Author Topic: Here's some interesting info on engine sizes (Read 985 times)

Bob Zambelli · « **on:** July 13, 2007, 01:44:14 PM »

I posted this a while back on another site but here it is again – any speculation on rhyme or reason for all the different sizes

??

While looking over a few engines I’ve accumulated over the years, I became curious about how many different sizes were made, so I looked at some websites and magazine advertisements – I was really surprised!

Here are some, starting with a little Diesel: (all in C.I.D.)

.009, .010, .020, .024, .039, .045, .049, .051, .06, .061, .074, .075, .09, .098, .099

.10, .11, .12, .14, .15, .19, .20, .201, .21, .23, .25, .26, .28, .29, .30, .31, .32, .33,

.34, .35, .36, .40, .45, .46, .48, .49, .50, .51, .52, .53, .54, .55, .56, .59, .60, .61, .65, .70, .72 .74, .77, .90, .91, .99, 1.08, 1.20, etc, etc,-----------.

I’m sure there are many more out there but what really got me thinking is: WHY?

? Could there possibly be some rationale? Granted, that for classification/competition, there are definite limits but what about all the “in-betweens”?

A topic for discussion/conjecture?

Bob Z

don Burke · « **Reply #1 on:** July 13, 2007, 04:21:56 PM »

A lot of the really close sizes were made for free flight, .049/.051 for classes 1/2A-A f'rnstance. A couple of other examples are the K&B specials 3.25/3.5cc (class A/B), and 6.5/6.6 cc (C/D). There's also Nelsons with the same close sizes for the same reason.

Most of the sizes were picked to fit one or another competition class.

I think the others were made because, "It seemed like a good idea at the time!"

Jim Oliver · « **Reply #2 on:** July 13, 2007, 07:42:35 PM »

Like some of the rifle and handgun cartridges--a new size just to fill a real, or imagined, need or gap in the line-up.

Build it---some one will buy it.

Jim

phil c · « **Reply #3 on:** July 13, 2007, 08:24:21 PM »

Bob, I think virutally all the "in-betweeners" were originally not contest engines. As sport engines, they didn't need to fit a specific contest category. Then the RC manufacturers started going to inbetween sizes to get more power without building a whole new engine, or to keep the motor fitting a specific set of mounts. Supertiger started this with the famous G21 series. The favorite 46 was a bored and stroked 29 to get the maximum displacement possible to fly sport RC planes. Fortunately they decided to use mild timing to get good idling and running characteristics. Helicopters have brought in a lot of odd sizes recently- 32, 34, 37, 39, 53, 57, etc. They've even crammed a 1.20 into a 60 size case.

L0U CRANE · « **Reply #4 on:** July 21, 2007, 12:11:07 PM »

Another thought on the various sizes, particularly for engines not intended for displacement-rules competition classes...

Check the bore and stroke dimensions. Simple, easily measured/set-up/tooling numbers may show up.

Classic example: Fox .35 0.800 bore, 0.700 stroke. That works out to a 'tween size displacement - 0.352 cu in, which was never a displacement Class-break in the rules, until Combat, and later, Profile Carrier settled on 0.36 cu in...

A 'square' engine (Bore = Stroke) at 0.50 in gives 0.098 cu in; wonder if any of the early .09s had those dimensions....

A 'square' engine at 0.6827 in gives 0.250 cu in, and those are the numbers on the Fox 25 BB Sch! Not easy numbers, in particular, but ...

dennis lipsett · « **Reply #5 on:** July 21, 2007, 02:51:03 PM »

Quote from: phil c on July 13, 2007, 08:24:21 PM

Bob, I think virtually all the "in-betweeners" were originally not contest engines. As sport engines, they didn't need to fit a specific contest category. Then the RC manufacturers started going to inbetween sizes to get more power without building a whole new engine, or to keep the motor fitting a specific set of mounts. Supertiger started this with the famous G21 series. The favorite 46 was a bored and stroked 29 to get the maximum displacement possible to fly sport RC planes. Fortunately they decided to use mild timing to get good idling and running characteristics. Helicopters have brought in a lot of odd sizes recently- 32, 34, 37, 39, 53, 57, etc. They've even crammed a 1.20 into a 60 size case.

Phil, we haven't managed to see a 120 sized production heli yet. The max size in production for Glow is 90 and that is dominated by the YS 90 followed by OS. They do however have gas at 1.4 C.I and of course a turbine or two if you have about 6/8K laying around.
As to the in between sized motors you might also consider that at one time you could get more money for the different sizes. World Engines got about $25 more for a 45 FSR over the 40. Another reason is simply models stop selling after awhile so it makes sense to slightly enlarge the displacement and intro the new, smoother, more powerful;, you really gotta have it Blast 2000 a definite improvement over the Blast 1998.5.
Dennis

Bob Disharoon · « **Reply #6 on:** July 26, 2007, 03:37:21 PM »

Paging "Billy-G"

Author Topic: Here's some interesting info on engine sizes (Read 985 times)

Bob Zambelli

Here's some interesting info on engine sizes

don Burke

Re: Here's some interesting info on engine sizes

Jim Oliver

Re: Here's some interesting info on engine sizes

phil c

Re: Here's some interesting info on engine sizes

L0U CRANE

Re: Here's some interesting info on engine sizes

dennis lipsett

Re: Here's some interesting info on engine sizes

Bob Disharoon

Re: Here's some interesting info on engine sizes