RM MK5

Model
Tamiya Porsche 956 Rothmans, article number 58042 put on sale in 1984 and available on the market until 1992.
Lexan body.
RM Mk5 chassis.

Analysis of the model to be restored
Starting from the front and moving towards the rear, an analysis of the body reveals that

– frontally the body is slightly deformed, which happens in a frontal accident because there is no front bumper of sufficient size to protect the body. All the energy of the impact is dissipated by the lexan.
– the holes to attach the body to the front chassis are damaged,
– the holes for fixing the body to the chassis at the rear are damaged,
– the colour scheme does not conform to the official one and has seen better weather,
– the stickers are almost all original except for the Futaba one on the windscreen + the two ‘Globee’ stickers on the right – left sides and
– there are no cuts or additional holes.

Starting from the front going to the rear, analysis of the chassis reveals that

– the two front aluminium alloy supports are missing,
– the front bumper is missing,
– the front rims are not those of this model,
– incomplete electronic system, one servo and the receiver are missing. The type A male Futaba plug is present, which is rare,
– the mechanical speed control system is missing which is peculiar. This system was only used by Tamiya on the RM MK5,6 and 7 chassis,
– the motor is not the original one,
– the rear wheels are fitted with sponge tyres for the front wheels; the tread width is less than it should be,
– there are signs of wear in the lower frame,
– the upper frame is broken at the point where the antenna is attached, it was a fault that happens every time the car tips over and
– the model comes complete with 4 rims with spare tyres; 2 front and 2 rear.

The photo shows all the parts involved in this restoration:

– mechanical speed control, SP-5214,
– black rear axle for Porsche 956 Rothmans, SP-5125,
– switch with Futaba A-type plug,
– driver,
– set of plastic straps to secure the battery,
– front bumper and
– receiver and servo for mechanical traction control with Futaba type A plug.

Frame Restoration
Sequence of images showing the stages in which the chassis is disassembled to check each of its parts; at this stage look for broken parts, missing parts, modified parts, screws that do not unscrew…

– remove the four wheels,
– disassemble the front suspension system which includes the steering system,
– check that the front suspension springs are the cylindrical ones for this set (Porsche 956 Newman and Toyota Toms 84C have conical springs),
– dismantle the rear suspension system,
– uninstall the motor that is not the original one and
– check the pinion gear, which on this model is alternatively 16, 17, 18 and 20 teeth. Install the 18-tooth pinion gear.

The left rear system support has both screws that are oxidised and their heads are stripped: they cannot be unscrewed. One of the two rear body supports is broken.

When a screw does not unscrew from a metal support, heat the parts and the heat expands the screw and support differently, separating the screw from the support and releasing it. It is not possible to heat the FRP plate without damaging it; the following sequence of pictures shows the procedure for releasing the screw without using a flame:

– install the cutter on the hobby drill,
– activate the drill at maximum speed,
– place the cutter on the screw and
– apply such a force that friction due to the rotation of the cutter on the screw head causes the screw to heat up; the heat acts by detaching the screw from the aluminium part without ruining the FRP plate.

The two screw heads are completely ruined and the frame is completely disassembled.

The following sequence of pictures shows the procedure for repairing the rear pin that supports the body, the rear pin is divided into two parts; a shorter and a longer one:

– heat a paper clip or 1 mm diameter metal wire with a lighter or gas cooker fire,
– when the metal has turned red, insert the metal in the centre of the shorter part. Repeat the operation until the metal penetrates 3..4 mm into the black plastic cylinder, in the last operation let the paperclip – metal wire weld to the plastic,
– cut the paper clip, leaving a 3…4 mm long piece of paper clip or wire protruding from the plastic,

– heat what is left of the paperclip with a lighter or gas cooker fire,
– insert the paperclip – metal wire into the long part of the support to make a hole deep enough to accommodate the trunk of metal wire that is welded into the short part,
– join the two parts with acetone and ABS solution; the metal is the structural reinforcement and the solution is the adhesive,
– machine the pin with 800 grit paper to obtain a diameter to fit it into the aluminium support and
– colour the white solution of acetone and ABS with XF1 matt black.

Wash all parts with hot water and degreasing kitchen soap and then run a cycle in the ultrasonic washing machine: metal parts for 25 minutes at 70°C and Teflon or plastic parts for 25 minutes at 40°C. Replace damaged parts such as screws with filed heads.

