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.

Basic Tutorial of the Catia Gear Joint

Making the model of the pump, I realized that I didn't remember how to use the gear joint of the module Kinematics of Catia. But I didn't find any good tutorial to help me. After visit a  forum I practiced a little and remember how to do it.

For that reason, I left a very basic tutorial of making a gear joint in the Catia's kinematic module.

https://www.youtube.com/watch?v=WI89RAgbUNo&list=UUd27vKc1z4Ugxh2i5ONDRLg

Lobe Pump

As the previous model, this one I made using some drawings in the blog ELciri. This case is a lobe pump using some gears.

Basic vehicle suspension

Hi everyone. Altough I have to finish the Formula One of Alfa Romeo that I commented, I did other designs to increase my capabilities.

I found some new drawings of a vehicle suspension in the blog Elciri. So, I decided to freeze the Formula One and do some small projects to help my motivation.

This first design is clear. It is a simple suspension for a vehicle, originally for a toy or a R/C, although it can be modified to serve for a Kart or a Buggie.

If people ask me, I don't have any issue in show a tutorial of How to do it.

X-15 aircraft model

With some free time, I managed to create a 3D model in a scale of the X-15. I will see how much cost will be to print it in 3D.

It took me around 3-4 days but not working in it too many hours. As modificatins, I am thinking in a landing gear (front wheel and rear skies) and the logo of the USAF and NASA in the fuselage. I made a video in which some of the alierons and mobile surfaces are spinning.

Hopefully you like it ;)

The render I did very fast since my actual computer does not have a lot of RAM.

Flying car challenge

As part of a Grabcad challenge, I decided to be invlolved in a design of a flying car. The project or tender was promoved by Terrafugia, which wanted to see new designs in order to make the image of the new terrafugia TX-1 better.

My design was made using Catia V5, and the renders using KeyShot.

The characteristics of the design were the following:

Lift Body TF-X Car

This design is based in the idea of being able to fly. A flying car is a complex vehicle, because it is difficult to make a secure model that is able to go in a highway an at the same time can fly.

The other restrictions like the vertical takeoff and landing make it even much difficult.

For that reason, the basic design of this car is the body of the car can generate the enough lift force, so the wing does not have to be too long.

In a conventional plane, the wings are the heart of the plane, because are the only part that generate the lift force. However, the wings are almost always fixed, except in the ship based planes. Even in these cases, the wings that can be folded are design for being park in less space.

With a lift body, the wing can be reduced to the minimum, and can be easier foldable. The idea is based in some projects that improved the idea of the lift body planes like the X-24

Body

The body is made using two different airfoils, the Goettingen 561, and the 518. Both were chosen due to their flat lower side, that better to adapt in a car, and was more similar to the original drawing imagined.

These airfoils also were selected because have a really god lift features, a characteristic that this flying car will need. Being a slow plane, the lift coefficient of the airfoil is very important.

The body is designed for 4 people, two in the front seats, and to in the back seats. However, both pair of seats is more separated than in normal cars. The reason, is because between them is the place for the wings, and since the wings have to resist a good part of the weight if the car, need thickness area for the structure.

The doors are completely transparent so the passengers can enjoy the flight. The doors are opened and closed in a similar way to the Mercedes 300SL.

The body has two areas grooved so the wings can fit in the car configuration. This transition (the grooved area) has to be designed very carefully, so will not increase too much the parasite drag of the car.

The body has a lot of space to install the batteries (probably in the bottom of the body) and for the motors.

The wing

The wing is straight and rectangular. The reason for being straight is obviously the only configuration for a plane that won’t go in transonic or close to supersonic speeds.

The reason for the rectangular configuration is because it is the easiest and cheapest configuration. An elliptical or trapezoidal wing would cause more problems manufacturing.

Although the rectangular wing has more induced drag than the other two, it has more surface than the other both options, what give more lift coefficient, especially for a plane with such a less aspect ratio.  At the same time is the safest wing, because it can be controlled easier even if the plane has stall problems.

The elliptical configuration is much less safe, so I reject it, even if has the best aerodynamic features.

 The airfoil used was a NACA 4415, although in a more advanced analysis other airfoil can replaced it; especially a common body/wing airfoil.

The wings can be folded turning 90º in a horizontal axis, in a similar way to the carrier ship fighters like the F-18 Hornet.

Stabilizers

Two stabilizers inclined are installed in the rear of the car before the Duct fan. Even in high angle of attack conditions, the duct fan will sure that the air will pass through the stabilizers. The localization is provisional, so it could change after some aerodynamic analysis.

Propellers

The propellers used are a simple example, and can be changed. The simple model has 3 blades, although the number of blades cannot be chosen until some calculations are done.

The propellers can rotate 90º or even more so the car can takeoff/land in vertical.

Duct Fan

The Duct fan is going to propel the car through the air, it is installed in the back of the car, with no many interaction so the air can go through it with less problem.

One idea that cannot be said now (until some calculations) is that the position of the duct fan could help the air to be laminar for more time when it goes through the body of the car. This would increase the aerodynamic features; but it depends on many factors, and should be analyses with determination using a CFD software and a wind-tunnel.

