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Starting a Diesel for the First time Tips and for Breaking in

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Starting a Diesel for the First time Tips and for Breaking in

Post  RUDiesel on Sat Dec 15, 2012 5:34 am

Hi,

I am very new to these mini engines, in fact I have never run one before. But I am very interested in learning how to turn one of these on properly and I have read a bunch on making fuel mixes and starting these engines.

I recently bought a brand new diesel bomber 049 from cox along with a diesel fuel line and a 5x3 prop. I made my own fuel mix using only starter fluid of about 30% ether, rest heptane, and castor oil and cetane booster. This is so that I could keep the ether content high to get it to turn on the first time (and break in). I read that the heptane acts as kerosene, which is why i didnt add any K1 to the mix.

I mounted the engine and tried to run it (im using a small bottle as a "fuel tank". My priming method was to put some fuel into the fuel line to go into the engine and start it using the spring starter.

I tried this many times (for over multiple hours, repriming and what-not) and even changing the compression (increasing and decreasing the compression) and opening and closing the needle valve, in small turns, I was UNABLE to get the engine to start.

Again I am very new to this sort of engine so I do not know much, If you could explain things in detail as to what I should do it would be very helpful. I am interested in getting involved with these sorts of things.

Thanks

RUDiesel
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  Surfer_kris on Sat Dec 15, 2012 5:43 am

Okey, here are some advice;
- use a larger prop, a 7x3 or 7x4 is a good match for a diesel (the 5x3 is for glow only).
- make sure the teflon gasket is sealing, if not, then simply though it away (very far) and use a disk made from a thin sheet of brass instead.
- don't even connect a fuel tank for the first starts, get it run out on a prime first.
- prime the side of the piston only (with piston high enough to plock the exhaust), never prime the intake.

Begin with the lowest compression setting, prime the side of the piston only and flip a few times. If it doen't fire straight away then prime again (only the side of the piston) and use one hand to increase the compression ratio slowly while flipping the prop over with the other hand. Continue like this with small primes and slow increase of the compression ratio until it fires.

I would also recommend a commercial fuel for the first starts so that you know how a good fuel should work, save the homebrew for once you get a hang of it.
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  RUDiesel on Sat Dec 15, 2012 6:38 am

Ok, Thanks. I can't get a hold of those bigger props at the moment. The gasket appears to be sealed since its brand new. Does the fuel mix sound ok? Just starter fluid from the gas station, pure castor oil, and cetane booster?
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  Kim on Sat Dec 15, 2012 7:34 am

Hi,

I'm by no means an expert, and can't add to Kriss' excellent advice, except to emphasize his suggestion on buying commercial fuel mixed for these engines.

I don't know if you're here in the states, but if so, you can get fuel from Davis Diesel @ http://www.davisdieseldevelopment.com/ , and Doctor Diesel Eric Clutton @ http://www.cafes.net/doctordiesel/

A quart of their fuel from either of them would allow a lot of running time for you to get to know your engine.

Best Wishes, Kim
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  Surfer_kris on Sat Dec 15, 2012 8:20 am

RUDiesel wrote: The gasket appears to be sealed since its brand new.

That is certainly no guarantee, the design is faulty from the beginning. Teflon does not make for a good gasket, it is very slippery and cannot take heat well. The edge of the head will very effectively pinch though the teflon and cause a leak. This means that they are always leaking a bit and this makes the engine very hard to start. There is also a big risk of setting an over-compression then, in order to get the engine to fire, and you might end up breaking the crank.

You can check for leaks by spraying the head with soap water and check for bubbles while turning the engine over slowly. It should hold the compression at TDC for a few seconds if everything is in order.

You can easily make a new disk from a thin sheet of brass. Aluminium from a soda can also works, in principle, but it will suffer from fatigue earlier and then break after a few flights.
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  RUDiesel on Sat Dec 15, 2012 8:24 am

Hey Thanks for the links,

I've seen those two brands before and I was thinking about buying from them to start off but since I didnt see any PayPal or secure online transaction method I decided to just try making my own from the blend Eric has on his website.

