How to design a R/C Car like an engineer II

Hi everybody.

One week more and I think I should upload what I have done until now. I am continiuing with the R/C car design, which is going to be printed using a 3D printer in plastic.

After the first post, I was working in the 3D design and linking the dimensions to the basic parameters that I need to buy or calculate.

Why that way? Is it not easier just dimension the model and change it when you have the dimension of the elements that you are going to buy?

Well, this is how the engineers work with the software Catia. Catia, apart of being a normal/good CAD, has the option of use parameter in the design; so then I will be able to modify the parameter value and then the whole model will change to the new dimensions.

In that way, I can check different configuration or options dependidng on which elements I like, but also change thickness to see the minimum one which is going to resists all the loads.

This is the process that I am finishing now, modify all the model to make it depend in few parameters according to de dimensions I have looked up in internet.

After that, I will have to buy the elements and measure to be sure that they are exactly the size that I wanted. If some are longer or bigger, I will change the parameter value in Catia, and the whole model will change and will be now ready to be printed.

Example of the parameter of catia, with a fx symbol in the constraint

The elements that I will have to print, and I will have to buy are the following:

-Electrical Motor: One of the most basic ones. It will move the rear wheels (in this model) and make the car move. In this case it's a Brushless motor with a KV of 4300, 900 watts of maximum power, 50000 rpm of maximum speed and a voltage less than 12 V.

-ESC: Electronic Speed Control. This device will be connected between the motor and the receptor and is the element which controls the speed of the motor, and then the power that it gives. There are mechanical speed controls, but latelly almost everybody uses one electronic (at least for electric cars).

-Battery: This is like the fuel of the car; in this case electric fuel. Normally the battery is one of the heavist and largest elements in a model and could be up to one third of the weight of the model. When you are going to take one, it is important that you look carefully the voltaje and maH of it, so the car will have the endurance and the motor that you desire.


-Receptor: The control or brain of the car. THe receptor will receive the orders from the Radio in your hands to control the car in different channels. It controls the motor power (throught the ESC), but also the direction control of the front wheels of the car (trhought a servo motor).

-Servo-motor: The servomotor is the element in charge of turning the wheels to make the car turn in one side or other. There are differnt kinds, which has to be study carefully and in detail.
Other servomotor will be neded to move the FPC camera up to 180º and let the driver look in different angles.

-FPC camera: Is one of the most expensive elements of the car and will be the last in being bouht (of course because the price) there are diffirent kinds. The desire features are light, with a good wireless range and real time video capacity to the googles (or monitor). Normallyare small, light and with a cost of 300 american dollars.

Now I start with some mehcanic elements:

-Wheels: Yes, I know. I could design and print the wheels. But they could be a little pain in the us since I have to design them in two parts for the inside part and the tyre apart. Also, they are cheap, les than 20 dollars the total.
The wheels I will use are 1/10 size and 1/8.

-Spur gear and pinion gear driver: the gears, will be designing and printed. The size and characteristics will have to be calculated in the excel software.

-Bearings: of course the bearings, they cannot be forgotten. Are very important to connect static elements with the shaft of the wheels. I will use two sizes (for the rear wheels and the front wheels). I don't design them because there are many in internet, metal ones and has to be done with accurate tolerances better that the ones I will use with the printer.  I will use 2 per wheel, and I will explain other day how I will use them.

-Bolts and screws: THe other structure element, that I will use to fix the elements and as shafts. I would like t use the Metric system, although in USA is not so easy. My initial idea is using a long one M7 and some shorters M4. Also, I will need washers and nuts, many of them. The precise number will be known later in the project.

-Structure: This element I won't have to buy separaterly, is the one I will print. I include it in the list because it will be needed as part of the parameters to the 3D design.


This are the most important elements that I will have to look for and the ones I will have to configurate the design for.

The 3D model after some changes

comparative: left the new model, right the first design

Although both are very similar, I have done some changes in the model. The most imporant ones affect the rear wheels (bigger) the bearing casign, and the frame.

More changes will be appear while I am linking the dimensions with the prameters. 

Sorry that this post is much more boring than others. The next one will be more interesting.

How to create a R/C car like an engineer I

As my first step of a future Drone project, I decided to start with something a little easier, and at the same time cheaper to manufacture, as it's a R/C car. At this point, I would like to use this project as a "technology demostrator" or "experience demostrator" for me, so I can gain experience in the electronic devices and FPV camera needed for building a Drone.

