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June 8, 2003
I am finally at the point where I can begin to build the cabinet!  This weekend I built a new speed controller based on a PIC16F877.  This is far more advanced that my first one and this one runs cool.  It works perfectly.  Using this PIC with it's analog inputs and dual hardware pulse width modulation, the speed controller is much improved and yet relatively simple.  I determined that the last one I built using conventional (old) technology had problems with the mosfets overheating due to a long slew rate.  It just means that it would take several hundred microseconds to turn on the mosfets while they were being driven with a pulse width modulated signal.  In that time, the mosfets generate heat.  Adding more mosfets in parallel just caused further slewing.  With the PIC, slew rate is minimal.  So much so I was able to use one mosfet per channel instead four.  The controller has three potentiometers for;

• Fine speed adjust motor 1 (for matching motor speed)

• Fine speed adjust motor 2 (for matching motor speed)

• Master speed adjust (single adjustment allows for a range of propeller sizes and machine performance)

Another major change is in the works.  I have cut off the counterweight and experimented with a straight/adjustable counterweight.  My goal was to get rid of the non linearity in the helicopters' apparent weight with respect to altitude, and to try much greater dampening.  I am delighted with the results.  Making the counterweight straight stabilized the helicopter immensely.  Extending the weight dampened the helicopter significantly, essentially slowing its rise and fall speed.  I was always worried about doing this because I was afraid the effect of true flight would be lost.  In reality, the helicopter is so powerful and so responsive, there was a huge amount of room left for dampening.  Now, firing the laser gun, dropping a bomb and picking up the jeep are no problem.  Yet the helicopter is still fast and exciting.  To keep the counterweight from striking the slip wire that connects to the jeep, the slip wire has been bent a bit.  

The final counterweight is now being manufactured at a machine shop.  It will be about 30% heaver than the last one.  It will be a double counterweight made of two 4" pieces of 1.25" solid metal rod.    They will be mounted at a right angle to the pivot arm and will be adjustable because they will be threaded onto a 3/8" rod.  With this change and the tremendous range of adjustments incorporated into the speed controller, this machine can be mechanically and electrically adjusted for a wide range of performance.  Now I believe that this game could be used commercially.  With these changes, I have made use of the tri props I bought some time ago.  Now they work great and they look great.  It's really fun to pick up the jeep because you can precisely hover and creep up to it. Check out the latest video showing the basic functions of the helicopter. (right click then choose "Save as" to download)

Next, the cabinet!

June 14, 2003
I'm still waiting for the counterweights to be completed at the machine shop.  It's time to start building the cabinet.  I generated a concept design in Corel Draw.  I've never seen a cabinet like this but I feel it is a practical an achievable design.  The legs, controller and coin door I have from the original game.  The cabinet will be made using high quality birch plywood.  The paint and color scheme are undecided at this time.  The glass will be extruded 1/8"acrylic.  I think the curved front will be sharp.  I struck a deal with a company I do electronic design for where I can build the cabinet in their shop and get their help.  I am a fair carpenter at best so this deal will ensure the cabinet is professionally manufactured.  It has to be strong, as light as possible and most importantly, look crisp and impressive.  This should be fun.  I'll likely get started next week.  I've found a supplier for the acrylic, bought a 12V, 30 Amp power supply from Ebay and am about to purchase the cabinet materials.  One thing that does concern me is the possibility of the adverse effects of turbulence once the chopper is enclosed.  I may be wise to experiment with how close I can have the acrylic to the helicopter's rotors.  I'm hoping I can have them as close as 1/4" to minimize the size of the cabinet.  The cabinet's width will be about 54 inches with a depth of perhaps 60 inches not including the controls.  Below, I've posted the design and software for the PIC based Speed 400 dual motor controller.  It's simple and works great.  What I Iearned about building a motor speed controller is;

• Choose mosfets with very low RDSon (on resistance).

• Use components with minimal slew rates and low capacitance.

• Use aggressive noise suppression techniques.

• Use a PIC for ease of design, minimal components, minimal cost, etc.

June 22, 2003
The machine shop completed the counterweights and a bottom plate for the pivot tower.  I built the adjustable counterweight assembly and a box which elevates the pivot tower by 4 inches.  I'm very happy with the results.  I think the dual counterweight design looks good.  I made them as 2 parts to minimize the width and thickness of the overall counterweight so that they would not infringe on the slip wire for the pick-up object. Each counterweight measures 1/25" X 4".  Together they weigh about 2.8 lbs.  Each weight is threaded so that their positions can be adjusted on the 3/8" threaded rod.  They are locked in place with hex nuts.   I had a metal plate made to attach to the bottom of the pivot tower so that I could elevate the entire assembly to gain more height by raising it with a 4" wooden box.  To accommodate the greater angle of the slip wire and the pivot arm (due to the increased height), I had to trim the tower's top plate.  Since I gained 4" in height, I could afford to limit the maximum angle of the pivot arm so that the counterweight does not strike the slip wire.  Overall, I still gained 2 inches of height.  I believe I have the helicopter and the pivot assembly complete now.  The results are;

• The counterweights are adjustable so that the helicopter can be highly dampened (light) or changed to make the helicopter heavy and super responsive.  Larger propellers are required when the helicopter is made heavier.

