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Messages - mjn

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31
My engine got a 5 month vacation over the winter.  This spring when I got ready to start up, I checked the oil and found that the crankcase was 2 inches over full.  There was a 2 inch layer of clear diesel floating on the top of the black motor oil.  Obviously the only way for that much fuel to get into the crankcase was through the injector pump.  I put off plans to start the engine until after I could tear into the IP to see what the problem was.

Over the weekend I pulled the IP expecting to find lots of damage.  Instead, I found a perfect pump with no obvious defects.  The pump barrel and plunger had a mirror finish with no scratches.  (There were some scratches on the tappet where it slid against the pump body which had not been properly deburred, but that is not related to my leak.)

Here is a schematic showing the insides of the pump and the suspect leak location.


I suspect that fuel (shown in red) is leaking between the pump barrel (blue) and the pump body (dark green).  This is not a tight fit.  The barrel slides into the body easily.  Under pressure, this will certainly leak. (The barrel is held pressed into place with the delivery valve nut not shown.)

The stock Changfa fuel tank is bolted directly to the top of the engine.  With a full tank of fuel, there is no more than 1 foot of fuel above the injector pump.  I have removed the stock tank and am using another tank located off the engine and another foot or so higher.  In the worst case, my fuel may be 3 feet above the IP.  I am speculating that the additional head is the cause of my leak.

Have others encountered leaking injector pumps?  Any suggestions for a fix?  I have considered RTV sealant, but I hate the thought of trying to get the goo into the right spot without getting it into the wrong spot.

In the meantime, I'm turning off the fuel when the engine is not running. (I should have been doing this anyway).

32
Sorry, I can't give you any more information.  The engine in the movie is not mine.  I just ran across the video and thought it would be helpful for you.

34
Waste Vegetable Oil / Re: WVO VS Biodisel
« on: April 25, 2007, 12:50:19 AM »

Has anyone tried the Dieselcraft OC20 centrifuge to clean their WVO  I have seen them on sale for 219.00 which i thought was pretty cheap and all you need is a couple of poly drums and a pump capable of 90 PSI.  I think it can operate with WVO cleaned to 500 microns to start.


There is a huge 55 page thread on the dieselcraft centrifuge over at the infopop forum.  You can read it at http://biodiesel.infopop.cc/eve/forums/a/tpc/f/159605551/m/2001011761.

I have not read the entire thread, but it does appear to work in removing debris (and water to some extent).  (It seems that much of the dewatering is happening because of flash evaporation as the oil exits the spinner jets.)

35
Waste Vegetable Oil / Re: WVO VS Biodisel
« on: April 24, 2007, 06:21:40 PM »
When talking about dewatering the WVO, what hydrogenated oils. I have about 100 gal of "creamy" fryer oil to deal with?

In theory, the dewatering procedure is the same:

  • pre-filter to remove debris which holds onto water
  • heat to about 100ºF
  • allow to settle

In practice the "creamy" VO is harder to deal with because it needs to be heated before the "pre-filter" step.  As long as your entire system has heat supplied from pre-filter to the injector, then it behaves the same as the non creamy variety. If you don't have adequate heat on the filters then the creamy oil plugs things up.

After my dewater tank, I pump through a filter before filling the tank on my generator.  That filter is not heated or insulated.  In the winter if I am running the creamy oil, the filter nearly frozen solid after sitting overnight.  I have to open the drain on the bottom of the filter and pump warm oil through the filter to thaw it out so I can fill the tank.

About a third of my oil is "creamy".  During the winter, I save it up for warm weather processing and use. 

36
Waste Vegetable Oil / Re: WVO VS Biodisel
« on: April 24, 2007, 12:12:03 AM »
When you talk about the engine being modified are just talking about a heat exchanger and possibly heating the injector line or something else?
Yes.  The "modifications" are all external, so they are not serious.  In a pinch I could put my engine back to "stock" in less than an hour.

Personally, I am heating the WVO prior to the injector pump with "hose on hose", and heating the injector line with a resistance heater.  I typically run about 190ºF to 230ºF at the injector.

