Calculating shear strength of bolts on corrugated roads

malmac

malmac

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Hi Team, We are installing a 2nd diesel tank for a vehicle which is going to see long distance travel on corrugated roads.

Shear strength for the bolts (10mm 8.8 bolts are the plan) is readily available. However the impact of corrugations must certainly increase the likelihood of failure from metal fatigue or coming loose. I would assume the coming loose is a question of torquing the bolt adequately - however the shear strength is an unknown to me.

Do any of you have any insights into this question.new diesel tank.jpg

Here is a rough diagram of how I would install the bosses for the bolts.

Thanks in advance.

Mal
 
With a tank in a SUV ,you wont have a problem......In a truck,there is a lot more impact load,but the tank will crack,the bolts will be OK........you should note you also have to comply with relevant ADRs.....
 
john.k is right, cracking is going to be the greater concern. OEM tanks are soft mounted, usually with a pair of straps. This allows the normal twisting behavior between frame rails to occur. In order to combat fatigue cracking, use as few mounts as possible, and make them soft. For example, I soft mounted a 100 gal transfer tank to a truck body using four 3/8" anchor bolts with valve springs as washers. It held up to off road work for years.
 
I second soft mount with straps. The stresses surrounding you hard mounts will crack the tank in short order.

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Originally it was a road paved paved with logs, laid crosswise. Stone roads when left unmaintained will develop a surface similar to ripples or corduroy fabric.
 
Down where I'm at we call them 'washboard' roads after the old washboards that were used to do laundry by hand.
 
They go on for kilometers. It's not like here. We went up to Mitchell Falls, all day. 8" deep. You know the advice, air down and speed up . From my experience of pounding gravel roads, use high quality six ply or better tires. Ripped shale and granite blastings are called gravel here.
 
Corrugated roads are the norm here in Australia. Mal the original poster is in Australia, and would be very familiar with them they destroy vehicles very quickly. They are named after corrugated iron which is a sheet building material usually rolled steel that is galvanized for weather resistance. The sheet is rolled with these corrugations much like a sine wave. On many country roads these corrugations can get quite large, and are very destructive to vehicles using them.
 
Thank you for the input. I was planning to have the tank with a rubber mounting system - but given the helpful comments, I am going back to the drawing board and thinking it through again.

Thanks for everyone's thoughts.

Mal
 
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