GMS .47 Weight
 

I told some people a while back that I'd weigh my GMS .47 and get back with the info. I just managed to weight it today and forgot the thread. Sorry about that.

My GMS .47 weighs 16.06 oz with the stock muffler. I don't really know how that compares to other similar engines, but it seems pretty reasonable.

Wiz

GMS .47 Weight
 

Gee, Wiz, that's about the same as the Tower 46, OS 46FX.
Thunder Tiger Pro 46, Magnum 46XLS etc.

Enjoy,

Jim

GMS 47
 

I own a GMS 47 2000 engine. After over 3 yrs its never been used. The owners manual indicates both the GMS 46 and 47 weigh 475 grams or 15.27 troy ounces. I along with 2 others decided to take a GMS 47 instead of a $75 cash refund in the defunct "Raptor II" deal advertised on RCOnline back in 98 or 99.
I have never heard a question on any RC forum regarding the use of the 2 head gaskets (head shims) that come with this engine. Strange, although the Owners Manual is very good from Gemtec Machinery Systems. The GMS 46 engines 22 mm bore (22.4 for the GMS 47) and 19.6 mm stroke would indicate it is an exact replica of the OS 46SF. The muffler looks like an exact replica of a Performance specialties muffler.

Engine Weight
 

I'll have to disagree with the comment that all of the .46s weigh "about the same."

Actually, Thunder Tiger engines tend to be heavy. OS makes very light 2-strokes. In most planes, and for most fliers, 2 or 3 ounces doesn't mean very much, but on a fun fly plane, you'll get better performance with a lighter engine. The TT .46, from their web site, weighs 15.8 ounces and the OS .46FX, 13.2. That's 2.6 ounces, which can mean a lot in a high performance plane. I own a TT .46 and it is a great engine, it's just not the lightest. I also own an OS .91FX which is lighter than just about any ball bearing .61 and produces tons more power.

When it comes to 4-strokes, the TT .91 is a real heavyweight. It weighs nearly a half pound more than a Saito .91!

Some times, if you are looking for performance, you pay for light weight. If you don't care, you get the cheaper engine, which for many applications, is just as good.

By the way, the reason many people who fly the large acro planes like the ZDZ engines is because they are very light. Great power-to-weight ratio.

GMS .47 Weight
 

Ed,

I'll agree that lighter engines can make a significant difference in overall flight preformance.

I now see that the GMS .47 is a little heavier than my O.S. .46 and TT .46 were, but neither of those engines produced the power of my GMS.

My GMS .47 swings an APC 11x5 at 14900 RPM! I don't remember the exact numbers on those other two engines (I don't own them anymore), but if memory serves it was significantly less......Like in the 1-2 grand range. Can you veryfy that?

BTW, I'm a ZDZ 80 RV owner and yes light weight and good power are some of the attributes I like best about ZDZ, but the low price is the one that won me over. It's (my ZDZ 80) a little less powerful than a BME 102, about the same weight, but half the price. I can live with a little less power for a $600 savings, some people can't.

Wiz

Re: Engine Weight
 

Wow, it always amazes me what people will skim over when reading information. All the values for TT engines are with their mufflers. OS for some reason feels the need to publish the weight of their engines without their mufflers (I'm guessing since most OS flyers fly sans muffler ;) ). The TT Pro-46 is right around 16oz (measured on a fairly accurate postal scale). My OS46FX is 17oz with muffler. I just weighed one last night.

I've heard that the TT 91 FS is a bit portly for an engine of it's size, but then again, it'll turn a bigger prop faster than both the Saito and OS 4 strokes (although not as fast as the YS which is also a bit heavy).