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Fuel economy of heavy brush cutters (e.g. Stihl FS550, Husqvarna FX555)

Started by Lorenzotto, June 24, 2012, 12:33:26 PM

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Lorenzotto

Hi, I work with slash-and-burn farmers in the Congo who clear fields manually with their machetes. This is very hard labor. As part of an initiative to introduce mild forms of mechanization amongst subsistence farmers, through a rental/service model based on some basic tools, I'm thinking of trying to introduce brush cutters. But I'm not sure whether this would be economical.

Some numbers:

Working with the machete

  • -farmers hire other farmers to clear a field with a cutlass at a rate of 1000 fc (Congolese francs) to cut a strip measuring 5 x 25 meters (16.5ft x 82ft)
  • -this is the equivalent of 40,000 fc per hectare (US$43/ha) or 16,200 fc per acre (US$ 21.5/acre)
  • -typically, 10 people are hired to work during 2 days; most farmers offer them a cheap meal, so you'd have to add US$10/ha or US$5.7 per acre
  • -total cost thus is: US$ 53/ha or US$28/acre
  • -a typical fallow is 2 to 3 years old and contains brushes with stems measuring 5cm/2 inches in diameter or so, besides lighter brushes and weeds
I find very limited information on the fuel consumption of strong brush cutters, such as the Stihl FS550 or Husqvarna FX555 (I think these strongest types are needed to do this work).

One source claims the utilization of 1 liter of fuel for 1000m² (i.e. the equivalent of 10 liters/ha or about 1 gallon / acre), which can be cleared in 1 hour, depending on the experience of the farmer. Fuel here costs 2000fc/liter (or US$2.13/liter) or 7600fc/gallon (or US$8/gallon).

Working with a heavy brush cutter
At the quoted fuel economy, using a brush cutter would be quite competitive, as it concerns the cost of fuel only:

  • -it would cost US$ 21 per hectare or US$8 per acre.
  • -now add labor at US$4 per day, and 10 hours work for the hectare (say 1.5 days), which would be a total of US$6. For the acre this would be 4.7 hours of work, say a bit less than a full day, let's keep it at US$3 for the wage. Note that these are "high" wages; the average yearly income for the subsistence farmer is less than US$100 a year
  • -total costs (fuel + labor) would be: US$27/ha or US$11/acre
  • -I'm not yet taking into account repairs and spares, nor lubrication oil

But in general, the brush cutter seems to be a good option.

However,  I doubt that these heavy brush cutters consume that little fuel or can be operated that smoothly (1000m²/h seems a lot). I don't know either how long they last in a heavy duty scenario (I read somewhere professional users buy a new one each year).

I'm looking for more precise numbers, because I want to introduce around 10 brush cutters as a first test. So I need to make sure it's economically viable.

In case the economics work out, I also see the potential use of brush cutters to harvest rice, maize, soy and sugarcane, - which is also done manually. Even though some studies show the brush cutter is only good for rice, soy and maize and less for sugarcane.

I would welcome some accurate data from serious people with experience with brush cutters. Thanks a lot.


beenthere

Welcome to the Forum

Your plan sounds interesting. Keep in mind that those with only experience using a machete may try to use the brush cutters in a similar way. ;)

If they have some mechanical skills and readily adapt, you may be on to something.
south central Wisconsin
It may be that my sole purpose in life is simply to serve as a warning to others

Lorenzotto

Quote from: beenthere on June 24, 2012, 12:47:15 PM
Welcome to the Forum

Your plan sounds interesting. Keep in mind that those with only experience using a machete may try to use the brush cutters in a similar way. ;)

If they have some mechanical skills and readily adapt, you may be on to something.

Thanks for the welcome. 

Indeed, training costs would surely have to be added. And this may be a high one time investment. Thanks already for this first important added expenditure.

Obviously, I made an error when saying a "rental" service. The tools would not be rented. We'd only offer a service, and people would hire our workers to come clear their field.

shinnlinger

I would think blades and how to sharpen them are another cost issue on top of parts and consumables
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

Ken

On our jobs the brush cutters will run from 50-75 minutes depending on the cutters methods.  We generally cut stems from 1-4".  Although the density varies widely from site to site the best cutters will average 5-7 tanks/acre.  In the absolute worst of conditions a good cutter should be able to clear an acre in 8 or 9 tanks.  Not sure what the tank size is but I suspect about 1 litre.  Although our work season is only 5-6 months a saw will last a couple of seasons without much trouble. 

Blades need to be kept sharp to increase productivity and lessen the strain on both worker and saw.  A light filing at the end of every tank will increase productivity.  Other than that maintenance on brush saws is pretty minimal although if they are used like an axe the repair bill will add up quickly. 

