the Wasp

My Feedback: (1)

note that this test was performed last summer, and I have just not got around to testing more,, but I really didn't feel I had to do more testing any way, my wants were to achieve more speed from my plane, yet not have a short Power Band as a Cone pipe would produce, you must know that I knew my test would work out to some extant, so here it is,,

so I have this GP ShoeString with an OS 61FX in it, well it's a very fun plane, note that I have never had more fun flying than I have had with is plane,, but it's speed is nothing much with it's older, restricting Slimline Pitts muffler, note I usually burn 20% Nitro in it, well I wanted more speed, see Prop/Mufflers RPM numbers>>
(NOTE, that the stock OS muffler will not fit on this plane)


A) stock OS 61 FX Muffler, Baffle removed,, 15%/ APC 12X6...12,600 RPM,,
B) Slimline Pitts, 20%/ APC 12X6....10.200 "
C) Slimline Pitts, 20%/ APC 11X8....11.800 "

note that I ran the 11X8 98% of the time..


so at the time of the test the engine has 6+ gallons run threw it, and the liner and piston are in good shape, and it has good compression, and I replaced the bearings before the test,

well I made an exhaust adapter and I mounted an old Century 50 Heli muffler on the 61FX (Century's Silent Power #CN3038A), well it ant silent !!,, see mufflers sizes>>

A) OS 61FX Stock Muffler...OD, 40mm, down to 38mm,, 6 inches long,,
B) Century 50 Heli Pipe..... OD, 40mm,, 9&5/16 inches long,,
exhaust adapter) including the Century Flange, Pipe to Engine's Exhaust Flange length is 2&3/8,,
..
running on 15% with the Century Pipe the 61FX turned the APC 12X6 to a peak of "13.800" RPM (OS #8 plug),,

now, I have read that the 61FX will turn 16,000 with a Cone Racing Pipe,,,, but the thing that this is really all about, is, that the transaction from an idle to peak RPM was explosive, instantaneously , NO lag, the power band was from Idle to 13.800 instantaneously,,

I have been around, I have had RC boats with OPS 45s with Cone Pipes burning 55% and they did not perform instantly like this did,

I felt the engine really needed to be slightly loaded more, it's too bad I didn't have a larger prop to try, such as an APC 12x10, 12X13 or 13X8,

with this type of performance it surly would be a good 3D setup, it would strongly pull out of a hover.. see photo,, yes the plane has been beat up on a few times, it needs work..

Hummmm,, I do have a "never started" OS 70sz Heli engine just waiting around, and I do have than new Worlds Model Midget Mustang, mmmmm I don't think the Century pipe will fit it.

Jim

Jesse Open

Sorry I didn't see this yesterday. I would have put an APC 13-8 in the box with your Saito 100! I have about a dozen of them sitting here!

Interesting report.

blw

My Feedback: (3)

Nice looking Century muffler. Lot's of manifold hardware though. Too bad they don't have a side mount version as a stock item. Still a nice looking installation.

1QwkSport2.5r

the Wasp

My Feedback: (1)

thanks for the offer, but the more I think about it the more I think that the 13X8 would be too much, maybe an 13X6 or 7, any hoo, I would be more apt to go with a 12X10 or 11 for the top speed..


I agree on all, the adapter doesn't weigh much but it sure is ugly, I took a 50 size tuned pipe "header" and shorten it's pipe, then cut off the flange on that 61 size Slimline Pitts (you see I vowed to never let that Pitts muffler be used again),, if used in flight I would have had to add an brace to support the muffler.. my welder friend didn't care much about it's looks,

BTW, OS does make a 90 degree exhaust adapter for the 50 and 61 engines, this is so you can use a Heli muffler on your plane engine, but they are for engines that mount vertically on the plane..


back when I was running RC boats (mid 80s to mid 90s), the RC Boat magazine suddenly started to report out of no were that the new thing to do was to use 60 size pipes on your 45 engines and 90 size pipes on your 60s and 67 size engines..
my boats were the "3D" brand, I remember the owner/designer of 3D boats "Tom Daniels" was big into straight-line speed trials, he once told me (on the phone) that he had seen more than one engine step-up on the pipe double-times, and once he saw an engine step-up on the pipe triple-times

thanks for the replies

Jim