Here is a schematic showing my modifications:

37
Waste Vegetable Oil / Re: WVO VS Biodisel
« on: April 23, 2007, 05:13:04 PM »
There are plusses and minuses for each:

WVO downsides:
  • WVO must be carefully filtered and dewatered
  • engine must be modified
  • engine must be started on biodiesel or diesel
WVO upsides:
  • No need to deal with deadly chemicals (Methanol,NAOH)
  • After converting the engine, there are no ongoing expenses other than filters
  • relativly simple processing
  • no need to dispose of glycerine byproduct
Biodiesel downsides:
  • You need to store and handle dangerous chemicals
  • More complex processing than WVO
  • Disposal of glycerine byproduct can be problematic
  • You are still dependent upon "big oil" because most Methanol is produced by reacting natural gas
Biodiesel upsides:
  • No engine conversion necessary
  • Simpler filtration (Most of the debris drops out in the byproduct)

Personally, the need to store and handle dangerous chemicals tipped the balance in the favor of WVO.  My filtration process is nearly handsoff.  I dump a cubie of oil into the prefilter/dewater tank.  I use waste heat from my generator to heat the WVO to aid in dewatering.  At the end of the run, I pump from my dewatering tank through yet another filter into the generator fuel tank.

38
General Discussion / Re: Casting insites
« on: April 06, 2007, 04:40:42 PM »
I do small scale aluminum casting http://martin.nile.googlepages.com/lostandfoundry where I cast my cooling manifold and direct drive adapter for my Changfa.

I have found that there are a million ways to make a mistake when casting aluminum.  For cast iron, things have got to be at least ten times worse.

I can totally understand how the foundry in India could turn out such lousy castings.  The real problem is that every person who handled that flywheel decided that "it was good enough".  The foundry worker who dug the wheel out of the sand should have noticed the flaws and dumped it back into the scrap pile.  The guy running the lathe should have gotten annoyed with the "clunk clunk clunk" as his tool kept hitting the voids in the rim.  The guy filling the holes with the plaster should have decided to not waste so much plaster.  The guy with the paint should have wondered about the 3/4 of the rim covered in plaster.





39
General Discussion / Re: Power Outages and Autostart
« on: April 03, 2007, 05:25:32 PM »
...snip...
       On your schematic, you show the steppers as 3.8A 1.4V motors.  I thought that series was 5V at 1A, if it is that low a voltage why not do a low voltage high current supply and not waste all that energy in heat?  I've got a 12 volt linear actuator so a PWM through an H-bridge is all it takes for movement, and the speed is easy to control.
...snip...
Hi DaveW,

Most of my design is based upon what was available.  I am using the limiting resistors because it was the easiest and cheapest method to use this motor with the 12V supplied by battery.  The slo-syn M061 series of motors range from 1.4 volts to 20 volts.  I would have preferred the M061-FF-206 motor because I could have driven it with 12 volts directly.  Unfortunately, the ebay auction did not give me a choice.  Buying the right motor retail would have blown my hobby budget for the next 12 months

I experimented with a chopper drive which would have elminated the limiting resistors.  It turned out that creating a 4 phase PWM in software was more complicated than I wanted to do.

In theory, the limiting resistors will only be drawing power when the motor is moving.  The governor on the Changfa will be doing the lions share of controlling the speed.  My controller will only be providing "sag" support.  If this were the only governor, then I'd be looking at a solution like your PWM driven linear actuator.  The stepper motor just can't move fast enough.


40
General Discussion / Re: Power Outages and Autostart
« on: April 02, 2007, 11:19:45 PM »
Regardless of how you do the sensor there should be some kind of sanity circuit/software in place where if the signal from the sensor disappears for longer then it would at some minimum speed it assumes something is wrong and goes into E-stop mode.
...

I'll add "Loss of Signal" to the list of stuff I need to program.  Thanks for the advice.

41
General Discussion / Re: Power Outages and Autostart
« on: April 02, 2007, 10:13:48 PM »
Hi Luismc, I haven't selected a decompression solenoid yet.  I think the door lock solenoid would work fine.  My current plan is to use a solenoid from McMaster-Carr (#69905K5).  It has a 1 inch stroke with a 74 ounce pull.

In my case, decompression is not essential for starting, but is nice.   I'm counting on using the compression release as an emergency stop mechanism.

I'm using one of these for the rpm sensor: http://www.fairchildsemi.com/ds/QR/QRB1114.pdf.  I have not yet installed it on the engine, but I breadboarded the circuit and it works just fine.  I will paint the side of the flywheel with flat black paint, and paint a white stripe in one place.  This will give me one pulse per rotation.

