel engine at the London trade fair.


Incidentally the Volvo IPS contra rotating propellers was invented to drive the torpedo propellers by a foreman at the Royal Arms factory in Enfield, England.
Nothing new, just re inventing the longest serving invention, the wheel, which incidentally was a Phoenician invention.
Apologies for being a smart **ss.
Excuse me for offering a correction, but I believe you'll find that the inventor of the diesel engine was a German (though born in Paris) mechanical engineer named Rudolf Christian Karl Diesel (1858-1913).
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Old 12-26-2016, 06:31 PM   #44
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I like my gearbox mounted out of the water.
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Old 12-27-2016, 12:55 AM   #45
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Bliss boat,
Correction accepted, It was from memory, which is clearly failing.
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Old 12-27-2016, 01:00 AM   #46
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Isn't the Otto cycle actually based on the gasoline model?
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Old 12-27-2016, 01:19 AM   #47
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I beg your pardon and correct myself. (I only had two snifters of brandy)
It was of course Rudolph Diesel, and (from my failing memory) I believe it was a man called Otto who invented the two stroke cycle engine.
I should've checked Wikipedia before replying.
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Old 12-27-2016, 12:15 PM   #48
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Otto cycle is typically spark ignition, two or four stroke. In engineer terms, constant volume addition of heat.

Diesel cycle is typically compression ignition, two or four stroke, constant pressure addition of heat. The fuel is injected over several degrees of crank rotation, the goal being to raise pressure and keep it roughly constant as fuel goes in and piston descends. Burn all the fuel at once like a gasser and things break.

In both cases, constant volume or constant pressure are rough approximations.
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Old 12-27-2016, 01:55 PM   #49
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For the nerdy, techie guys here, let me say a few words about diesel vs gasoline thermodynamics and the efficiencies that result.

As noted above, a gasoline engine uses a different thermodynamic cycle than a diesel, the Otto cycle. I won't go into the specific thermodynamics (and I am not sure I can remember them 50 years later) but the Otto cycle is fundamentally less efficient due the laws of thermodynamics than the diesel cycle.

Also gasoline engines are throttled at part load. That also causes a thermodynamic inefficiency compared to diesels, which are never throttled.

An finally the foregoing "efficiency" means amount of energy in the fuel converted to work at the output shaft. But gasoline has about 15% less energy per gallon as gasoline, simply because a gallon of gasoline weighs about 6 lbs and a gallon of diesel weighs about 7 lbs and both have the same energy content per pound. So the difference is approxmately 7 vs 6.

So how does all of the above add up in real world terms. The following is a guess (because I have since long forgotten how to do the math):

15 percent due to energy density
25 percent due to wot thermodynamic differences
10 percent due to throttling at part load

Overall a diesel at part load makes about 18 hp per gph and a gasser makes about 12. So 18/12 = 50% better efficiency.

The diesel spark ignition engine discussed above and on other threads only benefits from the energy density factor, so it probably is only 15% better than a straight gasoline engine.

YMMV.

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Old 12-27-2016, 03:44 PM   #50
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A predominant factor in the thermal efficiency calcs of both cycles is compression ratio. Higher CR, better efficiency. But with higher CR comes more thermal and mechanical stresses so they do not go too high. And on Otto, you run into detonation and preignition problems.

The big downside on Otto is that at part load the intake is throttled. There are pumping losses with throttling, but those turn out to be rather small. The biggest effect is that throttling reduces effective CR. Since there is a partial vacuum in the cylinder, compression does not start until piston has risen considerably. 9:1 at full power, 4.5:1 at light load. No such thing on the diesel.

We've gotten way off track here, but I don't feel like cleaning the shop.
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Old 02-22-2017, 12:58 AM   #51
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uniform elongation of Silent Chain

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The problem with any chain, including the above, is that each pin-to-link interface wears. Not much wear, but it changes the pitch slightly. And now you have sliding contact on the link to wheel interface. And add up all the pin to link wear and you get a considerable change in total length, aka "stretch". This forces the need of a tensioner mechanism that can gradually compensate fro the stretch.

I have no problem using chains in certain apps, but do have a problem with the tensioners presently in use. Little plastic guides of doubtful chemical stability, springs, hydraulic pistons, little springs and clips.

Belts need some sort of tensioner in most apps, mostly due to thermal expansion, but at least pitch remains much more constant than on a chain. The wear and thermal expansion dimensional changes less than chains. And quieter.

Neither is a silver bullet for all apps.

On the OXE I am real curious how the are guiding the outer surface of the belt as it courses down into the lower unit. Seems they would need some guides or rollers to squeeze the belt together to get a slim profile above the "torpedo" shaft housing. Can't yet imagine an easy way to do that.
Meantime I was doing a little house cleaning on one of my storage disc and ran across this little diagram that had existed in a PDF form, but I managed to convert to a jpg image.
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Old 02-22-2017, 06:49 AM   #52
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"The US miltary's single fuel requirement is sure driving some interesting engine developments."

The one that will most likely end up on cars and boats is the use of JP5 (kerosene) with very high pressure direct injection , and a spark (not compression ) for ignition. We would use diesel.

This gets the advantage of dense fuel and no requirement for the extra engine weight needed for compression ignition.

