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Old 19th April 2010, 11:30 PM   #41
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ok never mind I figured it out and got them to open. all these arms permit the tone arm to swing freely. this is exactly the action what Bo wanted to eliminate with the Cantus design. The Nottingham is however a beautiful execution of visual aesthetic. Thanks for posting the picture.
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Old 19th April 2010, 11:50 PM   #42
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Quote:
Originally Posted by moray james View Post
all these arms permit the tone arm to swing freely. this is exactly the action what Bo wanted to eliminate with the Cantus design.
You do realize the Cantus is a rather radical approach to tonearm design so you are not likely to another one like that, except the Statement TT1 arm by Clearaudio, who has a track record of curiously coincide with someone else's ideas. Surely there's a way to minimize the vertical seesaw action, right? Instead of V-groove bearing, can't we use regular cylindrical shaped bearing? Or even just some form of vertical fluid or magnetic damping in the vertical movement. I'm just trying to think of another way without using a rather delicate glass-tube. After all someone already thought of that idea so I want an alternative.

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Old 20th April 2010, 12:17 AM   #43
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I don't think that Rauna has had any real issues with the glass tube with respect to breakage and they are precision ground. Nothing to say you have to use glass you could machine and hone a metal tube to the same result. You could run two bearings outside of a precision ground tube but then you have to build a covering and when you use the inside of a tube it (the bearing and track) covers itself. Keeping the track clean is important. Designing the arm inside out would seem to be more complex than the way Bo did.
The use of the cylindrical roller bearings use in the current version of the Cantus is what makes the arm so rigid. The added friction in the horizontal plane is minimal and the extra contact points help the arm to better track a straight line. On a flat record the arm cannot rock there is no resonance because the system is non resonant. It is a very clever design. Motion is provided for the arm to track normal warps by means of the bearing races permitting the pivot point to slide enough to let the cartridge track the warp yet have no impact on horizontal motion.
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Old 20th April 2010, 01:51 AM   #44
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I think instead of V-groove bearing on a knife edge, we can use V-groove on a round rod to get similar stability. But the only thing is that when confronted with a warp record, the bearing will get pushed back instead of forward like the glass-tube. Just a thought.

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Old 20th April 2010, 02:41 AM   #45
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That's a good idea but again there is no reason that the tube has to be glass. Remember the larger the tube the more rigid it will be. You will still want to cover the assembly. Riding on the outside of a tube does not however provide the inherent ability to centre the trolley if it is pushed off balance by a severe warp whereas the inside of a tubes curvature forces the trolley always back down to centre at the bottom of the tube. All the same I like your idea.
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Old 20th April 2010, 07:41 AM   #46
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Quote:
Originally Posted by moray james View Post
the inside of a tubes curvature forces the trolley always back down to centre at the bottom of the tube.
I agree that riding inside a C shape has much better self centering effect, hence geometrically more accurate.

Moray, I want to thank you for providing so much information on this fascinating design, especially quotes from the designer. I am beginning to have a better understanding the designer's intention and at first it was a shock to the system to think frictionless free vertical motion is not always a good thing! It really does make me see tonearms in a different light. It makes me addressing issue that I was not aware of. I applaud him for thinking outside the box.... or glasstube. Thanks again.


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I am contemplating a simpler design from this Thales pivot-tangential arm.

Click the image to open in full size.

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Old 20th April 2010, 08:41 AM   #47
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Bo used to import the Sowther arm and was on very good terms with Lou. Lou's arm inspired Bo to make some improvements and the Cantus is the result of that. Lou sold his designs to Clear Audio and continued with them for some time. As far as I know Lou is still active but I don't know if he still does any work for Clear Audio.
As to the Tales arm well there are a lot of ways to skin a cat. Wonder what the moving mass is?
The more I look at the Cantus the more impressed I am with the thought that went into it. Simple is so complicated to do. Don't let the simple and plain Jane look of the Cantus fool you. The effort was not spared for the go but they did go easy on the show to make the arm affordable and that has to be commended. Unfortunately I feel the arm has not had the possible success that it might have had if it had the fit and finish of a Clear Audio Statement. Audiophiles cry for something wonderful for an affordable price but when it is handed to them they pass by because there is not enough flash and it can't be any good for that price. Oh well.
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Old 20th April 2010, 11:12 AM   #48
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Default Wow!

Can't anyone sleep 'round 'ere?

I've been up allt'night listening to you foreigners bickering!

You never know, I might even get a Cantus order soon, to pay for this 'call!!

LUVP.
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Old 20th April 2010, 07:21 PM   #49
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Quote:
Originally Posted by moray james View Post
As to the Tales arm well there are a lot of ways to skin a cat. Wonder what the moving mass is?
According to their website, the original version effective mass is 11g and the heavier AV version is 20g. Very reasonable mass as the the entire arm employs pivot bearings and uses NO linear motion bearing at all.

The most important thing is to understand the theory of the Thales circle.


Click the image to open in full size.



I have studied its design for a long time now and it's really ingenious from a geometric standpoint. The only thing that bothers me is to have a pivot bearing right above the stylus that might affect its rigidity and noise. The less linkages and bearings the better, from an engineering and economic standpoint.

I want to eliminate the rod from M to C which in this case is the armwand itself but if look closely, the guiding rod from B to C is the actual part of the triangle and is C is always 90 degree to A. Therefore, my aim is to figure out an arm that is capable of changing lenth for couple inches. It's a tall order but with inventiveness and patience I think there's a way. I already have something in mind but I don't want to post until it's more refined in its design. Just a jumble of ideas in the head.

Tonearms are really fun. Pentacone, we don't need to sleep.


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Old 21st April 2010, 11:41 AM   #50
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OK....Back to school. How is the groove made on the LP?

Come Back Good Bud!!
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