Do anyone know if there is a chart that tells you what motors variance are compatible to what motors. (Example a 46OS is equal to a 61asp 2 stroke)

Thanks,

There is no "chart" per se - there are too many variables such as gear boexes, prop size & pitch, type of plane, etc. There are some manufacturers that list their motors as glo size equivalents (E-Flight among others)

AS A "GENERAL RULE OF THUMB", 100 watts of motor power per 1 lb of ready to fly weight will USUALLY get you in the general ball park for sport flying.
For instance, if your ready to fly weight is 5 1/2 lbs, you would need a motor of 550 (or more) watts of power.

As with anything, there are exceptions - a Cub will typically fly very nicely on about 75 watts per lb (often even less), while a warbird may require substantially more than 100 watts per lb.

G'day Are you trying to compare fuel (glow/gas/nitro) engines to electric motors?

Or are you trying to compare electric to electric or fuel to fuel?

Can you tell us a bit more about what you need to do with this "motor".

glow/gas/nitro comparision I am looking for. Lets say i have a P51 engine and it has a 4 stroke engine. Something happens to it and I have a 46os engine on the shelf. Can that 46 keep that P51 in the air?

G'day again.

An OS 46AX is about the equivalent of a 60 size four stroke. So, if you have a Saito 56 in your Mustang, then an OS AX 46 (or FX) will be about equivalent. It partly depends on the type of plane you have. In gereral, Saito engines are more powerful than OS four strokes. There is a graph of this around somewhere here at the moment.

You did not say what sort of engine you have that is damaged or needs repair and you did not say how big the model is and both facts would help. If you have a 40 size Mustang then the AX will be fine. The LA 46 would be a bit marginal.

More details will get you a better answer.

You can put much bigger engines in planes than they need and they will fly but beyond a certain size, all you get is more noise and more fuel consumption and more weight and none of these is worth having.

If you are looking for a 4 stroke equivalant to a 2 stroke, the conversion seems to be 1.5 - roughly.

Example: you have a 1.20 2 stroke, but want a 4 stroke:

1.20 x 1.5 = 1.80 4 stroke.

or

.60 2 stroke x 1.5 = .90 which would be .91 4 stroke.


If going 4 stroke to 2 stroke, just do the reverse - divide!

Just go onto the Wattflyer web site and look, it's at teh bottom of the header bar. As I recall there was a great how to convert on the site. Been a while but it's a site worth looking at.

I would just look at the motor's full details: it has stuff like maximum voltage/ average voltage.

I have been using a program call Prop Power Calculator to see what a particular engine is capable of . Icalculate the thrust and speed based on what rpm an engine will turn a particular prop (all props are not created equal) Itry to use engines that achieve somewhere around 1 to 1 thrust to weight but most planes will fly just fine with a lot less depending on their wing loading.
Calculating for speed depends on the plane , a trainer flying at 40mph is happy enough but you may not want your P-51 to go that slow. You end up trading thrust for speed in most cases. And vice versa.

I don't know about the conversion, but for the plane in question, it depends on the size. I have the .40 size PTS mustang from Hangar 9, which stock came with a .46ish engine 2 stroke (with 11x7), and I upgraded it to a .80 4 stroke (with 13x7). In both situations the plane flew fine, though is quite a bit faster on the .80 than it was on the .45, but it did fly very well with the .46. For reference, the p-51 PTS that I fly has a 58" wingspan and weighs approximately 7 lbs.