Author Topic: Clutch Operating Lever  (Read 492 times)

Offline UKlittleguns

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Clutch Operating Lever
« on: 13.05. 2020 17:26 »
Hi Everybody,

What's the best initial angle setting between the clutch operating lever and the internal small lever that pushes the clutch release shaft.  Is it simply zero?  They fit together on a very fine set of splines which suggests some adjustment might be needed.  Never had the original parts so starting from scratch with replacement bits.  There is the adjustment screw on the small lever but don't think it will compensate for any gross errors.  I'd like to get somewhere close as changing it later looks like real pain.

Thanks and regards to all.
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Online bsa-bill

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Re: Clutch Operating Lever
« Reply #1 on: 13.05. 2020 18:43 »
I have the lever at roughly a right angle to the pushrod when it's halfway along it's travel, it's one of those  ones that you may never get exact but it's not really that much of an issue
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Re: Clutch Operating Lever
« Reply #2 on: 13.05. 2020 18:53 »
I made a mistake with mine when fitting the rrt2 and had to alter it when in situ, your right it is awkward but possible, when the clutch is disengaged the arm needs to be parallel to the gearbox so I would set it the same , then the ball and push rod are not trying to work against each other at a bad angle
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Online muskrat

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Re: Clutch Operating Lever
« Reply #3 on: 13.05. 2020 21:23 »
G'day Gunny.
The  arm at rest should be a little outbound of the cover so when the hand lever is pulled in the arm is level with the cover. Then it's a case of the inner arm being at 90 degrees to the rod when the hand lever is pulled in. On mine the adjusting screw and locknut show about 2 threads when locked up. You may need to move the small arm on the spline to get it close then use the adjuster to get it right.
Cheers
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Online RDfella

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Re: Clutch Operating Lever
« Reply #4 on: 14.05. 2020 12:16 »
As far as I can see, people are suggesting the small lever behind the inspection cover should be at 90* to the pushrod. I disagree. Given a picture is allegedly worth a thousands words, I drew a rough sketch. The top part shows what I presume people are suggesting, with the arms pivoting at point A. Trouble is, in this configuration the leverage to the pushrod is invariably nowhere near 90*. The internal short arm is actually irrelevant because the ‘lever’ is in fact a line drawn between hinge point A and the ball. In a worse case scenario, that’s more like 130* (depending on how far the adjuster is screwed in). As a result, when setting up these clutch parts I try to achieve 90* between hinge, ball and pushrod, which usually necessitates setting that internal arm outwards a little (bottom sketch). Making sure the pushrod is as long as possible assists too by keeping the adjuster back.
On these clutches you need to achieve all the clutch plate separation possible and, as they say. ‘every little helps’.
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Offline UKlittleguns

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Re: Clutch Operating Lever
« Reply #5 on: 14.05. 2020 16:59 »
Hi Everybody,

Thanks for all your comments.  Very helpful.  After no end of trial fits I realized the answer for an initial setting is in the Haynes manual!  Nothing in the text but Fig 22 on page 63 gives the answer.  You have to look at it very closely.  It's obviously the reproduction of a factory diagram so should be accurate.  Item 26, the clutch operating arm and item 27 the lever, are not parallel.  Look again.  The clutch arm is leading the lever in a clockwise direction.   Set mine away from parallel by one spline and it seems to match everyone's advice.  Given the adjustment at each end of the clutch push rod I'm sure it'll work *smile*   

 
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Re: Clutch Operating Lever
« Reply #6 on: 14.05. 2020 19:15 »
Apologies if I confused anyone with my sketch whilst trying to clarify the leverage issues. I thought laying it out that way would be clearer whereas, of course,  in real life both levers are on the same side as the hinge point. As you can see in the pic of one of my BSA boxes, and as UKlittleguns has identified, the inner leaver needs to 'hang out a little' from the clutch arm attached to the cable.
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Online chaterlea25

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Re: Clutch Operating Lever
« Reply #7 on: 14.05. 2020 19:21 »
HI RD
Is that photo with the clutch pulled in or out (slack) ?
If it is with the clutch pulled in then the adjuster is forcing the pushrod to one side ?????

