freakingfast

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Several weeks ago I arrived at the field and noticed a plane realy moving and thought I want to get a better look at it later.
Well, it turned out to be a stock World Models T-34 with a OS 55 in it. NO Way, but it can't be... but it was. So much for my thinking the 55 is a low RPM motor.
I've worn out a few of these planes too with OS 46 & 50s and the gamut of Ultrathust or Mac's tuned pipes but, I was never able to get one to move that good.
The speed looked like 120+ or so.
He was running a red Jett muffler with what looked like an OS exhaust spacer so the muffler would clear the side of the fuse.
The engine is turning a 10x8 APC at 15,000+(edited 8/19,was16k,sorry) on the ground (that's about 2hp !) and realy unloads in well in the air. The fuel was Power Master 15/18.
The T-34 has a lot more run time on it now and it's still fast however it has new covering...he blew the original off.
I keep joking "What's under that OS 55 camouflage."
His RCU name.... T-34 .. it figures!

Razor-RCU

My Feedback: (50)

Cool! Just goes to show that because it does not turn 18K it can still be fast if propped to run in the proper power-band. I really want to try a Webra-55 like Rmenke is always talking about but i have more engines than airplanes already

10x8 @ 16K, that is VERY strong- I wonder what it turned on the stock muffler...14.8 maybe?

rmenke

My Feedback: (13)

Razor:

Get the webra and chuck one of those worthless OS junkers out. Break it in correctly, add Jett Stream pipe. If its not all I try to tell you it is, will buy it from you while still in good condition at what you paid for it. How's that for putting your money where your mouth is???? ENJOY

bob27s

My Feedback: (19)

Yeah, there are few out there running fairly well.

16K on the 10x8 is pretty stout. But is right where it needs to be for both the engine and the muffler. So its working well as an assembly, and its well matched for the airframe it is in. Clearly, it enjoys the 10x8 prop. I will have to make a note of it.

Best I was able to get comfortably out of the OS55/Jett combo was around 15,500+ on a 10x7 ---- but I didnt push it real hard (wasnt my engine). And that was in Ohio air

Where guys go wrong with the OS55 is trying to get it turning 17K rpm ..... just aint gonna happen.

Destiny-RCU

I have a question with the OS. The prop doesn't need to be a 10" prop? Could the engine performe well with say a 9x9 etc. The prop size doesn't make a difference just as long as it's loaded down to it's proper RPM range?

Flying freak

what kind of fuel are you running my os turns a 10x7 at about 12000 with 15% powermaster on standered muffler .....

freakingfast

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That's real low, even for a stock muffler with baffle, less than 1 hp.

freakingfast

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I am waiting for some longer screws with inch threads for my muffler extension and will test my OS 55. I have an Ultrathust muffler, not a Jett.
I'm not overly impressed with the power of mine running the stock muffler/baffle, but it sure runs nice. looooow idle, smooooth transition and sips fuel.
I want to see if I can emulate the numbers that T-34 gave me, I did notice he can't fly very long, he sucks his tank dry in 7 minutes or so.
No free lunch for power.
Food for thought; do you know how well a YS-45 SE runs with the stock muffler? Well it runs like cr@p. And it's a screamer on a pipe/tuned muffler.

bob27s

My Feedback: (19)

Doesnt always work that way.... and depends on the way the engine unloads (or doesnt unload) in flight.

In that particular application......... it needs disk area and airflow.

Razor-RCU

My Feedback: (50)

Freakinfast- That is my favorite example of stock vs pipe or UT, the YS-45. It typically did not even come with a muffler. I tested mine once with the stock muffler and it was within 200RPM's of an OS-46FX

On a pipe, well it is right behind the Jett-50

Bob is pretty much the voice of God for engines but I can add that even if it would spin a 9x9 in the "power-band" for RPM's it only works on a sleekish airframe to get good use of the 9x9 anyhow. Have you ever seen a DF fly? it takes a good distance before the prop(s) become efficient and get on "step".