• The counterweight's minimal thickness and the added height of the pivot tower allowed me to make the slip wire straight without the counterweight striking it.

• The improved counterweight keeps the helicopter's weight constant.

June 22, 2003/PM
I had to use my 12 amp switching power supplies for a contract project so I was without one to test the chopper for the past week.  I am waiting for a 30 amp power supply that I bought via eBay.  I couldn't wait to see the results of the new counterweights, the elevated pivot tower and a few other mechanical tweaks so I used my 14.4V cordless drill battery pack.  At first it flew okay but because of the greater dampening due to heavier counterweights, I noticed the pivot arm wasn't rotating smoothly and would get stuck.  I disassembled it all and did a thorough cleaning of the ball bearings and re-lubricated everything.  It works better than ever.  I cannot see how the performance could be improved.  It is precise, predictable and powerful with a super smooth and solid feel.  I can creep over the jeep, lower the hook and take off in seconds!  As well, I was still having some problems with the serial communications locking up so that the gun kept firing.  I resolved this by adding a small ferrite toroid (spelling???), wrapping the serial line around it at the transmitter side.  Normally, you are supposed to put it on the receiver side to so that it will absorb electromagnetic noise just before the data entry point.  This did not work, however putting it on the transmitter side did.  Whatever works!  I adjusted the counterweights so that they are about 1 inch from the end of the threaded rod.  It appears I chose the correct rod length and counterweight weight for a good range of adjustment.

This week I hope to get started on the cabinet.  I have thought a lot about what I have to do to achieve the results I want.  It's going to be tricky but I think I can do a good job.  Before I start, I'll have to purchase the 1/8" acrylic and perform an experiment.  I am slightly concerned that the proximity of the helicopter's rotors to the acrylic will effect the stability of the helicopter while flying due to turbulence.  Before I commit to a cabinet size, I want to know how close I can have the acrylic without causing problems.  

Lastly, I just wanted mention too that I will not be attaching the body to the helicopter until I decide on a theme and complete the cabinet's interior landscaping.

June 23, 2003
Wow!  Three updates in 2 days!  I ordered and received a miniature remote control tank from eBay.  My theory was that I may be able to use the guts so that the pick-up vehicle would move around.  I have been experimenting with various parts from other toys and servos but everything it just too heavy, too large and usually consume too much power.  It appears however that the guts from the remote control tank will work for me.  I rigged up a test vehicle ( a truck) with a small pulley system using an aluminum slot car wheel mounted on the truck's rear axle.  An elastic goes around one of the tank's wheels and the slot car wheel, completing the drive train.  It works perfectly.  Ultimately I will permanently mount the tank's guts in the truck and replace the elastic with a much more robust O-ring.  I wanted to build something that uses a pulley drive so that there was no chance of damage to the drive train from being dropped or hit by the helicopter.  To move the truck around, I'll tap into the handheld remote control with a microprocessor.  My plan is to have the truck move seemingly randomly but stop for 3 reasons;

• To recharge at a charge point (could be more than one).

• To stop as part of it's random movement, stopping and starting and possibly reversing.

• To stop in front of a building which will then appear to blow up!

I am leaning toward the theme "US Terrorist Hunt" (In major US city) where a Chinook US Army helicopter is hunting terrorists in a major US city.  The truck will likely be a rental truck that blows up a building if you don't move it out of the way quickly enough with the helicopter!  Check out the test video here.  (If the video does not start after a few minutes, right click then choose "Save target as") You can see the truck move about and also see the helicopter easily pick it up.  The revisions to the counterweights work great!  Keeping the truck charged could be problematic.  I can detect a charging station and simply move the truck to it where electrical contact will recharge the batteries.  The problem is that if the helicopter moves the truck before it is recharged, it could run out of power.  Perhaps the key is to ensure that no matter what, the truck has lots of capacity left to get to a charging station.  Hence the game time and the duty cycle of the truck have to be considered.

Update! - Amazingly, the truck will run continuously for over 7 minutes on a 70 second charge!  Since each Chopper game will probably only last 3 to 4 minutes and since the truck will likely only run 50% of the time, there should be plenty of capacity left to get to a charging station under any condition.  I'm ordering 2 more tanks for spare parts.

