5.0Rick

Hi All,

I finally got my Rossi 53 installed on my Sky Raider and I am thinking there might be something wrong with it (not enough power). I ran some numbers in ThrustHP and according to the numbers it is only making 1.6 HP and not anywhere close to the 2.3 HP that is advertized. Could it be that the engine is not broken in yet? I have ran approximately half a gallon through it. Could it be the Rossi mini tuned pipe holding it back?

Here are the specifics:

Rossi 53 with the Tuned Mini Pipe (Black pipe)
Rossi R-6 Glow plug
Power Master 5% Nitro 18% oil

APC props and RPMs achieved

10x7 15,000 RPM
9x9 15,580 RPM
9x8 16,380 RPM

If you have the same setup, I would like to hear from you.

Thanks,

Rick

vertical grimmace

My Feedback: (1)

Those numbers do look a little low. Especially for the 10-7. I am sure my OS .46 AX was spinning that prop around 16,000 or so. I have a .67 and have not run it much but I was not blown away by the power when I did run it.

Julian537

My Feedback: (9)

put the jett SS pipe on it and watch it scream (black short one)
18160 on a 8.5*7.5
unload it!
mini pipe may be holding you back!

vertical grimmace

My Feedback: (1)

I do wonder about that muffler. My .67 has the black mini pipe muffler as well. I wonder if that engine really wants a full pipe. They advertise to run a 12-12 prop on it for pattern but there was just no way it would spin that.

Flyboy Dave

My Feedback: (21)

Could be....that is really the run-of -the-mill pipe for the Rossi's. They do
a fine job for what they are, but I would expect better performance with a
better pipe. I get over 18K out of my .45 with a Rossi long pipe....

....and it is a generic pipe for the 45 through 60. I would suspect it would
work fine on the 51 as well, but you would probably have to go down to a
9-7, 9-8 prop for some serious RPM.

You might want to try something other than the APC prop as well for RPM.

FBD.

still4given

How short is that pipe? It may be that it is too short for the props you are running or too long. You might try flying it with a 9x7 for a few flights and let it turn up. Things might still be a little tight.

combatpigg

My Feedback: (3)

Doesn't anybody believe in getting a baseline reading with open exhaust?
The mechanical checks to see if you are beating a dead horse are easy to do.

Flyboy Dave

My Feedback: (21)

....very, very true.

vertical grimmace

My Feedback: (1)

I like running open exhaust! Reminds me of a time long past. I think I will try that.

freakingfast

My Feedback: (3)

SG Model engines also list a Rossi 60 with a Pitts muffler @ 2.9 hp. , I don't think so.....With open face or tuned pipe maybe closer to the number.
I did a Sky Raider but it was very prone to flutter at high speed(all control surfaces) and would be too much work for me to justify the mods to fix it. My main probem was I over powered it (OS 55 ax & 11x7) and cleaned it up to much (cowling /race wheels). It served it's purpose, I beat someoneI gutted it and sold it at a swap meet. These are fine planes with just a plain Jane 46 engine. Just don't get carried away like I allways do.

5.0Rick

Thanks for the tip. I will try that, just one question... How do I pressurize the fuel tank without the pipe installed?

Rick

5.0Rick

Nice looking plane! Did you fabricate the cowl? Fiberglass I take it? Very nice work

I also encountered the flutter issue with the ST 51 installed. Fixed it by installing aileron servos on the wings.

Rick

bob27s

My Feedback: (19)

Sparing the tutorial on published HP info, can you identify where is the engine advertised as producing 2.3 HP ? Also, please note the rpm that might be suggested at which it develops that power?

you are on the right track - the "45 size" rossi mini-pipe is rather short-tuned. Needs to be propped to turn over 16,500 to function worth a hoot. Also, the o-ring style mini-pipe tends to leak at the o-ring if you to not properly support the tail of the muffler. Gas leakage past the o-ring can cause problems and inconsistant running.

The 9x8 info you have there is about in line with where it will want to run. In the air it probably comes on the pipe just about right. Something more along the lines of a 10x6 should turn up there too.

