double clunk in fuel tank

[weasel]

when fitting a double, clunk to the fuel tank, do i have to join the two tubes together at the clunks. to stop them twisting around each other. or would this not likely happen..  

 

                         regards Weasel........ 

[Marko]

hi weasel  l dont mean to be negative but,,, lve  never heard of a double CLUNK in a tank before ,!! why do you think you need to as the engine pressure feeds the right amount of fuel it needs with the regular tubing maybe a little more explanation from you is need to help the most common setups  are with three tubes ,,middle tube (clunked )going to the carb another tube going to the exhaust for tank pressure ,and the other for tank filling also going to the top of the tank,some 4 strokes will run without tank pressure

 

 

 

cheers .........................mark

[weasel]

hello mark, i am setting up the double clunk, to a  vmar bulldog, as the engine is fully enclosed, its to make draining the tank, a lot eaiser. than tipping the model on to its nose, i have set the tank up with one feed to carb, (clunked) one to exhaust pressure, and the third. with clunk as fill and empty.  i seen a post on this subject but cant find it, about  defuling this way....   any help would be a bonus,...

 

      thanks Weasel..........

[ben hall]

Installation with Two Clunk Lines

If you have a glow engine, you'll have to install a third line to the tank. This is easy because most tank plugs have a third hole, it just isn't all the way through. So the first step is to go ahead and punch this hole all the way through. You can simply push a peice of metal tubing through the stopper to open it up.

You now have to decide if you want two clunk lines, or one clunk line. This is purely a personal choice.

I personally prefer having two clunk lines. This makes it easy to remove the fuel from the tank. It also comes in very handy when trouble shooting your engine. If you suspect that the fuel suction line is the cause of your engine problems, you can simply switch the fueling line with the carburetor line to see if your engine problems go away.

This is much easier than removing the tank to physically check the condition of the clunk line in order to eliminate it as the possible cause of your problems.

 

 

[inspector9566]

Hi Weasel

   I personally wouldnt tie the two lines together as it would not allow the pick up line to move around to the corners of the tank try holding on to the two lines where they would enter the tank with the lines tied then move them around then un-tie them and try it again you will find that they move alot easier as for them getting tangled I wouldnt have thought that the lines inside the tank would be long enough to get knotted together.

hope this helps with your original question.

[ben hall]

+1 to inspector the lines indeed would be too short to allow tangling problems .

[Frank Skilbeck]

I've run a twin (Vega 50T) with a separate feed to each carb, i.e. twin clunks, I didn't tie them together and they never got tangled up, but this was on a fairly small tank (6oz)

 

As above I'd be wary of tying them together as this will have the effect of making them stiffer and hence they may not move around as freely.

 

If you are running a larger tank then using a short piece of fuel tube with a straight length of brass tube would also stop them from getting tangled up if thats a concern.

 

 

[Marko]

You never stop learning in this hobby l can now see what weasel said ! It makes de-fueling a lot easer this way if you have a fully cowled engine saves turning the plane upside down l will convert my tanks like cheers ...........mark

[Peter Beeney]

 

    Frank,

        Just as an item of interest, I discovered, a long time ago, that in some circumstances methanol can attack the brass tubing. I had an aerobatic model which suddenly started going dead stick halfway through the flight. But when I tried to drain the tank it appeared to be empty!!  So, I had to get down to it and I instantly discovered that all three tubes in the tank appeared to have swollen up and split open and on the most severe the edge had actually curled back.
    I bought a roll of 1/8 i/d copper tubing, which just happened to be the right outside diameter, and replaced everything.

    I have since read of this happening elsewhere, but only very seldom. So it may not be a big issue. Perhaps only some types of brass? I’ve noticed, too,  that some tanks appear to have an aluminium or dural type of plumbing, I’m sure that’s impervious.
    I’ve only ever used straight fuel, with a slightly less than normal amount of synthetic oil.

    Whenever possible, I always use plastic tube for joining etc. The odd bits from snake push rods or perhaps expired ball-point pen refills. Again, I found out the hard way, right back at the beginning, that you need to carefully ‘round off’ the sharp edges of metal tube. Silicon fuel tube does not want a lot of persuading to propagate holes where they shouldn’t be!      

    Hopefully a helpful observation.                 PB
                                                                                                                 

Edited By Peter Beeney on 13/03/2010 11:56:13

[Jimbo565]

weasel an easyer way to de fuel with out a double clunk would be to put a tee piece on the carb fuel line and just shut the needle valve while filling and emptying

[Steve Hargreaves - Moderator]

I use this method in all my models......works very well!!!!! Fill & drain via the same tube.

 

I certainly don't bother tying the clunks together....let it all hang free!!!!

[weasel]

Hello Ken Hope This Helps..    Regards Weasel....