buzzard bait

Just tried an APC 10.5 x 4.5 using S&P 15% nitro fuel and got 14,760 rpm. Really nice, steady howl. It's a relatively narrow blade so that must affect it, but it was still more than I expected. Lots of power for my World Models LA 40 Racer!

Jim

AMB

BUZZARD BAITIS THIS THE UK OR OS VERSION ? thinking about having a diesel head made up fro mine ( UK) made martin

buzzard bait

Mine is the UK one.

Go to the diesel forum if you haven't already. It's got a big carb and a lot of porting.

Jim

Oh, I just realized, you know diesels very well as I recall.

Stoneweapon

I got a bad rear bearing as well. It is the same small bearing as used in the Super Tigre G34.
For the Irvine .39 I would not recommend high rpm applications. 3D Funfly with less than 13000 rpm fits this Engine better.

nicohaas

I agree with that.

1QwkSport2.5r

For high rpm usage, you should use bearings with phenolic ball retainers.

buzzard bait

Hmm, I like mine on the APC 10.5x4.5, but maybe I should use a bit more load. Or just take the risk...it really sings on this prop.

Stoneweapon

The ball retainer is 1 piece and made of plastic. I don't know if it is a special "phenolic" material. My personal opinion is that the bearing is just too small to withstand rpm of estimated more than 15000 for a long time in this engine with it's relatively large displacement. This thin types of bearings have a lower limit rpm compared to standard bearings with the same outer diameter e.g. 25000 to 35000.
I added a picture of the Irvine .39 rear bearing (right side) together with a 61902 bearing which is used for normal 40-sized engines from almost all manufacturers (ST G40, OS 46FX, 50SX, China, Taiwan...)
We pay the price for a super lightweight and powerful engine by extra stress on tiny components.

@buzzard bait
You can run the engine as you like but from the experiences we share here you are aware of this problem and you may have extra attention to symptoms that come from the bearings.
If there is bearing noise or roughness I always check the bearings in my engines. Operating them with this symptoms may lead to more damage than just pitting on the bearing surfaces.

buzzard bait

Thanks much, that's a pretty dramatic comparison. Maybe I'll go with a little bigger prop and scale down the rpms a bit. Sorry you got burned on yours.

Jim

electrev

Why is it so IDIOTIC to register for this site ??? Email is NOT required for registration, no red asterisk. But when you press the button, it won't allow you to register unless you give an email ??? Needs checking out.

Also, when you browse, then log in, there is la ink to go back to the page you were browsing. But when you browse then register, no such link. Why would that minor bit of inconvenience be there ???

electrev

I had an Irvine 39 many years ago. I recently acquired another. The compression didn't feel "quite right", it was good, but not the way I remembered it. So I bought Just Engines' LAST Irvine 39 piston and liner, fitted it, and ran the engine in *.
I now have it in a Limbo Dancer 3D (I've added SFGs etc to a standard LD). I started off with a 12,25 X 3,75 APC, that really killed it ! Then I tried an 11 X 4 APC, better...but now I've got a 10 X 4 APC and I get 14,400 RPM. Sounds right too. I'm using Model Technics Contest 10 fuel and standard pipe. I'm still sorting out the bottom end, and it

*may not be fully run in yet, only had 6 or 7 tanks through it.

It flies the LD well, bags of top speed, too much for a funfly! But it doesn't prop hang very well. When I hold the model vertical on full throttle and let go for a split second (do NOT try this at home), it goes up SLOWLY, but not a patch on my electric 3ds, or my High 5 (similar size to LD) with a West 52 T1 and Genesis pipe.

I'm thinking that while the Irvine 39 IS still a pocket rocket, and I love it, to get the kind of power to weght ratio to which I have now become accustomed, I either need a bigger engine or a smaller lighter model.

Any thoughts ? Suggestions ?

electrev

Here's a point...I've only ever seen "made in England" Irvine 39s. Does anyone know if these were ever actually made in Japan by OS ? I'm just curious about this, thanks.

Stoneweapon

I use mine on a Magic 3D Funflyer with the APC 12,25x3,75 and it seems the right prop for the engine in this application.
What do you exactly mean wit "really killed it"?

electrev

The main way I judge it is the vertical test, pull-up from a hover, weather willing, or the "hold it up vertical and momentarily let go" method if it's too windy to hover. I'm not interested in how much noise it makes, top speed or anything else like that. Whed I tried vertical with the 12,25 it could hardly support it's own weight, let alone the "Ferrari" vertical acceleration I'm looking for. Under this test, the 10 X 4 APC was the best, albeit less than ideal.
A couple of points, I know that what I am expecting may be unreasonable: comparing it with my electric 3Ds (eg Lil' Banchee 3D by Cermark) weigh NOTHING, and a similar size funfly to the LD with the West 52, which is like a formula 1 engine ! These have an incredible P to W ratio, but that's what I've got used to.
I also read somewhere that these engines do take a LOT of running in, so maybe I must "chill" and be a bit patient.
All I know is that at this moment the Irv 39 does not give me the vertical performance I crave in a 3D model.
When you say "it seems right", what throttle setting does it hover at ? And if you then open the throttle fully, how quick does it accelerate vertically ? With my other models, I hover at most 1/4 throttle, and when I open up, it goes straight up, no lag, and unlimited vertical. Am I expecting too much from the Irv 39 ? Should I be more patient and run it in properly ? Thanks

Stoneweapon

The vertical performance is very good. Hoovering at about 1/2 Throttle. The engine can be throttled like an electric motor. My exhaust system is a Stueckerjuergen 3D muffler for 50 sized engines but I think the maximum Output is about the same as the stock muffler.

Fuel: 20% Castor 5& Nitro.
With 10% Nitro it even turns the APC 13x4W without sputtering but the acceleration of the prop is too slow to go out of critical situations fast enough.