chevy43

4 oz burned so far..... 7x3 APC prop. Aprox 23 oz of thrust and 40 mph pich speed. Can you say VERTICAL!!!

Yours truly,
"Vintage Cox Crank Buster"

soarrich

My Feedback: (98)

Whos diesel head?

gabe200

My Feedback: (21)

LOOKS LIKE RJL HEAD

chevy43

6-7 min. per oz of fuel. This thing has got some power baby! It can be peaked at 14,500 rpm on the 7x3....

I just ran it for another 13 min....

SGC

Chevy,
6.5 mins/oz = 4.5ml/min ,my 1cc Barbini does 2ml/min swinging a 7x5 about 12300rpm , I must dig out my new medalion 049 and give it a werl on diesel.
Stewart

layback2

My Feedback: (12)

OH yes sure has the power for sure

chevy43

I'm getting 14,700 to 14,800 now.... I'm pushing it I know!

gabe200

My Feedback: (21)

what kind of fuel are you using did you mix youre own

chevy43

Davis plane fuel.

SGC

Chevy,
Even TD's will snap the crankpin if pushed too hard, Ied recomend fuel with 35-40% Ether to enable lower comp settings.
Stewart
grr caps locks

chevy43

Thats what I hear. Somtimes I have to find out for myself.... Great runner for now though!

Ran a couple of more tanks through it.. 14,800 rpm. Tic, tic, tic..........

chevy43

If anyone tries this here are my recomendations: Don''t do it! But if you do:

Do not prime the engine! Start with the needle at about 3 turns out.

Lube the thrust washer with some oil or fuel.

Find where the contra piston touches the main piston by hand. Take note of that positon and stay away from it! Running positon is about 3/4 turn away from the contra piston touching. Starting position is about 1/8 turn tighter.

Don't bother with this conversion unless you have great compression! This engine did!
Use an electric starter.

Slowly open the needle about 1 to 1 1/2 turns more and adjust the compression till you get something.

Make sure you are a diesel expert before trying to run a cox on diesel!

AndyW

My Feedback: (1)

Good advice Chevy,

Respectfully, I'd like to add that you can find the needle setting or get very close to it by first running it with 25% glow fuel. From there, when you convert to diesel, don't fill the tank with fuel and leave the needle at the glow setting. Keep in mind that when you convert to diesel, all your lines need to be diesel proof. I use neoprene

With NO fuel in the tank, find your start setting on the compression by adjusting till you get consistent prime burst.

Now fill the tank, draw fuel up the line and go for it. Apply two or three drops of prime, to the intake. NEVER in the exhaust port. It should now start and keep running. From here, WAIT, don't touch anything, let the head stabilize in temperature for a minute or so.

Now tweak the compression screw. Likely you had to overcompress on your prime setting finding procedure to get a start. Back off the compression till the engine peaks. Now play with the needle. First instinct is to lean it out and that's normal if this was running on glow fuel. But diesel has a unique tendency to sound rich even if it's lean. This is kind of one of the advantages of diesel engines. They can run lean for some time with complete unawareness that it's bad for them. But don't abuse this perk. First, back it off the needle, that won't hurt for sure. If the revs don't pick up, take it in lean some and see what you get. Don't make the first try at adjusting the needle by going leaner. Rich first. Diesels will tolerate lean for a time but even they get fed up eventually with too much oxygen and not enough calorie juice.

Next, I suggest that you don't be afraid to use an electric starter. IF you follow the points here and those by Chevy. Again, with respect, to clarify, what Chevy is saying is that you won't get hand starts unless your compression SEAL is very good. These last few years, that was impossible to get.

First, as this is a 1/2A engine, use a 1/2A starter. That takes a lot of the danger out. But more importantly, flooding the engine with excess fuel is the "bad ting dat go rong" when using an electric starter. Here's how that happens.

