RH Magneto Problem Solved

 

The new distributor cap and rotor arrived.  The mag. checked good with my little fixture.  I've reinstalled and timed it on the motor.  I got to taxi the plane for 5 minutes warming it up.  The magneto had no drop at 1700 RPM.  You could here the motor running smoother right from the start.  Great day all around.  I won't fly it until I get back from visiting my parents and a trip to the Antique Fly-in in Blakesburg, Iowa.  I'll be back in about a week.

Right Hand Magneto Problem

 I removed the right magneto and harness so I could bring it home to see what's the problem.  I decided I needed to run the magneto so I could see if all the plugs misfire or is it just one or 2.  To do that I needed a way to run it at various speeds while watching the plugs fire.

The plan was simple create a holder for the plugs in 1-3-2-4 firing order, ground it to the magneto and spin the magneto with a variable speed drill motor.

The holder is a piece of 1 1/2" x 1/16" aluminum angle with 3/4" holes for the plugs.  

To create threads, to assure a good ground on each plug, and keep the secure during testing, I used a piece of 0.025" aluminum bent 90 degrees and riveted to the angle. The threads are just a 1/8" hole with a split for it to bend like a Tinnerman nut.  There is a small 1/16" chamfer on each corner.  You push the plug in and turn to engage the threads.  Hey it works!

I took the cotter pin from the gear retainer nut so a 9/16" socket could hold it to spin, clockwise.  With the help of some adapters I got it connected to the drill motor.

You can spin it slow enough to watch each plug fire or all the way to 2700 RPM, full throttle.

At very slow speed you feel each magnetic pulse as the field builds and falls for each plug to fire.  I could also see that plugs 1 and 4 fired every revolution, 2 and/or 3 however missed very often, which is why at first I thought I had reversed those 2 wires at the distributor cap.

At high speed they seemed to all fire, but not so.  We took this picture while running at high speed hoping to see at least 1 plug firing in the picture.  As it turns out the shutter was open long enough to get at last one full cycle 1-3-2-4.  It caught 1 and 4 firing, and 4 is bright enough it looks like more than one firing.  Two and 3 are not firing, which is consistent with with the firing at slow speed.

I've ordered a new rotor and distributor cap.  We'll see what happens when they arrive.

Left Brake Fixed

 

You can see the wet brake fluid on the brake puck, not good.  The bladder clearly ruptured.  It appears they haven't made any bladders since WWII.  Thanks to the war effort there was a lot of surplus.  As a result no one makes new bladders.  Grove does make some nice disk brakes to replace these for $920, a little out of my budget.

Fortunately a friend, Bernie Estes, had a couple CUBs in the past.  I rebuilt the wings for one of them.  He had put Groves on the other one 10 years ago, and still had the old brakes in his hangar.  Don't you just love people who keep useful things.

I used the best parts from mine and one of his to put together a good brake.  Maybe some day I'll switch to Groves.

I had trouble getting all the air out when I made the new brake lines so I got a syringe from the farm co-op.  It worked fine but the bladder itself wouldn't take any fluid.

Once I had the brake hooked up I used the syringe to fill the line from the bladder to the bleed valve.  Then I pumped fluid from the valve to the brake cylinder under the cockpit floor.  That worked, no air in the lines.

The wheel's back on and the brakes work great while taxiing the plane.

Now I need to solve the magneto problem.  I've removed the mag.  If I can't fix it with the parts I have I'll order all new from Fresno before I head to the AAA fly-in in Blakesburg.

Spark Plugs, Rain, Tie Down for Starting Motor, Throttle Cable and Brake Problems

 

I couldn't find a reason for the miss with the RH Magneto so I replaced the spark plugs with new Champion REM40E plugs.  I also replaced the plug leads with new wires from Fresno Air Parts.  I had one wire which, in the past, had rubbed through the insulation against the cowl bump so I wanted to change them anyway.  Th new ones have elbows to help protect against chafing.

As I got ready to run the motor the rain started so I quickly covered the cockpit.

You can see the wheels are chocked with ropes that allow pulling both chocks as one.

The tail is tied to a piece of rebar which goes into a tube in the ground and through an eye bolt in the hangar door.  The guy before me install them for his plane.

I made a 1/2" rope, about 5 feet long, with eyes spliced at each end.  I used 3/8" eyes because they fit the rope better.  The wrap at the end of the tucks is heat shrink tubing.  The forward end hooks to the cockpit operated tow hook.  Start the motor, pull the chocks, climb in, buckle up, and release the hook and you're ready to taxi.

Fortunately I did some more taxiing and found my foot was catching the throttle cable and reducing power, not good.  I've added some more cable ties so it's tight to the fuel line and my foot can't snag it.

When I came back the next day I found brake fluid leaked on the floor from the Left Brake.  The old bladder had sprung a leak.  I need to find a good cheap bladder or replace the brakes, big $$.

O yeah! I still have the magneto miss.

Motor Runs - Taxied Around

 

I put some yellow and red heat shrink tubing on the gas gauge wire so I can tell if I'm too low on fuel to be taking off.  I left a gap equal to the width of the stripes so the gauge could go lower while flying if needed to land somewhere.  It turns out it still goes into the cap fine even with the stripes added.

The motor started on the first pull with 2 shots of primer.  Oil pressure came up before I could get around the wing to check it.  Priming the pump probably helped after so many years setting.

