Heliman4213

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Does anyone know where to get new 0.20 props ????

MJD

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http://coxengines.ca/cox-.020-propeller-4.5-x-2.html

This is the first hit when you Google "Cox .020 prop".

Pond Skipper

Recomend Cox 4 x 2.5 props

rc lifer

P.S. I have a stash of the COX grey 4.5x2 props. Did cox make a 4x2.5? Or was it another brand? I chased these props down on ebay and was using them on a small electric but they seem to break to easy on my belly lander XB-70. I use a a folder now Graupner 4.7x2.3 CAM blades with a Texas Timer hub. No broken blades with this setup.I am down to seven of the little Cox grey props. Dont want to brake any more of them!

Pond Skipper

I showed Bernie a video of my Lil Speedy on the 4 x 2.5 and requested he find the mold from his cox prop maker in California.
After a week of searching they found a mold that looked like the old 4 x 2.5 used on the Lil Stinker and a few other CL planes back in the day.
The prop was purpose made to make a Pee Wee rip with thrust and enough pitch to fly faster more suited for typical breezy days.
Bernie agreed he would run a test batch to see how they will sell, I would make a double order while the gettin's good.

http://www.ebay.com/itm/3x-Cox-020-P...ht_2019wt_1228


The 2P 4.5D props are ok in calm sub 8mph days or with larger .020 powered planes in calm winds.
Check out my Lil Speedy on the 4 x 2.5
Set your viewing preference to 1080HD as this is a small 21in span plane.





Here I have the prop on a stock TD .020 with exhaust throttle sleeve

https://www.youtube.com/watch?v=WyKwCxfHxf0

MJD

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I will order myself a small stash of those!

rc lifer

P.S. Ok I will defiantly be getting some of those, that little plane just hauls buns. Since they are the black plastic flexies I could use them on my XB-70, without braking them.

Pond Skipper

Yes tough lil props the batch was made about 3 months ago.

Heliman4213

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ok thanks guys

rcfan450

Hey you cox guys, I just got me a pee wee - ordered some 3 bladed props off ebay that were advertised for it, hope they work. Sorry to poach the thread here a little but what gas to you run in this little guy? Just regular ol nitro? I really like 30% Heli Cool Power for my elevation in all my bigger 2-stroke motor planes, but I have never ran such a small motor and don't know if it can take the same stuff?

MJD

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30% nitro is a-okay, 15% is minimum for a Pee Wee to run okay. BUT you have to watch your defintion of "regular" - in terms of the oil package. Small Cox engines need (not prefer) castor oil in the brew, and preferably over 50% of the oil is castor. At the very least you'd need to run Omega 15% but it is still not up to par for the long haul. There are 1/2A specific brews, and Sig has good fuels in the Champion line if your LHS has them.

Very desirable: 25% +- 5% nitro, 21-23% oil of which a good chunk is castor. Or all castor.
Okay: 15-30% sport fuel, synthetic/castor, with about 5% added castor oil.

It will run on your 30% but I hate to think of the wear and tear on the poor wee thing. Cool Power = Cruel Power as far as Cox engines go.

rcfan450

Thank you for your educated reply. I'll take your advice and just go find me some champion fuel. Looks like they have 25 or 35% I could go with. Thanks again.

MJD

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You're not worrying the motor in any way with 30-35% nitromethane fuel, that's pretty much Cox red can while blue can was 25% IIRC. I think plug life starts to get dodgy over about 40%, but I never ran over 35% so I can't say first hand. Castor is important because of the ball and socket joints on the conrod. Synthetic properties don't fare so well in there. That's why why you should have, oh I dunno, at least 10-12% castor if you can't have more/all - longetivity. And the .020 runs like crap on less than 15% nitro and doesn't run so well on 15% but it's okay. If you ever have an .010 - forget less than 25%.

ffkiwi

rcfan450- you should be aware that the 3-bladed 3-1/8" x 2-1/4 PeeWee props are generally WAYYY off balance as supplied and normally require quite a bit of fettling to get them in balance-I've found this more trouble than its worth over the years, and stick to the 2-bladed versions. Hopefully these were the props you ordered-anything bigger in 3-bladed format will overload the PeeWee (there are several possible other candidates out there-Cox 5x3 3-blader, and the WenMac 4-3/4" one. Sometimes its the hub rather than the blades which are the problem, in which case it is possible to use tungsten filled putty in the hollows in the back of the hub to improve the balance, and careful drilling of lightening holes in the adjacent solid sectors ....
That being said-if you can get one balanced, these props perform quite well on the PeeWee.....two other suitable alternatives (but quite hard to find) are the Graupner 5x2 and the G-Mark 115 x50 prop made for the Humming Bird 03. The latter is a particularly nice prop for small glows-one day I must clone it, as the originals are getting very scarce...

