Lobo Pup Twin Diesel

[Swifty]

I finished building my Lobo Pup Twin a couple of weeks ago, but have spent the time since trying to get it to run. Seems to have plenty of compression, had a couple of kicks out of it and a puff of smoke, but that's it. Cant buy fuel for these engines readily now, tried making my own using castor oil, kerosene and aerosol starter, but no luck. I was lucky that a member living close by gave me some fuel that he was using to run his single diesel with, but still no luck. So for the time being, I have shelved it and will return to it at a later date. Have put up a couple of photo's for those who have not come across this engine before.




Paul.

 

[bigrigbri]

It looks to me that the crankcase has far too much volume to create any pressure for the transfer ports to work properly.

 

[DJP]

Try preheating the cylinders with a propane torch. I can't tell if you have glow plugs but a little heat may be all that you need to fire it up.

 

[Swifty]

Bigrigbri, the crankcase is filled up a lot with the main bearing and the caps on either end extend in a fair amount, so all up there is not a lot of volume in the crankcase.
DJP, I tried preheating with my heat gun, but still no luck.
I wonder if the ether ended up evaporating a bit from my fuel mixture and making it too weak.

Paul.

 

[Mechanicboy]

Hi Paul, take contact with Ronald A. Chernich who live i Australia, he can tell you how to buy the diesel fuel or where is ether available if you want to mix own dieselfuel. And he can tell you how to start the diesel engine. His contact e-mail: [email protected] or phone +61 7 3365 4310

Ron's homepage: http://www.modelenginenews.org/

Nice work of the twin diesel engine.

 

[Mechanicboy]

It looks to me that the crankcase has far too much volume to create any pressure for the transfer ports to work properly.

The volume of crankcase has no affect on the engine..

Duke Fox: "Reducing the crankcase volume of a 2 cycle model airplane motor will improve its power." My observations didn't jibe with this theory. so I devised a test. I fitted all unported cylinder and piston into a rear cover so I could pull the piston in or out while the motor was running, thus varying the crankcase volume. Result: A very slight increase in R.P.M. as the crankcase volume was increased. This I didn't expect, so the test was repeated with several other Fox motors - and a couple if brand X motors. In every case maximum R.P.M. was achieved with somewhat greater case volume than stock. Conclusion: The "authorities" on hopping up a motor were just plain wrong.

 

[Swifty]

Thanks for the information Jens,

Paul.

 

[Lawijt]

Some diesels are very hard to start.Always starting with & very rich carb setting & low compression. When he starts or try to start put the compression a little higher.
When he runs,lean the carb & put the compression higher. This is how I make my fuell:

-45% Ether
-30% kerosene or diesel
-25% Castor oil.

If you want , you may take 2% ignition improver like Amyl Nitrate. So the engine will runn faster with less compression.
I don't know how you start the engine?? With you fingers?? A startmotor for model airplanes will help a lot.
Also before starting , put some fuell in the exhaust ports.
I hope this is helpfull for you.
Also you can find here some solutions:http://www.modeltechnics.com/diesel.htm
Barry

 

[Swifty]

Hi Lawijt, ether is just about impossible to obtain in Australia for domestic use. I think that it might be used for making drugs or something else illegal.

My next step will be to see if I can get some John Deere aerosol starter, this is high in ether content, and I will try making my own fuel again.

Paul

 

[Lawijt]

Ok , you mix the oil & the diesel or lamp oil or kerosene & go to your drugstore.....Ask them to put the ether in that mix & mixed for you.
Ether is used like drugs , but here in Belgium I can buy it like coca cola....

 

[canadianhorsepower]

The volume of crankcase has no affect on the engine..
Conclusion: The "authorities" on hopping up a motor were just plain wrong

Mechanicboy,
I don't know were your getting your information but they are 100% wrong. Primary compression ratio on a 2 stroke is one of the most important thing to take care of. I don't doubt the fact that you did some experiment to generate an opinion. Thing is primary compression ratio also include transfer port volume. Therefor a big crankcase and small port volume would give you the same result as a small crankcase and large port
will give you the same volume ratio , but far far away the same engine performance. A considered good crankcase ratio is between 1.2 to 1.5.
I never agreed in having a twin using a single carb with out having any mechanical way to close the intake port "reed valve" On a big "250 cc" the intake track and piston skirt are being enough not to have a bad effect on your intake wave. On something this small piston clearance is just as important as the comp ratio

 

[Mechanicboy]

Mechanicboy,
I don't know were your getting your information but they are 100% wrong.

