Thursday 29 February 2024

Oil Ball Valve

A quick update.

As mentioned in my previous 'STOP PRESS' post I'd discovered the ball valve had the 'kick' in the wrong direction (it was kicked out at the top). It was Annual time recently so with the cowling off I took the opportunity to remove the ball valve mount and make it right. 

After a recent flight test in which I pulled many vertical lines I'm pleased to say the oil pressure stays high on an upline now, so it works perfectly.

I haven't seen so much as a puff of smoke out the exhaust either and oil usage is virtually zero after aeros so this all seems to be working very well.

I'm now looking forward to a new season of aerobatic competitions.

Sunday 24 December 2023

Twister meeting at Paderborn Haxterberg

A selection of pages from Ingo's excellent write up of our Twister meeting in July of this year.

As always, click on the images for a larger view.

Thursday 21 December 2023


More information has come to light since my last post. 

I've been busy visualising all the possible flight conditions to better understand what's going on. 

As you can see the 'kick' for the ball valve should be at the bottom not the top as I currently have it. It's not a 'biggie' to change this as I can re-use the mount, just flip it up the other way and drill and pot three new holes is all. The hoses and fittings will remain the same. Something to do in the New Year. While I'm at it I think I may change the oil air separator mount so that it kicks slightly out at the bottom too as this seems to be a more optimal solution. 

Click on the image for a much larger view.

Tuesday 5 December 2023

Oil Air separator and more

Way back in early 2015 when I was installing the engine and its accessories I was told by Pete to just copy what he did. 

Since then I've realised it was rather naive of me not to question the placement of certain items a bit more and do my own research.

There has always been some oil loss when doing aeros but since competing at Intermediate grade I've noticed a massive increase in oil loss. Sometimes to the point of returning with the mark on the bottom of the dipstick...

Obviously this is unacceptable. Not only thrashing the engine with low oil but the subsequent mess down the belly of the fuselage and the cost of having to top up the oil all the time.

Time to do some research and figure out what is wrong!

I read up on the Christian Inverted oil installation guide. Also UL Power now give advice for placement of the oil air separator - see below, BTW this information was not available when I was installing my engine.

It turns out the placement of the Oil Air Separator was completely wrong.

It should be on the other side of the engine (opposite side to the sump return connection) and as high as possible so that the path for the oil return line from the bottom is a steady descent (when flying upright and level) with no 'buckets' for the oil to collect.

So the plan was to relocate the oil air separator to the Starboard side of the engine and place it as high as possible.

Of course "when you change one thing you change everything" and so it was that now the ball valve was in the way! So that would have to be relocated inboard.

This also was a blessing in disguise as I'd been meaning to remake my ball valve mount for some time. I found out that even though UL Power say to mount this perfectly vertically on the firewall - if done so then in a vertical climb (something I do a lot in Intermediate aeros) the ball will not know which way to go as it is not subject to gravity when in this state. The solution is a small 'kick' out at either the top or bottom of the mount so that the ball positively stays put or moves to inverted position when on a vertical upline. I prefered that it stay down so put the kick at the top.

Potentially I was looking at 2 new mounts, and up to 8 new hoses and 16 fittings.

As it turns out I was able to reuse most of the hoses and some of the fittings but both mounts had to be fabricated.

Everything was a fight with this job as the access behind the engine to the firewall is extremely limited and a lot of what was installed was done prior to the engine going on back in the day, so certain fasteners took a lot of time and swearing to get to and undo and then redo later on. This meant I was out of the air for nearly 2 months.

I finally got everything finished two weeks ago and gave it a ground run with the cowlings off to check everything was ok. All was well with the work I'd done but a fuel fitting that I didn't even touch decided to fail and was leaking fuel badly. I had hoped to fly it that day but that was out of the question now. Another weeks delay while I waited for a new fitting. 

Last week I was finally able to get the cowlings back on and take it up for a test flight. All seems well and I even did a few aeros pulling a few vertical lines. No oil smoke so far. I'll have to give it another longer test to be sure but so far it looks like this fix has worked.

Now it's time to clean all that old oil off the belly!

UL Power current information recommending placement of the Oil Air Separator - wish I'd had this information when I was doing my engine install.

How my oil air separator was installed


Red line shows where the drain line was and how much of a 'bucket' was in it.

How things were before I started the fix.

Idea was to put move the Oil Air Separator to this location but as you can see the ball valve will be in the way so it had to move too!

Early thoughts with new placement and angle of the ball valve. keeping this forward facing option was out of the question as the hoses and fittings would conflict with the engine mount so I ended up flipping it 90 degrees sideways which is a Christian option BTW.

New Ball valve. Made from 12 plys of Carbon with a foam core and solid carbon sides. Very strong yet only 100 grams in weight.

'Kick' out from the Vertical is clear here. This makes sure the ball valve stays down when pulling a vertical line.

Finalising the position of the Oil Air separator - better check the top cowling clears it first!

Almost there. Ball valve has had to move inboard and flip on its side.

All done. Time for a ground run.

Red line shows new path of drain line from Oil Air Separator. Downhill and no buckets!

Same as above pic but without the red line.

