Talk Morgan Forums Morgan Sports Cars Morgan Three Wheeler & Super 3 Fuel Smell

Sounds like the tank mount weld crack to me too, only visible from the underside of the M3W.

Mini coopers, which can rode pretty rough with their “sport suspension” don’t seem to have fuel tank issues. They hang the pladtic(not sure the exact material but not metal) tank from metal straps. They use a rubber hosegoing to the fill cap. Seems like Morgan could benefit by this method.

Sure looks that way. Do all 3 Wheelers hard mount their tanks or did they ever strap mou t them?

They use L bend shape aluminium brackets welded onto the tank which bolt to the chassis for vertical support. They sit on rubber washers for the fwd end of the tank, which is where the weld fails and the seatbelt strap arrangements provide lateral & longitudinal support. The tanks also sit on a ply-board wooden structure which is bonded to the underside of the tank.

This can be seen on the parts list exploded diagrams

This photo (not mine) shows the strap arrangement well. It's imperative that this strap is kept taut or the tank will be allowed to flex up and down and the front bracket will almost certainly fracture, sometimes resulting in fuel leaks.


As Planenut mentioned, some of us have reinforced the rather flimsy L brackets that are welded to the tank with secondary aluminium brackets bonded over the originals.
Front bracket:

Lower bracket:


The take home message is to regularly check that your straps are correctly tensioned!

Mark, thanks for the explanation, and Andy the photos tell a lot about the design.

It appears that the tube frame does not extend to the rear completely and the front mounts and a tube extended part way back to the middle of the tank take the load. You are correct about the straps! If loose they allow the tank to pivot on the front mounts more freely. Box tubing would have less flex than round tube for that center tank support.

It makes one wonder why frame was not taken to the rear to hang thing like the tanks
.

I can't imagine ever designing a fuel tank to be so badly supported. No doubt it is an ingenious solution to a design problem but it does look rather "home built". Better, surely, to provide proper support.

Can't argue with that!

I bet it was for weight savings initially and they never envisioned people driving these machines many thousands of miles at speed over doubious roads but rather they probably envisioned driving around quaint villiages at slower speeds or on a track with controlled surface conditions. Motorcycles have a better grasp of fuel tank support.

I like that ingenious solution