Extreme Speed Prop Planes Discuss the need for speed with fast prop planes (Screamin Demon, Diamond Dust, Shrikes or any REAL sound breakin'''' plane)

Rossi .81 FIRE

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Old 12-22-2012, 09:24 PM
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Yak13
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Default Rossi .81 FIRE

I just got my hands on a Rossi .81 FIRE. It's a .61 bored and stroked to .81. Just want to ask if someone has used it for speed. I'm thinking a 10x12 or 10x14 prop, as it is a "long stroke" (around 1" stroke).

Ideas?

Thanks

Ed
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Old 12-22-2012, 09:43 PM
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Default RE: Rossi .81 FIRE

You wouldn't be interested in trading that 81 for a 90 FIRE would you? I just got the 90 and it looks to be a little bigger then what I thought. I have an existing airplane that had a 60 in it but will take lots of work to get the 90 in.
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Old 12-23-2012, 07:23 AM
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Default RE: Rossi .81 FIRE

Not sure of a trade. The .81 I like because it is small.
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Old 12-23-2012, 08:13 AM
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Default RE: Rossi .81 FIRE


ORIGINAL: Yak13

I just got my hands on a Rossi .81 FIRE. It's a .61 bored and stroked to .81. Just want to ask if someone has used it for speed. I'm thinking a 10x12 or 10x14 prop, as it is a ''long stroke'' (around 1'' stroke).

Ideas?

Thanks

Ed
If it's a DF engine the "long stroke" part is irrelevant - DF engines are set up to run best at DF rpm. An engine with the words "long stroke" attached to it isn't automatically a locomotive powerplant. It sound good on ad copy but the difference between "short stroke" and "long stroke" is relative and in this case probably doesn't mean much more than "longer than the .61 version". Those props, if you could find them, would bog it down (I doubt you would see much north of 15k), and you would be losing all the advantage a DF engine has to offer - correct porting and timing to generate maximum horsepower at DF rpm (20k plus). Even a 10x10 could be on the heavy side for shaft load but the engine might handle it fine if you set up the pipe length accordingly. APC 10x10 props are maxed out safety-wise at 19k, but you are in no danger of exceeding that. For all out speed something like a CF 9X10 would be about right. Try RocketRob on this forum, if he is still offering them. Guys overseas fly .91 DF engines on sport speed models with 9x10 props.

For some baseline numbers, a piped Jett 90L featured on Jett's site showed 16,300 on a 10x10. This is a .60 size engine with 11% more displacement than the Rossi .81 and timed for this general rpm range.
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Old 12-23-2012, 09:36 AM
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Default RE: Rossi .81 FIRE

Thanks for the coments MJD.

I'm not sure if it's a DF because it's a front intake. Could it be a DF engine?

Thanks again
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Old 12-23-2012, 09:49 AM
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Default RE: Rossi .81 FIRE

I don't think what you have is DF. At one time the rules for pattern stated the airplanes must use 10cc engines and weigh no more then 5KG. At some point in the mid '80's the engine size was upped. A few of the engine manufacturers responded to this by simply boring and stroking existing .60 engines. My guess is that if you measure the exhaust timing and the carb throat you will find a timing of no more then 160 degrees and a carb dia of 8 or 9mm. these would indicate pattern engine.

I hear you on the size thing. I was expecting my 90 to be closer in size to the 60 that the airplane was flying with. I'm very happy with the condition of the 90 though. Looks like it has only been bench run. There is no discoloration of the combustion chanber at all. As in any out of the box engine I buy, I have a new set of bearings on the way. After that it will be like a new engine. I will have to cut the nose off the exsisting airplane and move the firewall back 2" and lay up a new cowl then make a new header. More work then what I was wanting to do but sometimes thats the way it goes. Looking forward to seeing what a 6.5 lb airplane with 550 sq in and 8% airfoils is going to do.

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Old 12-23-2012, 09:51 AM
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Default RE: Rossi .81 FIRE

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Old 12-23-2012, 10:43 AM
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Default RE: Rossi .81 FIRE

The carb is 8mm. so it should be a pattern engine. If that is the case, what props do you think it will perform better with the idea of getting speed? I have some nice 9.5x12 carbon.
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Old 12-23-2012, 10:56 AM
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Default RE: Rossi .81 FIRE

I would start with an 11X12 APC. The way the engine is set up it will make it's best power at 13,000 to 14,000 RPM. Run the pipe at 14" from front of header cup to high point of pipe. The engine will respond well to raising the exhaust port. On my .61 I went .030. more power could be reached by increasing the intake duraration on the crank. I also machined the head button to reduce the compression so I could run 20% nitro.

