Hey, ive been reading this forum for a while and am really considering converting a gas engine and throwing it on either a 1/4 sig cub or spacewalker 2. i was wondering what size of engine i would need, and which brand is "the best" or the "OS" of conversion engines. i know this could be a classic "ford vs chevy" matter, but i dont want an engine that will give me headaches and shy away from gas conversion engines. any input would be greatly appreciated.
thx,
andrew

I have a Sig 1/4 scale Cub with a Homey 25. Easy to convert, Their real easy to find and they give good scale preformance on a Sig Cub.

This Cub has flown with a variety of engines including: Zen G23, Zen G26, Very old points ignition Zen23 (KALT22), ECHO 23.6. These 1/4 scale Cubs seem to like any engine that will turn a 16/6 or 16/8 at 8000+ rpm's.

thanx for the advice, would a 30ishcc engine be too much? i would like a little extra power for emergencies and some fun.

I have a converted 30cc homelite on my sons 1/4 Busa DVIII.flies it around at half throttle.running an 18x6 black plastic dynathrust prop.the weight does the plane great justice since its a short cowl WW1 aircraft.If i remember right my 30cc weighs a little less than the homy 25 but i cant remember for sure,thats why i used it i think.82 inch WS.14.5 lbs RTF dry weight.I can hand start it on the second or third flip with stock mag ign.

The Homelite 25 or 30cc engines are good, with the 30cc having a decided edge but they are a little harder to find. If there's an "OS" of conversion engines, I would say it is the Echo/Kioritz engines. Light weight, good power, and usually easy to convert. They aren't as common as the other engines as they are in upscale, more professional type equipment, and as such are also sometimes a little difficult to find. Another thought is the Ryobi 31cc engine. It is popular, easy to find, and easy to convert. It also has the benefit of being narrow because the carb and muffler are mounted on the back of the engine. This works nicely in airplanes with narrow cowls, like Cubs, Spacewalkers, Tiger Moths, etc.

If you think you might like a nice large scale biplane, check out the big Tiger Moth at www.nitroplanes.com. I'm doing one right now with a Ryobi. The Ryobi fits entirely within the cowl, and I think it will fly this plane nicely. It has a 78" wingspan, and is nicely built.

Good luck and have fun,
AV8TOR

av8tor: What do you think of the 82 inch AT6 Texan? Thanks Capt,n

Hey Capt,n. I think I have met you before......Aren't you Steve's nephew? Steve from Rockford? At any rate, I have the Midwest kit version of the 82" ws AT-6 and I am planning on using my 25cc Homie on it. The engine has been converted with a CH ignition, a large boar walbro carb and a Wacker Engines muffler. It runs real good and pulls 11+ lbs with a 16X8 APC so I think it will be a good match for a 12 lb airframe + engine. I just need to get motivated and finish the project!!!!!

I think i might have found a potential candidate........a homelite 30cc blower at home depot for $139. now, what will i have to modify as far as carb setup, scrapping magneto ignition, and to increase compression?
another thing, will the great planes 60 sized cub work for conversion? it seems like it would be an easier kit to build

The answer is “Hell No.”

In my opinion a 60-glow airplane is not a candidate for a 25cc gas engine. You are begging for many problems. Balance problems and structural issues might not have a solution. Assume you have calculated that 30cc is three times the displacement of a 60-glow engine. You probably would not put a 180 glow in a 60 airframe.

Bill

Andrew66,


Based on the specs for the 60-90 sized GP Cub kit you would most likely by OK. With a wing area of over 1100 sq in and a weight of 9.5-12 lbs you should be able to do it with the 30cc Homie. However, you may want to check some of the kit builder forums to see if anyone else has built one and ask how it balanced. If they needed lots of nose weight then the conversion could be a very good choice. If the balance is the other way around and you still want a gasser maybe you should check out an SPE 26 from BCMA Engines. It is very light weight and has everything you need already on the engine. If you go ahead and buy the leafblower for $139 then add an ignition, prop hub, muffler, new carb, velocity stack and mount you will probably spend more and it will most likely be heavier than the SPE 26. The SPE 26 only weighs 35 oz which is only 8 more ozs than a Super Tiger 0.90.


