martys40s

My Feedback: (213)

I AM BUILDING, RE-BUILDING, A SINGLE ENGINE MODEL INTO A TWIN. IS IT FEASABLE TO USE ONE FUEL TANK TO FEED BOTH ENGINES OR SHOULD I USE 2 TANKS?

Bad_Daddy

Why not? Your only concern will be that both engines can get their full draw of fuel.
I believe a .40 will use about 3/4 oz. per minute at full throttle, so if you had twin .40's you would need lines large enough to supply 1 1/2 oz. per minute. Since it would only take about 20 seconds for you to fill a 6 oz. tank thru the same fuel lines, starvation of the motors shouldn't be a problem unless you were talking about BIG motors.

Ed_Moorman

My Feedback: (1)

Bad idea, in my opinion.

How about pressure? You can't adjust the needles with only one engine running because the tank pressure leaks out through the other muffler. When one quits, the other will go lean due to lack of pressure. You are just asking for trouble.

There are 2 feasible ways. One is to install a smaller carb that will draw fuel without muffler pressure. The other is to use a pump.

I am on my 23rd twin and I have learned to use the KISS principle. You know, Keep It Simple, Stupid. Yep, my buddy and I learned this the hard way. Fly anything in a single engine, but for a twin, buy the most reliable engines you can, break them in first, set them up individually, run slightly rich and enjoy. Use 2 tanks.

evan-RCU

Bad idea, keep it simple, one tank per engine...

rrudytoo

My Feedback: (27)

If you used a check valve on the pressure line of each engine, wouldn't that negate the loss of pressure from the loss of one engine?

I don't see a problem with a single tank for two engines provided everything is plumbed correctly. There would be three lines utilized at the tank. Use two clunk pick-ups (one for each carb) and a single pressure / overflow line connected with a good quality tee fittting from each engine's muffler along with the aforementioned check valve.

The only hassle with this set up is fueling. You would need to disconnect the overflow line between the check valve and the tank for the overflow to function correctly. That and pinch off the carb line to the opposite engine to prevent flooding. Obviously, access to these lines would be neccessary. Use a tank twice the size (DUH!) of what you would use for a single engine application.

Now, having said all that, if you CAN facilitate a dedicated tank for each engine, that WOULD be the preferred method.

Good luck and have fun!!!

Al

BillS

Bad idea. I have attempted to use one tank with two engines and it doesn't work. The interaction of muffler pressures will not allow setting the high speed needles. The engines will run but cannot be synchronized. One engine was off it's maximum rpm by 1000 rpm.

Ed and Evan are correct. Keep it simple.

Since you received conflicting advice I suggest you experiment on the bench which is easy. If the engines do not run properly on the bench the concept certainly does not belong in the airplane.

Bill

martys40s

My Feedback: (213)

I thank you all for your advise. It looks like I will use 2 tanks and avoid any problems. Thanks again Marty

MormonMike

My Feedback: (2)

I agree, one tank/two engines don't work. You'll waste a lot of time trying to make it work. MM

Bad_Daddy

Hmmm - I hadn't thought of the tank pressure changes if one motor dies, and that would be a problem. I guess you showed me!

JohnBuckner

My Feedback: (1)

KISS-----One engine one tank, two engines two tanks, four engines four tanks. Anything less and you are looking for trouble.


Here is my latest project, six engines and of course six tanks. Nothing less.

John

BillS

With both engines at full throttle the tank pressure required was different which forced one side to be rich. Always one engine could not be leaned enough for max rpm. It was a mess and was not flown with one tank.

Bill

heli_Rod

Man, John, you are a glutton for punishment.....LOL!

I agree......K.I.S.S. I've tried tried several single tank setups over the years and never got satisfactory results.

Rod

Terror Dactyl

All that being said there is a safe way to accomplish this, but it is not using a pump

The way that you might want to consider is to use a Kline Regulator setup if you want to go scale and do not have good room for multi tanks to get a flight time you would be happy with

if you use 2stroke you can go with crankcase pressure with a check valve on each motor and if 4stroke use muffler with check valves.

You would then put a regulator on each motor and they will only let fuel through if there is venturi vacuum

Mine has worked well, but it is in a single engine setup

I will say that the 2stroke pressure will inflate the tank some and that is how I can say that it will work for multi as the inflated tank still does not push past the regulator.

Good luck on your project

Gremlin Castle

My Feedback: (14)

It depends on the configuration of the model as much as anything. In my gallery there are pictures of my DC-3 with inverted Saito 100s running on a single 40 oz tank sitting on the cg. The engines pull their fuel through Byron regulators and are dead reliable. The secret though is that the tank is above the motors even in the sitting position plus there is muffler pressure.

As a rule one tank per engine is usually the more reliable setup providing there is room for the required capacity tank in the nacelle.

Prairie Mike

If you are using gas powered engine with walbro (pumper) carbs, one tank will work fine. My flying pal has campaigned a DC-3 for 8 years using one tank. He originally used Qudra 35's and then switched to
G-38's. One tank was fine.

If you are using glo engines and muffler pressure, I'd use two tanks.

twinman

My Feedback: (2)

Above answers that say do not do it.. are CORRECT PERIOD!! Ok,,you won't listen...Ok,,listen to Ed Moreman and the clyme system....Ok,,you asked for it.
http://www.rcuniverse.com/forum/m_24...tm.htm#2447788
Don't do this, but it will work,
Twinman
PS Sorry, the person who refered to the gas engines that have fuel pumps, is of course correct also, but not glow.

Gremlin Castle

My Feedback: (14)

Does this mean that I should change my DC-3 to some little tanks instead of running 40 ozs in the fuselage?
Correct period? I really doubt that.

twinman

My Feedback: (2)

Ok Ok,,Regulators work too..Ha Ha Picky Picky, What I am getting at is that it adds unnecessary complexity and expense to make it reliable. You cannot just connect two engine to one tank without additional components.
Twinman

Rv7garage

My Feedback: (10)

twinman- after reading your thread on the B-17, I formally suggest that you change your name to "Four-Play". [sm=lol.gif]

Newc

Another thought...When there are two engines on one tank and the tank starts to go dry, it is likely that one engine will die first and as you then attempt to get the plane back under control with a single engine - and are very busy with that activity - the second engine will either slow down and die as the fuel funs out OR go lean and speed up just before it quits! Not a really good thing to have happen in my opinion.

twinman

My Feedback: (2)

Actually you are correct, but the same INVARIABLY happens with two tanks. The problem with one is reliable fuel flow.
Have a good one.
Twinman

Terror Dactyl

If you use the regulators and plumb the tank with one large line out to a "TEE" then run medium lines to the regulators and have the check valves on the pressure side of the tank you should have a very minor lag in effects to the engines.

Dont forget that this is a very stable fuel flow to the engines and the only time you should have a problem is if you dont tuse a good engine start up regimine or you forget to set some kind of reminder timer.

BTW there is only one regimine that I have found to really work:

1. start one engine and after short warmup set the needle for high (with tach or ear) and then back off needle one or two clicks, approx 300 R's,

2. shut off first engine

3. start second engine and tune to peak then back off needle just like on first engine

4. start first engine

5. DO NOT TRY TO MAKE BOTH ENGINES SOUND EXACTLY THE SAME WITH THE NEEDLES NOW. The reason I say this is that you have tuned the engines to their most reliable setting and any thing changed is asking for trouble.

Remember that unless you are trying to fly Pattern or IMAC you are just straining at nats bottoms and is it really worth the hassle and possible engine flame out

Lets see what kind of grief could we give him at the field if he changed to that, HHHHMMMMM

No I wont go there at this time (your safe for now Tm)