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  • November 18, 2019, 02:17:25 PM

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Author Topic: Two-ounce Clunk Tanks  (Read 474 times)

Offline Dave Moritz

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Two-ounce Clunk Tanks
« on: November 08, 2019, 11:54:38 AM »
Am back to the well for more help from the brethren assembled herein. 

Would like to replace the internal flexible lines on both of these tanks, but not sure what fuel line to use. Neither of the clunks is flexible enough to reach all the rear corners of the tank (they just kind of hang there mid-fuel even though not touching the back of the tank; not sure what will happen when they get into the air.). As they are, the short length of fuel line to the clunk is the medium-sized stuff (standard for the 1/8" brass pipes).  Will use one of these for .090 Enya and the other for .15 Enya.

Solutions I've in mind include: 1) more clunk weight); or 2) smaller fuel line of the type used for 1/2A.

Maybe fuel pickup will be fine if I fly them as is? Suggestions?

Dave Mo...

Online Dave Hull

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Re: Two-ounce Clunk Tanks
« Reply #1 on: November 08, 2019, 12:44:27 PM »
Moe,

That's a common issue. But you really need to take on the attitude that "if it doesn't look right on the ground (or while you're building it), then it won't get better in the air." Kind of an attitude about quality. Especially with fuel tanks since an erratic run can either quit before the tank is really empty, or cause a lean run and cook the expensive pieces.

As far as the tubing, there is some silicone tubing out there that has the standard ID, but with thin wall. It is very flexible. I use it for racing where the line has to go thru a pinch-type shutoff. Unfortunately, I do not have a ready source and am the end of my stash. I am curious too about where I could get a couple feet of the stuff. But we at least know it exists. So I'm looking too. By the way, I have read that Sullivan provides a more flexible line for these. I have not found it to be as flexible as I need it. The problem is highly compounded when the tank is small, as in your case.

I happen to like clunk tanks and have had good luck with them. Some guys just can't get them to run right and so they hate 'em. You could break off your needle valve and they'd blame the clunk tank....

Stay warm there Up Nort'. The weather report is calling for a Three Hodag night….

The Divot

Online Tim Wescott

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Re: Two-ounce Clunk Tanks
« Reply #2 on: November 08, 2019, 02:11:55 PM »
Bend the fuel pick-up tubing (the brass part) so that it's aimed where the clunk should be in normal level flight; that way all of the flexing of the tubing will be to slide the clunk up or down as you maneuver.

Beyond that -- I often use small tubing for this, if it's a small engine.  I wish I could find some of the stuff that Dave talks about -- I wonder if a search through industrial sources would find something (I doubt that there's a Model Airplane Fuel Tubing Factory out there -- the normal suppliers are almost certainly getting tubing meant for some industrial purpose or another and rebranding it).  A search through Amazon and the McMaster-Carr website may be worthwhile.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Carl Cisneros

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Re: Two-ounce Clunk Tanks
« Reply #3 on: November 09, 2019, 09:57:36 AM »
here is a choise from McMaster Carr

https://www.mcmaster.com/silicon-tubing

the ones on the bottom row

Carl
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Online john e. holliday

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Re: Two-ounce Clunk Tanks
« Reply #4 on: November 09, 2019, 10:21:04 AM »
Try a search on the evil Ebay.  That is where I got mine. D>K
John E. "DOC" Holliday
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Online Fredvon4

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Re: Two-ounce Clunk Tanks
« Reply #5 on: November 09, 2019, 11:44:44 AM »
Texas Timers

http://www.texastimers.com/

We have never carried the usual latex tubing for fuel lines because all the products were basically the same, and we could not offer anything better to the modeling community.

That is all changed now. We have located 1/8th -inch tubing made from the same space-age material used in our .020 tubing.  This size is perfect for all 1/4A and up free flight use.  It is so soft that even our competitor’s timers will pinch it off.  But much more importantly, it greatly outperforms and out lasts the latex type of fuel line.  No more gummy fuel lines caused by deterioration with high nitro fuel usage or long exposure to sunlight.  Plus, it can be stored in your box for years with no effect.  It is superior to the usual 1/8th  latex tubing in all ways. This is the answer to all your glow fuel line needs.

"A good scare teaches more than good advice"

Fred von Gortler IV

Online Dave Hull

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Re: Two-ounce Clunk Tanks
« Reply #6 on: November 09, 2019, 01:35:29 PM »
The tubing that I have (which is almost gone) that I am 100% happy with for pinch-off fuel lines and clunk tanks measures .106" ID and .160" OD. The wall is therefore around .027". It does not seem to collapse for me in the bend area around the needle valve, but is about as flexible as you could ask for. So this is my gold standard.

I have two different Hobby Shop sizes in my stash. Neither one is good for clunks or shutoffs. They are fine for all the other plumbing, except for diesels, of course. (Which is a whole different problem....)  I do not know the brands as I either bought them off the roll or discarded the packaging. Sorry.

     .125" ID x .247" OD transparent blue silicone

     .093" ID x .215" OD transparent blue silicone

As far as the McMaster Carr choices:

Which one(s) exactly, are you referring to Carl? Have you purchased or used any of these?

I searched thru the whole list. Here are my conclusions, based on the catalog, but not on purchasing any to test:

The standard size is 1/8" ID and 1/4" OD. For our use, I would call this a heavy wall, and no different from the hobby shop size.

