User:Timothyrfries/enes100/Project 1

Write problem/project Goal
The problem consists of building a vehicle that is mobile without the use of wheels. This would include either a vehicle riding on a cushion of air, or a vehicle that operates on vertical take off an landing.

My First Task
I am going to spearhead setting up the team wikispace. I want to move forward on defining the project goals and discuss some basic mechanics of achieving those goals. What do we really want this thing to do? I think that a basic servo system should be able to control a rotating fan system. RC car front servo control split in half with shaped plasticard creating a geared system to turn both wheel mechanisms?

Summary of actual work over first weekend
We have settled on a problem statement. I launched the team wiki and put together a basic outline of the steps we will take to fabricate and test the different designs. I produced a few drawings of the craft, and through some trial and error arrived at a method of mounting the fans to the craft.

Week1 Narrative
9/17/12 - Was able to speak briefly with my group today to work on scheduling. Whipped up a design concept for the hovercraft. It utilizes three computer cooling fans for vertical lift, and another two for steering and forward thrust. I will have to test out these kinds of fans and see if they could provide sufficient lift. Putting two of them on top of the hovercraft increases the load, as does the addition of a battery pack to run them all.

9/18/12 - Met briefly with Emmanuel this afternoon. Was able to clarify my idea of the problem statement, and he and I decided to proceed with "To fabricate and test hovercraft designs, specifically comparing results using a "classic" hovercraft (air cushion) with a hovercraft utilizing vertical take off and landing through prototyping. To develop a means of forward thrust and steering that is controlled remotely."

This is what I see as a working plan for prototyping and testing:

1. Produce three fan prototype with no air cushion and test the design.

-Build a body with ducts for three fans -Install and wire the three fans and use either a battery or a variable power source that will transform AC into the needed DC voltage and current. -Initial test with it wired, then simulate the load of a battery and control fan rig -If this works (produces necessary lift), refine the design, if it doesn’t go to step 2:

2. Produce a variant that has an air cushion on the bottom to maximize use of downward thrust.

-Use the same body -Attach a cushion to the bottom, I am thinking clear plastic tarp or mylar balloon for the material. Mylar would be lighter, but probably less durable. -Test first with it just wired, then simulate battery and control mechanism load. -If test data seems positive, refine. Ideally the final design will not use an air-cushion, so move on to step 3:

3. Produce a six fan variant

-Build a new body, as by this point the other may be damaged, and retro-fitting it may reduce structural integrity -Re-wire the system for six fans -Same testing parameters as above. -Refine.

9/21/12 We have a body design, and we have fans picked out. Now we have to figure out a way to mount them. We need metal plates to mount the motors to, then we need a framework to attach that plate to the body of the hovercraft. The props have an 8” span, so I am building a prototype with an 8 ½” hole to test mounting designs. Right now I am interested in building a metal plate that the motor can be mounted to, then working out an arm structure to attach the plate to the body of the fan. The structure needs to minimally obstruct the intake for the fan, so I will be taking measurements of the fan motor today. I am thinking that soldering the arms to the plates would be better than screwing them down, as this would make it more rigid and less likely to loosen. I need to check out techniques for doing that kind of soldering. May require brazing, I am not sure. I am thinking that square brass rod should work for the support arms. It is structurally sound (doesn’t bend easily), and relatively light.

9/21/12 (cont’d) So, decided to go with wood for the brace arm instead of metal, in hopes that the wood would dampen some of the vibration from the propellers. The three motors are now mounted on the cross arms, they just need to be screwed down. I need to make sure that as each is screwed to the cross arm that we are making sure that it is level. Otherwise they will be pushing at odd angles. I have drawn up a cross-section of the mounting method for the fans and cross-bars. I will convert it into a digital format for the team page ASAP. Should be pretty stable. I am going to pick up a sheet or two of the pink foam this weekend and begin fabrication of the body on Monday. After the cross arms are installed on their mounts, I will test for stability, and if needed I will add a square brass rod across the top to make it more rigid.



My Second Task
I want to build the body of the craft and get the three fans mounted. Then I want to get a tethered power system wired and begin testing. I need to look at the specs for the fans and speedometers, and make sure that we have sufficient current/voltage to drive all three motors. The AC adapter that we were using may not be sufficient.

Summary of actual work over second weekend
I did not accomplish all of the tasks that I had intended to this week, but I did manage to get the craft body pieces prepped for assembly. I did have a chance to explore possibilities for the control of the craft, and I think that not having access to a receiver for the castle speedometers may open the door to further exploration of the arduino as a means of control. I spent some time trying to locate a basic sketch that can be modified to provide control of the speedometers, but have not found an appropriate base sketch yet.

Week2 Narrative
9/24/12: Spent some time in class laying out a measurement schematic so that when fabrication begins on the body, the measurements will be ready to go. Centering the duct holes will probably be the most time-consuming. Also discussed power requirements and methods of wiring the system with the team.

