Diesel chain saw???

is there such a beast?? If not, is it possible to convert a gas one to bio-diesel?

Very good question! I am interested to hear replies to this as well.

Kate, I've long held a fascination for biodiesel. If you have a diesel engine, in theory, you ought to be able to convey it to bio, right? Well, there are so many biodiesel options, from fresh pressed, to filtered, used fryer oil, from fatty food joints, that biodiesel will likely be available, in some form or another, even when semis can't haul fuel to the gas stations. All you need, is a way to get the greasy stuff home & filtered - ok, that's a gross oversimplification, but. La!

Another great question!

To the best of my knowledge there are no diesel chainsaws, at least none that are remotely homeowner friendly.  They would potentially be very hard to start.  Diesel engines have much higher compression ratios than gasoline engines.  This high compression is part of what makes Diesel engines more efficient than gasoline engines.  Also, in order to accommodate that higher compression, Diesel engines are heavier and much more sturdy than a gasoline engine.

In the late 70s & early 80s I believe GM started making diesel variants of gasoline engines just by swapping out a few parts.  The result was engines that were completely shot, utterly destroyed after something like 30,000 miles.  The gas engines just could not hack the pounding.

I actually have an interest in small Diesel engines.  I tend to think that the world would be better off if it was powered with diesel instead of gas.  I occasionally look for things like amphibious atv’s and 4 wheelers that are powered with Diesel engines.  I actually talked to a couple of people in the industry and they told me that while Diesel is great, the engines are heavy and expensive.

Carla, I like the idea of a diesel chainsaw, I really do, but I think I saw from another post that you liked the idea of low vibrations in an electric chainsaw.  If this is the case, I doubt that you would like the vibrations you would get from a diesel chainsaw.  Perhaps there is a way you could incorporate some biodiesel fuel diluted into gasoline or maybe ethanol.  This seems at least plausible as it is possible to run a gasoline engine on diesel, but this is far from ideal.  The reverse is not true.  Even a tiny amount of gasoline in a Diesel engine will destroy the Diesel engine.

So in the end I am sad to say that a diesel chainsaw is an unlikely contraption.

Sorry,

Eric

Damn. Ok, so the answer to this then, might be a diesel generator, to charge the batteries for the electric chainsaw! Or, go solar, lol.

Carla Burke wrote:Damn. Ok, so the answer to this then, might be a diesel generator, to charge the batteries for the electric chainsaw! Or, go solar, lol.

A diesel chainsaw, if available, would be a monstrously heavy vibratey beast that would probably rip off an arm at startup...

Solar and cordless is the way to go for small saws and moderate workloads. Add a gas saw for big trees and heavy firewood production.. gas sucks, but for this no alternative is remotely competitive in my opinion.

There are these small diesel engines for quite a while.
They are expensive thogh even if they are made China( 500 dollars while on similar chinese motor 7Hp but 4 strokes gasoline ive paid 80 dollars new).
3 hp ,has a lot of uses ,to power generators,smal tiller machines ,water pumps,wood chippers.
For a chainsaw it wouldnt be good because this motor needs to work horizontally only while a 2stroke motor can work horizontally,vertically ,even upsidedown.

It's a rpm and power/acceleration thing too.
2 stroke gasoline engines rev right out really high which makes for a high speed chain.
Diesel engines especially naturally aspirated(non turbo) usually are maxed out at 2700-3000rpm Vs 2stroke at 10,000+rpm

A diesel powered chainsaw would be worthless in my opinion.

A chainsaw, no matter what size, make or style; has one purpose, which is to cut wood from point A to Point B. Now in doing that, there are two ways to get there:

1. Take a small chip, but make the chain speed so fast, that it makes a lot of small chips. This is the tactic Husqvarna uses and why their saws turn up at about 14,000 RPM. To get that their saws have only 1 piston ring so that there is less drag on the inside of the cylinder walls and they can get more speed out of a given cubic area.

2. Take a bigger chip, but make the chain speed a little slower so that the saw has more torque to hog through the wood. This is the direction Stihl takes for its saws, but they have 2 piston rings so they can scavenge that explosion a little better, and get more torque.

