thickness of alloy sheet for aux diesel tank

[gauci204]

hello gents. i have read through quite a few threads on long range tanks and aux tanks but havent quite got the info i am specifically after.

I am getting closer to finishing my alloy cage for the tray, and want to alter my headboard to reduce some weight by replacing the steel water tank i built into it, with a larger alloy tank. as well as this i want to add a aux tank between my tray and the chassis, but im not sure what thickness it will need to be, and whether im better with plain mill finish alloy, or checkerplate.

my initial thoughts were 3mm mill finish, but at 57kg/sheet, its not that much lighter than steel. will 2mm have enough meat on it for the bends and welds not to fatigue crack?

i have looked at the poly tanks, but i want to keep the weight as far forward as possible so i think custom welding one up will be my best bet. i have a space that is 1000mm x 950mm x 220mm but i dont need to fill it all with fuel capacity. ill probably only build a 70-80l tank for fuel, and possibly a 50-60l for water in the headboard.

so, what wall thickness will suffice, and any preference on type of alloy? i can get the 5005 mill sheet easily, but not all that cheap at $265/sheet.

thanks

chris

[mamiller]

I can offer some advice on the ally thickness in that if you fab a tank with baffles every 200mm or so that is of only about 70l capacity 2mm would be sufficiently strong enough to deal with the stresses applied to it by any 4wding you throw at it to old up at the corners and welds given the mounting points were tied into the tank sufficiently to avoid point loading and tearing the tank.
However we come back to the reason compressed air tanks (i know we are on diesel tanks here that arnt designed to hold pressure but stay with me) have to be the thickness they are (it is not because they need the strength tho contain the energy it is to provide a required thickness to deal with impacts and this is where im not sure if 2mm would be enough as a fair wack from a something may puncture it.

so given that reasoning id go with 3mm sheet ally or just stick with steel.
How can the ally be almost the same weight as the same thickness steel? at nearly 3 times the density of ally steel of the same volume will be 3 times the weight.

5005 grade ally would be fine for the use you have for it in the right thickness there is no benefit to checker plate for a tank other than to add weight.



Edit: had a bit about poly tanks but you have already looked into that

[gauci204]

thanks for the reply mamiller. i was always thinking 3mm, but didnt want to overkill if there was no need.

i am now seriously contemplating fabricating a full new alloy tray. i have priced up all the materials, and using 3mm rhs and shs, with 3mm treadplate for the tray, i can make a decently strong tray under 60kg, just not sure if i could handle Tig welding it all up.

in comparison to my chopped up cruiser tray which is in the vicinity of 250kgs i could have a full 100l water tank, and 100l diesel tank and still be lighter than i currently am (typically 2700kgs with a toolbox, and empty tray)

anyone in sydney with Alloy fab skills want to trade for some bobcat/excavator/tipper hire or asphalt work

[david875]

anyone with Alloy fab skills want to trade for some bobcat/excavator/tipper hire or asphalt work [/quote]
Would love to take you up with the trade offer but I am in Victoria. Dam dam dam.

[gauci204]

anyone with Alloy fab skills want to trade for some bobcat/excavator/tipper hire or asphalt work

Would love to take you up with the trade offer but I am in Victoria. Dam dam dam.[/quote]

ill send you the measurements

[Cowboy Dave]

I think he wants 3 dams dug out in return. Seems fair.

[gauci204]

he hasnt seen the plans im drawing up yet either. a few dams might not be out of the question

[david875]

he hasnt seen the plans im drawing up yet either. a few dams might not be out of the question
My gravel driveway is over 200 meters long and I could use a extra dam or two. Would be handy to run the boat down the back

[gauci204]

ok, i have pretty much decided to fab up a whole new tray and incorporate the water tank into the integral design of the tray/headboard, and then make up a fuel tank that i can bolt up underneath (figured a welded in job would be a pain to fix should it be required).

i was thinking of 3mm wall 75mm x 38mm for the outside frame and the main rails for the mounts, with 3mm wall 50mm x 50mm for the cross bracing and 3mm checker/tread plate. all of it will be in 6060/6061 alluminum.

can anyone advise if the 3mm will be thick enough for the frame of the tray or am in going to need to go a bit thicker? also am i better to use a "C" channel for the outside frame and main rails or will the 75*38 rhs be just as good?

the main reason for the tray is for my cape trip next year, so it wont be used to carry heavy stuff like the current steel tray is, i just want to save some weight whilst still having a decent tray. i will be fitting an alloy cage/frame with canvas canopy.

any help appreciated.

again, anyone willing to trade Fab work for Asphalt/concrete works and/or bobcat/excavator work let me know.

chris

[gauci204]

is C channel stronger than RHS or SHS for a given wall thickness or for a given weight?