Tag-Along Aux Fuel Tank (joe2lmaker)

[Joe2Lmaker]

Should we start talking to Linda T now or wait until we have the completed tank in hand?

I think it's a good idea to talk to her. Let her know that there are seven of these things. Two prototypes and 5 production tanks.

There might not be seven imediate sales, but it can't hurt to let her know there are seven potential sales.

I would wait to order. Even though everything is on track (sheets to be cut and bent next week), I would still wait to order covers.

Maybe we can get 01VFR's spare tank sold. Maybe if the covers aren't to expensive, I'll buy one too.

Give the information to Linda. Let her know what we have going on and see what she says.

just my opinion

 

[daddyman]

Quirky.

Ha.

That's exactly what my boss says about me. I guess that means I'll take a patch!

(I told one of my old supervisors that what I like about my job is that the company, unlike other places, doesn't push people to fit into their way of thinking, but rather accepts people with whatever personality quirks--or psychological disorders--they have, and practically encourages them to burst forth into full bloom.)

I prefer the non-violent Kitty, please. So just send it off to Linda when we get the covers made and have her sew it on.

My daughter will be in heaven.

 

[dcarver]

Should we start talking to Linda T now or wait until we have the completed tank in hand?

I think it's a good idea to talk to her. Let her know that there are seven of these things. Two prototypes and 5 production tanks.

There might not be seven imediate sales, but it can't hurt to let her know there are seven potential sales.

I would wait to order. Even though everything is on track (sheets to be cut and bent next week), I would still wait to order covers.

Maybe we can get 01VFR's spare tank sold. Maybe if the covers aren't to expensive, I'll buy one too.

Give the information to Linda. Let her know what we have going on and see what she says.

just my opinion

That sounds reasonable and actionable. Linda will then have a better cost estimate for us too; and cost is a consideration for me, unfortunately.

 

[dcarver]

Ok, more flow experiments today -

Per a Tanji tank user, who has run, and placed very high in the IBR, the recommendation was "run the main tank down to approx 50-70 miles" then open (the full) aux tank. Per said inside informant, many various designs of gravity fed aux tanks have had weird issues in draining at different main/aux tank fuel levels. [SIZE=8pt](I will ask this person if it's OK to post his PM to me, won't do so unless approved. )[/SIZE]

So, I did. Can't argue with a LDR who has been there, done that. Ran the main to 65 miles, showing 33 mpg avg, yes, I speed. Opened the fully filled aux and rode for about an hour.

Results = static. I started at 3 bars down, and the fuel gauge remained at 3 bars down for over an hour. The only real indication was the miles traveled. Normally at 100, I'm at least at half tank indicated. This time, I remained at 3 bars consumed and it just stayed there at 150 miles. Obviously, the fuel is transferring.

My deduction is that with the main at 3/4 full, and the Aux at 4/4 full, at speed, the fuel consumed +delivery rate = 0. Meaning the aux tank was delivering the same flow rate as consumption. Tomorrow I'll test more.

BTW, since the one-way valve was too restricitve, I removed it, meaning the main can fill the aux, as RenoJohn once experinced. So I even pulled off the road to see if the main tank was *back-flowing* the aux, it was not - the filter sock was dry. BTW, I found a cool solution for keeping the vent line clean yet still able to drain, check later for pix.

Arrived home, 3 bars down, looked inside the aux tank and it's about 1/3 consumed. Very cool.

Hope this helps.

 

[Good2Go]

Ok, more flow experiments today -
Per a Tanji tank user, who has run, and placed very high in the IBR, the recommendation was "run the main tank down to approx 50-70 miles" then open (the full) aux tank. Per said inside informant, many various designs of gravity fed aux tanks have had weird issues in draining at different main/aux tank fuel levels. [SIZE=8pt](I will ask this person if it's OK to post his PM to me, won't do so unless approved. )[/SIZE]

So, I did. Can't argue with a LDR who has been there, done that. Ran the main to 65 miles, showing 33 mpg avg, yes, I speed. Opened the fully filled aux and rode for about an hour.

Results = static. I started at 3 bars down, and the fuel gauge remained at 3 bars down for over an hour. The only real indication was the miles traveled. Normally at 100, I'm at least at half tank indicated. This time, I remained at 3 bars consumed and it just stayed there at 150 miles. Obviously, the fuel is transferring.

My deduction is that with the main at 3/4 full, and the Aux at 4/4 full, at speed, the fuel consumed +delivery rate = 0. Meaning the aux tank was delivering the same flow rate as consumption. Tomorrow I'll test more.

BTW, since the one-way valve was too restricitve, I removed it, meaning the main can fill the aux, as RenoJohn once experinced. So I even pulled off the road to see if the main tank was *back-flowing* the aux, it was not - the filter sock was dry. BTW, I found a cool solution for keeping the vent line clean yet still able to drain, check later for pix.