The idea, although it exist already, came to me after having a dream about driving a R/C with a FPV camera. Since then , I had the idea for few month, and I consider now that is the moment to start with the project.

The original project is to design and manufacture one R/C car using a 3D printer (or the service of other's 3D printer, since I don't have one). The size would be round 1/10 scale, with a top speed around 40 Km/h (11.1 m/s).

I decided to consider the option of an individual suspension in the front, and a join suspensión for the rear wheels.

After I worked with the car for few days, I had an idea of how could be the design of the model.

first impression drawing

The motor and transmission of the car is going to be installed behind, in a rear wheel driver configuration. The structure will be close to a buggy one, and of course the direction will be in the front, using a servo motor to change the directon of the wheels. 

The battery, radio receptor and electronic speed motor control will be placed inside the frame; protected of impacts and a little of the dust,

My next step is start transforming the drwaing and idea into a basic 3D design and see the value of it.

Process of the 3D conceptual design

final basic conceptual design

Once the basic 3D design is made. Now it's turn of modifying all the constraints and dimensions making them dependient variables of some few paraments which will be the elements I have to buy (battery, receptor, motor, bolts...) and the structure parameters so the car will resist the forces that it will experiment.

Then, I will be able to see which components I will finally buy and when I change the parameters, the 3D model will automatically change...But this is work of this next week. 

I will upload all the new steps I am doing.

Take Care

Stabilizer Leg Suspension

Actually this was my first project of all that can be seen in the blog. Although I have done small projects and designs and 3D models before, this was my first serious and professional project, and the one which made me start in this world.

Novatives Original Design

The project consisted in a competition or a tender in the website of Grab Cad, where one company (Novative) wanted some help finishing the design of a Hand Truck. The Hand truck was prepare to load weights of 700 Lb, and using one stabilizer Leg, the workers could move the weights without problems for the factory.

The main problem was the Suspension of the Stabilizer Leg, which had to resist the weight of the load without brake. They thought using one spring and a Shock suspensions that it wasn't enought; that's why they were asking for help and creating this contest.

The features of the original design of Novative were the following:

The first and second images is the static anaylisis of the leg suspension, while the third are the dimensions and the value of all the parameters of their problem.

After give all the parameters, they uploaded their model (handtruck and leg suspension) so we could see them in a CAD software.

the handtruck + leg suspension opened in catia

Original leg stabilizer

here in pdf: https://mega.co.nz/#!KRhADQia!43RnBr_54sOwXRuIrD-hjFvom9tZUl6xz57lO4BpWgo

After take a look, analyse and done some operations, it was clear that the design they did wasn't able to resiste the weight and forces they wanted. specially with a shock spring that can resit 1200 Lb of force.

To finish the specifications, Novative comented that they wanted to maintanin as many pieces as the original, which meaned not modifying the design in excess.

My Design

The first thing was the operations. How is it possible that the design can resist that weight. weight that could be increased up to 900 Lb!!

The three options were the following:

-increase the angle between the shoch spring suspension and the stinger wheelleg welment.

-use two springs, one in the original position and add a second one that can take part or half of the force weigh

-A complete new design

The third option is the last of the three, because it could be used just in case the other two weren't possible or compatible with what the client wanted.

So I started with the first one, engaging the shock suspension in the rear part of the leg welmentl and in an upper place of the handtruck. This configuration started to be to complicated; adding many new pieces and probably having many problems when I would do the stress analysis.

Then, I decided to focus in the two springs shock suspension option. I could maintanin the leg welment (without modificatons) and I would just have to create a new braket that substitute the two semi-brakets of the original design.


With calculations done, I determined that the angles of the springs are 45º and 61º, as it can be seen in the folowing image.

sheet with some operations and the angles of the configuration selected

After the calculations, the two shock springs suspensions have to resist a 1200Lb force compression (the maximum permited) and the force of the conexion between the braket casign and the leg weldment is 1463.72Lb in the opposite direction.

The design has to be closed for when h rear leg is not necessary, so I added some pockets or guides that the pins could follow and let the system close.

Image of the hadntruck+rear strider  in catia (springs removed)

Image of the handtruck+rear strider wheel in close position

Due to the high values of the force, and the design, I had to added some reinforced parts in both sdes, in the rear and at the botton, so the braket casign could resist them without braking, deformating to much or cross the plastic point.

The material selected was a steel with an E of 2e9 and a poisson ratio of 0.30.

