Hello!

I've become fascinated with converting from a gas engine to a gas/glow engine and accordingly purchased an old Homelite 25cc engine from ebay. I also bought a glow plug adapter for this purpose.

Now, Iam looking for a way to get the recommended mixture of gas and glow fuel. From scouring the forums Isee that the recommended mix is 1/3 of 10 / 10 Glow fuel and 2/3 of 93 octane gas. Iam stuck because Ido not know where Ican buy 10 / 10 glow fuel. Ican easily get 15% nitro + 18% synthetic lubricant fuel or 10% nitro + 18% synthetic lubricant fuel at my local hobby store or even 20% nitro 20% synthetic oil fuel (YS fuel?)if Iorder it on line (less practical). So my questions are :

1. What is the best mixing option to use among the above choices at my disposal?

2, Is there a place Ican get 10/10 fuel (I'd like to start with a quart to test things out). Ifind nobody sells the stuff any more.

3. Any other practical options (maybe heli fuel - which Iknow nothing about)as a starting point ?

Thanks

Ranga

Try to locate methanol. Try automotive speed shops, race car building shops, race tracks, and go kart suppliers. Chemical supply houses as well. You can then use 1 gallon of methanol mixed with 1 gallon of 20% nitro, 20% oil glow fuel to get the Gas/Glow 10/10 fuel.

Av8tor

Thank you Av8tor for quick reply! I'll go that route.

The following questions are not connected to the previous one but I would be grateful for a reply:

I wonder if these conversion engines are particularly hard to tune. How reliable are they?Will they dead stick easily? (i.e. more easily than a nitro engine?) Are they less reliable than gas? I've got no experience with gas engines either so Iam wondering if Ibit off more than I can chew here.

Is a homelite 25 a decent choice for a 120 size airplane ( I'm going to fit this on a CMP 72 inch zero which seems to do well on a 26 size gas engine).

Ranga

They are as reliable as regular ignition gas engines in my experiences. They seem to start easier and idle slower than a regular gas engine. Be sure to follow all the guidelines in the "Gas/Glow how to" thread.

The Homelite 25cc might be a touch heavy for your plane. You might get away with mounting servos in the rear, but in truth, gassers should be used on airplanes with about 1000 square inches of wing or more. Fighter planes have high wing loadings to begin with, and if you make yours even heavier with a Homelite, you might not like the plane much....

As a side note, the Homelite 30cc weighs the same as a 25cc and looks identical, but has considerably more power. They were often used in leaf blowers, and have been found in later model Ryobi weedeaters as well.

AV8TOR

Ifind my LHScarries 20/18 fuel. Can I use that instead of 20/20 and mix with a quart of heet (yellow)for methanol to get to the starting point (approximately)?Will the slightly less lubricating oil mess up the homelite? If so, I'll add some lubricating oil. What lubricating oil can I add to make up the difference? Can Iadd 20cc of Castor Oil to that 20/18 to make up the difference given that Ican obtail it at my local pharmacy? (will castor oil mix with gas or will it gum up the carb?)

Iwould like to buy a quart of the stuff to get started.

Thank you in advance for your answer.

Ranga

It should work fine. In the original mix, the oil comes out at around 32:1. A touch less won't hurt.

Good luck and have fun,
AV8TOR

Gas/Glow seems interesting, what would you say to this blend: 1 Qt. 20/20 glow, 1.15 Qt E-85, and 0.85 Qt gasoline? Did I get the ratio correct? E-85 is available at one location in my area.

When we started the Gas/Glow experiments, I tried E-85. Didn't work well at all for me. Some others have tried it with varying levels of success, using on board glow power, etc.

It is the methanol that has a catalytic reaction with the platinum in the glow plug element. E-85 is 85% ethanol. Not the same deal....

AV8TOR

Iam simply unable to make the engine idle reliably at anything below about 2500 to 3000 RPM. That is high. Will using an on-board glow help ? It appeared to idle better when I did not remove the igniter after startup. Presumably putting the flywheel back on will help the situation but it would add weight (sigh!).

Iam using a 18x8 Prop.

I am able to get a consistent high end RPMof 7500which is quite nice. for a 25cc engine.

Any other tips on getting a lower idle?

Ranga

You might try putting the magneto ignition back on it, and see how it idles then just in case you have some unrelated problem. All of mine will idle so low you can almost count the prop blades going by. They often won't shut off even with the carb all the way closed, and will just sit there putt putt putting away.... When trying to shut them down with the carb all the way shut, I have often had them backfire and take off idling in the opposite direction!!