I considered a hall effect sensor, but I could never come up with a suitable location or method to attach the magnet to the flywheel.  I did not like the idea of using glue or drilling a hole to hold the magnet.  (I had visions of the magnet flying off and my governor driving the engine to pieces because it was thinking the engine was too slow.)

My stepper motor is a slo-syn M061 8 wire nema-23 motor with a leadscrew assembly.  I'm running the motor in unipolor mode.  The biggest problem with the leadscrew is the slow speed.  My design could be improved by using a chopper drive, but I went for ease of implementation over efficiency.  (I'm burning over 60 watts of power in the limiting resistors while the motor is running.)


42
General Discussion / Re: Power Outages and Autostart
« on: April 02, 2007, 07:06:01 PM »
I'm in the process of building a computerized controller for my generator.  I have finished wiring the controller, now I'm debugging it and writing software.  Unfortunately writing code is more like work for me so my pace is not as fast as when I'm doing something fun.   Once finished, I'll be able to close a switch at the house and the generator will start itself and warm up.  Once running, I can throw the transfer switch and the lights come back on... All without having to go out to the generator shed.

Based on following several of the threads on the subject, I am monitoring the following items:
  RPM (via optical pickup on flywheel)
  oil pressure
  water temperature
  injector line temperature
  fuel level (WVO and diesel)
  run/stop
  emergency stop

I am providing the following outputs:
  Starter relay
  decompression relay
  fuel relay (WVO/diesel)
  speed control (via stepper motor)
  glow plug relay (If I ever add one to my engine)

I'm using a stepper motor to move the speed control on the engine.  I'll be able to start the engine and allow it to warm up at a reasonable speed before raising the rpm to 1800 to generate power.

Once the engine is fully up to temperature and the injector line is at least 70ºC I will switch from diesel to WVO fuel.  On shutdown, the controller will switch to diesel fuel for a couple of minutes to purge the WVO from the system.  An emergency shutdown (low oil pressure etc...) will immediately move the speed control to stop and open the decompression lever until all rotation has stopped.

After shutdown, the controller will move the speed control back to the nominal 1800 rpm setting so I can manually start the engine in case of a dead battery or a failed controller.

Eventually I will build in a software PID controller to keep the RPM exactly at 1800 rpm (the Changfa governor is not perfect).

I am using an Atmel ATMega8 AVR cpu as the heart of the controller.  The AVR is similar to the PIC cpu.  At work, one of our customers uses AVR cpus, so I've had some exposure to using them.

Here is my first version of the schematic:


I am open to suggestions for ways to improve the system.


43
Hi Terry,

My Changfa 195 has the same "clunk" when I turn the crank by hand.

When I first got my generator hooked up, it tried to wander around.  After a few hours, the muffler cracked and needed to be brazed back together. I ended up brazing the muffler back together 3 times in 50 hours of operation.  Eventually, I found the cause of my "wandering".  When I did my initial measurements of the shaft heights of the engine and generator, I made a mistake, and was .050" off.  As a result, the lovejoy coupler was dealing with a .050" shift with every rotation.

After I installed shims under the gen head to bring things into alignment, my "wandering" and cracked muffler stopped being problems.


44
Straight Vegetable Oil / Re: Changfa Direct Injection engine
« on: March 28, 2007, 05:29:02 PM »
Your direct injection engine should not have any problems with biodiesel.

Indirect injection engines are more forgiving of inadequately heated veggie oil.  For a direct injected engine, you should be sure that your veggie oil is plenty hot before injecting.  I suggest that you pre-heat the veggie oil to about 70ºC before the injector pump and the injector line to at least 100ºC before the injector. 

45
Other Slow Speed Diesels / Re: question about changfa style engine
« on: March 28, 2007, 05:06:25 PM »
My Changfa 195 does not look exactly like yours, but mine has a similar fitting.  Here is a picture of that area on my engine:



Mine has a screw to adjust the wide open rack setting.  Turn the screw in to limit the amount of fuel injected at the "wide open" position.  Another possibility is that is the access point to actuate the injector pump when bleeding the air from the injector line.  My engine does not have an access port to actuate the injector pump.


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