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Throttle Control Cable – 2 hrs

December 24, 2012 Leave a comment

Monday Dec 24, 2012

It’s Christmas Eve so I did not a lot of time on the project today but I did do some preliminary work on the throttle cable routing. First I went by the hardware store and bought a 17/64 cobalt drill bit so I could enlarge the holes in the eyeballs for the throttle cable which is .265 diameter. Then I drilled out the eyeball, installed the cable and began messing around with the routing while trying to figure out where to mount a bracket to tie down the control cable just before the servo. There are many variables to play with including the amount of thread engaged with the spherical rod end, the location and angle of the bracket, and the hole in the servo control arm selected. Initially I was using the outer hole in the control arm but I found that the extra motion was causing the cable to come up short at the instrument panel bracket. I think this cable is just barely long enough. I moved the spherical bearing to the inner hole in the control arm and adjusted the nominal angle of the arm so that the cable is perpendicular to it at the mid point of the throttle stroke. You can see that in the two pictures below. The first is at full throttle and the second is at idle. Note the angle of the control arm relative to the control cable. They are perpendicular half way in between these two positions.

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I also adjusted the tie down bracket to get the most clearance I could between it and the engine mount tube. There is about 1/2 inch clearance in this configuration. I think that is enough to allow for engine motion on the mounts. But before I drill this and lock it in I will sleep on it. Sometimes things I forgot come back to me when I give them time to season a little.

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Starting to Install Fuel Servo and Control Cables – 4.5 hrs

December 23, 2012 Leave a comment

Sunday Dec 23, 2012

This morning early I unpacked the components of the Airflow Performance fuel injection. These were included with the engine I bought from Aero Sport Power but were not installed when it was shipped. I have no idea how this goes together. The AFP manual is included but frankly it is less than straightforward. What I really need is step by step instructions based on my aircraft configuration. I am building 7A with IO-360, AFP fuel injection and vertical induction. That is not a “standard’ configuration supported by Vans. The closest thing they support is an O-360 in a 7A so you can’t count on the plans to always be right. I haven’t been able to find any clear directions on the forums so I’ll just have to try to figure this out as I go. I’ll document it as best I can in case anybody else needs the help.

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There is an adapter plate that clearly looks like it mounts directly to the induction sump. And based on some of the information in the manual I gather that the two angle brackets mount to that adapter. But the angles have to go on first because the screw heads are not accessible after it is installed. I did some fit checks and I am beginning to see that the throttle control is on the right side of the servo and is further forward than the mixture control which is on the left. So the short bracket goes on the right and the long bracket goes on the left. At least one photo in the AFP manual seems to support this. But there are multiple holes on the angles and you can adjust the position forward and aft by selecting holes. What to do? More fit checks using the brackets and servo and a control cable seems to suggest that the angles should be set with the most forward hole in the angle mating with the most forward hole in the adapter as you can see below. I went ahead and torqued the screws for this but I could change it later if necessary.

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Then I mounted the adapter to the induction sump. For now the screws are dry but I will use some locktite on these when I do the final torquing. Locktite is recommended in the AFP manual.

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Here is the adapter from the right side.

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And here it is from the left side with the fuel servo installed. I found four free running nuts in the ASP package along with four all metal lock nuts. I am guessing that the free-running nuts are for initial fit checks like this. At least that is what I am using them for. You can see the mixture control arm is about 6 inches forward of the flag-shaped area of the angle bracket. That is where I will mount an angle to hold the mixture cable.

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The right side shows the throttle control and again the flag-shape area of the angle bracket is about 6 inches aft of the control arm. It’s starting to make sense now. I can see now why the Vans plans for an O-360 show a firewall penetration near the fuel line fitting for the throttle control. It is a pretty straight shot and the angle bracket can be used to secure the cable. Now I feel confident I can punch the hole for an eyeball feed-thru in that area. I sighted along the projected path of the cable and see that the feed-thru should be between the fuel fitting and the nose gear tube of the engine mount (see below). I marked the center of the hole location and drilled a 1/8 inch pilot hole. Then I enlarged it to 7/16 using a step drill.

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Fortunately a friend loaned me a hydraulic punch kit with a 1-1/8 punch and it requires a 7/16 center hole. For clearance reasons I had to put the head of the punch on the cabin side of the firewall. Here you can see it set up just before pumping the handle to punch the hole.

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Wow, the hole came out nice and clean. I barely had to deburr the interior edge. I used the eyeball parts as the template to mark the locations of the screw holes and I drilled those with a 1/8 inch carbide drill bit. Notice that I rotated the hole pattern about 45 degrees from horizontal so it would fit better.  To have better access I removed the fuel servo before punching this.

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Then I screwed the eyeball parts into the newly made penetration. It is ready to receive the throttle cable except the cable is .265 diameter but the hole in the eyeball is .250. I need a 17/64 drill bit to open this up just a little.

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