[elippse]

Does anyone out there have or know where to get a torque curve of the STOCK O-200, especially one that goes out to around 4500 rpm? Any help will be appreciated!

 

[N316RV]

Try Formula I Forum

Try some of the Reno resources and forums for Formula I. They will be the only ones who run these engines to those kinds of rpm.
Alan Jackson

 

[osxuser]

Does anyone out there have or know where to get a torque curve of the STOCK O-200, especially one that goes out to around 4500 rpm? Any help will be appreciated!

Uh oh, if elippse is asking about torque curves of a stock O-200... turning at 4500 rpm... it can only mean one thing.

I don't have any DATA for you, but our little F1 really needs to see about 3200 rpm before it starts getting anywhere, and it's DONE at about 4100, anything more than that and we are just beating air with it.

What materials are you looking to use? Seeing what happened to an Owen's carbon prop that has the wrong mods makes me wonder what material would hold up to a more curved design. I suppose if it was completely symmetrical in it's taper to the tip it should work ok. The twisting force on the blade did one of Owen's test props in.

 

[elippse]

Uh oh, if elippse is asking about torque curves of a stock O-200... turning at 4500 rpm... it can only mean one thing.

I don't have any DATA for you, but our little F1 really needs to see about 3200 rpm before it starts getting anywhere, and it's DONE at about 4100, anything more than that and we are just beating air with it.

What materials are you looking to use? Seeing what happened to an Owen's carbon prop that has the wrong mods makes me wonder what material would hold up to a more curved design. I suppose if it was completely symmetrical in it's taper to the tip it should work ok. The twisting force on the blade did one of Owen's test props in.

I did two prop designs for Reno F1s, and neither achieved the design 4500 rpm; both of them wouldn't get much over 4100. I finally realized that although you can use a linear HP/rpm out to 3200-3600 rpm, that above this point the torque starts to drop off so that the HP increase with rpm also starts to drop off. That's why I would like to get a real torque curve to put into my equations when I design the next one. Neither of those props, which were carbon over wood, had any problem with coming apart. They were designed for a tip Mach of 0.85 at 4500 rpm and 265 mph. You may have seen Charlie Greer's "Bow-Tie" prop 3 years ago. According to him, it gave him about 6 mph more speed at the same rpm as his original prop, but would only turn up 4100 or thereabouts. The three blade props I designed for Tom Aberle and Jeff Lo, and the four blade for Tom, were both designed for a tip Mach of 0.85 at their rpm and speed, and there is no problem with separation or delam at the tip, and they are extremely quiet! Those props are all much shorter than any of the others!

 

[osxuser]

I'm curious why design for 4500 rpm then? Wouldn't a slightly longer/more pitched prop turning around 4000 be a better option. I understand the basics of prop aerodynamics, but am mostly an engine man

It seems (to me) like Owen's props aren't really that effective a design as far as shape goes. We run an unmodified one (or two ), but most people modify the tips for some reason or another. As i'm sure you know, his props are solid carbon... I personally thought a wood core would work fine, but everyone and their mother told me that those would fly apart...

 

[elippse]

I'm curious why design for 4500 rpm then? Wouldn't a slightly longer/more pitched prop turning around 4000 be a better option. I understand the basics of prop aerodynamics, but am mostly an engine man

HP is proportional to rpm up to about 3000 rpm, then increases with rpm at a lower rate because torque is dropping off. To get speed you need HP, and there's more HP at 4500 rpm than at 4000 rpm! To go 1% faster requires about 3% more power. HP=lb-ft x rpm / 5252. I now have a torque curve up to 2750 for the O-200, and it runs about 198-200 lb-ft from 2100 rpm to at least 2750 rpm.