July 2, 2003
Getting started on the physical construction of the cabinet is a struggle.  I have generated a dimensional drawing of the cabinet in order to determine the material list and the many details of the construction.  I have been flipping back and forth with respect to the overall shape of the cabinet.  I like the idea of a curved front end because of the unique shape however it complicates the construction and leaves only 2 corners at the back to add landscaping, special effects, etc..  I was a little surprised at the actual dimensions that I will need to accommodate the helicopters maximum radius and altitude.  I have to spec everything assuming that the largest rotors could be used.  Currently, the helicopter is fitted with 8 inch tri-props however 9 inch propellers could be used.  The height of the cabinet has to be able to accommodate the maximum altitude of the helicopter plus the additional height attributed to the pitching.  This works out to about 37 inches.  That's a lot of acrylic.  I want to use 1/8 inch extruded acrylic because I can bend it without thermoforming.  I am concerned however that the large height will be such that the sides will not be straight due to flexing.  I think it would be okay because 83 inches of the acrylic would serve as the front curved window.  The curve would keep the acrylic straight.  The only non-curved parts that could possibly bend would be the parts of the acrylic that makes up the sides.  This would only be 12.5 inches on both sides.  Standard extruded acrylic comes in a length of 108 inches.  I could have vertical support pieces that would allow me to cut the acrylic however I like the idea of one continuous piece. If you look at the side profile of the cabinet design, you'll notice that the rear side panels are quite large.  This is because the acrylic ends at about 15 inches from the rear of the cabinet.  I think this looks good however.  As well, the sides will serve as significant structural elements for the canopy.  The JPEG is not high resolution enough to show the dimensions of the cabinet so here they are;

• Width - 53"

• Depth - 54"

• Height 6' 4"

• Viewing Area - 34.5" (height) X 53" (width)

I will likely use a single leg on the front, tilted at a 5 degree angle however there is a possibility that I will use 2 front legs.  There is no easy way to attach the front leg(s) to the outside of the front part of the cabinet, therefore the front leg(s) will be mounted to an A-frame underneath.  

July 6, 2003
What a weekend!  I spent tons of time on the cabinet this weekend and got a lot done.  I must say that I am ecstatic with the results so far.  I was struggling with whether I should get help making the cabinet or try to tackle it myself.  I am glad I decided to do it alone.  On Friday I ordered the material and had it delivered in the afternoon.  I purchased about $400 of lumber and material including 4 sheets of Baltic birch plywood.  I started working on it Friday night and finished the base by 7:00PM Sunday night.  I am really happy with the look and stability of the base.  It is solid and straight.  See the pics below;

July15, 2003
In the past week, I have spent every available hour working on the cabinet.  It’s been tough but I am very pleased with the results so far.  The cabinet is essentially done with the exception of the clear acrylic and a few minor details. The rear corner pieces were particularly complicated to build.  They had to be very accurate, strong and removable.  I used ¾” Baltic birch for the sides and 1/2" Baltic birch for the back pieces.  The side and back are lap joined, screwed and glued.  To add further strength, I added a ¾” corner piece with the edges cut at 45 degree angles.  This piece runs vertically in front of the back and side pieces.  Jutting out of the bottom side piece is a ½” tongue.  I used a router to shave the 3’4” plywood down to the required thickness.  I then inserted threaded metal T-nuts in the tongue so that the side could be bolted on from the inside of the cabinet base.  To lock the back part of the corner assembly, I added a maple fastening plate.  This locks to the base with a nut, bolt and washers.  The corners and the fastening system work perfectly and are super strong. The best thing I did was purchase a brad nailer specifically to aid in putting on the wrap-around plywood.  Installing the plywood was a difficult task requiring me to build holding jigs.  To install the plywood, initially, I thought that I could align the top edge flush and then trim the bottom as required.  As it turned out, if there is any ever so slight misalignment between the top and bottom plates of the base, the plywood will not go on perfectly parallel and straight.  This was the case and as such, I had to edge trim the top and bottom edges of the plywood.  I used a 1/2” edge trimming router bit with a ball bearing guide.  I made a couple of mistakes that required some timely repair work but in the end, it looks nearly perfect.  Here’s is run down off the process I used to mount the skirting;
 

• I cut two lengths of the ¼” plywood, 16” wide.  The profile of the cabinet base is such that it is 13” thick at the back and 9” thick at the front. 

• I pre-fitted the skirting by clamping one end to the center of the front using a maple jig that I screwed to the front, center of the cabinet nose.  I then pushed the plywood against the edge of the plates and adjusted it’s height so that there was plywood above and below the base plates.

• I drew lines so that I could index the plywood in the same position after removing to glue.  I also drew lines that showed me where to brad nail.  This included the edges of the top and bottom plates and various vertical wood spacers.

• I glued all of the edges on the base that would be in contact with the plywood.

After re-clamping the plywood to the front edge, my wife helped by pushing the plywood snug against the base plates while I brad nailed starting from the front and moving to the back.

• Once fastened, I edge trimmed the top and bottom edges with a router trimming bit.

• I repeated the same process on the other side.

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