Arrived home, 3 bars down, looked inside the aux tank and it's about 1/3 consumed. Very cool.

Hope this helps.

Interesting.

Your description tells me that once you open the valve, the fuel levels in the aux and main tanks equalize. As you consume fuel, with the aux valve still open, the levels continue to equalize, resulting in miles traveled but your fuel gauge remaining at 3 bars down. I presume this "self equalization" will take place until both tanks are empty (?).

I've been under the impression that one would want to open the valve when the main is nearly empty, to dump the contents of the aux into the main...my main concern with the tag along design was that no one had proven this would actually happen. But if what I wrote is true, this "self equalization" would work as well.

Let me know if I'm way off base here; I've only started reading about this aux tank stuff within the past few months, and am still learning.

 

[Joe2Lmaker]

Your description tells me that once you open the valve, the fuel levels in the aux and main tanks equalize. As you consume fuel, with the aux valve still open, the levels continue to equalize, resulting in miles traveled but your fuel gauge remaining at 3 bars down. I presume this "self equalization" will take place until both tanks are empty (?).

...as long as you're not going up or down a steep grade.

I personally think Don should run 'til he can't run no mo'. That's the only way we'll know if the auxiliary tank drains fully. I would, but I don't have a tank right now. The fab shop wanted one of the prototypes for reference.

I've been under the impression that one would want to open the valve when the main is nearly empty, to dump the contents of the aux into the main...my main concern with the tag along design was that no one had proven this would actually happen. But if what I wrote is true, this "self equalization" would work as well.

I think your impression is right. I think that is the strategy for most gravity feed set-ups. Height would definitely be an advantage if that's your thing.

On the other hand, if your extended range is the same, wouldn't a lower center of gravity be desirable?

If the design is right for gravity feed, the Tag-Along won't leave you standing on the side of the road, engine starved for fuel with a gallon of gas that can't be used.

Don,

Put a new wooden paint stir stick and one of these in the side bag, and run those tanks Dry!

Then, dip the paint stick in the auxiliary tank and see what the level of unused fuel is in there. Close the valve. Add the gallon or two of gas to the main tank. Ride to a gas station. Fill both tanks and note how much fuel was required to fill both tanks.

Next, we need to figure out a way to do the same test with the other gravity fed tanks out there.

 

[Hello Kitty]

I'd be okay with trying it out around town. I wonder why this is an issue with the FJR. Was never an issue with the GS. maybe because the bulkhead fitting is under the tank? It was on the side on the GS....

On the tank bags, I'd rather wait until the tank is on the bike. You will want to see where things are to make decisions about how you want the bag to 'interact' with the tank and bike... I know Linda, I'll shoot her an email and give her a heads up.

 

[dcarver]

Your description tells me that once you open the valve, the fuel levels in the aux and main tanks equalize. As you consume fuel, with the aux valve still open, the levels continue to equalize, resulting in miles traveled but your fuel gauge remaining at 3 bars down. I presume this "self equalization" will take place until both tanks are empty (?).I'll do some static testing today, with various scenarios, (main 3/4 full, main nearly empty, etc).

I've been under the impression that one would want to open the valve when the main is nearly empty, to dump the contents of the aux into the main...my main concern with the tag along design was that no one had proven this would actually happen. But if what I wrote is true, this "self equalization" would work as well.

I already tested that, and the aux does fill the main, just not very fast. I believe this is common with all gravity feed tanks that have little head pressure, e.g. height differential between tanks. I guess I could try my engineer hat and calculate flow rate through 1/4" id tube at X inches H2o differential. Then again, not. I'll just test it in the real world.

My insider informant had mentioned his Tanji sometimes has issues flowing when the main is nearly empty and the aux tank is full. The speculation is that the air in the main tank compresses, impeding flow. Yes, I know it's a venting main tank, but it can and does still build some pressure, and when dealing with minimal head pressure, I could see how it's enough. Anyway, what works best for him is to use the method I just tested e.g. open aux when main has about 50 miles on it.

Either method, we know that fuel does flow, and that's the goal. :yahoo:

Let me know if I'm way off base here; I've only started reading about this aux tank stuff within the past few months, and am still learning.

See in line red comments.

 

[dcarver]

Ok, said inside informant gave me permission to post the PM.. Thanks SkooterG!

[SIZE=8pt](minor editing for typos)[/SIZE]

"Many of us had transfer 'issues' with the Tanji when we first bought them. Most of us have solved them in our own ways. Whatever cell you buy, you definitely need to get some miles with it to 'learn' it's characteristics and how it will and won't work.

Here's what I learned with my Tanji, and some of the same things most likely apply to most gravity fuel cells. Other's experiences may vary.

