Thank you, I TOBOR.

This is a new engine (never run) so we want to start out right.

Originally Posted by SrTelemaster

Nor would I ever own one.

To try to represent an uneven firing single throw opposed twin being as smooth as an even firing more naturally balanced boxer twin is just plain ludicrous.

Yup, just plain ludicrous. Funny how even Clarence Lee says they don't "shake" any more than the "boxer" type.

I have been running the 80T and 90T since they first came out and I oun All of the OS twins and the Saitos don't shake any more than them.

I own 3 80T's now and one 90T and run them quite a bit, no "shaking".

Like Gary Cee and I Tobor said. You never ran one so you wouldn't know anyway.

Just out of curiousity, what is the largest single-pin 4-stroke horizontal twin (including motorcycles, lawn equipment, etc) that has been produced in significant numbers?

I can see where very small displacement single-pin 4 strokes might not be "shakers", but if there is no inherent advantage to the "boxer twin, why is it even produced in the 1st place?

The single-pin is so much cheaper to produce & on very small engines it would also have a definate weight advantage. So, given those attributes, why doesn't the single-pin design dominate the entire flat twin market?

Why would manufacturers even go to all the added expense of a double throw crank design if there where not significant advantages?

D'guy and Itobor are spot on . The Saito 90 is a real smooth running engine . I love it !

Nobody said the boxer twin is useless . The rocking couple induced beemer buzz is definitely bothersome for people . Indeed BMW found the need to finally take steps to minimize the buzz. I agree with them .
Why would they go to all the expense of a right angle driven balance shaft if the engine was already perfectly balanced ?

The Royal Enfield vertical twin was probably the smoothest of the big bore Brit vertical twins .(Rubber mounted Nortons aside ) In fact I have had BMW air head riders comment that my Royal Enfield Interceptors actually seemed smoother than their BMW . I know they wouldn't be able to say that about a BSA Lightning or Triumph Bonneville . The Interceptors were dynamically balanced at the factory . They also sported a 26 pound nodular iron crankshaft, deeply spigoted , well supported cylinders and a well designed frame that helped minimize the natural nature of the vertical twin layout . Not all engines and packages of a given configuration are created equally .

Originally Posted by Gary Cee

Nobody said the boxer twin is useless . The rocking couple induced beemer buzz is definitely bothersome for people . Indeed BMW found the need to finally take steps to minimize the buzz. I agree with them .
Why would they go to all the expense of a right angle driven balance shaft if the engine was already perfectly balanced ?

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But that still doesn't answer my question.

Why didn't BMW just utilize the much cheaper to produce single crank pin flat twin instead of going to the considerable added expense of double crank throws W/the additional main bearings, etc?

Why would I have to second guess them ? No one said that the boxer layout was void of "advantages" . So why do you imply that ? The subject had been rocking couple . There was an assertion that rocking couple was a "wives tale " with the inferrence that those who spoke of such were a bit ignorant . Of course that would have to include the BMW design engineers as they too saw the need to attack the "wive's tale ". Balance shafts are not cheap ! Perhaps the "wives tale" assertion was in fact quite ignorant after all .
Our primary interest here is RC model aircraft . Within the range of RC engines the differences are nil to at times giving an edge to the sigle pin . I don't have my boxer Saito any longer but it sure seems the single throw 90 puts out a lot more power as well as being smoother . Datsunguy can probably fill in on the power differences .

Single pin crank should allow for a more compact engine which in turn is less weight. Not a lot but it's there right.

Ray

I can't really compare a Saito 80T to an OS twin because OS smallest is a 120. However, I had an 80T on an old Dave Platt Waco YMF3 and it flew quite well. That was a big biplane designed for a 60 two cycle. The 90T has more zip than the 80T that's for sure.

Both are one flip starters, great on fuel consumption and have a neat sounding idle. Hard to describe if you never heard it. Sort of a putt putt, ..., putt putt. Remember if fires like this, Bang bang, exhaust exhaust..

They are light engines. OS has all steel cylinders and Saito used ABC early and AAC later. Also one piece head and cylinder.

Dan, the original reason Saito gave for the boxer was to have a, "sort of" Continental Engine look for model Cubs and it caught on for many others as well.

The BMW boxer had only two main bearings, no center bearing.

Originally Posted by I TOBOR

.

The BMW boxer had only two main bearings, no center bearing.

And some of this :





Along with some comments on the BMW boxer and it's well known rocking couple issues . :
http://hildstrom.com/projects/boxer/index.html

Hey guys, trying to get my 72 I got from the classifieds running correctly. I used MikeMcChickens method to tune it, but having issues still. When I get it on the top, it hunts for rpm. I've had it both on the rich and lean side (top), and no where does it ever peak and hold. It won't idle below 3k very well, and the LS is set rich enough (another 1/8 turn closed and it dies). I set the valves a few months ago...did it according to guide found here.... The engine is used, and I haven't opened it up to really look on the inside.... thanks!
*running a XOAR 14x4 and 30% magnum.

Originally Posted by SrTelemaster

But that still doesn't answer my question.

Why didn't BMW just utilize the much cheaper to produce single crank pin flat twin instead of going to the considerable added expense of double crank throws W/the additional main bearings, etc?

Actually Harley Davidson had all the patents and copyrights on the single crankpin design flat and V twin engines using a forked rod or side by side rod setup. When the patents ran out HD got copyrights on the sound, et cetera for the engines too. BMW had to do something different then.

The HD WF from 1919-1923 a flat twin design with a single crankpin.

The opposed twin was by no means originated by either BMW or HD . Douglas and ABC had them in production long before BMW made their first and surely before HD's blacksmiths got the idea .
BTW A patent only holds sway in the country of issue . The idea of copyrighting the Harley Davidson noise is a real gem .
Forked rods were not exclusive to Hardlies .

Where did the Saitos go? I found one, can't wait to fly this in a week or so, got cleared by the Dr. yesterday, no restrictions on the arm.

I have been looking for one of the inline, narrow v twin Saitos for a while now . The smaller one is the one I am looking for . The newest plane here is running a NOS YS 63 .
Plan to build a big Fly Baby this winter . Looking for a 3.00 opposed twin for that one . Probably have to sell off some stuff . Serves two purposes ; Generates cash and makes room for more planes !

Earl , Indian beat Harley to the V twin cycle by about three years if I recall correctly . (As well as the 1902 French Griffon , The 1902 NSU and a few others )