For a few years now I have been racing my Rossi's against YS 4 strokes. The formula that I found to work best with the Rossi pattern engines is to take advantage of their huge torque. The Enya #3 plug has proven to work the best with 10% to 20% nitro. I usually set my needle just to the point of breaking into a 2 stoke and then the engine would unload and lean in the air.
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Old 12-23-2012, 01:30 PM
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Default RE: Rossi .81 FIRE

Oh yeah - FIRE - pattern version. Doh! I should lay off the forums the morning after a family wedding. Glad I was able to be of no help whatsoever..

I defer to speedracer's comments!

But you raised my curiosity - what are these 9.5x12 props you have?
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Old 12-23-2012, 07:00 PM
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Default RE: Rossi .81 FIRE

CL props. CF.

What are your prop suggestions? Now I am thinking either the 9.5x12 or a 10x10
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Old 12-23-2012, 07:01 PM
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Default RE: Rossi .81 FIRE

CL props. CF.

What are your prop suggestions? Now I am thinking either the 9.5x12 or a 10x10
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Old 12-23-2012, 08:19 PM
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Default RE: Rossi .81 FIRE

If it isn't timed and ported for speed....why not spend an hour or two and turn it into a speed engine...?
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Old 12-23-2012, 08:43 PM
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Default RE: Rossi .81 FIRE


ORIGINAL: combatpigg

If it isn't timed and ported for speed....why not spend an hour or two and turn it into a speed engine...?

Depends on what he intends to mount it in. If he is going to build a clean purpose designed speed plane like the euro cup guys then yes that may be of benifit. If he is going to adapt a current ARF or something then it would be better to take advantage of the engines bottom end grunt. With the correct pipe, prop, tuning and airplane he could easily end up with a 155 MPH airplane that runs like a Swiss watch. The only mods I did to my 60 was raise the exhaust port and throw on a 12mm carb. 9 times out of 10 I can bump start it and if there is a 10mph or better headwind I can idle down enough to land and actually taxi back. Really burns the guys on race day LOL.

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Old 12-23-2012, 09:36 PM
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Default RE: Rossi .81 FIRE

I'm sorry..thought this was the Extreme Speed forum....
If that engine was mine, it sure as heck wouldn't be condemned to run only 155 MPH.
155 is boring enough with a stock .40-.45
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Old 12-23-2012, 09:41 PM
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Default RE: Rossi .81 FIRE


ORIGINAL: Yak13

CL props. CF.

What are your prop suggestions? Now I am thinking either the 9.5x12 or a 10x10
Where'd you find that 9.5 x 12? That's a beefy prop compared to most of the choices I've found so far, sounds like it is made for D speed on a high nitro diet.
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Old 12-23-2012, 09:48 PM
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Default RE: Rossi .81 FIRE

A friend has one of these .81's...IIRC it's a nice running engine, had it in a Super Kaos 60 many moons ago...but it vibrates a bit more than the .61 it's based on.

I have never seen the DF version, but I think I recall reading in here somewhere about how the .81DF wasn't all that popular because of the vibration?

What I'm sayin' I guess, is that maybe as you work to get the r.p.m. up there you might want to consider that the higher you go, the more vibration you could have.

Edit: Who was / is the guy in Germany who did a whole (really cool BTW ) thread on DF engines, and the German Speed Cup, etc.?

Edit #2 (or would that be P.S. ?) MJD, in his post below, is right: http://www.rcuniverse.com/forum/m_52..._2/key_/tm.htm
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Old 12-23-2012, 09:53 PM
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Default RE: Rossi .81 FIRE


ORIGINAL: combatpigg

I'm sorry..thought this was the Extreme Speed forum....
If that engine was mine, it sure as heck wouldn't be condemned to run only 155 MPH.
155 is boring enough with a stock .40-.45
Well then Mr. Expert why don't you tell him how to set it up for max speed? What do I know anyways, all I ever did with my 60 was win the Norcal unlimited championship for 2012. I'm sure you did much better then that right? We're all ears master Pig.

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Old 12-23-2012, 10:03 PM
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Default RE: Rossi .81 FIRE


ORIGINAL: proptop

Edit: Who was / is the guy in Germany who did a whole (really cool BTW ) thread on DF engines, and the German Speed Cup, etc.?
I-love-jets (Stefan I think?)

That was the OPS engine thread I believe.

