500 lb. koolaid man

A couple of questions about the diesel conversions...

1. I've read that sure starts don't make good diesels, but it still interests me as something to try. All that is really needed is a different head, rite?(I'd make one if possible) What makes it different from a glow plug(to the eye)?

2. Can you use diesel from the pump, also, do you have to mix oil?

Thanks.

lildiesel

Model aircraft engine "diesel" is a mix of castor oil , lamp oil, and ether. Very different from pump diesel. See "Everything Diesel" for more on fuel mixes. Any Cox will run as a diesel for a short time. Then the con rod breaks or the crankshaft web relieves its stresses. I've made both the RJL head and the DDD head work on .049s, mostly by running a bit rich and undercrompressed. Going for glow like RPMs is a no-no... put a 7x4 or 8x3 on it. And make it a wooden prop for the sake of your knuckles!

chevy43

MAS 7x3


It is not a diesel begginers engine however!! Meccoa has the heads.. You can get it to last for a while ( not sure how long yet but I've got about 2-3 hours on one) if you are carefull and a tuning expert. This one broke because I was using a throttle sleve and it loaded up a little.

supagloo

Is this what you call a not-so-sure start?

Mr Cox

Or a sure-non-start...

500 lb. koolaid man

OK thanks guys... I read up a little about the fuel. I understand that better now.

What makes a diesel head special though? What's the "inside" end look like? Thanks.

supagloo

http://davisdieseldevelopment.com/gallery/closelook.htm

Look under "How complicated is it?"

500 lb. koolaid man

Thanks

BMatthews

The weakness of the Cox parts will still be an issue. If you want to try out a diesel engine I'd strongly suggest you just buy a PAW from Carlson Imports so you're starting with the real McCoy and don't have to worry about all the longevity and strength issues.

combatpigg

My Feedback: (3)

To simulate the 1/2A glow to diesel "experience" without actually investing in a diesel head and diesel fuel, do the following:

1.) With the head off your Cox engine, bring the piston to BDC and lay a 3/8" deep well socket on top of the piston. Now take a 5 pound maul and strike the socket like you would if you were trying to break up a sidewalk.

2.} Take some charcoal lighter fluid and douse yourself, your clothes and all vulnerable areas on the plane. If necessary use a heat gun to work the oily fluid into all major covering seams and underlying wood.

There you have it in a nutshell, the 1/2A diesel experience [don't forget to swear a lot]

Mr Cox

You'll also need some one to hit you on your fingers at the same time as doing the above

chevy43

Aw come on now CP! Thats all I fly!

I do kind of stink though..............

combatpigg

My Feedback: (3)

Chevy, get a move on and give us a great report about the 1cc PAW. That would be nice to hear instead of these depressing reports about the latest glow engines.

supagloo

I'm not Chevy but I got a PAW 1cc on my Jr. Falcon. If well primed it starts within 5 hits. Runs very reliable in every position.
In 2 words: Great engine.....

combatpigg

My Feedback: (3)

supaglue, what is the power output?

RocketRob

My Feedback: (1)

Hey CP, You made me crack up out loud at work....they already think I'm half nuts without uncontrolable laughter coming from my office. Yeah you only needed the lacerated index finger and some spilt fuel in the car..........but the fuel in the lacerations aid in cotterization

Ask Chevy about his "Magic PAW .55" it has more power than his 1cc paw and ALL of my engines of any size....[]

digital_trucker

Back in the day I had a PAW 19 that never saw a starter, always started on the 3rd flip (yes, EXACTLY the 3rd flip). PAW makes nice engines.

combatpigg

My Feedback: (3)

RR,glad to be of service . I haven't had a "diesel anything" in my car for more than a year and my wife still thinks it stinks. Most women hate model aviation, but they REALLY really hate diesel.

Dan Vincent

Diesels that are designed to be diesels, such as the PAW line, will run reliably but can still be overstressed by a ham-fister tightening down too much on the compression lever.

A sweet-running diesel has a "Happy" sound and when you start overcompressing it will begin to sound uncomfortable. Ignore the sounds and you will have problems.

Diesel fuel has more power drop for drop than glo fuel so you need a strong engine. Stresses are much higher than in a glo engine.

Davis did make a heavy-duty crankshaft for reed-valve Cox .049 engines that will make your lower end fairly bullet-proof.

Jim Thomerson

I have a Rustler Cheetah 2.5cc fake old time British diesel. (It is an Oliver Lynx redesigned to be a front intake. ) I'd guess 9 times out of 10 I get a first flip start. The engine runs very smooth and reliable but is not very powerful. I'm still fiddling with props. An APC 9x8 is the best so far.

chevy43

My best PAW .061 does 15,300 on a 7x3 with no mufler and it is kind of loud... .061 PAW's aren't my favorite diesels though..

My Magic .033 does 12,500 on a 7x3 MAS. PAW's can vary though. The ones that have a lower top end will sometimes do better on really big props.

digital_trucker

Yep, there's always a little variance...that's just the nature of reality. Every once in a while everything comes together 'just right'.

supagloo

For this particular plane a MAS 7x3 or Kavan 7x3 (yellow) are the most effective.
I tried several props (APC 6x3, 6x4, 7x3, 7x4 , MAS 6x3, 6x4, 7x3, Kavan yellow 6x4, 7x3).
Some of the propellers will give more rpm and eventual more speed, but the plane accelerates much slower. Since I have the RC engine it is convenient if the plane reacts to changes in throttle settings too .

I can try to dig up the tacho readings if you are interrested.

gcb

500,

There are two heads that I know of, DDD and RJL. I do not have an RJL, but the DDD has a teflon seal and a contra-piston held on by the adapter head. The reason for the teflon seal is that, in theory, when you over compress, the heat rises rapidly and causes the teflon to melt and save the engine. Some people do not like that feature and prefer the RJL.

As someone mentioned, if you want to run a reedie as a diesel you should get the DDD (Davis) crankshaft. As a matter of fact, Davis sells a combo for reedies that includes the crankshaft, the head, and extra teflon shims...at least they used to. Give him a call.

You should break-in an engine prior to conversion. I would also recommend getting commercial model diesel fuel over mixing your own...at least at first. You can order a quart of Davis fuel when you get the head.

Still, these are not as good as a purpose-built diesel, IMHO. PAW is currently made, so apare parts are available.

Good luck. You might check out the diesel forum on this site.

George

500 lb. koolaid man

Thanks for the info.