Nothing to lose really.

And today we played with the electric-glue-stick and the angry pixies. :)
Then we lathed the drive-plate assembly to within an inch of its life.
Then we inserted studs and cut them off to length, then we trimmed 'tother end to provide just enough thread protruding on the other side to put some fancy Stainless acorn-nuts on for S's & G's. :)
It looks like this.

I noticed that the trimming of the threaded centre boss/nut had perhaps introduced some hair-fine swarf into the threads and what had always been easy to do up/undo became a real challenge.:eek:
I managed to undo it and washed it out and then ran the tap through it a few times to clear the threads. All is OK again. :D
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I am just a tad "miffed".
I made all the parts to allow the drum hub backplates to "float" and kept them safe & sound with each set kept together on an M12 bolt and nut.
I started putting all the parts onto the frame and rear axle assembly and at the last minute when inserting the final half-shaft it occurred to me that some lube on the shaft (never a bad idea to lube one's shaft) would be a good idea.

Much to my horror, as I reached to replace the spray lube applicator the axle's angle dipped below horizontal and all the parts slid off and floor-wards.

One of which has not been recovered and may never be found. It spoilt my day.

Anyway, here it all is with just a bit of junk inserted instead of the custom part.

..... Missing part found! Planetary Disaster Averted.

20 minutes of swearing sweeping and grovelling around on the floor disclosed the location of the missing part from yesterday. Where? Yes, right at the back of the wall tight in the corner between wall and floor.
I had to coax it out from there with a hand brush. It could not have travelled any further than it did.
Hey @maddox & @Dale Rider .... I am restricted to using a roll-pin for my drive from the 2WD unit to the 12mm axle shafts..... is a 4mm solid pin better/worse than a roll-spring pin?
The axle is Silver steel 12mm Dia, and the 2WD unit's output boss is 40mm dia with a 12mm hole for the axle.
40mm x 4mm does sound a tad "light" but we shall live & learn I think.

Thanks for your considerations.

I'd go for a roll pin. That bit of spring will eliminate any gap. Without that spring a solid pin will use any gap to wear at the hole.
Thanks all for the input.
My "dull-witted" thinking was to use solid pins (probably strongest of the 2 options) that are unable to fall out because there is a keeper sleeve/clip over the outside covering both entry and exit paths for the pin.
I will see what I can get online. Thanks all. :)
I think I have found a decent "second" anchoring point for the SA Hub backplates. :)
There is a flat spot at right-angles to the axle at the root of the brake actuating lever area.

That means that the operating arm will still have plenty of travel before it has the remotest opportunity to be fouled by the 12mm stub.
Here is the same spot on the inside of the backplate. An M6 button head bolt will sit quite nicely there and screw into the M12 stub.

Given that many commercial trikes just have a single stub of 6mm poking into the anti-turn hole in the backplate tab, I think this will be better than that.
With the axle in position centralising the backplate and TWO fixing points preventing movement AND rotation I think this will be fine. (y)
But only if the 12mm stub is outside the circumference of the main axle-tube.
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Some of you may remember that I have an uncanny ability to snatch defeat from the jaws of victory. ;)

While checking to see that my proposed "second fixing point" would not cause any issues with the swing of the operating arm I was puzzled to find that one hub/backplate needed to move a lot further than the other before the brakes were applied. :(

On closer investigation it became apparent that there has been a missing part on that backplate from day 1 (which explained an uneven braking experience).
The missing part is a tiny "cap" that sits between the operating cam and the tip of the shoe. It is like a little "boot" designed to fit just right.
It is NOT a part you can buy, you can only buy replacement shoe kits or whole backplates, but not this part.

So I took some rudimentary measurements from the remaining one on that backplate and gave them to "lathe boy" who made me one in about 40 minutes today.

Now we have the mechanism complete and capable of working as intended.
The one on the left is the casting made by Sturmey Archer, the one on the right is the one made by me out of 4mm plate steel with a 4mm pocket milled into it.
My replacement is slightly over-length because round 4-flutes cannot cut square corners; but I have tried it on a wheel & hub and it works fine.



The fundamental issue is resolved and the fixing of the backplates can go ahead......... soon.
You do realise you can sell one's in thicker material to the velomobile boys to compensate for the shoes wearing down whilst still having plenty of material on them ?

You do realise you can sell one's in thicker material to the velomobile boys to compensate for the shoes wearing down whilst still having plenty of material on them ?

A lovely thought, but too much like hard work for "lathe-boy". Zee Germans would vant spessifications and paperz. ;)
Now I have gone and done it!
My pristine 90mm hub backplates now have a 6mm hole in them for a second anti-turn and centralisation fixing.
If this endeavour all falls flat all it means is a little 6mm plastic button-cap or a dollop of JB-Weld and some sanding to return them to standard though so all is not lost. :)
I finished the silly little stand-off stubs for the backplates today.
They are there to hold the backplate stationary for braking...while the axle& hub rotates.
Please pray for my soul.

The backplate mounts are now completed. :)
By "Completed" I only mean their key elements are all done; the tidying up and making "pretty" can wait till later (shaping making smaller etc. etc.).
Glad that's done because I was fighting-shy of the task of welding the stand-off studs in place.
So the next job is to attach these mounting plates to the outer tubes of the half-shaft assemblies.

Here is one of the backplates and its mounting plate sitting on a mock-up of the half-shaft tube & bearings.
You can see the two mounting bolts clearly (one on the SA backplates tab, and the other through the backplate near the shoe).

Here is the backplate mounting and the stand-offs.


The next difficult task will be to weld the mounting plates to the outer axle tubes without destroying the bearings inside. I think 3 "tacks" and then disassemble, remove the bearings and weld up fully, then refit the bearings.
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Oh Dear! :(

I placed one of the backplate mounts on the axle tube and welded it in place.
Now the tube has deformed sufficiently to make it difficult if not impossible to insert the bearings.
If I force a sacrificial bearing into place (for a test-fit) the deformation overall is sufficient to prevent the free-rotation of the inner race.
This is something of a disaster I feel.

Thinking cap on.
Update 13:37.
A vicious (but not un-provoked) attack with a grindstone in a rotary tool has fixed the issue. :)

Now on to side 2. :)
Update 15:30.
OK side 2 done now. Definitely the fugliest nastiest welds on planet Earth. My saving grace is that they only have to be stronger than the tyre 's ability to grip the road. ;-)

I put a wheel and half-shaft through and it was possible to turn the entire wheel etc. by finger & thumb pressure on the half-shaft at the 2WD unit location so the bearings etc. are still in decent alignment. :)
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Houston............. We have a problem! (No surprises there really).
I tried putting all the half-shafts, backplates and the 2WD unit in place as it will be in the final configuration.
Serious "binding" issues and on one side the half shaft just would not insert (despite the use of a very large "persuader").
It looks like something is scoring a line along the half-shaft as it is slid/pushed/hammered inwards.
It only takes the tinies bit of misalignment to totally kybosh it all it seems. :(
I found that despite almost getting there when the hub-shell reached the shoes it stopped totally.
This is a concentricity failure I think, so I will have to find out what has introduced it.
It may be as simple as a shim/washer to take a twist out of a backplate (I hope).

It does call into question the viability of the design because I would hate to try and pull these half-shafts out without a whole mess of tools around to attempt it.
Doing it at the roadside would be a nightmare I think. :(

Oh well, a lofty enterprise is still a good learning opportunity even if the outcome is not as one had hoped. We shall see, tomorrow is another day.
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