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Author Topic: Augusta progress  (Read 535 times)
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JohnMillham
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« Reply #15 on: 10 December, 2019, 03:06:07 PM »



 I suspect the original method was to use some sort of cross bar clamp as there are two 8mm holes diametrically opposite in the crankcase flange although oddly there is not enough room on the back of the flange for the head of a standard bolt.



That's the way I do it, with a length of angle iron between the two holes, held in place with tapered nuts on studding. I also make sure the spring goes in the same way round each time, as well as everything else. A spiggot is also needed to centre the clutch plate. Please keep up the reporting, as it's very interesting.
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Mikenoangelo
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« Reply #16 on: 10 December, 2019, 10:24:23 PM »

Clutch removed last night without difficulty. As I suspected the spring is out of line. Iíll put some pictures on here tomorrow so you will understand how the clutch works - itís very ingenious and very lightly built, the clutch plate weighing almost nothing which no doubt contributes to the extraordinary ease of changing gear despite the absence of synchromesh.

The spring is not original, but of heavier wire, 8mm x 9mm rather than 8 x 8, perhaps to discourage slip. The clutch cover plate is a very thin pressing and it looks like the stronger spring is right on the limit of loading for the cover plate as it is a bit distorted.

The problem is that the spring is not very accurate and the coils which should seat in a lipped recess in the thin steel cover plate are too tight a fit so that the spring is canted over a couple of mm to one side. This does not affect the clutch plate, which rides independently on the gearbox input shaft between the box and the flywheel  but because the clutch thrust race is carried on a tripod of thin spring steel there seems to be a possibility that the thrust race housing is pushed more on one side than on the other. This in turn might cause the clutch plate to be squeezed more at one side of the axis at the instant of engagement which would put an asymmetric load on the front spigot of the input shaft. This could explain the wear on the spigot and perhaps allow the clutch plate to move a little off line before being trapped as the clutch finally engages so contributing to an imbalance and vibration. It could also explain why the vibration I am chasing is affected by pressing the clutch pedal. Just a theory!

In fact the clutch behaves perfectly as a clutch, taking up smoothly, never slipping and permitting easy reversing up hills. I canít fault it and the faces of the flywheel and the pressure plate are perfect and the lining absolutely unworn, flat and even.

Unless I can grind the existing spring to sit properly in the recess Iíll have to seek a new one from the supplier used by Dale Hicks a while ago.

Mike

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JohnMillham
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« Reply #17 on: 11 December, 2019, 10:35:54 AM »

I modified my Augusta's clutch by adding three small springs - a copy of Mike Wheeler's system because I found there was a tendency to slip after I fitted the blower.


* Augusta.clutch.spring2.jpg (22.22 KB, 359x292 - viewed 88 times.)
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Mikenoangelo
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« Reply #18 on: 11 December, 2019, 09:51:31 PM »

Here is the Augusta clutch. Top centre is the pressure plate (the disc) with the central boss which carries the clutch release bearing. Inside the bearing is the clutch release dog, mounted on a  hollow shaft with a nut on the inner end which is pulled back by the action of the clutch pedal and via the thrust bearing pushes the pressure plate back away from the lining to disengage the clutch. The pressure plate unit is fixed to the flywheel by the three spring steel arms which flex to allow the plate to move away from the flywheel.

The spigot shaft, not shown, goes through the hollow centre shaft, is splined to the clutch plate and aligned by the gearbox input shaft between flywheel and box.

Top left is the cover plate, a very thin steel pressing, attached to the flywheel by three bolts, which compresses the spring against the central boss of the pressure plate unit.

The flywheel, most unusually does not fit to a taper on the crankshaft but is held in place and driven by four bolts which screw into the end of the crank - they are strong! Iíve seen that many of the components have a small round indent, showing that they were routinely tested for hardness, and this includes the four bolts.

Today I have made a fixture to prevent the flywheel from rotating while I undo the four flywheel bolts to replace the centre spigot ball race. I work on my own, often for a couple of hours in the evening so I donít have a handy assistant.

Mike




* 16 Clutch components.jpg (120.99 KB, 640x480 - viewed 66 times.)

* 18 Flywheel locking plate.jpg (132.6 KB, 640x480 - viewed 21 times.)
« Last Edit: Yesterday at 09:03:24 PM by Mikenoangelo » Logged
Kari
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« Reply #19 on: Yesterday at 01:08:59 PM »

On the last photo, I note that the friction plate is of a different construction as the original, which is made from aluminium, slotted and wavy. The linings are attached alternating to the front or rear of the plate. The original assembly has a weak point, that are the rivets who attach the plate to the splined hub. They can become loose allowing the hub to move on the plate, resulting in elongating the holes. The one of Mike's Augusta seems to have those rivets spaced on a greater radius.

Karl


* IMG_1252.JPG (1653.79 KB, 3264x2448 - viewed 0 times.)
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Mikenoangelo
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« Reply #20 on: Yesterday at 07:50:58 PM »

My clutch plate is certainly different to Karlís as the disc is steel rather than aluminium. It all looks fairly new and the riveting is really tidy, so perhaps having found that aluminium is a bit weak the previous owner substituted a steel version, or did the later cars use a steel plate (mine is 1936)?  With the cut out holes just inward of the lining it looks like a very professional job. See photo 16 above. The part behind the lining is wavy as it should be. . The more I look at this the more I suspect that it is a clutch plate from some other source rather than a specially made replacement but as I said it works perfectly.

There are other differences - the rivets attaching the linings are all on 133mm, not alternating diameters as in Karlís photo. The centre boss of mine does not have the cylindrical flange seen on yours Karl. The rivets fixing the centre boss are on 43 mm diameter.


* 17. My clutch.jpg (108.52 KB, 640x480 - viewed 27 times.)
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