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Post  Scratch049 on Fri Oct 25, 2019 10:57 am

Which of the Cox .049 models enjoy the best success for diesel modification.
Considering type of cylinder, porting, etc.
Any information is appreciated and will go directly toward feeding my present mania. Very Happy
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Post  Surfer_kris on Fri Oct 25, 2019 3:04 pm

In general the most timid glow engines will make for great diesel engines.
With diesel fuel you will run a larger prop at lower rpms, compared to glow, so there is no need for large transfer ports and large crank openings etc. The lower rpms also means that there is a lower fuel draw from the venturi effect, so small intakes work better.

So I would recommend to start with a regular old-school Babe Bee, or even a Texaco one. Wink
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Post  fredvon4 on Sat Oct 26, 2019 8:27 am

I wonder if one of Matt's (ExModelengines) drive plate that mates to car engine is a good way to have a stout crankshaft for diesel .  on other hand if the typical break is the con rod pin on the crankshaft.... a large diameter shaft just makes a heavier engine.
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Post  Scratch049 on Sat Oct 26, 2019 9:01 am

Kris wrote: start with a regular old-school Babe Bee, or even a Texaco one.
Great! Very Happy
Got one of each.
Also a "Sure Start".
Guess a Tee Dee is out. Unless it can be de-tuned?
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Post  Surfer_kris on Sat Oct 26, 2019 10:59 am

Scratch049 wrote:
Guess a Tee Dee is out.

It is not out of the question but it is much harder on the engine to run at the rpms that a TD is designed for. Diesels running higher rpm will need a higher compression ration and they are also picky on the fuel blend. So you risk damaging the engine with either a run-off, in terms of temperature, or you might simply shear the pin off from the crank-web. If you are playing around with homemade fuel, it is also highly recommended to change the crank in the Babe Bee to a heavy duty one (i.e. a car crank).

Remember that a larger prop requires a lower compression ratio. If you prop a diesel engine to max-out at around 10krpm, then the compression ration on good fuel will only have to be slightly higher than what it is on glow fuel (for a much smaller prop).

You can easily detune a TD a little by reducing the intake diameter, but I don't think that it will ever run as smooth as the lower timing engines will.
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Post  Mike1484 on Sat Oct 26, 2019 12:43 pm

Car crank only works in a car case . It is a larger diameter and needs a tapered adapter for the prop . Our Cox engine suppliers have a nice diesel heavy duty crank that works just fine . I would suggest the Mecoa diesel head over the Teflon disc heads . A Texaco or Bee will work just fine with these two parts and some good fuel .

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Post  aspeed on Sat Oct 26, 2019 12:51 pm

Does a car crank have the same diameter as a regular one, or does the case need to be bored? I have broken TD and BBee canks already on glow. The earlier TD cranks had a thinner web and were weaker. Not sure exactly when this was changed, or if the crankcase was somewhat shorter. We can get Kleenflow Ace fluid, but it seems less than 50% ether so I have never used it. I have the teflon disc head and PAW .06 that I have no tried out yet mostly because of the ether. Is there a way to improve upon the teflon style? I can machine stuff if needed.
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Post  Surfer_kris on Sat Oct 26, 2019 1:04 pm

I haven't checked the car cranks, just assumed that was what the heavy duty crank where in the early days. I can't imagine that they made a special crank but couldn't be bother with making a proper head and used the teflon stuff instead...

The stock cranks are fine if you know what you are doing (proper fuel and avoid the teflon disc heads etc) but the stronger cranks are an extra safety.
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Post  Mike1484 on Sat Oct 26, 2019 1:59 pm

EX Model engines has car cranks and also an airplane case/crank and tapered drive plate as well as diesel cranks . I think the Killer Bee and Venom had heavy duty ( diesel ) cranks . Cox International also has the diesel cranks . Also the PAW engines are great diesels and are very user friendly , I have 7 or8 of them . Check what EX says about the car crank and case .

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Post  Surfer_kris on Sat Oct 26, 2019 2:31 pm

Yes, an engine from PAW would be very good as a "first" diesel engine. Very docile, smooth runners with a soft exhaust note. The smaller ones (< .09) do not have mufflers but there are exhaust diverters offered for them and works well to keep the oil of the plane and also softens the sound even further.
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Post  aspeed on Sat Oct 26, 2019 2:58 pm

The PAW would be my second diesel. When I was a kid, I had a Frog .15. I could never start it. It ran very well once when my flying buddy started it, but that was the only time. I guess the teflon diesel head will just sit then. I was going to order the diesel/venom crank with some other stuff from Cox international. Really I don't run the Cox stuff much any more because of the wind here and the muffler rule at the RC club. Had to sneak in a few flights for the RWYB contest. I'll get the PAW going at some point. I often thought of making a diesel head for something like a .15 size. Some of Hopeso's videos were done with ether just used to start a motor, and it ran on a kero/oil mix. I am sure a throttle would not work with that mix. I have no experience with knowing what settings would be correct even if the fuel mix was right.
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Post  smooth_bill on Sat Oct 26, 2019 5:47 pm

Aspeed,

Very wise to jettison that Teflon head, and seek advice from any experienced diesel user to get a new one running.

