Epoxy experience - Devcon HP250 and gas

[JohnK]

Early on in my build I designed a sump with check valves in it to retain maybe a couple of pints or so of fuel when the fuel level was low and I was cornering. The in-tank pump fitted in the sump and the return line from the fuel rail emptied into the sump. Working with sheet aluminum and having not yet decided to buy my TIG welder, I searched around for a good epoxy to hold the sump together. Devcon assured me that their HP250 High Performance Adhesive would live quite happily under gasoline. I used their mixing nozzle with their cartridge delivery system to ensure proper proportions and mixing.

Several years later and finally on the road, things seemed fine, but after tossing the car around a bit and getting to 1/4 tank, it became obvious that the sump wasn't working like I'd hoped. Then, even with a full tank, it began losing pressure sporadically when pulling away from a full stop.

Pulling things apart I found that Devcon had lied. The sump parts were all apart, though held in place by the tank foam. I'd put some of their epoxy around the electrics, and as it swelled it may have pulled things apart electrically somehow - not clear at this point exactly how this interrupted its operation, if indeed it did. The Deutsch bulkhead connector seems fine and disassembled with no problems once I cut away the dead epoxy, but I'm going to have Deutsch verify that this application is OK, and perhaps search for a heavier duty solution.

And of course, get my welder out and put the sump sheet aluminum together properly.

Beware manufacturer's claims!

[Klasik-69]

They may have not understood that their product would be immersed in gasoline all the time, and then again, with the use of ethanol now, the problem is no longer just plain gasoline. Alcohol has effects on plastic products that may not have been foreseen. You are correct, get out the welder and do it correctly. I think you have a good idea in building a fuel sump system to prevent fuel starvation.

[xflow7]

Sorry to hear about your troubles. I was curious about this so I hunted down the data sheet for the product

 

Seems to me whoever you spoke to in their applications department didn't know what they were talking about. According to their own published tech data sheet, the chemical resistance of HP250 is Very Good or Excellent for most chemicals *except* gasoline which is listed as Poor:

 

[url=http://www.devcon.com/prodfiles/pdfs/fam_tds_185.pdf][/url]http://www.devcon.com/prodfiles/pdfs/fam_tds_185.pdf

 

Dave

Edited May 3, 2012 by xflow7

[1turbofocus]

Have you ever looked at http://www.atlinc.com/racing.html they have some great sump systems and fuel cells

 

Tom

[JohnK]

Klasik-69: Even with an exceptional welding machine (way better than I deserve), I'm probably going to do mechanical joining with some sort of sealant. There's so little space and the alignment issues are so critical that the warping you get working with sheet will likely nix anything I'm capable of fabricating.

 

xflow7: apparently some mfg's make a product support line available, but don't bother making sure that those folk give out correct information. They've certainly lost a customer for life over the matter, in spite of the fact that lots of their stuff is good. I've talked to 3M support several times and have gotten engineers, and they've given me lots of their time and made sure I knew what I was working with. In spite of the fact that 3M stuff in general is expensive, it's nowhere near as expensive as all the work I'm going to have to go through as a result of Devcon's misinformation.

 

1turbofocus: I have now ! :-) Thanks for the link. I chose this route because this car's been an excuse to learn how to do a bunch of development stuff that I'd been turned onto over the years. Fuel cells really do make sense and I'll probably go that route when (if) I get to enjoy the thing on a track. They are a bit expensive and it'll be work finding one that will fit. I'd write a book about my experiences, but Carroll Smith's already done that for all of us.

 

Thanks all.

[blubarisax]

Tom is right about ATL. They make great fuel cells. They make the standard Caterham cell, and can make one to any size you want.