Lotus 72C Construction

Here is the latest information on the construction of the 1:12 scale Lotus 72C, super detail kit. Updated 12/1/09

After attempting to scratch build the prototype parts for production and trying to produce them in such a fashion that a trans-kit would also result, for the Tamiya 72D, it proved to be most difficult and was causing problems. I have therefore decided not to produce a trans-kit at this time. I will visit the idea again once the kit is completed.

I chose the Lotus 72C, not just because it is one of my favorite F1 cars, but it represents a major part of F1 History after replacing the 49C in 1970 and being the basis of Lotus F1 cars for almost 6 seasons, also being Jochen Rindt's 1970 F1 World Championship car.

I have since been producing the model in 3D software "solidworks", which has enabled me to assemble the parts and make sure everything fits before fabricating any parts. Below you can see the new progress. To which I owe many thanks to Derek, a friend and customer, for his work and teachings of solidworks. Also Lee, another friend and customer for introducing me to "Solidworks".

Of course none of this would be possible without the information, help & support of Clive Chapman and Classic Team Lotus; also allowing me to forage through original drawings in their archives.
It has still been a difficult project as there are no original 72C's to examine, the ones that are around have been rebuilt and even then getting close to one is near impossible.

I also have to thank Erich Walitsch for his help and information, a great Jochen Rindt fan. www.jochen-rindt.at

Producing the model in this fashion I can have prototype parts printed on 3D printers, which I can then clean up and produce masters for making the molds.

New Construction Diary start date 7/31/09
Starting with the floor pan, seemed to be the best place to start this time around, but even something that seems as simple as the floor has gone through 3 or 4 generations. It is just as well I have been doing it in the 3D software.

I plan on the floor pan being 1mm thick aluminum and having all the necessary positions for holes etched into it, but this may not be practical as the underside has to have a lip machined into it. So depending on production cost, the holes may be drilled in it. You can see the detail of it here.

The tub, seat pan, seat back and many other parts will be Photo etched in aluminum sheet approx. 0.012" thick. I know it's not to scale but it is far more practical. This is how they should come out.

Right side tub. Seat pan. Seat back. When you have folded them into the correct shape they should look like this.

Right Left , Seat back and seat pan

I will supply enough rivets for anyone that wants to put a rivet in every position. If you don't want to use all the rivets you can simulate rivet heads by using a scriber, punch or something with a point, by applying pressure to the back of the aluminum at the etched marks.

The fuel line which connects all 5 fuel tanks together will be included, some people may decide to leave it out because it is under the seat pan. Some will also leave out the side tanks, it depends on how you want to display it. Here is the front left fuel tank. the recess in the top is for the fuel filler and the slot along its length is the clearance for the torsion bar part of the suspension. The rear tank has the last part of the clearance for the Torsion bar The "stubs" sticking out of the tanks line up with the Fuel line and connected together with some tube (supplied) and PE hose clamps (supplied). The rear tank will be necessary to install as it will play a major part in the kits assembly it has relief in the bottom and locating pins that line up with holes in the floor pan. All the fuel tanks will be resin.

The outer skin will also be resin, hopefully no more than 0.020" thick, I shall know for sure after the prototype parts are made. I have designed the bodywork in such a way as the sides can be removed to display the fuel tanks, via locating pins on the bodywork and associated holes in the tub. It may be difficult to see the pin here, so I made it a different color for ease.
All the fuel tanks have locating pins in the bottom for ease of assembly, and to make sure you have them in the correct place again I colored the pins so you can see them easier.

I have tried to be true to the car with all the access panels, hence the recesses in the fuel tanks and outer skin. The panel covers will be Photo Etch parts. You can see the shaded areas are the recesses on the skin to accept them. The two stubs at the rear are for mounting the radiators. I still have to work at the mounting bracket for the engine at the back before I can have the skins produced.

I want the shifter to actually have motion, but we shall see how successful that will be. Here is the shift lever

The shift rod, front half the bracket and tube which will be a piece of aluminum tube, supplied, that you will have to trim to fit. I know, the bracket looks ambitious, but it will change so that the screw heads are already in it, it will have the locating pins on the back, which align with holes in the tub side.

I am not too far away from have prototype parts printed and a test run of the major Photo Etch parts. If all goes well the parts should assemble something like these pictures.
sides dash bulkhead Tank, seat back Right side tanks and how they fit and the fuel line

There is still a lot to do but progress is much quicker now, plus not all the previous work is for naught, all the machined pieces will work. :)

And just for fun how all the parts come apart/fit together The radiators are just the blanks shown for now. For the detail fanatic, I am going to test a system of producing actual finned and tubed radiator cores. :) The kit will come with Photo etch parts for the faces.

I am stuck with the engine though. I need more physical dimensions of the Ford DFV engine, so I can complete the rear end. I will see if I can get that information from CTL.

Update: 8/1/09
I created the the rear top skin today, combining the top back section of the seat support. It will be easier to make this in resin and have all the shapes in one piece, which will make the build a little easier at this point. There are still some details to perfect on it, but I need it now to move on with other parts.

Unfortunately, after producing the part, it proved the rear tank access panel hole was in the wrong place, so it needed to be lowered. As I said before, luckily it is easier to correct in the software; now, when the parts are produced they will be correct.

The roll bar was the next part produced, this has great reference points to it, relative to the bodywork, the rear bulkhead, the floor pan and the inlet trumpets, as well as the head restraint and windshield. Also the position of the rear wing! It is an amazing piece having so much importance.

In the next few pictures you will see the progression. I already had the rear wing assembly done so it was easy to bring it into the main assembly and locate it in the correct position. The rear wing elements can be adjusted into any position to suit whatever race you want the kit to represent.

Update: 8/3/09
The inlet trumpets were then created and then their layout, which was then inserted into the assembly at the correct reference points. I admit it looks a little strange at this stage, but it really does help the progress. The inlet trumpets are being produced by "RB Motion" and saved me a lot of work. (Many thanks to Robert!) They are correct to scale and I already have the first sets for when the kit is ready for production.

With the inlet trumpets correctly positioned it was fairly easy to produce the "air-box bottom from there I started on the air-box top, which incidentally, is a very complex piece to produce. I am going to produce the part for the kit with the main area hollowed out and slight recesses at the front of the intakes. It will be up to you if you want to hollow out the inlets or just paint the recess black.

Update 8/7/09
I'm a happy camper today! I finally figured out how to produce a very important feature (pictures later) on the air-box inlets. I cleverly inserted the previous pictures here so you would not notice, but after approx. 3 hours of try and try again and again, plus a spark of EUREKA!. Which in turned spurred me on to look at the mounting plate for the Inlet stacks. This is kind of building the engine from the Inlet trumpets down. Once I get the engine dimensions I want, it SHOULD all go together very nicely. :)

There is still a lot to do, but it is moving quicker now. Of course I'm busy writing all this and I just realized that no one is able to see this yet. I will put a link from the old build diary.

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