flyinrog

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or AJ have you made one for one of your projects? (jk)
so engine guru's, what is the smallest production 4-stroke thats made?
just curious. I have seen the v-8 engine that will fit in your hand and the 4 cylinder ones the size of a D battery,,this ? is about rc engines....Rog

ajcoholic

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Mine is put on hold untill I get time to work on it again... its still sitting 1/2 finished in the drawer in my shop

I think the smallest "production" 4 stroke was the OS 20, there are some others but they are special 1-offs or small runs (like George Luhrs masterpieces).

A .10 size 4 stroke would be so cool. I have plans for a 1cc (.061) poppet valve 4 stroke in my engine books, called "Robin", some day I will build one but that may be off a few years yet...

AJC

John C

I had an OS .26 a few years ago on a plans built Basic Trainer. Good flyer, but the engine was no powerhouse, although it had a good idle. I think it subsequently became a .30 displacement. Currently there is a Saito .30, now out in a .40 size, same case size. That's all I know in small 4-strokes []

XJet

I've got an HP 21 four-stroke, it's the design with the Aspin rotary valve in the head.

As far as engines go, it doesn't have many redeeming qualities.

It's not at all powerful, producing (from memory) about .36 hp (about the same as a Norvel 061 AME!) and it weighs a ton.

It also has a pretty poor idle (no matter what plug, prop or fuel I've tried).

However, it is very nicely made and I will get around to putting into a nice parasole-winged sport model some day.

But, another down-side is that it doesn't actually l ike swinging particularly large props and develops maximum power when propped for around 14K-15K RPMs -- not very 4-strokish really :-(

johnvb-RCU

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Ahh, OS20 FS. Mine happily turns a 12*5 Zinger at 5,800 rpm. It's given up fuel as a bad joke

flyinrog

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I think the smallest "production" 4 stroke was the OS 20, there are some others but they are special 1-offs or small runs (like George Luhrs masterpieces).


That guy is a genius, I did a search on his name.. that was the 4 cylinder engine the size of a D battery I was talking about...just amazing.....600 hours to make those motors with jewelry precision....[X(]...the pistons were the size on Lincolns head on the penny....just amazing...
I forgot the other guy that makes the V-8 you can hold in your hand, and you can get it supercharged too!! for a couple of grand.........Rog

William Robison

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Roger:

The V-8s, both normlly aspirated and supercharged, are available from Conley Precision. They are also the current source for Perry pumps and carbs.

Bill.

Raymond LeFlyr

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I ordered my O.S. .20 4-stroke engine from the first ad I saw in the magazine. I, too wanted the smallest one they made. Alas, I believe it also produced the smallest power/displacement of any engine I ever had. The good news is that it is the quietest 4-stroke-cycle engine I own.

I'd bet my .26 Surpass produces twice the power of the .20.

My Saito .30 does even better.

I had an HP .21 for a short time. Had more power than my .20 but weighed a lot more. I traded it back to Mecoa.

I run hot and cold on 4-strokes. The fuel is more expensive because I THINK they run better with higher nitro content. Also, I THINK they don't have as good throttle response as 2-strokes.

nekked_man_2000

I haven't run one of the smaller 4 strokes yet, but, I was interested in the throttle response comment. I run several .50 sizes and don't really notice a lot of throttle lag, and I run 10%Nitro in all of my engines, from my .020TD to my .91 4stroke...so don't notice the need for higher nitro. But, they don't make as much power as an equivilant size 2 stroke, maybe that's why you need the extra Nitro. I did notice a lot of difference when I experimented with 10, 15, and 20% in my Saito .50 More than I noticed in my 2 strokes. Back to throttle response, the thing I like the most about the 4 Strokes is that the throttle seems to be more linear. I think of 2 strokes as having 3 speeds, idle, high speed, and something less than high speed. My 4 strokes seem to respond to one click on the throttle lever, which is nice for the 3d stuff. I like a high pitch prop on a 4 stroke on a sleek plane. It's really cool to see a plane flying 90mph and sound like the engine is hardly working, reminds me of an old Harley as he puts by you on the freeway at 70mph...ahhhhh the music of a 4 stroke.

Man, I'd love to have a .10 or .15 4 stroke.

Raymond LeFlyr

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I pondered the wisdom of expressing my opinion about "general" throttle response differences. I lost my argument with myself.

My Saito .72 has real good throttle response. upright, upside down, cold or hot - period. It has spent some time if the front of a couple of (short-lived) profile fun fly models and an Ultra Stick. It did very well on the fun fly's with the CL 12.25x3.75 props.

My little 4-strokes, in general, are slower to wind up when I crack the throttle from idle to wide open. Not as good as my combat 2-strokes. Perhaps its because they spin larger props.

My biggest 4-stroke-cycle engine is a Saito .91. It does good but not as well as the .72. My .60-size O.S. 2-strokes seem to me to respond better in the same model. Again, they carried different props. I tend to run more pitch in the 4-strokes.

I use S+W 20-25% nitro with 20% oil, half castor in them. It is hands down, the best fuel I have ever used for 4-strokes (opinion, not based on scientific proof). In the summer I may reduce nitro to save a dollar or two per gallon. But most of the time I stick with the "good stuff". If I was a fighting man, I would offer to arm-wrestle anyone with an opposing opinion. Oh why did I write that?! I hope I delete it before I hit Transmit.

The preceding comments are not paid for by anybody's political action committee, fuel manufacturer, or football half-time "performer". Alas, I confess that my observations are probably just delusions caused by my advanced age and should not be in any way construed as "words of wisdom". I may have missed my medication today.

nekked_man_2000

Yeah, I suspect we agree in principal. I didn't mean to start an argument, sorry if it sounded like I did. I'd probably run 20 or 25% myself, but I still run some hundred year old(not really) engines with iron pistons and sleaves, I suspect they'd eat themselves alive if I tried to get any power/rpms out of them(my McCoy .40 and .35 come to mind), and I'm too lazy to keep up with more than one brew, I just sorta found one that agreed with me and stuck to it. I had my Saito .50 in a smallish P-51, and ran a couple of gallons of 20% through it...it was a thing of beauty, the fours definitely seem to respond to the Nitro! And no amount of tuning makes a 4stroke have that immidiate rapp you get from a hot 2stroke. I love 'em all myself!

Big Al-RCU

Several OS 20 4C have been on ebay lately. Used have been going for around $100 and a NIB went for $169.
Save your Confederate money!!!

flyinrog

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BA HAHAHAHAHAHAA! that was a good one Big Al.....confederate money

Flicker

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Kalt (Japanese heli, etc. mfg) announced an .09 4 stroke several years ago...never saw one though.
That would have been neat.
Bob

zoomzoooie

Well... how are these for small? Check out the pics! They are hand made by a master craftsmans. If I remember right, the inline 4 is .061, or so. I know the 5 cylinder radial is .061. I don't recall the size of the single but must be very small. They all work too! I came across these while on a search. I don't know the site, but if you search for Luhrs you might find them. I know I would love nothing but to have that inline and radial for any of my planes. Specially a Gypsy Moth or any antique scale model. Don't think I could afford them if they were for sale though.

ZZ

ajcoholic

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those are George Luhrs' engines...

zoomzoooie

Thanks ajcoholic, I couldn't remember his first name.