Thorp Air Command - T18.net

I think you got your moneys worth if it was rebuilt in the 1970's ! Upgrade is good to keep the fan turning !

RB

According to the engine log, this mag has a history of troubles. The other mag has 'been as faithful as the day is long'. It's probably got some condemned guts too.
Well, I just got done with a week of night shift, so I have a few days off to ponder my next step, and get back to work on the important stuff....messin' with airplanes!

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

R & R both of the beauties and you will sleep like a Scott chowing on a Hagfish !

RB

This Scott has some Scot in 'im, but I'll defer to the Fraze, official House Scot of the t-18 clan!
I make a pretty mean Hobo Stew, but Haggis is 'beyond my pay grade'.

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

Well it turns out the mag in question, a Bendix, was rebuilt about 1970, when the engine was assembled. The coil and distributor drive gear are subject to an AD from the 1970s. The points are worn down, and the top bearing is discolored. The magneto overhaul would be $700. Also it has the olde riveted impulse coupler, which is still legal, but could be up graded for $100 more.
I elected to upgrade at this point, had the mag returned to me. So I can learn a thing or 2.
I called Emagair, and ordered up a P mag with accessories, it shipped today.
I sure have been all over the board on this thing! I chose the P mag for ease of installation, and customer satisfaction. We'll see how it works out.

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

We used to run electronic ignition on an 0-290 Thorp, but it would drop 200 RPM without warning. So we dumped it and put two new slick mags on. Engine runs a bit slower, but the confidence of flying over hostile territory and hearing that Lycoming hum makes me much happier not having the electrick ignition.

We used to run electronic ignition on an 0-290 Thorp, but it would drop 200 RPM without warning. So we dumped it and put two new slick mags on. Engine runs a bit slower, but the confidence of flying over hostile territory and hearing that Lycoming hum makes me much happier not having the electrick ignition.

Hagfish ! Hootmon ! Hootmon ! Not Haggis !

RB

Brent;
Can you tell us a bit more about the elctronic ignition you had, what it was, when it was made, etc?
There are several manufacturers of electronic ignitions now, and problems seem to be fewer and farther between incidences. I think they have surpassed magnetos for reliability, and certainly for performance.

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

My new Pmag was shipped promptly, and I got it a few days ago. I'm pretty excited about getting a few days off so I can install and test it on 'Feisty'.
Now I'm getting interested in electronic ignition, plus I was warned by Aircraft Magneto Service that my remaining mag, that has given no trouble whatsoever, could have a coil and a distributor gear that have AD's against them. That sounds like $700 getting yanked out of my wallet.
So I started learning about electronic ignition. Surely I can make my own?
I started thinking about the Pertronix Ignitor, which I installed on my tractor.
Then I learned about the Ford EDIC-4 distributorless ignition from the Megasquirt fuel injection site.
http://www.megamanual.com/ms2/EDIS.htm
Wow! what a basic system.
Forget the Megasquirt part. The basic EDIS-4 unit takes the sensor data from the 36-1 trigger wheel, and sets the spark sequence, firing the coils to start the engine a 0 BTDC, then as the engine exceeds 400 RPM advances the spark to 10BTDC. The coils are powered from 12 volts and are controlled by the EDIS unit, but they control dwell, providing a hot long spark, on command.
If set at 15 BTDC initial advance, it would advance to 25 BTDC above 400 RPM, right where the fixed timing Bendix Mag is set. Now slow idle with a low mass prop is possible!
This is better than a fixed timing mag, and the parts cost about $100. Now I gotta figure out how to install the hardware...

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

Scott, I looked at this one and it is very simple and interesting. Are you going to persue this? I am interested in how you do it and so forth.........Dan

Dan;
I'm measuring and making up a parts list.
I have an O-290 'Educational Engine' at home, and the magneto off 'Feisty'. I hope to make a direct fit timing sensor so I won't have to remove the prop, spacer & ring gear.

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

Keep me posted Scott.....Dan

I "Bit the Bullet" and bought the basic components on fleabay. Plus a 2.5" diameter trigger wheel out of England. The Megajolt E controller is a dedicated ignition controller for the EDIS ignition. It's only $162, and is completely programmable, so that would run the total cost over $300, but also be equal to the finest system available....if it works
http://www.youtube.com/watch?v=ih5b50NXN-4
This cheesy video shows the basic components, Trigger wheel, VR sensor, EDIS-4, coil pack, and the spark plugs zapping away at great gaps.
http://www.autosportlabs.com/megajolte-p-41.html
This link is to the Megajolt E controller that allows full timing control of rpm advance and manifold pressure to the EDIS unit.

_________________
Scott Emery
EAA Chapter 326
T-18 N18TE

This looks awful simple Scott, will you just run this on one side and the Mag on the other? Seems I read it has a limp home mode so if it decides it will quit thinkin it will set the timing and just keep on firing so it does have a form of redundancy? Correct me on this one if you would please....Dan