PK Corally 1/12 Car Build

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K-Max
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PK Corally 1/12 Car Build

Post by K-Max »

Hello all,

I've decided to build my PK Corally NIB kit and thought I would share the process step by step.

Released back in 1986, this was the first 1/12 car from PK Model Racing. The 'P' and 'K' of PK Model Racing represented the family names of owners Constant Paul and Jan van Kooij.

This car was based on the Schumacher C car but was refined further in its design. Unique to the PK Corally was its use of aircraft grade aluminium alloy in a 1/12 chassis; coined CORAL, it was intended to be more resistant to tweaking compared to the ubiquitous fibreglass chassis.

When launched this car costed approximately USD400. It was definitely a luxury kit at that time.

20200709_195352.jpg

Upon unboxing one is greeted with 9 ziplock bags, each bag representing a 'group' as referred to in the manual, to be assembled in sequence. There are no step by step instructions per se, you'd need to refer to the exploded diagram as you step through each 'group'.

20200709_183425.jpg
Shian

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PK Corally 1/12 Car Build

Post by K-Max »

Group 1: T-bar and Motor Pod

20200709_134907.jpg

The T-bar is made of carbon fiber, but rather than the usual woven construction, here it is made up of 11 layers with the carbon threads laid in 4 directions to render the sheet resistant to tweaking.

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The motor pod is offset slightly to the left so that the motor will be perfectly centered.
Shian

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PK Corally 1/12 Car Build

Post by K-Max »

Group 2: Main Chassis

20200709_140847.jpg

The CORAL chassis has an attractive anodized hairline finish.

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Carbon fibre cross members are held down by the radio plate posts, here the similarities to the Schumacher C car is clear.

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There's a lot of attention to detail - the countersunk holes on the bottom are deeper and allow the screw head to seat deeper inside.

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At this point the T-bar assembly can be connected.

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Close-up on the pivot that creates rear end articulation. An o-ring compressed by a bevel washer provides the play required.

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The motor pod has a feature to locate the motor position with a screw, I believe this is intended to save time on gear meshing when the motor is removed and put back.

20200709_202801.jpg
Shian

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PK Corally 1/12 Car Build

Post by K-Max »

Group 3: Radio Tray and Damper Plate

All molded parts of the PK Corally are carbon filled, except for the body posts. This helps to keep the shape of the part and would be an effective property especially for the wheels.

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Close-up on the lower half section of the rubber boot, friction plate and spring. The rubber boot was first sprayed with rubber treatment compound to 'moisturize' it. I was extremely careful when working on them. In some cases they crack with age (34 years!). The friction plates are sprung against the damper plate (that is fitted next) from bottom and top. The friction plates themselves have o-rings to damp their sliding along the damper post.

20200709_203311.jpg
20200709_203329.jpg
Shian

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PK Corally 1/12 Car Build

Post by K-Max »

Group 4: Front A-arms & dampers

20200709_204420.jpg

The damper posts are meant to articulate and are held in place from the main chassis with small o-rings.

20200709_204438.jpg

The A-arms articulate from 3 pivots, the shared front center pivot is shown here. O-rings are in use here again - there are 3 for each pivot post.

20200709_204453.jpg

The front dampers need to be very very carefully pushed into position, and the next picture will give an idea what was required. I used the blunt end of a wooden tooth pick to do this.

20200709_204504.jpg

After this painstaking step the A-arm with the damper is placed into position with the damper post pushed through the damper, again another fragile step to be careful with.

20200709_204518.jpg

One of the rear pivot post is integral with the steering servo mounting post. The A-arms are held together at the front with an o-ring. I don't think this was intended as a crash-back system ala Schumacher Cat XLS but rather as in improvement on the initial design that saw the arms come loose against this shared pivot post - the o-ring would keep the arms always located against the shared pivot.