Now if there was an ebay or amazon seller, that would be great.
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  RUDiesel on Sat Dec 15, 2012 8:27 am

Thanks for the reply on the gasket. I was not aware of that. I dont have the engine in front of me but it is something ill check into.

I appreciate all the help so far.
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  RUDiesel on Sat Dec 15, 2012 8:31 am

I dont intend to fly this engine on a plane. My end result is to actually put it on a small toy car but also (eventually) have it run off of B100 as well. An odd concept, but it's a project for school. I've done my research on the B100 and the oil we used is easier to burn than kero since it has shorter carbon chains.

Have you heard news of people running on different blends or even B100? I saw a youtube video once of a guy running a Norvel engine, but thats all I've seen.
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  Surfer_kris on Sat Dec 15, 2012 8:48 am

The diesel fuel for our model engines has been developed for a very long time and you cannot expect to improve on that. If you just want to experiment with different fuels, for the sake of experimenting, you might be better of with a glow engine and keep some power on the glow plug all the time. That heat will help to ignite most fuels, unlike the model diesel that relies on compression alone. A regular glow head should fit the engine that you already have, and it doesn't cost much, so you could begin in that end instead. Get it running with power on the plug then remove the power and see if it stays running. The compression setting is then altered by changing the number of head shims.
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  RUDiesel on Sat Dec 15, 2012 9:01 am

How would I attach the glow head and how would I remove the shims? They seem like they're stuck right on there good.
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  Surfer_kris on Sat Dec 15, 2012 9:07 am

You simply remove the head and replace it with this one from coxengines.ca :

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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  RUDiesel on Sat Dec 15, 2012 7:32 pm

Thanks for all the info so far.

I plan on buying 2 wrenches and an 8x4 prop. But just to be clear, by replacing the head with a glow head instead of the diesel head, wouldnt that mean I would have to use nitro fuel? Or can glow engines run both the diesel fuel and nitro fuel. I was under the impression if you had a glow head (thereby making it a glow engine) you would have to run nitro fuel because it is more easily ignited and the diesel head with the contra screw on top used diesel mix because it needed more compression.

This is important because the B100 mix that I will use once I get this running is not flammable in the bulk fluid but in droplets it is combustible. I have tested the flash point and fire point of my fuel as well and if you need the numbers I can look them up too.

This will matter, of course, when I can actually get it run on the standard fuel mix.
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  RUDiesel on Sat Dec 15, 2012 7:42 pm

And just to confirm, is the fuel mix that I created (see original post) a good fuel to use? In other words, will it work to start the engine and break it in? You can assume I am a chemist of all sorts so I have no issue making my own mixes and what not.

I just want to eliminate all extraneous reasons and understand the one or two reasons why it is not starting.

Could it be the 5x3 prop, the fuel mix etc? Assuming the teflon gasket is fine just for starting? I tested it and it is sealed by the way. Why would a smaller prop not allow the engine to start? I am still getting an 8x4 but while I am waiting for it to be shipped I still want to play around with the engine to get it to start.
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  Surfer_kris on Sun Dec 16, 2012 1:43 am

The difference between a diesel engine and a glow engine is the glow filament, and the fact that you cannot adjust the compression setting on a glow engine while it is running. The lack of a glow filament to aid the combustion on a diesel also means that it needs a little higher compression ratio in order to fire. The disel engine is thereby much more sensitive to the fuel, you absolute need a good amount of pure ether in the fuel as this is the part that will ignite. On a glow engine you can power the glow plug and then run with a variety of fuels. It is only methanol though (and possibly ethanol) that will keep the glow plug lit by catalytic activity so that the power can be removed once the engine has started.

A good fuel mix is 35% of pure ether, 25% castor oil, 39% kerosene and 1% ignition improver. If you don't have pure ether, and enough of it, the engine will not start as it is the ether that ignites "first" and then that heat can make the kerosene burn too.

