iflyg450

Well I just broke my last 7x3.5 prop. Can't seem to find anymore, anyone suggest a different prop? The engine is going in a Sig Hummer. The 09 is 1oz heavier then the 051 but that plane was made to fly old standard servos and large 72rx So running HS-64hb and a park spektrum rx. I think the plane should move along pretty fast.

DeviousDave

APC6.3-4 maybe?

combatpigg

My Feedback: (3)

I'm guessing a 6x4, maybe even a 5.5x4, 5x4, etc., but just guessing.
The "fun" part about speed is trying different props to see what works with each plane.
APC does have a pretty great selection once you get into their catalog.

Mr Cox

If you absolutely want something close to the cox 7x3.5 then there is a Revup 7x3.5 (wood) that is very similar in shaope and load, and can be found at Brodak. The revups have a much better shape than Zinger props.

But for a speed project there is plenty of offerings from APC. The 6.3x4 is a nice one and it has been meantion above and there is also a 6.5x5 that could be trimmed down to suit.

gcb

I would try a 7x4 or an 8x3. The TD .09 is closer to some .15's in power.

George

Cox International

My Feedback: (10)

Don't run a 5" prop on a TD 09.

Cox recommends props from 6x4 to 8x4 for that engine.

We do have the original Cox 8x4 grey competition props for sale:

http://coxengines.ca/product.php?pro...2&cat=9&page=3

and they are a good match for Cox 09 and 15 engines.

We also have a small quantity of grey competition 6x3 props left but those are too small for the 09 engine.

Bernie

MJD

My Feedback: (1)

7-4, sure, that would move it along decently. But I don't see why you would ever fit an 8-3 to an .09 on an overpowered 1/2A sport model. Maybe a sport scale biplane or other draggy type of airframe, sure. At 17k, which I am sure it will not manage with that prop, the pitch speed is only 48mph.

The TD .09 makes its best power around 17.5 - 18.5k, peaking between 18 and 18.5. It will sit there all day with no complaint. The 7x3.5 runs in the high 17's, and unloading to 18k gives a pitch speed of 60mph which is somewhat better. 6" diameter is plenty of disc area for the Hummer, so it makes sense to find something in that range with enough pitch to load the engine to 17 or a bit more on the ground. 4 inch pitch at 18k can get you close to 70mph.

Cox International

My Feedback: (10)

Here are the official test results for a Cox Tee Dee .09 run with 25% nitro:

6x4: 18,500
6x5: 16,500
7x 3.5: 17,000
8x3: 14,000
8x4: 13,700

Bernie

Jim Thomerson

According to Aeromodeller review TD 09 on 30% nitro peaks around 19,000. I have flown them a lot in CL stunt airplanes. with Cox 7 x 3.5, 10 % Sig Champion fuel with 20% oil half synthetic/half castor, with back plate pressure and one way valve in the pressure line. I turn them loose at around 15,000 with that set up. Leaned out on the bench they will blip up to 17,000 on the same fuel and prop. I am presently flying an Italian copy of the Cox 7 x 3.5. The Cox props show up on eBay. I've only flown the grey ones, but now have both black and white versions, but have not tried them. I used to fly the TD 09's on high nitro fuel, but I think I like how they handle on the 10% better. Years ago, I opened up the venturi as far as it would go, ran high nitro, and promptly broke a crank.

I've not tried an 8 x 4 grey, but there is some figures in and old Aeromodeller which suggest that a TD 09 will turn an 8 x 4 about the same as the old non-schnurle Fox 15x.

combatpigg

My Feedback: (3)

So, in other words the TD.09 has zero potential to be as fast as the TD.049?
The speediest possible prop for it is the 6x4 at 18,500?
70 mph...that's it?

I can't think of any reason why a TD 049 can be propped to do 110-115 mph and a TD.09 can't.
Unless the weight of the bigger/heavier steel piston is the limiting factor.

MJD

My Feedback: (1)

I bet it has more potential, but it looks like it needs a sub 6" prop with more than 4" pitch. I only know that the tests I've seen show peak hp in the 18k range while the stock .049 is up in the 22k range, so I suppose that suggests it is timed somewhat more mildly too. Bernie notes it spins a 7x3.5 at 17k, the Aeromodeller test shows it gets into the higher 17's on that prop. It's certainly well matched to the engine, for GP sport use anyhow.

Here's some info from Dr. Hepperle's site. Whatever the peak hp may be, the curve shows the drop off at rpm around 20 and above. The only TD .049 data there is from when I was a year old, so dunno how current that is, but it suggests the .09 has about 2.2X the peak hp of the .049 at around 80% of the rpm, so it's torquier per unit displacement by comparison.

