There is No Joy in Mudville

Rats!

I thought I had it licked. Last night I was getting roughness in the backup system and also the primary was acting up. This morning I went out early and replaced the electronic ignition spark plugs and the engine ran great in all functions! I have been doing a lot of ground running and I have seen this plug fouling before.

I put the cowling on and called the tower and told them I would like some high speed taxis, then possibly a takeoff. Everything seemed fine until I did my run-up at the end of the runway. The primary system was strong, but when I switched to the backup the engine just sputtered and died.

I ran up and down the runway a few times, then tried it again. Same thing. I tried leaning the back-up system, then richening it. Tried all sorts of throttle settings. No joy, so I taxied back to the hangar with my tail hanging between my legs.

Rats! Did I already say that?

So now, I am officially scratching my entrance in the AirVenture Cup race. We're taking the granddaughters on a little vacation today and maybe I can figure it out when I get back.

I'm dumfluxed. I need an expert to come and help me out.

See you in a week or so.

Sam

Isn't She Lovely?

Not So Fast, Buddy Boy

Or, should I say "It's not ready, till I say it's ready".

The weight & balance is done, and I was glad to see that it came in at 696 pounds, even with all the stuff I added, including extra batteries, heavier paint job, and TWO paint jobs.

I thought I just needed to get the vinyl lettering applied and a few more little items, when go taxi. But, why should it be that easy?

I thought I'd celebrate having the canopy on by running the engine a little. I got it up to 2,400 RPM, then it started getting rough again. What's the deal with that?

Rats.

Maybe that sensor bracket is still vibrating a little. I have a plan for that. Maybe the mixture still needs tweaking. I dunno.

We'll see tomorrow.

Anyway, here's some photos of the mostly complete engine installation.





Mixture look a little rich?

So Close I Can Taste It

I am 90% though my annual condition checklist and the thing is close to being ready.

Yesterday, I hauled it over to AvTech for weight & balance. I had the help of the instructor, Karen and two A&P students, Tom & Colin. I forgot to use my camera, but Colin grabbed these with his cell phone. Thanks folks!


I was happily surprised to see it come in under 700 pounds, 696 pounds, to be exact. I was afraid I would be in the 725 range, so 696 is good, considering all the stuff I've added. We weighed all possible combinations; empty, main tank, header tank, aux tank, pilot installed, etc. I'll figure all the arms & moments later.


Just to remind me that nothing should happen too easily, I intended to taxi the Q-200 over to AvTech for the weigh-in. Unfortunately, there was interference between my air induction tube and the cowling, which resulted in causing the lower cowl to bind against the spinner. So, today I'll have to modify the tube to better fit the cowl, blah, blah, blah.

Happy Anniversary

Today, June 22, 2009, is the 10th anniversary of my one-day trip across the U.S.A. in my Q-200. I guess it doesn't seem like ten years, then again, a lot has transpired since then (the best of which, was marrying Sandy).

Here is the link to the whole story Trip Across USA It's a pretty long read, so I suggest making yourself comfortable and pouring a cup of coffee first.

Here is the radar capture for June 22, 1999 - about mid-day. As you can see I had a bit of a time picking through Oklahoma.


It really is a shame that I can't celebrate properly and go fly today, but alas, I am still trying to hash out engine problems. (I think the engine now has more power than with the old system, I just can't get my back-up fuel injection to work yet). I guess I'll commemorate it by going to the hangar and giving the old girl a pat on the vertical fin.

This little plane has been one of the most rewarding, satisfying, challenging, expensive, hair pulling, bleeding, frustrating, and funnest things that I have ever been involved with.

Here's to my little Quickie!

I Got It ! - I Get By With a Little Help From My Friends

Finally... I know what was causing my woes (besides dain bramage). How long have I been working on this rough engine problem? Two months? Three months? Four?

The problem was finally traced to vibration of the bracket that holds the pickup sensors.

Now, how did I come to that conclusion?

Several of my advisers suggested getting my hands on an oscilloscope (see the previous post). After I sent out the results of that test, two experts said that my problem was the variation in amplitude in the signal - not a phase shift, and was most likely caused by vibration.


I got hold of Don Bartlett (who doesn't like me very much) and he welded a couple of gussets onto the new bracket made by Phil Lankford and Jeff Doddridge, in California.


When I first fired it up, I could tell that things were better, but still not 100%. It ran well on the mag, but not on the electronic ignition, but the fuel injection seemed fine. Fortunately, I had experience with this and figured it was just dirty spark plugs.

I let the thing cool off for an hour, pulled and cleaned the automotive plugs, then stuck them back in.

