Wilson InvenTeam

Hi All,

Team members from all teams combined efforts today at Whitney from 9-12

Accomplishments:

- Members were trained in the use of the circular saw and the drill press

- We designed, fabricated, and tested a platform to evaluate turbine blade designs

- This design holds the axle internally to improve balance and alignment

- We tested three blade designs (flat (our baseline), bent at 30 degree angles, and the bent blades in the reversed direction).

- We measured wind speed and the rotational speed of each turbine at three settings of the fan.

Observations:

The 30 degree bent design was more efficient (more rpm at a given wind speed) probably due to a lower drag coefficient.

We need to standardize the position of the wind speed device.

We must also evaluate the position of the fan (height/distance, etc.) to get the most meaningful results.

We must make sure the platform is aligned properly to reduce friction on the axle.

Next steps:

- Test curved blades

- Test slotted blades

- Explore using gears to connect the turbine to generator.

- Start developing the requirements for Prototype #3.

All teams met at Whitney H.S. today

We had an opportunity to review our wind tunnel testing from last week:

- Learned how drag coefficients changed with truck body modifications

- We were able to share our measurements with the Director of Engineering at Peterbilt Truck Company (Rick Mehelic).  He was impressed by the results and gave us several suggestions to try next time we test.  Rick is behind the aerodynamic designs of the most modern trucks and has written many articles on this

- We learned about Computational Fluid Dynamics (CFD) and Bernoulli's Equation- and how they are used to predict fluid flow

- We saw how we needed to design a better air inlet system - to minimize truck drag and maximize air flow to the turbine

- We saw how just a slight change in truck drag can cause thousands of dollars in added fuel costs

The Mechanical team met Saturday at Whitney with the Systems team from 9-12.

Accomplishments:

- Fabricated and installed a wood wind deflector on the front of prototype 2.

- Fabricated and installed a wind deflector from card board to guide the wind around the turbine.

- Mounted Prototype 2 on the Ford Escape.

- Completed a slow speed trial in the parking lot.

- Completed a road test trial on surface streets- recorded wind speed, voltage, and current (Data to be reported on Friday at Design Review Presentation)

- Designed and fabricated a turbine blade holder to test blade designs. (This blade holder holds the axle internally instead of attaching the axle assembly to the end of the holder as in prototype 2.)

Challenges:

- The cardboard wind deflector was damaged at high speeds (we lost a C-clamp).  But the turbine appeared to be more efficient with the damaged reflector. (we did not continue testing after the failure, so this is an observation based on the short drive back to the school) We may need to gear our turbine to the generator in order to achieve the target voltage/current because turbine speed doesn't appear high enough when attached to the generator directly.

Next steps:

- Next Saturday we will evaluate turbine blade designs.

- We will road test various approaches to directing wind around the turbine and changing the position of the opening on the front of the deflector.

- We need to consider modifying the opening based on the wind tunnel data from the systems team.

The Systems and Electrical Engineering teams met at Whitney High School on Saturday.  It was one amazing day to say the least!  In 5 hours, a huge amount of ground was covered and we learned a lot about drag and air flow.

Accomplishments:

- learned to drill holes and cut with a dremel tool the truck air screen section

- Learned eye protection is especially important with small drill bits because they can easily shatter and splinter into eyes

- Measured and calculated the frontal surface area of a truck 

- Calibrated springs to measure drag force in the wind tunnel (F=Kx)

- Saw how excel can rapidly plot data and one can see how "good" the data is

- Using the wind tunnel, completed many drag force measurements to assess how to modify the truck air screen:

1.  Measured drag force for unmodified truck

2. Measured drag force for flat scoop with no cutout

3. Measured drag force for curved-up scoop with no cutout

4. Measured drag force with simple cutout in air screen

5. Measured drag force with scoop directing air into cutout on air screen

- Measurements were shown to agree very well with theory

- Observed air flow over the truck body for these modifications

Work accomplished by this team was at least junior college level - that's something to really be proud of.  Really, really nice work.  Thank you to everyone who helped out!

What's next:

Well, with measured drag coefficients, we now need to extend these measurements to that of a real truck.

(1) How much does the change in drag coefficient Cd affect the gas mileage of the truck? (since Cd does not depend on size)

(2) Are there more air scoop shapes we should test?

(3) What happens when the trailer is on the truck?

(4) We need to create a concept design for our end.

Electrical team:

(1) still need to plot our Back EMF vs voltage data (who has that? can you bring it to the next meeting please?)

(2) Need to understand inverters and charge controllers

(3) need to build our power distribution system

Great work you guys!!

Mechanical Team Meeting Update

Accomplishments:

- Updated Lemelson website with photos of our work (Josie/Mr. Falcone)

- Completed fabrication of the bearing/generator mount assembly

- Completed fabrication of the support structure - Completed assembly of Prototype #2

- Conducted preliminary "Proof of concept" testing of Prototype #2 using a fan (thank you Ted)

- Prototype #2 produced power under low speed conditions

Challenges:

We have previously identified problems with our axle assembly--either the axle is not straight or its not attached at the center of the turbine or both. David constructed an axle assembly, but this needs to be redesigned in prototype #3 (most likely out-sourced for manufacture).

