Justin's Raven

[justin.schoeman]

Had my AP over on Saturday (a many-time aero VW builder), to look over my shoulder while I assembled things yesterday... So far, the bottom end is complete up to, and including the flywheel, end shims, and <censored> gland nut.

I have finished shuffling barrel shims, until I have all the deck heights within 0.1mm of mean. Cleaned and prepped all pistons and cylinders. Gapped all rings.

Just need to tweak the cooling baffles on the heads and clean them up, and I can finish the assembly. With a tiny bit of luck, the engine will be fitted later this week, for test and break-in runs over the weekend!

[Tortoise man]

Hope everything go s well
Greetings

[justin.schoeman]

Oh boy. Seems I did it again...

I got sloppy on Saturday afternoon, and did not notice that I had knocked a copper head gasket skew, before putting the cylinder head on. So now I have ruined one of the gaskets... And just naturally, there are none available in the country (at least none that I can find).

I did spend some time yesterday experimenting with annealing the old head gaskets to possibly reuse them. It seems this may work as a last resort.

If anybody knows of any 92mm 0.060" copper head gaskets available anywhere in the country, please let me know!

[justin.schoeman]

Another busy night. Started off with my flatting block, some sand paper and the old head gaskets. Managed to surface one down to +/-0.02mm thickness all round (which is flatter than the newly manufactured gasket!). Annealed the old gasket. Jury rigged a simple Brinel tester, and confirmed that the annealed used gasket has pretty much the same hardness as the new one.

I am happy that the old gasket will be a perfectly suitable replacement - so I won't wait three weeks for a new one from the US . I will however run the CHTs up to red line temps, and do a leak down before first flight (just to be sure).

I also finished modifying the oil cooler mount to accommodate the adjustable oil pressure regulator I installed this time around. And I modified the cooling baffles. Previously, installing the baffles was a race between fatigue, and blood loss, to see which would stop you first... I have replaced most of the fasteners with rivnuts, so that it can all be assembled from easy angles now.

I have almost finished a new throttle cable bracket (the old one held the cable at just the wrong angle, so it could get sticky at the throw limits).

As long as nothing else goes wrong, I should be installing and test running on Saturday. I hope.

[JvTonder]

Ons hou duim vas vir jou!

[Jean Crous]

Nice one Justin Ek se mos ons vriend Justin is n "vetterige" engineer
Regards.
Jean.

[justin.schoeman]

Nice one Justin Ek se mos ons vriend Justin is n "vetterige" engineer
Regards.
Jean.

Almost there. Second head is on, oil system is primed (made 50PSI turning it by hand!), and playing with the valve geometry. With the price of fuel, I dropped the compression ratio a bit, to make sure she will be happy on mogas too. Need to slightly re-shim the rocker assemblies to get the valve geometry set - seems to be working out (and I am really glad I don't need to remake the pushrods!).

[justin.schoeman]

:D Hi engineer Meneer, how about an update hhhhhhhhmmmmmm?????????????????????????
Jean.

I am about to go on leave, so every available moment has gone into getting her running (want her properly lubed up before storage!).

So this evening at around 19h00 I finally wheeled her out of the hangar. Cranked first to bring oil pressure up (~6 blades had her at 50PSI), then turned on the mags, and she fired off straight away. Died a few seconds later because the idle is set too low... Cracked the throttle a bit more, and fired her up again. Runs sweet.

Still some issues to sort out. I previously had problems with the throttle sticking a bit. So I redid most of the throttle system, and it is smooth as silk - but after all that work, I discovered that it was actually due to a poorly machined part in the carb itself! Sonex is sending me a new one, but now the throttle is so smooth that it is almost impossible to use. Let go, and the vacuum of the engine will pull it closed. Hold the know, twitch a muscle in your big toe, and the RPM changes. After working so hard to take the friction out, I will now have to add a friction nut to 'fix' it!

I will also need to have a new prop spacer made up, as there is some fretting around the washers I used to adjust the existing spacer.

Should be able to sort all of this out early in the new year, and hopefully fly soon after!

[justin.schoeman]

The offending carb bit:

20121218_223808.jpg (24.72 KiB) Viewed 2617 times

The little knob is fractionally off centre, so it pushes the needle against the side of the metering hole, when the offset is to the side, causing it to stick. At the moment I am running a 1/4 turn too rich, so that the needle is pushed down (instead of sideways), and still moves freely.

[justin.schoeman]

A very brief clip of the first start - just to show that there really is a plane out there somewhere!

http://www.youtube.com/watch?v=zoefETjWK20

[Scotsman]

Really admire your persistence Justin. I hope that you get to fly your baby as a Christmas present soon!

[Jean Crous]

Justin, a question............you say a 1/4 turn to rich on the needle. What effect will you say that is going to have on your full power static RPM ????
Jean.

[justin.schoeman]

Justin, a question............you say a 1/4 turn to rich on the needle. What effect will you say that is going to have on your full power static RPM ????
Jean.

I am not sure. Without throttle friction, I could not really lean it out and test...

Need to sort this out before any real engine runs.

[justin.schoeman]

Back from holiday, and spent the last two days at the airfield. Have now finished 4 of the six required break-in runs, and everything is looking great.

The only slight problem so far, is the oil pressure is a bit high (75PSI), and I am getting a fine oil mist out of the front of the prop bearing. I have adjusted the regulator to the minimum, with no change, so I will have to remove the regulator, and replace the spring with a shorter one. I will have to see if I can get a new crush washer tomorrow, and try do this on Tuesday...

[justin.schoeman]

I managed to find a new crush washer, as well as a used spring that was 5mm shorter than the EMPI one. Replaced the spring, and the start-up pressure dropped from 90PSI to 45PSI. I took it out and started warming it up for a test/break-in run - and then it started raining... Since the RDAC is exposed without the cowls, I made a mad dash back to the hangar to get her undercover. Over the next few hours, I pulled her out once or twice, but every time I got out of the hangar, it started raining again! Will do the next runs, and fine tune the oil pressure on Saturday. Weather permitting...