Fieldlines.com || Make your electricity from scratch!

Front Page - [Homebrewed Electricity-- (wind) (solar) (hydro) (steam) (controls) (storage) (mechanical)] - Classifieds - Site News
Everything - Newbies - [Remote Living-- (housing) (heat) (light) (water)] - Reviews - Diaries - Our Products

Ethanol Engine (updated)
By Andrew, Section Homebrewed Electricity Posted on Fri Jun 27, 2003 at 11:39:53 PM MST
Ethanol powered lawn boy.

Hi,
I just got a old stihl weed eater motor. The thing was trashed! After an afternoon of fixing up the piston, the recoil unit, I got it running! Just need to adjust the carb to allow lower idling speeds. The nasty oily smoke though just screamed for the engine to be converted to ethanol. (I know one distributer down here in Colorado Springs, on 8th street I think) So, I was told that I need to adjust the carb for a richer mixture of ethanol/oil mix. How do I go about this.
Finally, anyone know a alcohol soluable oil for 2 cycles. If so, what proportions should I mix?
Thanks
-Andrew
P.S.
The Machining process of the tiny ethanol engine is progressing! Got the pistons and the crankcase done. But when I went to machine the head I found out I have a chipped reamer! Looks like I'll have to take it in the shorts and buy a 3/8ths reamer and a 1/2 one too. (Anyone know any good machine tool places for internet order?) (3/8 needed for valve assembly) I'll keep you posted as both projects progress.
-Andrew

Ethanol Engine (updated) | 24 comments (24 topical)

Re: Ethanol Engine (updated) (none / 0) (#1)
by Demetri on Sat Jun 28, 2003 at 12:21:43 AM MST

Castor works, and there are a couple synthetics and synthetic/castor blends, though I don't know if they'll offer enough protection for the weed eater motor. Most model airplane engines burning the same stuff use 10-30% oil <I'm not a small engine mechanic, nor a fuel chemist, try at your own risk>. You might find it sold separately from the fuel at hobby shops(or buy the fuel pre-mixed, with nitro!) for those who like to mix their own fuel. Good luck. Demetri
Uncommon sense required.

Re: Ethanol Engine (updated) (none / 0) (#2)
by Brian on Sat Jun 28, 2003 at 01:07:01 AM MST

Sorry I took so long but I have been busy with other projects. That weedeater will run just fine on ethanol. Adjust for about a 9:1 air/fuel ratio which is richer compared to the 12:1 mixture used in gasoline engines. Just find the mixture adjusting screw on the carb and back it out to richen it up. Run it for a while and be sure the plugs arent white. If they are, the fuel mixture is too lean and it will run hot. As far as the fuel/oil mixture, try to mess with the fuel/oil mixture ratio until it smokes just a LITTLE while on the throttle to be on the safe side. Now for the temps for your other project....I believe you said u were going for a 12:1 compression ratio. How did you figure this is what you will end up at? Dynamic compression ratio will be lower than the static compression ratio. I would have to see the intake and exhaust design to know what volumes to use to figure out the CR you will be running at. If you want, send me your latest drawing and I'll take a look and tell you what to use to compute the actual compression ratio. It doesn't make much sense to do the math on the temps until I have that. If you're sure it's 12:1, let me know and I'll figure the temps using that ratio. Keep us posted of your progress. I expect it will run just fine using a glow plug setup!

Re: Ethanol Engine (updated) (none / 0) (#3)
by Andrew on Sat Jun 28, 2003 at 01:26:27 AM MST

This is static I believe. I did it by just checking the heights. I'll send you the
dxfs. I'll post them asap. Thanks for your help.
I can change the compression ration if this is a problem.
-Andrew

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#4)
by Andrew on Sat Jun 28, 2003 at 02:59:10 AM MST

Well here is a pic of the rendered pattern but showing the hidden lines to reveal the piston and the crankshaft.

Sorry, it is big, admin could you reduce it again.

You can also see the glow plug and the coil at the top of the cylinder.
I do not have the exhaust or intake on this. I will do this upon request.

