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Sawdust From The Kerf
Volume 1
Issue 3
September 2002
Diesel Chain Saws
By George B. Blake

One day Mike and I were discussing topics for the newsletter. For some reason I can’t remember, the subject of Diesel Chain Saws came up. We both agreed that this would make a great newsletter that should be interesting to most who read it, for, it has been my experience that most people don’t know that Diesel Chain Saws exist.

When I tell people about Diesel Chain Saws, after the funny looks, I usually get the; “Yeah right”!! Once I convince people of the fact that diesels do exist, they usually form their opinions that these things must be huge monsters !! Trucks use them, as do trains, and look at the size of them! People also draw conclusions as to how they must have operated and how complicated they must have been.

In this letter I will try to give you some history of when the first Diesel Chain Saw was made, who made it, where it was made, and why it was made. I will talk a little about what made these saws work as well as their design. We will also look at some of the various models of diesels.

The history of the Diesel Chain Saw is a little fuzzy. I have obtained information from several sources, some which contradict each other, but have put together what I believe is the most accurate history available about these little known wonders.

I do not profess to be a Diesel Chain Saw authority. I am just an enthusiast that spent 20 years looking for and studying these elusive marvels.

I can assure you; Diesel Chain Saws do exist !!!

Where was the first diesel saw made ? It was in Oslo, Norway. Who invented such a thing ? A Norwegian named Rasmus Wiig.

Rasmus Wiig was a mine captain in the silver mines of a town in Norway called Kongsberg. Although he worked in the silver mines, Mr. Wiig was very much interested in forestry. In 1947 Mr. Wiig invented a steel jawed machine for felling trees. According to Professor Ivar Samset, this device was driven by a bicycle like mechanism and was actually quite effective. The problem was that he couldn’t control the direction the trees would fall!

In 1949, Mr. Wiig constructed his first power driven saw. He named this saw “Comet”. The Comet weighed in at 8 1/2 kilos, which was sensational at that time when you think of the weight of the other power saws that were around.

There was something extra special about the Comet! It had no spark plug. No ignition coil, no points, and no condenser!! It was a Diesel !!!

When one thinks of diesels one thinks of heavy engines with high pressure injection pumps. Not so with the Comet, which weighs in at a mere 8 ½ kilos. So, how did he do it? How did Mr. Wiig make this Comet run?

We all know that a diesel engine needs a heat source to get the engine started. Once the engine is started, the heat of combustion does the rest. Most modern diesel engines use electrically heated glow plugs. Well, Mr. Wiig did use a glow plug, but it wasn’t electrically heated. In the cylinder head of the engine is a heating tube, or plug called the “Tändror”. This is a steel plug which actually screws into the cylinder head. Heat this plug until it glows red, and you have a glow plug !! Mr. Wiig knew that moisture was the biggest enemy of the conventional ignition system and did not want anything electrical on this Comet. The very high cost of gasoline in Europe and Scandinavia was also of great concern.

Most all saws use a tubular handle bar system. Mr. Wiig made use of the tubular handle bar on the Comet. First he ensured that all ends of the handle bar were well sealed. Then he installed a “charging post valve” into the handle bar, similar to that of a charging port on an air conditioner system. Using a separate small canister and a connector hose, Mr. Wiig filled the tubular handle bar with propane gas.

Propane reservoir connected to filling valve in handlebar.

Also connected to the handle bar is a shut off valve connected to a tube that runs to the Tändror. Open the valve, light the burner at the end of the tube at the Tändror, and a mini propane torch heats the Tändror.

View of Tändror and propane fired heater.

When the Tändror begins to glow red, pull the rope and start the Comet !! Once the Comet is running, simply turn off the gas to the Tändror burner and you have a diesel in your hands which is running purely off of the heat of combustion !!

Mr. Wiig boasted about how dampness and moisture could not affect the operation of the Comet. In one advertisement, Mr. Wiig submerges a Comet into a barrel of water. After a few moments he pulls the Comet out of the barrel, lights the Tändror burner, and starts the saw !! Let me see you do that with any of today’s saws !!

This unique saw can run on diesel fuel, kerosene, and a gasoline / oil mix. It is a 2 cycle engine that uses an “injector” type of carburetion system.

The very first model Comet produced was the Model “A”. The tag on the starter door had the word “Comet”, and below that was the name of Mr. Wiigs small factory in Oslo, “ Norsk Sagbladd Fabrikk”, which translates into “ Norwegian Saw Blade Factory”.

Name Plate of "A"
model comet.

"A" model Comet
flywheel side.

"A" model Comet
sprocket side.

"A" model Comet
operator position.

