Whats your best guess?

[quinnf]

The conclusions section of a technical brochure comparing the power transmission efficiency of belts in ag applications  http://www.cptbelts.com/pdf/misc/energy_loss_and_belt_efficiency.pdf says:


Median efficiency of the surveyed industrial and agricultural
belt types and constructions is 96 per cent. Within
rated and application power levels, efficiency ranges from
90 to 99 per cent depending on belt type, construction, and
application parameters. Both median and range agree with
historical data.The major portion of belt energy loss during power transmission
is attributed to parasitic bending hysteresis and
sliding friction. The cogged construction which minimizes
the hysteretic component of parasitic loss yields the
greatest efficiency in each industrial test. The condition of
classical B-section cogged belts operating on 3.4 inch
diameters at rated power levels demonstrated the largest
energy savings, ranging from 3 to 6 per cent.

[cognos]

Well, I suppose 200 watts is significant to some. It's certainly more more significant as a 6% loss than 2%.

I was just pointing out that the difference in efficiency in flywheel's test was low, lower than even I - who has no real idea - expected. And possibly within tolerances of the test. Put on a new belt, change the belt tension, change the pulley, vary the rpm slightly, blow on the resistive heater load, etc...

So I could "win" the Big Prize for the first correct answer...   Hence the "smiley faces" in my post.

I guess I'd like to see a test with measured fuel consumption, constant standard load, same gennie rpm, same engine and generator. Then we'd really see how much energy is consumed by that belt setup. But if it's only 2%, then it's not really worth doing. But if someone wants to send me a free 6.5HP Changfa to hook up to my old (dead engine) Kohler 6.5HP/3500 Watt generator setup, I'd be willing to do the tests, I've got the instrumentation and the "volunteer" manpower...  

[mobile_bob]

two hundred watts is only significant if you are on a hunt for every possible loss in an effort to see
what is possible and at what cost, as opposed to what is nearly impossible or too costly.

your mention of blowing on the heater is a valid one, it is amazing to see the effects of a breeze blowing through
the shop while running one test and then retest with one door shut to cut off that breeze.

all this anal retentive behaviour while hard for most to understand, is something you have to do in order to get
solid fact based info and data. and it has to be repeatable or in my opinion the data/results or conclusions are flawed.

when i started on the process my assumption was the alternator at best might be 54% efficient as advertized by the
manufacture, and the st head was widely reported to be 80-85% efficient (anecdotal evidence) so on the face
of things it would seem fruitless to try and use an automotive alternator to drive an inverter to get clean power
without taking a huge hit in efficiency over just producing the power with the st head and either living with its less
than perfect waveform, shifting hz, etc. or take off on the path to improving the power quality of the st head.

i chose to fully explore the alternator route, and to determine whether i was making any progress i had to have
an accurate means of measurement, and being able to measure and capture down to as low as 60 watts was
something that i needed.  accepting 5% here, and 2% there, and magnify both in calculations meant that
sooner than later everything concluded based on not so good measurements was worthless.  Things like clamp on
meters shifting about  by a few tenths of an amp, or more depending on how the wire was centered in the clamp,
drafts (as alluded to) skew the load, ambeint temperatures, fuels used, how the damn fuel test tank sets of the scale
and how the hose coming off of it is supported, and on and on, all have some effect on test results.

so yes i get very anal about 200 watts

and when i found the GE kw/hr meter which is digital is good to 1/2 percent i thought, hmmm cool
so in one kwatt hour it can be off {+/- 5 watt hours) and add to that another +/- 10 watt hours
for screen update, the result for testing is i could be off as much as +/- 15 watt/hrs or more
after doing some research and finding out i can alter the head to read out in watt/hrs instead of kw/hrs
the accuracy improves dramatically to about +/- 3 watt hours. 

the move to the GE head dramatically improved my accuracy and perhaps more importantly my  repeatability
over any of 3 different clamp on meters i had been using, so at least that factor was resolved to a highly reliable
degree in my mind.

having a gram scale was the second major factor that works into the equation, without the gram scale determining
gr/kw/hr BSFC would be problematic, wherein measuring fuel by volume inserts another set of inaccuracies into all
the equations.

my next move is to get a gram scale that is digital and as accurate as the GE kw/hr meter.

bob g

[AdeV]

and it has to be repeatable or in my opinion the data/results or conclusions are flawed.

Amen to that!

In fact, it not only has to be repeatable; it has to be consistently repeatable even when someone else does the test [provided, naturally, they follow your setup and instructions to the letter].

In attempting to not go too far off-topic, I'll refrain from mentioning which "sciences" tend not to be so bothered about repeatability (coughglobalwarmingcough) or transparent methodology.

[flywheel]

Direct vs belt drive, and what I have learned.  When I first assembled this genset six years ago I thought v belt drive was a good choice.  Belts have been around for a long time, they are readily available and not expensive.  The belt I used is a banded belt - two belts in one with a common back.  They are also called commonback, banded or combo belts, instead of using two seperate matched belts why not just use one banded belt. Cost for this high quality belt was about $40. It is a heavy duty quality belt.

During belt testing under a heavy load there was some belt bouncing.  Belt needed to be very tight which can be hard on engine and head bearings.  The pulleys became very hot from friction and the flexing around the pulleys.  Very fine black particles like dust comes off the belt.  This heat buildup in the pulleys and belt is wasted energy.  Belts need periodic adjustment and replacement.  All v belts will have some slip or creep which is also a energy loss.  When the engine is hand cranked it is much harder to start with belts. The engine does have a starter but I usually just hand crank it.

