Use of Oak in Restoration

I am looking at rebuilding a vehicle that has a timber underframe and have a large oak Beam that we have sourced from an old barn a local farmer has demolished, my query is that traditionally you would not use ferrous fixings in oak due to the timber corroding the fastenings so what are the ways of combating this the drawings state an oak underframe and the beam we have sourced will yield enough for more than one vehicle in time being 22ft long and 6" square

 

My experience, with Mk 1 Carriages is that they certainly used ferrous fixings through Oak. However, as the Mk 1's were only expected to be in use 25 years +/-, such corrosion would not have been a problem. However, what I am dealing with now is 60-70 years old Carriages where the 3/8" (10mm) bolts on the Corridor connection timbers, have not only rotted in themselves, but the original bolts/fixings are rarely 4-5mm in their existent form.

For replacements, we use BZP (Bright Zinc Plated) 10mm bolts, which should last, certainly beyond my lifetime. I don't envisage having to replace them a 'second' time.

If you really wanted any repairs to exist beyond your lifetime, and the lifetime of your Grandchildren, then A2 Stainless steel bolts are the solution, at a price.

But then the Oak would degrade prior to the fixings.

 

If you can use stainless steel as much possible.

Sawdust.

 

I've used green oak for underframes (the three waggons for Bowes Railway) - we painted the inside of the holes and painted the bolts before use.
E2A - and greased the bolts (ta for the reminder @gwalkeriow )

For seasoned oak it is not such a problem, but painting or galvanizing is likely to be needed for ferrous fixings. Or use brass / bronze or stainless, but these have a cost implication ...

Shipbuilders would use trenails or iron fixings for boats with substantial frames, for the lighter planking in yachts or lifeboats then copper nails and roves or bronze screws.

I've some images on Ipernity ...

 

We have used green oak for seven or is it eight wagon underframes with galvanised bolts with plenty of grease.

 

I find modern BZP screws corrode after a relatively short time. I suspect that the coating is very thin. I think A2 stainless is the answer even at a higher cost. My Father always greased screws heavily. I thought that this was messy but I am changing my mind as it certainly protects them and they come out much more easily. I also believe that holes for bolts in oak were charred. I suppose this neutralises the tannic acid.

 

Holcroft talks about rebuilding an elderly sandwich framed GWR loco while apprenticed at Wolverhampton, and notes that they did just that: the iron frames and oak blocks between were drilled, and then red hot iron rods were pushed through to char the wood, after which the components were bolted together.

(Locomotive Adventure, Vol 1 pg 33).

Tom

 

This is the newly retimbered frame for Snowplough 18 back in 2010
In Oak

 

When I've watched wagon solebars being changed at Allerton Bywater wagon shops they always used red hot pokers in the holes and the metalwork was always steel/iron. It amazed me how quickly the solebars could be changed on a wagon. All done in a day, albeit with a ready prepared replacement solebar.

 

I haven't had to do it but if I did I'd think about wrapping the bolt with ptfe tape (assuming it isn't a drive fit in the hole).

 

Actually, the reason for charring holes in timber is not just to protect the fixings, but also the timber. The reason is that various forms of rot can only attack timber - but not the charcoal that you get on the inside of the hole when you shove the red hot metal through. Charring wood like this was used to fit new shafts to things like long handled slashers and bill hooks, fireman's shovels and shunting poles. Just heat up the socket to a black heat, push the new handle in, and the socket will shape the wood to a perfect fit, and protect it from rot - even when used in situations as damp as lineside clearance or on steam loco footplates.

Some time back, amateur archaeologists dug up some hardwood stakes which had been sharpened at both ends, scorched in a fire, and driven into the bed of a river in a shallow stretch which could be forded on foot in the summer (can't remember the location, but I think it was in the Thames Valley area). The stakes had no other rot protection, such as wood pitch or paint, but were still perfectly sound.

At first the finders thought they might have been put in by the local Home Guard during WWII, as an anti-invasion defensive measure - but the local members of the HG who were still alive said they knew nothing about them - and didn't even know that stretch of the river could be forded. Eventually, they persuaded a museum to get the stakes carbon dated; to their amazement, the dating suggested that the stakes had been placed in the river bed during the Roman invasion of Britain, nearly 2,000 years ago!

 

I fit files to handles by heating the tang then driving it into the handle

 

Looking at the drawings I have for the coaches the sole bars are 4 x 2 section I'm concerned about the oak splitting given the relative thin nature of it has anyone any suggestions or alternative materials a steel underframe has been mused but would present serious design implications