Catamaran Drive system Comments
Brian,
If you guys are working on a new drive system as you described
consider including something like the Nissan continuously variable speed
automatic transmission in the design. You are aware of the typical
significant difference between the rpm and power producing/absorbing
characteristics of a diesel engine and the propeller. The prop is designed to
absorb the total hp the engine can produce at rated RPM. At RPMs below this
level the prop does not absorb as much power as the engine could produce.
Properly loading the engine at lower RPMs would also solve the problem of a
large engine not having sufficient load at low rpms to fully warm up.
Most
engines have an optimum specific fuel consumption considerably below their max
rated RPMs. The new Vovlo D3 has its most economic specific fuel
consumption in the 2500 rpm range. The Nissan transmission is used in 300 hp
vehicles and gets better mileage than a manual transmission version. It has
been in service a number of years now and seems both reliable and efficient.
I looked at controllable pitch propellers but they lose efficiency due to the
hub size and are quite a compromise in the smaller diameters. I also thought
of a two speed gear that used high gear for lower rpms and low speed for the
highest rpms but the standard available items did not have appropriate
ratios.
Envision a single 'speed' lever that integrated prop, engine and
transmission characteristics and as you pushed it forward it determined what
ratio to set the transmission to and what rpm to set the engine at. With
today's electronic controls this seems like a relatively trouble free way to
achieve the maximum economy and performance. From the 'back of the envelope'
calculations I have done it looks to me there is a 5-7% economy improvement
possible and a significant decrease in engine noise and wear with the
same propeller thrust (equates roughly to boat speed) available at 500-700
rpms less than a traditional fixed pitch single speed prop.
Give it some
thought
Gary Hagstrom
building CRACKERJACK, a Maine Cat P-47
Iron River,
Wisconsin
Speaking of alternatives how about all electric
http://www.teslamotors.com/performance/perf_specs.php
Obviously you would need a generator and strong battery capability, but 288
HP and 100% torque at all levels of power.
Also prop shaft placement could be greatly enhanced due to smaller motor
size.
Lots of ideas, probably the wrong economy for real production
experimentation.
Last idea, what if you added a variable pitched prop to the variable
transmission, Wow you could use a fuel flow meter and really trim out any
condition
Jim Meader
On 4/4/10 7:07 AM, "Gary Hagstrom" ghagstrom@yahoo.com wrote:
Brian,
If you guys are working on a new drive system as you described
consider including something like the Nissan continuously variable speed
automatic transmission in the design. You are aware of the typical
significant difference between the rpm and power producing/absorbing
characteristics of a diesel engine and the propeller. The prop is designed to
absorb the total hp the engine can produce at rated RPM. At RPMs below this
level the prop does not absorb as much power as the engine could produce.
Properly loading the engine at lower RPMs would also solve the problem of a
large engine not having sufficient load at low rpms to fully warm up.
Most
engines have an optimum specific fuel consumption considerably below their max
rated RPMs. The new Vovlo D3 has its most economic specific fuel
consumption in the 2500 rpm range. The Nissan transmission is used in 300 hp
vehicles and gets better mileage than a manual transmission version. It has
been in service a number of years now and seems both reliable and efficient.
I looked at controllable pitch propellers but they lose efficiency due to the
hub size and are quite a compromise in the smaller diameters. I also thought
of a two speed gear that used high gear for lower rpms and low speed for the
highest rpms but the standard available items did not have appropriate
ratios.
Envision a single 'speed' lever that integrated prop, engine and
transmission characteristics and as you pushed it forward it determined what
ratio to set the transmission to and what rpm to set the engine at. With
today's electronic controls this seems like a relatively trouble free way to
achieve the maximum economy and performance. From the 'back of the envelope'
calculations I have done it looks to me there is a 5-7% economy improvement
possible and a significant decrease in engine noise and wear with the
same propeller thrust (equates roughly to boat speed) available at 500-700
rpms less than a traditional fixed pitch single speed prop.
Give it some
thought
Gary Hagstrom
building CRACKERJACK, a Maine Cat P-47
Iron River,
Wisconsin
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No where near ready for prime time. Batteries and associated weight and cost
are not competitive in ac or dc vs. diesel propulsion, and with twin diesels
you have redundancy for getting home. In a car where you don't need to drive
more than 50 miles in maybe can make sense to some, but not to me. A much
better alternative would be to offer more diesel cars like Europe does. Modern
common rail diesels with electronic injectors can be run a lower loads much
more efficiently then old mechanical diesels.
----- Original Message -----
From: Jim Meadermailto:jim@rmtmail.com
To: Power Catamaran Listmailto:power-catamaran@lists.samurai.com
Sent: Sunday, April 04, 2010 1:13 PM
Subject: Re: [PCW] Catamaran Drive system Comments
Speaking of alternatives how about all electric
http://www.teslamotors.com/performance/perf_specs.php<http://www.teslamotor
s.com/performance/perf_specs.php>
Obviously you would need a generator and strong battery capability, but 288
HP and 100% torque at all levels of power.
Also prop shaft placement could be greatly enhanced due to smaller motor
size.
Lots of ideas, probably the wrong economy for real production
experimentation.
Last idea, what if you added a variable pitched prop to the variable
transmission, Wow you could use a fuel flow meter and really trim out any
condition
Jim Meader
On 4/4/10 7:07 AM, "Gary Hagstrom"
<ghagstrom@yahoo.commailto:ghagstrom@yahoo.com> wrote:
Brian,
If you guys are working on a new drive system as you described
consider including something like the Nissan continuously variable speed
automatic transmission in the design. You are aware of the typical
significant difference between the rpm and power producing/absorbing
characteristics of a diesel engine and the propeller. The prop is
designed to
absorb the total hp the engine can produce at rated RPM. At RPMs below
this
level the prop does not absorb as much power as the engine could produce.
Properly loading the engine at lower RPMs would also solve the problem of
a
large engine not having sufficient load at low rpms to fully warm up.
Most
engines have an optimum specific fuel consumption considerably below their
max
rated RPMs. The new Vovlo D3 has its most economic specific fuel
consumption in the 2500 rpm range. The Nissan transmission is used in 300
hp
vehicles and gets better mileage than a manual transmission version. It
has
been in service a number of years now and seems both reliable and
efficient.
I looked at controllable pitch propellers but they lose efficiency due to
the
hub size and are quite a compromise in the smaller diameters. I also
thought
of a two speed gear that used high gear for lower rpms and low speed for
the
highest rpms but the standard available items did not have appropriate
ratios.
Envision a single 'speed' lever that integrated prop, engine and
transmission characteristics and as you pushed it forward it determined
what
ratio to set the transmission to and what rpm to set the engine at. With
today's electronic controls this seems like a relatively trouble free way
to
achieve the maximum economy and performance. From the 'back of the
envelope'
calculations I have done it looks to me there is a 5-7% economy
improvement
possible and a significant decrease in engine noise and wear with the
same propeller thrust (equates roughly to boat speed) available at
500-700
rpms less than a traditional fixed pitch single speed prop.
Give it some
thought
Gary Hagstrom
building CRACKERJACK, a Maine Cat P-47
Iron River,
Wisconsin
ghagstrom@yahoo.commailto:ghagstrom@yahoo.com
Power-Catamaran Mailing List
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