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Test #6

Etherless mix:

1 part acitone
1 part 87 octane gasoline
4 parts mix #2

To get this to start I needed more compression so I took the head gasket out. Also while messing around I managed to drop the contra piston out and it turned sideways in the cylinder. I pulled the head and put it back in but the O rings are going to need to be replaced soon. The head apears to be leaking slightly so my compression probably isn't as good and this is going to skew my tests somewhat. Davis heads are only good for so much compression because of the dome shape in the contra piston. I believe we need more compression to start eitherless mixes.

8,800 WOT. Might be reduced because of the compression insted of the fuel.

Idle 2,000

Throttle up not so good unless I overcompress.

Also the engine sounds like it is knocking some but that is what it takes to run this mix.

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Test #7

Ambiant temprature 59 degrese F.

Either less mix:

Mix #2 only ( 2% cetain, truck diesel, 20% weedeater oil )

Needs maximum compression to start and an electric starter. Once it starts it is hard to grab the allen wrench ( Davis Head ) and put down the starter fast enough for it not to knock hard while you are trying to reduce compression.

I don't think priming with either would make this start by hand because it would be way over compressed and if you backed it off it would be way undercompressed when the diesel made it up the line. I might try the propane torch on the head and see what that does.

9,400 RPM max but won't idle so well at this reduced comression setting

2,000 idle but will get cold if left very long at 2,000 and will not throttle up well.

If it is kept above 3,000 and when trottling up only go to about 3/4 throtlle ( which is about 9,000 rpm ) performance seem OK. Also to get decent performance a little over compression helps. It really isn't over compressed exept at extended WOT. I think this could work becuase I only use full throttle for bursts but not constantly. Also it seems to help to run it a little rich to get a good throttle up after a bit of idling.

This would be the cheapest fuel here in the USA I think.

This might work better on an engine that has higer compression ability. This could be achieved with a few modifications and might be possible on a stock PAW.

I'm going to try it a little more.......

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Test #7 continued:

Warming up the head with the propane torch makes it start without touching the compression screw. I starts righ away with the electric starter. Hand starting may be possible this way. There are small pockett size propane torches availble. This is good!

3/4 throttle is ove 9,000 rpm and WOT when it is completely hot will give more.

Throttling. You get about 30 sec. of slow idle before it begins to get cold and not want to go back to full throttle without missing.
If idling is kept above 3,500, which is no problem in the air, throttling is much better.
Extended taxiing before take off could be a problem without warming the engine by holding the plane while you rev the engine.
I don't think flying would be a probem.
I would set the throttle to go to 3/4 open and get the last little bit with the trim for all out engine speed.

I think I can fly this mix. I will try it when the engine is all back on the plane.

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It is possible that substituting Kerosene for my truck diesel in the above tests will improve things. I might try that next. I have to go buy some first. It isn't all that easy to get here.

I don't really know that it will help though because the volitility of the gasoline and the acitone didn't really seem to help at all. The only advantage to Kerosene seems to be it's volotility unless it has a better auto ignition temprature. I have to go back in this thread and see if I can find that.

At leas now I have a real diesel engine that burns real diesel fuel!

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Very near the Holy Grail!!

Test #7 continued:

I put the head gasket back.

I got a hand start on Mix #2! I heated the head and after a couple of flips away she went!

I fidled with the settings a bit and then added about 2 ft. of exuast tubing. This really seemed to help. I'm not suere why yet but the back pressure is helping.

Now it runs great! It goes to wide open without missing and idles nicely too.

It will idle at 2,000

WOT 9,400!!!

NO EITHER!!!!!!! TRUCK DIESEL!!!! YEAAAHHHOOOOO!

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Yes, the engine should start hot on etherless fuel. No.2 Diesel has a higher autoignition temperature than kerosene. It's one reason I haven't tried it yet.

My test bench amplifies any knocking my engines make. It's so loud that it had me concerned in the beginning. The PAW 35 clatters so much below 5kRPM that I think the rod is loose. Above 5k it sounds really nice.

If detonation is autoignition of the fuel mixture, what is happenening in our engines since they have no spark?