Keep in mind that this thing is a two clyinder machine, and I have only drawn up one cylinder to keep it simple.

Here is the dxfs of this...

"http://www.otherpower.com/images/scimages/248/crankcase_and_cylenderhead.dxf"

just right click it and hit "save link target as" or some thing similar.

It should start downloading. Open it with autocad or similar.

I can also put up a 3d cadkey pattern if yall want to do cool stuff with it (like spin the rendered model at any angle, etc. just another reason to get cadkey)

-Andrew

(Brian, the total stroke length is 0.4 the and the the cylender depth is 0.43 excluding the height of the piston (which if included the total height would equal 0.83) and the volume in the glow plug. I look forward to seeing the temp ranges. If you need the exhaust and intake, I will add them asap THANKS!)

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#5)
by Andrew on Sat Jun 28, 2003 at 03:00:56 AM MST

Wow, Admin did you change the code? It was posted normal sized! Thank you!
-Andrew

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#7)
by Brian on Mon Jun 30, 2003 at 02:42:05 PM MST

Sorry I haven't replied sooner. In order to figure out the dynamic compression, you need to take some measurements. How did you design the intake and exhaust?? The dynamic compression will vary greatly depending on how you set it up. Go ahead and post a description of your design and I'll tell you where to take your measurements from to figure the ratio.

BTW, if you want the picture to show up the same size on everyone's computer regardless of the resolution they're running at, use the HTML formatted option when posting and use the tag below. I'll use the filename engine.jpg but you can change it depending on your file name and server addy.

This will make the picture take up 80% of the screen width no matter what size monitor the person viewing it is using!! No more scrolling sideways!

[ Parent ]

Pictures, reducing them in comments. (none / 0) (#9)
by TomW on Mon Jun 30, 2003 at 03:26:09 PM MST

Andrew;

Sorry, I would gladly do that but Admin / Editors cannot alter comments in any manner other than deletion. And thats how it should be. Can't be revising ppls comments you know.

But i feel fairly confident your program should be able to output a smaller picture or you can learn the height and width tags for html in about 10 minutes.

Cheers.

TomW

The Truth is the Truth, even if no one believes it; and a lie is a lie even if everyone believes it

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#6)
by RobD on Mon Jun 30, 2003 at 08:00:58 AM MST

Nice Job! I have a Stihl chain saw that has run great for years. The fuel oil ratio is 50/1. You shouldn't get that much smoke out of it, I don't. Also 2 cycle engines are more prone to ceasure when the oil is RICH in the mixture. These engines also run on Hi-test gas. For those of you not familiar the difference in hi-test and regular is the speed of burning. Hi-test burns SLOWER than regular this prevents ugly things like pinging that can eventually burn a hole in your piston. I don't know the octane of ethanol but you might want to play with your timing if it is on the low side. RobD

Re: Ethanol Engine (updated) (none / 0) (#8)
by Brian on Mon Jun 30, 2003 at 02:51:44 PM MST

Ethanol has a higher octane rating that gasoline does so he shouldn't have any problem with pre-ignition.

You're right about the speed of combustion. Many people confuse a high octane rating for high volatility which is wrong. The octane rating is the fuels ability to resist knock, AKA pinging or preignition. The slower the fuel burns, the better it is at resisting preignition. The higher the octane rating of the fuel, the higher one can raise the compression ratio without preignition. A higher compression ratio creates more power!!

It will be interesting so see what fuel/oil ratio will end up working the best for this application. This is definitely a guess and check type experiment!! All very good points though! Brian

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#10)
by Andrew on Mon Jun 30, 2003 at 04:06:33 PM MST

I make the intake/exhaust on the drawing. I'm not really sure where to put them other than the exhause should be a little bit higher in the cycle than the intake.
I think one problem with high octane fuel though is the fact that with lean fuel mixures you will get detonation. I believe this you will also hear a "ping" because its the speed of the engine slamming down so fast that it get hit against the side of the cylinder. This is probably why most engines run on a rather rich fuel/air mix like 10:1
I think pinging starts for normal gasoline at about 18-22:1

-Andrew

(Could you post why and where the intake/exhaust is where they are.)

