Driving and Arc Welding

Sometimes you can be multitasking without realizing it.  This time I was out cruising in Ripper at night.  I had some funny electrical problems when I made right turns.  The radio would cut out, and other electrical things became intermittent.  The engine would lose ignition momentarily.  There were sparks flying out from under my hood when the electrical issues happened.  Well, this is highly concerning, and I quickly found a place to stop, and inspect things under the hood.

Once I opened the hood I was kinda disappointed that it was such a stupid failure.  Something that should not happen, but does because of vibration.  Ripper is a little sport car, with sport suspension, and gets Driven.  So, vibration is a significant thing.  Here is a shot of the battery back in January.

There are a few issues here.  The first is the hold down nuts are not locking nuts, and do not have lock washers.  The nut that remained, in front, seemed like it had some loctite applied to it, and the threads were gummy.  The rear nut was gone, and the threads were clean, no surprise there.  So, obviously we missed a spot of loctite there.  But, really, loctite is not the right way to do this.  Then there are the exposed conductors.  I think I need to call this a design issue.  There is a solid, 4mm screw, tied directly to the body, right next to the positive terminal of the battery, and also is, coincidentally, the positive terminal connected to the alternator.

In "normal" conditions the Battery Hold Down Bracket is a a couple inches away from the exposed Positive Terminal of the Battery.  So, if the Battery Hold Down Bracket is holding the battery like it is designed then the Battery Hold Down Bracket will never make contact with the Positive Terminal of the Battery.  Vibration makes Shit Happen.  It looks like the nut on the back of the Battery Hold Down Bracket vibrated loose, and came off.  This released tension on the back of the battery.  The front J Bolt held the Battery Hold Down Bracket for a while, but when it slipped loose the Battery Hold Down Bracket started moving around, the Battery started moving around, and eventually the Battery Hold Down Bracket started making intermittent contact with the Positive Terminal of the Battery.  That is when the funny things started happening.

This is shot of the front J Bolt.  The evidence of the Arc Welding is there, and this may further indicate that there was no Loctite here.  The Arcs conducted to the Bracket, and the Nut is directly adjacent to the bracket, and may have been "sticky" because it was in close proximity to the Arcing.  Similar Arc scars are on the J end of this J Bolt.

To prevent this in the future there are a couple things I have done.  Insulating the Positive Terminal of the Battery will prevent potential grounds from touching the Positive Terminal of the Battery.  The double layer of heat shrink is a good start, but I want something that completely covers the entire terminal.  Then, also, I want to prevent the Battery from getting loose in the first place.

Adding a Lock Nut, or a Jam Nut, will prevent the nuts from moving in the first place without gumming up the threads.  A couple Nuts, and some Heat Shrink would have prevented this mayhem easily.  Ripper is different from my other Toyota vehicles.  Ripper is raw, no frills...

Ripper

Split Key

 Well, this is new for me.  This is a Flywheel Shaft Key that is split in half lengthwise.  I've never seen a failure like this before.  It was mechanically curious anyway.  The metal is not magnetic, seems relatively light weight, but doesn't scratch easily, so maybe an aluminum alloy?  I thought shaft keys were made of hardened steel.  I dunno...  This was an unusual failure...

So, anyway the mower would crank good.  It seemed to be getting compression, and spark at first, and it tried to run a little.  So, I started looking at all the areas where I have seen failures before.  I cleaned the fuel system first, and flushed out the old gas.  After the fuel system clean up I tried cranking it some more.  Now it seems like it is not getting spark.  So I inspected, and tested the ignition system.  The ignition system seems to be working, so I had to dig a little deeper.  When I removed the Starter Bell on the end of the Crankshaft I found the split key.  Then it all became clear.  It's firing, but at the wrong time, like 40 degrees late.  So, anyway, I fabricated a new, steel key, put it back together, and it runs good...

Here is a shot of the Flywheel, and the Split Key before I disassembled it.  Funny how a tiny bit of metal can cause a whole lot of work..

Puffy Capacitor

 It is the hottest week of the Summer so far.  This is very stressful on your Environmental Control System.  Hotter Temperatures means the pressures go up, and the system runs a lot more.  These conditions will cause weak parts to fail.