20200709_204531.jpg
Shian

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Re: PK Corally 1/12 Car Build

Post by winner_evo »

Very nice, as you say, you can certainly see elements of the C car. Do you have a body and will you be fitting full electrics into it?

Great documentation of the build 8)

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Re: PK Corally 1/12 Car Build

Post by K-Max »

Thank you :)

I intend to fit a Novak servo and receiver to this car, as well as a TOJ body shell later.
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PK Corally 1/12 Car Build

Post by K-Max »

Group 5: Front springs and anti-roll bar

20200709_210709.jpg

The springs are screwed into the threaded aluminium caps, the purpose for this shall be explained shortly. The spring perches that the springs will later screw onto are also threaded. The perches themselves are press-fitted to the A-arms.

20200709_210720.jpg

With such a setup, the A-arms 'hang' from the spring caps, and therefore the droop of A-arms can be adjusted by turning the damper posts.

20200709_210732.jpg

The anti-roll bar is connected to the A-arms from below. The connectors are held in place to the A-arms with small o-rings.

20200709_210754.jpg
20200709_210743.jpg
Shian

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PK Corally 1/12 Car Build

Post by K-Max »

Group 6: Steering blocks & king-pins

20200709_212623.jpg

Similar to the C car, the stub axle is shaved with a semi-circular recess to clear the king pin. However, instead of a stub axle, in the case of the PK Corally, you have a rotating axle to the ballraced steering block (the front wheel does not rotate on the axle). In order to minimize rotating mass the axles are made from lightweight aluminum.

20200709_212647.jpg

The rotating axle is designed to be kept in place by o-ring, and you can see attention to detail in the notched flange of the axle that allows for easier o-ring removal.

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However, rather than use o-rings this time, I opted for the plastic c-clips that came with later Corally cars. They are easier to remove than the o-rings.

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The steering blocks have ball races also for the king pins.

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The king pins are simply screwed into place on the A-arms. Translucent spacers allow for ride height adjustments. Again, instead of o-rings I used the c-clips for the king pins to retain the steering blocks.

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Shian

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Re: PK Corally 1/12 Car Build

Post by GeneralZod »

Thanks for sharing your build! Looks modern even by today's standards. I always liked Corally but parts availability here was non existent bitd. :D

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Re: PK Corally 1/12 Car Build

Post by K-Max »

Thank you :)

I’m new at doing build documenting. I’m really happy to be able to share.

Back in 1986-87 when I first saw this car I couldn’t afford it as a student then, so it’s nice to find one to build today.

I reckon Corally was easier to find in Europe in the days.
Shian

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Re: PK Corally 1/12 Car Build

Post by Burniefloyd »

The aluminum, anodizing and carbon fiber really make for a very striking car. Great build, can't wait to see it finished.
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Re: PK Corally 1/12 Car Build

Post by DennisM »

Pure candy for the eye - Nice build thread
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PK Corally 1/12 Car Build

Post by K-Max »

Thanks guys! :D It's been an interesting build so far, with only exploded diagrams for assembly instructions :shock:

Group 7: Rear axle & differential

20200710_172957.jpg

Unusually there are 4 rather than 2 diff washers. The spur looks to be 32P. I'll need to find a 32P pinion.

20200710_173019.jpg

After assembly the whole diff unit looks well enclosed against debris.

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The ride height adaptors cap over the ends of the oval extruded tube of the motor pod and are easy to change out.

20200710_173056.jpg

Rear diff and axle now installed:

20200710_173120.jpg
Shian

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PK Corally 1/12 Car Build

Post by K-Max »

For the first time with this build I'm finding out some design revisions to this car.

Earlier PK Corallys had a chain-like element linking the 2 front A-arms, as can be seen in the following diagram, part #38.

20200710_173517.jpg

In my kit however, part #38 takes the form of the letter 'U'. It would drop out when the car is flipped upside down. But then I realized it should fit from underneath the A-arms instead, with an added tab feature of the main chassis holding it in place.

20200710_173332.jpg
Shian

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