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Old 01-24-2006, 12:14 AM
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Re: BME 55....its coming

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Originally Posted by STR8HUCKIN
they obviously have very little metal in them??? How can they have a tough enough piston and a balanced crankshaft at that weight??? Are DA and 3W retardted or is that bme gonna vibrate and not last very long ?? why do they run hotter??? Are there less cooling areas is that how they keep the weight down??? I would love to hear from the bme designer.... He must have some pretty radical ideas and theory about engines to have made such a kick ass motor?? a pound and a half difference on a 5 pound motor is like a 35% diff. someone has to be doing something wrong
Yes, reduced cooling fin area and very careful trimming of the crankcase is whrer he saves the weight, I doubt that he compromises in piston/cranckcase balancing to achieve his goals.
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Old 01-24-2006, 12:35 AM
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Re: BME 55....its coming

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Originally Posted by bodywerks
Yes, reduced cooling fin area and very careful trimming of the crankcase is whrer he saves the weight, I doubt that he compromises in piston/cranckcase balancing to achieve his goals.
Reducing fin area does not always mean reducing cooling efficiency. I am no engineer, but there is more than one way to skin a cat.

As for the stand-offs,,,he could remove the radial mount and incorporate legs or a back plate like on the 55.

Keith had mentioned that you could wind up the 110 pretty tight with out any problems.
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Old 01-24-2006, 01:02 AM
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Re: BME 55....its coming

Yeah, I believe Keith's idea was that the extra weight in excessive fin area for super cooling efficiency could be cut by requiring baffling in the cowl to force air over the smaller fins, thus providing effective cooling. The extra weight in balsa baffling surely is lighter than extra metal fin area.
However, I think his biggest weight savings, at least on the 110, is the HIGHLY shaved down casing and overall shorter engine length (even less weight in aluminum and steel), as well as the single-bolt hub (not to mention the trimmed down prop hub) setup.
What do you mean by "wind up the 110 pretty tight without any problems"?
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Old 01-24-2006, 01:15 AM
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Re: BME 55....its coming

They have been run at higher than normal rpm with no ill affects.

You a right about the biggest weight savings. It is amazing when you hold it side by side with other engines in the same CC class.
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Old 01-24-2006, 06:58 PM
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Re: BME 55....its coming

The first prototype BME55, during testing some 2 years ago, spun a Bolly 19-8 in excess of 10.200 rpm for a LONG time. . they actualy tried to make theengine spit out a rod, and didnot succeed.

In a rather perverse test of the 110, when I was developing a canister setup for the engine, I put a 26-10 Mejzlik on it, using the same setup for exhaust that turned a 28-10 Mejzlik at 7100 rpm, and a Menz 27-10 in excess of 7300 rpm. The engine tached OVER 8100 rpm, and had insane idle-full power response with the small 26-10 Mejzlik prop on it. The sound was mind-boggling, with the prop actually going sonic and ripping on the test stand. Needless to say, after a few minutes of that insanity I determined to never use a 26-10 anything on the BME110 ever again.

The internals are very robust in design. Keith claims that no BME crankshaft has ever broken, though you can destroy the bearings if you abuse the engine.
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Old 01-24-2006, 08:27 PM
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Re: BME 55....its coming

Man, you're all about doing exactly the opposite of what BME recommends! More power to you...you seem confident enough in your knowledge. As for me, BME says use a BME 26X10 for break-in, and that is what I intend to use. I already know it rips the prop, even on stock mufflers, I've seen it, but I only have to deal with it for a few gallons, of which full throttle should rarely be used, anyway. My final prop selection will likely be a 27X10mezjlik, menz, or MSC, depending on what kinda R's I get at my altitude.
I will admit, however, that, the instructions seem to be written around stock mufflers. If you ar running cannisters, it would be a different story.
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Old 01-25-2006, 07:04 AM
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Re: BME 55....its coming

Bodywerks. . There is a big difference between myself and BME .. BME has to worry about a WARRANTY, and keeping a lot of people happy. I, however, have a deserved reputation for pushing equipment to it's limit, and trying to get every ounce of performance out of a product. Since I've never hurt a BME110. . I guess there is still room for improvement.

So far, Keith has not told me to knock it off and not push the little engine as hard as I can. So . .now. . it's time to develop some IMAC planes strictly around this powerplant. . since no one seems to have stepped up to that yet.

And the 55??? (which this thread is about, btw). . oh MAN I've got a plane designed just for that engine . .. it's gonna be insane.
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Old 01-25-2006, 07:10 AM
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Re: BME 55....its coming

I would imagine that most yaks and other 84-87" planes would be difficult to balance without the weight up front.

I'm thinking GP Cap 232 with bme55 at 12.5-13lb with lipo batteries or GP yak 54 at about same weight? What do you think?
Any other prime candidates?