Look at the terminals on this capacitor.  They are angled outward.  They should be parallel.  This is a visual indicator that this capacitor is bad.  It's "puffy" which in this case means that it has failed open.  When it is open no current flows.  In this case it is a Motor Run Capacitor.  With no current flowing to the Fan Motor, no air moves.  This was the Blower Motor Run Capacitor in the interior Air Handler.  We noticed that the house was getting warmer last night, and discovered that the Air Handler wasn't blowing cold air.  The Compressor, and Condenser Fan were running.  I did a little debugging last night, and found this Puffy Capacitor.  This morning I replaced it, and had the Air Conditioner running before the Sun got high...  Crisis averted...

Old Sticker Removal

 You know that bumper sticker you put on your old car, like 12 years ago, and has been cooked on to your fender for 12 years.  It seems like that would be a permanent bond, but it's not.  To liberate this old, cured adhesive is actually pretty easy.  In this example I have a piece of aluminum that has a product label on it.  I'm starting to surface finish the piece, and this label is in the way.  It's been on there for around 13 years.

There are chemicals that are specifically formulated for adhesive removal, and I hate all of them.  They are usually potent VOCs that are both flammable, and noxious.  So, what is the alternative?  Heat...  It is an electronic solvent.  How do you loosen something up at an atomic scale?  Heat...  It causes the atoms to expand, and you get mobility.  With mobility the adhesive gets gummy again, you can manipulate it again, and remove it easily.  My process is to use a heat gun, or hair dryer, and warm up the old sticker.  Then, in this case, I used a plastic scrapper to prevent gouges in the aluminum.  There is a residue of the adhesive left on the aluminum after scrapping the label, and adhesive off the part.  I use penetrating oil to remove the residue.  Then to remove the penetrating oil I'll use a degreaser like 409, or ammonia.  Now I can get back to the surface finishing...

Office Chair

 After refurbishing the original RX300 driver's seat, now I have an extra RX300 driver's seat.  Originally I got this seat because the seat in the RX300 was worn out, and covered in duct tape.  This link, RX300 Seat Renewed,  covers the work I did on the original driver's seat in the RX300.  This thread is about the spare seat that I used in the RX300 when I was working on the original seat.  So, anyway, now I've got an extra RX300 driver's seat.  I should do something with it...

So, my wife suggested that I get a new office chair at my desk.  The old chair is 25 years old, and broken in many ways.  It is so bad I don't want to publish a picture.  So, like a lot of the stuff I build there needed to be some adaptation to use the RX300 Seat in the Office Seat role.  It needs wheels, so I can roll around the house.  I need the interface between the wheels, and the seat.  Also, I need a theme to tie this automotive part into our home, and the office, so Fence Posts it is...

I want to do this cost effectively, and utilize the materials I have at hand as much as possible.  In our home we have a lot of rustic furniture that it made from aged Cedar, and in order to tie this chair into the house I am going to use big hunks of aged Cedar.  No, question there.  So, I chopped up an old fence timber, and it will become the frame for the Office Chair.

Of course I want this platform to be very strong.  The RX300 Seat is really heavy because it is a full power seat with five motor control systems.  Sure, I could have got a light weight seat, and trimmed down the size of the base, but all at a cost.  I wanted to use materials that I have at hand, but as few new parts as necessary.

But, I did have to get some new parts, all hardware.  I used 3/8" x 6" Lag Screws to put the frame together.  Then, I picked some 4" rubber casters on steel mounts, like you would find on a piece of equipment, or a big tool box.  The heavy platform holds the seat well, and together they have the heft of a high quality chair, with an advanced level of comfort.

Next I needed to connect the seat to the platform.  I like to use 1/2" hardware in my projects, so, that is the choice here as well.  The size of the platform was dictated by the mounting pads on the seat, and I had to factor in the screw paths.  All the hardware seems to fit alright.

The next task was to interface to the electrical controls.  The motors that control the positions of the seat are all 12 Volt powered.  So, I needed a wiring diagram for the RX300 seat.  This took a little digging on the Interwebz, and resulted in a similar wiring diagram for a compatible seat.