Work the FRP parts with 1000, 1500 and then 2000 abrasive paper to remove traces of glue and scratches; wet the surface of the FRP plate with water, dip the abrasive paper into the water, work the surface with the paper on a smooth surface so the resin dust does not fly off, but collects on the surface in the form of mush. Polish the two plates with Tamiya polish to give a shine to the surfaces treated with sandpaper.

Electronics of this machine consists of:

– two servos with Futaba male A-type sockets,
– receiver,
– switch with Futaba male A-type battery connector,
– the RS540 black motor and
– the speed controller.

Clean the servo and receiver with a good degreaser and 90% pure alcohol if they are dirty and/or covered with double-sided tape glue.

The following sequence of pictures shows the procedure for re-assembling the chassis:

– assemble the rear axle complete with differential,
– install on the lower FRP chassis the two aluminium parts to house the rear axle, the two rear pillars to install the body, the rear suspension and the motor,

– assemble front axle that serves to accommodate the steering system, house the front suspension, the two aluminium alloy front pillars to install the body and the front bumper,

– The FRP top plate houses all electronics except the motor. Installing the various parts is quick and requires two screws for the speed control and two screws for the switch. The rest is installed using double-sided tape and clamps. A very light solution indeed. The only drawback is that installation cannot be changed once it has been done, otherwise all the parts will come loose.

Beware of the steering servo, if it is too wide it risks interfering and blocking the steering arm. In this case, it is preferable to cut the servo side plate, which allows the servo to be locked with two screws (not used in this case),

– install the upper plate to the lower frame while waiting for the wheels.

To remove blue colour from rims, soak rim and tyre in 90% pure alcohol. After 24 hours of soaking in the alcohol, the colour is removed by wiping with a fairly rough paper towel. Immediately after this, soak rims and tyres in water and leave them to soak for 24 hours, so alcohol does not stick to the sponge and water makes the sponge soft and supple again.
If alcohol detaches the sponge from the rim, use double-sided tape to join the parts again. Use suitable skin protection (disposable gloves) and eye protection (goggles).

Body restoration
The following sequence of pictures shows the procedure for stripping the body

– remove all adhesives
– fill a 5-litre container with 90% pure denatured ethyl alcohol or more free of aromas or pink dyes; 99% pure alcohol is available on the market,
– soak the front of the body in the 5-litre container for 12 hours. Alcohol flakes off the paint, which becomes soft and peels off, beware that as alcohol evaporates the paint becomes hard again and sticks well to the surface,
– remove the body and mechanically remove the paint using paper towels. Use suitable skin protection (disposable gloves) and eye protection (goggles),
– use cotton wool and toothpicks for hard-to-reach parts,
– repeat this operation until the snout is completely free of paint and
– use the same procedure with the rear part of the body.

Especially where the white body will go, try to remove even the smallest stain of the previous colour. Hunt down even the smallest speck and remove it by applying light force with a wooden toothpick. This is a time-consuming and tedious operation that requires great care to avoid scratching the body. Before applying paint, treat with toothpaste or polish to soften abrasions and erase lines.
Mask to paint the air intakes and headlights and paint the two front headlights, the central NACA air intake, the rear NACA air intake, the two intakes on the nose of the car and the two air intakes on the front bumper in X1 black.
Mask to paint the 2+2 square air intakes in the central part and paint colour X11 grey.

For the Lexan body, start with the dark colour first and then pass the light colour from blue to white. Close all holes in the body to allow the 4 support pillars and antenna to pass through. Use food-grade plastic film to mask the very large parts.
The dividing line between white and blue is covered by the white – red – gold sticker that runs along the left and right side. Once the blue is gone, remove the masking and place the new masking in place to colour white. Mask the windscreen and the right-left window with masking tape so that when the work is finished removing the tape the transparent lexan remains.
Overcoat with white also on the blue colour, which will not be affected as it is darker.

Driver of this model is made of lexan with the head separated from the body, always colour the darker colours first and then the lighter ones. Follow this sequence: red for the two gloves, grey for the two belt buckles, red for the two belts, white for the body and then black for the background.
Follow this sequence to colour the helmet: pink for the face, white for the helmet, blue for the stripe, matt black for the underside of the helmet and outline of the visor, matt white for the eyes and black for the pupils.
To install the helmet on the body, make a hole with a star-shaped screwdriver of the right size, first heat the screwdriver with a lighter and then press it into the exact spot where the screw that holds the helmet to the driver’s body is to be installed, the heat melts the lexan and hardens the contour of the hole, making this part strong enough to accommodate a screw.

Restored model
Images showing the finished model.

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