slapshot1997

When it comes to comparing ball bearing engines to plain bearing engines I won't make the mistake of relying on horsepower specs again. I powered my nice old ACE RC Cloud Dancer 40 with an OS 46 LA to attempt to cut down on nose weight. I used a new OS glow plug and tuned the engine well - but the airplane was an absolute dog with the 46 LA. It had a reasonable enough take off roll and the airplane did fly - but it had just enough power to make compact "trainer plane" type loops - hardly what I expected out of a Cloud Dancer 40. The 46 LA ran well enough and it was reliable, but the airplane definitely needed more. So I decided to swap in an older OS 40 SF (ringed) which has a ball bearing as opposed to the 46 LA's plain bearing. In terms of horsepower the engines should be about even, the 46 LA's stated horsepower is 1.18 hp while the 40 SF (ringed) is 1.22 hp - I should be losing out a little here actually since the 40 SF is heavier than the 46 LA. I tuned the 40 SF and flew the airplane - it was like a light switch was flipped, I now found the airplane was substantially quicker, I had much better vertical climb capability and I could make much larger loops. I didn't change much of anything else other than the engines, I used the exact same spinner / prop (10x6 Master Airscrew nylon) / same batch of fuel / roughly same atmospheric - weather conditions. I'm guessing that the ball bearing engines must also have a torque advantage over the plain bearing engines. I'll be sticking to the ball bearing engines from now on I guess - unless I have something that is nose heavy (and I'll try other fixes rather than trying to use a lighter engine first in that case). I won't knock the 46 LA, it ran as well as it could and it was reliable and easy to start - but I would say the plain bearing engines are probably better suited to slower flying non aerobatic aircraft and trainer planes. Here's some pictures of my Cloud Dancer 40 - I wish I could say I built the airplane - but the truth is I picked up the built airframe used at a swap meet.

jeffie8696

LA engines in particular are very low powered, they only have 2 intake ports compared to most others having 3. In addition you will notice bushing engines have air bleed carbs that while reliable and provide easy tuning and fuel draw they have very small venturis and do not provide much air flow. Bushing engines are inexpensive and reliable, robust and easy to tune but as you have discovered ball bearing twin needle carb engines have the horsepower advantage, especially the SF engines like the one you installed. One of my favorites, I have an OS46SF and it is a beautiful piece of engineering. A real powerhouse.

Mr Cox

It is not really so much about plain bearing versus BB though, as they are simply two very different engines.
Enya engines do very well without ball bearings...

1QwkSport2.5r

I agree with Mr. Cox. Two identical engines side by side will run within a few hundred rpm of one another if the only difference between the two is a bushed crank versus ballraced. Comparing an LA 46 to an SF 40 is an apples and strawberries comparison.

slapshot1997

I was aware of the difference in carburetors (air bleed carb and smaller venturi), but I wasn't aware the LA series engines only have 2 intake ports - that explains a lot. Do any of you guys know if the FP series engines also only have 2 intake ports, I'm am aware that they have air bleed carbs with small venturis as well, but I don't recall them seeming to be so anemic. I actually helped a guy tune his 40 FP on his Stik 40 and it flew that plane fine. I have a couple of FP 40's along with 1 FP 60 laying around. I'm probably going to sell on my loose LA series engines but I'm not so certain that I'd like to dump off my FP series engines.

aspeed

I just checked my FP and there is a boost port. I am pretty sure they put out about the same power as the LA though. In some racing series, ball bearing motors were not allowed, so bronze bushings were available as replacements for the balls in some older Supertigers. There was no measurable difference in power. You may as well keep your LA's. just use them on a lighter plane, because if you sell them off, the $20 won't get you far. I got a few for that price. The smaller LA .15 and .10 are quite good in comparison to other motors of the same sizes, even with the missing boost port. I think the .46 is likely not designed for ultimate speed, more for ease of use and reliability, for which it is good at.

jeffie8696

However for some reason the 65LA is a very powerful engine. I don't know how they managed to get that one right.

earlwb

Plain bearing engines can be really good running engines. But there are some engine models or types that were intended to be low cost entry level engines and easier for newbies to get running OK. The OS FP and LA engines are good examples of this type of engine. In this case high performance was not the issue but good running and easy starting and tuning characteristics.

Now then the older plain bearing engine designs could be harder to get running good and require a good break in before they would run well. Today you don't see these so much anymore as they are all sort of vintage by today's means. But the engines can run good and produce good to excellent power suitable for any model airplane in their size range.

Ball bearing engines came into vogue when certain model engine companies or their importers started big advertising campaigns to sell them. They cost more than plain bearing engines. The ball bearing sport engines only gain about 500 RPMs over a equal plain bearing version. The high performance types of engines do perform with more power and speed though. In the past Enya and Fox both used to sell plain bearing and ball bearing engines that were identical except for the bearings. In this case you could run the two engines and see that they ran about 500 rpms different from each other. But over time the ball bearing engines evolved more with more changes and enhancements and you can't compare them anymore. The plain bearing engines tended to stay the same as a lower cost engine while the ball bearing engines got all the enhancements for added performance.

The main advantage for performance with a ball bearing engine is that it reduced the oil drag on the crankshaft which is where it gets the added RPM boost. Other than that it doesn't offer any other advantage.

The disadvantages are of course ball bearings going bad or wearing out fast, and it costs more for ball bearings too. One could run and use a good plain bearing engine for many years if they didn't crash or hurt the engine somehow. But with a BB engine you had to replace the ball bearings from time to time, sometimes more often than one would like too. Plain bearing engines are great in model airboats too or model sea planes, as a dunking doesn't risk causing bearing corrosion like it does with ball bearings.