Have fun!!!

thats a good point, if the gp cub isnt going to work, i think some ppl have done the sig clipped wing cub. i have thought about buying a couple ready-made engines, but i want the satisfaction of saying "i did it myself........with the help of the guys on RCU" also, is there any way of using the stock magneto ignition so it will start easier? the guy at my club has the electronic, and on some days he has quite the time starting it. i also will probably do some winter flying, so the more reliable the better.

I prefer using the magneto and pull start when possible.

Bill

so is the pull start actually left on the engine, or is a rope used?

On some engines the pull start is on the opposite end from the prop and can be left on the engine. Using a rope is a really bad idea and very dangerous. Experience is speaking.

Bill

ok, i think on the blower, the pull start is on the back of the engine, is there a special mount i need?

My approach was to tap the existing holes for 10-32 and use screws as standoffs. Here is a picture.

Bill

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The vast majority of gasoline fueled engines that are used in models are conversions. The only problem with conversion engines is usually the weight, or some awkward configuration of carb or exhaust that can be bothersome, when compared to the ideal. Fortunately, most applications for such engines are not critical in this regard.

The largest single problem with all gas engines is also its blessing and major advantage - the carburetor. Most are Walbro manufactured carbs. Those that are not Walbro brand generally follow the Walbro theme. The EPA influenced carbs can be problematic. Fortunately, loosening to bolts/nuts can rid any engine of the EPA carb problem rather inexpensively.

If you are looking for a problem free engine, you are in the wrong aspect of this hobby. All engines can be problematic from time to time. All need maintenance and attention in order to function problem, just like your weed whacker, if you have one.

If you are expecting something that is strictly plug and play, do yourself a favor, stick with the simulator. Otherwise, most engine brands are similarly reliable, with the more expensive brands usually being the best. If you don't like to tinker, stick with a simulator.

well, i dont want to just plug and play, or i would be in electrics. as far as tinkering, i understand that you have to maintain them to keep things working, but i just dont want to deal with having to change or replace things on a regular basis, just to go fly, but i have no problem replacing stuff to get better performance or to improve the flight characteristics of a plane.
on my first plane, i bought a nice little engine that was priced right and was supposed to be "good", but did nothing but give me constant headaches everytime i went flying. i had an average of one deadstick per flight, wich was good practice for me, but not acceptable.
i just want reliability....

I would suggest that conversions might require a reasonable amount of understanding and tinkering during the conversion and testing process. However once I put the engine in an airframe it is seldom if ever touched again.

If however one has difficulty sorting out glow engine problems they are also likely to have some difficulty with gas engines. Gas engines of all types are more likely to be set and forget. In that context gas engines are more reliable than glow engines.

If you don’t like engines don’t attempt conversion. It is considered macho to purchase an ARF engine but not macho to purchase an ARF airplane. Go figure.

Bill

dont get me wrong, i love to play with engines. i do understand gas ones, b/c i was into hot rods b4 airplanes, so what i learned doing that, will transfer over to these conversion engines. as per the glow engine i was having trouble with, even the most experienced guys (they've been flying for 25-30 years) couldnt get this engine to run right. then i bought a webra 40, and i had no trouble tuning it by myself. another main reason i want a gasser, is the ablility for it to hold a setting. my glow engine always seems to be a little bit "off" b/c the high speed needle has a tendency to get bumped or snagged on the cargo net in the trunk of my car. the carb on the gasser i want, will be well out of the way of any obstructions, plus the 1/4 scale cub has a cowl, which will help any mishaps from happening. The guys at my field had similar problems with their planes. there are only a few of us that have nice big trucks or suvs. (thats the next thing on my list)