Author Topic: Brodak 40 Problem (Read 7461 times)

Motorman · « **on:** November 08, 2016, 02:16:22 PM »

Set up: Brodak 40 stock (newest version) factory muffler, Merlin 2005 hot plug, 11-4 wood prop, 10% nitro, Brodak 4oz uniflow wedge tank 1/8" above center line. Dubro filter, good tubing, Profile Sig Banshee, 63' lines, oat 65f.

I had a 5oz tank on it that I made and I tried re plumbing a few times but got the same problem so, I got the Brodak tank and the problem is still there.

I set the needle on the ground so it's 4 stroking with just a wisp of 2 stroke now and then. It's basically running rich then, when it takes off, it goes lean in less than a lap almost full 2 stroke. So I'm wizzing around the pattern and when I get to the square eight it starts going rich almost a full 4 stroke then it gets richer from there. I can still finish the pattern, in fact when it's running full 4 stroke it's much nicer to fly but, at the start of the flight it's a rocket ship.

I've tried allot of needle settings and it still goes lean to rich throughout the flight only leaner or richer overall depending on the needle. I tried higher pitch props but they make the plane too fast. I had an old K&B 1-L plug in there and had it set so rich on the ground it was almost cutting off and it still went too fast after launch.

I've never had a tank that goes from lean to rich through the flight but somehow I don't think it's a tank problem. Maybe it needs head shims or a smaller venturi?

MM

Brent Williams · « **Reply #1 on:** November 08, 2016, 03:24:47 PM »

Dirt in the needle valve/spraybar?

My LA46 was doing that last weekend and it cured the issue when I cleaned it out.

Chris Belcher · « **Reply #2 on:** November 08, 2016, 03:30:11 PM »

loose back plate screws that are "sealing up" when it gets hot causing it to go rich cuz it stops sucking air???

Motorman · « **Reply #3 on:** November 08, 2016, 04:51:53 PM »

I clean the fuel system after every session. It's a very consistent problem, doesn't act like dirt in the needle.

The screws aren't loose.

Could the tank be too wide? It's something the two tanks have in common.

MM

Mark Scarborough · « **Reply #4 on:** November 08, 2016, 05:00:41 PM »

could be unloading , what prop is it,, ( i know you said wood, but what brand)

also, are you SURE its going rich at the end f the flight? if it were getting hot it could slow down too

I dont know that I would rule out a tank problem

Motorman · « **Reply #5 on:** November 08, 2016, 05:42:42 PM »

Hawk (A type) 11-4 beachwood prop. It's definitely going from lean to rich.

MM

Steve Helmick · « **Reply #6 on:** November 09, 2016, 04:31:10 PM »

Can you post a picture of the engine setup? What's the oil content in the fuel? Also, there was a discussion at last night's club meeting about a problem with Brodak .40's. Seems some of the muffler mounting screws are too long and when screwed in all the way, they bottom out and distort the cylinder. Might be something to take a look at, anyway.

Steve

Motorman · « **Reply #7 on:** November 09, 2016, 08:10:19 PM »

The muffler bolts are ok on this one. The oil is 10% Klotz original techniplate and 10% castor, I mix my own.

John Tate · « **Reply #8 on:** November 09, 2016, 09:27:36 PM »

Add a head gasket. I noticed that each production had different combustion chamber shapes. Some of them have too much compression for a 2 - 4 break. Wish you luck.

Clint Ormosen · « **Reply #9 on:** November 10, 2016, 04:01:34 AM »

You need to up your total oil content to 22-23% and try a Thunderbolt idle bar plug. Then get rid of that tank and use one of the 1" tall uniflow types. Looks like you have room for it, but you'll have to move the tank mounting holes to over/under the tank instead of on the ends. Or, a plastic klunk set up for uniflow might work, too.
I wouldn't mess with head shims just yet.

C.T. Schaefer · « **Reply #10 on:** November 10, 2016, 06:32:04 AM »

My experience so far. Brodak on a Twister. Sullivan clunk uniflow 4oz. Takes off just right but about halfway through the pattern it starts to run leaner. Not dramatically but enough to be annoying. Tried all the usual and finally put the motor in my pal's well proven Nobler. Boom! Perfect run. Conclusion. Keep working on the tank!
These things keep us busy TS

Balsa Butcher · « **Reply #11 on:** November 10, 2016, 09:24:02 AM »

My 2 cents worth based on recent experience: I noticed you have the latest version of the muffler. It has a HUGE (.38" approx.) outlet. When I used that muffler my B-40 acted in a similar fashion. It wanted to run flat out. Good for racing, not so good for stunt where back pressure can be a good thing. I sleeved it down to .32" (approx.) by putting a brass tube insert w/ JB Weld. Ran more consistent, no more going lean, still plenty of power. The previous run of mufflers had an outlet approx. this smaller size. They could be substituted for the one with the larger outlet if one is available.