However, the 53 is bit lower timed (IIRC) than the .40 and .45 engines. More intended for the quiet euopean market. More along the lines of the Jett .46 and OS .46 timing. The displacement gives it some extra oommph to turn a bit more prop. So it can and does run well at lower rpms with "quiet" props, when combined with a properly tunned full-side pipe. It will be much better off with a full sized pipe, or a broader-band tuned muffler.

5.0Rick

Thanks for the reply Bob. I got the HP info from SG Model Engines (where I bought it) From their site "This engine is specified for 2.3 Horse Power at 16000 RPM."

Here is the link.

http://shop.vendio.com/RossiEnginesU...272/index.html

I did read the pipe support info from another post and bought a pipe support from my LHS.

Can you please suggest a tuned full side pipe?

Also, is it possible to change the timing on this engine?

Thanks again,

Rick

bob27s

My Feedback: (19)

I would suggest the 7.5cc pipe from Macs - quiet pipe is pretty good.
Mac's can also supply a header for the engine.

rossienginesusa apparently offers modified sleeves and crankshafts for the engines. Perhas they might be the best contact to evaluate your current engine performance and desired performance for your application. It has been a while since I evaluated one of the rossi engines or played with any modifications to one.

Although long ago, I had a Rossi .61 RE that was somewhat tweeked - hauled my 9.3 lb EU1-A uphill quite nicely at the time. But with such tweeks go away some user friendly tendencies, and also reliability. But it ran well most of the time, and was a real monster of an engine as long as I used the 10.75x7.5 modified Max Daley props so it could turn up a bit and stay on the pipe. Sure with I had a Jett 90 way back then ---- life would have been a bit more, well, reliable....

rmenke

My Feedback: (13)

FF:

Overpowered it with a OS 55 yet? Nah, next time try the 90 VRDF with a 10 X 9 & tack to 24,500. Should get the juces flowing. ENJOY Bro 119

freakingfast

My Feedback: (3)

Yup, it could get exciting when the control surfaces come off or a servo lets go. The 55 & tuned pipe was Waaaay too much unless you pointed it strait up Anything more than a 46 and stock muffler could have flutter problems on a Sky Raider.

freakingfast

My Feedback: (3)

I have run open faced engines on the test stand only and the fuel was gravity fed. A tube pointing into the exhaust port could work too on a plane but I don't need the noise.
The cowl was made of formed balsa sheet and covered with Monocote. Installing aileron servos on the wings would have helped but I think the ailerons still needed to be shortened and or thickened. The vertical and horizontal stab framework need to be replaced with a solid sheet with a strip of carbon fiber on each side. The elevator and rudder should be a tad thicker than the stabs and a bit narrower the originals. It's just more work than I want to put into this kind of plane. If I were you leave the Rossi as it is and enjoy the great handling Sky Raider, it's an easy 100 mph now and no mods needed. When your ready, move on to a quickie 500 class like a Viper. Need more speed ? Put an Ultrathrust or Jett tuned muffler on that quickie.

combatpigg

My Feedback: (3)

, Yep, for our purposes getting a baseline reading with open exhaust on an engine of un-known quantity is a place to start. Like already said, just open the needle up enough to compensate, this is just going to be a bench run. Make sure you can start from the very rich end and walk it in from there. If the cylinder will stay pumped [after an exhaust prime] indefinitely, then you have something to work with. If the cylinder leaks down after a few seconds, the engine is past its' prime, or never did get broke in right. No amount of running will magically rearrange the gouges and scratches to regain a bad seal. The crankcase needs to be airtight at the front bearing, head and backplate. I check for this quickly by fixing a sealed off straw down the intake and duct taping off the exhaust. Dunk the engine in water as you blow into the straw with moderate pressure and watch for airbubbles. Turn the shaft and continue to watch for bubbles. The final check is for axial play in the crank/bearings and to see how much slop is in the rod, typically a piston will have 10 degrees of dwell either side of TDC if the parts all fit good. Check for axial play with the prop installed and put side force into your effort as you rotate the crank by hand. With just the lower end installed [no piston connected to the crank] you should be able to just flick the prop and it should freewheel for a couple of seconds. With the piston connected, the prop should toggle back and forth from either side of TDC when flicked. If the engine doesn't pass all the tests with flying colors and it doesn't have the fits like these that have been quickly described, then it is up to the user to make it happen if you want top performance.