 

[leeschaumberg]

More Power = More Speed

Quote -

HP is proportional to rpm up to about 3000 rpm, then increases with rpm at a lower rate because torque is dropping off. To get speed you need HP, and there's more HP at 4500 rpm than at 4000 rpm! To go 1% faster requires about 3% more power. HP=lb-ft x rpm / 5252. I now have a torque curve up to 2750 for the O-200, and it runs about 198-200 lb-ft from 2100 rpm to at least 2750 rpm.[/quote]
Hello
Torque does NOT equal power or speed. The formula 1 cars have very little torque under 10,000 rpm but they do go fast and have a lot of power at 19,000 rpm. The most efficient prop has fewer blades. The continental O200 is not designed to turn 4500 rpm. Power yes power drops off up there. To get more SPEED gear down a good 2 blade prop. Having been a research tech for 4 engine manufactures I have been there. I have a 2cycle engine that turns over 8,000 rpm at max power. On it I put a 2 to 1 gear box for a maximum of 4,ooo prop RPM. Prop diameter was about 64 inches. If you want to run the conti at high speeds gear the prop down. As the prop tips get close to mach 1 they get very noisy and inefficent.
Good Bye

 

[osxuser]

Lee,

Elippse probably knows what he is talking about when it comes to prop designs... he's done some amazing stuff at reno and for sport airplanes. That said, I think whoever he's making a prop for is probably barking up the wrong tree trying to turn the O-200 much past 4100.
We can make 4300 RPM with slightly less pitched prop, but don't go any faster than we did making 4100. We had some engine work done and got the extra RPM (Power?) without the gain speed.

That could be a result of the prop being inefficient at those RPMs, but it's spurred us to play with the idea of a pitchier prop for the races this year. (We have three different pitches). I understand the advantage of the extra RPM, but I'm thinking that valve train and a few other things about the O-200 limits efficiency up at 4500.

But thats racing isn't it? Everyone looks for the edge somewhere.

 

[rvbuilder2002]

If you want to run the conti at high speeds gear the prop down. As the prop tips get close to mach 1 they get very noisy and inefficent.
Good Bye

Problem is...the Formula 1 Airplane class requires running a stock (sort of) O-200 but you can run it at what ever RPM you want to. May not be the best, but to be competitive, you have to turn them fast.

 

[Canadian_JOY]

Ummm... Dumb question here from a big fan of small Continentals. How long do these engines last while turning those speeds? My expectation is that operation above rated RPM brings with it an extremely logarithmic service life derating curve. Guesstimate less than 50 hours at 4,000 RPM? Since I know nothing about air racing is it safe to assume the engine gets torn down after every trip to Reno? If so that makes racing a pretty expensive habit.

Hmmm, now let's see how much HP that is. WOW, that's a lot from 200 cubes!

 

[osxuser]

Ummm... Dumb question here from a big fan of small Continentals. How long do these engines last while turning those speeds? My expectation is that operation above rated RPM brings with it an extremely logarithmic service life derating curve. Guesstimate less than 50 hours at 4,000 RPM? Since I know nothing about air racing is it safe to assume the engine gets torn down after every trip to Reno? If so that makes racing a pretty expensive habit.

Hmmm, now let's see how much HP that is. WOW, that's a lot from 200 cubes!

Well everybody does things differently. We run a "race" engine for two to three seasons, but that only equates to about 15 hours on our speciality bird. (Race #3, Sly Dog). We also have a spare engine, which is pretty much stock, and kinda run-out, but would get us through the weekend if we had major problems with our Race motor.

Running a Race engine hard, and the cam/tappets pretty much are DONE at 25-50 hours from (at least thats what I hear from talking to other people.) This is all assuming that we don't blow something else up first. A guy somehow blew up a lifter body at PRS this year. I'm not sure how that works, i'm guessing corrosion inside it.

Some teams do an overhaul every year, some do a top every year, some don't mess with a good thing...

I'm guessing we are putting out around 130hp, we have a tricked out top end, fairly stock cam (limited, but some teams have more aggressive ones than ours), some carb work done (again, limited) mag timing bumped a bit, and some other stuff that is propriatary...

Yes, F1 air racing is expensive, but NOTHING comepared to T-6, Sport or Unlimited. To be competitive in sport you have to have a $500K buy-in now (NXT... or a Legacy with a MONSTER motor).

F1 can be done for a $15,000 Casset, and run in the bronze for fun. Put a $25,000 engine and some elbox grease on the airframe to clean it up, and you can be pulling yourself around the silver race. Or just buy a gold racer for around $65K and run from there. Learning curve is steep to buy straight into the gold.

I'd imagine the Biplane class is about the same costs, but more practical for day to day flying. But F1's go faster

But back to props.... who's gonna be running an elippse prop next year ?