 The RX300 Seat has the motors that control the seat positions. and the switches that control the motors.  So, in order to move the seats I needed to supply 12 Volts, and Ground to the right connections on the seat harness connector that goes to the body wiring harness.  This was fairly simple, and I used a shop power supply to test the seat controls.  My little bench top power supply provided enough current to run the Slide, and Tilt motors in the seat, but not the seat elevation.  I also tried this with a 7 Amp Hour battery, and it was still deficient to run the elevation controls.

So, I need a little bigger power supply, or bigger battery, but then I should be able to use all the controls.  This is a little more work that simply buying a new office chair.  But, this is something that is customized for me, by me, and I like it...

Craftsman 21" Self Propelled Mower

 Oh look!  It's another broken small gas engine.  This one is special, well, sort of.  It's a Briggs and Stratton Platinum Engine.  It has overhead valves, which is still kinda new to me for an American made engine.  Briggs and Stratton held on to the flat head design in the small lawn mower market right up until the turn of the Century, 1997.  So, lets Rip into it...

Usually when I start debugging a small engine I want to try to start it.  Then I can evaluate things like the ignition, and fuel system condition.  On this one the Start Handle was missing.  So, I guess we are going to trouble shoot the Starting System first.  I removed the engine faring, exposing the Recoil Starter.  Then I removed a few more screws, and the Recoil Starter is removed from the engine.

I disassembled the Recoil Starter assembly, and found damage.  There is a keeper that holds the end of the recoil spring which is damaged, and it not holding the spring.  This means the starter is not working, in multiple ways.  The Pull Cord has been cut, the Pull Handle is missing, and the recoil spring keeper is damaged.  This is an indication of long use.  I was stuck here for a time looking for a part.  But then realized that I have another mower with a very similar engine, and I could borrow the starter off the good working mower to test the broken mower.  How fortuitous...

After swapping the Recoil Starter Assembly from the good working mower to the broken mower I was able to do a little more troubleshooting.  The engine cranks, and I am reasonably sure that it is getting compression, and spark.  When you pull the cord you can feel the compression stroke of the motor because the cord gets a little harder to pull periodically.  You can hear the carburetor "whine" on the intake stroke, and you can hear the exhaust exhale on the exhaust stroke.  This tells me that the rings, and bore are generally doing their job by making compression, and that the valves are sealing.  I tested the spark by spraying some Carburetor Cleaner in the intake of the Carburetor, and cranking the engine.  This resulted in the engine briefly running, and then shutting off.

With the testing I have done so far it looks like my Briggs and Stratton small engine has a fuel system problem.  The fuel is not being metered properly into the engine, and the engine will not run because of this.  The engine is not getting enough fuel to run.  This mean we have to dis-assemble the carburetor, and see if we can find a problem.  First there are two linkages we must disconnect from the carburetor.

Modern Mowers have automatic features that make the operation of the mower easier.  In the picture above is a feature that engages the choke on the carburetor when the mower is cold.  It is a thermal actuator connected to the muffler.  Its function is to push the choke open when the mower warms up.  For what we are doing here we need to remove this linkage from the carburetor so that we can remove the carburetor.  So we need to remove three screws from the muffler heat shield, and two screws from the muffler, and then we can disconnect the linkage.

While you have these exterior pieces removed from the engine you can clean those spaces you would not normally have access to.  Maintenance is largely about cleaning stuff, like the air filter, the fuel filter, and the little bits that get grimy...

The Air Cleaner Assembly holds the carburetor in place in conjunction with the bracket you see around the carburetor.  The flow connection of the carburetor is a tube, with an O-Ring.  I am beginning to like the simplicity here.  Also, it is an all plastic carburetor, and is the first plastic carburetor I have worked on.  It's kinda weird, but also makes sense to my engineering brain.

OK, now that the carburetor is detached we can get on with the task of determining our fuel system problem.  At this point I have to note that I have not found a discrete fuel filter.  Usually with lawn equipment you need a fuel filter because of the excessive amount of debris associated with lawn service.  This mower does have a large, pleated air filter, but not a fuel filter.  Maybe there is an inlet screen on the carburetor fuel inlet.

