rrragmanliam

My Feedback: (1)

I 've recently pruchased a bunch of cox engines. Several .049td's, several .049 reed valve, (collecting parts to build a couple of the famous Dickie Bird engines). A .074 r/c Queen Bee, and a .09 medalion. The .049 motors are broken in, The .074 and .09 are new. I was looking for:

A. Propeller recomendations for flight on all engines, (and break in on the .074 an .09)
B. And fuel recomendations. I'm thinking 20-25% nitro 18-20% castor.

If it matters the .074 has a throttled carb at the rear of the motor, and the .09 has a exhaust throttle sleeve.
Any and all help is appreciated.

Thank you,

Darren

ajcoholic

My Feedback: (10)

Darren, your fuel is bang on, and even a bit more oil content cannot hurt, but not run lean I have found 18% fine for sport flying ,where the NV is set on the rich side. Can allways add a bit to the fuel to bring it up to 22 to 24% though to be safe, especially if you are setting for maximum power and risk a lean run.

The 074 Queen Bee likes the Cox 7.5-4 prop, anything from a 7-3 to an 8-4 would work. The 09 I would run a 7-4 personally.


AJC

rrragmanliam

My Feedback: (1)

Thanks AJ, Your responces to my post's are always full of valuable information. I noticed you didn't suggest a larger propeller for the .09 than the .074. Was there any paticular reason for this?

thanks again
Darren

BMatthews

The 09 likes to spin a bit higher. I used to run an Enya 09 on an 8x4 and it seemed fine but when I think back on it a 7x4 probably would have been better. To put it in perspective 15's use a 7x6 for speedier flying and an 8x4 or 7x4 for free flight power duration. So the 7x4 for an 09 IS a sport size.

The Nelson 15's in the last few years before the reduction units became popular for FAI free flight power used a folding 7x2.5 and other slight variations on that size and pitch give or take a 1/2 inch. Of course those engines were turning up to around 28 to 30,000 rpm.

Jim Thomerson

I've flown TD 09's a lot on small CL stunt airplanes. They run fine on 10% nitro, 20% 50:50 oil Sig Champion fuel. Actually I like that fuel better than 25% nitro for them. The best prop is the Cox grey 7 x 3.5 for my purposes. An APC 7 x 3 should be fine. I turn them loose at around 15,000, which is not screaming for a TD 09. I have an ebay Medallion 09, only run on the bench, same fuel and prop, turns around 13,000. Your Medallion won't need much break-in. just don't run it lean for the first few runs. It will improve a little over the first 30 minutes of flying. Do get reset tools and keep the ball and socket joint in the piston tight on all the Cox engines which don't have a piston pin.

Jim

ajcoholic

My Feedback: (10)

Maybe it has to do with rotary intake engine's timing and such, but I, like BM think the 09 likes to turn up a bit. The reed valve queen bee can lug the same prop or larger.

AJC