As far as the tendency to slowly go lean throughout the run as stated above: I've found it goes away as the engine gets some run time on it. Until then adding a couple of ounces of castor oil to your 10x22 blend will help stabilize the run. Best prop for this engine is still the Bolly Clubman 10.5 x 5, are you reading this Steve Wilks?... hint, hint. Disclaimer...your mileage may vary.

Motorman · « **Reply #12 on:** November 10, 2016, 10:50:12 AM »

Both of my tanks were 2-1/4" wide. I think when it takes off there's allot of pressure against the vent tube inside and as the tank empties the pressure gets less and it goes richer. Of course that same pressure is against the feed tube so, I don't know. Anyway, I took my 5 oz tank and made it a 4 oz tank by cutting some off the width. Now it's 1-3/4" wide and I'll see what that does today. I also have a Brodak 1" tall 4oz uniflow to try after this.

Thanks for the numbers on the muffler. I'll start playing with the engine after I've run out of tanks.

MM

Brad LaPointe · « **Reply #13 on:** November 10, 2016, 02:19:07 PM »

Try a rubber muffler extension , they will cause a bit of a restriction and help keep the model clean .

Brad

Mark Scarborough · « **Reply #14 on:** November 10, 2016, 02:48:17 PM »

Quote from: Motorman on November 10, 2016, 10:50:12 AM

Both of my tanks were 2-1/4" wide. I think when it takes off there's allot of pressure against the vent tube inside and as the tank empties the pressure gets less and it goes richer. Of course that same pressure is against the feed tube so, I don't know. Anyway, I took my 5 oz tank and made it a 4 oz tank by cutting some off the width. Now it's 1-3/4" wide and I'll see what that does today. I also have a Brodak 1" tall 4oz uniflow to try after this.

If this is uniflow, then this statement is False,,

and if in deed the pressure decreases in the tank( uniflow will not do this) then the engine will go LEANER not richer, because the fuel is not being pushed to the needle as readily..

when you talk width, are you talking width when looking at it from above or height,,

EddyR · « **Reply #15 on:** November 10, 2016, 04:11:52 PM »

What is the open vent in the top front outside corner?
Ed

Mark Scarborough · « **Reply #16 on:** November 10, 2016, 05:58:00 PM »

Quote from: EddyR on November 10, 2016, 04:11:52 PM

What is the open vent in the top front outside corner?
Ed

Good point, it looks as though the overflow is now open to oncoming air, and the uniflow( with the tube on it?) is vented,, something is not right there,,

Dan McEntee · « **Reply #17 on:** November 10, 2016, 06:11:29 PM »

Quote from: Motorman on November 09, 2016, 08:10:19 PM

The muffler bolts are ok on this one. The oil is 10% Klotz original techniplate and 10% castor, I mix my own.

Looks to me like you took a good tank and ruined it. That big tube sticking up about the tank acting like a tuning fork is probably the uniflow? And the tube sticking out the side with the yellow fuel line on it, is that the over flow? If so it should be plugged for uniflow operation. That poor tank just doesn't know what it's supposed to do!
Type at you later,
Dan McEntee

Motorman · « **Reply #18 on:** November 10, 2016, 06:16:16 PM »

That is a piece of fuel tubing with a 1/8" dowel pin in it to plug the over flow that goes to the top front inboard corner. It looks funny but it's real easy to reach. All tanks are uniflow with just one vent.

Mark Scarborough · « **Reply #19 on:** November 10, 2016, 06:23:19 PM »

so then what is the relationship bnetween the fuel pickup and the uniflow inside the tank?
is this a tank you built?

pmackenzie · « **Reply #20 on:** November 10, 2016, 07:31:25 PM »

I would try armour-all in the fuel.
Had a similar issue in my old Fox powered Gieseke Nobler,ran a bit fast early in the flight then would settle down.
Preventing the fuel from foaming solved it.

Steve Hines · « **Reply #21 on:** November 10, 2016, 08:07:03 PM »

We had the same problem with my brother b40 last weekend, the same thing g this spring. Both time temp in the 60s, it was fine all summer. We should have tried 5%, could be it just not broke in. We did the tank thing, tubing, plug, prop. It just needed the temp to go up and it ran great with out changing anything, and nothing g was changed last Sunday.

