Rotopax / Fuelpax expansion in the sun

[976-HIKE]

What do you guys do to stem the expansion of these things in the sun? I hadn’t considered it and left my can in the 80 degree sun for about an hour and it ballooned up, warping it a little permanently. It can be vented a little at rest, but what do you do when driving in sunny weather?

 

[outback97]

The big problem is the liquid expansion with temperature. I've posted this before (link below) but here's what I do:

Underfill slightly. 2 GL gets 1.95 gallon, 4 GL gets 3.9 gallon. Set the can somewhere it can warm up. As the fuel warms up, vent the can a few times, while pushing in the sides.

I don't vent at all once the cans are acclimated in the above way. When the temp drops, it may get a little concave, but in my experience that's not a problem.

Yesterday we did a day trip to the desert, and I brought our 2GL can for a little range insurance. When I took the can out of the shed in the morning, it was slightly concave because it was 35F. I left it on the roof all day and it was very slightly convex, not bloated. Didn't need the fuel, so it went back in the shed where it's ready for the next trip. Someone will probably chime in about how I should vent every day, but this is what has worked for me.

Rotopax - Is there something better I should be using?

I ditched my four 2-gallon Rotopax after heat caused too much frustration: They swelled up in the mounts making them extremely difficult to screw off Once off the mounts the Rotopax tended to retain the new balloon shape making them difficult to reinstall They look really cool and are a good...

expeditionportal.com

 

[976-HIKE]

I‘ll try warming them up in the sun before closing the cap, theory being that it will stop expanding after a bit.

 

[outback97]

I‘ll try warming them up in the sun before closing the cap, theory being that it will stop expanding after a bit.

Yes, and push in the sides as you close it off if they're a bit distended.

 

[4000lbsOfGoat]

There is nothing you can really do to "stem the expansion" other than keep them cool. If they are in the sun, they are going to expand. As mentioned above, underfilling can help but even when "full" (i.e. 4 gallons in a 4 gallon) there is a still a good amount of air\expansion space left in the container.

I keep a pair of 4-gallon on the roof of my trailer. Over the winter I ran from western MT to southern AZ over the course of 3 days. Started in MT at around 25-30 degrees F, got up into the 70s\80s with full sun in AZ. They were definitely bigger at the end of the trip than the beginning but just venting them when we got there seemed to be fine. I think I vented them a couple more times here and there over the next 3 weeks in the desert.

If you're using the Rotopax mounts you need to be careful with how tight you make them. If you snug them down real good when the containers are cold they can be a real pain to remove after the containers have warmed up. If you tighten them down when the containers are warm, you'll find they are loose when the containers cool down. You kind of have to keep after the tightness of the mounts as temperatures change.

 

[Martinjmpr]

I ran RotoPax 3 gallon cans for several years and never had any issues. Yes, they expanded a bit when warming up but they never leaked, cracked or split. And mine were mounted horizontally on a roof rack, to boot.

 

[karlmagnum]

I know others drilled a hole in their Rotapax and installed a metal tire valve stem.

 

[Buddha.]

Don’t forget elevation change affects gas cans as well.

 

[Alloy]

Liquid expand less than the air so I overfill them.

If they expand allot when partially full I'll vent them off.

 

[Cabrito]

I think mine are permanently deformed at this point.

 

[Rando]

Exactly. It is not so much the gasoline that is expanding and causing the rotopax to expand, it is the vapor pressure of the gasoline and the thermal expansion of these vapors. Filling all the way full may help a little, but there is really no way to avoid this. Unfortunately the rotopax design is crappy at resisting this with two large plane parallel sides (relative to the volume) and not enough reinforcement at the mounting hole. I have certainly had an issue where it has been almost impossible to the unscrew the mount on a hot afternoon due to the expansion.

Rotopax look cool, but if I could fit a different container in the space I have, I would ditch them immediately.

Liquid expand less than the air so I overfill them.

If they expand allot when partially full I'll vent them off.

 

[Winterpeg]

The rotopax handles can also break when trying to screw them on or off.

Check your handles periodically and keep the threads oiled.

I had a handle break free from it's threaded rod end and had the aluminum handle come off... leaving the threaded rod still on.

I now keep an extra handle in my toolbox.

(and yes, liquid doesn't expand... it's the gaseous gas and air that does... underfilling the tank is detrimental)

 

[Alloy]

I think mine are permanently deformed at this point.

Wonder how much a cover / shading would do?

 

[MiamiC70]

I’m in S. Florida and honestly haven’t had a problem with my RotoPax. I don’t fill them all the way and have them mounted horizontally on roof rack. However, I do have a pair of RotoTrax stacked above them which does shade the RotoPax below.

 

[Buddha.]

My steel wavian cans are permanently deformed after one trip from St.Paul MN(600’and 30f) to Sante Fe NM (6000’? And 75).

The stream of gasoline when I stupidly opened the can up sprayed all over me and six foot over my shoulder.

It was actually pretty impressive.