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"So when I crank up the compression on my Norvel, I get this sharp cracking sound in perfect sequence to the RPM. I do this often, because I get more RPM/power. Most, and likely good advice, is to back off the compression till this "ping?" sound disappears. So if we compress too much, we are advancing the timing, causing pre-ignition, causing detonation causing the ping? "

Andy,
The sharp crackling sound may just be efficient combustion- the motor "ON song", if its a metalic clinking then it is as you say, but if its a nonmetalic sound its ok.
Stewart

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Any time the mixture fires too much before TDC the pressure will go out of sight making the noise. The flame is burning and the presure is rising and so is the piston the results in even faster burnig or should I say exploding.


Gas or diesel it really doesn't matter. If the mixture lights of before the spark in a gasser the spark plug isn't doing anything.

Diese engines knock a littel especially Direct Ingection but since there is only a little fuel in there ( the injector has just started injecting )when the knock occures it doesn't hurt anything and diesels are built so much stronger anyway.

Unlike any other diesel our model engines have a full cylinder of fuel and air on the pistons way up so we can get much worse knock than any real diesel.

Real diesels have nothing but air on the compression stroke so they reall can't detonate the same way.

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Chevy43,

A big congrats.

No ether and locally available ingredients.

Weed eater oil. Please, what brand, part number, where'dya get it? Link?


Greg,

Diesel ignition timing. Affected by compression setting? More compression causes the fuel to ignite earlier in the cycle. Too much compression and the fuel ignites too soon before TDC causing noise, hammering, damage etc.

Stewart,

I can get the Norvels to purr, quiet and smooth. Like a diesel is supposed to do, run much quieter. But power is down. Cranking up the CR, gives much better power but the engine is NOISY, not what diesels are supposed to sound like. Been doing it for some time with no damage but the same engine, on glow and glow sized prop is much quieter. This may be characteristic of Norvel only, perhaps.

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Andy it happend to be Homelite 2 stoke oil but I doubt it makes much difference

I just ran onother batch of diesel through it that I used crank case drainings out of my Cummins at about 23% oil to fuel. It worked fine to but RPM was down slightly maybe because I mixed in more oil this time and the oil doesn't burn like the diesel fuel.

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Chev,

So in our small engines, a bit of knock/noise is normal. And yes, I've been running the Norvels noisy for some time with no damage. Only when I went to an all oil fuel did my rod protest. Could have been due to extreme compression just to get a run.

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What I think would make our diesels really run perfect would be a temprature compensated contra piston.

I'm thinking it could work like a thermostat on a truck. Maybe a wax pellet that expands to and reduces compression or a bimetalic type of thing. I'm going to start thinking about it.

What is happening is that the engine is getting cold while idling and hot while running ( fairly obvious ) The cold engine doesn't want to come back up to speed. The colder engine would run fine if it had a bit more compression.

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Yes Andy I agree.

Most large diesels will have more power at advanced time to a point. But like everything there is a compromise to get the engine to live longer. Advance the timing too much and head gaskets and bearings begin to give trouble.

Treven.

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Andy,
I too run my diesels at the high end and they too get the crackle in the exhaust- on song. this is whats needed to get max efficiency but as you say it sounds harsh. This is ok as long as the RPM's havent dropped , this is the first sign of overcompression.

chevy43,
As gkamysz says kero has a lower auto ignition temp and will require a lower compression setting to start and run.
Stewart

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Stewart,

Do you happen to know what the differece is in Auto Ignition temps? Kerosene is Obsenely priced around here - $5 a gallon vrs $3 for diese which I can get around the corner.

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chevy43,
Not off hand, but its enough to make quite a difference in the compression requirements and ease of starting, the starting could also be because of kero's lower viscosity allowing it to atomise better/easier. I also have found the exhaust is cleaner on kero over pump diesel.
As I hand start all my diesels I dont use less than 20% ether fuel with 22% lube oil-was castor but will be useing the modded vegi oil from now on to offset the ether cost, also my test runs with the vegi oil gave easier starts and a cleaner exhaust - not as much black oil, it also cleaned the piston crown from previouse fuel mixes:)
Actually I hand start all my motors with the exception of my OS40 4st, starter use is mandatory with this as it BITES even without the glow connected.
Stewart

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Kerosene around here was 20 cents less when I bought it a couple weeks ago.