I am kind of partial to the Stihls but others who use Husky swear by them.  I suspect that once you introduce those saws the machete will soon be largely misplaced. 

Cheers
Ken
Lots of toys for working in the bush

shinnlinger

I suspect if one is good at sharpening a machete, they can probably handle a brush blade,(how are the rocks there, nonexistent due to centuries of farming?) but I think you also need to consider safety equipment.  Steel toed boots would be ideal but at least closed toe shoes, heavy pants, gloves and eye and ear protection.  Maybe chainsaw   helmets to go with each saw?
Shinnlinger
Woodshop teacher, pasture raised chicken farmer
34 horse kubota L-2850, Turner Band Mill, '84 F-600,
living in self-built/milled timberframe home

florida

I'd be surprised if the Congolese workers thought it was hard work although no doubt would be to most of us. We had a company come in with 10 laborers  to  clear 2 sections of swampy land of invasive Melaleuca trees with nothing but machetes. It was all hand work, cut and spray both cuts or ring the larger tress and spray. This was during the summer with temps in the mid nineties and humidity at 100%. I asked the foreman how he got guys to do the work and he told me they all thought it was easy.
General contractor and carpenter for 50 years.
Retired now!

Lorenzotto

Quote from: Ken on June 24, 2012, 06:01:09 PM
On our jobs the brush cutters will run from 50-75 minutes depending on the cutters methods.  We generally cut stems from 1-4".  Although the density varies widely from site to site the best cutters will average 5-7 tanks/acre.  In the absolute worst of conditions a good cutter should be able to clear an acre in 8 or 9 tanks.  Not sure what the tank size is but I suspect about 1 litre.  Although our work season is only 5-6 months a saw will last a couple of seasons without much trouble. 

Blades need to be kept sharp to increase productivity and lessen the strain on both worker and saw.  A light filing at the end of every tank will increase productivity.  Other than that maintenance on brush saws is pretty minimal although if they are used like an axe the repair bill will add up quickly. 

I am kind of partial to the Stihls but others who use Husky swear by them.  I suspect that once you introduce those saws the machete will soon be largely misplaced. 

Cheers
Ken

Hey Ken, thanks, these are useful data and pieces of advice.

There's a small difficulty in doing the calculation in that the fuel tank of the most powerful Stihl only contains 0.76 liters whereas that of the most powerful Husqvarna contains 1.1 liters.

In any case, if we take the worst situation of a Husqvarna needing 9 tanks / acre, this equates to 24.5 liters per hectare, or around US$52 in fuel per hectare. You'd have to add US$6 for labor = US$58 / hectare. Doing it with a machete: US$53/ha.

So in this case, the brush cutter loses its competitiveness against the machete...

Lorenzotto

Quote from: shinnlinger on June 24, 2012, 08:43:49 PM
I suspect if one is good at sharpening a machete, they can probably handle a brush blade,(how are the rocks there, nonexistent due to centuries of farming?) but I think you also need to consider safety equipment.  Steel toed boots would be ideal but at least closed toe shoes, heavy pants, gloves and eye and ear protection.  Maybe chainsaw   helmets to go with each saw?
Hi Shinnlinger, true, rocks aren't a problem (there's not so much as a pebble), but nobody wears shoes, only slippers. So we'd have to invest in good protective gear.

Lorenzotto

Quote from: florida on June 24, 2012, 10:09:16 PM
I'd be surprised if the Congolese workers thought it was hard work although no doubt would be to most of us. We had a company come in with 10 laborers  to  clear 2 sections of swampy land of invasive Melaleuca trees. It was all hand work, cut and spray both cuts or ring the larger tress and spray. This was during the summer with temps in the mid nineties and humidity at 100%. I asked the foreman how he got guys to do the work and he told me they all thought it was easy.
Well, they themselves report clearing fields as the single most exhausting farming duty. It's also the only job on which the better off farmers are willing to spend some money to hire workers. I've worked with many on the field, in the nasty sun and humid environment, and I see the suffering.

But comparatively speaking, you're certainly right: these people do work that most of us could not support for a minute. Women carry 50kg bags of manioc every day, over distances of 10km... Ask a girl in the US or the EU to do this...

westyswoods

I believe Ken gave a quite accurate assessment of the brush cutters. I have owned a Stihl 550 for several years and love it. They are a tool which most in this country would find very hard work. It will take out two inch brush with no difficulty.

The one big downside with it is, I have yet to find any commercial blades that are not junk. They just don't hold an edge.  My solution is to find good used 10 inch circular saw blades. The arbor for the  Stihl is an odd size so I bore out the used blades and use them. Absolutely no comparison as to how well they cut and long they last. I also fabricated a heavy duty retaining ring for the shaft on the Stihl. The original stamped ones are junk if used hard. Neither one of the above suggestions are costly or difficult.

