Dave’s RV-7A Building Log

With the head of the prop governor correctly positioned, I went ahead and secured the screws and safety wired them. This is the first safety wire I’ve done. The first one I did over, but the rest turned out pretty good.

I also wored a little bit on the fuel line doubler for the firewall. I’d like to put the doubler behind the firewall like the other doublers. However, I’d also like to tie it in with one of the stiffeners. I think I have a plan.

I removed the engine mount from the fuselage in preparation for drilling the fuel line and control cable firewall holes. I did a bunch of measuring and examining and thinking. I’m almost ready to drill the holes.

Sub-50 degrees is just too cold to work out in the shop. I could crank up the heater, but it seems a waste for the 10 or 15 minutes at a time that I’m actually out there. Instead, I brought the parts for the mixture linkage into the house. It’s kind of a complicated gizmo that changes the direction of the mixture actuation and reaches around the sump.

It all went together fine except for some washers. I’m not sure what exactly to use for the large washer that keeps the bearing end on the control arm in case the bearing gives out completely. The plans call for a washer that’s not included in the kit. The kit includes some tinnerman washers, but it doesn’t look like those will work very well. I’ll just order more of the washers called out in the plans. It’s a little frustrating that it takes only 10 minutes to put together the assembly and then I spend another 10 minutes trying to figure out something stupid like washers.

With the studs installed yesterday, it was time to install the governor and cable bracket. Some builders wait until the engine is mounted to deal with the prop governor. It seems much easier to me to work on the stuff on the rear of the engine before it’s installed, as long as it won’t interfere with the engine install itself.

I used a nut, star washer, and plain washer for each stud and torqued them to 140 in-lb per the MT prop install instructions. At first I was worried that I installed the bracket at the wrong angle. The “up” arrow on the drawing from Van’s is not really up.

Both the Vans and MT instructions mention that the prop governor head might need to be rotated. Mine certainly needed it. The control arm was on the bottom. I took these pictures mainly to document how the safety wire was originally.

I decided to go ahead and temporarily mount the control cable on the bracket and governor to find the ideal position of the control head. The cable operates very smoothly. I even found myself making vroom-vroom noises. And then I realized something weird about one of the stops. If you look closely in the picture at the stop on the left, you’ll see that the screw is backwards. The control arm hits the head of the screw rather than the end. I’m not sure if that is intentional or not. I’ll check with Vans.

Reply from Gus:

I think it probably should be the other way around, but it won’t matter.
You will not go to the low rpm stop very often, if ever, and with the cable travel available, there is a good chance that the cable will limit the travel before the arm hits the stop anyway.

The interesting part is that I am getting full travel from the prop governor with plenty to spare. I’m wondering if the stops on the governor are just completely wrong. The only way I know to check them is to run the engine and exercise the governor. I guess we’ll wait and see, because that is a long ways down the road still.

Other than that little issue, the rest of it works well. I was able to set it up to get full stop-to-stop movement of the control arm.

I picked up some acorn nuts to try on the governor pad studs. They didn’t work. The top is not strong enough. I emailed Mahlon and he replied at 8:30pm his time! He suggested locking two nuts together on the stud, which I tried before but didn’t apply enough torque. I really torqued the nuts against each other this time, and that worked. I measured the governor base plus washers plus nut plus two extra threads plus a tiny extra. That ended up being 1-3/8″, so that’s how much of the stud I left exposed. The top stud was a little more stubborn so it’s 1-1/2″.

I also tinkered with the electrical a little bit. I swapped out the plastic clips I was initially planning on using for some zip-tie mounts. I attached them with a #8 flat head screw, washer, and nut. These mounts are going to work much better. I can secure the wires more securely and it’s easier to to add and remove wires later on.

The word from Mahlon is that the prop governor studs should be installed so that the end of the stud that is hard to thread goes into the engine. I tried locking two nuts together on the stud and used that to get the stud installed. It wouldn’t go any further than about 1/4″. I’ll try a cap nut next. Also, I’m not sure if should use the black gasket that came with the governor, the green gaskets that came with the engine, or both.

I moved on to something else. I installed the oil pressure fitting and one of the oil cooler fittings. With the oil filter adapter in the way, I need to use 45 degree fittings for the inlet and outlet. Van’s supplies a 45 and straight fitting in the firewall forward kit. They also supply only one 90 degree fitting for the oil cooler, although the plans clearly call out two fittings. Strange.

