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Author Topic: Castor angle  (Read 273 times)
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davidwheeler
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« on: 09 May, 2018, 02:55:36 PM »

Since its front end rebuild after being attacked some 20 years ago, Old Boot has lacked self-centreing in the steering.   I have just made a gauge to measure castor angle (a plank with a cut out to go round the steering rods and a plumbline) and I find that Sheila, who steers beautifully since I rebuilt her front end has a correct castor of 3 degrees backwards (by chance I have to admit!) whereas Old Boot's pillars are vertical.   I remember reading a very long time ago that it is possible to adjust the castor by inserting packing between the rear mounting of the horizontal diagonal posterior strut and the chassis and I am looking at doing that.  The nuts are, of course, inaccessible. Though it is possible to remove the vertical bolt, I am currently unable to undo the horizontal ones.    Does anybody know if these latter sit in slotted holes and thus the brackets could be persuaded to move with a little judicious wedging or is it necessary to remove the studs and ream the holes?    Although it is possible to get at the front stud nut the stud itself turns with it (of course!).   The rear one is buried somewhere beneath the brake cable pulley though may be persuaded to move if I weld a bar to the head of the stud.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
davidwheeler
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« Reply #1 on: 10 May, 2018, 08:15:02 PM »

To answer my own query - I cut slots in the heads of the studs and so took them out.  There is no provision for adjustment.  Getting the castor angle right in the factory clearly depended on getting the  radiator frame just so.    I have inserted aome 4mm packing pieces which I calculate will give me the correct angle and shall bolt it all together anon making the holes to fit the studs including the attatchment of the diagonals to the radiator frame.   I am even more astonished I got it right with Sheila since I made an entirely new radiator frame (in rather thicker metal than the original).
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
Dikappa
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« Reply #2 on: 11 May, 2018, 06:02:06 PM »

The Lambda subframe has a 5 degree positive caster 'incorperated' in the design normally.  But I've seen quite a few distorted ones...
I'm currently trying to find out if the factory switched to thicker walled tubing at a certain point, as I have two suspension frames, one using 3mm walled tube, which is a late (8th series) frame.  The second frame I heve here uses much thinner walled tube.  However from the drawings or part numbers there is no evidence that the tubes were changed....
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davidwheeler
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« Reply #3 on: 13 May, 2018, 03:39:38 PM »

That may explain why the VIIth came out right as I set the radiator frame vertical by spirit level.    We shall see in due course whether my adjustments make any difference.    Cannot help with the tube thickness.
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David Wheeler.  Lambdas, Aprilia, Fulvia Sport.(formerly Appia and Thema as well).
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