Vintage Aero was started in 2006 by Russell Ward in response to a local requirement for Tie Rods and Streamline Flying Wires. Round tie rods are employed as diagonal bracing in wings and fuselages as well as in some tail brace wires, eg: on Piper Cubs. Streamline wires are used as flying wires and landing wires in biplanes, and most modern aircraft which use tail brace wires, use streamline wires for decreased air resistance.
Tie Rods are round wires which have a reduced diameter just beyond the threads. This reduced diameter saves weight but also adds strength through the cold working process.
The first tie rods produced by Vintage Aero were fabricated by heating the ends red hot and upsetting them to increase the shank to the diameter to be threaded. This process was slow, expensive and resulted in a less than perfect product.
Currently Tie Rods are produced using a rotary swager which is able to reduce the diameter of a piece of steel rod with the added advantage of being able to start in the middle of the steel rod and progress out to the ends. Swaging the steel rods work hardens the steel and makes it much tougher.
The first threading attempts employed a single point cutting tool with a hardened backrest. This was a delicate operation was most the threads were very small (4BA). Currently a more modern threading machine is used, fitted with high precision thread rolling heads. Rolling the threads also increases the toughness of the thread, as no material is removed from the shank.
Steamline Flying Wires
The first streamline tie rods (flying wires) were for a static display and were produced using a set of press blocks and a 1000 ton press. The flying wires were produced in 6 inch (150mm) steps, and it took 620 tons to press a 6 inch piece of 1/4 inch warm mild steel. Progress was slow.
Subsequently a rolling mill was discovered and it was refurbished, but
the design did not lend itself to the quality required, so a search went
on for a replacement machine. Two plate rolling mills became available in
2009 and were purchased. They had previously been employed rolling blanks
for teaspoons, but the company found it was more cost effective to source
the teaspoons ready made from overseas. The rolling mills had to be
converted from a constant speed operation to
start | stop | reverse
operation. The first attempts at hydraulic control were not successful,
but after a series of frequency controllers were installed the resultant
efforts were successful.
Clevis fittings for both Tie Rods and Streamline Flying Wires
Stainless clevis fittings for the ends (AN665) were also an issue and after much research it was found to be more cost effective to source the stainless steel from the USA (where the quality was known) and have them machined and heat treated locally. This ensures quality control in contrast to relying on an overseas supplier.
Tensile Strength Testing
Tensile strength is an important factor with all tie rods and the specifications, published by both British and American authorities must be followed.
Initially a system was developed with a series of calibrated pressure gauges, which was certified by Air New Zealand’s engineering department who are approved by the local aviation authority. Subsequent improvements to this system have seen a face centered load cell and an ‘S’ beam load cell being added to this now computerized monitoring system for improved assurance.