Monday, February 29, 2016

Wiring – Doing Homework For Wiring Instillation & Modifications

A fair amount of time was spent the last couple of days prepping for the final push to put a big dent in the wiring chore. A punch list has been prepared by creating a list of action items that involve removing or installing connector pins and wiring for modifications such as additional switches for the fuel pump and left landing light, not to mention the Tosten grip switches.

One item I wanted to verify for myself was that all the grounds on the AV-50000A Control Module are common. The reason for this is because I want to ground the AV-50000A Control Module directly to the grounding block. Why? Because it will offer a good solid ground for the electrical system and should allow the Control Module to be unscrewed and tilted sideways to gain easier access for making adjustments to the trim motor speed and the multitude of audio level controls on the side of the case. However, Van’s warns about powering the system up with the Control Module unscrewed because it obtains it’s grounding though the mounting screws … but with a 14 gauge wire connected directly to the case of the Control Module, this will no longer be an issue if all the grounds are common to the case.

The electrical diagram was studied and all the grounds for every connector was identified. An Ohm meter and a couple of connector testing pins were used to first verify that the designated ground pins on ALL the connectors are common to one another. Glad to report, they are! Next a check was made to verify that without the mounting screws installed and the Control Module sitting on an insulated surface that the case of the Control Module is connected to the internal common ground. Glad to report, it is! … meaning, a 14 gauge ground wire connected directly to the case will allow the Control Module to be powered while unscrewed without damaging the unit or other components in the electrical system. So a 14 gauge ground wire was crimped onto a #6 ring connector and installed onto the case of the AV-50000A Control Module.
AV-50000A Control Module mounted along with the #14 ground wire that will be connected to the ground block on the firewall. This will offer solid grounding of the Control Module and allow the Control Module to be unscrewed and tilted to allow easier access to the adjustment potentiometers (that can be seen on the side and aft) with power applied to the unit.

A dilemma to solve is where to pick up the power for the left landing light. Those following the Blog on a regular basis know an additional left landing light was installed so the DOG Aviation RV-12 could have wig-wag lighting with no additional current penalty (since only one landing light is on at a time). However, because of the limited available power, felt it best to add a separate switch to control the left landing light’s steady on power … and only use it on short final so not to overtax the electrical system for extended periods of time. The steady on function of the landing light will draw between 2.4 to 2.8 amps depending on the battery’s voltage. Unfortunately, there are no spare fuse positions built into the RV-12’s electrical system. There is an unused “Extra” position on the AV-50001 Switch & Fuse Module that connects pin 14 of the connector on the back of the AV-50001 Switch & Fuse Module directly to the main power buss (without a fuse). An Ohm meter was used to verify pin 14 on the connector is connected internally to the main power buss ... it is. So at this point, I’m leaning towards using this location to obtain power for the left landing light’s steady on function. The current plan is to add a wire to pin 14 of the WH-00031 wire harness and run it directly to an inline fuse then over to the left landing light’s switch. This will insure there is fuse protection as close as possible to the AV-50001 Switch & Fuse Module.
A wire will be added to pin 14 of the connector on the WH-00031 wire harness that interfaces with the connector on the back of the AV-50001 Switch & Fuse Module to connect to the “Extra” circuit. A 3 or 4 amp inline fuse will be installed on the “Extra” power wire coming from pin 14 because there is NO internal fuse for this circuit inside the AV-50001 Switch & Fuse Module.

A wrench in the gears. After purchasing the inline fuse block, the electrical drawings were given closer scrutiny … noticed what I hope is a miss-print. The Van’s electrical schematic drawings show the builder the maximum amperage connector pins or circuit traces can handle. I did not notice it at first, but every place the “extra” lead is designated it is rated for 5 amps … that is except at one location inside the AV-50001 Switch & Fuse Module. There are two circuit boards inside the AV-50001 Switch & Fuse Module and the designation for the one that has the fuses on it shows a 2 amp limit for the trace named “Extra”. Yet from that point on, everything else shows 5 amps, so I’m hoping this is a misprint. To get a better visual, the back plate was removed from the AV-50001 Switch & Fuse Module and examination of the circuit board reveled the width of the “Extra” trace on the circuit board going to the connector is seemingly approximately the same as the other 5 amp circuits. At this point in time, based on what I saw, I’m feeling the 2 amp limit is a misprint … unless Van's has reduced the current rating arbitrarily because the circuit is unfused. Will place a call to Vans for clarification. I could not see all of the trace, but based on what I saw, I feel I can safely fuse this circuit to 3 amps and move on.

Return from the future: See the edit at the end of this post regarding the current rating of the Extra circuit.

