Metal parts

Different types of metal parts can be found on a model car by Tamiya:

– Zamak
– Aluminium
– Steel
– Brass
– Bronze

In the 1970s and 1980s, plastic was a well-known material, but one with poor mechanical performance, and therefore had no application where mechanical stress was severe. Technology and knowledge of materials evolved over time: we went from almost completely metal models in the early 1970s to almost completely plastic models in the early 1990s.
Before the era of plastic, the use of metal evolved quickly; in fact, over time, the ability and technique of metalworking evolved, allowing Tamiya to develop competitively priced products with excellent quality, ranging from the cheaper Zama to the more performance-oriented Steel.
The metal parts of 1970s models have arrived to the present day in perfect condition, rarely are broken or bent parts found if the car was used correctly.
Metal parts made up 90% of the chassis for the first 10…15 chassis released by Tamiya, with the advent of plastic this slowly took over; today metal parts make up about 10% of a model car.
Metal was used to build the parts with the most wear or those parts most subject to impact: the wheel axles, bumpers, lower bumpers, some chassis, suspension arms, steering system.

Zamak
Zama or rather Zamak is an alloy consisting of aluminium, magnesium, copper and zinc.
Its name is formed from the initials of the names of the alloy metals in German: Zink (zinc), Aluminium (aluminium), Magnesium (magnesium) and Kupfer (copper).
Specific weight 6.50…6.80 g/cm3, varying according to the percentage of the various components.
It is a product that had some success at the beginning of the 1900s in various fields: jewellery, small ornaments, small everyday objects. Its success was due to the ease with which it could be worked and cast, its dimensional stability after casting, its resistance to corrosion, its good surface aesthetic finish and its good mechanical performance. Another advantage was its low cost.
It cannot be bent, this metal tends to break if forced to change shape.
It is certainly not one of the lightest alloys and was therefore only used by Tamiya in the beginning on a few models. Then by refining the construction techniques Tamiya managed to have the same parts made of aluminium.
For example, we can find these parts in Zama:

– the steering systems of the F1 chassis,
– the motor mount of the F1 chassis.
– the front suspension system of the SRB chassis,
– the gearbox of the SRB chassis,
– the gearbox of the 3Speed chassis and the Bruiser chassis and
– steering of the ORV chassis

This metal is non-magnetic, so it is not attracted by a magnet. Zama is easy to work with tools such as files and drill bits, so it is possible to carry out repairs involving the use of these tools.
A metal part if damaged can only be repaired if the damage does not involve rebuilding the part. Zamak parts can only be welded using special techniques and by professionals with skills that are precluded to most hoddists.
Welding a part to rebuild it is an activity that few people can do, and the result often leaves something to be desired anyway because parts always break at the point of greatest wear; a well-made weld does not always have the same guarantee of integrity as a new part.
Gluing Zamak parts is possible, but the mechanical resistance of two glued parts is infinitely inferior to an intact part formed from a single piece; it is not convenient to use this technique if you want to restore the functionality of a model car.
You cannot repair a component that has been twisted or bent due to an impact, a bad landing or a driving accident. Zamak parts tend to break when you try to bend them.
So when a part breaks or cracks, there is no alternative but to replace it.

Aluminium
Aluminium is an element of the periodic table, not an alloy of several materials mixed together. Specific weight 2.70 g/cm3.
With the first models of the 1980s, machining techniques were refined so Tamiya replaced the heavy Zamak with Aluminium. Aluminium is one of the most widespread materials on earth, it is in third place after oxygen and silicon, the mineral most exploited to obtain aluminium is bauxite, which at 50…60% consists of aluminium.
Due to its mechanical properties and lightness, it is widely used in the aircraft industry. The specific weight of aluminium is about one third that of steel and copper; it is much lighter than Zamak.
For example, we can find these parts in aluminium:

– chassis for the Tyrrel P34 family,
– motor mounts and differentials for the F1 CS family,
– rear wing supports for the Lotus JPS 79 family,
– electronics carrier and battery for the Countach family,
– gearbox shell for the ORV family and
– motor mount and rear axle for the Mk5..7 family.