Fred Rollins took a short video as I started to taxi.

The brakes work fine and it felt so good to taxi it around.

There was one problem the right magneto has a bad miss.  It sounds like I switched two lead wires on the distributor cap.  I'll work on it this evening when the engine has cooled.  Right now I'm delighted to have it running.

Fuel Flow Test

 The new EAA Flight Test Manual suggests determining the minimum fuel needed to assure safe flight in a full power climb.  They had a good webinar on this back in February, 2013.  They recommend flow at 150% of full power with the plane climbing at a 25 degree angle.  For the Continental C-85 that means you need flow at 12.2 Gallons Per Hour or 26.1 ounces per minute.  The climb angle part of this is to determine how much fuel needs to be in the tank so that the head pressure of that much fuel will cause flow at this rate.

The first part is to measure the flow rate to the Carburetor.  The recommended procedure is to disconnect the fuel line to the carburetor and capture the fuel flowing from the hose in a container.  That would be a great plan but I spent all this time fire proofing that hose and undoing it is more trouble than I want.  

When I did the annual Condition Inspection I had to remove the filter screen in the carburetor and remove the drain plug from the float bowl.  This gave me the idea of using the drain plug hole for the fuel exit.  I also like the idea of knowing the flow rate I'm measuring is what really gets into the carburetor.  I tried putting in a tube fitting in place of the plug, but it's not possible without removing the carb. heat box.  

Instead I used a funnel to catch the flow from the hole.  It worked well, but I had to use a bead of RTV to seal it to the bottom of the carb.  This prevented a small amount of dripping from the back corner of the carburetor.  I put the RTV on the funnel and then carefully positioned it to not get any in the drain hole.  It cleaned up well when we were done.

The next step was to create a level base for my beaker. I wanted the outlet of the funnel close to the top of the beaker so the breeze wouldn't cause any mess.

I started with a full tank and the plane in the 3 point attitude.  I wanted to know the system flowed well before experimenting with less fuel and a steeper angles.

The process is simple, just open the fuel valve, capture the flow in the beaker, and time how long the valve is open.

I put the beaker in a small tote just in case I didn't shut the valve off in time.

With a full tank I flowed 31.4 ounces of fuel in 47.37 seconds.  That works out to 18.64 Gal/Hr, well above the 150% goal.  At least we have good flow with a full tank.

In the 3 point attitude we have acceptable flow down to 3 gallons remaining in the tank.

In the three point attitude the tank will completely empty, which was my goal for assuring any water in the tank would flow to the gascolator.  With just 2 quarts above empty it only flowed 8 ounces of fuel in 1 minute, which is only 3.75 GPH.  That's way below our safe flight 12.2 GPH.

The next step was to increase the fuselage angle toward the 25 degree climb angle.  We have 7 degrees in the 3 point attitude so we need another 18 degrees to get to 25.  We know that the Sine of our 18 degree angle is the length of the opposite side of a right triangle divided by the hypotenuse.  I know, it's trigonometry. If we lift the mains with the tail wheel on the ground the distance we lift them is the opposite side and the distance between the mains and tail wheel ( 169.875") is the hypotenuse.  Ah the joys of a calculator, we need to raise the mains 52.5 inches to add 18 degrees.  Ouch, that's not easy.  For now I put the mains up on the trailer, which got us to 14.5 degrees, total angle.  We'll fly with a full tank until I can measure the max climb angle Fly Baby actually will do.

The process is now the same, open valve, catch fuel, measure time the valve is open.

We started with an empty tank and added fuel until we found how much was needed to just get fuel to flow.  With 2 gallons plus 3 quarts, fuel is just at the carb.

Then we added 1 gallon and measured the flow, 2 gallons, 3 gallons, etc.  We like data.

The result is we get to the 150% flow rate with 5.6 gallons in the tank.  I'm going to mark the fuel gauge wire, so when the plane is on the ground you can see that there are more than 6 gallons in the tank.  This leaves 9 gallons of usable fuel.  At some point I'll probably redesign the tank to eliminate the unusable fuel.  For now I'll live with what we have.  I expect the original 12 gallon CUB tank would have had about the same amount of usable fuel if we had done this test back in the 60's.

Clearly you could push flying past the 5.6 gallon minimum in level flight, but I like the idea of having enough fuel to make a safe go around if needed when landing.  I never ran the old tank this low so it's not a big change, I'm just smarter now.

A good project.

Magnetos Reinstalled

The Eisemann magnetos have a timing indicator window in the distributor cap.  It works fine if the engine is off the plane but its hard to see in the tight space between the motor and firewall.  I prefer to hook up the timing light and use it to make sure I get the magneto gear positioned correctly as the magneto slides onto the mounting stud.

I've taken to making notes on the firewall to help with things like timing angles, spark plug gap and torque.  It's easier than looking them up each time.  In the engine compartment of my car I write the oil filter number and how many quarts to change the oil.  It's very easy to just pop the hood when I get to the car parts store.

The timing marks are on the propeller hub, but they're at the bottom where it's hard to see them.  I use painters tape to give me a nice line to sight with the split in the crankcase. It makes it so much easier.

The mags are back on and timed.  I've checked to see that they are producing a spark and I can see it's happening around the top of compression on each cylinder, which reinforces that all the wires are all hooked back up correctly.

I still want to verify the fuel flow before running the motor.