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Another Diesel to Get Running...

PeterGregory

CrossThread Industries
#1
I am sharing my tale of non-success - but I believe I will be successful, eventually.
You can see a picture of a classic OK Cub Diesel .049 I bought on eBay.

Excellent OK Cub Diesel from eBay.png

It either was never run, or it never could run - ha.
Very pristine, it is about as old as I am - the 50's.

I took it out and set up the test stand at noon today, thinking I would have run it and cleaned up in about 1 hour.
That plan was not to be.

For longer than I like to admit, I flipped that diesel with great expectation that the next flip would be the one where it would kick off and scream.

I learned a lot, and I think I have what should be the correct compression and needle valve "NV" setting.
There were burps & purrs for a second throughout my trying but I could not get it to catch.

What I learned on this tiny, responsive engine was to keep my left hand on the compression screw. The engine did not want to run "dry." I found I was flipping forever with no kick when it didn't sound juicy. After you prime either right into the exhaust port or into the front intake, it would sound very juicy. You have to back off the compression because that extra fuel causes detonation before you reach top-dead-center (TDC) with the piston. You can feel the prop kick back before you push the prop to the "downside" of the stroke. It is a lot like fishing with worms of bottom bait, when you feel the tug-tug-tug of a fish. The bump-bump-bump of the juicy detonation tells you to increasingly ease the compression as you keep flipping, and at a certain good point the engine will actually fire correctly for a while, then it is time for more juice.

I just couldn't get the engine to draw its own fuel into the nipple on the intake port. I had great expectations with each flip, but wore my arm out (again.) I do love the pursuit of the "sweet spot" for the engine, though.

I will tell more about what the problem was once I hear back from some inquiries I put out on the internet.
Most of all, i will pick an outerzone.co.uk plan to put this into and do a build log, here.

There are a bunch of things about these I diesels I do like, the nostalgia being one of the biggest factors.

Sweet Heap - British from Aeromodeller

sweet heap.jpg
 

pgerts

Old age member
Mentor
#2
It can take a long time to get the feeling for how to adjust diesel engines.
Lots of 60-70 year old people lerned the hard way as young teenagers.
Many never got the engines to run.

BUT - when you really get the settings right the engines are really good.
If you can fint a Good Year team racer.
Landing, refueling starting and off in e few (2-3) seconds!! - for those with the best adjusted engines.

Your OK Cub will probably fit in the smallest Weaterman racing class.
 

PeterGregory

CrossThread Industries
#3
Great share - what a great way to spend a day.
Looks like problem in the pits for that one team at the 3 minute video mark.
I'd love to try this - nothing like this within 2 hours of me, though.
Motivated to find out what my little Cub .049 doesn't like.

Is the 18 Scale racing an FAI class?

PS Subscribed to your channel - looking forward to going thru your vids.
 
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Epitaph

Ebil Filleh Pega-Bat ^.^
Mentor
#4
Wow, control line!! I have several friends up in northern Spain that still practice this modality all the time!! One plane that is very much a favourite out here is an old spanish design by Modelhob called the "Yeyito", because it has good response and runs really well, and can be easily adapted to fly with "flaps" together with the elevator in opposite direction (when elevator is down, flaps go up, and visa versa) to make for some tight turns, something very much needed in acrobatic control line flight.

Yeyito.jpg

I was going to make one myself, but it's something I never got around to, and finding a place to fly it around here isn't easy...
 

Epitaph

Ebil Filleh Pega-Bat ^.^
Mentor
#5
Another thing, if you come across a larger diesel motor that uses an exhaust, and you can't find an exhaust for it, one trick they use a lot here is using the metal cylinder from a used asthma inhaler... it's cheap, it's cheerful, it's shiny, and it can withstand the heat and pressure no problem!!
 

pgerts

Old age member
Mentor
#6
The GoodYear is not an FAI Class (A B C or D) but it is common to fly a lot more than the 4 FAI-classes during a line competition.
The Good Year is one of 4 classes in the AMA Rat Race rules. The Weatherman is quite new and is supported by the SAM (oldtimer flyer).
By the way - there is a Yeyito somewhere nearby. But the fuse and tail is modified - a little more belly and painted as a Mustang :)
 

PeterGregory

CrossThread Industries
#8
Yeyito plans to download

Thanks Gents - all good info... Maybe the asthma inhaler will get my 049 over its sputtering and wheezing...
I have to give the engine another try tomorrow.
As opposed to the long time I spent without success with the .049, I pulled out an MP-Jet 80 yesterday and it fired up in 5 minutes!
So on average it took 2.5h apiece to get them running (well the 049 never really ran).

I found plans for Yeyito on outerzone - have to take a closer look at it for my next plane: http://www.hippocketaeronautics.com/hpa_plans/details.php?image_id=2853

I am in the middle of building an "Old Faithful" which was originally designed, built and flown in Sweden armed forces.
http://outerzone.co.uk/plan_files_06/6270/Old_Faithful.pdf

More to come...
 
