Aeromaniacs Isobaric " Bush-O-Lator "

If you haven't tried one of these things, you should! I now use them on all my tanks that are not uniflow or pressurized. It would probably work well to pressurize by connecting your pressure line to the "Bush- O- Lator" "tee". You can try it many different ways, by pointing the "tee" in different directions ( up, down, forward, sideways, etc. ). You can also cure your Norvel fuel feed problems by converting to uniflow per instructions from the Aeromaniacs web site.
Go to the tips section to look at these things. I am sure you have all gone to this site many times, but it it is always worth another look --- these guys have some good, cheap ideas, and I like cheap. Why heck, Cheap is my middle name.

www.aeromaniacs.com

Looks to me like an excellent solution--assuming it works as claimed, and I'm pretty sure the claims are valid--to some of the problems in using the stock tanks supplied in ARF Flite Streak "kits."

I might well be blowing smoke here, as I have not actually used the stock tanks in either of my ARF models, but have seen some less than ideal runs with the models of others. This little trick might well make those tanks work just fine, especially for sport flying.

I use the stock tank on my ARF Flightstreak and did not get a full run. There was some fuel left in the tank. Try it with muffler presure and without. I suspect that the fuel feed tube does not go all the way back to the end of the tank. Replaced it with an 2.5 oz. tank an it works fine.

Am I the only one that couldn't find any reference to what the heck you are talking about on the web site. I now know everything about how to build a platter but no Bush-O-Lator

No.

Howard (intensely curious about the Bush-O-Lator)Rush

You just need to click further into the site to the hints section. Ultimately this:

http://www.aeromaniacs.com/busholator.htm

SK

It took me a bit of searching to find it-
http://www.aeromaniacs.com/Tips.html

My first reaction was, as Buggs Bunney would say, "Wotta maroon." However, I was helping a friend get back into the hobby. He made up a uniflow just as I instructed him. Didn't run well for reasons unknown. He ended up with basically the same set-up with a tee to the muffler pressure line. Ran fine. Go figure!

I've looked at this site and am intrigued and mystified. When the fuel surges to the remote end of the tank as it empties surely you end up with a standard vented tank? In fact the set up looks like a standard vented tank with one air bleed instead of two. Great if it works, but why?
Adrian

LAST EDITED ON Dec-07-03 AT 01:20 PM (CST)
 
I agree, I don't see what the effect is suppose to be. If you would "simply" put two short pieces of fuel tubing on the two standard vents, and cut a 45 degree angle onto both of the exposed pieces (the cut facing forward into the wind), you would also get the effect of ram pressure. (see picture)

But even with ram pressure, the mixture will still lean out over the flight, maybe not as much (relatively speaking) without the ram pressure.

I use to do this when I was a kid. The only problem is that some fuel still syphons out, even with the 45 degree cut.

I guess I am surprised that you got siphoning, which I assume was at the beginning of the flight when the fuel level is still covering the end of the overflows. You could beat that by simply plugging one of the vents (instead of using two 45 degree cuts). Since you will be drawing air through the one vent left open, it can't also be siphoning.

What I have done in the past is to plug the bottom vent, and fill the tank by holding the plane with the nose down. When the tank is filled, fuel will begin to come out the venturi (since the nose is down, it just runs out and doesn't flood the engine). This has worked well with my Norvels.

I have noticed that most of the old plans I have with standard venting usually show the overflow vents pointing into the slipstream. Must be the same reason, to minimize the normal leaning that you get when the tank empties.

>I guess I am surprised that you got siphoning, which I
>assume was at the beginning of the flight when the fuel
>level is still covering the end of the overflows. You could
>beat that by simply plugging one of the vents (instead of
>using two 45 degree cuts). Since you will be drawing air
>through the one vent left open, it can't also be siphoning.
>
>What I have done in the past is to plug the bottom vent, and
>fill the tank by holding the plane with the nose down. When
>the tank is filled, fuel will begin to come out the venturi
>(since the nose is down, it just runs out and doesn't flood
>the engine). This has worked well with my Norvels.
>
>I have noticed that most of the old plans I have with
>standard venting usually show the overflow vents pointing
>into the slipstream. Must be the same reason, to minimize
>the normal leaning that you get when the tank empties.

