Escoge tu idioma

In this section I will explain the process I have been following to create my scale models based on a real car. This is something I have been asked before many times, thus I think it will be useful for many. I also want to mention that this is not a professional method or a stipulated process that has been adopted by a certain company. Instead, this simple method will serve you to design and create pretty cool RC race cars for your own use and leisure.

Choosing the model

The first thing you have to keep clear in your head is what kind of processes are available for you to use. We all would like to use the same processes that are used in industry but this is not always possible. In the best case scenario, it would cost too much so we cannot afford it anyway. Therefore a deep understanding of our capabilities is a must, so afterwards we can identify where our manufacturing bondaries are.

Strongly related to the previous point is the level of accuracy that we need. Sometimes people tend to think in outstanding surface finishes or tolerances which are absolutely unreachable or out of range. Our dream machines are always extremely complex and designed to have an awsome performance which is not possible to reach by ourselves So again, we have to keep our feet on the ground and try not to exceed our skills.

Of course, the next step is the selection of our model. It should be something that we really like because this means motivation to finish the project. Otherwise, it will start getting boring and we will not finish it. In my personal experience, we have to be prepared to keep undergoing tasks for at least one year if we want to bring a good project to the end. Consider that one cannot work full time on a project because we all have jobs and social life to attend too. With regards to construction themes, I love cars so I have been only focused on this particular field. However, I do not rule out building an aircraft or spaceship. That must be prety cool as well. In conclusion, chose whatever you like most and this will give you an incentive to finish the project. Bear in mind that every idea has to be manufactured and this process has important restraints.

Getting the information and initial design

Initial information of the model is key for the final result and the resemblance of our craft with the real one. This task is not always easy, since we may like to build an old machine or a black project aircraft with all the problems involved in such a case.

With help of the internet, this step has usually become easier and usually there is plenty of pics and technical diagrams or characteristics. The most common diagrams we might find are blue-prints or technical drawings with some overal dimensions. In addition to the pictures this will be our starting point. It is important to note that not all the information is fully reliable, specially when talking about diagrams or pictures that may have been scaled without keeping the original size ratio.

The information from books is even better than what we can find on the internet. Book's info is usually more reliable and more specific. On the other hand, it is always hard to find a good book and normally they do not refer to our model deep enough so we can base our project on just one book. Books are specially good in common subjects, such as mechanics, engineering, mechanical design, composites, and so on. Some books I have on my favorite shelf are about mechanical design (Shigley's), vehicle dynamics, engines (common automotive engines), F1 technical books (specially Giorgio Piola's); also some catalogues on pneumatics, hydraulics, motors, tools, bearings; and of course, my university notes and handouts.

In terms of getting an accurate scale model with the right dimensions the best way is getting an official scale model. There are lots of plastic kits, from Tamiya, Revel, MiniChamps, etc. If you are thinking about building a relatively famous scale model, you will find it as a scale  model kit. They are usually not expensive so the investment is worth it. After getting the model, usually it comes disassembled, you should measure it with a vernier caliper in order to create a basic drawing. This will be useful for the next step of the process which starts getting a bit more complicated.

Some important considerations prior modeling

These measures from our model kit will be our starting point. Now we have to decide at what scale we build the model. Take this as a general rule: the bigger the model, the easier to build! Big means more space to put your hands through, easy to find industrial components suitable for it and usually the same or lower cost in terms of materials and of the-shelf-parts. As a personal advice, I prefer 1/5^th for cars but I do not rule out building something at 1/3^rd in near future.

With the scale already decided, try finding industrial components that you may want to use. Get drawings from these components too( you will easily find them on-line or by a telephone query). Just to mention some instances: rod ends, bolts, gears, metal sheet plate, composite materials, paint, stickers, tyres, motors, gas/petrol engines, remote control systems, electrical stuff, bearings, pipes and tubes, coatings, etc.

Also very important: find somebody keen to machine or build small parts for you. Sometimes we cannot manufacture a certain component because it is too complex to build or needs fine tolerances. Then you can always pay and make the part outside. In this case, cost might be a problem because manufacturing few units of a custom part is always very expensive, so its worth thinking about it when designing the model and save a few hundreds of euros.

Modeling, CAD

Once we have a scale model of our favorite car or plane, let’s move on to the next thing we need: a CAD package. I do not know how computer-friendly you are but you will definitely need to get on well with those systems at this point. I do not recommend making the drawings by hand, because these days the performance you get with a CAD package is awsome.

I have tried many different software packages (TurboCAD v3.0, AutoCAD r14 - 2007, SolidWorks 2003-2007, Inventor, ProEngineer, Catia v5, Rhino, and a bit of other ones). All of them are very powerful and we might not need that much from them, that is, with a simple CAD package it will be fine. I really like SolidWorks, which is my favorite right now. It is so simple and intuitive to use and at the same time, SW is extremely powerful in terms of 3D possibilities. I would recommend a software focused on mechanical design because there are some other packages like Rhino which are not really meant for mechanical design. There is also the possibility of downloading a free CAD software that would do the job as well.

I recommend to use a virtual 3D master assembly because this is really useful when our project starts getting complex, that is, lots of different components that are interrelated with each other in a reduced space. CAD’s greatest achieving is reducing the number of errors caused by interference and silly mistakes that one cannot avoid when working with hundreds of different bits and pieces at the same time in a 2D plane.

The first thing I do is creating a basic sketch that I use as a blueprint. You can insert this into the master assembly so you have a guide on the top reference plane. Afterwards, when modeling the 3D assembly, you can use that to place the individual parts of it.

When working with SolidWorks I recommend creating a master assembly with the initial drawing (scaled measurements) as a template. As I mentioned before, it is possible to insert a 2D sketch in a top reference plane so everything else would be placed properly according to the real model. Do not forget to magnify or reduce every single measurement you take from the scale model kit!

At this stage, you have to think about creating an assembly by a combination of different elements or creating a main body which you will then cut into small pieces. Since we already have a physical prototype of what we want to model, I think that the best option is to model the components individually, specially for cars where almost everything is attached to a chassis.

Think about a racing car. With the blueprint in place, we model the monocoque. From there, we can model a suspension reference points or sketches. With those simple things, we already have most of the hard work done. Then place the engine and wheels and that is the initial design finished. Then you can go for the detail design which takes longer.

If the object of our project is a plane or a boat, it is very likely that the best way to go is starting from a main body. In this case, you will have to split it in several parts so you can model the different parts of the assembly when it comes to detail design.

The way you chose to create the assembly will vary according to your CAD skills since there are thousands of different and possible ways. According to my experience, I would chose the one I explained about the car, while the second way looks good to me when talking about an aircraft.

Anyway, make sure you model every single part properly in the detailed design step or you will have major problems when manufacturing and physical assembly goes on. Model everything, bolts, nuts, tubes, cables. Also, some calculations will have to be made during this step. This is up to you but make sure you know what you are playing around with. Sometimes this hobby may be dangerous and this is something we have to bear in mind all the time.

After this point, will follow detailed design, lots of calculations, FEA, drawing creation, manufacturing process and assembly, testing and final product development.

Project planning

Since a project like this will take long, it is worth making a project planning. This will also give us as a reference time line so we always know what to do next. There is good software on that like Microsoft Project.

In addition, it is recommendable to create a BOM’s (Bill of materials). Usually the BOM is generated automatically by CAD package and can be transferred into an Excel spreadsheet or Acces database. We can use that to create checklists in order to assist the control of the manufacturing progress.