My first diesel was a McCoy .049, and was my first successful engine. Had an early Cub .049, but never got it running well. Anyway, I had no trouble buying the Ether at a drug store, and mixing my own fuel. Got it running with no problems, and successfully wore out a Walker Firebaby with that great little engine.

I attribute my luck to several years of swapping my US model magazines, for English Aeromodeller and Model Aircraft magazines, and reading them from cover to cover! The English mags had wonderful coverage of diesels, and the best engine reviews I've ever read!

Don't let anyone tell you that diesel engines are as easy as glow engines to start, and run. They are sensitive to compression and needle settings, fuel blend, temperature, and require a very healthy flick to start (at first). Once the proper compression and needle settings are found, starting becomes a joy with most of them. Learning to recognize over compression, and flooding signs, are important, and that is where experience will help.

I have found a few diesels that were difficult to start, but that was often due to problems with the engines. PAW is easy to set up and run, once the diesel basics are learned.

Unfortunately, I seem to have lost some of my ability to recognize diesel problems by their exhaust notes in my later years. Still haven't found a diesel setting on my hearing aides!

Good luck, and keep us up to date with your progress.

Bill
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Post  Oldenginerod on Sun Oct 27, 2019 12:30 am

aspeed wrote:Does a car crank have the same diameter as a regular one, or does the case need to be bored?

No and no.
Cranks from the car engines have a larger diameter. I believe there may have been some which used a regular crankcase assembly from a plane engine, but generally they were larger with a tapered nose rather than a knurled one.

Boring out a case will remove the hard anodized surface and it will wear quickly. It would need to be sleeved in bronze to last any time.

Rod
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Post  smooth_bill on Sun Oct 27, 2019 12:53 am

Rod,

Good information, thanks!

All the Cox engines I've purchased individually and in small batches, I've yet to find a car engine!

I wouldn't be surprised if the prop stud was a little larger as well, as it probably carries more load. I've watched videos that showed either push starting, or hand starting and then dropping them the last few inches to the track.

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Post  Oldenginerod on Sun Oct 27, 2019 6:25 am

The car engines don't use a prop driver (for obvious reasons) and have a tapered nose on the crankshaft with no splines/knurling. The flywheel mounts directly onto the end of the shaft. Many of the crankcases have a snap ring groove around the front which held on the pull-starter. I've always found the stud to be the same size as the standard prop studs/screws.

As mentioned, Ex Model Engines supply a prop driver made especially to suit the tapered crankshaft so that a prop can be fitted.
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Post  Ken Cook on Sun Oct 27, 2019 8:24 am

I experimented using my conversion of a Babe bee for control line use. I installed a RJL head and was using Davis Diesel Power fuel. I subscribed to the larger prop theory and used a Master Airscrew thin bladed G/F series 7x4. First flight was stellar, it barely had enough power to sustain level flight. Second flight I leaned the engine up and turned in the compression a bit more, about 50 seconds into the flight the crankpin breaks off of the crank. The engine was hauling the plane around better but not enough for maneuvering.

I installed a Davis Diesel crank and tried once again essentially running the engine as fast as possible. I quickly came to the conclusion that this isn't going to work and that the glow was better. Second attempt, I switched to a Black Widow, the rpm's were certainly higher than the Babe Bee, unfortunately, the Davis cranks are solid from web to driver and these tend to cause a bit more drag. I know the engine had more in it. I dropped prop size to a Cox gray 6x4, rpm's were certainly improving however, the plane still didn't have authority taking the plane over the top of the circle. It sounded like it was over compressed and sagging. No matter how much I backed off the compression, it didn't make a difference. It was next to impossible to achieve back to back runs without constant fiddling of the needle or Tommy bar. If the engine ran out of fuel, I would quickly get to it to refill as to not lose heat from the engine and restart. Nope, wouldn't work. The engine both the Babe and the Black Widow required the compression to increase for starting up and then backed off.