Alan,

The one thing missing from the discussion, is that fuel is also *atomized* by the airstream flowing over the top vent which is always dipped in the fuel. This is just our friend Bernoulli reminding us that if we blow over the top vent tube, the increased velocity of the airflow lowers the pressure at that point and will tend to draw fuel up the vent and atomize it into the airflow. So you have the potential to lose a large fraction of the fuel load. The 45 degree tubing or pointing the vents into the flow prevents this. If you point the vent into the airflow, the flow will stall to zero speed at the vent inlet (like a pitot tube) and the pressure will remain constant and approximately equal to atmospheric at that point. The Bush-O-Lator accomplishes the same thing neatly for both vents, and should help stabilize the pressure within the tank throughout the run. The only differences in the fuel pressure head at the pickup tube will be due to the changing height of fuel in the tank and accelerations and changes in attitude due to maneuvers. The basic idea is a pretty good one, and I'm not surprised it results in smoother engine runs without siphoning or atomizing of the fuel. It's not exactly uniflow, which attempts to hold the pressure at the fuel inlet steady by connecting it to an approximately constant reference pressure, but it does establish a constant gas pressure within the tank above the fuel, which will certainly help.

Another $0.02...

But that is what I meant. The 45 degree fuel tubing cuts are my picture. I was claiming that they were equivalent to the "bush-o-lator".

I understood his (Aeromaniac) comments to be that even with the tubing cut at 45 degrees that he was getting siphoning.

Actually I suspect there may have been a bit of fuel foaming, which of course will push fuel out the vents too.

Thanks for the promo. Randy Bush, who is the current WAM Racing Director and an expert Sport Racer, came up with this idea a few years ago. I seems to work well on his Sport Racer. The name Bush-O-Lator was kind of a joke, but it seem to have spread around by the C/L community pretty well.

On the Norvel engines, our club did a lot of testing with these engine. In fact everyone in our club has at least one Norvel engine, so it very easy to see what happened when trying different tank configuration.

Heman Lee
Alameda Aer-O-Nut Model Airplane Club

What's the diff between Bush-OH and sticking tubing bits on intake and overflow with a 45 degree cut facing into the breeze. Or what about capping the overflow and running muffler pressure to the fill line. Saves a hunt for a t-connector at the pet shop.

I vote CHICKEN HOPPER with or without muffler pressure. Unfortunately don't make them in miniature for 1/2A. Even too big for my Enya 19s.

I'm looking at a set of plans for the 1/2A Snapper. Designed by Geo. Millikin in 1954. It shows two different engines. One, an Atwood, the other is a Cox Baby Bee. It shows the Baby Bee with a notched tube connecting the two top mounted fuel inlets. This is very similar to what this thread is talking about.

On this plane, the tubeing mod. allows the Baby Bee to be flown inverted. I quick and dirty solution that I wished I'd known about back when I was a kid flying that Scientific All American Boy.

I'm wondering why everything is spinning around?

It's an idea, but HOW does it work?

Both vents are seeing one atmosphere (maybe a tiny bit more due to ram air effects), just like on a stock tank with no tubing connecting them..

Someone explain to me what the difference is, and if it only ram air effects, wouldn't just pointing both vents into the airstream be completely equivalent?

Throwing rocks out of a boat in a swimming pool made perfect sense to me, but this does not..

[photo not recovered: 3e69bb3870f12ad5.jpg]

"Don't MAKE me come down there" - God

>Someone explain to me what the difference is, and if it only
>ram air effects, wouldn't just pointing both vents into the
>airstream be completely equivalent?

Yes, provided the airflow at both vents were *exactly* the same, which it never is. So for sure this setup ensures that the pressure at both vents is *exactly* the same, which is good. You don't want any pressure difference between the vents.

LAST EDITED ON Dec-08-03 AT 01:23 PM (CST)
 
"Exactly" the same is always relative. Nominally the bottom vent is out of the fuel almost immediately when you start the engine. So the slight difference would have to pump the fuel out the top (~1/2 inch?).
As I said up in another post, I bet foaming is the larger effect.
I think simply capping off the lower vent and leaving the 45 degree cut on the top vent is equivalent. After the first few laps, both vents are out of the fuel.

So the way it "works", is that the ram pressure lessens the rising fuel head over the flight.

>I think simply capping off the lower vent and leaving the 45
>degree cut on the top vent is equivalent. After the first
>few laps, both vents are out of the fuel.
>

Alan,

Not so. On all the wedge tanks I am familiar with, the top vent runs nearly to the bottom of the tank, the bottom vent nearly to the top. Otherwise fuel can run out of the top vent during inverted flight. The top vent is dipped into the fuel until the fuel is nearly exhausted. So the top vent behaves sort of like a uniflow vent (dipped in the fuel) but it is not near the pickup point. In inverted flight the top and bottom vents interchange roles.