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pgerts

Old age member
Mentor
#9
Nothing in the diesel thread for a long time.
I got some really old things last summer - http://modellflygnytt.se/opublicerat/ot-diesel/index.htm
There was nothing i really wanted but i traded two old Super Tigres for a "new" Irvine 20 diesel.
It took me to this summer to fit the Irvine in my Falcon 56. I tried the engine at the lawn with some new 22-33-45+2 mix and the engine run directly at 3000 rmp at low and 10500 rpm at full throttle. I let the enginge run at low rpm when going for a cup of tea - 90 minutes on a 150 cc tank. Later same week i had the plane in the air 60 minutes on 500 cc of fuel.
https://www.facebook.com/gert.gertsson.98/videos/670089089805221/



Someone found the Falcon 56 picture and asked med for the plans - He knew another Irvine 20 Diesel NIB !

I am now the owner of two identical new engines and need a suggestion for a twin engine - fast/easy build - light wieght - good flying model fitting the two Irvines.
 
#10
I am sharing my tale of non-success - but I believe I will be successful, eventually.
You can see a picture of a classic OK Cub Diesel .049 I bought on eBay.

View attachment 52278

It either was never run, or it never could run - ha.
Very pristine, it is about as old as I am - the 50's.

I took it out and set up the test stand at noon today, thinking I would have run it and cleaned up in about 1 hour.
That plan was not to be.

For longer than I like to admit, I flipped that diesel with great expectation that the next flip would be the one where it would kick off and scream.

I learned a lot, and I think I have what should be the correct compression and needle valve "NV" setting.
There were burps & purrs for a second throughout my trying but I could not get it to catch.

What I learned on this tiny, responsive engine was to keep my left hand on the compression screw. The engine did not want to run "dry." I found I was flipping forever with no kick when it didn't sound juicy. After you prime either right into the exhaust port or into the front intake, it would sound very juicy. You have to back off the compression because that extra fuel causes detonation before you reach top-dead-center (TDC) with the piston. You can feel the prop kick back before you push the prop to the "downside" of the stroke. It is a lot like fishing with worms of bottom bait, when you feel the tug-tug-tug of a fish. The bump-bump-bump of the juicy detonation tells you to increasingly ease the compression as you keep flipping, and at a certain good point the engine will actually fire correctly for a while, then it is time for more juice.

I just couldn't get the engine to draw its own fuel into the nipple on the intake port. I had great expectations with each flip, but wore my arm out (again.) I do love the pursuit of the "sweet spot" for the engine, though.

I will tell more about what the problem was once I hear back from some inquiries I put out on the internet.
Most of all, i will pick an outerzone.co.uk plan to put this into and do a build log, here.

There are a bunch of things about these I diesels I do like, the nostalgia being one of the biggest factors.

Sweet Heap - British from Aeromodeller

View attachment 52279
I am experiencing exactly the same issue, but with an ok cub .074 diesel. It has excellent compression (no leak) and will detonate with a reasonable amount of fuel at the exhaust port or front intake at maximum compression minus 1/2 turn. if overprimed, it will detonate at maximum compression minus one full turn. It will keep working for a couple of seconds but will not draw fuel, at any needle position, compression screw position; even if I close the venturi partially with my finger. I verified whether the spray bar was not clogged, changed the fuel line for one of smaller diameter, tried an external tank positioned at the same level or above the engine (it was to no avail, leading to its flooding), tried various propellers (6x5, 8x4, 8x6), left the engine soaked in fuel overnight to clean it and repeated all the described steps. After failing miserably, I changed the 0.74 cylinder and head for a nitro cylinder and glow plug, and the engine simply will not draw fuel.
Sometimes, I even notice bubbles at the fuel line, near the venturi. I think the engine could be starting in the clockwise direction due to overcompression, however the engine will not start at lower compressions, depending on the fuel amount.
The fuel I am using consists of 27% kerosene, 30% castor oil, 3% motul cetane booster, 40% ether (I use those with my MK-17s and cox engine without a problem)
As I am out of ideas, i will next try 60% eter/40% castor oil as fuel.
Comforting to know that someone has the same sufferings, though.
 
#13
It can take a long time to get the feeling for how to adjust diesel engines.
Lots of 60-70 year old people lerned the hard way as young teenagers.
Many never got the engines to run.

BUT - when you really get the settings right the engines are really good.
If you can fint a Good Year team racer.
Landing, refueling starting and off in e few (2-3) seconds!! - for those with the best adjusted engines.

Your OK Cub will probably fit in the smallest Weaterman racing class.
you guys must have strong stomachs cause i tried this when i was young and puked.
 

Piotrsko

Master member
#14
Wasn't thinking of muffler pressure, but.....that'll work, too

Was thinking of using a soft tank and slightly squeezing just to get fuel flow.

How about low wing falcon (aka Skylark) done as a twin? Most of the same parts, someone did it here a while back.
 
#15
Wasn't thinking of muffler pressure, but.....that'll work, too

Was thinking of using a soft tank and slightly squeezing just to get fuel flow.

How about low wing falcon (aka Skylark) done as a twin? Most of the same parts, someone did it here a while back.
That will be easier to do. Maybe a baloon tank or a baby bottle liner. Will try that, provided they resist diesel fuel.