A diesel powered chainsaw would be pretty heavy to survive the double compression ratio of a gasoline chainsaw, and turn really slow in comparison. Now a person could file the rakers completely off, and make a huge chip so that it could still cut from point a to point b fairly quickly, but there would not be much net gain.

A diesel is generally more efficient in fuel economy, but it would be hard pressed to get the efficiencies chainsaws have today. Now that chainsaws are fuel injected, they sip fuel. I mean sip fuel. Compared to the saw I bought in 2016 to the saw I bought in 2017, it is night and day. And the saw companies did that for pollution reasons, because they no longer run too rich, or too lean, because they always run at ideal settings...no matter the temperature outside, no matter how plugged the air filter is, no matter what elevation you are at...they just operate at peak efficiency.

Carla,

A diesel generator is definitely a viable option for your setup.  Off hand, the smallest one I know about from a reliable manufacturer is a 5k diesel generator by Generac.  This is just about perfectly sized for a home and positively sips the fuel.  It has a 12 gallon tank with a whopping 32 hour run time!  But be prepared to pony up for this awesome generator, it is a couple thousand dollars!  Ouch!

If you really want to go off grid and have reliable backup for dark days, my personal thoughts are that a diesel generator is the perfect match.  I don’t specifically know if the Generac model I mentioned is biodiesel compatible, but an increasingly large number of engines are compatible.  The main compatibility issue is that biodiesel is a better solvent than petroleum diesel (diesel #2).  A lot of Diesel engines are being modified to biodiesel compatibility simply by changing out rubber valves and seals for new ones made of a non-soluble rubber.  It’s really a pretty simple operation to make a Diesel engine biodiesel compatible.

Diesel generators shine in another respect that actually pertains to your potential usage.  Correct me if I am wrong, but one of the primary applications in your situation would be to change batteries when your solar panels can’t.  Is this basically correct?  If so, you could potentially be changing several batteries of various types (regular solar backup batteries, batteries for tools, etc).  Further, I am assuming that you still want household electricity while you are charging.  Charging all these batteries all at once and providing household electricity will likely require a lot of current as measured in amps.  When I run my Generac 5k gas generator under heavy load, it clearly strains.  I tested this by hooking up the generator to my house (I have a special setup for this) and turned on all my lights, TV’s computers, etc, I was running under half a full load.  Then I turned on the microwave and WHAM, the amperage draw roughly doubled and the generator audibly struggled to keep up.  I would expect the diesel generator to do very well under heavy load.  I am sure that my generator doubled or tripled or even more than tripled it’s f consumption when I turned on the heavy load.  I expect a diesel to behave much better under heavy load.

Carla, if you really want an off grid option but are put off by the cost of diesel, there is the wood gas option.  You would have to build a wood gasifier (it shares some principles of a RMH) and have a way to attach it to the generator.  If you have plenty of scrap wood on your property (think sticks, fallen branches, etc), then a gasifier may be a viable option for you, but if you really want information on that approach, I will save it for another post.

Carla, I hope this helps,  I think diesel is a great option, but they don’t come cheap.

Eric

I use an electric chainsaw run by my off grid batteries. You could run an electric chainsaw from a diesel gene.

I am trying to imagine what a diesel chainsaw would be like and about the only application I can think of that might approximate would be the original chainsaws.

The first chainsaws were huge, monstrous beasts that were two-man operated machines.  The bar was about 10-12 FEET long and required a man at either end.  They weighed between 80-100 pounds.  They cumbersome and dangerous.  One of the main problems was that the cutters on the chain were based on saw teeth from a handsaw.  They were not terribly efficient at getting the wood out.  Worse, being a sturdy chain, the chains were fairly thick, requiring a thick tooth.  In woodwork this is known as the kerf.  A thin kerf is always desirable.  It takes less work to cut and less wood is wasted.