I open the valve to my cell after only 30-50 miles. (After filling both tanks) It works better this way. I don't know why. It doesn't make sense. If I let the main tank get low, I tend to have more problems with transfer. I think it has to do with the big pocket of air in the main tank not venting, building up pressure, and restricting, stopping, or even reversing flow. It doesn't seem to do this with a 'small' pocket of air. See more about this below.

One of the big issues initially with my Tanji (and it being gravity fed) was air in the line between cell and fuel tank. Gravity and the only slight difference in head pressure doesn't give a real big 'push'. Any air or bubbles in the fuel line and it can stop, or severely restrict flow. I learned early on that when filling the cell after it's been totally dry and/or off the bike that sealing my mouth around the cell filler and blowing would give that extra 'push' to get the air out of the line. I would have the fuel cap on the main tank open, and could hear the bubbles coming out. I would continue this until they stopped coming out. When doing this, especially if the fuel cell is totally dry, make sure the cell is full, and the main tank almost empty to get as much head pressure helping as you can. After the initia 'blow-job' to get things flowing, I don't have to do it again.

Another is the fuel filter installed in the line between cell and main if you have one. I don't know what kind of filter Dean installed on the cell when hem made it, but after two years I replaced it with one of those clear plastic or glass marine units. Well, after I put the new filter on, I observed my flow rate improve. So, obviously the original filter was a bit restrictive for gravity feed. If you need the particulars about the one I am using now, let me know.

Ok, for the biggie. For whatever phooked up reason, gravity feed cells can occasionally have issues with pressure building up in the main tank, and then reversing flow TO the cell, and in the case of the Tanji, dumping fuel out the vent line. This happens ALMOST exclusively with REALLY hot ambient temps. I have no idea why it does this. And I've spent a lot of time thinking about it. The thing is, in over 200k, my main tank (with no cell) has built up pressure to where the fuel cap 'pops' and hisses out the built-up pressure when opening it only once or twice. Yet with the cell, it's done this a dozen or two times. Why? I have no phooking idea. I used to think it had something to do with the Tanji cell, but that is not the case: Last June during the Utah1088 there were 3 of us that went to Las Vegas in the afternoon when it was 115+. Me, with the Tanji cell, Iggy with the BLM cell, and RenoJohn with the Skyway cell. Well, ALL of us had several instances of the main tank building pressure and reversing flow of fuel to the cell and out the vent. Three different gravity cells, in REALLY hot weather, experiencing the SAME problem MULTIPLE times.

For me, I had only had the pressure build-up thing occur 2-3 times in the last couple years. But on that afternoon, every time I filled it I experienced the problem. 4 or 5 times just that one afternoon. Of course, later that night when it was cooler, everything worked fine again.

To this day, it still drives me nuts why it happens with the cell installed, and not without. To me, the root cause is the FJR's main tank venting system. Adding a cell and hot ambient temps somehow triggers some kind of problem where it doesn't properly vent. I think the partial solution is installing a one way check-valve in the line between cell and main to at least keep fuel from flowing backwards, but I haven't been able to find one yet, and I am a bit worried about adding any undo restriction to a gravity feed system. Still, it sucks when you realize you have dumped a good gallon or more out the fuel cell's vent. Only way I know it is doing that is when the fuel bars on the fuel gauge start decreasing a lot more rapidly than they should.

As I said above, what I have found is that turning on the cell as early as practical helps, even with the heat issue. For whatever phooked up reason, less air space in the main tank is good thing for gravity transfer of fuel from the cell. It's not 100%, but definitely seems to help. Much less likely to encounter main tank venting issues and pressure build-up. I don't get it. I mean, as both the cell and main empty, let's say to half, there is more air in both tanks but I don't seem to have problems then. I just don't get it. BTW, at the last IBR I talked to some other east coast IBR riders who I can't remember right now and they told me they modified their main tank fuel cap (by removing the ball I believe - the ball that is designed to stop fuel from flowing out the filler cap when the FJR is on it's side) and that they have not had any issues since. Like I said, root cause is the main venting system.

Edit: I forgot to mention my re-fueling procedure which seems to work for me. When on the road and re-fueling, I try to have the main tank as empty as possible. I then close the cell valve and first fill the cell. I then open the valve and let it flow for a few seconds before closing the valve. While doing this, I can check to see that the fuel is slowly going down in the Tanji filler neck. Oh, and also I make sure the main tank fuel cap open. The reason I do all that is that almost all the time, I am running the whole system pretty dry. It's not uncommon for me to put in 10.3 - 11.2 gallons when re-fueling. And when I do this, I am pretty sure I am running the Tanji cell dry. I don't think it tends to get air in the lines, but I do the above to ensure I get good flow (with the head pressure help).