AV8TOR

I found the problem (Ibelieve). Air leak at the heat dam. Ihad a loose screw on one side where the heat dam meets the engine block.

Sometimes, it pays to check for the most obvious issues (sigh!)

Thanks for your help. I'll try again today and report back.

Instead of just tightening it up, which would be the normal tendency, you might want to take it off, check the gasket, and sand the insulator block on a nice flat surface to make sure it is still straight. (And/or make it straight if it is warped.)

Note that fixing this leak is going to change your mixture tune again....

AV8T0R

After fixing the air leak, I find I am able to get a steady low speed idle of 2000 RPM without the glow igniter. However, I notice that the engine hunts (speeds up slightly and slows down) when it idles. If I allow it to idle for a long time, and suddenly throttle up to high, the engine hesitates.   The hunting behaviour and hesitation goes away when I leave the glow igniter on during idle and I also find the transition from low to high is smoother. Further, I am able to go down to a comfortable 1800 RPM on idle.

I think I'll need to use an on board glow for reliability.

Other than that, I am able to go up to a steady 7300 to 7400 RPM on an 18x8 prop. I am told that is pretty good for an engine this size and that it matches the performance of commercial 26  cc gas engines.

I think I'll stop tweaking. What size plane ( wingspan, wing loading  and weight)  can such an engine pull comfortably? I am thinking about an ultra SPAD stick build for it.

7300 rpms with an 18 x 8 is approximately 18 lbs. of thrust according to PE Reivers prop chart, and probably around 65 mph or more level airspeed.

My usual recommendation for any gas engine plane is nothing less than 1000 square inch wing; for sure not less than 900 squares if you are experienced and it is an aerobatic plane with a farily light gas engine. For a Homelite I would stay at 1000 squares or above due to its weight.

AV8TOR

After removal of the flywheel and ignition coil, the homelite gasglow weighs in at under 3lbs. This includes the muffler. Compared with commercially available 26cc gas engines, it seems pretty competitive.

The zero has a wingspan of 70.5 inches and an area of 877 square inches (57 dm squared). It is slightly smaller in area than your recommendation. It supposedly requires a lot of nose weight so I might be able to put the flywheel back (might as well use that weight quota). I am thinking that might be a decent candidate. Apparently comes in quite heavy at 18 - 20 lbs but reputed to be a "floater with trainer like flight manners".

I am tempted to build a coroplast  giant spad stick.  Nothing quite as impressive as a plane which looks like it was entirely dug up from the junk pile but yet flies well. That one has an 80 inch wing span and apparently comes in at 20 lbs. I might scale it down by 10 inches in wingspan.<br type="_moz"/>

Actually that could be an over estimate on the weight of the zero. Apparently can be made to weigh about 15 lbs with judicious weight placement.

Well, I have a Giant Stik that is a pleasure to fly even though it is heavy, because of it's high wing area. I have a Katana that's a pleasure to fly because it has low wing area, but it is light.

Then I have a Giles that must be flown very carefully because if you get it too slow or pull too hard on the elevator, it will snap on you. It has a Homelite on it, and about 900 squares. Warbirds are famous for high wing loadings and the tendecy to snap roll. That's why it concerns me to put a gas engine on a Zero with only 877 square inches of wing area. Your choice, but it is always a bummer to build something that isn't enjoyable to fly... (Or to lose it in a crash due to a snap roll in a turn or final approach to landing.)

AV8TOR

I did some research and found others seem to have no trouble putting a gas engine on this plane. However, it appears 25cc is on the low end of acceptable power level.

I did some reading and decided to upgrade the homie to 30 cc. I bought a new cylinder and piston. Hopefully it will run at 8K RPM. A little extra power does not hurt.

I am not keeping track of how much this is all costing - it is the learning experience and kick I get out of it that pays back for the obvious cost overrun :-)

I would have come out pretty close to even by buying a gas engine new but hey who's counting....

Thanks for all your help.

Regards,

Ranga<br type="_moz"/>

I do tons of projects. I am a hot rodder, have a very fast boat, I've had several ultralight airplanes, I'm an avid modeler and engine guy, etc., etc., and the one golden rule is never, ever, ever keep track of what it costs!! If you did, you would lessen the enjoyment and possibly even not do it anymore. Besides, if you are married and the wife finds your accounting, that would cost you even more for the divorce!

AV8TOR