ChrisM
'ffkiwi'

rcfan450

Thanks for the reply Chris, I will definitely check the balance of them when they come. The nice thing about these tiny little motors as if they are a pain in the but it's not very expensive to just buy the two bladed versions

rcfan450

Well I got my little guy in the mail. Got me some 35% champion fuel. And I actually got it to run, sweet! Just a quick question, after-run oil? Do you guys use any? I used to run good ol WD-40 in my rc car nitro engines and it worked great. I don't even bother with my bigger nitro plane engines (cool power 30% says it has stuff in it for that so I don't). Just curious about this little guy and the different fuel. Sorry to hi-jack...

https://www.youtube.com/watch?v=5pKGceGfJr8

ffkiwi

Running nicely-that sounds a very healthy PeeWee! . I do use afterrun oil (but nowhere as often and as regularly as I should!)-if your fuel contains castor then it is probably a good idea-but ideally you'd want to put a couple of drops down the air intake of the Pee Wee-the reason being the reed valve seating-the big bugbear with all the Cox reed valves-not just the PeeWee-is that the residue from castor fuel is very sticky-and will 'glue' the reed in place on its seat if the motor is allowed to sit around after running. [I'm talking weeks or months here-I doubt it will be an issue after only a few days-such as one weekend to the next] Result-the engine won't run next time-runs out the prime then stops. Afterrun oils usually have detergent and penetrative additives to help get in all the nooks and crannies-so certainly help in this situation. If you're not running castor then its not really an issue-but most of us prefer castor for the sake of the little end ball joint. If your background is R/C cars then you'll be used to low oil, medium nitro synthetic oil based fuels-which while admirable for their intended use, are less than ideal for Coxes.
So if you're going to run it again in a few days, I wouldn't worry-but if its going to be several weeks or longer before it gets used again, then by all means introduce it to some AR oil.....

ChrisM
'ffkiwi'

PS The TD 010s and 020s can be just as frustrating in use-even though they don't use reed valves-in their case it's the 3 tiny jet holes in the venturi, plus the feed hole in the needle valve banjo that block up with fuel residue....

MJD

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Here's my report on the 4x2.5 props - you can see the problem yourself. Actually it is fun to scan your eye left to right, the right blade will wiggle for you.


I'll send them back with my observations, things happen. I'd check yours if I were you. The black 4.5x2 also showed some crookedness, it was acquired in the last two years. The greys I have are straight.

Not fit to bolt to an engine. You could never balance these, by the time you did half of each blade would be gone.

MJD

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BTW the eight pics are: prop 1 with the outline traced by pen, prop 1 rotated 180 degrees, then prop 2, prop 2 180, etc.

ffkiwi

This looks very much a classic case of not allowing sufficient cool down time after the mold is filled-this sort of distortion was well known in the heydey of injection moulded props and piecework rates-the workers were cutting corners in the cycle to produce more props, and hence earn more-but it doesn't work, as the reject rate shoots up considerably-as MJDs pics above demonstrate.....

ChrisM
'ffkiwi'

Pond Skipper

Bernie was going to run these in competition grey I have been waiting to buy some next. We need him to take a look at your pics Mike..

Pond Skipper

ahhhh bummerrr looks like I have a few bad ones too

Pond Skipper

I have messaged Bernie to take a look at the pics

MJD

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I was planning to send them back with a note to talk to the operator, I've been on the wrong side of injection molding before in mfg. I hesitated posting this here because I only wanted to let the core group of .020 fans know, and I have no intention of hanging a vendor out on display. Since this is a special interest thread I figured it was "ok" but I still wasn't sure if I should.

Pond Skipper

Right agreed, its just a matter of getting it fixed right away this is an appreciation thread and so is limited to just that.