| Gas Tank Heat Shields [message #89721] |
Thu, 24 June 2010 11:44  |
Neil
Messages: 271
Registered: July 2007
Location: Los Angeles and Magalia, ...
Karma: 1
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Well, I am going to start on fabricating heat shields for the gas tanks this weekend. I am thinking 1/4 aluminum diamond plate, with spacers between the diamond plate and the tank, secured on three sides by the frame rail with maybe one "finger" in the middle of the passenger side diamond plate extending over the exhaust pipe to the passenger side frame rail. I already have heat shields between the exhaust pipes and the gas tanks.
Any been there done that advice before getting started?
Neil
76 Eleganza now sold
Los Angeles
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| Re: [GMCnet] Gas Tank Heat Shields [message #89725 is a reply to message #89721] |
Thu, 24 June 2010 12:05  |
Carleton Douglas[1]
Messages: 174
Registered: March 2006
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I/4" is way to thick, 1/16" is all you need and forget about the
diamond plate too costly and one will see it any way. Put some stand
offs so you have about 1/2 air space.
On Thu, Jun 24, 2010 at 9:44 AM, Neil Martin <nmartin@hfbllp.com> wrote:
>
>
> Well, I am going to start on fabricating heat shields for the gas tanks this weekend. I am thinking 1/4 aluminum diamond plate, with spacers between the diamond plate and the tank, secured on three sides by the frame rail with maybe one "finger" in the middle of the passenger side diamond plate extending over the exhaust pipe to the passenger side frame rail. I already have heat shields between the exhaust pipes and the gas tanks.
>
> Any been there done that advice before getting started?
> --
> Neil
> 76 Eleganza
> Los Angeles
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--
Carleton Douglas
73 custom, by myself
Prescott, AZ
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| Re: Gas Tank Heat Shields [message #89729 is a reply to message #89721] |
Thu, 24 June 2010 12:41 |
voodoolng
Messages: 40
Registered: February 2004
Location: Colo
Karma: 0
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Hi Tim here
I used the heavy guage siding from metal buildings and cut it to fit inside frame rails. I took 1 inch L iron and made a slow Z from upper crossmember to the lower next crossmember and bolted 3 of them and covered them with the alum. shield. It channels the air under and not through the gas tanks. I drilled and tapped the L brackets and bolted the sheet in place. This way you can removed the sheet for maintenance on gas line etc.
So the shield starts up toward the floor on first crossmember then angles down then plans to the flat of the tanks.
This seens to divert the air down and not through the tanks. Has really helped on the heating of the gas tanks.
73 Glacier Voodoo lounge
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| Re: [GMCnet] Gas Tank Heat Shields [message #89742 is a reply to message #89721] |
Thu, 24 June 2010 15:03 |
powerjon
Messages: 2446
Registered: January 2004
Karma: 5
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Don't spend so much on materials. Go to Lowes or Home Depot and get a
singe piece of aluminum siding in white. Plenty thick enough to make
up a heat shield.
J.R. Wright
On Jun 24, 2010, at 12:44 PM, Neil Martin wrote:
>
>
> Well, I am going to start on fabricating heat shields for the gas
> tanks this weekend. I am thinking 1/4 aluminum diamond plate, with
> spacers between the diamond plate and the tank, secured on three
> sides by the frame rail with maybe one "finger" in the middle of the
> passenger side diamond plate extending over the exhaust pipe to the
> passenger side frame rail. I already have heat shields between the
> exhaust pipes and the gas tanks.
>
> Any been there done that advice before getting started?
> --
> Neil
> 76 Eleganza
> Los Angeles
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
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J.R. Wright
GMC GreatLaker
GMC Eastern States
GMCMI
78 30' Buskirk Stretch
75 Avion Under Reconstruction
Michigan
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| Re: Gas Tank Heat Shields [message #89817 is a reply to message #89721] |
Fri, 25 June 2010 08:51 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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has anyone actually put a thermocouple on a tank and measured tank temp before and after adding shields?
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: Gas Tank Heat Shields [message #89820 is a reply to message #89817] |
Fri, 25 June 2010 09:11 |
Neil
Messages: 271
Registered: July 2007
Location: Los Angeles and Magalia, ...
Karma: 1
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Senior Member |
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I am going to take pictures to share.
I havn't measured before temps, other than to "know" that on the last trip, by the afternoon, we had fuel big time boiling in the tanks, and even with a electric pump, a big drop in power.
Still toying with the idea of spraying lizardskin on the tanks before putting the heat shield on.
I want this to be a do it once, do it right, never have the problem again repair.
Neil
76 Eleganza now sold
Los Angeles
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| Re: [GMCnet] Gas Tank Heat Shields [message #89844 is a reply to message #89822] |
Fri, 25 June 2010 12:37 |
fred v
Messages: 999
Registered: April 2006
Location: pensacola, fl.
Karma: 0
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thanks Gene. he states the highest temp he saw was 148 deg. what temp. does the E-85 fuel boil? i think someone commented on that in another thread but i cannot remember.
Fred V
'77 Royale RB 455
P'cola, Fl
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| Re: Gas Tank Heat Shields [message #89877 is a reply to message #89721] |
Fri, 25 June 2010 14:47 |
GeorgeRud
Messages: 1380
Registered: February 2007
Location: Chicago, IL
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I don't recall the vendor, but someone here had made some heat shields available that were already cut and pre-bent. They went on easily when I replaced my exhaust and seem to be doing fine.
Does anyone remember who made them?