Next steps:

- Road testing of Prototype #2 at a range of speeds

- Investigate/evaluate blade design (we think a curved design will be more efficient)

- Construct a pathway/deflector to direct the air around the turbine

- Begin making CAD (Solid Works) drawings of the final design

Accomplishments:

- conducted a conference call with Ellen at MIT to update the status of the project

- learned to use the cutting tool on the Dremel motor tool.

- modified the design of the assembly that mounts the generator/turbine to the support structure and supports the axle with bearings.

- cut the wood pieces for the mounts inserted the bearings, and held the bearings in place with brass plates.

- began drilling the holes and assembling the mounts, (1/2 completed)

- trouble shooting a bad connection in a probe wire, and fixing it.

- began wiring a test platform to measure voltage, current of the prototype from inside the car.

- soldered a set of resistors to match the resistance of the batteries that we will be charging.

Next steps:

We need to finish making the mounts, attach the mounts to the cross-members of the support structure, and complete the support structure!

Attach prototype to the car and complete low speed testing of Prototype #2

Great work!!

All teams met at Whitney from 9-12:30.

Accomplishments:

- Alligator connectors were soldered to generators wires.

- Various mounting devices for the generators were examined

- A vibration reducing generator holder was completed

- Several bearing assemblies were examined.

- A design was completed for the mount that supports the turbine axle with bearings and attaches the generator/turbine assembly to the support structure.

- We learned to operate a circular saw.

- We began fabricating the generator/ turbine mount.

Next steps:

- Complete fabrication of generator/turbine mount

- Wire a test panel to monitor voltage/current from inside the car.

- Fabricate a temporary wind shield for the front of the device

- Fabricate a temporary wind diverter to guide the wind around the turbine so that it is in contact with the turbine for a longer distance, and more energy can be distracted.

- Conduct a low speed test.

Great work guys!

All three teams (Mechanical, Electrical, and Systems) met at Whitney today, 1/23/10 from 9-12:15

This is the report of the mechanical team.

Accomplishments:

-holes were drilled in the aluminum support structure.

-the aluminum support structure was assembled

-the two generators were tested and labeled.

-connector wires were soldered to the generators the connections shrink wrapped.

-the turbine assembly was assembled (generator-coupling-axle-fin assembly-axle-coupling-generator)

-alligator clips were soldered to the amp meter and volt meter probes

-progress reports were made by each group, to members of all teams.

-received specifications/performance data from the electrical and systems teams.

-all groups worked very well together.

Challenges:

the best method to mount the turbine assembly on the support structure was discussed.

It seems necessary to have bearings surrounding the axle to support the weight of the turbine assembly so that this weight is not carried by the bearings in the generator.

Using the generators in prototype #2 we need 3000 RPM to generate the voltage we require, (12 volts), with the resistance of the battery and the motor being approximately  15 ohms, our current from each motor will be 0.8 amps.  So the turbine would produce 1.6 amp hours if the turbine runs continuously for an hour, at this rate it would take nearly 8 hours to charge just one battery).

Action items:

Before the next meeting we need to purchase bearing assemblies for sliding doors with 1/4 holes, and a power saw for cutting/finishing the aluminum support structure.

System and Electrical Team Meeting Report

Wow! Absolutely excellent progress today on all the teams!

System Team:

- Completed the building of the wind tunnel

-Installed windows and flow inlet coweling

- Completed variable speed controller for tunnel fan

(Learned about wire stripping, wire nuts, and 110 VAC wiring and grounding)

- Modified fan structure for mounting to the wind tunnel

- Constructed mount for model truck

- Very early trial run of tunnel - using smoke from a burning piece of paper

- Learned about laminar - vs. - turbulent flow and that free-exposed edges will trip laminar flow into turbulent.

Electrical Team:

- Modified electrical scooter throttle to be a force transducer

(Learned about hall effect and transistor)

(Learned the effects pull-down resistor on an IC)

(Learned how a magnet changes the source voltage on a transistor gate)

(Learned how to tell the resistance on a resistor)

(Learned how to use analog and digital multimeters)

- Learned that the stiction/friction in the scooter handle was too much to overcome

(will have to modify to put in a bearing assembly)

- Learned how to calibrate the force transducer

All teams:

- Learned the differences between a mechanical and digital electric tachometer

- Learned how to measure shaft rotation speeds up to 3000 RPM

- Learned how fast a variable speed drill motor can turn

Thank you Mr. Z for a fabulous lab to work in!

Both Systems and Electrical Teams should meet next Friday (1/22) afternoon, 3:00 if possible, Mr. Falcone's room at Wilson HS (he will confirm)

- Need to catch-up with our budgets, planning, requirments

- Need to talk a little more about the force transducer and electrical things

For our next Saturday meeting (1/23) 9:00 AM at Whitney HS, we will:

- Hook up smoker in the wind tunnel and check for turbulence

- Make any modifications  to the tunnel to make it work well

-Maybe start on preliminary small white truck mods to look at air flow sensitivity, and effects of windspeed on air flow

- Let's start testing those generators! - then let's see if we can toast a few of them! - then take apart and see how they work

- Re-try force sensor with mods