Are you sure?

Here is link http://modelenginenews.org/people/duke/dm8812.html

Duke Fox was a model engine designer and produced the Fox model engines in U.S.A..

And the other link about crank case compression in 2 stroke engine: http://modelenginenews.org/etw/2s/index.html#A7

 

[canadianhorsepower]

Are you sure?

sure at 150% these article could have been good in 1988
but a lot of water went under the bridge since. Sure enough
if your intake port area is max for the crankcase volume you want have any effect. The 2 stroke have evaluate so much in the pass decade, incredible
.Just try to answer these question, why does almost all good 2 strokes
motor come with full crank now, hand did you ever think that a 2 stroke could be so efficient that it would produce more power and less pollution that a 4 stroke does?

cheers

 

[gus]

Some diesels are very hard to start.Always starting with & very rich carb setting & low compression. When he starts or try to start put the compression a little higher.
When he runs,lean the carb & put the compression higher. This is how I make my fuell:

-45% Ether
-30% kerosene or diesel
-25% Castor oil.

If you want , you may take 2% ignition improver like Amyl Nitrate. So the engine will runn faster with less compression.
I don't know how you start the engine?? With you fingers?? A startmotor for model airplanes will help a lot.
Also before starting , put some fuell in the exhaust ports.
I hope this is helpfull for you.
Also you can find here some solutions:http://www.modeltechnics.com/diesel.htm
Barry

Hi Barry,

Been looking for this formula for a lomg long time.
Went fishing this wek end. Gus was champ for Saturday. Three Snappers.
Today --------Gus is zero catch. The last spot before pack shop was good for my mates. Had good HongKong Steam Grouper(2kg)

 

[mu38&Bg#]

In the realm of model engines where intake, crankcase, and transfer tuning only applies to a very small segment of engines under 10cc, crankcase volume is irrelevant. Regardless the original Lobo Pup design ran fine!

If using starting fluid you have to verify the ether content. Some can be as low as 30% ether which is essentially useless. John Deere fluid can be considered 100% ether after the propellant boils off. If the cylinder is not holding pressure well it will be difficult to start. I have a tiny 0.1CC AE engine and it starts and runs fine with off the shelf model diesel fuel with 35% ether in it.

Greg

 

[Lawijt]

I'am happy that I help you Gus. Too bad that you don't have a great fishing week-end. So you have to go to the supermarket. But who knows , maybe we meet & we will fish togheter?

Barry

 

[DJP]

A power drill with a two pronged fork in the chuck should let you crank the engine until you find a combination of heat, fuel and compression that makes it fire. Flipping a prop by hand is the hard way and only works under ideal conditions, in my opinion.

My model engines from the distant past always had a glow plug so I'm still a fan of preheating a diesel to get it started. On a farm my uncle had a single cylinder bulldozer. There was a small tube in the head which held a burning (glowing) piece of paper and with the big flywheel cranked by hand it would start.

Just a thought for your consideration.

 

[tornitore45]

In my youth I started plenty single diesels but have no experience with a twin.

How you adjust two contrapistons, one is finnicky enough.

 

[Swifty]

I made a two pronged fork to fit my battery drill, but still could not get it to start. I think that the main problem is the correct fuel.

Paul.

 

[Mechanicboy]

If you want , you may take 2% ignition improver like Amyl Nitrate.
Barry

Near impossible to buy the Amyl nitrate. Use Glassfibre hardener who has this name Methylethylketone peroxide, Add same amount 2% in the fuel.

You can use the basis fuel such as this: 1 part kerosene, 1 part ether, 1 part castor oil.

Kerosene can be replaced with lamp oil or Diesel (fuel for diesel car) if kerosene is not available there you live.

To start the diesel engine, flip the propeller fast as possible to generate heat of compression, also not same as you are starting the glow plug engine.
Do not overcompress the engine, it will make difficult to start the engine.

The attachment of your first diesel engine, how to operate the model dieselengine.

View attachment Your first dieselengine.zip