Try flying the etherless mix. You may be a bit surprised. As soon as the revs increase slightly you may experince combustion ceasing completely.

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Well I got 12 minuets run time @ 8,400 rpm on a 4oz tank of my extra black brew. The fuel is going in black and it is black comming out :-)
I will have to run this with an exhaust piped to the back of the plane which I like anyway. Also there is a lot of white-ish smoke which I think is cool for flying. Some people have to buy a smoke system and I have a built in one.
It starts by hand after warming the head with the prpane torch and about a 1/2 turn on the comprssion screw.

Thanks Stewart,

I might go down and buy a gallon of Kerosene next time I'm near the place that sells it.

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I can hand start my black brew without the torch now. I just prime the line with davis and get it started. A little quick chocking and compression adjustment and it will transfer over to the diesel.

This is just great!!!

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I looks like my fuel costs will be $3.15 per gallon for diesel and 1.60 for 2% cetain boost and free engine crank case drainings for a total of
$4.75 a gallon! That sure beats $27 for Davis fuel.

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Good to see this thread still going strong with lots of good input and results.

I managed to put one of my PAW back together. After a couple of tries at "growing the piston" I managed to get a piston/cylinder that has some compression, not like new but certainly better than before. Time will tell how long it lasts. Next time it will be time for a new set or a rebore.

I have been continuing my tests with B20 biodiesel. Using various mixes of B20 biodiesel and 5 to 10 percent ether and 1 to 3 percent Amsoil Cetane boost I find little difference in any combination of these mixes. I have run about 1.5 litres of the B20 through the engine, it runs reasonably well, a bit better on the 10% ether mix but power is down from the more traditional fuel mixes. Lots of oil in the exhaust and some white smoke as well.

Also, I have been tearing the engine down after a days running to check for wear etc. I am getting a nice bunch of carbon/soot buildup on the pistion crown all the time but there does not seem to be any appreciable wear. From the amount of oil in the exhaust and the white smoke it is obvious the fuel is burning (the engine runs) but there is a lot going through that isn't getting burned. I am guessing primarily the biodiesel component of the fuel.

Perhaps the 20% biodiesel in the mix is simply too much oil. I haven't yet but will try mixing straight kerosene to reduce the biodiesel % down somewhat to see what effect that will have performance and wear.

With all the good success using the home cooked vegetable oil I spent some time rereading my original post with the quoted Aeromodeller article and readin up on biodiesel. I have come to the conclusion that the process in the Aeromodeller article is a simple method to produce what is essentially biodiesel from the cooking oil; perhaps not as efficient or as thorough as the lye/ethanol method more commonly used by the home biodiesel brewer. The two processes are too similar to be anything much different. Now that is just an educated guess as I haven't taken the time to understand both processes enough to say absolutly yes but a cursory look has me thinking that way.

It is certainly neat to take some pump diesel fuel, add a wiff of ether and cetane boost and make this old PAW run much to the dismay of some old time diesel users.

Someone asked about auto ignition temperatures, Kerosene 210C (410F), Gasoline 280C (536F) Methyl Alcohol 385C (725F) Acetone 465C (869F) Naptha 550C (1022F) to list a few (found from various searches on the net and for most materials the given value is about the middle of the range of temperatures found. Interestingly I found the auto ignition temperature of Mineral Spirits (paint thinner) is about 254C - might make a cheap substitute for kerosene or perhaps a blend might be better than one of the other alone; I will have to try a mix and see.

Tests continue.

Cheers, Graham in Embrun near Ottawa Canada

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" With all the good success using the home cooked vegetable oil I spent some time rereading my original post with the quoted Aeromodeller article and readin up on biodiesel. I have come to the conclusion that the process in the Aeromodeller article is a simple method to produce what is essentially biodiesel from the cooking oil; "

GrahamC,
I have to dissagree . the process of makeing the modded vegi oil is the opposite to makeing bio diesel
To make bio diesel from vegitable/cooking oils, the glycerine is stripped from the molecules- decreaseing the triglyceride count on the molecule , wereas in makeing the lubricating oil we add glycerine to increase the No of triglycerides on the molecule, 2 entirely different directions in the process's.
Stewart

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That explains why it will be hard to find a single component fuel/lubricant.