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#11)
by mkseps on Mon Jun 30, 2003 at 04:12:01 PM MST

Pure ethanol has an octane between 107 to 113. It is much higher than automobile high test gasoline. Gene

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#12)
by Brian on Mon Jun 30, 2003 at 05:08:00 PM MST

Hi, I'm guessing you meant that the intake and exhaust are labeled on the drawing file you posted. I wasn't able to open it so I can't comment!! Does Cadkey allow you to save it as a *.dwg file?

Regarding the intake and exhaust design....in a 2-cycle engine the fuel/air mixture is forced into the combustion chamber during the down stroke of the piston. During the upstroke the mixture is compressed. When the piston gets close to TDC, the glow plug ignites the mixture.....forcing the piston back down. As the piston moves back down, exhaust gases escape through the exhaust port while the fuel mixture re-enters the cylinder.

Regarding pre-ignition, you are correct for the most part. High octane fuels do not vaporize as well as lower octane fuels do. This lack of vaporization causes much of the mixture to remain as a liquid instead of the dry vapor necessary for efficient combustion. Since there is less fuel in the fuel/air mixture, the mixture is often way too lean....causing detonation and internal damage!! So in the case of higher octane fuels, it is the octane rating iteself that often causes the lean mixture, resulting in detonation. This is the reason you need to richen the mixture when burning ethanol.

However, most gasoline engines do not run at a fuel/air ratio of 10:1. Between 11.5 and 12:1 is the norm for most 4 stroke gasoline engines.

Hope this helps, Brian.

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#13)
by Andrew on Mon Jun 30, 2003 at 08:39:12 PM MST

Sure, I can do *.dwg files.
I was meaning that I haven't drawn the exhaust or intake on the engine. I really don't know the exact height of where they should be placed. Could you tell me how this is done? (what exact height should the exhaust and intake be.)

I'll post the *.dwg.

-Andrew

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#14)
by Andrew on Mon Jun 30, 2003 at 08:42:10 PM MST

Here they are.

Just right click and hit "save file as" or some sort like that.

"http://www.otherpower.com/images/scimages/248/ethanolengine.dwg"

Hope this helps

-Andrew

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#15)
by Andrew on Wed Jul 02, 2003 at 02:37:24 AM MST

Brain, whats the deal?
I posted the dwgs, and you haven't got back yet. Sorry to sound impatient, your probably just busy.
Anybody can look at the schematics if they want. I would bw happy to recieve any feedback.

Also does anyone know any good cheap machine tool places?

-Andrew

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#16)
by Brian on Thu Jul 03, 2003 at 12:47:43 AM MST

Yes, I have been busy....Sorry about that. I have been working on a prototype solar collector for OREC. Fun stuff!!

Regarding your drawings....very nice. The conversion worked just fine. How does Cadkey work for coil/spring drawings like those used for your glow plug drawing? Just curious if it's easier than the method used in AutoCAD. In AutoCAD, you have to use an AutoLISP to extrude a 2D object about the spring path to create the 3D solid drawing of the coil. Kind of a pain.....

Ok, now for the intake and exhaust. The exhaust port will need to be slightly higher than the intake port to allow the exhaust gases to escape just before the fresh fuel mixture enters the cylinder. You will want the intake port to be fully open just as the piston hits bottom dead center. When the piston reaches BDC, the pressurized fuel mixture will flow through the intake port into the combustion chamber for the power/exhaust stroke.

In order to make this work, you need to incorporate a reed valve into your design. It's essentially a one way valve that allows the upward motion of the piston to suck fuel in from the carb but not allow it to leave when the piston begins its downward motion.....pressurizing the mixture for injection once the piston moves past the intake port.

In your design, I see no intake port that will utilize the downward motion of the piston to pressurize the fuel. The fuel MUST enter the crankcase in a 2 stroke design, not through the top of the cylinder head.

I'll try to make some time in the next few days to tinker with your drawing and post the required design features.

