stunthanger.com
Engine basics => Engine set up tips => Topic started by: Bootlegger on April 18, 2009, 09:41:45 AM
-
I'm not gettin very good gas milage on my Brodak 40, runnin 5% nitro, 22% oil, 1/2 castor 1/2 syn T/bolt idle bar plug and a 10x5 apc prop at 9500 rpm and about 5 1/2 min run time added a .014 head shim, no help, this mornin added another .010 shim will try that later today..
Any suggestions ??? Thanks, Gil
-
Hey, Gil. How much runtime does your B40 have? Mine started running easily after about 40 minutes on the test stand, so I put it in a Cardinal. a couple of months later, after about 3 flights one day, I had to turn the needle in almost 2 full turns to regain takeoff rpm. Following that, runtime went from 4:45 to 6:00 in one flight, and I didn't have to touch the needle again for almost 5 months!
Apparently, the engine did the final bit of breakin during that 3rd flight that day. But this was following an additional 3 hours of runtime in the air. Perhaps your B40 isn't quite run in yet ? ? ?
-
By all reports, the stock venturi of the B.40 is typically .305", which is bigger than many used on ST .60's. It might work well at high altitude or high heat, but generally, it's too big by about .030". You can "adjust it" by putting on a Bruline fine (green filter element) air filter or a few layers of pantyhose material. H^^ Steve
PS: Don't fail to try the Thunder Tiger Cyclone 11 x 4.5 prop. It's "da bomb" on the B.40.
-
I'm not gettin very good gas milage on my Brodak 40, runnin 5% nitro, 22% oil, 1/2 castor 1/2 syn T/bolt idle bar plug and a 10x5 apc prop at 9500 rpm and about 5 1/2 min run time added a .014 head shim, no help, this mornin added another .010 shim will try that later today..
Any suggestions ??? Thanks, Gil
Hey Gil:
How much fuel is it using for the 5.5 min run time. I get the pattern in no sweat on my B40/ARF Nobler. Engine is stock. It has a 4oz plastic tank, using 10% Sig Champion.
-
My 2 B-40s came with .310 venturis.
I ordered 2 .275s from Jim Lee. $8.00 each.
-
Guy's I thank all ya'll for your answers, Ralph I have about 2-2 1/2 hrs on the engine, and I'm usin a 4 oz clunk tank on an ARF Nobler that was "nekked" when I got it so I doped it and it tips the scales at 42 oz, I am gonna try the prop's that ya'll recommend ... Again thanks for the answers... #^
-
Unless you live above 2,500' (ie: Tucson) plan on B-40 using about 4 1/2 ounces for a 6 minute or so run. That's just the way it is. Ditto on the Thunder Tiger prop. Another good prop is the APC 10.5 x 4.5. 8)
-
Hi Guys,
I just did a test flight on a new(broke in by the instructions) B-40 using an APC 10/4 and the early small outlet muffler,10/22 fuel and the .305 venturi.The launch RPM was about 10,900/11,100. What a difference this made!! The 48 oz. ARF G. Nobler pulled like a horse and used only about 4 oz. of fuel.It was very windy & turbulent,so I didn't do many tricks.The lap times were about 4.5 seconds,so I'm going to try some longer lines next weekend and see what happens.This engine will cycle back and forth between a 4 cycle and 2 cycle like a pipe motor.You will never hear a B-40 sound like this.It runs in a dead 4 stroke and breaks quickly into a 2 stroke when loaded and back to a 4 stroke very quickly.
I got the idea from a fellow at VSC who flew a 52 oz. Tempest like this using about 11,200 launch RPM.Very impressive!!
-
Hi Guys,
I just did a test flight on a new(broke in by the instructions) B-40 using an APC 10/4 and the early small outlet muffler,10/22 fuel and the .305 venturi.The launch RPM was about 10,900/11,100. What a difference this made!! The 48 oz. ARF G. Nobler pulled like a horse and used only about 4 oz. of fuel.It was very windy & turbulent,so I didn't do many tricks.The lap times were about 4.5 seconds,so I'm going to try some longer lines next weekend and see what happens.This engine will cycle back and forth between a 4 cycle and 2 cycle like a pipe motor.You will never hear a B-40 sound like this.It runs in a dead 4 stroke and breaks quickly into a 2 stroke when loaded and back to a 4 stroke very quickly.
I got the idea from a fellow at VSC who flew a 52 oz. Tempest like this using about 11,200 launch RPM.Very impressive!!
Not to say you are wrong, but my 2 Brodak 40's ran exactly that way--deep 4 stroking breaking into a 2 stroke only at the top of the loops (or the verticals). One was in a Nobler (40oz) , the other a Brodak P40 (about 48oz).
