Hi on my 1970 4/4 the petrol tank is supported by two planks (for want of a better word) joined together by metal strips/bands.
The planks span between the chassis rails and the tank is bolted to this making it secure and also protecting the tank from impact from below.
My question is during a rebuild has anyone replaced the planks with another material. For example aluminium.
Would it make any difference if an alternative material used was thinner than the planks.
Would this impact on any part of the rebuild further down the line. Personally I can not see it making a difference but some of our more knowledgeable friends may know otherwise.
Was wood still used up to the recent change in chassis construction
If wood is reused during the rebuild what wood is best.

I've just moved by tank back about 30mm, and there are only four bolts holding it in. The wood is fairly thick - I'd say about 15 - 20mm and there is a hole towards the back for the tank drain plug. The thickness of the wood means that the drain plug does not protude further than the wood, which would mean the wood offers it some protection.

Personally I can't see any issue with changing the material as long as it retains the same structural rigidity, there is the same protection for the drain plug and the filler hose still fits ok. Sorry, don't know what the wood is, but it is 'wood' rather than 'ply'.

Being in two planks makes it possible to remove and refit the wood with the springs in place .... it's a bit of a jiggle but they go in (don't ask how I know )
A single piece would mean removing at least the rear bolts of the springs and lifting the axle a bit to refit. One nut and a screw each side and the planks split.... easy to replace them from underneath once it's all back in situ.

K

Certainly in 2005, the planks were angle cut, so they could be extracted diagonally.

Some time later.....………..maybe 2009...…..the planks were cut square and fitted in a cradle which then bolts to the chassis.

Dave ... mine's another '70s one .... just a couple of square cut hefty planks.

K

How about 18mm or 25mm Marine Plywood? , remembering to treat the edges first though

If I replaced with a alternative material to the
"planks" I would construct it in the the same manner i.e. with the split as I am aware that it can not be removed in one piece once the springs are bolted in place.
TBM has a valid point which I had not considered regarding exposing the drain plug when using a thinner material but is not insurmountable. Like him I will be moving the tank rearwards due to replacing five leaf springs with four leaf springs. (As in my previous post).
TBM is your tank sat flat on the boards or is it sat on spacers so that there is a space beneath it?

I don't think the standard planks they used were anything special, my original 1980's planks were rough-sawn pine held together with steel straps and the tank sat directly on them. They lasted fine until Kevin Vernon cut them out when fitting the new chassis. He replaced them with similar.

Apart from the point about protecting the drain plug, I wonder if there may be a degree of vibration absorption for the fuel tank. I can certainly see no reason to change to a different material, what would be the point?

Another good point to consider Tim H regarding the vibration absorption, thanks for that.
To clarify I wasn't after change for change sake. The timbers are original so 50 years old and to be fair still look to be in usable condition.
I was thinking that as the car is stripped down to the bare chassis it would be wise to replace them. If during the last 50 years another presumably better material has been discovered/invented I would adopt that. I am guessing that a big consideration in Morgans choice of using wooden planks in the first place would be cost rather than it being the most suitable material.

Interesting thread, having spent a few hours looking at how I'm going to fit my new tank in place. My ex racer had a bag tank fitted and was mounted on an ally frame. Going back to a standard size/layout tank, I need understand how they were originally fitted.

Do the two "planks" only bolt through the chassis side rails or was there also a cross rail that it bolted to along its front edge? (just as there is on its rear edge)