This metal is non-magnetic, so it is not attracted by a magnet.
A metal part if damaged can only be repaired if the damage does not involve rebuilding the part. Aluminium is easy to bend and work with tools such as files and drill bits, but it is difficult to weld. So when a part breaks or cracks, there is no alternative but to replace it.
Aluminium parts can only be welded using special techniques and by professionals with skills that are precluded to most hoddists.
Welding a part to reassemble it is an activity that few people can do, and the result often leaves something to be desired anyway because parts always break at the point of greatest wear; a well-made weld does not always have the same guarantee of integrity as a new part.
Solidly gluing aluminium is possible, but the mechanical resistance of two glued parts is infinitely inferior to an intact part formed from a single piece; it is not convenient to use this technique if you want to restore the functionality of a model car. It is possible to repair a component that has been twisted or bent due to an impact, a bad landing or a driving accident.
To restore a bent part to its original shape, proceed as follows: clamp the part on a vice, heat the part as much as possible, carefully apply a constant force (do not hammer) opposite to that which caused the damage that forces the part to resume its original shape, repeat this operation several times.
To heat the part, use the coachbuilder’s heat gun, which generally has the function of heating surfaces to bake and then remove the paint.
To straighten a plate or pin always use pliers and a vice: the vice holds the part in place while you try to repair the damage by taking the part to be adjusted with the pliers and applying force in the required direction.
Avoid hitting the part in question with a hammer or trying to cold-force it, you only risk unnerving the metal, which becomes less strong and will therefore be prone to break again easily.
Aluminium is difficult for it to oxidise because a thin layer of oxide forms on the surface immediately, protecting the material and leaving it a light, shiny silver colour.

Steel
Steel is an alloy consisting of iron and carbon. Specific weight 7.5 … 7.8 g/cm3, varies depending on the percentage of the various components.
Steel guarantees excellent mechanical performance and resistance to stress, which is why it is chosen for all heavy-duty tasks such as rear axles, front wheel axles and suspension pivots.
Steel is a stainless metal that does not corrode by rusting or oxidising and is resistant to attack by chemical compounds. Of course, it has a high cost and specific weight: a steel part weighs about three times as much as an equivalent part made of aluminium. This explains why so few parts are made from this metal; they are few but vital.
For example, we can find these parts in steel:

– rear axle and pins for the differential satellites for the Mk5 chassis,
– axle and constant velocity joint for ORV chassis,
– rear drive axle for 3 Speed chassis and
– pins for transmission gears and torsion bars for SRB chassis..7

Steel chosen by Tamiya is magnetic, so it is attracted by a magnet.
Steel is not easy to work with tools such as files and drill bits. When a part breaks or cracks it can be welded or fixed but it is almost impossible for these parts to break or bend, it is more likely that the components that are in contact with these steel parts will fail first.
In the case of a twisted pivot or axle, the first choice is to change the part; if this route is not feasible, one can go the route of repairing a component that has been twisted or bent due to an impact, a landing after a bad jump, or a driving accident.
To restore a bent part to its original shape, proceed as follows: clamp the part on a vice, heat the part as much as possible, carefully apply a force opposite to that which caused the damage that forces the part to return to its original shape, repeat this operation several times.
To heat the part, use the heat gun for the body, which generally has the function of heating surfaces to bake and then remove the paint.
There are two techniques that can be used to straighten an axle.
The first is to use pliers and a vice: the vice holds the part in place while you try to repair the damage by grabbing the part to be adjusted with the pliers and applying force in the required direction.
If you do not get any results because the pin or steel part is too strong, you can try using a hammer and vice: the vice holds the part in place while you try to repair the damage by carefully hammering the part to be adjusted and applying blows in the required direction.
Be careful with the force used as it is easy to make the situation worse.

Brass
Brass is an alloy consisting of copper, zinc and other elements in small quantities. Specific weight 8.0 … 8.4 g/cm3, varies depending on the percentage of the various components.
It is a malleable material that has good corrosion resistance. It is easily machined with machine tools, but the chips remain long and compact. To overcome this problem, lead is added to the alloy. Due to its hardness and strength values, it is excellent for the manufacture of gears, universal joints, ball joints, small parts and small parts.

It is not possible to repair these parts.