In some of the more esoteric sizes--with matching prices--I found this one that might actually be suitable. It has a much thicker wall that the stuff I like, but is still better than the hobby shop sizes. The durometer is not given in every case, so a full comparison is not possible without buying samples. And of course, for our application, having a clear or transparent fuel line can be an enormous help in general operation and troubleshooting.


Offline Dave Moritz

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Re: Two-ounce Clunk Tanks
« Reply #7 on: November 10, 2019, 11:56:33 AM »
A boatload of good thoughts here. My apologies for such a slow response - the fear of Divot's triple header Hodag disrupted several nights of sleep. Ha! Where is Paul Bunyan when you need him?

For the time being, I'll take Tim's advice and orient the brass pipe and Sullivan-type pipe towards the outer side of the tank. I guess we modelers just don't command enough market power for that dedicated fuel line manufacturing plant (ah, as the scales fall from my eyes!).

Carl and the Divot both have a good take on McMaster's supply. John, I gave "da Bay" a look, but found the search results voluminous and hard to interpret. If you still have any info on what you got and who from, it might prove helpful.

In the final analysis, Fred's suggestion might be just the ticket. I'll shoot Texas Timers an order in the next week or so. If that doesn't work, then it'll be McMaster. Will report back here with results on the TT stuff.

Moe...

Online Brett Buck

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Re: Two-ounce Clunk Tanks
« Reply #8 on: November 10, 2019, 02:32:54 PM »
Am back to the well for more help from the brethren assembled herein. 

Would like to replace the internal flexible lines on both of these tanks, but not sure what fuel line to use. Neither of the clunks is flexible enough to reach all the rear corners of the tank (they just kind of hang there mid-fuel even though not touching the back of the tank;

   Use Sullivan Pro-Flex - extremely flexible, almost like the old gum rubber, but chemically bulletproof.

http://sullivanproducts.com/product/s211/

   Brett

Offline Dave Moritz

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Re: Two-ounce Clunk Tanks
« Reply #9 on: November 11, 2019, 09:24:59 AM »
Very good, Brett. I read your suggestion just after my TT order went out. Will place it in the queue for next consideration should the TT stuff not do the job.

Moe...

Offline Paul Smith

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Re: Two-ounce Clunk Tanks
« Reply #10 on: November 11, 2019, 04:18:54 PM »
2 ounce clunk tanks are not a good thing for control line stunt.

There just isn't enough room for the clunking to work right.

Remember, RC planes have throttles and do not terminate the flight by running out of fuel. So RC'er don't care about being "good to the very last drop" like Maxwell House coffee and control line stunt.
Paul Smith

Offline Dave Moritz

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Re: Two-ounce Clunk Tanks
« Reply #11 on: November 12, 2019, 12:32:15 PM »
Hmm..., you might be on to something here, Paul. A two-ounce tank is awfully short, but I'll give one the empirical test with some of the newer flexible fuel lines. Could be a wasted effort, but not it will be be my first success at that dubious accomplishment!

Thanks for the comment!

Moe...

Online Brett Buck

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Re: Two-ounce Clunk Tanks
« Reply #12 on: November 13, 2019, 12:02:44 AM »
Hmm..., you might be on to something here, Paul. A two-ounce tank is awfully short, but I'll give one the empirical test with some of the newer flexible fuel lines. Could be a wasted effort, but not it will be be my first success at that dubious accomplishment!

  He's about right if you use silicone tubing, even the really thin stuff they use for clunk tanks. What they use is more-or-less identical to the very first surgical silicone tubing they sold for model use. It's extremely fragile and easily torn/cut, but it was A LOT better in almost any regard than what we used before - gum rubber surgical tubing or neoprene. Gum rubber got sticky in a week or so, neoprene was chemically durable, but both of them melted easily if they touched anything hot. Silicone is barely affected by fuel and can withstand touching a muffler or header.

   The Pro-Flex stuff is very flexible and will work fine in a small clunk tank.

    Brett

Offline BillP

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Re: Two-ounce Clunk Tanks
« Reply #13 on: November 13, 2019, 05:55:13 AM »
Several guys on a glow rc car forum are using tubing out of a kit for gas weed trimmers. I have one of those kits handy to look/see. It has 3 pieces of tubing and they look like 3 different materials/sizes. The pkg doesn't say material type but one looks like the small thin walled flexi tubing that comes with glow tanks.  I bought this kit at Homedepot for my lawn gear for around $10. Might be an option if you can't wait to order something.
Bill P.

Offline Dave Moritz

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Re: Two-ounce Clunk Tanks
« Reply #14 on: November 16, 2019, 06:18:05 PM »
Gents:

The Texas Timer order came in today. Below are two pics showing their small fuel line in context. The first shows the line adjacent to a 1/8" OD copper pipe. The line appears to be made of some kind of very flexible, thin silicone material. The second pic shows a clunk and the line installed on the copper pipe (background). The clunk opening is 1/8" ID so I'll need to solder a short length of copper pipe onto it so the line can be attached. The clunk is plenty heavy for such a small and flexible line. The line's ID should be good for the motors I've got in mind.

When it comes time to place a tank order from Sullivan, I'll put the pinch on some of their line a la Brett and report back.

Moe...

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