Analysis in Abaqus cae of the braket casign stress without reinforcements

Analysis in Abaqus cae of the braket casing stress with the reinforcements

Altough is not 100% finished, the improvemets are small, and the configuration was ready to a client analysis.

My design was finally the 10 best, and altohugh I didn't get the best prize, I got one lower and the satisfaction of finishing in a good position being my first design in the professional world of the Cad engineering.

https://grabcad.com/challenges/stabilizer-leg-suspension-challenge/results

As it can be seen in this link, my design had the 10th best punctuation.

Blog under construction and improvement

After take a look, I decided that the quality of the blog as a completely fail, so I am trying to take as much time as possible to improve. wait few days, and you can come back again

About Me

I am an aerospace engineer starting his career in the design and development area. With a strong vocation in the technology and the learning, I decided to create this Blog to follow all my professional, personal and tutorial projects. 

Although I am from Spain, I am living currently in the US, trying to follow the engineering life motto, in which there is no contry limits for us.

My profesional information is the follow:

Education
	Technical Aeronautical Engineering, Engine’s specialty in Universidad Politécnica de Madrid
Date	September 2005 – October 2012 (except course 2007-2008)
	Aerospace Engineering, European standard conversion degree (ects credits), in Universidad de León
Date	March 2014 – July 2014
Experience
	Field Engineer for the maintenance of gas turbines
Date	March 2013 – March 2014
Profession	Field Engineer
Functions	Supervision of the maintenance for Alstom turbines, leading groups of international mechanics, working in a variety of countries, and acting as a translator between different groups
Company	Alstom Power. Working under José Manuel Costa (Field Service Director)
	Freelance engineering designer for tenders and requests.  https://grabcad.com/pablo-301
Date	February 2014 – Until now
Profession	Design engineer
Company	Different companies (Novative, Umbra, Terrafugia…) and private individuals Stabilizer leg suspension challenge, flying car, and a Rolls Royce 250 design
Important Projects
	Overhaul of a gas turbine GT26U3 (GT27) in the Alstom’s test center, Birr (Switzerland)
Date	August 2013 - September 2013
Client	Alstom Power Service
Duties	Supported the maintenance, worked in an international group assembling the gas turbine, and maintenance of the Alstom generator
	Overhaul of a gas turbine GT8B (III), Luanda (Angola)
Date	October 2013 – December 2013
Client	ENE (Empresa Nacional de Electricidade)
Duties	Managing various groups of Angolan mechanics to complete the maintenance of the Gas Turbine, translating orders between Asltom Switzerland and ENE workers, acting as a temporary director of the mechanic department, supporting the commissioning department, and communicating directly with the client to outline the goals and objectives of the project
	Emergency dismantling GT26 (Group 31) Fuel Oil System and sent to Mexico, Cartagea (Spain)
Date	February 2014
Client	Gas Natural Fenosa
	Finalist in the Novative competition for designing the Stabilizer Leg Suspension Challenge.  https://grabcad.com/challenges/stabilizer-leg-suspension-challenge/results
Date	February 2014
Client	Novative
Languages
Native Language	Spanish
Other Languages	English, advanced level (C1). Oral and written. Preparing TOEFL certification Portuguese, basic level. Translator between ALSTOM Switzerland and ENE workers.
Complementary Courses
	Catia design course with Catia V5 CAD 90h. CT Academy in Madrid (Spain) Analyst and specialist course of structures in aircraft, using FEM software Abaqus, 100 h. CT Academy in Madrid (Spain) Courses as part of Alstom Training University, for the certification as lead chief engineer in maintenance of gas turbines, Birr (Switzerland)
Software Capabilities	Advanced use of Microsoft office (Excel, Word, Power Point, Visio, Project…) Comprehensive Knowledge Abaqus software in CAE area, for static cases (linear and no linear) Advanced level in Catia V5 for CAD area Thermodynamic gas turbines software GASTURB Aerodynamic software XFLR5 and XFOIL Render software KeyShot 4 Basic knowledge of Hypermesh
Personal Qualities	My personal characteristics would make me a valuable asset to any engineering opportunity that I may counter. As follows are a list of the personal qualities that I hold and find most appropriate to the engineering field: I display strong attention to detail, I am mathematically inclined, I am able to work well in teams or as an individual, I posse a strong and analytical aptitude, I am highly communicative, I have a great strength in problem solving and logical thinking, and I display intense ambition and determination to continue my education and knowledge in the engineering field.