Matt's RV-7 Project

The B&C 60-amp alternator comes with all the hardware you need to mount it to the engine. I first bolted the (very substantial) mounting bracket to the matching boss on the engine:

The two mounting bolts get secured with safety wire, and you also bend up the tabs on the little washer-plate thingy to further immobilize them. Talk about belt and suspenders.

The included spacers put the alternator in just the right position to get the pulleys lined up. Here it's just hanging from the pivot bolt, as the tension arm isn't in place yet.

The alternator came with a Gates 7365 belt:

Oh boy, another little surprise… not only will I have to take the propeller off to replace the belt at some point in the future – probably a most inopportune time – but I also had to pull the ring gear to get the belt past the starter's pinion gear.

Here it is with the tension arm loosely connected. I think I'm going to go find a shorter belt so I can tuck the alternator in closer to the engine and farther away from the cowl.

I also had to replace the belt in our vacuum cleaner yesterday, so this has pretty much been an all-belt weekend.

I bolted on the exhaust pipes for good:

I put high-temp anti-seize paste on the studs, and torqued the nuts to 120 in-lbs. I also used the included blow-proof gaskets between the pipe flanges and the cylinder heads.

I painted some more anti-seize on the exhaust slip joints before sliding them together. I also dribbled some mouse milk into the exhaust's ball joints.

Look at this little guy. If there was ever a mouse that was more eager to help build an airplane, I don't think I want to know about it.

I taped some plastic caps over the pipe ends to keep critters out.

I used stainless steel clamps to attach a couple of heat shields to the pipes where they come close to the throttle cable. This plus the firesleeve should protect the cable from radiant heat.

Since I had a spare, I also put a heat shield at the top of cylinder #4's exhaust pipe, near where the mixture cables goes by. There's more clearance here than where the throttle cable is, but I figure a little extra heat protection can't hurt.

This is how I safety-wired the hose clamps:

The clevises I am using inside the throttle quadrant are AN481's – actually a special variant threaded for a 10-32 cable end, available from Aircraft Spruce under part number 05-01437. I'm using these because they have sufficient throat depth to avoid getting hung up on the quadrant levers, which is a problem with the AN665's recommended by Van's. But, the AN481's are quite a bit wider, which is a problem when using the closely-spaced DJM throttle quadrant. I fixed this by grinding down the clevis that will be used for the center lever (the prop control) and bending the ears slightly inward to narrow it. With this modification, the AN481 will take the 11/32" clevis pin used by the AN665, instead of the 15/32" pin it comes with. That means it will fit in the same space as the factory-recommended clevis, and won't hang up on its neighbors as it moves. There's still plenty of material left, so I'm not worried about the strength of the modified part.

As I did with the throttle and mixture levers, I decided to drill a new hole in the prop lever in order to get a little more travel. I had to measure this carefully to keep the clevises in the throttle quadrant from ending up too close together and getting tangled up.

I re-safety-wired the throttle cable bracket in its new orientation on the bottom of the engine sump. As is often the case when I try to use safety wire, it took about eight tries before I managed to get it right. Sometimes it sucks to be a perfectionist cursed with limited motor skills.

The little machine screws that come with the firewall eyeballs I'm using are so easy to strip out that you can almost ruin one just by pointing a screwdriver in its general direction. I went to the hardware store and picked up some different screws (on the left in this photo) that have a more substantial head and can actually be tightened by humans.

In addition to the split lockwashers under the screw heads, I used a dab of blue Loctite on the theads of each screw as I installed the firewall eyeballs for good.

Behind the panel, I lashed the prop cable to the mixture cable with adel clamps to keep it from getting tangled up in the rudder pedals:

I cut lengths of firesleeve for the engine control cables and treated the ends with RTV. Technically, the prop control cable doesn't need firesleeve since it's not that close to the exhaust, but it would bother my OCD not to do them all the same way.

I slipped the firesleeve over the control cables and tightened the bulkhead nuts for good:

Then I finished off the ends with heatshrink tubing (a purely cosmetic touch) and firesleeve band clamps. The plans call for a simple loop of safety wire here, but I like the look of a good firesleeve clamp.

Normally you firesleeve a hose on your workbench, where you have plenty of room to use the band clamp tool. It was challenging to get all the clamps tightened, what with the engine and its various associated parts in the way, but I managed.