9/25/12: Went to the hardware store to pick up the pink insulation foam sheets that will form the body of the craft. The sheets are apparently only available in 8'x2' sheets, instead of the 8'x4' sheets I had anticipated using to construct the body. This size restriction necessitates having a seam in the craft body, and because the body is built of two layers of the foam, that really means that there will be two seams. These seams represent potential points of failure, either structurally or by unbalancing the craft. Structural integrity may be restored by adhering thin polystyrene sheet to the top and bottom of the craft. This would add weight, but the craft would be much more durable. Potential for a snap test?

9/26/12: Converted notebook drawing into a digital version. Added in the polystyrene sheet that I suspect is going to have to be a part of the craft design. I also did some research with the team into how we are going to control the craft. There is an RF receiver for remote control that is available through Castle, but it is $38, which puts it outside of our budgetary constraints. I noticed that a previous team working on the quad-copter project had used an arduino to control the same type of speedometers that we are using. I think that this is our best solution to use for testing, and it could probably be switched over to a wireless control system by adding a wireless breakout board.

9/27/12: I got the four main parts of the craft body cut out today. I experimented with a spray adhesive that was in the shop, but it unsurprisingly melted the sample piece of foam.

9/28/12: Stopped by the hardware store to pick up some foam-safe spray adhesive.



My Third task
This week I will get the body of the craft assembled, and test out the mounting system for the fans. Once we have a working prototype, testing will begin on the lift of the fans. I will also locate a basic sketch to modify for arduino control of the Castle speedometers.

Summary of actual work over third weekend
The layout for the duct holes and the body of the craft is complete. The first duct hole is cut, and the top edge of the craft has been beveled to reduce vertical drag. Copper standoffs were cut for the fan mounts, but they may be too imprecise to be a working solution.

Week3 Narrative
10/1/12: Adhered the four main parts of the craft body using Loctite spray adhesive. After letting the adhesive set for about 20 minutes, the body seems sound, and I do not think that the Polystyrene skin will be needed. Once testing begins, this may prove wrong, and I am somewhat concerned about the seam as an aerodynamic element.

10/3/12: Spent time beveling the edge of the craft body. The box cutter blade was too small to get a decent cut when it was in the handle, but worked much better when used on its own. This did necessitate very careful handling, and it is a tedious process. The beveling is needed to reduce drag when the craft ascends.

10/4/12: Finished beveling on the craft body. Started cutting the 1" stand offs needed to elevate the motor mounts from copper pipe using a hacksaw. I then switched to using an oscillating cutter, which does an excellent job of cutting through the pipe, but I was still not getting satisfactory results.  I don't think that any amount of finishing work will produce a stand off that has the precision needed.  I think that either pre-cut stand offs are needed, or some other method of cutting the pipe.

10/5/12: Finished laying out the duct holes for the fans and got the first one cut out. Adhering the two layers made the process less likely to break the body pieces, but cutting a curve through two layers of the foam is a bit of work, and requires significant clean up.















My Fourth task
My goal is to complete craft body construction and have a working prototype to test by the end of the week. Once the prototype has been tested, fan mounts can be constructed for the craft, and testing can begin on the craft itself.

Summary of actual work over fourth weekend
Continued work on the prototype, but work stalled when there was no way of providing an initialization signal to the ESC. Without that signal, the ESC could not provide power to the motor. Completed the team page, including a decision tree and additional photos. Completed tutorial on how to produce a Western Union splice, but I could not link to it on the team page, or even post the URL because Wikiversity has apparently blacklisted Youtube.

Week4 Narrative
10/8/12 - Continued research on arduino control sketches for the ESC. Have not yet found one that does not incorporate extensive gyro and accelerometer input. This may mean that a sketch will have to be written in order to perform an effective test of the prototype. The time frame to code and debug a sketch will probably put that outside of the remaining time for this project cycle. Will explore alternative means of powering the fans.

10/10/12 - Realizing that time was short, I decided to focus on building the prototype. I attached 1.5" foam feet to the corners of the prototype to work in place of standoffs, so that the fan crossbar could be mounted directly to the foam. Attempted to power the motors using the RF receiver power leads.  The motor would start spinning at speed, but would start making a grinding noise after a second or two.

10/12/12 - Resumed trying to power the prototype. Switched out the ESC for one that works with a brushed motor (Zagi 5) by splicing the input power leads to the AC adapter. Attempted to use an RF receiver that was in the shop and an RC controller, but the battery was dead in the controller. Could not find a compatible charger. I also could not locate a variable power supply that would operate at a low enough level of voltage and current. Would have considered scratch building one, but time was short. This concluded the production stage of the project for this cycle. Took pictures of the craft body as it is.

10/14/12 - Took pictures of the prototype and the power rig. Drew a decision tree for the project and added it to the team page. Extensive updating of the team page, including the story, and added quite a few pictures.



Complete Team Page
Hovercraft Project Page