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Old 23rd April 2012, 11:23 PM   #401
dtut is offline dtut  United States
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Hello all,

Very good news all around. Fran, I checked out your video. That's a handsome LT and it performs excellently. I like the straight ahead styling, it's very effective.

I'm delighted/relieved the ceramic bearings worked for everybody. I ordered four different sets from Acer Racer - clutch, brushless motor, regular, and 7x10x3, which is a bit peculiar, but interesting. So far the clutch bearing, once I got the seals off and all the grease out, seems the most promising. Acer Racer claims they are engineered differently, tighter specs, for the clutch duty. They spin very freely and seem to have just about no radial play. They also seem to run smoother and quieter than the previous bearings. Cost isn't a problem - they're about eight bucks. I'll have more to report later.

I wonder if Acer Racer is a bit puzzled by these orders. We should all e-mail them pictures of the arms.

I've been playing in the shop, again. I narrowed the bearing spacing and the effective length is 4.5". It weighs 49gr. It tracks well and sounds good. It PVC-based and the sonic improvement with the paint was amazing. This arm transmits the least noise/music into the structure of any arm I've built.

I measured equal lengths of aluminum and carbon fiber tube - they weighed the same, but the carbon won the resonance drop test. The aluminum rang like a chime while the carbon just made a high pitched thunk. Maybe JRKO could tell us more about this.

I'm beginning to think this thing we've been working on - two years now for me - is just about dialed in. The basic recipe is pretty well determined. I hope that means more folks will jump in because, at this point, a working LT can be made with hand tools on an apt. kitchen table. It may not be terribly precise or beautiful, but it will work and sound good.

phivates - would you explain a bit more on your 90 degree torquing question?
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File Type: jpg P1040472.jpg (204.9 KB, 453 views)
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Old 23rd April 2012, 11:28 PM   #402
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That looks great dtut! I see you used a wider angle than 90 deg - did that help?


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Old 24th April 2012, 03:06 AM   #403
bgruhn is offline bgruhn  United States
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Hello all also:
Fran- Nice job. I think you are just about there. What did you use for the arm wand(s). I like your styling and implementation. It is going to be interesting to see what refinements are going to come about.
Doug- You have been busy. PVC wow. You say paint made a big difference. I assume you mean the red stuff on the carriage frame. I used wood, mahogany, about 1/8" thick for the vertical carriage member and wood for the bearing support rods and the arm wand. so far I've not used any damping on the wooden parts. Put some darker oil stain on the arm wand for looks only, and thin coated the frame with cyanoacrylate glue to seal it against humidity. It has turned out to be very quiet. With the amplifier off and a good loud record playing there is barely any needle talk audible. I would like to build a carriage with the double tube arms as Bo and now Fran have done. Regarding the "clutch" bearing with very small radial play. My gut feel is that taking that accommodation for small playing wows away and forcing the bearings to ride up and down the glass walls will not be as satisfactory. Otherwise I think the better bearing, less friction lower starting and running torque can only be good. Going back to Bo's insistence that getting the most signal off the record and into the amplifier was the name of the game. Introducing lossy elements into the structure, damping materials, paint, PVC, wood, imho will work against Bo's basic goals. It will help to kill resonances and feedback to the cart. So I think there may be a compromise needed. We gotta sort that out some. My wood structure definitely works better than the early one using aluminum tubing. That one needed to be wrapped with black tape and cotton thread. So I'm not convinced that using PVC is the way to go.
Fran- I was under the impression that these ceramic bearings had non-contacting shields. So I left them in place. Guess I'll remove the shields and check that out. Good Show Lads,

BillG


Quote:
Originally Posted by dtut View Post
Hello all,

Very good news all around. Fran, I checked out your video. That's a handsome LT and it performs excellently. I like the straight ahead styling, it's very effective.

I'm delighted/relieved the ceramic bearings worked for everybody. I ordered four different sets from Acer Racer - clutch, brushless motor, regular, and 7x10x3, which is a bit peculiar, but interesting. So far the clutch bearing, once I got the seals off and all the grease out, seems the most promising. Acer Racer claims they are engineered differently, tighter specs, for the clutch duty. They spin very freely and seem to have just about no radial play. They also seem to run smoother and quieter than the previous bearings. Cost isn't a problem - they're about eight bucks. I'll have more to report later.

I wonder if Acer Racer is a bit puzzled by these orders. We should all e-mail them pictures of the arms.

I've been playing in the shop, again. I narrowed the bearing spacing and the effective length is 4.5". It weighs 49gr. It tracks well and sounds good. It PVC-based and the sonic improvement with the paint was amazing. This arm transmits the least noise/music into the structure of any arm I've built.

I measured equal lengths of aluminum and carbon fiber tube - they weighed the same, but the carbon won the resonance drop test. The aluminum rang like a chime while the carbon just made a high pitched thunk. Maybe JRKO could tell us more about this.

I'm beginning to think this thing we've been working on - two years now for me - is just about dialed in. The basic recipe is pretty well determined. I hope that means more folks will jump in because, at this point, a working LT can be made with hand tools on an apt. kitchen table. It may not be terribly precise or beautiful, but it will work and sound good.

phivates - would you explain a bit more on your 90 degree torquing question?
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Old 24th April 2012, 04:03 AM   #404
dtut is offline dtut  United States
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Bill,

I was afraid this was gonna happen - the red paint comment was just me making fun of my stylin'. The PVC just gave me nice curves to work with, it's possible damping qualities only became apparent after the arm was built. I weighed equal sized sections of ABS and PVC and was surprised that PVC is heavier even though the ABS was thicker. In other words, ABS is less dense. In the past, I've had to use heat shrink to make aluminum tube quiet, but this time it doesn't seem necessary.