I tightened all the hardware in the throttle linkage for the final time and installed the required cotter pins:

Ditto for the mixture linkage. Lots of cotter pins here. Cut my hand on at least one of them, which is pretty typical when installing cotter pins. Interestingly, the throttle side of the fuel servo uses a castellated nut and cotter pin to hold the control arm on, but the mixture shaft on the opposite side is not drilled. I used the nyloc nut that came with it (lower left corner of this image) although as a matter of principle I don't like using nylon locknuts forward of the firewall. I may eventually change it out for an all-metal locknut.

Ditto again for the prop linkage. I ended up getting about 60 degrees of travel here, which according to the manufacturer of the prop governor is plenty.

In this photo you can see a few different details of how I installed the clevises inside the throttle quadrant. First, I painted the clevis that I'd previously ground down, since I sanded off all the corrosion protection. The pins for the throttle and mixture levers are installed with their heads pointing inward, to give more clearance for the prop clevis. The outer two clevises have a 1/16" brass washer inside the fork, and a 1/32" steel washer under the cotter pin, to make sure they can't accidentally migrate inwards and foul the center lever. And finally, let me tell you that these cotter pins were a pain to install. Seriously.

The engine controls are finished! All the way from the throttle quadrant…

…to the cables:

…to the engine. Awesome.

I also managed to go flying and shoot six approaches under the hood this weekend, which was fun. Now I'm legal to fly instruments for another six months.

Since I don't post enough overview photos, here's a picture of the fuselage as it looks today. Yep, there it is.

I started today's session by getting out my Vetterman exhaust pipes and temporarily bolting them up to the engine. The welding on these pipes is really, really nice, and the fit is excellent.

What was less excellent was the way the exhaust pipes interfered with the throttle cable. After I spent all that time getting the linkage to work right, I found that the factory-supplied bracket, installed per the plans, causes the throttle cable to run right into the crossover pipe from cylinders 3 and 4. Grrrr. There needs to be at least three quarters of an inch of clearance between the cable and the hot exhaust pipe, but in this photo you can see that they are totally smooshed up against one another. No good.

After much bad language and head scratching, I figured out how to get the cable to clear the exhaust pipes by reversing the mounting bracket, thus moving the cable attach point about two inches outboard from its previous position:

Here's an end-on view, showing that the cable is now routed well clear of the exhaust pipes, through a relatively open area:

To make it all fit, I had to re-bend the bracket to make the angles work out. The geometry involved here makes it necessary for the cable to run downhill to the bracket, and then the cable's actuator rod thingy has to slope sharply upwards towards the fuel injector servo. Luckily the cable end is designed to accommodate a certain range of motion.

The linkage angles inward towards the throttle arm, where it now attaches on the outboard side with a shorter bolt. Good thing I used an offset arm here.

Here's a view looking up from the floor. With the throttle quadrant hooked up inside the fuselage, there's just barely enough travel to hit the wide-open and idle stops. I think there's actually less margin than before, if that's possible, but it does work. The cable actually has pretty good clearance from the exhaust pipes, too – about an inch, which is way more than was physically possible with the other bracket arrangement.

What a mess. The combination of horizontal induction and throttle quadrant is an exercise in frustration. And speaking of messes, this is what happens when you fiddle with control cables for multiple weeks without putting your tools and parts away – it took me half the afternoon to clean this up:

We also went to the huge parade they held downtown to celebrate the big sports victory.

My views on sporting events are well known, but it was still fun.

I've been struggling for more than a week to figure out exactly how to correctly hook up the engine control cables. Rather than fill up the whole internet with a play-by-play of the various things I tried, I'll just show you the end results.

Here are the cables mounted to the cable bracket, with clevises installed. You can sort of see that I had to drill new holes in the throttle and mixture levers in order to get sufficient travel at the other end. To do this I had to take apart the throttle quadrant, which was straightforward but annoying.

The cables fan out from the bracket in various directions. I may use adel clamps to tie the throttle and prop cables together (approximately where the piece of masking tape is) just to keep them from chafing.

The prop and mixture cable arc rather gracefully (if you ask me) over the top of the rudder pedal brace, and go through the firewall on either side of the parking brake plumbing. The previous careful measuring and use of custom-length cables paid off here, as these two cables manage to go where they need to go without getting hung up on anything. I will eventually replace the experimental duct tape with a pair of adel clamps, mostly to keep the prop cable well clear of the brake hoses.

The throttle cable is basically a straight shot from the quadrant down to the lower center of the firewall. I ended up using my 48" cable here after all, as the 49.5" one I'd ordered from Van's was a bit too long. I may end up returning that one, or I may just keep it around for whatever.