I also received my order from SteinAir. It was delivered across the street by UPS. Those idiots have about a 95% success rate. Not good enough. The order was also missing an item I ordered and paid for. I wish I could say that hasn’t happened before. I think it’s time to find a new source for electrical stuff. The order included some more D-sub pins and connectors, some large lug terminals (that were supposed to be in the master kit), a couple smaller fuse blocks, and one red LED swivel cockpit light (there were supposed to be two). At least the light looks pretty cool.

I searched around a bit and found some advice for securing the axle nuts. I wasn’t sure how tight to make them, which affects where the hole is drilled for the cotter pin. One way to do it is to tighten the nut to about 20 in-lb while spinning the wheel. This sets the bearings. Then back off the nut and hand-tighten it. I don’t have a wrench big enough for the axle nut, so I fashioned one out of scrap wood with the band saw. It’s free and worked great.

I estimated the 20 in-lb of torque and did the procedure above a few times and came to the same spot each time. I decided that was the spot to drill. Following Dan’s advice I picked a hole in the axle nut that lined up with a thread valley and punched it lightly. Drilling between steel threads is not fun. The drill really wants to wander. I finally got through it and cleaned up the threads with a small file. I threaded on the nut, lined up the hole and marked the hole for the other side, which happened to line up right at the peak of a thread. Oh well. After drilling and cleaning up the threads, it all went together perfectly.

I repeated the whole process again with the left wheel. Time consuming.

I then moved on to the nose wheel. I was well tired of dealing with the wheels, but figured I might as well get them done. The nose wheel parts went together fairly easily. I’ve read some people having trouble getting the parts together. The only trouble I had was that the axle holes in the fork were under-sized. I had to enlarge them to get the axle bolt inserted. I still have a little bit more to do, but I need to get a fish scale in order to estimate the break-out force for turning the nose wheel.

I went through the same routine with the right wheel. Luckily, this time everything fit much better. The axle still needed some work, but not nearly as much as the left side. I went straight for 13/32″ spacers like I had for the other side and the gap ended up being on the short end. I guess I’ll just use some washers.

You can see in the picture that I used a chunk of plywood with a hole in it to hold the end of the gear leg at the far side of the bench. That worked out quite well.

I also messed around with the engine a bit. I had to hunt around for the instructions for the prop governor, but finally found them. The instructions mention studs for mounting the governor on the engine, but no studs were on the engine. I scanned some builders logs, and posted a question on the forum. Turns out the studs were in a bag that came with the engine. However, the two ends of the studs are different. One end threads in easily and one doesn’t. I suspect the difficult end should go in the engine, but I’m going to confirm with Mahlon before I go any further. It’s also not super-intuitive how to orient the governor on the engine. I’m fairly certain I know how it should go. There really needs to be more instructions on this stuff.

One last thing I almost forgot is that I painted the battery box spacers.

Now that the left wheel was mounted, I checked the clearance between the wheel pant bracket and the disk brake using some scraps of sheet aluminum as a feeler gauge. The gap was right at the high end of the range. I trimmed each of the spacers down 1/32″ and the gap turned out perfect.

I messed with the axle nut a bit, but wasn’t entirely sure how tight it should be.

I started out making the spacers for the wheel pant brackets. The plans call out 13/32″, but I made them 14/32″ to start with. I’ve read that 13/32″ might be a bit short. I attached a bracket to the left brake flange and then tried to get the wheel onto the axle. It would go on about 1/4″ and then get stuck. I tried sanding the axle with some emory cloth, but it still wouldn’t go on. Measuring the wheel bearing, it was exactly 1.250″. The axle was 1.248″ inboard tapering to 1.250-1.251″ at the outboard end. I had thoughts of heating up the bearing to see if that would help, but I didn’t want to get the darn thing stuck on there. I secured the gear leg really well and went after it with the emory cloth at the outboard end, using a similar action to polishing a shoe. I took the wheel bearing out of the wheel to make it easier to test fit and to make sure none of the hairs from the grease seal were getting in the way.

After an hour of this, I finally got the bearing onto the axle. What a hassle. Now I need to do the other axle.