Small engines used for lawn mowers run at a single speed, and the carburetor can be simplified because of this.  This carburetor is very basic.  I think it still has idle, and run circuits, but I have to admit it is still a little mysterious to me.  There are two screws to remove the float bowl, and then inside I found what appears to be a Jet Module which contains the metering jets for the idle, and run circuits.

There are three tubes on the Jet Module, and I think that two of them are the idle, and run circuits.  Then I am assuming that the third is a vent, but I am not sure at this point.  So, I am going to clean the Jet Module, and the Carburetor in general, and then re-assemble everything, and give it a Krank...

All the bits, and pieces go back together in reverse order, just like in the old car manuals, LOL!  Easy right?  No, really this is a very simple engine, and I think if we can get the Gas to the Bang Box itz gonna Krank...

I want to note some other features that I found on this fuel system.  It has a Positive Crankcase Ventilation tube that runs from the crankcase to the air cleaner.  There is a Gas Tank Vent that runs from the top of the gas tank to the air cleaner.  Compared to other small engines I have worked on, this one has an oversized muffler.  I wear headphones when mowing, so having less external noise is good.

I also want to note some things that are not on this engine.  There is no Primer Bulb, which was once used to circulate fresh gas into the carburetor.  Also this engine does not have a user accessible throttle adjustment.  Old mowers had a throttle, and I guess these newer mowers use the governor to regulate engine speed.  New mowers are more powerful, and less troublesome, I guess...

Well, looka there...  I inspected the Jet Module carefully before I cleaned it, and it looks like the actual problem was there.  Two of the jets looked open, but the one in the middle seemed clogged.  After I sprayed with with the carburetor cleaner the "jet" in the middle opened up, and I got that warm, fuzzy feeling of success.  The two jets on the ends have metal inserts, like they are used to precisely meter fuel, while the one in the middle was just plastic, and kinda seems to be a vent tube.  I have to look into Briggs and Stratton Plastic Carburetors a little more.  OK, Happy Mowing...

Digital Logic Sequencer

 This prototype circuit is a good example of how my design process works.  The point at which I built this prototype was in the middle of the design process, and not the starting point.  The customer already had an electronic design, and wanted to have a Printed Circuit Board made.  So, I replicated the electronic design with the circuit design tool I was using at the time (OrCAD).  Then generated the Printed Circuit Board layout.  Once we had released the Gerber files for fabrication is when I decided to prototype the design while we were waiting on the fabricated Printed Circuit Boards.

My main concern is that we got all the connections that needed to be made hooked up correctly.  There was one enable pin that needed to be hooked up in order for the circuit to work properly.  I was able to stop the PCB Fabrication House before they printed the PCB, and get the extra connection added.  The Printed Circuit Board worked the first time once we had received, and assembled it.

The operation of the circuit works like this.  First is the oscillator is a Quad Op Amp, LM324, which is configured as a relaxation oscillator.  The LM324 has four Op Amps in it, so I used one for the relaxation oscillator, and the other three as buffer amplifiers.  The clock signal is then fed to a digital counter, CD4024, a seven bit binary counter, which takes an incoming pulse train, the clock, and counts the number of pulses.  The output is in binary, and there are seven output pins for the seven bits.  The high order bits (4, 5, and 6) are fed to the sequencers address bits.  The sequencer is a MC14051 Analog Multiplexor.  The address input bits select which output channel get connected to the source.  So, when you input address bits in binary order they will switch the outputs in numeric order, the sequence.  This could also be an arbitrary selection if you were to use a processor to drive the address inputs.

This prototype is typical for small electronic prototypes.  I use single sided printed circuit boards with 100 mil hole spacing, and plated with a pad per hole layout.  All the connections are made with discrete wires, in this case 26 AWG solid core wire.  Not all the components have 100 mil spacing connections, and you wind up bending legs, and modifying the board as needed to accommodate the components.  I have made hundreds of prototype bards similar to this to work out circuits, and do proof of concept work.  This one is fun because it is visual with all the LEDs.