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doyle
25th October 2009, 11:52
Well the project has been put on hold until I procure additional funds and its starting to get cold here in Mi.

As I'm staring at the bike I like the look of having extra space behind the motor for stash or tools. So I'm soliciting opinions if I'm out of my mind by putting my oil tank under the gas tank.

The way I mounted the tank I have quite a lot of space under it,
http://i233.photobucket.com/albums/ee21/Saabnobb/1972%20Sportster/IMG_3110.jpg
http://i233.photobucket.com/albums/ee21/Saabnobb/1972%20Sportster/IMG_3113.jpg
I got a guy that fabricates tanks will do it for me, (I powdercoated a bunch of stuff for his vintage Chris Craft)
Here is the design that I'm thinking of, calculated the volume to be 2.8 quarts to the top return.
http://i233.photobucket.com/albums/ee21/Saabnobb/1972%20Sportster/sportyoiltank10-23-09.jpg
Opinions welcomed

Thanks
doyle

NC_REDNECK_1981
25th October 2009, 12:01
its your bike if you want it go for it. i have never seen one like that so it would definately be different.

IronHead78
25th October 2009, 13:50
How well will your wiring harness fit along the frame tube after installing this tank? Other then that I don't see any reason it would not work, you would need an external oil filter.

AB,Frank
25th October 2009, 14:45
I'm just wondering if there would be an heat issue...just saying.

meanmechanic
25th October 2009, 15:04
The oil tank will sometimes get to 200 degrees. You want that heating up your gastank and the gas inside? That is a lot of room between those tanks though.

Schutzhund
25th October 2009, 15:19
The oil tank heating up the gas could be a concern, maybe would be controled with an oil cooler. The wiring could be run through the frame. It's a novel idea, but what would be the oil capacity be. Have you figured out the volume of the space?

Fe Head
25th October 2009, 15:20
Very novel approach.

As for the heat transfering to the gas tank - leave enough space to add some thin insulation having the aluminium shiny reflective side facing the black oil tank.

It will keep the gasoline from absorbing too much of the oil's radiant heat.

To assist in cooling the oil tank buy a thin sheet(s) of 20 -22 guage copper. It is a little expensive but worth the effort IMO.

Place /mold the sheet of copper along all of the bottom and up the sides - the higher the better - making sure it is as tight to the oil tank's surface. Some spray on glue or white heat sink paste may be helpful.

However you do it make sure the copper up the sides is continuous with the bottom for the best conduction of the heat to the bottom where the fresh air is.

If the cost is not overly prohibitive you can dramatically increase the cooling effect when you make a series of longitudinal " V " shaped folds 1/2 to 3/4 of an inch high/deep on the bottom surface.

Next to German silver, copper is one of the best heat conductors commercially available.

These are just a few little additions that will ensure the oil does not over heat itself or the gasoline next to it.

All the best as you complete the fabrication please let us know how the final setup works.


Cheers;

Gone
25th October 2009, 15:35
great idea. i too am lokin for an alternative tank location. let us know how it goes, you will have plenty of time to figger it out with our lovely weather

1976 XL
25th October 2009, 16:20
How will you fill\check the oil levels? Won't the filler be under the dash\speedo? Also won't the tank be in the way of the speedo cable?

meanmechanic
25th October 2009, 16:24
I think maybe you should get a 2 piece gastank w\one side the oiltank like the old days. You are putting a oiltank in a confined area w\little or no air flow. It will heat up any insulation you put in there and heat the gastank. So you run a cooler for the oil-you get it down to say 175. It's still too hot at 150. Of course you got the additional engine heat going up there too. You might as well put in a larger backbone for the frame and run the oil in there. I have that space under my tank also-welded up the front so I don't see it. Oil tank in stock location out in the wind.

1976 XL
25th October 2009, 16:36
+1 on Meanmechanics idea. Split tanks will give you the look you want, with less fabbing. Although you won't have the capacity for fuel as before, but it would seem to have less problems with other stuff(speedo, cooling, filling, etc.).

doyle
25th October 2009, 17:29
Thanks for all the replies and suggestions.

The volume of the tank will be about 2.8 quarts is this enough? The plan is to remove the mount for the speedo and run speedo on the handlebars. I'll fill and check the oil through the top of the tank. I would also like to put the old style glass oil filter over the battery at the original tank location. Something like this.
http://i240.photobucket.com/albums/ff317/nitropathic/IMG_0032.jpg

Heat was my first concern also and the plan was to run a external cooler, is there any one better then an other.

Thanks
doyle

1976 XL
25th October 2009, 20:23
Looks like you have thought through most of the factors here Doyle. I say go for it. It will be original. Let us know how it works and looks(more pics). Oh yeah my original tank is a 3quart I believe, and with a cooler, extra line, glass filter, etc. I don't think volume will be a factor at 2.8 quart.