-
Hi Guys,
I just did a test flight on a new(broke in by the instructions) B-40 using an APC 10/4 and the early small outlet muffler,10/22 fuel and the .305 venturi.The launch RPM was about 10,900/11,100. What a difference this made!! The 48 oz. ARF G. Nobler pulled like a horse and used only about 4 oz. of fuel.It was very windy & turbulent,so I didn't do many tricks.The lap times were about 4.5 seconds,so I'm going to try some longer lines next weekend and see what happens.This engine will cycle back and forth between a 4 cycle and 2 cycle like a pipe motor.You will never hear a B-40 sound like this.It runs in a dead 4 stroke and breaks quickly into a 2 stroke when loaded and back to a 4 stroke very quickly.
I got the idea from a fellow at VSC who flew a 52 oz. Tempest like this using about 11,200 launch RPM.Very impressive!!
That fellow at VSC was Jeff Welliver. Interesting approach to a setup, I must say. I recall that Jeff used the small outlet muffler (early issue), and seemed to think it was an important part of the package. My applause for following the setup so thoroughly, Rod. I could even provide an entire early Brodak .40 with small outlet muffler, all NIB, for anybody interested. Contact me if interested! #^ Steve
-
I recently changed a muffler from the stock OS to a tongue muffler and couldn't get enough time out of a tank either. Way short, so I started plugging holes in the muffler untill I thought I was close to the factory exhaust port on the muffler removed... The run time came right back. The small exhaust port is an important factor in fuel usuage just like the venturi.
Glad you got it fixed.
-
Remember, a lot of old RC engines used an exhaust restrictor as a throttle. I have a Norvel 061 in a little "bounce-able" heli (LiteMachines), and it uses an adjustable exhaust restrictor for a quite effective throttle. I think Cox had something similar too.
-
Most B-40's seem to use 4 1/2 ounces of fuel until they are well broken in.......then they become a little more economical.....
Let it run the way it is intended...
-
HI All, Back i 2006 I learned that for my B-40's a home made restricter to .270" was just right for my runs and power for my ARF Nobler! Since then this same restriction continues to work quite well for me and my planes! I used telescoping pieces of brass tubing to reach this dimension.
Best of settings to all!
Phil Spillman
-
HI All, Back i 2006 I learned that for my B-40's a home made restricter to .270" was just right for my runs and power for my ARF Nobler! Since then this same restriction continues to work quite well for me and my planes! I used telescoping pieces of brass tubing to reach this dimension.
Phil Spillman
What are you restricting, venturi or exhaust outlet ?
-
My Brodak B-40 is going into it's third airplane. It is box stock except for the Adimisin Tongue Muffler I got from Brodak. The Muffler is permanently attached now after the demise of the Olympic. I run 4.25 ounces of fuel to get thru the pattern with about 10 extra laps when the needle is set right. I run 10% nitro fuel, Sig, Power Master and Excaliber brands. I have seen very little difference in the fuel. The prop is Top Flite Power Point 10-4. Don't know rpm, but, try for 5 to 5.2 second laps. I also fly on .015 cable 60 foot center of plane to center of handle.
But, it takes a lot longer to break in the B-40 than the instructions say. Have fun, DOC Holliday
-
Mornin Guy's Sure do thank all ya'll for the answers, put a .272 venturi in it this mornin and plan to see what it'll do for fuel milage now.. Again thanks for all the input.. n~
-
Hey, Gil. How much runtime does your B40 have? Mine started running easily after about 40 minutes on the test stand, so I put it in a Cardinal. a couple of months later, after about 3 flights one day, I had to turn the needle in almost 2 full turns to regain takeoff rpm. Following that, runtime went from 4:45 to 6:00 in one flight, and I didn't have to touch the needle again for almost 5 months!
Apparently, the engine did the final bit of breakin during that 3rd flight that day. But this was following an additional 3 hours of runtime in the air. Perhaps your B40 isn't quite run in yet ? ? ?
Listen to the League City man. Here is the typical drill on getting a Brodak 40 right:
30 minutes or so bench time. Followed by lots of air time, adding shims, removing shims, changing mufflers, changing venturis, changing fuel, fiddle, fiddle, run, run. Pretty soon you will find the magic combination that works, so you tell all your friends you found the "answer".
Now, put everything back stock, and it will run even better. The cure for all B-40 ills is to run it some more! (This answer is pure prejudice, but it worked once for me, and once for Ralph)
Larry Fulwider
-
Good thread...shouldn't it be under the Engine Forum? S?P
-
My mistake........ H^^
-
No problem - just couldn't resist pointing it out. And FWIW I tried my B-40 with a .283 venturi. It didn't run as consistent, gained RPM throughout the flight. Lots of things it could be but I just went back to the stock venturi and kept it there. Just thought I'd let you know in case this happens to your engine when you downsize the venturi. It's worth a try though and easy enough to revert back to stock. 8)
-
There have been many subtel changes to this engine since its introduction! One of the most important has been the newer mufflers which have come through with much larger outlet holes than the initial ones. This may appear trivial but it is most significant as it allows the engine to breathe much easier! Take a look at the size of you muffler's outlet. The newer ones are about .367" in id. That's slightly less than 3/8".
As to preferred props, my B .40's like the newer 11 X 4 Pro Zingers and the 11 X 4 MAS. Of course balancing is highly suggested!
Phil Spillman