Upshur Engine #3 of 5. Horizontal F-Head with optional hit-n miss governor.

[Metal Butcher]

I got the #3 engine to start and run without to much fuss, and then shortly after wards a few problems developed. After about ten minutes of running the engine stalled due to a severe drop in compression. It turned out that the piston rings rotated, and their splits ended up in line with each other. The second problem was the intake valve leaking, and puffs of white smoke could be seen coming from the carburetor. I tried another intake valve and it didn't solve the problem. Then I took a very light cut on the valve seat with the valve seat cutter and that didn't help. Finally I gave the first valve a light lapping with some metal polish and that worked.

In the video you can see that the engine runs inconsistently, and the needle valve needs to be adjusted periodically to keep it running. It seems that the needle valve on this engine is more sensitive than the first two engines. Since its not in 'good' running order I'll have to look deeper into the cause of the erratic behavior this engine displays. But for now I'll set it aside and move onto getting build #4 assembled and running.

[ame]http://www.youtube.com/watch?v=Ol5Uuf6xrH0[/ame]

-MB

 

[Brian Rupnow]

You da man Rick.--Great stuff!!!---Brian

 

[doc1955]

Congrats looks like it is a mighty nice engine. :bow: :bow:

 

[lazylathe]

And yet another awesome engine!!!!!
th_wav

Love the red flywheels on this one!!

Andrew

 

[Troutsqueezer]

MB, I'm not surprised the engine painted Trout Green runs the best.

Nice work though.

 

[Metal Butcher]

I was having a problem with multiple sensor failure on engine #4, and solved the problem by insulating the entire sensor and its prongs with shrink tubing. It worked! The engine is starting and running great.

I made the same insulation change on this engine (#3) and the erratic running and shutting down behavior it was displaying for no apparent reason has gone away. I started it several times this morning and ran it without any issues.

The lesson learned with this experience is to insulate from the solder joints all the way up-and-over the entire sensor chip, past the top by 1/16" or slightly more, and seal the open end with a silicone sealant. Once it sets up you can mount the sealed sensor in any type of mount including metal, and mount it in place using whatever glue you like with out any problem.

-MB

 

[bearcar1]

Now this may be a out of the known universe idea but what if the epoxy medium used to secure the devices was creating a capacitance effect between the leads of the device and spurious signals were 'leaking' to ground potential. (?) By using heat shrink it would have eliminated the direct contact of the adhesive and the leads themselves. At the lab I worked at after college we would encapsulate some of our electronics packages in epoxy and they would sometimes become squirrelly and unstable in operation after doing so. We solved that problem by first dipping the small packages in a pot of bees wax and then potting them in the epoxy. It seemed to work and that is what made me think of it regarding what has happened here. MB it is a beautiful thing you are doing here.

BC1
Jim

 

[Metal Butcher]

Now this may be a out of the known universe idea but what if the epoxy medium used to secure the devices was creating a capacitance effect between the leads of the device and spurious signals were 'leaking' to ground potential. (?) By using heat shrink it would have eliminated the direct contact of the adhesive and the leads themselves. At the lab I worked at after college we would encapsulate some of our electronics packages in epoxy and they would sometimes become squirrelly and unstable in operation after doing so. We solved that problem by first dipping the small packages in a pot of bees wax and then potting them in the epoxy. It seemed to work and that is what made me think of it regarding what has happened here. MB it is a beautiful thing you are doing here.

BC1
Jim

I knew that setting the sensors directly in super glue was a NO-NO-due to the shrinkage. I was planning on buying a 2-part 'electronics potting epoxy' but never did, and used a regular 2-part epoxy thinking it would be O.K.. It could be the reason the sensors failed by creating a conductive pathway, or a damaging amount of shrinkage on the sensor chip or prongs. Another likely reason could be what you mention. Roy Sholl is saying its a discharge jumping to the sensor since it has a separate ground lead, and my method (regular epoxy) of mounting did not provide an adequate amount of insulation on the sensor.

Its difficult to prove the exact cause, but the insulation (just like the the wax dip you mention) appears to be the answer to the problem, at least for the moment.

-MB

 

[el gringo]

I knew that setting the sensors directly in super glue was a NO-NO-due to the shrinkage. I was planning on buying a 2-part 'electronics potting epoxy' but never did, and used a regular 2-part epoxy thinking it would be O.K.. It could be the reason the sensors failed by creating a conductive pathway, or a damaging amount of shrinkage on the sensor chip or prongs. Another likely reason could be what you mention. Roy Sholl is saying its a discharge jumping to the sensor since it has a separate ground lead, and my method (regular epoxy) of mounting did not provide an adequate amount of insulation on the sensor.

Its difficult to prove the exact cause, but the insulation (just like the the wax dip you mention) appears to be the answer to the problem, at least for the moment.

-MB

I talked to Roy Sholl the other day and he mentioned the proposed jumping problem .He proposed a fix using piece of plastic(credit card type) as a barrier and is sending a sketch of the fix.
Ray M

 

[Metal Butcher]

I talked to Roy Sholl the other day and he mentioned the proposed jumping problem .He proposed a fix using piece of plastic(credit card type) as a barrier and is sending a sketch of the fix.
Ray M

Hi el gringo. Yes he mentioned that to me also. It seems to reason that any non-conductive plastic .020 to .030" would work as a fix if you have the leads up to the chip insulated with shrink tubing.

In my case I needed to add the shrink insulation to the prongs, and when I did so I went a step further and insulated over the chip also, and on top of that I added the plastic over the entire assembly. The shrink tubing all the way up to and over the chip should solve the problem alone. Or just adding the plastic over the face of the chip.

I posted the upgrade (fix) I used on my build thread today.

Picture #393 & #394: http://www.homemodelenginemachinist.com/index.php?topic=11257.msg145021;topicseen#new

Did you also have a sensor failure, and did you insulate up to the chip leaving the face of the chip exposed?

-MB

 

[el gringo]

Did you also have a sensor failure, and did you insulate up to the chip leaving the face of the chip exposed?

-MB
[/quote]

Yes MB, I shrink small tubing over the leads, pack RTV around them (near the sensor), then shrink the larger tubing over all, carefully.
I have Roy's ignition system on eight engines. I run a 6v sla battery through his voltage regulator. The only real problems I've had were poor ground conections (I am also a mediocre elect. type :-[) and one CDI failure I sent back and was promptly replaced.
I am going to use the two coil version on the Silver Bullet when it is time and I will insulate the chip.
Ray M