I then tried the Davis Diesel head, this offered more rpm's with the cost of reliability in starting. Engine speed came up and allowed for some loops, aside from that it was pretty bad. I went with the Cox 5x3, now were talking, the engine came alive and was sounding good. Fuel consumption seemed to have doubled from the previous prop cutting the flight time quickly. The problem was now the Teflon was blowing out at a very fast rate. The Teflon sits entirely across the combustion chamber, it seals on the plug landing and the inner portion of the Teflon would burn. It would then tear and fail. I never tried it but others had said cutting a aluminum disc from soda can material works superior to the Teflon.
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Post  aspeed on Sun Oct 27, 2019 9:00 am

Sounds like it is not worth the effort on the reedies. I might even have a car crank already with the worm gear setup if that is the same one. I was thinking the Medallian would be a good candidate, but the crank would likely go. I could make a bronze bushing and thrust washer for a Bee, but I guess not. Probably would run it, and leave it in the drawer like a lot of the others.
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Post  Scratch049 on Sun Oct 27, 2019 12:28 pm

Wow, really appreciate all the input.
To be up front,I don't have a whole lot of current experience with these engines.
It was some years ago that I ran a Baby Bee in a Cupcake motor glider.
Great airplane that liked to thermal and would land at your feet.
Eventually I graduated to larger engines and aircraft.
However the most fun that I had with any of my creations was with that little half A.
Seems that most of what is being looked for in the Cox .049 engine, could be obtained with the Texaco model. Or, a Bee modified to Texaco standards.
At least for my use, scale and Victorian era RC models.
Went to peruse the PAW site yesterday.
They put out a nice catalog with a varied product line.
Their prices are fair and from my reading, a quality product.
I imagine their support is good as well.
Perhaps a dedicated diesel is a better way to go?
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Post  fredvon4 on Sun Oct 27, 2019 2:00 pm

I follow many forums
While some dedicated hobby folks can, and have made a glow conversion work....Cox .049s seem prone to frustration

Almost everybody who acquires a small purpose designed Diesel has good luck and less frustration or broken engines

Set a thread on what you really want to accomplish -------------and many CEFers like Chris and Ian and Rod  
(I am sure some others) with experience will send you in search of stinky nirvana

Commercial diesel fuel ( no matter the price) is a first acquisition....later find REAL JD start fluid...it is 48 state mail orderable

As far as I know there are no USA federal or state laws prohibiting purchase or storage of Ether...Just hard to find a small qty supplier...if you want 100 liters for commercial use it is for sale from dozens of outlets
I know a guy who knew a guy who used to steal it in pints off a doctors office exam room table...same butt head stole the Liquid Nitrogen spray bottle. I have not seen Ether in an exam room for a decade but yesterday the Liquid Nitrogen burned off a pre cancer on my face

As a child I got way too sick on deep sea diesel fishing boats with my dad...to this day even a diesel pickup down my county road nauseates me...I do NOT do small diesel engines
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Post  Scratch049 on Mon Oct 28, 2019 8:23 am

Interesting that you brought this up Fred.
Is the smell of model airplane diesel the same as what we'd use in a Cummins ?
Worked for a while on a dive boat in New Jersey.
Wasn't too much troubled by the diesel fumes.
Be interesting if anyone did a comparison test between two Cox engines.
One on glow and one on diesel.  Huh...
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Post  smooth_bill on Mon Oct 28, 2019 3:57 pm

May be an acquired taste, but I always liked the smell of Kerosene (what you smell in diesel fuel and the exhaust fumes).

Lived on a farm as a child, and our new kitchen stove also burned Kerosene. Guess I associated the smell with frying bacon, potatoes, and eggs that we had for breakfast most mornings.

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Post  Oldenginerod on Mon Oct 28, 2019 4:11 pm

There seems to be so much discussion about the smell of model diesel. (No, it's not like truck fumes.). I'm not sure why so many seem to find it so offensive. As bill said, most of us will have some experience with kerosene. Just add some aromatic ether and you have it. Yes, it's strong, but I think people must still be thinking back to the old days when you could still find Amyl Nitrate in the fuel as an ignition enhancer. That apparently was the main culprit, but it hasn't been used for years due, once again, to it being used as a drug.
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Post  Surfer_kris on Mon Oct 28, 2019 4:18 pm

The fuel it-self is not the problem, is the exhaust residues that has a specific smell which is very hard to get rid off.

After a good day at the field, I need to put all my clothes staright in the washing machine or my wife will not stop nagging about it... Rolling Eyes
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Post  Scratch049 on Mon Oct 28, 2019 4:25 pm

Aha moment!
Bill, you completed the dots for me.
We used to use kerosene for heating when I was a kid.
Maybe that's why I never found the small offensive.
Jeez...I'm getting old.
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