I missed the other thread, don't know why it seemed to become a boxing match but...

Here's the answer as I see it. There is something you need to understand. There are two distinct types of gas engines available to us to use for R/C: converts and specifically designed.
Converts consist of a variety of widely available small displacement, 2 stroke, commercial engines - Quadra, Ryobi, Zenoah, Homelite, etc etc etc.... These engines were designed with chainsaws and weedwackers in mind and likewise assembled that way. I have a 24cc Homelite weedwacker that is probably 15 years old. I've NEVER taken care of it yet it starts and runs every time. It's heavy and I'd not trust it on a plane but it runs. To make one of these convert plane-worthy, someone needs to buy them wholesale, do whatever is necessary to make them plane-ready, box them up and market them to a VERY small audience compared to that which buys chainsaws and weedwackers, hence the COGS is pretty significant. I have a converted (albeit used) Ryobi 31cc that is probably worth about $125. It is clear that it is a mass produced unit and new wasn't all that expensive. There is nothing stopping you from buying a $150 weedwacker, stripping all the stuff off it and using the engine in a plane. The conversion really isn't that hard. But you need to consider all that happens to those engines and all the hands that they pass thru to get to the nose of your plane. When Weedwackers-R-Us buys engines, they buy truck loads to make their products with and get a volume price. Horizon doesn't amount to a bit percentage of total sales.
The second kind of gas engine we have available to us are the specifically designed. These engines come from both the US and Europe (and Asia of late) and from the brains of engineers who know modeling. They design these engines knowing full well that not only are they designing for a VERY small market in R/C but a very small percentage of that very small market. BME, DA, 3W, ZDZ, Brison, etc these guys don't count sales in the thousands but in the hundreds. And the amount of engineering, R&D, and manufacturing costs that go into making these little jewels put out the way we expect them to needs to be recouped over a relatively small number of products. And when you compare the output of a G45 or a Q42 with a ZDZ40 or DA50, you'll see a VAST WIDE disparity in power output, weight, and durability. Add to that marketing costs and the COGS is VERY significant. You have the option of buying directly from the manufacturer meaning no middle man (or men). And I don't believe that these guys are getting rich off the sales of these engines. But that is where the cost comes from.

Hope that helps.

Nik, thank you very much. That was the answer I was hoping to receive.

-Tom

KMOT , just a quick quirck, some one might have mentioned this but, anyway the worst thing you could do is convert over a weedeater/chainsaw motor, reason: A gas weed motor is designed for shaft drive and or centrifugal clutches, by this I mean the bearings on the crank are for longitude support( up and down pull) when you convert a weed motor to a plane motor and fly, the prop is putting a pulling action on the motor, side to side(pulling straight out) this motion is putting pressure on the crank bearings, the crank does not have the proper thrust washers and/or bearings to handle this load, A Desert Aircraft 50 (for simplicity) has sealed crank bearings that have a longitudle(I.E spelling) support. HHHHHHHHH anyway by converting the motors it will run semi good but will wear out much quicker not to mention using a magneto type ignition, thats why a $80 simple weed motor with a $30conversion and no warranty = $110, and a Desert Aircraft 50 $549 (has electronic ignition, machined case, proper bearings, excellent warranty service, and great looks) + muffler $59 = about $607 dollars. Sorry KMOT if I was long winded but I hope it makes sense.

jongurley: Yes, that makes a lot of sense. Thanks for that perspective. This is what I was digging for. The reasons why their is disparity in price between what I had perceived were the same engines. Now I am more informed about the subject. Thanks!

You did not deserve the response which now ends the earlier thread.
It was totally uncalled for .
strange-- they chose to lock the thread leaving that note in there.

B A L D E R D A S H ...We go through this discussion periodically...
There are very few engines using roller bearings on the crank, US 41 and old Q35s and 40s..
They have a bronze thrust washer to take up the longitudinal thrust, and it works very well and for a very long time..Most of these old engines are still running, outlasting the planes they were put on..
Maybe someone can ENLIGHTEN me as to why DA, for example, using ball bearings on the crank, is better suited for thrust than a CHAINSAW or weedeater engine using the same ball bearings ? The crank in both types is pulled against the front of the case by the prop..THRUST...
The main difference between a CHAINSAW and a DA is in the porting of the cylinder..The DA is designed for more torque at lower rpm, while the CHAINSAW wil run happily all day long at 8000 rpm cutting trees...
Any bearing engineer will tell you that a BALL bearing will take about !/2 of its rated load in thrust...I con't know of any model airplane engines that will put 1500 lbs of thrust on the crank...Cantilever crank engines, like the DA 50, use the REAR bearing to take up the thrust..Engines that are not cantilever crank types use the FRONT bearing for thrust, The rear bearing is there to support the rear portion of the crank.....
BTW, almost ALL the model airplane engines sold in the past 20 years are mostly CHAINSAW or WEEEDEATER derivations...

Uh. . . .RALPH!!!!! (a few slaps, shaking by the shoulders, and a bucket of cold wter thrown onto him. . . )

You're starting to sound like ME, Ralph. . . .better cut that out. . . now get a hold of yourself and have a beer or 6. .

But, point taken, and made very clearly. End-thrust is controlled with ball bearings, or tapered bearings, with high-end loaded shafts actualy using flat "Torrington" style bearings to control thrust (just look inside any automatic transmission) For the most part, the "Thrust" control of a crankshaft is indeed controlled by ball bearings running up against the edge of their races, and they do the job quite well in our engines, no matter WHAT make of engine is used. I have yet to see a "weedie" lose a "thrust bearing", though I've seen almost every make of "designed for the hobby" engine lose a bearing at one time or another.. (Yes, even my beloved BME's. . ) It happens. The "Price issue" comes from manufacturing processes (billet casings versus castings), tighter tolerances, and lower production numbers that always drives prices up, not to mention proprietary designed cylinders specifically for the rpm band and power curve of our model engines (weedies and chainies can hit 8000-9000 rpm all day long and have the powerband to work best. . "up there). There is a tremendous design difference between the two types of gassers . .and the price difference reflects that.

I almost said that at the bottom

Great Mimes wink alike, Ralph

Ran across this:

http://www.wackerengines.com/

And this:

http://www.rcuniverse.com/forum/Engi...umid_92/tt.htm