I love the 550 seems to be very durable although have not ran to the extent you plan or Ken has.

They are costly and purchasing ten seems to be quite a leap. Why not start with two and keep close records to compare. Seems as though you are an individual who does their homework.

Welcome to the forum and have a great day.

Westy
Stay Safe and Be Healthy
Westy

westyswoods

Not to make light of safety equipment although I bet there is no OSHA in the Congo. Just a thought.

Westy
Stay Safe and Be Healthy
Westy

Lorenzotto

Quote from: westyswoods on June 25, 2012, 07:00:17 AM
They are costly and purchasing ten seems to be quite a leap. Why not start with two and keep close records to compare. Seems as though you are an individual who does their homework.

Welcome to the forum and have a great day.

Westy

Thanks, Westy, for the advice.

The reason why we'd prefer to go with 10 is to have some representative data. Using 2 can already yield good data, but with 10 you have a more accurate picture of the economics, the durability of the machines, handling problems, and demand.

Remember that the fields and farmers with who we'll be using this are quite diverse. So for each context we'd like to see some data.

We'll be using the cutters for 3 tasks:

1. clearing fields
2. weeding
3. harvesting crops

We're also studying whether it would be better to be going with 2 categories: a lighter (1.5kw) and a heavier (3kw) type of brushcutter. 5 pieces each. 5 sites.

In any case, the market for such a machine is truly enormous. Around 5 million farmers in Congo work on the forest frontier, in fields and fallows that require them to clear bush every 6 months.

rmack

I believe mine is an fs550, it's a 4 stroke, so very economical to run... but you still have to mix fuel.
I use a regular circular brush saw blade on it, sharpen at each fuel up.
the foundation for a successful life is being able to recognize what to least expect the most... (anonymous)

Welder Bob
2012 LT40HDSD35 Yanmar Diesel Triple
1972 Patrick AR-5
Massey Ferguson GC2410TLB Diesel Triple
Belsaw Boat Anchor

Lorenzotto

Quote from: rmack on June 29, 2012, 03:13:02 PM
I believe mine is an fs550, it's a 4 stroke, so very economical to run... but you still have to mix fuel.
I use a regular circular brush saw blade on it, sharpen at each fuel up.

Hi Rmack, thanks for your input. Do you have any idea how many acres you work on a full tank (I know this depends on the type of bush, but still, a description with estimate would come in very handy for me). Thanks in advance.

DouginUtah


Quote from: rmack on June 29, 2012, 03:13:02 PM
... it's a 4 stroke, so very economical to run... but you still have to mix fuel.

???  If it is a 4-stroke why do you still have to mix fuel?

-Doug
When you hang around with good people, good things happen. -Darrell Waltrip

There is no need to say 'unleaded regular gas'. It's all unleaded. Just say 'regular gas'. It's not the 70s anymore. (At least that's what my wife tells me.)

---

rmack

Quote from: DouginUtah on June 29, 2012, 03:29:37 PM

Quote from: rmack on June 29, 2012, 03:13:02 PM
... it's a 4 stroke, so very economical to run... but you still have to mix fuel.

???  If it is a 4-stroke why do you still have to mix fuel?

Don't know. That's what the still dealer told me when I bought it... do know it runs quite a while on a tank. Had it 3 years now.

Far as how many acres it would clear on a tank, I don't know... the tank is quite small, but I guess being a 4 stroke makes it quite a but more fuel efficient than a 2 stroke like a chainsaw engine.
the foundation for a successful life is being able to recognize what to least expect the most... (anonymous)

Welder Bob
2012 LT40HDSD35 Yanmar Diesel Triple
1972 Patrick AR-5
Massey Ferguson GC2410TLB Diesel Triple
Belsaw Boat Anchor

westyswoods

I must have missed something along the way. Four stroke with mixed fuel and a 550 some one please enlighten me.
Stay Safe and Be Healthy
Westy

Maine372

it operates of 4 strokes, but it doesnt have an oil resivoir like an automotive motor. it still requires the oil to be mixed with the gas to operate.

you would have to ask a stihl tech for more info.

Lorenzotto

Yes, these bizarre new motors by Stihl exist: they combine some principles of the 2-stroke with the 4-stroke engine. They call it the "four-mix" technology.

I'm not sure whether they've really marketed it in large numbers, because their news release about the technology is no longer available. A cache reveals it, though:

http://webcache.googleusercontent.com/search?q=cache:JhZ9H2-i3pAJ:www.stihlusa.com/whatsnew/news_fourmix.html+stihl+new+engine+two-stroke+four-stroke&cd=1&hl=en&ct=clnk

Ianab

Stihl's  NZ page has a write up on the 4-mix and how it works.

http://www.stihl.co.nz/4-mix-engine-lightweight-and-with-good-lugging-power.aspx

Seems the trick is they bypass a bit of the fuel/oil mix out of the inlet manifold and into the rest of the engine to lubricate the valve train and crankcase.

