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Wow, I thought you guys were using two CAS's off the flywheel teeth. I had no idea you were using the Mazda setup.
Hans
On Jun 11, 2006, at 6:45 AM, Ed Anderson wrote:
Hi Tim,
As we all know, all things break. Generally the simpler the component the less likely hood of a failure - but still possible.
The Crank angle sensor has:
1. Gear drive
2. Shaft
3. Two timing wheels
4. Two magnetic reluctance type coils.
5. Electrical Connector
It would appear that the areas most like to fail are (in my opinion) in order of likelihood:
1. Electrical connector external to the crankangle sensor housing (as related to the skill, knowledge and craftsmanship involved in making the interface between the aircraft's electrical system and the crankangle sensor).
2. Gear Drive
3. Shaft
4. Reluctance coil
5. Timing Wheels
The device is about as simple as you can get. The coils have no wear (but could possible corrode), the wheels do not rub against any component so no wear, so the highest likelihood of failure (integral to the crank angle sensor) in my opinion would most likely be the drive gear. External to the sensor the most likely failure mode is the electrical connection. I personally use the Mazda stock connectors and then added a strain relief strap (plastic electrical tie) across the two connectors holding them together. If I need to take the connection apart, I just cut the plastic strap and replace it when I reconnect.
I personally have never heard of a crank angle sensor itself failing - could certainly happen, but must be fairly rare. However, it is a single point of failure so a candidate for redundancy.
But, in my opinion, there are so many other components with a higher likely hood of failure - that I am unable to get alarmed over the possible failure of the crankangle sensor. If someone should develop a flywheel/pulley add-on sensor that can be integrated with the EC2 for a "reasonable" price, I would be interested - otherwise not.
Just my 0.02 worth
Ed
Ed Anderson
Rv-6A N494BW Rotary Powered
Matthews, NC
eanderson@carolina.rr.com
----- Original Message -----
From: Timothy Peters
To: Rotary motors in aircraft
Sent: Saturday, June 10, 2006 9:52 PM
Subject: [FlyRotary] Re: Ignition Failure
Thanks Perry!
That was what I was looking for.
I didn't mention names because I didn't want things to get personal, but I guess everything is out in the open now...
Every conversion I have seen so far has some non-redundant items. One example on the Subaru side, I have seen backup ignition controllers, but all the engines I have seen only have one sparkplug per cylinder. Is redundancy needed there? I'm not certain. Normally I would say no. But I just had a plug failure strand me while riding my motorcycle. (First time ever for me... and no, it's not a V-Twin) So now it raises a red flag... there have been other red flags, but this was just the first thing to come to mind.
I do know that a 91 Porsche 911 engine had dual plugs, dual distributor, dual coils. Maybe replace the distributors with electronic ignition. Parts would be pricey though... typing out loud again.
So now I have confirmation that a crank angle sensor failure will shut down an engine. But it also appears that a crank angle sensor failure is extremely rare (difficult to quantify, but there seems to be a general consensus on this). Something else that would be interesting to find out is if failure usually occurs during operation (stress), or during idle time (corrosion, etc.). If the primary failure point is before startup, then the risk is relatively benign (not happening in the air).
I hope everyone here (and other mailing lists for that matter) continue to report their successes and failures. I have been following (and cheering on! :-) ) John Slade for a while now. I just hope you don't give up on the A/C system John, now that you have moved out of the tropics and north of the Mason-Dixon line!
Back to lurking!
-TP
----- Original Message -----
From: Perry Mick
To: Rotary motors in aircraft
Sent: Saturday, June 10, 2006 11:49 AM
Subject: [FlyRotary] Re: Ignition Failure
The crank angle sensor is a single point of failure. There is only one, so it's not redundant even if you have two controllers. However from my experience driving RX-7s (70 miles round trip to work for the last 10 years) I've never seen one fail. Haven't seen an ECU fail either. Occassionally one of my cars wouldn't start, I would unplug and then reseat the crank angle sensor connector and it would then start. I've only seen this phenomenon on one car. Probably just needed some contact cleaner.
Generally I think any problem with the crank angle sensor would mean the engine wouldn't run at all.
Might be good to have one controller running on the stock crank angle sensor and a second running from an independent sensor on the e-shaft front pulley.
You can't have redundancy everywhere. I have one cranks sensor and one ecu and my engine has never quit running in 600 hours. If you really want redundancy build a plane like a twin-engine Defiant, that can truly fly on one engine.
Perry
-----------------
I understand that it's totally natural to feel defensive in this situation. I know you may find this hard to believe, but the goal of the post is to help others reduce risk. It's not a personal attack. There's no rotary reference in it anywhere. As far as the readers know it's a piston engine. But I hope there's at least one person on this list that sees value of looking at the other causes.
The essence of the post is accurate. Doesn't matter if you are near home base or not. Ignition failure is very high risk item. An ECU that was better at self diagnoses would have greatly reduced your risk. On your car, it would be recognized immediately. Ecu would say "Hey, my cam sensor just went thru it's normal 50 pulses per revolution with the normal 5 and 8 ms. gaps. But I didn't get the normal 20 pulses and signal gaps from the crank sensor. Turn on warning lamp and crank code. Use cam sensor for timing info." You don't see value in discussing stuff like this? If you guys just used toothed wheel with pulse gaps, then the ECU could easily self diagnose.
You know what was cool on the other list? Guys came back with "confessions" of how this parallels a problem they encountered. 2 guys said, "yeah, I had partial failure, thought it was x, took off only to find it was y". Then other guys described changes they made to system that totally eliminated the risk. Some really creative stuff. Then we discussed just how risky crank sensor really is...we see one ever 1 1/2 to 2 years. Etc. Etc. Very positive experience that may save someone's life. That's the goal.
-al wick
Artificial intelligence in cockpit, Cozy IV powered by stock Subaru 2.5
N9032U 200+ hours on engine/airframe from Portland, Oregon
Prop construct, Subaru install, Risk assessment, Glass panel design info:
http://www.maddyhome.com/canardpages/pages/alwick/index.html
On Fri, 09 Jun 2006 23:30:00 -0400 John Slade <sladerj@bellsouth.net> writes:
Hi Tim,
Isn't it wonderful how stories get twisted around as they fly from list to list. Obviously this particular twisted story relates to my recent experience, so let's dilute the fun a little by adding some truth.
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