Roof comes off

… A slightly retrogressive step… taking the roof off. The weather is improving, spring is on its way (or at least it isn’t going to snow again down here) and thoughts are turning to actually getting the Landy on the road.

To do this, the roof needs to come off to get the vehicle out of the diminutive garage door.

In a fit of brilliance whilst lying awake in the early hours of this morning I thought about fitting original Land Rover leaf springs and be done with it.

This would perhaps lower the ride height sufficiently to fit through the door… If not, I’ve wasted a lot of time fitting  new springs and would never feel the benefit of the funky Canadian parabolics.

So, the rear door and roof have to come off and nearer Easter, will be re-fitted whilst on the driveway. Hopefully there won’t be any significant mechanical problems after this point as I don’t fancy doing them on the drive… and I’m not entirely sure if I’m actually allowed to do them on the drive.

 

 

 

 

Cold Welding / Galling

Now…. I had to look this up… but I have at least something this afternoon.

For as along as I can remember, undoing stainless nuts and bolts often resulted in the nut seizing on the thread of the bolt. It was more common with nyloc nuts.

The only way to release the pair was to force them until the shaft of the bolt shears or cut them off. Smaller diameter bolts can be sheared by hand, larger bolts would have to cut with the grinder or hacksaw… unless you’re Popeye. Not ideal in a confined space.

This seizure is called cold welding or galling. Cold welding occurs during installation / extraction when pressure and friction cause the bolt threads to seize to the threads of the nut. It occurs typically in stainless, titanium, aluminium… in-fact anything except hardened and or galvanised nuts and bolts.

When exposed to air and moisture, stainless steel (and any other metal) will form a very thin film of oxide (rust) on the surface. This offers some protection against cold welding as it reduces friction.

However, if a nut is driven down the thread very quickly (with a power tool), or a nyloc nut is used, heat and friction quickly build up, the oxide removed and the relatively soft materials mechanically bond together.

At a microscopic level, the surface of the threads have small ridges on them. In normal conditions, this presents no problem and nuts will happily wind down threads. If heat and friction are introduced, the tops of these ridges will shear off, creating more friction and heat. The cycle continues with more shearing and locking until the threads are destroyed and the fastener will no longer turn in either direction.

The process is compounded by the depth and pitch of the thread. Fine threads are more susceptible to cold welding than course threads… and I’m using stainless steel BSF nuts and bolts… British Standard Fine. Enough said.

In future I will use a dab of copper slip on the threads.