mar345

Was looking at the Magnum add for the new 180 FS in Model Aviation and the manufacturers specs for bore and stroke as listed in the add calculate out to only 1.36 cubic inch displacement !! So is the new engine a 180 or a 136 ??
The add appears in the March issue of Model Aviation on page 14 and the listed bore is 1.417 in. diameter or 36 mm and stroke is listed as 0.866 in. or 22mm. I believe that the calculation for the displacement is the area of the bore times the length of the stroke. So Displacement = Area 0f Bore X Length of Stroke or 3.1416 x radius squared x length of stroke or [3.1416 x ( 0.71 x 0.71)] x 0.866 = (3.1416 x 0.5) x 0.866 = 1.57 x 0.866 = 1.36 cubic inch displacement.
Anyone care to check this out or comment ?

w8ye

My Feedback: (16)

When you set a Magnum 120 FS beside a 180 FS, there is considerable difference in external size.

The 180 has a bore of 35.95 mm and a stroke of 29 mm

Enjoy,

Jim

mar345

I wonder if they made an error in listing the specs in the add ? It would be nice to know the actual bore and stroke before I buy one of these brutes. I wonder how smoothly this engine would run when compared to lets say a Saito 180. The Magnum add implies a low level of vibration.

mar345

w8ye
Thanks! Those numbers work a lot better. Curious as to where you got your numbers?

w8ye

My Feedback: (16)

I looked on the Hobby people site and the numbers were the same as yours.

I then looked at the ASP 180 FS which is the same engine except for the name on the side at www.justengines.unseen.org and found the 29 mm stroke listed in one of the reviews for the ASP 180 FS.

Jim

Richard L.

My Feedback: (24)

According to the instruction manual, the Magnum 180 has a bore of 36mm and a stroke of 29mm:

LuvBipes

My Feedback: (4)

Using an APC 16X8 one test reported 8900rpm on 5% nitro and the other (curiously) only 8400rpm on 10% nitro. Averaging that out, still puts the engine only on par (barely) with a Saito 150. My well used Saito 150, can still turn that same prop at 8900 on 15% nitro.

So it might displace 1.80 cu, but it doesn't turn like a 180.

mar345

My interest in the Magnum 180 is based on the low level of vibration implied in the Magnum add. They refere to it as "Smooth 4 Stroke Horsepower". I don't like when an engine tries to shake the details off of a scale model.
So how smoothly can it run when the 29mm stroke is about the longest travel around in a 180 cubic inch engine?? What factors other than prop balance determine why one engine will vibrate less than another of the same displacement??