canardlover

Howdy, I´m currently contemplating my next build and thinking of feeding two glow engines sitting side by side from one central tank(see attachment). Never done that before so before I commence (into a dead end.?) I would like to pick your brains on how to set it up (or abandon it). Anyone tried it ? - if so please enlighten me..Thanks.! Tried several searches but found little...Cheers/

jaka

Hi!
It will work but...In a turn one engine will be above the tank which means the engine will go lean. The other engine will go rich! So...Why not use two separate tanks and you will avoid this problem?

rgburrill

If the higher engine goes lean in a turn it will also increase speed. Since it will be the outside engine so that is a good thing, right?

rgburrill

With that set up when one engine dies the other one will also die since the tank will have an open line to the air. Some systems I have seen use a large single tank in the center of the aircraft with two small tanks, one at each engine.

canardlover

Thanks guys for input. Provided the two engines are pretty close together (prop tips almost touching) going rich/going lean should not be worse than climbing/diving in a conventional airplane.
Yes, one engine "flaming out" means less tank pressure but with check valves in the pipe/muffler pressure lines I guess that can be alleviated..?!
I have mixed results with "hopper tanks" and that becomes even more complicated than having two tanks in the first place as jaka suggests(the KISS principle)

Rafael23cc

My Feedback: (6)

If you are going to install check valves in the pressure side of the fuel system, make sure that you also allow for a plugged vent to release the pressure when you land. I've got a similar pressurized system on my helicopters. I also have a pressure regulator at the carburetor inlet that takes care of the changes in pressure due to changes in attitude of the aircraft. That may also help you in feeding dual engines on a single tank.

Rafael

canardlover

Rafael, good point to release pressure after landing..! Could you please elaborate a bit on your pressure regulator, maybe with pics....thanks.!

Rafael23cc

My Feedback: (6)

Attached is a pic of the set-up in my helicopter. the line coming from the back of the crankcase can be seen coming out of the back of the engine and passing thru the one-way valve. From there I installed a "T" fitting and a clamp to release the pressure after landing. From there it goes to the fuel tank. Also in the picture you can see the header tank fed from the main tank and the regulator attached to the carb.

canardlover

OK, I see the white "square gadget" which I assume is the regulator.?! What make is it..? could you please provide a link to the regulator supplier...Thanks and cheers/

Rafael23cc

My Feedback: (6)

The "gadget" is a Cline Regulator. I do not believe the company is in business anymore. I do believe that OS Engines had a similar device in their lineup.

I found a picture of the OS Version. They call it the Demand Regulator System (DRS) on this particular application, it is mounted to an OS 55 helicopter engine.

Rafael

daveopam

My Feedback: (9)

I'm sorry, I don't mean to be a Debbie Downer or offend anyone, but WHY? This goes against the KISS way of doing things. I don't see a benefit over two smaller tanks side by side. If anything I see a more complex and less reliable system. Sure you can get it to work with two clunks and a check valve and regulator etc..etc. But I would argue you have a less reliable more complex system. If your tank needed to be back in the fuse away from the engines I would understand. If that's not the case a two tank system is going to be the right answer.

David

canardlover

Rafael, thanks for pics, will check what is available here.
David, I fully agree that the KISS principle is a good one. That´s why I do consider one tank and not two tanks. I still think my initial sketch above is the simplest setup possible and I believe it will work fine even without check valves. One draw-back is that both engines will stop simultaneously when fuel is out-
In summary: thanks for input, I will now "sleep on" the different options before deciding...Cheers/

daveopam

My Feedback: (9)

I think as long as both engines are running it would be a simple system. I would use a 3 line set up. One vent line with a T fitting and two clunk lines. Even if one engine dies the other should run as long as you keep the nose down or level. The thing to watch out for would be a missed landing attempt. If pressure is low in the tank and you advance the throttle with the nose up, you are in trouble.

David

JohnBuckner

My Feedback: (1)

Over the years I have done many multi's totaling around 19 or 20. In addition to the Twins I have also done three triples, three four engine aircraft and one six engine airplane. All have been .25 or larger sized glow engines and heck I most recently did a twin with both a glow engine as well as a jet turbine engine but yes that one is a mixed fuel airplane. So I suppose that does not count in this discussion

Anyway for what its worth the true KISS system (two engines two fuel tanks, three engines three fuel tanks etc.) Has never failed me in any of my projects and all I have listed have been quite successful. However many of my friends who have persisted with single tank systems have all failed for one reason or another and either quit or converted to two engines two fuel tanks, three engines three fuel tanks etc.

John

daveopam

My Feedback: (9)

^^^^^^^^^^^^^^^^^^^^^^^^^^ If John says two tanks, I would do two tanks.

David

canardlover

OK, thanks all for input, will decide later as my design develops...Cheers/

Pylonracr

Many years ago, one of the flyers at our field built a C-47 (DC-3) with twin 40 engines and 1 large tank in the fuselage due to the size / wing outline as there was not room for much fuel near the engines. He used no muffler pressure and a Perry pump on each engine. It did work as I saw it fly a few times, but I can't comment on the reliability or any problems he may have had with it.

Scott

Zoomer02

Been there done that and it does not work. When you start the first engine the pressure in the tank floods the second engine. If you use check valves, the pressure does not reduce at low throttle setting flooding both engines. Lots of unexpected things happen none of which are good. On planes where I have little room in the nacelles, I use a header tank and put a larger tank in the fuselage. So I run 4 tanks for two engines. I have been flying a plane with this configuration for over 20 years now with no problems at all. Mount the two tanks in the fuselage on the CG or if too narrow, one in front of CG and one behind CG so that they balance and have little effect on the overall CG as fuel drains.

I know Twinman was able to get this to work as proof of and absurd concept for a kit building company that wanted to be cheap and only use one tank, but he had to use perry pumps to feed the engines to prevent the above mentioned problems, then you need to plumb fuel return lines back to the tank. Makes for a crazy complicated set up. He showed me a picture of the single tank with something like 9 lines going in and out of the system. Good luck with your project.

Zoomer02

I found Twinman's comments from his experience with this. Follow this link: http://www.rcuniverse.com/forum/twin...project-7.html
Good luck

canardlover

OK guys, seems I opened a real "can of worms" and after all your comments I´m inclined to stick to 2 engines/2 tanks....cheers/

Walther

My Feedback: (1)

Here is a link to the Cline fuel regulator. ACCESSORIES

canardlover

Walther, many thanks for the above link..! And YES..! the description was certainly very informative and I feel the issue is again an open question in my mind. Will decide later when my build proceeds to the critical point. It also appears that overflooding of the "dead" engine is not an issue with the Cline regulator. THANK YOU..!!

Propworn

My Feedback: (3)

Very simple mount the engines on a test stand as they would be in your application. Make sure the test stand can be rotated as per how the engines might find themselves in flight. Fuel tank or tanks mounted as per the application. Set up each engine individually with its own tank (i would use a different test stand) and tune engine until it runs perfect.

Mount the engines on the twin test stand and try them with single tank, twin tanks and variations until you fine the most reliable setup. Twins need to be reliable an engine out most times spells disaster.

good luck
Dennis

canardlover

Yes Dennis, but what cannot be easily simulated are the acceleration/deceleration and the G-forces on the flying aircraft. However, the completed airplane could at least be held and rotated with engines running similar to your suggestion above. I guess that is the closest I could get.