The prop cable makes a hard right turn after passing through the firewall eyeball, and crosses over the mixture cable to reach the prop governor cable bracket. Meanwhile, the mixture cable continues forward to its own cable bracket on the top of the oil sump. The throttle cable is visible down below.

I had to use a joggled mixture control arm in order to get it to clear my Skytec NL inline starter. I think you could use a straight arm if you had a Skytec LS or PM model, but the NL is quite a bit longer than either of those two.

Here's how the mixture bellcrank works. The mixture cable connects to the arm on the right side of the photo, and the bellcrank provides the necessary offset to reach the mixture arm and also reverses the direction of movement. You'll note that I had to drill a second hole much closer to the mixture control arm's pivot point… this is necessary because the limited amount of travel available at the quadrant end requires a shorter mixture control arm in order to get full travel at the servo.

Here's photographic proof that the mixture can reach the full rich stop:

…as well as the idle cutoff stop:

Despite the apparent complexity of the mixture bellcrank, I didn't really have much difficulty getting the mixture control working properly. The throttle was actually the hardest one, because of the very limited clearances that exist with the forward-facing fuel injection servo (if you have one, you'll see what I mean). I ended up having Mattituck send me another joggled control arm that I could use for the throttle, and shortened it as I did with the mixture arm. Here it's shown at the idle stop. Not visible is how close the rod end bearing comes to the bottom of the oil sump when the throttle is all the way back like this… it's close, but there is still just barely enough room.

With the throttle all the way to the wide open stop, the cable shaft almost touches the bottom of the oil sump as well. Moving the attachment point of the rod end bearing farther away from the pivot point is the obvious remedy, of course, but then the throttle quadrant wouldn't give me enough travel to go all the way from idle to full throttle. This would not be a problem if I was using standard plunger-style engine controls, but with the throttle quadrant it's an additional huge headache that I wasn't really expecting. I spent a week wrestling with this before arriving at this solution, and it just barely works (but it does work!). From what I've seen, I think that this wouldn't be so much of an issue with a vertical induction setup, but the combination of a throttle quadrant and forward induction is extremely tricky to get right.

Here's the prop governor cable at the fine pitch (full RPM) stop. It's actually spring-loaded to return to this position – I guess so that a broken cable will tend to return to the full RPM setting, which would be preferable to the opposite behavior in an emergency.

Once again, the throttle quadrant limits the amount of travel I can get out of the prop cable – I can only get the lever to move about halfway from the fine pitch stop to the coarse pitch stop. The plans actually mention that this might happen, but they don't provide a recommended minimum amount of travel. Just to be safe, I fired off an email to the manufacturer of my prop governor, to determine a) if this is an acceptable amount of travel, and if not; b) if a shorter control arm is available.

I set things up so that at the most forward position (full throttle, high RPM, rich mixture), all three of the engine control levers are almost, but not quite, at the end of their travel. There is a gap of about 1/16" at the top of each lever's travel, which provides a certain amount of "springback" to let you know that you've hit the actual stop on the engine instead of just hitting the limit of the lever's travel within the throttle quadrant. This is a good practice that I picked up from one or more RV elders. Obviously, in a situation like mine where the throttle quadrant is the thing that gives you the most problems in getting full travel out of your controls, you have to be very careful about balancing the goal of getting the correct amount of positive springback against the desire to get as much travel out of your quadrant as you can. Tricky.

At the full-aft position, the throttle and mixture levers are not quite at their limit of travel, so I know from the springback effect that the throttle and mixture are hitting the correct stops on the engine. The prop lever does hit the quadrant housing and limits the amount of prop control movement, as discussed above.

Here's a shot from the floor of the airplane, looking up into the bottom of the throttle quadrant. It's not quite as bad as the perspective in this photo makes it look, but there is still not a lot of clearance between adjacent clevises within the quadrant. I'm going to have to get creative to keep the engine control levers from jamming against one another.

Note: All the preceding photos were taken during development, before any hardware was installed for good – hence the absence of cotter pins. When I decide that the engine controls are really, really done, only then will I go to the trouble of installing all the correct fasteners.

Update: For those who've emailed asking about cable lengths, the final sizes I picked were 48", 51", and 52.5". Obviously these lengths are only applicable to my particular airplane, but if you are using a DJM quadrant with an IO-360-M1B and Bendix/Silverhawk injection these will be a good place to start.