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Old 4th May 2010, 03:23 PM   #101
wjlamp is offline wjlamp  Greece
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Quote:
Originally Posted by Nanook View Post
perhaps something like this, except with a solid "tube"
Going external,it would be easier with a calibrated s/s rod,which is perfectly dimensioned,externally,and bearings made of industrial plastics, eg Ertalon.

B.L.
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Old 4th May 2010, 03:25 PM   #102
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.
If the rollers are riding on the outside of the tube, then why not just use TWO U-groove bearings riding on a rod? It's certainly cheaper and simpler that way.

.

Click the image to open in full size.

.
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Old 4th May 2010, 03:32 PM   #103
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Hi all,

Been following this with interest.

I have sketched out some ideas (good old pencil on the back of an envelope).
Using 3 bearings on an inverted channel, 2 on the front face wide spaced, 1 on the back face central, with separate knife edge/single points for the up/down.

Inspiration is the Trans-Fi Audio - Terminator Tonearm

John.
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Old 4th May 2010, 03:42 PM   #104
wjlamp is offline wjlamp  Greece
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Quote:
Originally Posted by directdriver View Post
.
If the rollers are riding on the outside of the tube, then why not just use TWO U-groove bearings riding on a rod? It's certainly cheaper and simpler that way.

.

Click the image to open in full size.

.
And use a Teflon rod ,with all the benefits.Excellent idea.Less glitzy,than the glass tube,perhaps,but more easy,for DIY.
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Old 4th May 2010, 08:00 PM   #105
dtut is offline dtut  United States
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This Opus clone was cobbled together as a proof of concept project and this is its Initial Public Exposure. Obviously, without PVC and blue masking tape, I'd never be able to build anything so, again, what EC8010 called "rustic."

The bearings are $5/pair remote control model car parts. I removed the seals and lubricant so they roll more freely. The PVC interior is highly polished. Horizontal movement (rolling bearings) is quite good - no hitches or stuttering as long as the record is clean. This arm does not like dirty records. Vertical movement (sliding bearings) of the arm is stiff. Setting the VTF is difficult and, although the arm does follow warps, the stylus winds up doing a lot of the work. The polished glass tube and carefully chosen bearings would help. Figuring out the arm mass and relative weights of head shell and counter balance was trial and error. I probably didn't get optimal results.

Regardless, it works and it's definitely DIY possible.

The sound has a remarkable presence and is very enjoyable with a deep 3D stage and the best bass - detailed and musical - I've ever heard from my system. The sound is transparent so voices and instruments are clearly delineated.

After seeing the Opus pictures, I just couldn't help myself. It's encouraging to have obsessions turn out well.
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Old 4th May 2010, 11:16 PM   #106
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Doug: nice knock up. I do like the spirit level nice touch. Clear Audio make the "STATEMENT" yours might be what you can afford to build after the divorce so perhaps we should call it the "SETTLEMENT".
Try giving the trolley assembly a degree or two of downward tilt to provide a little help to make things roll along easily. Great to hear that it works and sounds so good.
Is it good enough to temp you to give up on the thread suspension arm that you have been working on? I can't quite make out from the picture but one of those tip mounted record brushed might provide a tad extra trolley drive and also provide some relief for the cantilever and its suspension. Nice job Doug I am sure that this will inspire some other folks to try some ideas out. Do you think you might be talked int trying out a metal tube for comparison? Thank you for posting your pictures. Best regards Moray James.
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Old 4th May 2010, 11:47 PM   #107
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Doug I just had a simpler idea to check out friction of the PVC tube. Make a little dam at the end of the tube with putty or the like and with an eye dropper insert just enough alcohol to wet the bottom of the tube. Single Malt Whiskey works best for me but that seems such a waste. Running wet should reduce overall friction quite a bit and you can see if there is any significant improvement. Faster and easier than building a metal tube. Regards Moray James.
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Old 5th May 2010, 12:44 AM   #108
dtut is offline dtut  United States
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Moray,

She got the Hi Fi, I got the tube - something like that?

Thanks. I hope others will take a shot at an Opus clone, but I also hope that some of the other ingenious ideas and approaches from this thread will become working models - like BillG's glass-lined V trough. Part of doing my half-assed builds is to show it doesn't take an engineering degree and fully-staffed machine shop to produce something workable and rewarding. Funky materials and a home shop are just fine for a first approximation. Big bucks and obsessive precision can come later, if they're justified.

I noticed, looking down the tube, that a bit of trolley angle - either for or aft - might help, but I haven't quite figured it out yet. The cartridge is a Shure w/dust brush. I thought it might help with lateral movement, but I've tried the arm with the brush up and down and didn't notice any difference.

I'm still working on the string arm - that's my baby and it still has some growing up to do yet.



I've got copper tubing that's the right diameter, but that's for another day. In the meantime, I'll try the alcohol idea and report back. If I ever make a Schroeder quality version of this thing maybe I'll consider putting single malt in it, but not 'til then.
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Old 5th May 2010, 02:27 AM   #109
Pano is offline Pano  United States
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Quote:
Originally Posted by directdriver View Post
.
If the rollers are riding on the outside of the tube, then why not just use TWO U-groove bearings riding on a rod?
Well, um, yes. Hehe, of course! I did think of that and completely forgot about it. Silly, really, as I had to do something similar for a big sliding repo camera rig. 2 rails instead of 1.

I like Doug's effort a lot. But I was thinking about the bearings on the top of the rod (v-bearings, of course) and just a normal pivot for vertical. Don't know if it would be any better, but it might.

Some fun thinking going on here, and some nice building, too.
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Old 5th May 2010, 05:54 AM   #110
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When I discussed the normal vertical pivot idea with Bo he was adamant that that was one of the things which Lou Souther had done and that the arm worked better without the free swing pivot because it would resonate and also because it was not as rigid in other words there was too much loss of energy with a free swing vertical pivot. The free pivot will work well it's just that the more rigid version works better. You can see which version Clear Audio chose for their top of the line arm just as Bo did for the same reasons. Too bad CA did not come up with an original idea but at least they chose the better working one. I think that pretty much tells the story.
With respect to inside Vs outside for bearing position well it is the same deal outside you are trying to keep the arm balanced with gravity looking to pull it off balance. Inside of the tube the trolley can ride up the wall (to permit the cartridge to ride a warp) but gravity pulls it back down to centre position for you. Its not a free lunch but it's as close to one as you are ever going to get. The more you look at it Cantus is a very clever design. Regards Moray James.
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Last edited by moray james; 5th May 2010 at 05:57 AM.
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