The revolution that changed chainsaws forever came from Adolphus Stihl (Stihl chainsaws).  He made the astute observation that wood boring beetles dig through wood and leave behind little curls of wood shavings and not sawdust.  He developed a chain cutter that worked like s beetle, taking short slices that were then excavated and thrown out.  This slicing operation was vastly more efficient than the previous method and therefore required much less energy, and could use a smaller, lighter engine that could be used by a single operator.  The modern chainsaw was born.

Maybe one of those huge early chainsaws (or their even earlier cousins, a gas powered reciprocating saw, also operated by two people) would have been conducive to a Diesel engine.  They certainly could have used all that torque, but the weight might have been prohibitive.  At any rate, a modern diesel chainsaw would be extremely heavy, noisy, vibrate terribly, and might actually be dangerous at low RPMs as diesels have a lot of torque at fairly low RPMs.

Eric

Hi Carla;  Thought I would throw my 2 cents worth in.
Sadly I agree with the majority... Diesel is not viable for a chain saw.
Now lets talk about genset's.  Beware low cost diesel generators ...  They are now building them to run at 3600 rpm!!! Are they crazy?  Loud, stinky and I promise they will not last!  A good diesel runs at 1800 rpm and will cost minimum several thousand dollars, really more like $ 7000.00 !!!

There is another option with gasoline gensets. Buy only the new Inverter gensets ,  They are super quiet , run at reduced rpm's, will outperform any standard genset of the same output.  Then  hook it up to your large home propane tank... no pouring gasoline...  depending on your tank size it lasts all winter.
Yes you do need to buy a conversion kit for the propane  But propane burns much cleaner than gas, no choke required, starts at 20 below zero no issues, the motor oil does not need constant changing.
It's really a win win... nothing sucks more than trooping out in the cold and snow to pour gas on your foot ... oops .. meant  that to go in the genset...
Oh and if your handy with wiring they can be made to be remote start and stop !!!  Sitting in your easy chair to start and stop your genny is one of the finer things in life.

diesel would work better for a stationary saw like a band sawmill or a big circular saw cutoff saw like the ones that run off a tractor belt pulley.
I don't know where travis got the information about one and two piston rings and how it relates to friction drag. In 4 years of two cycle engine repair school I never heard such logic.

the top aftermarket pistons for husky saws have 2 rings

here's an example
https://www.baileysonline.com/meteor-piston-assembly-44mm-for-husqvarna-550-xp-chainsaws-replaces-577-04-70-02-mpa-pc2584.html

The first thing that comes to my mind is an old Ottawa log saw.  Not a chain saw, but will cut logs well and can be converted to a slow running diesel.

I found 2 hatz 3 hp diesels at a sale for $300. We use one of them to power a GM 10SI one wire alternator for a backup generator for the barn.  It is hooked to the battery bank that the windmill and solar panels are hooked to. It is set up with 2 tanks, 1 for diesel and 1 for bio.  We start it and stop it on diesel and use the bio for generation time.  The bio fuel is extremely hydroscopic so it will gel easily if let in a tank vented to air for a couple days.  So we use 2 caps for the bio tank one that is glued shut so when we are not using it the air can’t get in.  I think this could be put on a small portable trailer or even a cart to run an electric chain saw.

I sure wish we could make tiny diesels.  I can think of hundreds of applications.  In my studies there are a few design flaws that engineering hasn’t overcome, because of the size of the fuel particles. The diesels that are small enough to run a chainsaw usually are quite temperamental and need their compression changed wile worming up.  Most will need a squirt of either to get them started. A diesel uses heat from compression to fire. The other problem I have had running tiny diesels is the tiny fuel pumps and injectors are extreme precision machined tiny parts that wear out quick.  They will literally be destroyed from a particle smaller than a hair.

Carla Burke wrote:Damn. Ok, so the answer to this then, might be a diesel generator, to charge the batteries for the electric chainsaw! Or, go solar, lol.

Or just buy a regular gasoline chainsaw.

If you just buy a gasoline chainsaw that matches the work you are doing, it would be by far the most efficient means. My chainsaw is on the larger size, because I am a professional logger, and it is only 5 horsepower. The size chainsaw a homeowner would need is probably in the 4 HP range.

