PETROL TANK MOUNTING

[Dennis Nicholas]

Hi all.  Need some thoughts on mounting my Nippy petrol tank on the extended chassis frame I have built under the boot area.
This picture shows the bracket bolted to the tank. Bracket 3mm steel plate.

   

This shows an edge on of the bracket

   

This shows the chassis extension with the plate at the rear corner (4 holes) that the above bracket bolts onto.

   

With the tank/brackets bolted to the chassis extension the bracket size and shape has been arranged such that the tank is as high up as is possible. (I have previously used the Nippy in MCC trials and wanted to ensure max ground clearance).
The chassis extension is not completely rigid such that if you press down at either rear corner that corner will (together with the rest of the chassis) move downwards a little while the other corner stays up......ie the tank ends would be subject to a bending force through the brackets and the tank bracket.
I am wondering whether to put a medium soft rubber block between the bracket and where it bolts to the bracket welded to the tank so as to take distortion away from the tank ends.  If so what hardness of rubber and what thickness? I would obviously have to shorten the bracket between tank and chassis extension by the thickness of the rubber block.
The rest of the chassis remains the usual A7 flexible affair.

Your thoughts welcome.

Dennis

[bob46320]

For my money, the extention bracket will put so much load onto the rear of the original chassis extenders that you will experience a fracture at that point - especially if you are into trials. I can see that you have stiffened up the original extensions, so lets hope that that will be enough.

[Dennis Nicholas]

Yes the original flimsy extension did crack just beside where spring goes into main chassis and hence the beefing up.

   

If anything round there goes again I will stamp my foot and utter TISH TISH

Am more worried now about distortion bending the end panels of the tank and cracking them.  I am thinking of getting a stainless petrol tank made.

At least the B pillar and associated body around should not fracture and has not to date.

[Colin Reed]

Hi Dennis,
I would be inclined to Fit Rubber Anti-Vibration mounts between bracket and tank which means shortening Bracket.
These are the round type with stud on either side.
Fitting rubber between tank and bracket will not allow any movement once tightened up,
Changing the type of material that the tank is made will have no influence on the twisting.

Just my Opinion
Colin
NZ

[stuartu]

Dennis, I agree with Colin that anti vibration mounts have merit but I would point out that, in my experience, they are good in compression, passable in shear for an exhaust mount but don't last too long in tension. If I were going down the rubber bobbin route, I might extend the 3mm steel brackets to sit under the original mountings on the tank like a hook with the anti vibration mounts sandwiched between the bracket and the mount on the tank. Just a suggestion.
Regards, Stuart

[Robert Leigh]

May I suggest shortening the brackets to maintain the position you want, with longer bolts and thick rubber washers between a flat washer under the bolt heads, another between the bracket and the tank, with a third the other side of the tank mounted bracket with another flat washer and a self locking nut. This will require longer bolts but will give the slight flexibility you are seeking. The rubber washers might well be made from synthetic rubber gasket material available from engineering suppliers, say 4 to 6 mm thick.
Robert Leigh

[Dennis Nicholas]

Thanks all replies.
I will most likely go down the route of lengthening brackets so they hook under tank bracket with rubber between the two brackets and with bolts and nylocks just bringing the three together...ie not tight.

The choice of stainless for a new tank is because I already have 3 copper patches soldered on the old tank 

Dennis