When I fired it up it ran just great! Wow!!! Did I say great? I really meant fantastic! I brought it up all the way to 2,370 RPM, which I hadn't seen in a long, long time! There was still a slight roughness when running on the electronic ignition, but nothing like before. I think I need some bracing of the sensor bracket, but at least I know what to do!

I want to thank all you guys who were helping me on this frustrating, teeth gnashing, hair pulling episode. I'm going to take a couple of days off for a Hoskins family reunion, but I'll be back at it on Tuesday.

Thanks again, all!

More chasing

Please take a look at these two sorrowful pages of sketches of today's oscilloscope output.

The engine always starts easily and idles very smoothly. Roughness starts around 1,800 RPM. Misfiring is very pronounced, really shakes the engine, and the exhaust is momentarily black.

Page 1.

First wave is pretty much what it looks like with both the 6" and 7 1/2" wheel, at idle. With the 7 1/2" wheel there is a little more of a hump in the middle of the trigger wave. The peak-to-peak amplitude is pretty even and is about 4 volts p-p.

2nd wave. This is what it looks around 2,000 RPM. Notice that the amplitude varies greatly, from about 3 V to 7.5 V p-p. We tried adjusting the air gap from .015 to .060 and didn't see a change here. We thought maybe the variations in amplitude might be from the prop bolts and flange lugs. Just speculation.
3rd wave. Another sketch at high throttle. Here, I tried to include the trigger wave. The trigger wave, at higher RPMs, always had a greater p-p voltage than any other part of the wave, while at idle, the trigger wave was the same.


Page 2.

There always is a consistent phase shift (skipping a tooth?) at any speed. In the sketch, I am attempting to show how it would bounce back and forth. We feel this is a key issue, but have no idea why it is occurring.

We also saw that the amplitude of the wave is pretty even at low RPMs, but at higher revs the amplitude varies a lot. Click on the sketches to better read the voltage ranges.


Other things we tried and noticed:

Changed from 1 1/2" to 6" wheel. no change seen on scope.
Removed the prop bolt closest to the trigger gap. - no change
Tried a smaller diameter sensor. - a little smoother.
Degaussed the crankshaft flange. - no change.
Ran on the single magneto only. - a little smoother.
An automotive timing light flashes consistently at low RPMs, but becomes intermittent, in sync with misfiring, at higher speeds.
Installed the 6" wheel and used the 7-1/2" sensor mount bracket. This caused the sensor to kind of be extended way out from the aluminum bracket. No effect.

I sent these sketches to Tracy Crook, at RWS and he thinks that the change in amplitude is the source of the problem and what I perceived as a "phase shift" is not an issue. Given that, I will be concentrating on eliminating all vibration in the sensor mount bracket.

Sam

Chasing the Noise

I have been corresponding with several of you and thought I'd put a week-end summary into one post. First off, I'd like to thank all of you for your help and patience while I'm going at this problem.

These things had a positive effect:

• Temporarily replacing the 1/2" VRS sensor with an old 3/8" sensor. Ran a little better.
• Centering the sensor over the trigger teeth. Got another 200 RPM and noticeably smoother.
  

These things had no observable effect:

Changing from a 6" trigger wheel to a 7-1/2" trigger wheel (photo attached), and sensor mounting brackets.

• Adjusting air gap from .030" to .055"

These things had a negative effect:

• Swapping the position of the primary and backup VRS sensors

This had an unknown effect:

• "Dressing up" the two tooth gap in the 7 1/2" trigger wheel. Actually, this was a bonehead move. I'm going to attempt repair it by having a pal fill it in with weld, then reduce it, so it pretty well matches the gap on the 6" wheel. The original configuration may help alleviate the phenomenon known as "phantom tooth".
  

This was a positive fix:

• Swapping my standard trigger wheel with Lynn French's aluminum bowl and trigger wheel setup.
  

This is what I know.

• When the engine is set at 6 deg. ATC, the primary sensor is directly over the first tooth in the gap. (photo attached shows the engine set exactly at TDC.).
  
• The air gap remains consistent all around the wheel, within a couple of thousandths.
• The engine starts easily and idles smoothly.
• When at about 700 RPM, the measured timing is around 38 deg. BTDC
• When running at full throttle (2,100 for now) the timing is about 25 deg. BTDC
• At high RPMs, the automotive style timing light flashes quite intermittently at the same time the engine starts missing, indicating, to me, that the signal is getting interference.
  
• Engine now runs pretty will up to about 1,900 - 2,000 RPM

This is next:

• Borrow an oscilloscope to view the VRS sensor signal.
• Repair the trigger wheel.
• Inquire into getting a duplicate bowl, trigger wheel and mounting bracket ala Lynn French.

Again, I invite suggestions and I thank you for the help.