Wednesday 19 July 2023

A new Twister

Kit number 33 is complete and isn't she a beauty! So good it won the Best Twister award at our recent meeting.

Constructed by Eugen Schaal over 2.5 years (1,500 hrs).

Powered by the UL Power UL260iSA engine with an Airmaster electric variable pitch prop giving a 1,500 fpm rate of climb.

Eugen was lucky to build his at the Silence factory so had all the answers and help at hand - which explains the fairly quick build time for such a fine example.

I wish Eugen many happy flights.

Parked in pride of place at our recent Twister meeting.

In the factory when almost finished.

A neat idea to secure the gear leg fairing without fasteners at the front.

Ready for some more flight testing.

It look like some cowling modifications were needed to make the UL fit.

Sealed plenums rule!

Garmin screen, Trig Radio and Transponder.

Looking happy to have received the Best Twister award. 

Friday 14 July 2023

Krishna Build Video

Check out this excellent video by Krishna of his Twister build. 

In particular the trials and tribulations with installing a Rotax 912, the first Twister to feature this powerplant.

Krishna Article - Airsport Magazine

Tuesday 7 March 2023

Wheel bearings, tailwheel axle bolt and panel upgrade

It was Annual time again in February so I finally got around to doing several jobs I'd been putting off.

I noticed when I last changed the main wheel tyres that the wheel bearings were not running smoothly. This is after 500 hrs with most of that from grass runways which get very muddy here in the UK during the winter. 

So I changed these bearings for new. I did not recognise the Italian brand of bearings that were in there from new so changed these ones for SKF which is a brand I trust. Hopefully they will last longer this time. I will make a note to check the wheel bearings every 200 hrs from now on.

The bearing part number is: 6004-2RSH SKF Sealed Ball Bearing 20mm x 42mm 12mm (BB-1853). You will need 4 in total, 2 per wheel.

Getting the old wheel bearings out was a real pain as the hub is a single piece of Ali which is not able to be split in half. There is also a spacer inside of the bearings which prevents a bearing puller being used to pull them outwards. The bearings sit on a shoulder on the inside so there was no way to push them out either.

I ended up having to dismantle one of the bearings from one side to then remove the balls and centre race, this then allowed me to remove the spacer and push out the other bearing (using a deep reach socket, a vice and the boiling water to expand the Ali hub technique). Finally I had to rework the remaining outer race of the dismantled bearing as it has a smooth concave shape which a chisel or screwdriver tip just slides off. A little Dremel work made this into a squared off shape so I was able to drive out the outer race too.

Onto the tailwheel.

This I found several months ago, the bearing had actually seized on one side.

So again these were changed for new. 

That part number is: 6300-2RSH SKF Sealed Ball Bearing 10mm x 35mm x 11mm (BB-1919). You'll need 2 of these for the tailwheel.

I also discovered that the bolt which is used as the axle for the tailwheel was slightly too short in its shank. This meant that the thread was working against the hole in the tailwheel fork rather than against the smooth shank as it should be. See the pic below.

I sourced a correct sized bolt (M10 with 120mm length) and cut it down to the required total length. This still leaves enough thread for a washer and thin Nyloc.

I'm happy to have found these faults and fixed them.

While I was working on the main wheels I decided to change the brake pads for new too. They didn't really need changing as they had only worn about 30% but as I was in there disassembling everything then it was prudent to do so.

The engine has really settled down with its tappet clearances. Cylinders, 1, 2 and 4 didn't need adjusting at all this time. Cylinder 3 needed a small tweak - but this Cylinder head is only 100 hours old as it was replaced at 400 hours due to the leaking exhaust valve.

I replaced the engine mount rubbers at the front too. You have to take the whole engine forward to get to the rear rubbers so I've left those for the time being as I don't have an engine hoist anymore.

Finally, I decided it would be a good idea to have a backup to the Dynon EFIS - in case it ever went down for any reason (even though it has a back up battery, if you were IFR and it went down you would be screwed). So at AERO Friedrichshafen last year I bought a Kanardia Horis EFIS. I got it for a special show price which made it about £300 cheaper than buying here in the UK.

To make room for it in the panel I got rid of the mag compass and moved the old 'steam' altimeter into its place.

This left the altimeter hole free for the Horis.

It's a pretty straight forward install, just connect up Pitot and Static and then power and ground. The only other two things that need sorting are the outside air temp probe, which I've located on the underside near the main gear leg and the GPS antenna which I've located in the space above the safety cell at the front.

The EFIS is fully featured and even has a dedicated G-meter screen which will come in very handy for Aeros as the one on the Dynon is not easy to read in flight as it just displays as small numbers.

Main wheel bearing hub, which is one piece and makes removing the bearings a real pain!

Destroyed wheel bearing to get it out of the hub

Old and new brake pads - not too much wear after 500 hrs

Old Tailwheel axle bolt to the left, note worn shank from seized bearing and damaged thread. New bolt cut down to same length but with correct shank length on the right.

Still room for a thin Nyloc and washer

Engine mount rubber - showing some wear and elongation of the hole

New panel with Kanardia EFIS

Features a dedicated G-Meter screen

How the panel used to look with mag compass at right