Time for you to get yer hands on a TD .09 and start shaving.. mind you I wonder what the conrod/ball joint limitations are.

combatpigg

My Feedback: (3)

Yes, I'll bet the piston is the first thing to look at. It would be nice to know how much time Cox spent with R&D and if so, what they tried doing with it.
The piston of a guinea pig engine could be shaved and tried without the Cox Police showing up with the handcuffs if a guy is sneaky about it.
To put this in perspective, a ASP .10 will do 110 MPH with a 6x4 prop...so the resultant rpm is in the mid to high 20s. Trying to get a Cox.09 into this realm might be like beating a dead horse?

buzzard bait

Wow, I didn't know Brodak brought back the Rev-Up line. Just checked it out...I see the choices are kind of limited, but yes, I bet the 7x3.5 would be a great substitute for your Cox prop.

Unfortunately the 8x3 is not in their catalog, which is a shame because I'd love to try it on my PAW 06 and my OS 10. But I agree it wouldn't make your Hummer hum.

Has anyone tried the Brodak Rev-Ups? I hope the quality is the same as of old. Their Y&O repros several years back would barely stir paint.

Jim

Jim Thomerson

Back around maybe 1990, when there were 09's with mufflers and throttles, people in the St Louis area were running a 10 class pylon race. Engines were the TD 09 and the whatever OS 10. Engine guru friend was winning with TD 09 and complaining that he could not get just the right prop for it (had to run stock props.) I have a bunch of 7 x whatever wood props of various brands I bought around 1980 and tried on TD 09. None compared with Cox 7 x 3.5. If I couldn't get Cox 7 x 3.5's I'd try an APC 7 x 3.

The TD 09 is a legitimate 1.5 cc engine (as is the Johnson Bulldog 09). Rest of older USA 09's are over 1.5 cc. There was talk at one time of dropping various FAI events from 2.5 cc down to 1.5cc. Never happened.

MJD

My Feedback: (1)

Seeing that the .09 displacement class doesn't cater to any competitive events, in NA at least, it makes sense the .09 is set up as it is and that there were no follow on developments like in the .15 class.

These are the APC options that catch my eye as candidates for sport use on small to mid-size (for an .09) aircraft:

LP06340 6.3x4
LP06537 6.5x3.7
LP06550 6.5x5.0 (perhaps trimmed a hair)
LP07030 7x3
LP07040 7x4

Looking at the other curves on Dr. Hepperle's site, a cool relationship I see there is the TD .010 peaking at about 21W, about 50% of the Babe Bee's peak. 2.5 times the specific power output.

Mr Cox

The Rev-ups that I have bought from them during the last 1-2years are marked "series 3" and are very nice. They have a thin profile and are nothing like the Zinger for instance. The rev-up 7x3.5 is a very similar in shape and load to the cox 7x3.5 (black), that is why I recommended it above.

buzzard bait

That's good to hear; thanks.

fit90

I am not at my home computer so I may not have all info correct but I remember  going to gregorie.org and finding some really good info on different engines and their capabilities.  When I get back home I will check on that web site to see if I got the address correct.  It may be worth a look.  I remember some info on various tee dee's.

fit90

go to gregorie.org then go to free flight model flying then go to F1J/F1P engines.  There is a very brief comparison between the MP Jet .061BB and the Cox .09 Tee Dee.  No specifics on the Cox engine though.  However, the site still contains some very interesting stuff.

iflyg450

Well I did find a Cox 6x4 grey. Give that a try the hummer is almost don the AUW will be right a 1lb. Which will be perfect for the TD 09 and 212sqin wing. It should move along really well. Just as long as its faster than all thoes foam strykers at my field I will be happy. It shoud run right at the 90mph mark

EX Model Engines

Cox 6x4 grey was always my favorite for the .09!

DeviousDave

Weren't the 8-4's meant for 1/2A Texaco?

Cox International

My Feedback: (10)

Yes but many buyers use them for .09 and, especially, 15 Cox engines; hence we also market them that way.

Bernie

gcb

Cox made a white nylon 8x4 for the Olympic and Sportsman .15's way before the TD series, let alone the Texaco. I have no idea how the profile and hole size compares with the gray competition series.

Since I fly mostly sport, I tend to over-prop my engines compared to those in competition. Saves engines...especially ones with ball-sockets.

I would not hesitate to run my TD .09's on an 8x4.

BTW, if you run the Cox gray 6x4 on a TD .09 you will need to ream out the prop hole to fit the thrust plate on the .09.

George

combatpigg

My Feedback: (3)

I think Iflyg450 has made it clear that he's after speed and not an entry in the Rose Bowl Parade.
With that idea in mind, I find it amazing that any props larger than 6x4 have entered the conversation.
There's no substitute to actually being out there with your plane, a fist full of props to try and some way to measure the results.