Re: Brodak 40 Mystery

Thank you for your feed back

I am using a standard toung muffler with pressure, Bob Hunt helped me set up the correct amount of holes to plug. It has a uniflow 4.5 ounce tank and an RSM 10-6 Proppeller, i am still using the same galon of Excalibur fuel that i have been running for quite a while.

I had also thought it would be the tank but i cleaned it out and pressurized it, all was fine. All of the fuel lines were replaced with new ones along with a new crap trap filter.


Michael Duffy
250-403-0927

>Thank you for your feed back
>
>I am using a standard toung muffler with pressure, Bob Hunt
>helped me set up the correct amount of holes to plug. It has a
>uniflow 4.5 ounce tank and an RSM 10-6 Proppeller, i am still
>using the same galon of Excalibur fuel that i have been
>running for quite a while.
>
>I had also thought it would be the tank but i cleaned it out
>and pressurized it, all was fine. All of the fuel lines were
>replaced with new ones along with a new crap trap filter.
>
>
>Michael Duffy
>250-403-0927
>
>

Michael,
The first thing I would check is the pressure line from the muffler to the tank, especially the pressure fitting on the muffler.
Remove the line and check the pressure fitting by poking a wire into the hole in the fitting. I've had these clog up in the past on tongue mufflers. Drove me crazy the first time.
Second to that I'd make sure there are absolutely no leaks in the fuel system, to include the fuel lines and the tank itself. A uniflo system will not tolerate leaks as you know, but sometimes muffler pressure can mask the effect of this and cause lean runs.
Next to that check all the engine bolts and make sure everything is snug - head bolts, back plate bolts, etc....
I'm betting on the pressure fitting however.
See you at the field this weekend!

Randy C

Michael,
I'm a little confused. Did this problem just start after you added muffler pressure to the engine?
If that is the case, the problem may be one of the muffler actually producing suction (a generally negative pressure) at the pressure fitting. This can happen on tongue mufflers if the pressure fitting is located in an area of high velocity exhaust gasses. Gas flow across an orifice (at 90 degrees) will actually produce a suction in the orifice (pressure line in this case. This has happened in certain cases with pressurized tongue mufflers in the past.
Just disconnect the pressure line and see what happens. If this is the case we can fix it by relocating the pressure tap.

Randy C

Randy, read Michael's original thread on Brodak .40 mystery.

>Randy, read Michael's original thread on Brodak .40 mystery.
>
>

Matt,
I've read it very carefully but the answer to these questions are not there.
There is a lot of reasonable advice there but nothing concerning the items I've mentioned.

Randy C

Hi Michael - Crap trap filters leak after a while. Try replacing it with one that screws together. Tom H.

Hi Michael,
Call RJ.
Unplug or plug more muffler holes, relocate the pressure fitting and shrink wrap a new crap trap to keep it from leaking and replace the other. Check all fuel lines. You know how small things matter, and although Bobby Hunt got you in the ballpark, you may need additional trimming of the engines backpressure and pressure fitting location.

For instance, the two Aero Tiger 36's on Rick Loomis's Two Bits ran perfectly at VSC during their contest time after Bob trimmed the backpressure and props. Rick came back to SoCal, 2500 feet lower elevation, and it wouldn't run a whole flight without one engine quitting. After retrimming the muffler backpressure the engines run great.

Bobby got you "into the ballpark", working from there will probably get you the rest of the way. Randy has a good idea about the pressure fitting location, this happens a lot and is not standard from one engine to another.

Congratulations on your VSC performance.
Chris...

Hi Michael,
I don't have much to help you out, but, as you may know, to gain more mileage (at the same time losing some power) we plug or use smaller venturi openings. You migh check to see if some kind of debris has gotten into the venturi, a bug or rock. Something like that would probably show up with a different needle setting than you are used to. Just scratching my head.....dale gleason

The direction the hole in the spraybar is pointing? I can't see how that would do anything, but something to check....dg

Michael,
Has the mystery been solved? Have you been able to get it to run well yet?
Thanks,
dale g

Michael, yes I am an old crotchety old man and say things I shouldn't. But, where you are with all the local help why do you post here? I too had problems with overruns. The first was too much fuel(not enough practice at the site). The second was not getting started within a minute even tho I did take out 1/2 ounce of fuel. That was in Classic after the Humbug was done in.

In old time both flights were over runs and it runs almost perfect here at home. I even drained off fuel second round also. I just hope RJ, BH and MK will still talk to you.
DOC Hollida

I too was at VSC and had a very long over run on my ST .51 on my first judged flight. The day before I did a practice flight and had no power, so I turned in the needle to get the power needed and forgot to take out some fuel when I did the first real flight.

I do believe it is the thin air. My ST .51 did the entire OTS pattern on 2.5oz of 10x11x11 Excallebur fuel and the entire PAMPA pattern on 3ozs. No lie. I fly at sea level and it is always a supprise what going up 3000 feet will do to motor runs.
An dy

Hi Mike,
I understand you flew John`s Eagle. So how did you like it?

Gordy