With air power & computer operating intake, exhaust and injectors , no camshaft or rockers are used.

A boat or heavy duty engine can use different computer timing to hold the exhaust longer for efficiency .

Flick a switch to change the computer and the power profile can be changed.

Or for purists ( and backwater areas) the engine can be mechanical, no electric or computer needed.

Compliments of DARPA , the only gov agency that is worth its expense.
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Old 02-22-2017, 09:56 AM   #53
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Meantime I was doing a little house cleaning on one of my storage disc and ran across this little diagram that had existed in a PDF form, but I managed to convert to a jpg image.
It might wear uniformly, and not wear as much, but they certainly wear at the pin joints. They flat out admitted such. And that changes pitch which then wears the sprockets.

Don't get me wrong, there are apps where chains work fine, but wear and stretch remain an issue.

Take the cam drive chain off a GM v-block engine and it is obvious that wear occurs. Sloppy as heck, even with all steel sprockets.
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Old 02-23-2017, 01:07 AM   #54
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It might wear uniformly, and not wear as much, but they certainly wear at the pin joints. They flat out admitted such. And that changes pitch which then wears the sprockets.

Don't get me wrong, there are apps where chains work fine, but wear and stretch remain an issue.

Take the cam drive chain off a GM v-block engine and it is obvious that wear occurs. Sloppy as heck, even with all steel sprockets.
I suspect that the serpentine configuration of those camshaft chains are contributing a lot to the extra wear you are speaking of. Without proper tension any 'belt/chain' drive is going to experience extra wear.

The more direct configuration of this marine chain drive I posted here is likely going to see minimal wear....







BTW, the Oldsmobile Tornado utilized such a silent chain link between their transverse mounted engine and transmission. It lasted over 100,000 miles from the reports I've seen
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Old 02-23-2017, 01:19 AM   #55
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Olds configuration

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BTW, the Oldsmobile Tornado utilized such a silent chain link between their transverse mounted engine and transmission. It lasted over 100,000 miles from the reports I've seen
Just found this...
Out in Front: The Front-Wheel-Drive Oldsmobile Toronado, Part 1 - Page 2 of 5 - Ate Up With Motor






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Brakes aside, the Toronado was a remarkable piece of engineering. No less an authority than Alec Issigonis, BMC technical director and designer of the Mini, had declared that front-wheel drive was impractical with engines over 2 liters (122 cu. in.), but the Toronado coped admirably with 6,964 cc (425 cu. in.), 385 gross horsepower (287 kW), and 475 lb-ft (644 N-m) of torque. For all its novelty, the Unitized Power Package also proved to be remarkably reliable. The production line — established in a separate building from other Oldsmobiles — had its issues early on, but there were few problems with the drivetrain in service.
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Old 02-23-2017, 02:12 AM   #56
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Alfa Romeo twin cam engines with chain camshaft drives had an adjustment to take up the slack as the chain wore/stretched. Unless done carefully all the valve stems could be bent. Do not ask how I know.
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Old 02-23-2017, 02:55 AM   #57
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Alfa Romeo twin cam engines with chain camshaft drives had an adjustment to take up the slack as the chain wore/stretched. Unless done carefully all the valve stems could be bent. Do not ask how I know.
Those are totally different types of chains,...they are roller bearing chains.

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Old 02-23-2017, 06:32 AM   #58
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I suspect that the serpentine configuration of those camshaft chains are contributing a lot to the extra wear you are speaking of. Without proper tension any 'belt/chain' drive is going to experience extra wear.

The more direct configuration of this marine chain drive I posted here is likely going to see minimal wear....







BTW, the Oldsmobile Tornado utilized such a silent chain link between their transverse mounted engine and transmission. It lasted over 100,000 miles from the reports I've seen
Very interesting product which should be much more reliable than the standard z-drive out drive configuration with all its drawbacks. I'm wondering why it hasn't become more popular : maybe cost and the limited HP rating?

Pyi doesn't list it on their site; any idea of a ball park price?
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Old 02-23-2017, 07:25 AM   #59
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Very interesting product which should be much more reliable than the standard z-drive out drive configuration with all its drawbacks. I'm wondering why it hasn't become more popular : maybe cost and the limited HP rating?

Pyi doesn't list it on their site; any idea of a ball park price?
It was fairly expensive. There were 2 different sizes for two HP ranges. They only built them for a very short time, then stopped,...I don't know all the reasons why. (maybe legal concerns, see below).

I did hear of one installation on a big custom cat (French I believe) where the outdrive leg was hooked up directly to the engine without any intermediate shock absorption driveshafting, and of course it vibrated itself to dead. Then the builder/owner sought warranty on the item, when in reality it was an installation error.

As you said I think the concept has a lot of pluses over a Z-drive.

I've even drawn up a little idea for a duo-prop version...
Tennant Hull V ChainDrive

Thought about having the metal housings made up over in Thailand at one company I know of, then putting America bearings, seals, and drive chain(s) in them.
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Old 02-23-2017, 07:59 AM   #60
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Only thing for sure is I stay away from car engines with cam driving belts.

Our Honda CRV has a chain , so every few years it does not need a new belt.
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