Bronze
Bronze is an alloy consisting of over 70% copper, tin and other elements in small quantities. Specific weight 7.4 … 8.8 g/cm3, varies depending on the percentage of the various components.
Before the advent of ball bearings and plastic bushings, bushings were installed on Tamiya models.
Bronze has good mechanical properties combined with great corrosion resistance; it is an alloy that is easily machined by drawing, rolling, extrusion and forging. The purpose of bushings is to reduce friction on rotating parts such as drive axles.
To have the best possible effect, there must be a layer of lubricant between the axle and bush.
Bronze wears out more easily than steel; if lubrication is lacking, the bush is the first to wear out through friction.
The bushings in Tamiya machines come in different sizes.

It is not possible to repair these components.
Here is an overview of the evolution of components whose function is to reduce friction between rotating parts and improve performance (from left to right in the photo):

– bushings with a knurled edge,
– bushings with a smooth edge,
– solid Teflon bushings,
– lightened Teflon bushings,
– open bearings,
– version 1 shielded bearings,
– version 2 shielded bearings and
– version 3 shielded bearings

In the picture on the bottom right you can see the evolution of the bearing, the first version was without shielding. Shielding was added to protect the balls from dust and dirt in general.
Bearings from the 1980s do not have the typical knurls (there are nine in the picture and one is prominent) on the shield ring. In more modern bearings, the shielding is of a different colour and material than metal.

Cleaning
Cleaning metal parts is relatively easy because they are less prone to damage from chemicals.
The easiest method is to use fine steel wool type “0000”. Always work in the same direction with circular movements and polish the parts until they return to their original condition.
This way you can also remove small scratches from surfaces, but it does not allow you to clean uneven surfaces.
Take care not to scratch surfaces further, test in a corner to assess the force to be applied when brushing.
To reach hidden areas, you can place the wool on a flathead screwdriver and try to reach all corners. It is a method that requires time and patience.

The best method for cleaning metal parts in the most hidden areas is to use an ultrasonic washing machine.
The ultrasonic washing machine is a device for deep cleaning complex-shaped objects by removing the smallest particles of dirt or dust that hide in crevices that are difficult to reach with mechanical cleaning. The machine consists of a tank that is contained in the central body to be filled with cleaning fluid, a removable basket and a lid. The object or objects to be treated are immersed in the tank.
The ultrasonic machine combines the action of temperature and micro-bubbles that create micro-vibrations to rip off from the surface the particles of corrosion, oxide, dirt and grease that have stuck over time: the physical phenomenon exploited is ultrasonic cavitation. The machine has a 45 KHz generator that drives piezoelectric transducers that generate a mechanical vibration.
The ultrasound that is generated creates an infinite number of bubbles in the liquid of the tank that burst, releasing a great deal of energy (cavitation); as they burst, they release a concentrated energy that carries dirt away from the surface of the objects in the tank.
On average, a treatment at 70°C for about 25 minutes is sufficient to thoroughly clean heavily soiled metal parts; at other temperatures and times, most materials can be cleaned.
The procedure to follow is as follows: first clean the parts with hot water + hard-bristled toothbrush + dish soap, prepare the cleaning liquid for the washing machine with demineralised water for irons to which you add the dishwashing detergent, set the temperature + treatment time, switch on the machine, leave the parts in the ultrasonic machine for the treatment time, rinse the parts under hot water and dry them.
The workpieces should be placed inside the basket, they should not touch each other as the micro-vibrations generated could cause the workpieces to mark each other.
It is better to treat homogeneous metals without mixing them together, especially chemically weaker metals, such as bronze and brass, if washed with other chemically stronger metals, they may become covered with a patina of oxide.

Rust

Rust is a problem that greatly affects metals in that there are often traces of iron in the alloys, which causes the spontaneous formation of iron oxide that is characterized by a dark reddish-brown color. Even in small parts (screws, nuts and bolts) there is a minute trace of iron that oxidizes causing unsightly dark-colored spots to form on the metal.
First proceed with a thorough cleaning of the parts using warm water with kitchen soap by scrubbing the parts with a hard-bristled toothbrush, wash the part with the ultrasonic machine and then polish. If the above had no effect or the end result does not meet expectations, proceed by soaking the parts in automotive diesel oil for at least seven days. The diesel oil will degrease and dislodge rust from the metals; after the week has passed, the parts should be taken out of the diesel oil bath and cleaned with a paper kitchen cloth rough enough to take away whatever has stuck to the surfaces. After this treatment the parts will be practically new again. Preferably use glass containers for the diesel baths.

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