049flyer

My Feedback: (18)

It seems we get all caught up in trying to determine which .46 or .60 size engine is the most powerful, or we compare this .25 size engine to that .25 size engine etc.

Unless you are for some reason displacement restricted (competition?), I think power to weight would be much more useful. Instead of which .60 size engine is most powerful, how about which 15 to 17 oz engine is most powerful? Who really cares what the displacement is?

Seems I recall that OS made a .61 size engine and then took the same case and made a larger more powerful engine out of it that actually weighed LESS than the original 61. For a while they manufactured both at the same time. Now there is some useful information. Who would want the heavier less powerful 61?

Recently while flying control line, I read how other modelers ridiculed the Fox .15 because it was a weakling compared to other .15 engines of the day. One club even sponsored a yearly contest to see who could throw a Fox .15 the furthest! The funny thing was that the Fox .15 weighed less than any of the other competing .15 of the day and in fact weighed less than most of the .09 engines of the day. When mounted on .15 size plane it was indeed lackluster, but when mounted on a .09 size plane you had a tiger by the tail!

So why all the focus over the years on displacement instead of weight?

CLBetten

My Feedback: (16)

I'll dive in. Your point is very valid. You are looking from a total logic standpoint. I've found myself in the same situations. I.E. a Clarence Lee modified K&B .61 that has been used on several .40 sized planes. It's compatible to an average modern 60 but much lighter. I'm most familiar with Super Tiger. As the displacement increases in the same case (call it a series) the larger displacement is actually lighter due to the fact there is more hollow space inside. A .51 is lighter than a .40. A .61 is heavier than a .75 then .90. A 2000 is heaviest in order as compared to a 2500, 3000 and 3250. A Saito .65 is much heavier than a lot of their larger engines. What you may not have considered is personal preference and price. Price typically goes up with displacement. Also the airframe. I have old timers that need nose weight. They fly great at half throttle on a .61. There's really no point using a .90 even though the power to weight ratio is much better. Novelty is another target. Under your logic multi cylinder engines in smaller displacements are pointless. But they sure look and sound cool. Just creating conversation. Take care, Cliff

Hobbsy

My Feedback: (102)

I don't put much stock in a few OZ difference such as between the Saito .65 and the .91, moving the battery a couple of inches will compensate for it. The Saito .65 is such a smooth user friendly engine that it wins on that score. I only owned a .91 a few weeks and never really got to know it. I've had an .80 since about 1990.

CLBetten

My Feedback: (16)

Forgot to ad that about the Saito .65. Also should mention a big difference in vibration between a ST .61 and the larger .90. Point being the reasons for choosing a different engine are many and maybe even unpredictable.

Jennifer Curtis

I have NEVER had to add tail weight to a plane.
Most of my glow planes have extra nose weight.
I would not complain about the weight of a stronger
carburetor or quieter muffler.

I don't concern myself one bit about the weight of the
engine. As long as the engine has the right power
for the plane I'm happy.

I'll leave the hair splitting to the speed folks, where
it MIGHT make a difference.

Jenny

aspeed

Power to weight ratio is of the power to the weight of the plane. The motor itself is a small proportion to the overall weight. Speed planes are not all that fussy about weight to a point. Maybe a proto. Flea Fright planes and 3D stuff it matters for sure. I would take a 3 oz heavier Jett .40 over an LA .40 any day. It only has to balance right (and not rip the wings off which is a problem I have had) Having said that, an LA is good for lots of slightly smaller planes. I have a bunch, they have a good power to weight ratio for what they are.

049flyer

My Feedback: (18)

Lots of valid points here. Thanks to all for responding. As a flyer of smaller planes I am always focused on weight, beginning with the first sheet of balsa selected to the final coat of paint and the servo/battery selection.

But you must admit it would be interesting to consider a shoot out among engines of similar weights. The most powerful .46 engine might be a .61.

aspeed

A good example is the Sig Wonder. It is rated to use a .10 to .20 or something like that. They recommend a .19. I put in a couple of different.15s, and they needed at least 2 oz of noseweight, so I ended up with a heavy Fox BB .15 with an extended motor mount. Some guys are using a plain bearing .40 with good results. Something like an LA. I have been thinking about an LA .25 in mine when I get tired of the Fox .15. I have a new head that gives it a bit more power, but it is easier to go up in size. Normally noseweight is needed on many planes, so power to weight is a non issue. Just power. With regards to power. sometimes an unreliable idle in an oversize motor can lead to interesting landing abortions, not to mention sheared wings. Oh I guess I did mention that.

706jim

Lighter weight in a single cylinder engine usually results in increased vibration. So, IMO, the power to weight isn't that big of a deal.

CLBetten

My Feedback: (16)

049, if you're basing your testing on thrust to weight ratio you may likely find your most powerful .46 to be a four stroke also. I could see the Saito .62 right in there at the top or dang close.

jeffie8696

I only use tach readings to determine the engine I select and dont worry much about how much the engine weighs. Most of my planes require some balancing regardless but not much.

Stoneweapon

I found it interesting to compare power to weight (or my impression of thrust during flight) of a 4-stroke at its optimal setup with a 2-stroke using a cheap "silent" muffler and too large prop to match noise restrictions.
2-Strokes are heavier under this conditions.

The other thing is that standard block engines like the OS 61FX or the Super Tigre GS40 are very sturdy compared to the big-bore versions. They have more "meat" to withstand unintended or intended abuses.
I personally like the OS "LA" engines. They are simple and very reliable. The LA46 is as light as a 25FX but swings larger props. A LA65 is not exceptionally light but very simple to set up and reliable. The power of the LA65 is almost the same as the 61FX develops if noise is an issue.

jeffie8696

The 65LA is an excellent engine. I had one on my 60 size Escapade and it proved to be very powerful and reliable. According to a Model Airplane News comparison it is as powerful as most anything else in its size which is very surprising given the reputation of the 46/40 size LAs. I have flown my 46LA and while reliable and fuel efficient doesnt make the kind of power most other engines of similar displacement do

CLBetten

My Feedback: (16)

In the test mentioned the .65LA actually outperformed the .61FX I believe.

049flyer

My Feedback: (18)

I like the OS LA series of engines very much, very simple, good power, and surprisingly light weight.

However, I find I do not like remote needle valves in general and the OS LA version in particular, especially the black plastic, cone shaped piece with the fuel nipple on the carb body. That dang fuel nipple seems way too delicate and breaks easily and for the LA engines I have experience with, the black piece is not replaceable on it's own. One must replace the entire carb body.

Otherwise very solid sport engines in my opinion.

aspeed

I normally put a small hacksaw cut on each side of the LA needle valve. Just to score the plastic so if it breaks, the remaining backplate will still be usable with another brand of remote needle. Sometimes something can be fashioned up to use the remaining needle. They are pretty delicate, and the motors are generally used on trainers, so I guess there is a good profit on the plastic parts. Good motors if you can avoid the ground though.