freakingfast

My Feedback: (3)

After 150 plus flights on the Viper I was getting bored with it.... or is the Diamond Dust that quick? So out went the Evolution NT 46, Ultrathrust ,APC 8.75X8.75W and in to the Viper went a Webra 55 , Jett muffler and APC 9X 10. WOW what an improvement. Still not near as fast as the Dust but the Viper turns harder and holds speed through loops and 180*'s much better. The Viper's pathetically small fuel tank now allows only 3 1/2 minutes of flight time, but thats about all the adrenalin I can handle anyway.

Razor-RCU

My Feedback: (50)

FF- Did you ever try a smaller prop. like a 9x9 or 9x8 on the 55?

Got any pics?

freakingfast

My Feedback: (3)

Yes I have, the 9x9 with the red Jett muffler ran poorly, the engine liked the load of the 9x10. I've never seen this before. This engine died, the crank broke.
Two others are still running fine with more abuse & time than this one had. I just got a OS 55 AX to test. After break in I'll try a 9x9 and 9x10 on it. I think the OS 55 ax manual's prop recommendations are a bit optimistic or a mis print "Sport 12x7-8 13x6-7" or can it really turn that much prop at a decent speed? Keep in mind it's rated at 1.75 ps @ 16,000 rpm. By my calculations the engine will never get there with these props even unloaded. Perhaps mounted in front of an anvil from 10,000 feet.

PS the Webra 55 GT 2.1 ps @ ? rpm vs OS 55 AX 1.75 ps @ 16000

Razor-RCU

My Feedback: (50)

I totally disregard the HP and RPM #'s from the manuf. A 9x10 is a LOT of prop. for a speedy 55.

What rpm's were you getting with the 9x10?

Maybe cut a 9x9 down into an 8.5x 9 or just try a pylon prop like a 8.75x8

Methanolover

So your webra 55 crank broke in the air?? Mine did too!!! between the bearings at intake-port. Webra cranks often do, it seems. [:@]

Henrik

bob27s

My Feedback: (19)

9x10 is indeed a LOT of prop. THe quicker airplane helps a bit - engine will unload a lot in the air.

The key to the best peformance using the jett-stream muffler is getting the engine running between 16,500 and 17,000 on the ground. Although it does boost effectively starting down around 14,500.

Looks like you are on the right track though. The APC 8.8x9.25 may be worth trying.

(edit) Sounds like they bored-out the crankshaft a bit to help with mass-flow... but I have not seen one up close. Usually mfgs try to keep engine weights down by minimizing crankshaft and bearing sizes. Perhaps they pushed a bit here, and were not expecting much more than 11x7 props turning at 12,000 rpm

russm

i just put my new 55ax on a s.a. low wing stick w/ a 10x7 prop for breakin. this is a supprisingly fast airframe. i thought the same thing regarding prop size in the manual. what would be the best prop for speed on this setup? russm

freakingfast

My Feedback: (3)

The Webra 55 gt turns an APC 9x10 @ 16,300 rpm with the red Jett muffler. That worked better than a 9x9, both on the run in bench and in the air (no there were no air bubbles).

Razor-RCU

My Feedback: (50)

16.3K is impressive for that 55- My Webra Speed-50 turned a stock APC 9x8 around 16.2 give or take 200, on the stock muffler. Between the extra size and that "red muffler" I am not surprised!

Go smaller towards the pylon props. and let us know what happens- You are the first person I have EVER heard of running a 9x10 on a Viper style quickee-

freakingfast

My Feedback: (3)

I run the same exact setup on my two Diamond Dusts too! Four more clipped wing Diamonds Dusts are under construction to be powered by OS 46 df motors and YS 45 re.

I've concluded that the OS 55 AX is probably not a high speed motor base on RCU threads, so it will be mounted to my Edge 540 spinning a cleaned up wood 13x4 pro Zinger for fast spool up

Razor-RCU

My Feedback: (50)

Whatever... So you are not even going to try a smaller prop.?

freakingfast

My Feedback: (3)

Of course I will. I did'nt bring a 9x8, 9x9 or 9x10 this time. I feel the power is less than I expected. Could be it was mounted to flimsy profile fuselage.
After 1/2 gallon of break in time on the OS 55 AX I have some numbers:

On 15%, Just off peak, slightly rich. 50* air temp. Engine mounted side winder. Stock muffler.
11x6 Scimitar = 13,000 rpm
12.75X3.75 APC = 12,100 rpm
13X6 APC = 9,850 rpm
13x4 cleaned up wood Pro Zinger = 10,400 rpm

Very easy starting. Strong, even transition. No hesitation when stabbing the throttle after a long idle. Nice smooth low idle.

Razor-RCU

My Feedback: (50)

I mean smaller than a 9x10

freakingfast

My Feedback: (3)

More on the OS 55 AX. All props are APC. 15% nitro.
9x9 @14,300
9x9 @ 15,400 baffle removed on this and following.
9x10 @ 14,980
11x6 @ 13,280
11x5 @ 13,800
12.25x3.75 @ 13,090

There could be hope for this engine with an Ultrathrust or Jett muffler. Over 1000 rpm jump by just taking out the baffle with a 9x9.
I doubt that will match the Webra 55 in power. It would need to gain 1,300 rpm on a 9x10 to do that.

Razor-RCU

My Feedback: (50)

I do not think you are even in the power band with a 9x10, seriously...Even when I run a 9x9 on a Jett-50 some folks think that is too much, and the Jett smokes the OS-55...

MyWay

Put a SS tuned muffler on that OS 55 with a 9/9 and a muffler on the Jett 50 and see which one comes out on top.