I get the impression there wasn't enough genuine speed activity in this forum for his taste. They take it pretty seriously over there.
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Old 12-23-2012, 10:12 PM
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Default RE: Rossi .81 FIRE


ORIGINAL: speedracerntrixie


ORIGINAL: combatpigg

I'm sorry..thought this was the Extreme Speed forum....
If that engine was mine, it sure as heck wouldn't be condemned to run only 155 MPH.
155 is boring enough with a stock .40-.45
Well then Mr. Expert why don't you tell him how to set it up for max speed? What do I know anyways, all I ever did with my 60 was win the Norcal unlimited championship for 2012. I'm sure you did much better then that right? We're all ears master Pig.

Unlimited What..?
A speed contest...?
An UNLIMITED Speed Contest..?
Is that what you're at this forum to talk about..?
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Old 12-23-2012, 10:19 PM
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Default RE: Rossi .81 FIRE


ORIGINAL: combatpigg


ORIGINAL: speedracerntrixie


ORIGINAL: combatpigg

I'm sorry..thought this was the Extreme Speed forum....
If that engine was mine, it sure as heck wouldn't be condemned to run only 155 MPH.
155 is boring enough with a stock .40-.45
Well then Mr. Expert why don't you tell him how to set it up for max speed? What do I know anyways, all I ever did with my 60 was win the Norcal unlimited championship for 2012. I'm sure you did much better then that right? We're all ears master Pig.

Unlimited What..?
A speed contest...?
An UNLIMITED Speed Contest..?
Is that what you're at this forum to talk about..?

So unbecoming when you play stupid. You know full well that I race in a warbird series. Like I said earlier put up or shut up! Tell him how he should set up his engine and then back it up with some real results. I suppose you will just be yourself though and just sling some insults. No worries, my stuff works in the real world.

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Old 12-23-2012, 10:29 PM
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Default RE: Rossi .81 FIRE


ORIGINAL: speedracerntrixie


ORIGINAL: combatpigg


ORIGINAL: speedracerntrixie


ORIGINAL: combatpigg


I'm sorry..thought this was the Extreme Speed forum....
If that engine was mine, it sure as heck wouldn't be condemned to run only 155 MPH.
155 is boring enough with a stock .40-.45
Well then Mr. Expert why don't you tell him how to set it up for max speed? What do I know anyways, all I ever did with my 60 was win the Norcal unlimited championship for 2012. I'm sure you did much better then that right? We're all ears master Pig.

Unlimited What..?
A speed contest...?
An UNLIMITED Speed Contest..?
Is that what you're at this forum to talk about..?

So unbecoming when you play stupid. You know full well that I race in a warbird series. Like I said earlier put up or shut up! Tell him how he should set up his engine and then back it up with some real results. I suppose you will just be yourself though and just sling some insults. No worries, my stuff works in the real world.

You're at the wrong forum. You want the pylon forum. This forum is meant for hot rodders who are into radical engine work, prop work and straight line speed.
Send me one of those .81s and I'll take time out from working on a street rod project/restoration to do an Extreme Speed Forum thread.
The "challenge" would be to top 155 mph with the .81.......
I'll send the engine back when the thread reaches it's conclusion.
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Old 12-23-2012, 10:31 PM
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Default RE: Rossi .81 FIRE

the rossi .81 engines aren't stroked they are just bored.. most were set to run at 21-22k rpm, yes the piston is heavier...lets get real, this for fun speed airplanes not endurance racing right? i believe someone has taken ducted fan middle case with sleeve/piston and rod and assembled it with standard front intake crank etc, this takes all of five minutes to swap out...you can use some cutdown wood props to run and set approximate pipe length, then buy some carbon props based on your test runs, and intended airframe, check headshims on engine and add two thick ones.. it will take the 25 percent nitro with them installed.. contrary to a lot of tales told.. rossi ducted fans have been run successfully with high nitro in boats as well
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Old 12-23-2012, 10:48 PM
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Default RE: Rossi .81 FIRE

lfinney..do you think the vibration issue can be helped with some work..?
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Old 12-24-2012, 08:50 AM
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Default RE: Rossi .81 FIRE

I was offering first hand knowledge of an engine I am familliar with and that puts me in the wrong forum? Looks like someone has a big fish in a little pond complex. I stated what the engine was and what was needed to set it up to get the most speed out of it without modifications. It is NOT a DF engine and is NOT going to turn 20K. If you guys want to mis-lead somone just so you can feed your ego's then I will leave you to it. The OP had my information and the choice to follow it.
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