The rear lights of the car are installed in the duct fan cage, so the other cars can have an idea of it height at night.

Other improvements and options

The first improvement is to install a solar panel on the roof of the car, that will increase the energy of the batteries, and then the range of the model.

The other improve is the configuration of the propels. The option is to use a propeller to propels the model, and two or four duct fan to lift it. The propeller has more efficiency propels a plane in different envelope of a flight.

On the other side, the duct fan is better for smaller speeds abut high rpm, with higher efficiency for vertical taking off and landing

Also I made a little and not so good looking video jajaja. The software used was Catia, which is not the best making renders and video renders. I am still improving in Keyshot to learn how to make video renders.

As a conclusion, I want to say that this design is based in the lift body idea, so the entire design has its limitations. 

Underrun truck challenge

This little project started as a challenge of the website GrabCad https://grabcad.com/challenges in which a company wanted to design a underrun truck protection.
Unfortunately, I was busy at that moment, so I couldn't participate in it. However, now with much more free time, I decided to do it by my own (without any compesation) to show how a small structure design can be done, and to show new engineer students. If I can, I will prepare a video on youtube to show step by step with all the details how I did it.

As the most important point, the company of the challenge made public the requirements of the underrun protector. All the features and requeriments are inside the next pdf file: https://mega.co.nz/#!ONggkC4K!DEhosz1uiOcregHUNwPCTLYPXKk6_LTQAem-wdBcJxQ

The most important points of the requirements are the dimensions, the load cases, the material, and the options that we can do.

The dimensions of the main protection (the beam) are a length of 2500 mm and 100 mm of width. The minimum thickness is 10 mm, but could be more.

The load values are defined by the client in three static load cases of pressure, that are distributed as it can see in the pdf or in the next image.

The first case of load is of 1,25e6 Pa, the second is 2,5e6 Pa and the third 1,25e6 Pa. 

The material selected y the customer is a normal Steel with a young modulus of 205GPa, a poisson value of 0,28 and a density of 7870 Kg/m3.

According to the customer, the maximum deformation allow is 40 mm, and the maximum stress value of 355 Mpa. The steel used has a elastic limit point of 200-250Mpa, so the value proposed by the client has sense since it is a protection devide that has to be taking out in case of an impact.

The steel a stress break point around 400 Mpa, so it represents a 1,127 of extra stress, that in my case I cannot be sure since the trucks industry is not my specialty. Taking that the extra value of stress is correct, if not it can be changed, I proceed wit the study/project.

The client also ask that the entire model must be designed in one piece, not as an assembly. The stress study could be done using one online CAE software that in my opinion is not the most accurate; so for this study I will use the CAD software Catia to design the protection, the Abaqus CAE in the Standard mode for the tress/deformation analysis and the software excel fot the mathematical operations.

Other designers during the challenge spent all their resouces in design a "cool" underrun protection. Most of then were designers not engineers, so a "cool" design is more their role. In my case, as an engineer, I prefer center the design in a protection that can resit all the client load cases, with the less material possible, and if it can be the less weight too using just one material, less volume means less weight).

For that reason, my objective is to find the minimum thickness of the beam (according with the shape of the section) that can resist the pressures.

Because start doing designs in catia and analysing with Abaqus until have the correctone would take months, the best way is to use the excel and the material mechanic to make the three load cases and determine the minimum thickness, and then check it using the computer softwares.

The next file is the excel, in which the three load cases are calculated. I compared a normal flat section with a square (empty inside) and this last one, was too strong, so the material wasted would have bee too much.

https://mega.co.nz/#!OA4HXbwS!VfPF-3lwYy9cDr2rGpuMoYUuzNqWt9WspD2WlFzcMNk

After determine the minimum thickness of 45 milimiters, I check the values using a catia model and run it using Abaqus CAE.

As it can be seen easily, if a comparation is done between the excel results and the Abaqus ones, the values are very close, showing that the protection can resit the impacts.

4 linear pistons reciprocating engine

This 3D was done for trainning myself using Catia V5, the drawing in which i based the model was taken from http://catiaeinventorconciri.blogspot.com/
The engine was render using the platform Keyshot 4

16 valves piston engine

This is a model that I developed for  a Catia course. The render is done using the Catia module of rendering.

Rolls Royce 250

This is a request of an aerospace engineer that wanted a 3D print of a turboengine RR250. The model was developed using the software Catia V5, and the renders with Keyshot 4

Contact Me

If you are navigating through this blog and you want to ask for information or doubts regarding to engineering.

If you want to ask my service for any engineering aspect in a professional way.

If you want to hire me to make a freelance work or designs.

If you want to hire me for your company (I am looking for job and I have the visa to work in the European Uniona and United States of America).

Just contact me:

Pablo Galindos Reyes

pablo.galindos@gmail.com

http://www.linkedin.com/pub/pablo-galindos-reyes/59/317/527/

https://grabcad.com/pablo-301