A larger prop gives you a flywheel effect that helps the engine stay running. The optimum compression setting is also lower on a larger prop, so that helps too. Running a small prop is dangerous on engines that where not designed as diesels, the compression ration will be higher and then something wil break (usually the crankpin).

So get a 7x3 or a 7x4 prop and commercial fuel. Better yet, find someone nearby that has experience with both glow and diesel engines.
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  RUDiesel on Sun Dec 16, 2012 3:01 am

Thanks, that was very informative, I'll read up on some of those things you mentioned. I heard about the methanol being necessary for catalysis, which is why i questioned the use of diesel fuel in those engines.

And yes, I have asked around in my area, but no one seems to know anything about model airplane engines let alone small diesel engines. Only a friend of mine uses nitro engines for the cars, but he said that was a few years back.

I made some orders online for a larger prop etc. When that comes in I'll try and put it all to work! Thank you so much! I'm glad that you guys are kind to help a beginner (who has no experience with these things) understand all of this.
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  John Goddard on Sun Dec 16, 2012 9:02 am

Bear in mind I've only ran one diesel a few times so
What do I know? But
1, Cox advises running as a glow engine until it is broken in.
2, would you take delivery of your new Ferrari and knock up
Some fuel in your garage instead of going to the petrol/gas
Station...?
Run it in on glow then buy some proper diesel fuel.
Very Happy
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  Kim on Sun Dec 16, 2012 9:14 am

John Goddard wrote:Bear in mind I've only ran one diesel a few times so
What do I know? But
1, Cox advises running as a glow engine until it is broken in.
2, would you take delivery of your new Ferrari and knock up
Some fuel in your garage instead of going to the petrol/gas
Station...?
Run it in on glow then buy some proper diesel fuel.
Very Happy

From across the Pond...True Wisdom from a fellow Cut-Finger Brother !!!!!
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  Surfer_kris on Sun Dec 16, 2012 10:43 am

There is no need to run it in on glow, Diesel engines were used even before glow engines were invented. I wonder how they managed then... lol!
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  RUDiesel on Sun Dec 16, 2012 4:55 pm

Yes, a lot of this stuff happened before I was born. I am only in my early twenties. I never ran a glow or a diesel before, but I like engines a lot and I want to learn how to run these. The feeling when you get an engine to run for the first time is just priceless. I worked on a stirling engine before and when that finally worked it made me want to move onto tougher projects like these.
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  gcb on Sun Dec 16, 2012 8:54 pm

RUDiesel wrote:Yes, a lot of this stuff happened before I was born. I am only in my early twenties. I never ran a glow or a diesel before, but I like engines a lot and I want to learn how to run these. The feeling when you get an engine to run for the first time is just priceless. I worked on a stirling engine before and when that finally worked it made me want to move onto tougher projects like these.
Cox engines were designed for glow. People have created diesel conversions which require some stronger parts but basicly it is designed as a glow engine which has different firing characteristics than a compression ignition (diesel) engine. Cox engines are easily broken if over compressed as a diesel.
If you are going to experiment with bio-diesel fuel or something similar that requires higher compression to fire, you might consider getting a purpose-built diesel...such as a PAW that can better handle the stresses involved.

Of course the choice is yours. Good luck either way.

George
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Re: Starting a Diesel for the First time Tips and for Breaking in

Post  Jason_WI on Sun Dec 16, 2012 9:27 pm

Get a HD crank shaft or a large splined car crankshaft with the case. These can handle extra stress but they can still break if over compressed. Look for a cox engine parts lot on eBay that has crank cases and piston/cylinder. This way you have parts to experiment with and you can get them cheaper than buying single engines.

This is a small lot. Not sure what your budget is but I wouldn't go more than 25 on this one.

http://www.ebay.com/itm/LOT-OF-MISC-COX-049-PARTS-TEE-DEE-AND-REED-/300834793726?pt=US_Character_Radio_Control_Toys&hash=item460b26a8fe

And you can sell those TD 049 needle valve springs as they are pure unobtainium.

Jason


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