You probably are not going to find a generator that is under 6 HP, so that means the generator is going to be 1/3 bigger than you need, and consume at least five times the fuel. One has to keep in mind too, that with each conversion you will have losses. So from gasoline engine to making electricity for the generator there is a power loss, and then from the conversion of electricity to make the chainsaw turn there is loss, so twice the conversion losses over that of an gasoline powered chainsaw; that is hardly efficient.

As for fuel consumption, a modern chainsaw is pretty efficient. The engine is directly coupled to the chain directly, so the speed of the engine, and the fuel consumption of that engine, is directly proportional to the work it is doing. I cut professionally, and do not have a small saw, but even using a big chainsaw, all day, cutting 10 cord of wood, I average 1/4 of a gallon of fuel per day. That is really nothing. A generator/electric chainsaw set-up is going to cost you 5 times as much, because the generator is always running; you cannot shut it off like a gasoline chainsaw because the switch to do so is right on the saw.

Now how much do you value your back? Again, I have a big chainsaw, and it is 14 pounds. A homeowner sized saw is probably in the 8 pound range, or the equivalent of a newborn infant. Which would you rather drag around, an 8 pound infant-equivalent everywhere you go, or a 6 pound electric chainsaw everywhere you go, but then a 45 pound generator that needs to be shuffled in and out of the shed to get it within extension cord length of where you are cutting?

I would just buy an appropriate sized gasoline chainsaw, buy a gallon of gas, mix in a little two stroke oil, and use the fry oil you would use to make biodiesel, and dump that in the bar and chain oil tank. You would spend less money, use less fuel, lug a lot less things around, and get more cutting done.

If Katie can tote a chainsaw around, then surely you can! (LOL)

Nope. I'm much older than Katie, and disabled. I do have smarts, though, and wouldn't likely be carrying the generator around, but would have someone else mount it  on/ in something with wheels, so it could be moved, mechanically - or would leave it in place, to use for charging/running other things, as well, and only move the chainsaw.

bruce Fine wrote: I don't know where travis got the information about one and two piston rings and how it relates to friction drag. In 4 years of two cycle engine repair school I never heard such logic.

Inside an engine you have a piston moving inside a cylinder. The gap between the piston and cylinder is made up with a ring that goes around a grove...or two grooves...in the piston. If you only have (1) piston ring, there is going to be some drag along the cylinder walls. If you have (2) rings, you are naturally going to have twice as much drag along those cylinder walls.

But here is where power comes into place.

In order to get the ring on a piston, there is a gap between the ring ends, and a little compression gets lost down this gap which is called blow-by. An engine with one ring is going to have twice as much blow-by as an engine that has two rings because there is twice as much contact.

The twice as much drag along the cylinder wall slows the piston up, BUT when a piston is moving slower in the engine, it has more TIME to burn the gas and air mixture. Because of that added time, the engine develops more torque. Clessie Cummins realized this phenomenon, and designed a new diesel engine of the day that utilized this. This is the reason why Cummins Diesels have a totally different sound than that of Caterpillar or Detroit.

Myself, most of my experience has been with 2 stroke diesel gen-sets, but some 4 strokes too.

Eric Hanson wrote:
The revolution that changed chainsaws forever came from Adolphus Stihl (Stihl chainsaws).  He made the astute observation that wood boring beetles dig through wood and leave behind little curls of wood shavings and not sawdust.  He developed a chain cutter that worked like s beetle, taking short slices that were then excavated and thrown out.  This slicing operation was vastly more efficient than the previous method and therefore required much less energy, and could use a smaller, lighter engine that could be used by a single operator.  The modern chainsaw was born.

Biomimicry for the win!!

I think a diesel chainsaw is a solution in search of a problem.
I have to say, I really like my battery chainsaw.
The cost was comparable to my gas saw, and the flexibility of using those same batteries for other tools including portable lighting is nice.

The army had some diesel chainsaws, the raket and janseret I think. So it is a possibility, but another possibility is converting a gas chainsaw to run on methanol. Since methanol is a feedstock for biodiesel you'd likely already have some or the means to make some, you may not get the power or efficiency as biodiesel but you'd be self-sufficient if you make it yourself.