I don’t like Rotax’s documentation. It’s extremely detailed to the point of nearly being unreadable. I also haven’t found anything that remotely resembles an index, so it’s impossible for me to navigate the plethora of pages to find the minutia of importance. Case in point. I recall reading that after 1st start, you must remove the valve covers and verify that the lifters don’t move with 15 # of pressure when the valves are both closed at TDC for each cylinder. This blog entry is to document that I have performed that procedure, but I can’t find the document to cite it properly. I’ll amend this posting when I find that document.
Saturday, May 23, 2015
The photo shows a motorcycle carb sync gauge looped into the cockpit. I spent several hours with multiple sized hoses and clamps jury-rigging the plumbing to get from the compensator tube and Left carb. When I finally got it out and started the next day, I had clamped down so tight at two places that the gauges were totally isolated from the vacuum. Frustrating but funny, in a geeky sort of way.
I got the engine started again, and did a partial sync of the carbs. I know that it’s within my capabilities, but I’m not at all confident of how to synchronize them from both idle and moderate / high power. I can hear the transmission knocking at low power and that’s not good, so I’m going to defer final synchronizing to Shane when I move out to KDLZ.
Carb Vacuum Gauges in place
I naively thought this would be a slam dunk. Not! I spent nearly 4 days fighting with the little tiny gap fillers that aren’t even visible in the photo. The downside of my initial sanding to fit was that I really failed to appreciate the fact that the roots of the prop blades are truly elliptical and I did my initial fitting to the minor axis of the ellipse. When I figured out how to pitch the props, they axis is quite different and they rotated up and impinged on the gap fillers. I had to find assistants to remove & re-install the blades several times to get things sanded down to fit.
Prop Pitch Measurement Tool
I also made an assumption that turned out to be false: that the leading edge pitch of the descending blade was the negative of the pitch of the ascending blade. The question of the assumption was triggered by a thread on VAF. I had previously set the prop pitches as 22.6° and -22.6° using the canopy side rail as the 0° reference. Last night I finally realized that this assumes the prop axis of rotation is parallel to the canopy rail. There’s no way to easily check that, but I’m pretty sure that they are not parallel because when I checked both blades in the ascending position, I found there was about 4° variation. I gave up on using the digital method for now and set both blades using the #3 pin. I’ll revisit this after I get the carbs synched.
Prop & Spinner installed. Finally.
Wednesday, May 20, 2015
The holes for the nut plates were final drilled #19, then the wing holes got drilled (from the inside). Lots of countersinking and deburring, then lots of riveting. You can see through the translucent fiberglass the two metal plates used to hold the gap fillers in place. That metal is only 0.032” but The Book called for countersinking. I declined and dimpled instead. I know, I’m a rebel.
The plate off to the side is the optional spacer I used to help alleviate the cowling spacing issue described else where (and nearly remediated, I might add!) I wasn’t able to do the final prop & spinner install because I need AN5-16 bolts (instead of AN5-15’s) due to that spinner. That, and it’s 1:00 AM when I took that picture and I didn’t have an assistant to hold the prop blades in place. BTW, the bolts arrived this morning about 10 hours after I took this picture. Stay tuned.
This page is all about getting the spinner well aligned. Take out the plugs so you can rotate the engine, tape up the prop blades to prevent scratches and clamp the spinner to the back plate. Then turn the prop and verify that the pitot tube doesn’t wobble (thus indicating that the spinner is well positioned. The Book recommends taping a ruler to a chair to position it right in front of the pitot tube so you have a good visual reference. I couldn’t get the ruler taped juuuust right, so I used my micrometer so I could adjust the tip.
For the photo, I put a light source on the (clear) pitot tubing behind the gearbox and it very nicely illuminates the inside of the metal pitot tube. Nice!
Saturday, May 16, 2015
Lots of fiberglass cutting today. The spinner had a 1” lip that needed to be trimmed off as well as the cutouts for the prop blades. I used the cutting wheel for the posterior lip, since that will be fine sanded to the backing plate in the near future. I hand-cut the side cutouts using a fine tooth hack saw blade. The upper rounded portion was easier, since it didn’t have to be preserved. (Note the fiberglass piece in front of the spinner—that will become the side panel behind the prop blade. It needed to be cut with minimal loss of material, so I used the finest blade I could find.) The upper part came out with some holes drilled near the perimeter, then quickly ground to shape with the Dremel tool with a sanding drum.
There’s a small bushing (brown) that goes in the tip. That needed to be roughed up and placed in the hole, after the hole was ever-so-slightly enlarged. It’s glued in with blue Loctite.
The rest of this page is the installation of the propeller, but I already did that last month as part of the engine startup, so I can officially take credit for this page today.
Friday, May 15, 2015
I’ve been away from posting on this blog for nearly 3 weeks. As you’ll recall from 4/4, I found a problem with the fit of the cowlings against the spinner plate. There was no easy fix, but so far, it appears that there’s a cheap fix. I reached the point where I’m reassured that I’ll be able to finish the revision without having to buy new cowlings, and will post a separate update when all is complete. Having reached that point, I felt ready to resume forward progress.
This photo shows the pitot tube. Recall that the RV-12 is designed with removable wings, and Van’s didn’t feel that it was feasible to make a detachable pitot line that runs back to the ADARHS in the tail cone. They designed the pitot tube that goes through the engine gearbox, prop hub and out the tip of the spinner. On the left of the transmission you can see the white plastic box that the pitot tube is attached to. To its left is the clear plastic tube that goes back to the ADARHS. Out of the right of the prop hub is the looooong metal pitot tube itself. I want to get the spinner attached this weekend to protect that thing from getting bumped by some clumsy oaf (that’d be me).
Sunday, May 3, 2015
There hasn’t been much published here for a while. I’ve got a couple of other irons in the fire (daughter graduating and getting married, another daughter 1 semester away from both graduation and her marriage) and some aviation things (CFI-I check ride tomorrow) as well. I’ve also discovered that I really don’t like having to re-work things. Like the cowlings that I’ve been slowly sanding and fitting and sanding and fitting and sanding and fitting. (That’s almost done, but will be the subject of another posting. Eventually.)
On the other hand, I did get something else of note accomplished: I flew the Cardinal down to Tennessee and took the 2 day course that will allow me to get my LSA Repairman Certificate (Inspection Rating) for 012 when the time comes. It was a great course with a lot of confirmatory information and a lot of new stuff, too.