Motorman · « **Reply #22 on:** November 14, 2016, 11:11:30 AM »

I took everyone's advise and put it all together. Brodak 1" tall tank, Bolly Clubman 11-5, made an insert for the exhaust .370", made a smaller venturi .281", got some Byron 10% fuel with 16% synthetic and added 11oz of castor to make 9/22. It's working good now, put in about 12 flights Saturday. I might even finish painting the nose.

Scott B. Riese · « **Reply #23 on:** November 26, 2016, 08:30:49 PM »

Quote from: Steve Hines on November 10, 2016, 08:07:03 PM

We had the same problem with my brother b40 last weekend, the same thing g this spring. Both time temp in the 60s, it was fine all summer. We should have tried 5%, could be it just not broke in. We did the tank thing, tubing, plug, prop. It just needed the temp to go up and it ran great with out changing anything, and nothing g was changed last Sun

Tank needs to be at least 3/16th or more above the center of the engine or glowplug. Also add a .010 Head gasket. Run a 11.5x5 Prop. YOU may have some fun.

Phil Spillman · « **Reply #24 on:** December 02, 2016, 08:09:38 PM »

If with this configuration you're still not perfectly satisfied, You may try raising the tank just a bit. It looks to me as if the tank is almost even with the venturi's center! Just a thought!

Phil Spillman

Motorman · « **Reply #25 on:** December 06, 2016, 06:29:02 AM »

It's camera angle but it's 1/8" higher than center. It does run just slightly richer inverted but only noticeable on cold days. I'll have to do something with the washers on top to get it any higher.

How do you set up for 45F temps? I had to lean it down to keep it from flaming out and now it goes too fast. Is it just hotter plug or should I raise the compression or something?

Thanks,
MM

Lauri Malila · « **Reply #26 on:** December 06, 2016, 06:59:31 AM »

If cold running is the problem, why don't you just raise the running temperature? You can play with big O-rings between cooling fins, or make a balsa/ plywood shield like Mike Nelson did. Or use scotch or heat shrink for example. L

Steve Helmick · « **Reply #27 on:** December 06, 2016, 06:31:10 PM »

Try adding 2%-4% Coleman Stove & Lantern fuel to a pint of your glow fuel. It should help it stay lit in cold weather and also will increase the fuel economy. If you don't, watch your run time, because it may be quite a bit shorter than expected. It'll help starting, also. A squeeze bottle with some Naptha will also be good for priming in cold weather. Add 20% Klotz to the Naptha if you want to be kind to your engine. I assume Klotz will mix ok with Naptha, but I haven't tried to. I'm having crazy thoughts about running glow engines on a mix of Klotz, Naptha and Coleman fuel. KaBoom!

Steve

cory colquhoun · « **Reply #28 on:** January 21, 2017, 10:21:10 PM »

Quote from: Motorman on November 08, 2016, 02:16:22 PM

Set up: Brodak 40 stock (newest version) factory muffler, Merlin 2005 hot plug, 11-4 wood prop, 10% nitro, Brodak 4oz uniflow wedge tank 1/8" above center line. Dubro filter, good tubing, Profile Sig Banshee, 63' lines, oat 65f.

I had a 5oz tank on it that I made and I tried re plumbing a few times but got the same problem so, I got the Brodak tank and the problem is still there.

I set the needle on the ground so it's 4 stroking with just a wisp of 2 stroke now and then. It's basically running rich then, when it takes off, it goes lean in less than a lap almost full 2 stroke. So I'm wizzing around the pattern and when I get to the square eight it starts going rich almost a full 4 stroke then it gets richer from there. I can still finish the pattern, in fact when it's running full 4 stroke it's much nicer to fly but, at the start of the flight it's a rocket ship.

I've tried allot of needle settings and it still goes lean to rich throughout the flight only leaner or richer overall depending on the needle. I tried higher pitch props but they make the plane too fast. I had an old K&B 1-L plug in there and had it set so rich on the ground it was almost cutting off and it still went too fast after launch.

I've never had a tank that goes from lean to rich through the flight but somehow I don't think it's a tank problem. Maybe it needs head shims or a smaller venturi?

MM

probably a bit inexperienced to be commenting ,but had one of my engines doing similar things,turns out tank had very tiny pin hole.that small it didnt leak fuel, the only way i found it was to submerse in a bucket of water and saw tiniest of bubbles coming from outlet tube where its soldered to tank soldered it up works fine