Lock nut question

[Steve Bryant]

I have an application that will require two ny-lock nuts but since I'm pretty sure these weren't available in 1929, what would have been used? They will be visible once installed. These would be for a 5/16 BSF thread.
Thanks,
Stephen

[Tony Press]

I think early 'locknuts' were 'half' nuts.

[Greig Smith]

Double nut & Locktite

To look a little more authentic (& because we like to focus on details), 1 normal nut & one half nut locked against each other. Or castle nut & split pin

Or if you really wanted to use that nylock.... just add a half nut on top of it to disguise it. a careful wipe of sealer, epoxy putty or even window putty would disguise the curved top of the nylock below. Brush paint with ordinary air drying enamel

Aye
Greig

[Ruairidh Dunford]

Where are you using this, Steve?

[Chris KC]

Another popular option was to use castellated nuts and split pins; or plain nuts with locking tab washers.
As Ruairidh suggests, the best answer will depend to some extent on the application you have in mind.

[dickie65]

I re purpose big end nuts as they are usually very good quality and condition. You just need to add hole for a split pin.

[Steve Bryant]

In answer to Ruairidh's question I will try to explain my situation.
 
On my AD body the fuel tank goes through the "D" shaped hole in the firewall / bulkhead to be solidly mounted at the rear  to the bottom lip of the dashboard with two bolts and nuts. On the front face of the fuel tank at the bottom there are two flanges that are to be retained to the bulkhead with a bolt and nut (I think).  On my car there is a 1/4" gap between the flange and the bulkhead which if bolted tight would stress the tank and the bulkhead.
   

The tank is not insulated at all from vibration rubbing on the bulkhead opening and support lip which I don't particularly like at all. So I want to insulate the tank from rubbing and allow it some limited movement on the two new mounting studs I made with a soft rubber cushion on the stud between the bulkhead and the back of the tanks mounting flanges.
   
I would normally use a Nylok nut in this type of application to apply slight compression of the vibration cushion on the stud. The Nylok could be tightened or loosened as required and would stay in that state.

So I'm trying to establish what correct period lock nut would be used in this type of situation.
Cheers,
Stephen

[Howard Wright]

Hi Steve

On my RK and van (built from an AD tourer) the tank is bolted hard to the bulkhead by two 5/16 set screws with the hex head of the screw showing to the front. The tank sits on the ledge with a cork strip filler.

I’ve taken up any alignment problems at the back of the tank where it bolts to the dash by inserting a rubber washer.  You’re right to be worried about putting strain on the tank, they have a tendency to leak at the rear where the lugs are riveted and soldered to the thin steel of the tank.

Cheers

Howard

[Ruairidh Dunford]

You need to adjust the the rear mounting points so the tank fits flush at the front, there should be no gap.

I have seen evidence of felt tape all around the the edge with the front face on some every original cars.

[Colin Morgan]

Yes, on my car the tank was bolted in tight so there would be no movement - and so no wear.  (There was some felt tape, as mentioned above.)  If you cannot close the gap without stressing the tank, or alter it accordingly, I would suggest you might consider using a piece of solid packing of the right thickness to fill the gap - then there would be no movement where the tank passes through the bulkhead.