Thread: Stihl E15 electric chain saw

Hi all,

recently i bought a Stihl E15 electric chain saw through Ebay Germany. A lady sold it, it belonged to her dad, who chose quality tools only, and took great care of them. It turned out to be a beautifully preserved and only lightly used machine. It merely took some cleaning and some paint retouching to have it back in almost new shape. She was pleased to hear that i would carry on taking good care of the machine, in the tradition of her father. Apart from running into beautiful items on internet auctions, you can also run into beautiful people.

This saw is such a nice piece of kit that i would like to tell a bit more about it.

Andreas Stihl started off in Stuttgart in the early 20's, with the manufacturing of electric fan assisted oil burners for boilers, and also electric washing machines. Therefore it's not surprising that the first Stihl chain saw from 1926 was also electric. It came in two versions, a two-men operated timberyard version and a one-man operated cut-off type rated at 2.2 kW input and weighing "only" 48 kilograms (see first two pics below, borrowed form the official Stihl company website). Stihl offered both DC and three-phase AC versions. DC originated from the initial two wire Edison mains distribution systems (built in Germany by Emil Rathenau's "Deutsche Edison Gesellschaft", later to become AEG) , with a maximum voltage of 127 Volts. Draining 1 or more kiloWatts from 127 Volts would mean big currents in all cables and through the motor itself. Besides, DC power automatically means that the motor must have a wound armature and brushes. Since armature windings are packed tight and therefore have a high energy density, armatures typically suffer the biggest cooling problems of all motor components. Insulation materials of those years were by far not as reliable and resilient as they are today. You must think shellac, cotton, natural rubber, bakelite and mica instead of epoxy resins, esterimide, teflon and silicones. Running on DC, adverse circumstances like induced counter-voltages and flashover-risks, are far less of a concern than what they would be with AC, so these first Stihl large brush motors were by no means fit for true universal DC/AC operation yet. Because of the far from ideal insulation reliability of those years, no tool or appliance manufacturer dared push brush motors beyond a 300 Watts input rating, when run on AC. Such modest rating was enough to drive the first electric AC/DC electric drills and vacuum cleaners, but not yet enough for the more demanding applications like circular saws or industrial grinders. These heavy duty machines were still the terrain of the three phase AC powered induction motors. So, apart from starting to make petrol chain saws from 1929 on, Stihl concentrated on three phase power for electric chain saws when the Edison DC system was gradually being pushed aside in Germany in the decades to come, in favor of Nikola Tesla's AC system with proven superiority.

AC and three phase mains systems were first adopted in the south of Germany, following closely behind the pioneering neighbours Austria, Switzerland, Hungary and Italy. So it was logical for the German industrial areas to have three phase power installed in an early age. Three phase motors powered stationary saws, planers and thicknessers, routers and mortisers in virtually any woodworking shop or factory. Since there was three phase power available around these places anyway and one had to go out to fetch expensive petrol from sales points few and far between, timber yards favored electric chain saws for a long time. Petrol was okay for use in remote places like forests, but inside the shop or on the timber yards from which fumes could waft in through open doors and windows, electric power was a better choice. So large AC chain saws were three phase up to the times when reliability and power-to-weight ratio of large AC brush motors were good enough to run them on single phase AC.

For chain saw fans, there is a very interesting site run by Manfred Pfeifer, a collector of such machines. This is a link leading you to it:

http://www.motorsaegensammler.de/English.htm

Do take a look at the electric saws featured in his collection pics. Apart from Stihl, you also see examples from Festo, Dolmar and Mafell, other woodworking firms with stationary machine and induction motor experience. You see all sorts of interesting one-man and two-men operated sword- or bow type chain saws, all with three phase motors. Mafell reduced its chain type assortment to some sole guided beam treatment types and some chain mortisers and Festo left this niche altogether, but Dolmar is still the second German name in the chain saw field. It even started earlier than Stihl, in 1926, near Hamburg. It always worked closely together with its petrol motor supplier Fichtel & Sachs (leading to the Sachs-Dolmar branding) and was bought by Makita in 1991 (which explains the sudden appearance of Makita petrol driven machines around that time). Present electric Dolmar chain saws have Makita electric motors and are sold in both Dolmar red and Makita blue.

The disadvantage of conventional 50 Hertz induction motors is their bulk. Nikola Tesla had already proven the fact that the energy density inside induction motors could be vastly increased and their size considerably reduced when the 50 Hertz frequency was cranked up to 200 Hertz or more. I have left a thread about this a few weeks ago in this forum and i wonder if there have ever been high frequency AC electric chain saws. For myself, in never saw one, although i have seen pneumatic and hydraulic chain saws (the latter can even be used under water!). Anyway, Stihl has problably studied this option and must have decided some moment in time that the extra expense of the obligatory special frequency converter was not worth the effort. For single phase AC (meaning that it could run on any household mains facility and that it allowed the provision of double electrical tool insulation easier and cheaper than in a three phase tool) Stihl apparently went for an AC brush motor straight away, as soon as a heavy and utterly reliable version of it became available. In that league, the choice for a heavy angle grinder motor was a good and logical choice. Both angle grinder and chain saws must withstand heavy loading during longer periods of time. The motor and the gears experience about the same amount of torque and shock load and an angle grinder and a chain saw will have about the same duty cycle and load function curves.

The first heavy tool use AC brush motors were introduced by Ackermann + Schmitt in an angle grinder in 1954, as a reliable enough alternative to the three phase high frequency industrial grinders. This DL9 type had an input rating of 1600 Watts and all leading tool manufactureres were quick to copy this design for their own program. AEG's efforts evolved into the WSA1900 in the latter 60's, and Stihl settled on this power source for its first single phase AC chain saw. Apart from the heavy angle grinder motor, which was also ideal for chain saw use, the angled gear system was another bonus. With the motor mass being in straight line behind the chain blade, without any bulk hanging from the side, the handling balance was very good. This inline-design was no first, however. In Manfred Pfeifer's pics you can see that Mafell and Stihl already used angled gears on their older three phase machines.
But the supply of angle grinder units by AEG was not so straigthforward as one would think. I've often read about the suggestion that a broken Stihl E15 would leave you with a decent vintage AEG angle grinder. Just replace the sprocket arbor for a regular M14 one and add a bottom bearing plate including the mounting for a grinding disc safety hood, and presto. But on a regular right-handed chain saw, with the blade and chain positioned on the right and hence motor and gears bolted on to the left, a regular angle grinder would drive the chain in reverse. So AEG had to make mirror images of the regular WSA1900 grinder, including mirrored versions of the Gleason gears. Such unit would make a nice left-handed angle grinder, but you wouldn't find a reverse threaded M14 arbor for it, unless made to special order.

AEG and Stihl settled on a co-production straight away, since AEG also wanted this saw for its own program. The Stihl E15 version was fitted with a 45 cm sword/blade, and AEG chose a 36 cm blade. Motors for the Stihl factory left the Winnenden plant unpainted, with two rivet holes on top for the Stihl branded badge. Cast frames and oil reservoir lids, made by Stihl for AEG, left the Waiblingen plant with the AEG typeface cast into them. This swapping of components left to the KES36 in the familiar Berlin and the E15 in light grey and orange. KES is short for "Kettensäge".

The pics below are from a German auction site and conveniently show both machines side by side, for comparison.

greetings

gerhard