We've taken this thing to the point we're discussing arcane subjects like the finer points of bearing characteristics and the resonant qualities and consequences of materials and structures.

I'll be mounting the clutch bearings some time soon and will check to see any effects in warp handling, which is where I think any lack of radial play would make itself felt. I think the ceramics seals only contact one side. I took them off just on GPs and the clutches and 4x10x4 s cleaned up much easier without them.

Fran - I just tried to guess Bill's angle on his first glass track. I over estimated and wound up with 120 degrees, which does get the upper edge of the glass out of the way, but I'm not sure there's any other advantage. I've been doing some thought experiments about V angles and as far as I can tell, any angle from 90 and above up to the point where torquing and skittering begins to show up will work. At this point, I think your method of mounting the sllps in 90 degree aluminum angle is the simplest, best protected, most easily attached way to go. Again, very nice work and thanks for coming to the party. Would you post some pictures here? I'd like to see some more details.
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Last edited by dtut; 24th April 2012 at 04:07 AM. Reason: missing verb
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Old 24th April 2012, 06:28 PM   #405
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Doug: your sense for the visual esthetic is excellent. I really think you should consider industrial design. You have an excellent balance between a look which captures the interest while at the same time follows and servers function. Do you draw any of your ideas up in sketch up that we could see. I think an assortment of different ideas would provide some real stimulus for those trying to decide how they might want their arm to look. Well done I would like to see more. Best regards Moray James.
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Old 25th April 2012, 01:21 AM   #406
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Default Stylin'

Your arm is wicked awesome. As for damping or not, well I don't like the results that go with undamped systems in my carpenter world, including my truck, and I've just joined the ductseal club on my speaker tweaking. Gloss red on PVC: brilliant, literally.
My 90 degree comment is also carpenter-think; that when a force is resisted say by bearing friction there's a reaction sideways. Posts bend before they crush under load, frinstance. Popping the clutch usually results in a wavy patch on the pavement, if the torque available is sufficient. Is that "moment?"
Anyway. Great stuff. I agree with M James.
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Old 25th April 2012, 10:58 PM   #407
dtut is offline dtut  United States
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Thank you Moray and phivates for the kind words about the arm.

The Sketch Up learning curve was a bit steep for me and my working drawings are mostly crude reminders of what I've been thinking about - the one for the latest arm is literally on the back of an envelope - but I have thought about compiling the photos. I'm a sculptor, and although I haven't done much of that recently, it seems to come out sideways in my audio designs. Before I discovered Norman bel Geddes or figured out Raymond Lowey designed something other than the '53 Studebaker, my life took a couple of turns that put industrial/package design out of reach. I've always regretted that.

I think the 90 degree question deserves investigation. Ceramic bearings seem to alleviate a lot of the friction problem, but that still leaves inertial forces. I've never had much luck at trying to vector this thing out.

I don't like to hear needle talk or to hear sound from any source in the arm with a stethoscope so I've used brute force methods - neoprene, heat shrink - to tame that sometimes. I'm not sure about the consequences to the music.

Questions from an LT skeptic friend made me take the pictures. The bearing does seem to slide rather than pivot on the back corner. In a 90 degree V, a really bad warp might make the back side of the bearing scrape a bit, but that would be extreme and momentary. A more open V keeps that from happening at all.
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File Type: jpg P1040491.jpg (117.1 KB, 194 views)
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Old 26th April 2012, 01:30 AM   #408
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Default Vectors

Or something; my middle name is Victor, who was my dad. 50 years ago I was on the swim team in high school. We strove mightily to keep our palms moving in a pure longitudinal stroke with no, that's zero, deflection laterally. Now they say that the zig zag ours hands want to do is what works. Fish zig zag to get on their way, their way. Are they stupid?
Nature has scant use for straight lines. We REALLY want them to work. Consider the groove our stylus is asked to track. Not too linear! So when our precious gem is told to do what it has to do, a bit of wiggle room right at the beginning may be what is needed to get going.
Is this clueless? I am just guessing.
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Old 26th April 2012, 01:43 AM   #409
Nanook is offline Nanook  Canada
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Default Dear clueless (phivares)...

...I don't think you can fight the Physics, however nature has a funny way of "finding" the most efficient (and thus lowest energy) solution to pretty much all physical system problems. It reminds me of engineers who engineer solution rather than look for a simpler solution.

Considering the "sliding" bearing issue as stated by dtut:If you'd like to "vector this thing out" PM or email me. I'll see what I can do (just nice simple vector diagrams in 3D). The forces acting on the stylus/cart/arm/bearings/armshaft/counterweight/tube, etc., can be diagrammed as a series of small isolated or "closed" systems. The great thing about the use of vectors is that there exists a well defined set of rules and vector mathematics that can help explain a particular system (almost) completely.

dtut: the arm you've built is pretty spectacular to look at. Kudos on the implementation.
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Last edited by Nanook; 26th April 2012 at 01:45 AM. Reason: added congrats on the design/implementation to dtut
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Old 26th April 2012, 02:47 AM   #410
dtut is offline dtut  United States
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My dad worked at Scripp's Institution of Oceanography in La Jolla. Scripp's, among other things, did research for the Navy, which in its effort to design faster subs, spent a lot of time looking at dolphins. There was serious Naval consternation when they found that dolphin skin ripples to accommodate micro pressures in the water, which allows them move far more efficiently than rigid structures.

Nanook, that's a very generous offer. Thank you. PM on the way.
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