If another arrangement for the left landing light steady on power needs to be made, the next easiest power source is the power for the 12 volt plug that looks like a cigarette lighter socket. It is a dedicated and fused 5 amp source for power. The most power likely to be used from the power socket would be to charge a notepad (which would be roughly a max of 2.5 amps if using a high output USB charger) so the left landing light could be powered from this available source of power … but if a notepad were drawing a full 2.5 amps, the 5 amp fuse would be at or near its limit for the duration the left landing light is on. Of course, the notepad charger could easily be unplugged by reaching down between the seats and unplugging it from the 12 volt socket so this power source is doable.

It appears I opened up a can of worms in Van’s engineering department when asking about the current capability of the extra circuit in the AV-50001 Fuse & Switch module (which appeared to be incorrectly marked on the drawing, along with other circuits). The good news … the “Extra” circuit can be used as a power source for the left landing light because it IS indeed rated for 5 amps! The bad news, I created some extra work for Van's engineering department which now needs to correct that misprint and a couple of others ... they said an updated drawing will be posted on Van’s WEB site when the corrections are made.

Saturday, February 27, 2016

Oil & Fuel Pressure Sensor Hoses Secured

The one lose end remaining after installing Aircraft Specialty’s Teflon fuel line kit and the kit to move the oil pressure sensor to the firewall was … securing the lines going to the firewall mounted sensors to my satisfaction.  As mentioned in the previous post, a mounting bracket was made but did not have the right size screw to mount the bracket onto the forward riser on the left intake manifold. Yesterday, the screw came in along with some other goodies that will be needing in the coming days. With correct sized screw in hand, proceeded to mount the oil and fuel pressure sensor lines onto the fabricated bracket … and am very pleased with the way it turned out.
To secure the two Teflon lines, two Adel clamps were screwed onto a custom made bracket that was mounted onto the forward riser on the intake manifold.
Side view of the completed instillation and securing of the Aircraft Specialty Teflon lines going to the fuel and oil sensor units mounted onto the firewall.

A note to fellow builders: The mounting location chosen for the remote oil pressure sensor is NOT the standard location ... that said, Steve at Aircraft Specialty gladly custom made a Teflon hose to reach the custom made dual sensor bracket mounted on the firewall of the DOG Aviation RV-12.

Wednesday, February 24, 2016

Mounting Bracket Support For Oil & Fuel Pressure Lines Fabricated

As could be seen in one of the photos in yesterday’s post, the two Teflon lines running over to the firewall mounted oil and fuel pressure sensors still needed securing. Figured I would need to fabricate a bracket which I was planning on saving for a rainy day. Gee, it rained today … so a mounting location was determined and a bracket was made.

Decided one of the easiest ways to secure the two Teflon lines would be to use  one of the two slotted risers on the left carburetor’s intake manifold. Have no idea what these are used for .... mounting cables perhaps. Nothing is attached to the risers in the Illustrated Parts Catalog and I’ve looked at many many photos on line of RV-12's and other aircraft using the Rotax 912 engine and have not seen anything connected to the risers. … so guess I’ve found a convenient place to hang a bracket for mounting a couple of Adel clamps. After playing around with the angles and various mounting methods decided to use the forward most riser as an attachment point for a small mounting bracket that will be skewed at a 45 degree angle for Adel clamps to mount onto. The holes in the risers are fairly large so opted to make a bushing from a piece of left over aluminum tubing so a #10 screw could be used to attach the bracket onto the riser.
A test fitting of the fabricated bushing and bracket that will support the Adel clamps for the hoses. Looking closely at the forward riser one can see the bushing that was made. For final assembly the bracket will be rotated up 45 degrees so the hoses can sit a little higher.

Discovered I did not have a spare screw of the proper length, so will not be able to secure the lines with Adel clamps today … but when the screw comes in, it will all work out nicely.

Tuesday, February 23, 2016

Finishing Touches Placed On Aircraft Specialty Fuel Lines

Today was a mixed bag of firewall forward work activities, most notably placing the finishing touches on the Aircraft Specialty Teflon fuel line instillation. Even though the fuel lines were installed, they were not yet secured to the carburetor flange bolts. Also, the rubber hose that connects the balance tube to the right intake manifold was damaged during removal of the fuel clamp block (which after removing all the banjo fittings serves no useful purpose), so a new piece of hose was cut and installed.
New piece of fuel hose to replace the piece of hose that was damaged during removal of the no longer necessary fuel clamp block (pictured in the Jan 25, 2016 posting). The end of the hose attaches to where the blue tape is protecting the port from debris.

The clamp was installed on the hose making sure the tang for installing the vibration dampening spring was positioned correctly.
Using a spring hook tool to reattach the spring from the carburetor onto the tang.

To prevent the Teflon hoses from chafing or the balance tube from being damaged by the fuel marshal, a piece of rubber hose was slit and placed over the balance tube so the fuel marshal/fuel lines can be secured directly to the balance tube.
The space between my fingers is where a piece of slit fuel line was placed over the balance tube to prevent it from being damaged by the fuel marshal when it is wire tied onto the balance tube.
Fuel marshal is now secured onto the balance tube with wire ties.