I have run patriots with a 9x9 but only because I had a Jett-50 up front. Otherwise it was 10x7 or 10x8 to find a balance of vertical and some speed (OS-50SX, Irvine-53, etc.)

freakingfast

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Naaahhh

bob27s

My Feedback: (19)

Not sure about that..... but I try....
And my voice seems to carry substantially less weight at home !!

freakingfast

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Well I saw T-34(Joe) yesterday and I made a boo-boo. I miss quoted him. His OS 55 was turning a 10x8 @ 15k not 16k. Sorry y-all.
I did manage to put the Ultrathrust on my 55 and got a nice surprise. On my Goldberg tiger II (40 size) I run a 10x7, 3 blade Master Airscrew for clearance, climb rate and braking. The 55 with stock muffler and baffle was 11,700 and with the Ultrathrust it jumped to 14,000 backed off 300 rpm rich. This is about 2 Hp at only 14k.
I would not hesitate to recommend this combo for performance sport. Low noise, hover with fast climb out, cool running, fuel efficient and great speed. Now let’s see how the engine holds up. Last week Joe was lapping me, now I'm got him by 3-5 mph.

t-34

hey this is the T-34 (Joe From Mather) I am now running a longer Mac tuned pipe and now spinning a 10 x 9 @ 15500 on the ground , the 55 still unloads once air bourne and my flight last only 4 minutes 30 seconds . And on the topic of going to a nine inch prop , I tried it once and there was not enough air flow for the plane to barely take off , for the world models T-34 you need a 10 inch disc . I even have some bolly 10.5 x 8 I look forward to retesting agian with this new exhuast combination . 1/9/08

jvino

Which is better the Jett or the Performance Specialties muffler???

t-34

Jvino _ It matters what you are looking for in performance . I can not make suggestions yet on the longer tuned Mac pipe yet due to the fact I only have 2 flights with it and one flight involed a 100+ mph touch and go , ( and yes the plane survived ) i should be have a better understanding of the new combination on sunday , but I Loved my Jett pipe and Have them on our Radical Profile plane w/ a 46 ax and on our goldberg tigerII with a 55 ax . In short any thing is better then stock muffler

freakingfast

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Joe now holds our field record for the fastest touch and go......just short of a crash LOL

jvino

I am looking for an even power band not to concerned with top end. My OS 55 is currently on a profile plane with a 13x4 prop. I would like to get a little more power to hopefully get to a 14x4 prop. I know that my application is not extreme speed but performance is performance. Thanks so much for your help.

Jeremiah

freakingfast

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Both are very good tuned mufflers. The Jett seems to make magic happen higher around 15000 and the Ultra Thust (Performance Specialties ) around 14000.
I have the Ultra Thust and I prefer it. I'm sure Joe will say the same about his Jett. Performance Specialties sells a Longer version which my be just the ticket for the 14X4 prop.
The broadest/smoothest power band will be had with the Macs 8.5 Quiet pipe, even better for a profile plane.

Edit:
I just ran the numbers and a 14X4 may be a bit much for the OS 55. It will be sub 12000 rpm, so the standard Jett or Ultra Thust definitely won’t help.

jvino

Thanks so much, not a big fan of pipe mounting so I guess I will try the Performance Specialties muffler.

t-34

Hey There Freaking -- I May have the touch and go record but you my friend have the 90 degree @ 170 mph record ( your Diamond Dust ) the fast and tightest loop record ( your viper ) and about a hundred more records too .... I mean yeah I may be fast but you were hallin' ***** when you passed me !!!!

jvino

Thanks for the update freaking. I appreciate it.

How exactly do you "run the numbers"?? What does the 13x4 come out to?? I wonder is the Webra 55 on a performance muffler will turn a 14x4??

Thanks again,

Jeremiah

freakingfast

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Joe, I think that we both hold the field record of one of the hardest mid-airs and both planes survived Ive ever seen when our T-28's got together last weekend. LOL.

Fixed that hole ya made in my wing and found a new right main gear.

freakingfast

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Jeremiah

There are two free programs that I use to run the numbers.

http://homepage.ntlworld.com/barry.hobson2/ and look under “goodies”
This works ok but the thrust out put stays the same when you change the pitch.


www.mvvs.nl/prop-power-calculator.xls
This one is more in depth.

Guys at our feild are running Webra 55s with APC 12.25x3.75 props and Webra Mufflers. The Jett and Ultra Thust were too peaky for 3-D on this Webra (on or off). A 13X4 and 14X4 are too big for the Webra.
This Webra likes higher RPMs than the OS. Both great engines for different Jobs.

jvino

Thanks for the info on the webra. I guess the OS 55 is the ticket. Also thanks for the calcs.