Now lets look at a direct drive system.  The engine adapter hub and lovejoy coupler was supplied by
george B at www.utterpower.com  George is a very nice guy.  When this genset was  changed over to direct drive testing shows a higher output at a lower engine speed.  Hand cranking to start is much easier. Under a heavy load there is no heat buildup in the lovejoy coupler, not even warm.  No heavy side loading of engine or head bearings.  No black dust coming off the coupler. There are no adjustments once properly set up and alligned. The same rubber spider in the coupling is still in very good condition after six years.  It is also not used on a daily basis but only as needed.

My testing was not a highly controlled test,  it was good enough to determine that direct drive is a better choice for me.  I will be taking this genset apart after I have a replacement set up and operating.  If there is a lot of interest I may retest under highly controlled conditions. This would require me getting two same size metric v pulleys.  Serpentine belts are suppose to be more efficient than v belts. I would also like to obtain two like size serpentine pulleys to see how much more efficient than v belts they are. I will check into this to see what the cost may be.

[mobile_bob]

Flywheel:

i like the banded back belts if you have to run multiple V belts, there is about no other way to get a good match
these days.

my only question is why the dusting of the belt? this doesn't seem normal for the power capability of dual B belts
which should have a rating far above the power being transferred and factoring in the 1.4 derate for a single cylinder
diesel engine,,, iirc (i would have to dig out the belt engineering book, but i bet you did that to start with)

is it possible one or both pulleys are made for something other than a standard B groove? there is another V by some
other designation that escapes me just now that looks close but an A or B will not seat in properly, is it possible this is an
issue?

i also noted a dramatic change in my ability to hand crank my engine with a belt drive, i am useing what is called an AA belt
time 2, the belt section is basically hexagonal in cross section allowing it to drive off the bottom and the top and be used in
a serpentive drive over standard A or B pulleys. even with the fields disconnected to the twin alternators i cannot hand crank the
engine to start it.

After calculating the belt drag to be somewhere around 200 watts which equates to a bit over a quarter hp, i got to thinking
it is said that a healthy man can generate 1/2 hp (presumably with the stronger muscles of his legs) so i figure a tired, injured old
fart like me probably can't make a quarter hp using one arm for more than a several seconds at a time, certainly not long enough
to get past compression a time or two.

(edit: upon rereading this it occurs to me that the quarter hp i refer to is in addition to the power required to start the engine
without belts attached, which is probably a couple hundred watts by itself, making the total required over a half hp with the belts
installed.)

the most i have pulled off of my twin AA belts is approx 6kwatts, and the belts get up to about 140 degree's F at room ambient
temps of 60 degree's F. i noted no dusting of the belts but did note the pulleys get hot on the alternators running a bit more than
the 140 degree belt temps.

according to the engineering the twin AA drive will handle ~8kwatts continuously at room temps as installed in my application
taking into account the single cylinder diesel derate, wrap angles, alternator loads and other things the engineering requires one
to account for... in other words thats it 8kwatts is all it will take and return good life expectancy.

thats why i am somewhat set back that you have dusting with twin common back B belts i would think they would be good
for 12kwatts under your application parameters without dusting and without heavy sideloading from high tensions.

just trying to get my head around your results, and try to understand what is happening there.

as for direct drive, there is little doubt in my mind that it is anything other than the way to go for this application
the changfa likes 1800 and the ST head requires 1800, a match made in heaven. what could be simpler than a
direct drive coupler like the lovejoy or similar device?

sunday i will try to get some pictures of my drive system for comparison, it all depends on whether my back will let me
get up and move or not.  (next wednesday is the 3rd injection, oh boy!)

btw, nice report flywheel!

bob g

[Henry W]

Guys, very nice write-up's.

I believe if someone wants to run a belt setup on the S195's or larger running larger gen-heads from 10k and up they should look at an 8 or 10 groove serpentine setup. They will work very well as long as a heavy built idler system is built to take the abuse of large one cylinder diesels. Once the idler assembly was installed on my genset my problems went away. I believe the pulley size of 8 1/4" for both pulley's helps on my setup. More mass for the belt to grab onto. I get at most very little slippage. So little that when I stop the engine and put it on the compression stroke the lettering on the belt is at the same location before I started.

I could not get this to happen without the idler assembly. Another good thing is I can run much lower belt tension with this setup. I do not notice heat generated from the belt and pulley's so that must mean no or very little slippage is happening.

I think running a properly desgined serpentine setup will give you more efficency than a conventional V-belt setup.
But I believe direct drive is the more efficent way to drive gen-heads. The main reason why I went with a belt setup is space. I made a much narrower genset. The genset fits nicely in a corner of the garage. If I had more room I would of went with a direct drive system.

Henry

[veggie]

Henry,

Yep, the surpentine is more efficient than a V-Belt.
usually it's less noisy and can carry more HP / Belt width.
I think you're right about the 8 groove surpentine. The traditional inexpensive 6 groove version may be a bit light for the 12BHP+ that you are pulling under full load. (or the 16HP you are pulling in your secret tests    )

Veggie

[veggie]

... Or you can go to a different belt profile (other than the automotive style) that is meant for more power.

Jens

Good point. The 3V and 5V section industrial belts can pull a great deal of BHP relative to their cross sectional size.
We use a 3 banded 3V belt (looks about the same width as a standard "A" belt) to drive our screw compressors pulling 25 HP.
Very quiet also. The sheaves are easy to find, but getting someone to make a custom sheave to fit a specific engine flywheel might be a bit of a problem.

Veggie