Even the experts sometimes fall into this trap. Following quite sensible procedures, they hand start. Even glow engines ought to hand start easily with just two or three flips. But diesels have a third adjustment that's pretty critical, the compression. Instinctively, you follow glow practise and you fill the tank with stinky fuel. You draw fuel up the line, apply a drop or two of prime into the intake and flip. And flip, and flip and flip. So, the compression wasn't right. If you had read the instructions, you would have backed out the screw to the recommended setting. That should have you somewhat undercompressed. So now, after you flipped a few (10) times, you turn in the screw and repeat the flips. If it fires, Murphy gets discouraged and backs away. Careful though, he's not far behind and ready to move up in a split second the minute you stumble. If it fires and keeps running, see the previous paragraphs.

As the engine runs flat out, at max RPM, go back to all the adjustments to make sure that under prolonged running, no settings have altered or have come to require being altered. Tweaking, is the expression, I think.

But if you have to repeat the tweak compression/flip procedure three or four times, and still no go, keep this in mind. ETHER is very volatile and by now, most of that in the first few primes are gone and evaporated and only residuals of the last few is left. But kerosene and oil haven't gone anywhere. They've settled to the bottom of the crankcase along with just a smidgen of ether. Now, why is it there? All that flippin' and primin' has ejected out the exhaust port only a minimal amount of fuel and a healthy proportion of the multiple prime applications has stayed behind. This is because flipping by hand just doesn't have the power to send the majority of the prime charge up the ports and out the exhaust.

So in frustration, even our experienced dieseler succumbs to the inevitable response from the peanut gallery and pulls out the electric starter. Naturally he has to prime it again. Naturally the higher spin provided by the starter now blows that puddle of ether depleted fuel, that's collected in the case, right up into the combustion chamber with healthy enthusiasm. Far more than with hand flipping. And next thing you know, BANG there goes a bent rod. IF you're lucky. Broken crank pins have also been known to show their displeasure by morphing into not that which they were.

But the experienced modeller will have backed off the compression screw two or three turns, making note of the running setting. If he's really, really good, he'll also pinch off or disconnect the fuel line to the carb. This is a last precaution that speaks to the first few paragraphs. Remember, we want to find the compression setting with NO fuel going to the throttle. That comes later, AFTER the engine burns off several prime runs reliably.

I sure love diesels and I hope that the new CS06D is a huge success.

Andrew

Thank you -- I don't run diesels, but if I do, this is a little piece of information I intend to remember. Maybe it will save an engine.

chevy43

Here it is on a 7x4 MAS.

chevy43

Here is a 7x5 MAS Scimitar:

chevy43

Note the compression settings as the pitch goes up....


I'd love to try a higher pitch 6" prop. Too bad I cant get a 6x5 or a 6x6 for some speed!

The beauty of diesels is you can pick the prop you want and tune the engine to it instead of being stuck with few choices.

ptulmer

My Feedback: (5)

Chevy, with minor reshaping you can have the props you want! Here's a link to the 6.5x6, but there are others in that range. http://www3.towerhobbies.com/cgi-bin...?&I=LX1691&P=0

rainedave

My Feedback: (1)

Did the head come with that little arm you're using to "mark" settings?

David

Andrew

David --

That's a locking lever -- set the compression and tighten the lever against the head to hold the compression setting.

rainedave

My Feedback: (1)

Ah! See, I know almost nothing about diesels. But... I have been wanting to try one out. Are conversion heads a bad decision for a first attempt? Is there a such thing as a good "beginner's" diesel?

BTW, your tests are impressive chevy43.

David

chevy43

I think a cox is not a good begginer engine exept that it is cheap. A PAW is much easier to use but lots more expensive. I have broken stuff on my learning curve and so will any begginer - just part of diesel learning...

I'm very careful with thease cox conversions and they may break any minuet.....

gkamysz

My Feedback: (19)

Graupner makes a 6x5 in the Super Nylon. They used to have a 6x6. I had one years ago.

lildiesel

I'd recommend a real diesel for your first experience. A conversion will cause too much grief while learning the diesel ways. Something like PAW .09 or larger at least. Maybe you could get a used .15/.19 to learn on before going to the more finicky 1/2As.

ptulmer

My Feedback: (5)

Dave, go to the Southeastern Model Show this coming March and meet Eric Clutton hisself. He'll show you how to start them, care for them, etc and is a real gentleman and a bit of a comedian. But bring a full wallet...