Hope this helps. Brian

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#17)
by Andrew on Thu Jul 03, 2003 at 12:58:30 AM MST

Solar collectors... Tricky business

Thanks for the tips.

I do have a valve. I can't believe you didn't see it. Its that green thing sticking out the side. It has that yellow valve on the inside. It is a poppet valve instead of a reed, and the fuel intake for it is on the side, drilled at an angle.

Take a close look.
I'll post a close up of the valve system for you.

-Andrew

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#18)
by Andrew on Thu Jul 03, 2003 at 01:09:12 AM MST

First, its easy for the springs. Just go over to draftpak (a part of cadkey package) and select spring. It will ask how many windings, and the thickness of the wire.

Here are the images of the valve I was talking about.

Sorry if they are big.

Thanks
-Andrew

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#19)
by Brian on Thu Jul 03, 2003 at 11:19:04 AM MST

LOL, I saw your valve on the side of the crankcase. I'm not that blind!! What I didn't see is how the pressurized fuel/air mixture is going to flow from the crankcase to the cylinder!!! There is normally an internal passage from the crankcase to the cylinder that is opened when the piston passes a certain part of the stroke, allowing the fuel/air to flow into the cylinder to be burned on the next intake/combustion stroke.......somewhere near BDC.

How will you accomplish this???

Regarding the solar collector, it's not as bad as one would think. We're working on a new design that will maximize efficiency without tracking regardless of the time of day. The design is meant to concentrate the rays in order to quickly heat water while also generating electricity. It's the first of it's kind design wise, and we hope to have refined the design by next summer for testing. Preliminary data look very promising, but only time will tell.

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#20)
by Brian on Thu Jul 03, 2003 at 11:25:46 AM MST

One more thing...PLEASE use the image tag I posted a few posts ago to keep the pictures smaller than the screen. In case you didn't see it, here it is again.

This will scale the image down to only take up 80% of the width of the screen without changing the aspect ratio. You can change the percentage to whatever you'd like if 80% is too large. Please use it!!

[ Parent ]

plain and simple courtesy (none / 0) (#21)
by Anonymous Hero on Thu Jul 03, 2003 at 11:54:52 AM MST

Yeah i see a lot of attitude from this user.
I have some ideas for andrew but i don't respond to attitude.

Anonymous because i want to be.

[ Parent ]

Re: plain and simple courtesy (none / 0) (#22)
by Andrew on Thu Jul 03, 2003 at 06:07:39 PM MST

Attitude???? What do you mean? I try and be as curtious and friendly as possile. Sorry to offend you. -Andrew

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#23)
by Andrew on Thu Jul 03, 2003 at 06:18:39 PM MST

I was thinking on just using an endmill, and buzz the side a bit at the appropriate length. I just ordered a couple of reamers yesterday, so production should be up and running by next week. (I can't wait to get the new swivel vice for my mill) Also, I'm having trouble figuring this out, how do such tiny engines use rings, and how does one go abuot manufacturing them. I was thinking on using a cobalt or tungsten disc the right size, and very slowly drill out a hole, and then grind a tiny slot on the side to allow compression against the walls of the cylinder. -Andrew

[ Parent ]

Re: Ethanol Engine (updated) (none / 0) (#24)
by Brian on Thu Jul 10, 2003 at 12:50:11 AM MST

Hey Andrew. Been gone for a while. How's the engine coming along??

[ Parent ]

Ethanol Engine (updated) | 24 comments (24 topical)

Menu

� create account
� How to use the board
� FAQs
� search the board
� Google search the board

Login

Make a new account

Username:

Password:

Total Views

��44 Scoop users have viewed this posting.

Related Links

� Also by Andrew

You must be a registered user to post here. It's easy and free, and the link is on the upper right side of your page.
All trademarks and copyrights on this page are owned by their respective companies. Postings are owned by the poster, but may be deleted or moved at the ADMIN's sole discretion. The Rest � 2009 Forcefield.
You can Email the board ADMIN here. PLEASE include the username you signed up with!