I'll be interested to hear your experiences with your new cell. I hope you get as much enjoyment out of it as I have mine. Even with your CandyAss.

Hugs & Kisses, babe."

 

[exskibum]

SkooterG:
"I learned early on that sealing my mouth around the cell filler and blowing would give that extra 'push' . . . . I would have the fuel cap on the main tank open, and could hear the bubbles coming out. I would continue this until they stopped coming . . . get as much head pressure helping as you can. After the initia 'blow-job' to get things flowing, I don't have to do it again.

* * * *

Hugs & Kisses, babe."

WTF!?! No one has gotten pictures of this?!? No wonder Skoot was secretive in PMing you, Don. He damn well knows that beemerdons will now be laying in wait with camera. :lol:

 

[Joe2Lmaker]

Don,

Step away from the computer.

You have some riding to do!

 

[exskibum]

Damn interesting read about SkooterG's experience. Just an observation that you may have considered, may be relevant, may not -- I'm not sure where it leads yet:

In addition to rising air pressure in the main tank on hot days (which we'd expect to vent if the main tank vent line isn't obstructed or kinked), the fuel in the main tank is expanding with the heat from the engine and is, therefore, less dense than the fuel in the aux. tank, which does not have a 1298cc heater directly under it.

At some point, probably in the line, the warmer and cooler fuel is meeting. Any chance that the tendency of the less dense warm fuel to rise (vis the cooler fuel) is causing some of this phenomenon when constricted from efficient mixing by the small size of the line in which this interface takes place? Or something like that?

 

[SkooterG]

I edited some stuff in CandyButt's post form my initial PM to him.

I love some good mental masturbation as much as the next guy, but try not to overthink this stuff too much. It either freaking works, or it doesn't. A cell owners job is to figure out how to make it work.

As for transfer, yes it's slow, but who freaking cares? Mine generally acts like yours, holding at 6 or 7 bars (out of 8 on a Gen I) for a long time. Occassionally, I see the fuel gauge actually increase a bar while fuel is transferring, but not usually.

Don, dude! You need to get rid of the POS yellow hard plastic line and get yourself some high quality fuel line.

 

[Joe2Lmaker]

Don, dude! You need to get rid of the POS yellow hard plastic line and get yourself some high quality fuel line.

That looks like Tygon

<Link>

 

[Hello Kitty]

Do you think that you HAVE TO wait until a gallon of gas has been used? I mean, why not just leave the valve open? I am just picturing myself forgetting all about opening the valve 30 min later, especially on Day 9.

Also wondering if putting some spacers under the cell would help? Dale suggested raising the cell a bit and I don't see what it would hurt. My Sampson on the GS sits quite high and I never had any problems with the weight. This might give a bit more head pressure, no?

I too would like to see Skoot blowing his fuel cell. Awesome!

 

[Joe2Lmaker]

Do you think that you HAVE TO wait until a gallon of gas has been used?

Yes.

The top of the auxiliary tank is higher than the top of the main tank. If you open the valve too soon, you risk pushing some of your fuel out of the main tank through the overflow vent.

 

[rickcorwn]

I too would like to see Skoot blowing his fuel cell. Awesome!

Blowing fuel cells has been a long standing tradition in LD circles mg:

 

[Hello Kitty]

Do you think that you HAVE TO wait until a gallon of gas has been used?

Yes.

The top of the auxiliary tank is higher than the top of the main tank. If you open the valve too soon, you risk pushing some of your fuel out of the main tank through the overflow vent.

Huh. Again, on the GS this wasn't an issue. I usually waited until my low fuel light came on to flip the valve just so I didn't have a partially full tank on the back, but there were a handful of times I just left it open and never had any problem at all. The top of that aux tank is significantly higher than the main tank. Like everyone has been saying, we'll just have to try things out and see what works and what doesn't. I will probably wind up with a note on the windscreen to remind me to flip the switch.

excellent!

RIP Eddie.

 

[Gramps]

Wouldn't one of these be better?

 

[CAJW]

Back in the late 70's I built and flew an ultralight (Mitchell Wing) that was powered by a racing go-kart engine (Mac 101) that had a fuel starvation problem while fast taxing. The issue was an inadequate engine mounted fuel pump trying to pull fuel up from the tank (located between my legs) 24" or so inches up to the engine. I would run, but ended up losing it's prime and then would die (not good while on climb out- been there done that) so I got one of these Linky to fix it. The main reason I tell this story is the one way check valve in this bulb primer (commonly obtained from an marine shop) fixed my problem and would probably help on preventing fuel from running back to the aux tank by keeping the fuel forward of the bulb primer. It could be plumbed in line near the main tank and actuated after fueling if there is any concern with air in the line between the two tanks. There are a lot smarter minds working on this issue than mine, but thought I'd throw this out just in case it might work.