The starter on the Comet was a simple notched pulley which you wound the rope around. The pulley was kept behind a spring loaded starter door which closed once the engine had started.

View of starter pulley
with spring loaded door.

Mr. Wiig once claimed that should the engine ever stall during operation, all one need do to re-start the engine is open the door and give the pulley a spin with your fingers !!!

It is unknown just how many model “A” Comets were made. Most say it numbers in the hundreds.

Although a very light and innovative saw, sales were not what Mr. Wiig had hoped for, so, he took his idea to neighboring Sweden. A company called “Como” M. T. Bjerke would now build the Comet in Sweden. I’m told this occurred in 1950. The Swedish version of the Comet was called model “B”. Swedish forestry historians tell me that production of the model “B” Comet is approximately 1,000 between 1950 through 1953.

"B" model Comet

Historians tell me that in 1953, the Comet was produced with an automatic rewind starter mechanism called “Magnapull”. This was model “S”. This would be the last model of the Comet and it was produced until sometime in 1954.

In 1954, Jonsereds became involved in the chainsaw industry and, in cooperation with “Como” M.T. Bjerke Company, produced the first Jonsereds chainsaw. This saw used the ideas of Mr. Wiig and his Comet, but was quite different in appearance. The very first model was called model “P”. The “P” stood for “Propane”.

The first Jonsereds saw sold on the market was called model “XA”. The “XA” was a propane heated diesel saw.

"XA" model Jonsereds
sprocket side

When the “XA” is in the sitting upright position, the cutting chain appears to be installed backwards. That’s because it is !! The upright position is not the position the saw is operated in. Once started, the saw is intended to be inverted, which places the chain in the proper direction !

There are two varieties of the “XA”. The “XA”, and the “XA-19”. Both are propane diesels. The differences are small, but can be noticed. The biggest difference is that the “XA” has a rounded edge fuel tank, whicle the “XA-19” had very squared edges of the fuel tank.

It is said that the “XA-19” is more rare than the “XA”.

I’ve been told that Jonsereds does not know the exact production numbers of the “XA” models, but believe it to be in the area of 2,000 units.

It is my understanding that the Jonsereds “XA” was never imported into the USA. A Diesel was, however sent here in a different form. The saw was a diesel, however, the Tändror was missing and was replaced with an electrically heated Glow Plug. An aluminum box was attached to the handle bars. In this box were two (2) “D” cell batteries. On the side of the box was a spring loaded push button. Push the button, heat the Glow Plug, and start your engine !

This version was labeled “XC”. Only a handful of the “XC” were produced. Numbers are believed to be under 100.

"XC" model Jonsereds
battery box and glow

"XC" model sprocket
Although I do not have this on authority, one can only imagine why the models sent here did not have a propane fired Tändror sitting on the ground in a pile of dried leaves.

This was the last model of the Jonsereds diesel saws. The exact year that production of the diesel saws ceased is not known for certain.

The diesels were said to be dependable saws, but it was also claimed that they lacked power.

There are many legends that follow the diesel saws. One is that in the frigid Scandinavian winters, the pressure of the Propane stored in the handles would drop and the propane fire would not be hot enough to properly heat the Tändror. To solve this problem, you held onto the handle bar at various points with your gloves in order to warm the handle bar, thus raising the pressure of the Propane inside.

It is also said that the quantity of the Propane stored in the handle bar would start a diesel a “few hundred” times.

I hope you found this article about these wonderful saws to be of interest. They are truly special saws and deserve their place in chain saw history!

Oh, what ever happened to Mr. Wiig ?? In 1953, while back in Oslo, Norway, Mr. Wiig developed yet another, very unique and rare saw. This saw was called the “Bamse”. The “Bamse” is a truly unique and wonderful saw, made by Norsk Sagbladd Fabrikk.

No, it was not a diesel, but it was every bit as unique as a diesel! It was a gasoline 2 cycle engine with a handle bar grip that rotated like a motorcycle accelerator.

The two (2) bladed cooling fan was rotated by means of a small fan belt which ran between the flywheel and the pulley of the fan.

In the 1950’s, Norwegian loggers would work late in the forests. To accommodate these late working loggers, Mr. Wiig installed an electrical receptacle on the fan cover of the Bamse. Two (2) different types of lights were available as accessories; a flood light to light the camp ground, and a flashlight with which you see in the traditional manner.

With the engine operating, a generator supplied power to this receptacle which had a small, weatherproof, spring loaded door.

Production of the Bamse was in extremely limited numbers. Each Bamse I have seen seems just a little different than the other.

These are pictures of the Bamse in my collection.

Again, I hope you have found this letter interesting.

George B. Blake

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