John
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Re: Clutch Operating Lever
« Reply #8 on: 14.05. 2020 19:35 »
if it isn't pulled in it's at the wrong angle anyway *fight* *fight*
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Online RDfella

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Re: Clutch Operating Lever
« Reply #9 on: 14.05. 2020 20:25 »
No, it's not pulled in and yes, it's the correct angle - the clutch lever just under 90* with the cable and the inner the same with the pushrod.  Remember - as my sketch outlined - the actual angle of the clutch push rod lever to pushrod is irrelevant. The angle that matters is between a line from the centre of the pivot point to the outer end of the ball and the pushrod.  You need to aim for 90* roughly mid clutch travel to gaim maximum travel and leverage. Simple trigonometry.
Of course, John is right about the ball not being in the centre of the pushrod with clutch engaged, but it never can be in both clutch positions. A similar situation exists with valves and rockers and, indeed, most car clutches before the advent of slave cylinders around the 1st motion shaft. There are invariably compromises to be made in engineering. In this case, the amount of off-centre compared with the length of the pushrod makes such a tiny angle that any sideays force would be miniscule.
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Online chaterlea25

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Re: Clutch Operating Lever
« Reply #10 on: 14.05. 2020 21:59 »
Hi All
Without getting into the nth degree of trigonometry or starting an argument, here is my pennyworth and it works for me
Maximum movement of the pushrod occurs when the pusher arcs through 90 degrees to the pushrod
Imagine movement from twenty five past the hour through half past and onto twenty five to
The same applies to the external clutch arm , 85- 90-95 degree angle sweep

John

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Re: Clutch Operating Lever
« Reply #11 on: 14.05. 2020 22:37 »
thick me , but don't you find that how it is set up it puts strain on the cable where it fits in the arm when it is pulled in *conf2*
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Online RDfella

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Re: Clutch Operating Lever
« Reply #12 on: 15.05. 2020 10:18 »
John has hit the nail on the head – 90* is the magic number. Maybe I confused people (wouldn’t be the first time) by trying to explain where that 90* should be measured.
And no, Berger – thick you’re definitely not.

As mentioned ages ago, I often find it difficult deciding where to pitch an explanation, given the wide variety of knowledge / ability between members on this forum. 
At the risk of further confusion, here’s the fuller explanation of my thoughts, which I was trying to avoid earlier…….

In order to hide from his wife the fact his girlfriend was in the office, a director might designate her as part of the ‘design team’. At least that’s what we assumed when we used to describe a particularly poor design as ‘designed by the director’s girlfriend’. I’m afraid BSA’s clutch falls into that category.
For a start, you have a hard ball, bearing on the hardened end of a shaft, with the shaft’s other (hardened) end bearing on a hard stud in the pressure plate. All with scotch mist for lubrication. Bad engineering and no wonder it’s not unusual to find the ball is worn flat or there’s a deep hollow in the ‘actuating cap’ centre. The rest of the mechanism is sadly not much better.
First, the clutch arm / cable angle. I set my levers (I have four bikes with these boxes) to be just under that angle with clutch engaged and just over when disengaged. Having 90* at mid point gives the longest period of best leverage with maximum travel of the clutch push rod. I believe this is the point John was making.
Secondly, that little clutch pushrod lever on the end of the clutch arm spindle. Again, for maximum travel of the push rod and to minimise the amount the ball wipes across its face, 90* is again the magic angle. As explained in previous posts, this is not achieved when the pushrod lever is at 90* with the pushrod, but rather when that angle exists between the pushrod and a line drawn between where the ball touches the rod and the centre of the clutch arm spindle. Because of the poor design, this may mean the ball is not in the centre of the pushrod, but we’re working with what we’ve got and so the ‘cleanest dirty shirt’ principle applies. Is it better to have the ball in the centre (though it won’t stay there as it wipes across the rod end face during use) but pushing sideways on the pushrod because the angle is nowhere near 90*, or is it better to have 90* but the ball not central on the rod? I prefer the latter, as the force is pushing directly along the line of the rod with virtually nil sideways thrust.
Finally, again as referred to in previous posts, the best way of minimising this grief is to keep the ball as close to the pushrod lever as possible. This can only be achieved by having the pushrod as long as possible (I cut ¼” silver steel to length and harden the ends) but there is a downside – as the clutch wears there’s little if any adjustment available (letting the clutch arm out a little to compensate defeats the purpose). Had the adjustment been at the clutch pressure plate instead, most of this grief would have been avoided. Did directors have girlfriends in their offices in the 30’s when these designs were dreamt up?
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Offline UKlittleguns

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Re: Clutch Operating Lever
« Reply #13 on: 15.05. 2020 12:20 »
Hi RD,

Thanks for posting the excellent picture of your clutch operating arm and lever position.  It's exactly how I finally set mine so am very reassured.  If Haynes had such clear pictures I wouldn't have asked my question in the first place.  I believe that once the off-set angle between the lever and arm is set, the angle of contact between the lever and push rod is then a matter of adjustment on the screws at each end of the push rod and possibly a matter of personal choice.  I personally think the clutch was designed at the office Christmas party where good laughter is essential *smile*   
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Online cyclobutch

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Re: Clutch Operating Lever
« Reply #14 on: 15.05. 2020 15:45 »
Comment from a pal I shared this with;

"Sorry not impressed.. I have looked upon a Silk Clutch.. & if the above clutch actuator was designed by Mr BSA's girlfriend, the one on the silk was from the pen of Mr Silk's Pet Monkey & we aren't talking an intelligent primate like a Chimp"
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