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That was my first thought too Stewart but I am not so sure.

Just because the process adds glycerine to the mix before the oil is "cooked" doesn't mean we are actually adding more to the oil. The process of making biodiesel uses an alkali ( Potassium or Sodium Hydroxide) and an alcohol (Ethanol or Methanol) a bit of water and then heat with continuous mixing. In the Aeromodeller article he used washing up liquid/ dish soap (an alkali) and Glycerine (a heavy alcohol) a bit of water and then heat with continuous stirring (mixing). I wish I knew more about chemistry at this level as I would truly like to have a better undestanding of what is happening but I seems to me that the two processes are so similar that the end product is likely (or very close) to the same. I am still not convinced either way however.

In any respect, I am going to "cook" up a batch of veggie oil and have a try. Theory is fine but the bottom line is what works, works. I must go back in this thread and re-read Andy's comments on his use of biodiesel.

In reading some of the web sites that have details of using vegetable oils as lubricants and sites on biodiesel I ran across a figure of the effect of adding biodiesel to diesel fuels; that figure was that adding 1% biodiesel to regular diesel fuel increased it's lubricity by 65%! Now that seems to be a fanastically high figure but having no way to refute it we either have to accept it or take it with a grain of salt. Even if you figured it was pumped up by 100% then that is still an improvement of over 30% with just the addition of 1% biodiesel. On that same web page was a mention that France (was planning to or has already) mandated the addition of 3 to 5% biodiesel to commerical diesel fuel to counter the effects of the loss of lubricity in very low sulphur diesel fuels not to mention the environmental benefits.

cheers, Graham in Embrun near Ottawa Canada.

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Graham.

I have to agree with SGC (Stewart) on his option that making BioDiesel (Transesterification) and the process of make the Veggie Oil are opposite processes. Perhaps your experiment of making a sample of the Veggie oil may illustrate this for all of us. I do see your argument and appreciate your reasoning for your conclusions.

If you are correct then at the end of the 1-day settling period after boiling the oil you will have two distinct layers of material. If you are correct then these layers will represent 1. biodiesel fuel and 2. stripped glycerin molecules.

If you are wrong then there will not be two distinct layers, but simply a small deposit of material that did not bind during the cooking process that has settled out to the bottom of the container.

I think Stewart is correct, when making the Veggie oil you are trying to make a thicker oil by adding glycerin and saturating the veggie oil with more glycerin molecules thus increasing the size of your oil molecule. Glycerin is a very slippery thick material; by adding more glycerin you’re improving the lubricating properties of the oil and increasing the viscosity of the oil.

Since a strong detergent is used to make veggie oil, that tends to make me think that the glycerin is being added onto the exiting molecules of the base oil. The detergent has a polar structure on one end of the molecule and a non-polar structure at its other end thus binding the added water (polar) and glycerin to the existing oil (non-polar).

This maybe helpful: http://en.wikipedia.org/wiki/Transesterification

But you have made one discovery that I suggested many pages ago on this thread.

Your Quote:

I found the auto ignition temperature of Mineral Spirits (paint thinner) is about 254C - might make a cheap substitute for kerosene or perhaps a blend might be better than one of the other alone; I will have to try a mix and see

End Quote:

I think you’ll find that BBQ Charcoal Lighter fluid maybe a good fuel to mix with your veggie oil. I have been opening bottles at every store I shop at to smell the contents of the BBQ Lighter Fluid. To my nose, they mostly smell like paint thinner. I’ve smelled about 10 brands, but they all smell a bit different. Well it’s hard to tell from day to day, but the result are similar. It appears that 3 or 4 brands are available at some stores. Some brands are no-odor brands, and have little odor but cost twice as much. One brand advertised that it had not mineral oil contents, but was a biofuel?

I think it would be great if you could make a batch of your veggie oil and mix this with some BBQ Lighter Fluid. I bet this mixture runs well and smells great! The nice thing about lighter fluid is you can buy small amounts at one time to test many different brands. If you do a MSDS search for each brand then you will be able to determined the basic makeup of these fuels.

Thanks for posting your experiment. This has been enjoyable learning from you efforts.

Kelly