Mechanical Efficiency

I have been looking all over the Internet to find comparisons of mechanical efficiency and haven't found anything that isn't covered in different units of measure that require multiple iterations of conversions.

Can anyone here compare the efficiency of:

A very long chain drive as used in a recumbent
A hydraulic drive system and
A electric motor

And perhaps there's something I missed?

expressed precisely :
I have been looking all over the Internet to find comparisons of mechanical
efficiency and haven't found anything that isn't covered in different units
of measure that require multiple iterations of conversions.

Can anyone here compare the efficiency of:

A very long chain drive as used in a recumbent
A hydraulic drive system and
A electric motor

And perhaps there's something I missed?

You start here comparing the efficiency of the transmission (chain or
hydraulic pmp/motor/tubing combination) with that of the drive
(e-motor).

Something with apples and pears. Please be more clear on this.

On 4/19/2017 3:23 PM, Martin Borsje wrote:
expressed precisely :
I have been looking all over the Internet to find comparisons of
mechanical efficiency and haven't found anything that isn't covered in
different units of measure that require multiple iterations of
conversions.

Can anyone here compare the efficiency of:

A very long chain drive as used in a recumbent
A hydraulic drive system and
A electric motor

And perhaps there's something I missed?

You start here comparing the efficiency of the transmission (chain or
hydraulic pmp/motor/tubing combination) with that of the drive (e-motor).

Something with apples and pears. Please be more clear on this.

As Martin says, the electric motor is the answer to "One of these things
is not like the others..."

But electric motors vary widely in efficiency. The trend, very
logically, is that big ones are made more efficient than tiny ones. My
guess (TM) would be approaching 95% for really huge ones, down to 70%
for tiny shaded pole motors driving timers, clocks, etc. I'd expect a
motor as used in a motorized bike to be around 80% efficient.

Roller chains are very efficient. Over 90% is not at all unusual, and
they can get into the high 90s under the right conditions.

Hydraulic drives typically consist of a pump, valves, hoses and a
hydraulic motor. This site gives roughly 85% for a fairly simple pump:
http://machinerylubrication.com/Read...rs-maintenance
A hydraulic motor of similar technology would be similar. And you'd
have losses in valves and piping. You'd need to compound all those
efficiencies to get the total. I'd guess overall efficiency of less than
70%.

--
- Frank Krygowski

On 4/19/2017 2:10 PM, wrote:
I have been looking all over the Internet to find comparisons of mechanical efficiency and haven't found anything that isn't covered in different units of measure that require multiple iterations of conversions.

Can anyone here compare the efficiency of:

A very long chain drive as used in a recumbent
A hydraulic drive system and
A electric motor

And perhaps there's something I missed?

Hydraulic wheel drive can work okay at low RPMs and where loss of drive
precision isn't important, but the fluid turbulence prevents them from
being much use at higher RPMs. ("higher" being, as fast as bicycle
wheels or car wheels typically turn)

Tall-wheel self-propelled crop sprayers have a hydraulic pump on the
transmission and hydraulic motors at the wheels:
https://www.youtube.com/watch?v=cvDVcFCp5fU
The ones for spraying corn (maize in Euro-land) are tall enough that you
can walk around underneath them without bending over. They are driven
across corn fields with the tires straddling between the planted rows.

On 4/19/2017 2:10 PM, wrote:
I have been looking all over the Internet to find comparisons of mechanical efficiency and haven't found anything that isn't covered in different units of measure that require multiple iterations of conversions.

Can anyone here compare the efficiency of:

A very long chain drive as used in a recumbent
A hydraulic drive system and
A electric motor

And perhaps there's something I missed?


I do not know but it sounds dauntingly complex.

One added factor is that a new chain drive is very efficient
but wear brings a lot of friction=heat loss. There's plenty
of data on that subject.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

Ok, I'll bite 8-)

wrote:
I have been looking all over the Internet to find comparisons of mechanical efficiency and haven't found anything that isn't covered in different units of measure that require multiple iterations of conversions.

Can anyone here compare the efficiency of:

A very long chain drive as used in a recumbent
Low-to-mid 90's %, assuming good alignment and lubriction.
Aluminum chain links seem like a good idea.

