01-03-2022, 03:47 PM (This post was last modified: 01-03-2022, 04:50 PM by Belinni.)
Hi,
I was just about to fit a brake cross shaft to a chassis I have, when I noticed that the supports on the chassis rails do not have the bevelled edge that usually holds the swivel. The question is what is normally fitted between these type of supports and the cross shaft, is it just a piece of zinc ie without the swivel? And if so is the cross shaft still the same or do I need one that is a different diameter?
Thanks
See pic, note left is the bevelled one with the swivel, the right one has no bevelled edge to hold the swivel.
Thanks Ian, i might have to make up a couple of nylon bushes.
Does anyone have a photo of one of these semi Girling bushes? I’ve seen an exploded diagram but it’s hard to make out the bushes.
01-03-2022, 08:10 PM (This post was last modified: 01-03-2022, 08:12 PM by Hugh Barnes.)
One thing that is worth mentioning, do not make these bushes too 'snug'. They need a fair amount of play otherwise, when the chassis flexes, the cross shaft will bind in the supports...
They are made from strips of Zinc sheet, about 1/2" wide with a 1/16" flange from memory, rolled into a cylinder of the appropriate diameter. They are easy to make and the Zinc sheet not too hard to find, roofing specialists often have it in stock if you can't find it elsewhere.
If I understand it correctly, you are fitting an Austin cross shaft and Austin brakes to a later chassis that originally had Semi-Girling brakes. The Semi-Girling setup was introduced in mid 1936 with the ARR Ruby, and differs in several ways including the cross shaft and its bearings.
Fortunately, the chassis holes for the centre bearing bolts and outer bearing rivets stayed the same. I think your best bet would be to source some of the earlier spherical bearings/brackets and refurbish them. All three are different. The bearing bracket rivets can be drilled out and replaced with 1/4 inch BSF high tensile bolts and nyloc nuts. The centre bearing is a bolt-in affair, with slot holes in both the plate and the chassis so that fore-aft and up-down alignment can be achieved before tightening.
You are probably aware that the spherical inserts should be held quite firmly between the bevelled plates,with just enough movement to allow the shaft to align. The shaft rotates within thin zinc "top hat" liners. You don't want too much bearing play at the offside (driver's) end, or it will spoil the balance of forces between the rear brakes and the offside rear will be too enthusiastic.
An alternative would be to make custom bearings to adapt an Austin cross shaft to the semi-girling bearing brackets. Some people have used Delrin or similar for this .
In the recent past I have fully refurbished and fitted a semi-girling cross shaft. It's not a job for the faint hearted, and I spent a long time drawing up the various bits in order to work out where it all went. An unbelievable number of felt rings and washers ! My conclusion is that sourcing and refurbishing a semi-girling shaft to fit your chassis would be a much bigger job than sourcing the earlier Austin bearings/brackets or making custom bearings.
Thanks John, yes I came to the same conclusion and intend to fit a non semi Girling cross shaft and make up my own bearings on the chassis rails. I did think about drilling out and replacing the carrriers/brackets, but think I’d prefer to make a bearing. Brakes are bowdenex front and Austin rear.
I would be very interested to see what the semi Girling bearing looks like on the chassis rail carriers, if anyone is able to post a pic.
Here are two extracts from the scale drawing I prepared while sorting out my semi-girling setup. I'm no draughtsman, so don't expect full engineering drawing conventions ! The shaft is shown as viewed looking forwards, and the thin walled top hat bushes are shown in orange.
Semi Girling Cross Shaft Nearside.jpg (Size: 237.63 KB / Downloads: 126)
Turns out I had the answer to my own question! After rummaging around for something else I found a semi Girling cross shaft that I didn’t know I had!
Putting these pics up for anyone who in the future has the same question, or anyone interested.
I note that the wear on the shaft, compared to the normal type. I know the original wasn’t a great design but it did account for twisting of the chassis.