Now with the final positioning for the fuel marshal determined, attention was given to reinstalling the hose clamps on the intake manifold flanges used to secure the fuel line to each carburetor.
Both green fuel line hose clamps reinstalled onto the flanges on the intake manifold and the fuel marshal secured onto the balance tube with wire ties.

Of note: The bottom two Teflon hoses on the right in the above photo still need to be secured with Adel clamps … but first a small mounting bracket needs to be made … a rainy day project.

In doing a little more research on the torque values for the 37 degree fittings, it appears that because the new fittings are steel on steel, a higher torque value of 100 inch pounds is recommended … so the torque of all the 1/4" steel to steel fittings was increased to 100 inch pounds.

Continuing on with closing out the tasks in Section 46, the last task in the section is to remove the banjo fitting on the oil return port and install a straight adapter for flair fittings.
This banjo fitting (on the oil return port) needs to be removed and replaced with a straight adapter for flair fittings.
The Banjo fitting seen in the previous photo was replaced by this straight fitting.

Sunday, February 21, 2016

Fabricating & Installing Fuel Pump Drain Line

The task for the afternoon was to fabricate and install the fuel pump drain tube. The fuel pump’s drain tube is fabricated from two pieces of rubber fuel line and an aluminum tube which needs to receive three bends. Right off the bat a mistake was almost made in cutting the rubber fuel line … the instructions say to cut both FF-01224 and FF-01225 fuel lines per figure 1 dimensions. Figure 1 shows two fuel lines with a measurement of 2" above them. It is a good thing I looked further forward in the plans to realize the second fuel line needs to be much longer than 2" … in fact it needs to be 19".
At first glance it appears figure 1 in the upper left is showing both fuel lines are to be cut to 2" … NOT SO, the drawing is misleading, only FF-01224 is 2" … FF-01225 is cut to 19" as can be seen between my fingers.

FF-01223 is fabricated from 1/4" aluminum tubing cut to 17 3/8". Both ends of the tube are flared then the flairs are ground down to leave approximately 1/32" of a flange. Basically, the idea is making a ridge for the hose clamps … but not so high that the tube won’t fit into the hose.
The flair on the left is a normal flair … the flair on the right is after grinding most of the flair off creating a ridge for a hose clamp.
FF-10223 after grinding down the flairs ready to be shaped per the 1:1 drawing.

To make the tube as precise as possible to the drawing, I ignored Van’s radius angle given for the middle bend and used a protractor to determine that angles the bends were … from right to left they are 50 degrees, 40 degrees and 30 degrees. I started with the biggest bend on the right and worked to the left. Since the drawing is a 1:1 to scale drawing, a straight edge was used to determine where the bend begins and the tubing was marked at that spot and placed in the tubing bender at the 0 degree mark and the first bend was made to 50 degrees. The point where the 40 degree bend begins was determined and the tubing was marked at that spot and placed in the bender at the 0 degree mark and bent to 40 degrees,  checked with the protractor, then placed on the 1:1 drawing for verification.
About to make the second 40 degree bend with the tubing bender.
The first two bends are completed and the tube is adhering to the drawing very nicely.

Before making the final bend, I wanted to check the fit on the engine to see how all this is working out. Four Adel clamps are used as hangers for the tubing … two larger Adel clamps go around the forward and aft oil return tubes and are used as hangers  for the smaller Adel clamps that will secure the FF-01223 tube. To aid in being able to get the mounting screw inserted, a piece of safety wire is used to compress the Adel clamp.
A piece of safety wire holds the Adel clamp compressed … this makes it easier to install the screw and nut.

With the clamps in position, the tubing was placed in position and it looked good. I made a mark on the tubing where the aft Adel clamp would be securing it just to make sure the final 30 degree bend began aft of the Adel clamp. The tubing was removed and the last bend was made.
Completed bending of the FF-01223 tubing. It is now ready for instillation.

Prior to installing the FF-01223 tube, the 19" piece of hose was attached and secured with a hose clamp and the two smaller Adel clamps were placed onto the tube … safety wire was used to compress the Adel clamps so installing the screws would be much easier.
The FF-01223 fuel drain tube assembly ready for final installation.

Instillation of the FF-01223 tube went smooth … it was connected to the 2" hose on the fuel pump and both Adel clamp hangers were secured with a screw and nut. The 19" hose is routed between the two coolant lines aft to be wire tied onto the fuel line from the Gascolator.
Transition of the FF-01223 fuel drain line from the fuel pump to under the engine.
The FF-01223 fuel drain line traversing the underside of the engine.
The aft transition from the FF-01223 aluminum line to the 19" FF-01225 fuel drain line hose.
The  19" FF-01225 fuel drain line hose wire tied onto the fuel line coming from the Gascolator.