Now this is an American engine! - PeachParts Mercedes-Benz Forum

Hatterasguy · #1 07-13-2006, 11:09 PM

http://www.ptboats.org/20-01-05-ptboat-008.html

Those things can suck fuel, what does 100 octane cost today? $5 a gallon? so $2,500 an hour at WOT.

Thats no wussy modern computer controlled engine, it is from a time when engines spewed leaded emissions, sucked fuel through carbs, and leaked oil like crazy.

Love PT boats, I have seen the ones in MA a couple of times. It must be really fun to ride one. 40 knots was amazing for a boat of that size in 1940.

TheDon · #2 07-13-2006, 11:11 PM

kinda like the one in JFK's PT boat eh

diametricalbenz · #3 07-14-2006, 01:51 AM

$2,500 an hour......still cheaper to operate than many aircraft.

t walgamuth · #4 07-14-2006, 03:17 AM

the front end of the motor reminds me of an old novi engine.

tom w

Botnst · #5 07-14-2006, 08:18 AM

That's a compressor on the front?

B

Kuan · #6 07-14-2006, 08:44 AM

Read the specs: 2400rpm max, 2000rpm sustained! Fresh water cooled!

Quote:

Cylinders: 12 - V angled arrangement

Supercharger: Gear driven - centrifugal

Cooling: Fresh water

Maximum RPM: 2400 rpm, 2000 rpm sustained

Rating: 1200, 1350, 1500 depending on year of manufacturing

Fuel: 100 Octane gasoline

Fuel Consumption at 40 knots: Top speed at 40 knots, running three engines, 474 gallons per hour. Full fuel load (3,000 gallons) 6.3 hours.

Fuel Consumption at 40 knots: Maximum sustained speed at 2000 rpm, running three engines, 292 gallons per hour. Full fuel load (3,000 gallons) 10.3 hours, range radius of 259 miles at 35 knots, 518 miles total.

Botnst · #7 07-14-2006, 08:51 AM

Duh-oh!

Hatterasguy · #8 07-14-2006, 10:06 PM

Looks like the carb sitting on top of the super charger, at least thats my guess. I'm not really familer with the old stuff.

Botnst · #9 07-14-2006, 10:12 PM

I'm curious what the advantage (esp. in the 1940's) would have been for a gasser vs diesel in a boat?

I don't know squat about the 1940's industrial-strength engines, especially for marine use (botanist). But I have a hard time coming-up with a reason to go with Avgas vs diesel.

B

Emmerich · #10 07-14-2006, 10:57 PM

Quote:

Originally Posted by Botnst

I'm curious what the advantage (esp. in the 1940's) would have been for a gasser vs diesel in a boat?

I don't know squat about the 1940's industrial-strength engines, especially for marine use (botanist). But I have a hard time coming-up with a reason to go with Avgas vs diesel.
B

Might be there was a better HP/weight ratio? Being a modified aircraft engine it had many features of aircraft engines such as supercharger, intercooler, dual magnetos, two spark plugs per cylinder, etc. Maybe this did not exist as good technology at the time for diesel engines.

Another guess would be the type of fuel the fleet carried, maybe it was mostly fuel oil for the ships and avgas for airplanes, avoiding diesel would eliminate a 3rd choice??

Botnst · #11 07-14-2006, 11:14 PM

The fuel issue sounds reasonable. I entered the USN when we were converting from NSFO to JP-5. I had forgotten that in the 1940's the Navy used a fuel even less refined than NSFO, Bunker-C. Carrying bunker-c, avgas, and diesel would have been logistically burdensome. I don't think an I.C.E. could be built for bunker-C so it had to be avgas.

What about american manufacturing back then--could we mass produce diesel engines as quickly and with consistent tolerances as gassers?

B

Emmerich · #12 07-14-2006, 11:32 PM

I bet the Germans could.....oops.

Hatterasguy · #13 07-14-2006, 11:37 PM

Their is no way you could get that much HP out of a diesel in 1940 and be able to fit it within the hull of a PT. They were heavy slow engines.

The Germans did use diesel patrol boats, forget their name but they were much larger like 120ft.

Botnst · #14 07-14-2006, 11:45 PM

That sounds like a limitation of metallurgy rather than manufacturing.

I guess that within the past 20 years we've transitioned a cross-over in efficiencies between boiler-steam turbine and diesel-electric, favoring I.C. diesel or gas turbine burning diesel, at least for ships.

I guess there's an analogous revolution going on for small craft motorboats from gas 2-cycle to gas 4-cycle or diesel. In all honesty, I watch boats less closely than I watch evening primroses, so I know full well I could be way-wrong.

B

Hatterasguy · #15 07-14-2006, 11:50 PM

High speed powerful light diesels have only really been around for 30 years. Back in the 60's everything was natural. I remember a 1968 vintage sportfish that I was on that had state of the art in 1968 V8 na Cummins. Massive na diesels that made all of 300hp each. When the boat was re powered by modern Cummins B series, the new engines were so light they had to add tankage to get her to sit right.

The new I6's look so small in place of those old V8's but put a couple hundred more hp then the old ones.

I don't know how much one of those Packard V12's would weigh, but I bet HP to weight would be similer to a 12V71TI.