When would be the earliest one can get one? production or preproduction?
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Old 01-25-2006, 07:17 AM
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Re: BME 55....its coming

Quote:
Originally Posted by STR8HUCKIN
they obviously have very little metal in them??? How can they have a tough enough piston and a balanced crankshaft at that weight??? Are DA and 3W retardted or is that bme gonna vibrate and not last very long ?? why do they run hotter??? Are there less cooling areas is that how they keep the weight down??? I would love to hear from the bme designer.... He must have some pretty radical ideas and theory about engines to have made such a kick ass motor?? a pound and a half difference on a 5 pound motor is like a 35% diff. someone has to be doing something wrong
Keiths philosophy is very simple. . Lighter is better. DA and 3W and ZDZ all have different design/engineering philosphies. But, when DA and now BME came out with super competitive engines to go up against 3W's products, you saw a very quick shift in the 3W design ideology and business practices. It's a slow process of evolution for the engines we use today. If you will notice, 3W's engines have gotten lighter, DA is working toward that end as well, and BME has not really moved toward a 150-200cc sized engine. As for being retarded . .ZDZ engines, for the displacement, are close to the BME's in weight, usually within 10-15%, unlike the other guys being off by 30+%. But, again, it's a different design philosophy from ZDZ.
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Old 01-25-2006, 07:29 AM
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Re: BME 55....its coming

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Originally Posted by red_z06
I would imagine that most yaks and other 84-87" planes would be difficult to balance without the weight up front.

I'm thinking GP Cap 232 with bme55 at 12.5-13lb with lipo batteries or GP yak 54 at about same weight? What do you think?
Any other prime candidates?

When would be the earliest one can get one? production or preproduction?
Balance with the BME is a matter of shifting other components forward in the airframe, usually. I've had 3 3M Composite-ARf Extra's with the 110 on the nose. . none required lead or ballast up front. But, aft of the wing tube there was NOTHING, and only one servo per stabilizer half. Other people have done the same thing with the same combination of engine/airframe.

For YAK's and other radial cowled aircraft, you can shift the engine and exhaust forward a bit to get the weight as far forward as possible. The engine/exhaust is the single heaviest piece of equipment on the plane, so moving it has the greatest effect on CG changes.

One thing people forget. . even if you add a little ballast to attain a proper CG, the power difference between the BME55, and ANY other 50-55cc engine, gives you a very strong performance increase. For the same exact flying weight, you will have better acceleration and performance, which makes the BME55 the best alternative when compared to any other engine out there. If you can achieve a proper CG without adding ballast, then even better. But no one should develop the mindset that adding ballast is a bad thing. You are already saving 12-16 ounces, at LEAST, over any other powerplant out there, and you are not just paying for a the weight reduction, you are also paying for the performance increase.

I look at it this way. . you are gaining a lot of power, and NOT increasing the weight. .that, in and of itself, is more than enough reason to buy the engine. That you also decrease the engines weight is an overall additional PLUS . .if you can take advantage of it . .even better.
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Old 01-25-2006, 07:34 AM
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Re: BME 55....its coming

I think an Edge or Extra 300 (shoulder-wing design) would be ideal - they both have a bit longer nose than most. Actually, the GP Ultimate wouldn't be a bad airframe, either, but probably not for IMAC.
Kris, I am sure you know what you are doing, so it's all good. BTW, have you had any problems with CF props slipping on this single-bolt hub setup? Do you use a torque wrench when tightening the nut or do you just crank down on it until you can't get any more out of it?
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Old 01-25-2006, 07:56 AM
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Re: BME 55....its coming

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Originally Posted by bodywerks
I think an Edge or Extra 300 (shoulder-wing design) would be ideal - they both have a bit longer nose than most. Actually, the GP Ultimate wouldn't be a bad airframe, either, but probably not for IMAC.
Kris, I am sure you know what you are doing, so it's all good. BTW, have you had any problems with CF props slipping on this single-bolt hub setup? Do you use a torque wrench when tightening the nut or do you just crank down on it until you can't get any more out of it?
I cheat. I drill the spinner backplate for the 3W large pattern, countersink the holes then use #10 x 1" countersunk screws through the backplate into the propellor. The entire "assmblly" is then balanced as a unit. The backplate has two holes to match the location of the anti-rotation pins in the prop hub of the BME 110. Three "anti rotation" screws are all that are required, and if you index several propellors to the same backplate you can swap props without rebalancing things.

As for tightening the center nut/stud, I use a long 13mm 6-point Craftsman wrench, grab the prop in one hand, and just YANK. Being a professional mechanic. . my "Calibrated hands" know when enough is enough. You would be hard pressed to break the center stud, though. I've tried to break it. . without success.
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Old 01-25-2006, 08:18 AM
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Re: BME 55....its coming

I am an aircraft mechanic and have a "calibrated elbow", too, but actual numbers would be of some value. What do you think, around 40-45 lb.ft.?
Well, I cheated, too, but what I did was put a couple #10 alloy screws into the spinner backplate, bottomed out to the head, to act as anti-rotation pins in much the same way as the prop hub does. I figured it can't hurt...
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Old 01-25-2006, 08:34 AM
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Re: BME 55....its coming

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Originally Posted by bodywerks
I am an aircraft mechanic and have a "calibrated elbow", too, but actual numbers would be of some value. What do you think, around 40-45 lb.ft.?
Well, I cheated, too, but what I did was put a couple #10 alloy screws into the spinner backplate, bottomed out to the head, to act as anti-rotation pins in much the same way as the prop hub does. I figured it can't hurt...
Being that the stud is 8mm x 1.25 thread. . the rated torque is in the 25-30 ft lbs range. 40-55 ft lbs would be something in the 3/8-10mm range, and 60-80 for 7/16-12mm. . depending on metallurgy and thread count.
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Old 01-25-2006, 02:15 PM
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Re: BME 55....its coming

That's right, I thought it was 10mm...
that stud does appear to be a high carbon alloy, so it should definitely be able to handle 30 or so.
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