A hydraulic drive system and
Don't know, but hydrostatic drives tend to have seal friction
losses and hydrodynamic drives operate at higher speeds than
cyclists pedal.

A electric motor


How heavy do you want to make it? Power transfer is maximum at
50% efficiency, to make it more efficient the components must be
given higher power capacity, i.e., bigger. That's why bottle
dynamos are around 50% efficiency.


And perhaps there's something I missed?
On a bicycle the biggest issue seems to be weight. An aluminum
or titanium chain drive is probably the best match to requirements.

Putting on my Nomex suit...........

bob prohaska

On Wed, 19 Apr 2017 12:10:33 -0700 (PDT), wrote:

I have been looking all over the Internet to find comparisons of mechanical efficiency and haven't found anything that isn't covered in different units of measure that require multiple iterations of conversions.

Can anyone here compare the efficiency of:

A very long chain drive as used in a recumbent
A hydraulic drive system and
A electric motor

And perhaps there's something I missed?

I can't quantify it but I've known a number of people that had a
hydraulic drive in a sailing yacht. Every one hated it. I remember a
guy had sailed from Australia to Singapore and when I met him he was
industrially re-engining his 35 ft. boat to use a direct drive
(propeller shaft and gear box).

Due to hull design and shape installing an auxiliary motor is
difficult in some sail boats and a hydraulic pump on the engine and a
hydraulic motor driving the prop seems like a good idea. Until one
tries it. On the other hand an electrical drive seems to work great.
At least on a boat :-)

It might be considered that a chain drive probably has the lowest
losses of any drive system :-)

On Wednesday, April 19, 2017 at 7:52:24 PM UTC-7, John B Slocomb wrote:
On Wed, 19 Apr 2017 12:10:33 -0700 (PDT), wrote:

I have been looking all over the Internet to find comparisons of mechanical efficiency and haven't found anything that isn't covered in different units of measure that require multiple iterations of conversions.

Can anyone here compare the efficiency of:

A very long chain drive as used in a recumbent
A hydraulic drive system and
A electric motor

And perhaps there's something I missed?

I can't quantify it but I've known a number of people that had a
hydraulic drive in a sailing yacht. Every one hated it. I remember a
guy had sailed from Australia to Singapore and when I met him he was
industrially re-engining his 35 ft. boat to use a direct drive
(propeller shaft and gear box).

Due to hull design and shape installing an auxiliary motor is
difficult in some sail boats and a hydraulic pump on the engine and a
hydraulic motor driving the prop seems like a good idea. Until one
tries it. On the other hand an electrical drive seems to work great.
At least on a boat :-)

It might be considered that a chain drive probably has the lowest
losses of any drive system :-)

Thanks for everyone's input. While going through all of the literature I got the idea that with electric or hydraulic you couldn't really expect much more than a total of 60% at best but I wanted to make sure.

High speed recumbents have the problem of not being able to get high enough gears and end up having multiple large and small wheels to get pure wheel speed. The best I saw was an internally geared wheel that gave a 1:4 ratio but you can't buy those sorts of components and would have to build them yourself.

Straight cut gears are the most efficient losing only around 2-3%, chain drives in perfect condition are something like 90% but rapidly lose that unless fully enclosed and often serviced.

On 4/20/2017 10:20 AM, wrote:
On Wednesday, April 19, 2017 at 7:52:24 PM UTC-7, John B Slocomb wrote:
On Wed, 19 Apr 2017 12:10:33 -0700 (PDT), wrote:

I have been looking all over the Internet to find comparisons of mechanical efficiency and haven't found anything that isn't covered in different units of measure that require multiple iterations of conversions.

Can anyone here compare the efficiency of:

A very long chain drive as used in a recumbent
A hydraulic drive system and
A electric motor

And perhaps there's something I missed?

I can't quantify it but I've known a number of people that had a
hydraulic drive in a sailing yacht. Every one hated it. I remember a
guy had sailed from Australia to Singapore and when I met him he was
industrially re-engining his 35 ft. boat to use a direct drive
(propeller shaft and gear box).

Due to hull design and shape installing an auxiliary motor is
difficult in some sail boats and a hydraulic pump on the engine and a
hydraulic motor driving the prop seems like a good idea. Until one
tries it. On the other hand an electrical drive seems to work great.
At least on a boat :-)

It might be considered that a chain drive probably has the lowest
losses of any drive system :-)

Thanks for everyone's input. While going through all of the literature I got the idea that with electric or hydraulic you couldn't really expect much more than a total of 60% at best but I wanted to make sure.