Anyway the oil drag become significant as the RPMs increase and begin to stifle the engine performance. There are some tricks that racers did in the past to help reduce oil drag, but since BB engines became so pervasive there isn't much reason to go that route anymore as a plain bearing engine wouldn't be competitive against a BB engine.

Lifer

My Feedback: (1)

The LA series as well as the Thunder Tiger GP series can gain a lot of power with a home-made device called a mousse-can pipe. My GP .42 gained 4,000 rpm on a 10.5x4.5 APC prop. Google "mousse-can pipe" and see what you come up with.

http://www.smrcc.net/Tips/Engine/Mou...n_Muffler.html

aspeed

Here's another source http://www.spadtothebone.net/SPAD/Mufflers/

bigedmustafa

My Feedback: (2)

I've found the .40 LA and the .46 LA to really be the only two "dogs" in the LA-series lineup; I still enjoy flying them when easy tuning and reliability are more important than peak power . The .65 LA has been previously mentioned as a surprisingly lively engine; it can actually out-turn the .61 FX on a couple of prop sizes. I've seen a few .25 LA engines that ran like scalded cats, as well.

The Thunder Tiger GP-42, also previously mentioned, is another good example of a plain bearing engine that likes to run hard. I have a Thunder Tiger GP-65 on a Goldberg Protege .60 trainer that is a pretty tame engine, but my GP-42 engines have all been very peppy and ran happily at 13k or 13,500 rpms on a 10x6 propeller.

Ball bearings are a wonderful thing, but they don't directly contribute to the power output of a glow engine. I've flown anemic engines with twin needle carburetors and dual ball bearings supporting the crank, and I've flown plain bearing engines with air bleed carburetors that were real screamers.

Many of the top glow engine manufacturers like O.S. Max, Thunder Tiger, K&B, and Enya still make plain bearing engines with air bleed carburetors. Ironically enough, it's the budget lines from manufacturers like Magnum, GMS, Aviastar, and SK who only offer glow engines with dual ball bearings and twin-needle carburetors.

049flyer

My Feedback: (18)

Truly astounding how many modelers believe that ball bearing engines are far and away more powerful just because they have ball bearings.

Here's another mystery:

Why the heck do sport modelers judge engines by power output to displacement? I think power to weight comparisons are far more useful but seldom considered. The most powerful .46 might actually be a .61 and the most powerful .61 might be a .75 or a .90.

fiery

My Feedback: (2)

The LA 40 and 46's are sought after by C/L flyers for their running characteristics.

So, it is 'horses for courses'. They are not 'bad' engines. Just an engine designed for a role.

All the LA's also make excellent diesel conversions, due to the restrictive intake, timing and porting.

The best diesel OS never made

jeffie8696

https://www.youtube.com/watch?v=uEB6...SXPIF7UE5LWLDw

Mr Cox

Did the pipe do anything?

jeffie8696

It was a progressive modification so its hard to say how much the pipe itself would have made.
I just installed a new ring in my OS46SF yesterday and after a brief break-in gave it a nice rich run using 15% SIG champion an OS#7 plug and an MA 10X6 Scimitar. gave me 15,100 rpm without even trying. God I love that engine. It is completely stock no mods.

Hobbsy

My Feedback: (102)

This seems to be a bearing discussion, turbo chargers have for years run on films of oil, they turn 90,000 to 150,000 plus rpm and run 100s of thousands of miles with no problems. Most have sleeve bearings where a free floating sleeve has a film of oil inside and outside of it.

jaka

Hi!
If you had choosen a better prop for the OS LA .46 Engine you would have seen better performance!
11x6 is much bettter size and if you had choosen a RAM, APC or Graupner G-sonic you would have seen much better performance,MA is the worst prop on the market!

blw

My Feedback: (3)

Jan, I almost agree with you. I have Zingers down as being a little worse than MA props. It's a close call though.

slapshot1997

You're right about Master Airscrew, I usually use APC props - but this airplane has a tendency to want to nose over on taxiing so I'll be sticking to Master Airscrews on this one (they do have one advantage - they don't break unless you do something REALLY bad to them!). 11x6 is recommended by os for this engine - it might have made a difference, but I've already swapped the engine out.

jeffie8696

Funny, I use Master Airscrew props all the time and my planes fly great. testing is the key.

slapshot1997

Yeah, the Master Airscrews do work - I can usually get a little better performance out of the APC's though - just enough to notice. There's lots of posts on here about how the Master Airscrew props flex the most - but props on real airplanes also flex - so how big of an issue can that really be?

049flyer

My Feedback: (18)

Master airscrew props weigh much less than APC props and are usually a bit cheaper.

Some say that Master Aircrew props flex, maybe so but they also have more blade area at the tip than APC props which end with a point. Seems that you would want some some blade area out at the tips which are moving the fastest. Might as well cut off the last 1/2 inch of the APC since it's not doing anything anyway.

So if you cut the Master Airscrew prop tip like the APC would it still flex as much?

Lifer

My Feedback: (1)

Wow....

earlwb

Well, those APC scimitar shaped sharp front edge props tend to scare me more than the more conventional shape of the Master Airscrew props. I figure I would need a less number of stitches if I have a accident with the MA prop versus the APC prop. Also the APC props tend to have really sharp trailing edges too. The APC props tend to tear up my leather gloves a lot faster when I am hand flipping props. But actually the APC props do work better than the MA props do. But I still tend to use MA props more than APC props though. I would use wood props more, but they are getting harder to get nowadays. What I hate is after getting a engine all mounted in a airplane and all ready to go, is I tend to flip the prop for the heck of it, and when I forget the APC prop gives me a nasty cut.