Vinland 2 - October 10, 2009
Working towards a reconstruction of the L'Anse aux Meadows Smelt

Smelt Report

The core team was:
Smelt Master - Ken Cook ( Darrell Markewitz assisting)
Ore - Darrell Markewitz
Charcoal - Sam Falezone
Strikers - Neil Peterson / Richard Schwitzer
Smelter construction - Darrell Markewitz & Ken Cook
Pump Bellows Construction - Darrell Markewitz & Sam Falezone

Starting in Winter of 2009, detailed investigations of the the archaeology of L'Anse aux Meadows, Newfoundland (site of the first iron smelt in North America, c 1000 AD) was started. There has always been some uncertainty about what exactly the remains excavated at the site indicated. The purpose of the Vinland series of smelts is to interpret the archaeology in light of what has been learned through research and direct experience over the last decade. These aspects will be combined into a full scale historic re-creation of the original Norse iron smelt, scheduled for August 23, 2010 at L'Anse aux Meadows NHSC.

More Details of the investigation will be found in a paper currently under preparation. Separate topic elements have been published in a series of short articles on the blog.

The smelt undertaken on Sunday October 10, 2009 at Wareham, marks the second in this series.

Primary Objective - To employ an air system that mimics that delivered by a Norse style bellows to the LAM furnance design. This to familiarize the team to the different SOUNDS resulting from a plused air delivery system.

The core of the system is a small bicycle rear frame, cut down to retain the 6 speed gear set, rear forks holding a 20 inch rim, and the peddle crank set. I am mounting this so that a 1/4 HP electric motor (scrounged at the dump) will drive the system, via a pulley onto the wheel. In turn the gears / chain / crank converts the rotation into straight line thrust. Using a pivoted push bar, the mechanicals will operate a modified box bellows. The input on each side was a simple rectangular leather flap valve. The output used two standard one way sump pump valves.
By calculating the chamber size against throw distance (in this case 12 inches / 30 cm against a plate size at 25 x 25 cm) the theoretical delivery volume was matched against possible air requirements for our standard small furnaces. Stokes per minute will be the adjustment. In theory this could be changed by two methods, first gears on the 6 speed derailer, second by placing a light dimmer switch on the incoming electric power to the motor.

The point of all this is to give us experience with the type of air delivery created by a double chamber bellows compared to that from the electric blower system we normally work with. A blower produces a constant air blast, while the bellows 'pulses' its air. The use of a mechanical system avoids the major problem with a human powered bellows - the huge labour requirement. The norse double bag bellows will require roughly one stroke every 1 - 5 seconds (depending on size and volume required) over the entire 4 - 6 hour firing of the smelter.

In the end the bizarre combination of bicycle, electrical, plumbing and both metal and wooden parts was chistened 'the FrankenBellows'!
In the end it was found that it was only on the lowest gear setting, with the motor running at full speed, was it possible to generate enough raw torc to operate the piston mechanism. In addition, there was considerable loss around the edges of the central plate. The mechanical challenge here was getting the plate to fit tight enough to reduce loss inside the pump box, but at the same time allow freedom of movement (torc problem above). Considerable effort and raw trial in error was involved in finding a solutin to these opposing requirements. Eventually each edge of the square internal plate was wrapped with a layer of felt. These and the entire movement pathway was heavily greased with petrolium jelly.

In actual operation, the motor was driving the crank assembly through one complete cycle roughly 90 times per minute. Given the alternating push and pull method of filling and emptying the dual chambers, this resulted in 180 individual air 'stokes' per minute. When measured with the anenomometer, the actual working volume was recorded at 255 LpM. Although the resulting air pressure was very good, the volume was less than what was required ( for 20 cm ID at an estimated 380 to 560 LpM).
(See also the Video Segment below, which starts with a close up of the Box Bellows in action)
Another task undertaken well before smelt day was preparing the ore analog to be used. Because of material shortages, it was decided to blend partial batches remaining on hand:

DARC Dirt 1 - Red (Fe2O3 at 64% / Fe at 45%) = 6 kg
DARC Dirt 2 - Black (Fe3O4 at 79% / Fe at 64%) = 4.6 kg
Haematite Grit - (Fe2O3 at 98 / Fe at 68%) = 10.1 kg
ANALOG PREPARED - (Fe 61%) = 20.7 kg

The method was to first screen out the larger lumps of the two DARC Dirt analogs. The remaining 'dust' (below 3/16 screen size) was combined together with the haematite grit and enough water to create a paste. This was in turn dried, then broken to lumps for adding to the smelter.

Because of the extra time consumed by preparing the FrankenBellows, the construction of the smelter itself was put off until the morning of smelt day. This need to both construct the furnace, and run a complete smelt sequence in one day effected the construction methods employed.

Spreading out a layer of charcoal fines to isolate the area after a summer's growth. Prepared potter's clay sliced to slabs, joined around a form covered with newspaper. On completing the first layer, the form is removed and the centre packed with dry sand. This allows the form to be moved up for layer two. Note stones helping to prevend the first layer from slumping
A mix of sand and ashes used to fill the gaps between the stones. More stones are piled to support layer two. Here the remaining clay slabs are being added to a height of roughly 45 cm. To ensure the required furnace height, a layer of standard firebrick is mortared together with the remaining clay. To hold these heavier elements in place, several loops of wire are used.
The standard ceramic tube tuyere set into place. Note the blocking in of the area with stone slabs The complex piping allowing both the Pump Bellows and electric blower to be ganged together to provide the required air volume. Late into the preheat phase. Steam is being driven out from the wet clay as it heats.

View down inside, near the end of the pre-heat, with the ceramic tuyere shown. Light coloured portions of the walls have had clay spall off due to steam explosions. Complete set up for the air system, just as the first load of charcoal was added.
Video Segment edited for YouTube

The construction of the furnace, plus the extended preheat required for the thick clay slab walls, considerably delayed the start of the main smelt sequence. This in turn pushed the extraction point well past sun down. (For that reason there are few good images of the extraction and primary consolidation steps.

Team in place: Sam (charcoal) at left rear / Darrell (ore) at right rear / Ken (smelt master) at centre front. The furnace self tapping, slag flowing through one of the cracks in the soild clay walls Striking in the dark - primary consolidaton

The final results of this sucessful smelt:
Total Charcoal - 43 KG
Total Ore - 20.7 KG
Main Sequence - 4:45
Bloom - 5.6 KG
Yield - 27%

Text and photography © 2009, Darrell Markewitz
Any images containing Darrell shot by Ann Graham