High speed recumbents have the problem of not being able to get high enough gears and end up having multiple large and small wheels to get pure wheel speed. The best I saw was an internally geared wheel that gave a 1:4 ratio but you can't buy those sorts of components and would have to build them yourself.

Straight cut gears are the most efficient losing only around 2-3%, chain drives in perfect condition are something like 90% but rapidly lose that unless fully enclosed and often serviced.


But you already have a meat engine as cargo so any
additional energy source (electric) will increase total mass
and any degradation of efficiency in transfer (hydraulic)
will waste energy.

--
Andrew Muzi
www.yellowjersey.org/
Open every day since 1 April, 1971

On Wed, 19 Apr 2017 12:10:33 -0700 (PDT), wrote:

I have been looking all over the Internet to find comparisons of
mechanical efficiency and haven't found anything that isn't
covered in different units of measure that require multiple
iterations of conversions.

https://en.wikipedia.org/wiki/Bicycle_drivetrain_systems

I also couldn't find anything that is instantly useful. There's
probably a reason why nobody has made such a general study. My
guess(tm) is it's because it wouldn't apply to most useful situations,
power levels, rotational speeds, and other design limitations. A
realistic comparison would include a range of acceptable power
transmission levels, weight limits, and possibly some operational
considerations. On a bicycle, the book
"Bicycling Science"
by David Gordon Wilson
2nd and 3rd editions (they're somewhat different)
http://www.alibris.com/Bicycling-Science-David-Gordon-Wilson/book/17828968
https://books.google.com/books?id=0JJo6DlF9iMC
is a good reference of work for such surveys. The section on power
transmission includes Berg cable drives, toothed belt drives, drive
shafts, etc.

Can anyone here compare the efficiency of:

A very long chain drive as used in a recumbent

Might be something in he
http://www.cyclingpowerlab.com/drivetrainefficiency.aspx
http://www.bikeradar.com/us/news/article/friction-facts-measuring-drivetrain-efficiency-35694/

A hydraulic drive system and

The weight penalty of dragging a plumbing nightmare around might make
this a losing proposition even if it were 100% efficient.

A electric motor

I'm going to assume you're only interested in a human powered
transmition, not building a battery or wind powered bicycle or hybrid.

An electric generator and motor transmission is the mostly the product
of the generator and motor efficiencies, going from kinetic energy to
electric energy and then back to kinetic. A small (1-2HP) permanent
magnet electric generator is probably about 75% efficient while a
similar sized motor is about 70%. There are power/rpm curves for both
that can be used to determine the most efficient operating point, or
the efficiency at some particular power and RPM level. Using my
guess(tm) numbers, that's:
0.75 * 0.70 = 53% efficiency.
In other words, an all electric drive system sucks. On Pg 337 of the
"Bicycling Science" book, the author does a better job of estimating
the electrical system efficiency. He has the following in series:
70% - Pedals driving gears with short chain to generator.
98% - Generator
95% - Controller
80% - Motor driving short chain to wheel
Multiplying these together yields 52% efficiency.

There's also a short section on hydrostatic drives (as in earth
movers), which the author claims maxes out at 80% efficiency and is
therefor useless.

And perhaps there's something I missed?

Well, I would suggest you disclose what you are trying to accomplish
so that I don't need to guess(tm) so much. You also missed other
transmission systems:
1. Perforated metal tape instead of a chain
2. Cable (Snek) drive
3. Berg cable and plastic chain:
http://802.11junk.com/jeffl/pics/Berg/
4. Toothed rubber belt
5. Direct gear drive using lots of spur gears.
6. Drive Shaft
7. Direct drive (Penny Farthing)
8. Ratchet drive
9. Various eccentric gear drives (elliptical crank, reciprocating
pedals, rolling exercise machines, etc).
http://www.elliptigo.com
https://www.streetstrider.com
10. Rowing motion drive
https://rowingbike.com
11. Front wheel pedal drive with hub transmission.
12. Whatever else I forgot.

--
Jeff Liebermann
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558