George Rudawsky
Chicago, IL
75 Palm Beach
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| Re: [GMCnet] Gas Tank Heat Shields [message #89879 is a reply to message #89877] |
Fri, 25 June 2010 15:11 |
Dennis S
Messages: 3046
Registered: November 2005
Karma: 2
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Senior Member |
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George,
Bill Brown had some exhaust heat shields made -- I believe JimK now sells them. Several owners now are discussing shields across the bottom of the tanks to eliminate radiant heat from the pavement.
Dennis Sexton
73 GMC
Germantown, TN
USA
-----Original Message-----
From: George Rudawsky <GeorgeRud@aol.com>
To: gmclist@temp.gmcnet.org
Sent: Fri, Jun 25, 2010 2:47 pm
Subject: Re: [GMCnet] Gas Tank Heat Shields
I don't recall the vendor, but someone here had made some heat shields available
hat were already cut and pre-bent. They went on easily when I replaced my
xhaust and seem to be doing fine.
Does anyone remember who made them?
-
eorge Rudawsky
hicago, IL
5 Palm Beach
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MCnet mailing list
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Dennis S
73 Painted Desert 230
Memphis TN Metro
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| Re: [GMCnet] Gas Tank Heat Shields [message #89880 is a reply to message #89877] |
Fri, 25 June 2010 15:14 |
Ken Coit
Messages: 151
Registered: November 2005
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Emery,
I didn't mean to imply that ethyl alcohol was going to boil first or last.
Note that gasoline is all over the place, depending on the additives.
However, it does seem likely that the boiling point is going to trend
towards the alcohol as you add more and more, no matter what the direction.
174°F isn't that much above the pavement in some places on some days.
George,
I think Bill Brown is the source for those shields between the exhaust and
the tanks.
On Fri, Jun 25, 2010 at 3:47 PM, George Rudawsky <GeorgeRud@aol.com> wrote:
>
>
> I don't recall the vendor, but someone here had made some heat shields
> available that were already cut and pre-bent. They went on easily when I
> replaced my exhaust and seem to be doing fine.
>
> Does anyone remember who made them?
> --
> George Rudawsky
> Chicago, IL
> 75 Palm Beach
> _______________________________________________
> GMCnet mailing list
> List Information and Subscription Options:
> http://temp.gmcnet.org/cgi-bin/mailman/listinfo/gmclist
>
--
Ken Coit, ND7N
Raleigh, NC
Parfait Royale
1978 Royale Rear Bath, 403, 3.07
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| Re: [GMCnet] Gas Tank Heat Shields [message #89882 is a reply to message #89880] |
Fri, 25 June 2010 16:10 |
Neil
Messages: 271
Registered: July 2007
Location: Los Angeles and Magalia, ...
Karma: 1
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Senior Member |
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On the subject of shields between the exhaust and the tanks.
I had some made while on the road at a nice place called Deep South RV in Mobile.
Didn't stop the fuel from boiling in the tanks.
Neil
76 Eleganza now sold
Los Angeles
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| Re: [GMCnet] Boiling Point of Gasoline / Alcohol mixtures - WAS: Gas Tank Heat Shields [message #89886 is a reply to message #89880] |
Fri, 25 June 2010 16:26 |
emerystora
Messages: 4442
Registered: January 2004
Karma: 13
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Senior Member |
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On Jun 25, 2010, at 2:14 PM, Ken Coit wrote:
> Emery,
>
> I didn't mean to imply that ethyl alcohol was going to boil first or last.
> Note that gasoline is all over the place, depending on the additives.
> However, it does seem likely that the boiling point is going to trend
> towards the alcohol as you add more and more, no matter what the direction.
> 174°F isn't that much above the pavement in some places on some days.
>
When it comes to predicting the boiling points of mixtures it get very complicated. Adding more ethanol doesn't necessarily mean that the boiling point will get closer toward the alcohol's boiling point.
Mixtures of gasoline and ethanol deviates from Raoult's Law caused by variation in intermolecular forces in pure alcohol and in hydrocarbon solution.
Most gasoline components follow Raoult's Law - that is their individual component vapor pressure is the product of their pure component vapor pressure times their mole fraction (or in other words - their percentage in the mixture). This Raoult 's Law behavior allows us to predict the vapor properties of most gasoline blends - each component will contribute according to its concentration in the final blend.
But consider pure alcohol. At molecular weight 46 it has a boiling point of about 174 deg F. (only at sea level) , far above what we would predict of a material of that low molecular weight. Propane, with a molecular weight of 44, is a gas! One can explain the high pure ethanol boiling point and low vapor pressure by the intermolecular forces due to hydrogen bonding between ethanol molecules. The hydrogen of one molecule and the electron pair on oxygen on a second molecule attract each other and additional energy - more heat - is required to separate the molecules to form a gas - to boil. And ethanol has a high dipole moment - a skewed electron distribution that establishes an additional intermolecular attraction.
Note that this boiling point stated above is only for anhydrous ethanol (without water). The ethanol that is used to blend gasoline is hydrous ethanol which contains 4 to 7 % water. Trying to get closer to anhydrous ethanol would make it much more expensive to manufacture.
But in hydrocarbon solution, the ethanol molecules are separated from each other by the preponderence of nonpolar, hydrocarbon molecules. Ethanol is soluble, but each polar, hydrogen bonding molecule cannot find the ready association with another ethanol molecule that increases boiling point and lower volatility. Its partial vapor pressure (and thus lower boiling point) is a lot higher than one would predict from Raoult's Law. This deviation from linear, "ideal" behavior that increases ethanol containing gasoline volatility, is a common phenomenon in chemistry.
This is probably getting to be much more technical than most of the people on this site want to hear about or know so I would just suggest that we just drop this direction of this thread.
Emery Stora
77 Kingsley
Santa Fe, NM
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