BTW, if you want to run open exhaust in the air, forget about having a throttle, might as well use an over size venturi and either pressurize the tank with a backplate tap fitting or go with a high pressure bladder and fine tooth, locking collet needle valve.

5.0Rick

Thanks for all of the info, I really appreciate the help. I will check the engine out.

Regards,

Rick

combatpigg

My Feedback: (3)

5.0, hope it works out to be a good engine. One note about breaking down a motor that's been run, it is a good idea to install an index pin so the liner can be put back exactly in the same spot it came out of the case. If the engine doesn't pass a leak down test before dismantling, then disregard. What you should do then is buy a hunk of maple or walnut and put the engine on a display plaque .

5.0Rick

Hi Guys,

Well, everything checked out on the motor, so I decided to make some mods to see if I could get the power up. I carved fangs into the sleeve to assist with the airflow, polished the rough scratches out on the newly created fangs with (1000 grit sand paper and increased the Exhaust timing by 10 degrees to 170. The Rossi 53 has very mild exhaust timing. I also used a degree wheel to document the timings (by the way, TDC is 0, BDC is 180 on a 360 degree wheel). Here are the results.

Exhaust timing 160 (open at 100 closes at 260) changed this to 170 (open at 95 closes at 265) I opened up the top center middle third of exhaust port - rounded.
Intake timing 134 (open at 113 closes at 247) left this alone
Crank intake 208 (open at 212 closes at 60)
Blowdown 13 degrees, after exhaust timing change it increased to 18 degrees


Since the exhaust mod alters the compression ratio, I decided to document this as well. I used the timings to position the piston in the cylinder and measured the before and after compression strokes. I also used a buret to measure the volume of the combustion chamber. Here are the specifics on that:

Button volume (combustion chamber) .5 CC
Bore size .876
stock compression stroke .585
new compression stroke .545
shim .005
quench area (area between the piston and the button at TDC) .018

I put all of this data into a compression calculator and this is what I got:

Stock compression 8.94:1
New compression with shim installed 8.4:1
New compression with no shim installed 8.94:1

I opted for the no shim installed configuration since it put the compression about where it was before the exhaust timing mod. I also changed the glow plug to an OS #8 and kept the 5% nitro 18% oil Power Master fuel. I decided to see just how fast the motor would spin after the mods, so I installed a small (sorry no markings) prop and tached it at 22,500 RPM [sm=tongue_smile.gif]

I then installed the 10x7 and tached it at 16,300 RPM. Much better! ThrustHP calculates HP at 2.165, not 2.3 but I can live with that number for now. I wonder how much a full pipe will help?

Rick

Julian537

My Feedback: (9)

Rick,

Do you have any pictures of the mods you did? Where did you get the small degree wheel?

I think a full pipe will make a big difference!

combatpigg

My Feedback: (3)

5.0, nice going so far. Don't over look the importance of lightening the piston and rod as much as possible, plus the possibility of notching the bottom of the piston skirt to uncover the boost ports. The crank counterbalance could also use a scoop of material removed to assist flow up the forward boost port as the piston begins the down stroke. The rod beam can be shaped to more of an oval cross section. All these little things add up.

5.0Rick

I hope the degree wheel from here. http://www.lucasinjection.com/Degree_wheel_100.jpg it printed out fairly small (4.5 inch diameter or so), no need to scale it down.

Sorry no pictures. BTW, I used the following tools.

Dial indicator for finding BDC and measuring the stroke
Buret for CCing the combustion chamber
Caliper for measuring bore and shim

Rick