Idea is you get the fuel economy, low emissions and torque of the 4-stroke, without the hassle of a sumps and oil pump etc and it will still run in any position.

The larger brushcutters like the FS550 are still conventional 2 strokes, but most of the smaller units are the new 4-mix type.

Ian
Weekend warrior, Peterson JP test pilot, Dolmar 7900 and Stihl MS310 saws and  the usual collection of power tools :)

SwampDonkey

I think your workers will be much more productive with the brush saw and they don't have to bend over all day. This assumes the saw is in good working order and sharp blades. I believe there is also a big difference between actual clearing and spacing. If your mowing the stems down, the trees drop quicker than dealing with hangups in spaced trees. So your production is going to go up a far bit more on clearing openings.

I've been thinning a few years as well and have a FS550. Some years I cut 100 acres, some maybe 60 because I do a lot of marking out as well. This one I have now I bought in 2007. I put in new crank bearings, seals, and carb. kit in 2010.

Make sure you clean the air filter daily, or you'll loose power. Also put a courser spark screen in the muffler or that will clog up to and fast. If not you'll be carrying around a gutless machine all day.
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

Ken

Although I have already posted here I have some new info.  There is one new Stihl 560 on my crew this year.  I spoke to the operator today and he says he is getting nearly 2 hours/tank.  That is considerably better mileage than the 550's and the tank is only slightly larger.  He also claims that the 560 has much more power than the 550 he used to run. 

Lorenzotto, although you are using fuel consumption as a defining criteria in your determination I suspect that the amount of acreage/unit of time that can be done with a clearing saw versus a machete is no comparison.

Cheers
Ken
Lots of toys for working in the bush

SwampDonkey

I can get about 2 hours on my 550 in light thinning. But in thick red spruce, about 50 minutes. One hardwood block we were on, I cut a path in behind some residual to get to the block and then proceeded to cut. I was in there 2 hours and then walked out to get the gas jug and tool bag on the road. It was only 50 meters of trail to the road. Last year I was on plantation and burned 4 tanks a day to cut about 2 acres a day. On another light block, I cut 1 ha every 5 tanks. The biggest problem is having to walk so much to get the gas jug. :D
"No amount of belief makes something a fact." James Randi

1 Thessalonians 5:21

2020 Polaris Ranger 570 to forward firewood, Husqvarna 555 XT Pro, Stihl FS560 clearing saw and continuously thinning my ground, on the side. Grow them trees. (((o)))

Lorenzotto

Thanks all for your great input. This is what's so nice about small online communities: no spam or useless comments...

Before I reply, allow me to show you some vids and pics of a typical field that would have to be cleared::

I have uploaded some videos on Youtube, straight out of the Congo, and "exclusively" because of this topic  ;):

Young farmers cutting a fallow with 9.6 tons of fresh biomass / hectare, with the machete:

http://www.youtube.com/watch?v=W1uRZbuHMBs&feature=youtu.be

http://www.youtube.com/watch?v=3Mk13_XEmCo&feature=youtu.be

This one is good, right at the end you see how the farmer struggles with a tiny palm tree. Anyone who has worked with a machete knows that it gets stuck when you try to cut a woody but moist piece of biomass. A brush-cutter would cut this in a second:
http://www.youtube.com/watch?v=NjPmfoJMAko&feature=youtu.be

A general overview of the situation at the forest frontier - primary forest, secondary forest, lonely trees, fallow:

http://www.youtube.com/watch?v=VCELDpcj6pI&feature=youtu.be


Some pics:

First picture shows a field that has been cut, and is now being burned - you can see some of the types of brush to be cut:


PHOTOS MUST BE IN YOUR FORESTRY FORUM GALLERY PLEASE READ RULES AND REPLACE

Second picture shows a very young fallow (6 months); almost no woody brushes - we've done some measuring on the amount of biomass per hectare (in the case of 6-month fallows, the average is 96kg/100m² or 9.6 tons/ha):

PHOTOS MUST BE IN YOUR FORESTRY FORUM GALLERY PLEASE READ RULES AND REPLACE

Same fallow:


PHOTOS MUST BE IN YOUR FORESTRY FORUM GALLERY PLEASE READ RULES AND REPLACE

Another young fallow shows dry biomass - so you see which chunks are woody; these pieces are not too thick:

PHOTOS MUST BE IN YOUR FORESTRY FORUM GALLERY PLEASE READ RULES AND REPLACE

Mind you, many farmers also clear 3-year old fallows, which have woody brush with stems that can already be 5 to 8cm thick (2 to 3 inches).

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