RossSackett
sage
Reged: 08/17/07
Posts: 338
Loc: Memphis, TN
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I ran the usual field-expedient stiction test for dob bearing material: I went to Home Depot with a block of teflon, and sandwinched the block between sample sheets of countertop laminate. They had a good selection of Formica and Wilsonart laminate samples, with several different textures. In each challenge I used finger pressure to squeeze the laminate1-teflon-laminate2 sandwich together and apply an increasing amount of shear, until the laminate on one side or the other slipped. The winner of each challenge (the one that slipped first) goes on to the next round.
Here are some findings: shiny polished laminates consistently beat matte laminates, including "stone" textures (even though the stone textures were bumpier at a macro scale). Among the shiny laminates, the bumpier the better.
The winner? Among those I tested, the best was WilsonartHD series #45 texture, available in several different color patterns, particularly the "Passage" series (I didn't find any stiction difference between the colors). Wilsonart calls this texture "#45 facet ultra-premium". This has a shiny microtexture, overlaid with very small bumps and grooves resembling a halftone screen.
How does it compare to our old favorite, Wilsonart Ebony Star? I had a little left of both "old" Ebony Star and the more recent "grittier" version that some suppliers still stock. The new #45 facet texture lost to old Ebony Star, but beat the new gritty version. When I added a little SailKote dry lubricant to the #45, it beat the untreated old Ebony Star in the stiction test. If I had more "old" Ebony Star I would probably use that, but in the mean time I think the new #45 "facet" texture will have to do.
So I have purchased a 4X8 sheet of the Mountain Passage #45 texture laminate. I'll post again when I have had a chance to actually use it in a scope.
I'd be interested in hearing if others can replicate this, and would be delighted to hear if they can find something better.
Ross
[Note added later: Moki reports that Formica Sparkle Finish laminate also performs well. I tested it later and found no consistent difference between it and #45 facet, so both are likely to perform well in a scope. See below.]
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Ross Sackett
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11 scopes currently on the flight line from 4.25 to 18"; 5 pairs of astronomical binocs 35-80mm. My wife suggests that with just one pair of eyes, this might be excessive.
See my scope pix at http://www.flickr.com/photos/8315630@N04/
Carpe noctem!
Amateur astronomer = A mature moon-starer
Edited by RossSackett (08/09/08 10:44 AM)
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KerryR
sage
Reged: 12/05/07
Posts: 317
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Very Cool of you to do the test and publish your results!
This is the sort of info that needs a "sticky", so me and others don't have to try to search for it when we need to remember/find for the first time this info.
Thanks!
Kerry
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Kerry
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Gregg Lobdell
sage
Reged: 01/20/06
Posts: 373
Loc: Covington, WA
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Very nice data Ross. Looking at the Wilsonart web site, they list nine (9) different finishes. http://samples.wilsonart.com/t-laminate_finishes.aspx Did your test happen to include all these finishes? I'm particularly curious how #35 Mirage – Ultra Premium; #90 Crystal – Premium; and #7 Textured Gloss performed.
Last time the pattern of choice was "Ebony Star", a very astronomical name. It's interesting to note that in the Passage line there is a "Night Passage", pattern number 1845-45
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Clear skies,
Gregg
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RossSackett
sage
Reged: 08/17/07
Posts: 338
Loc: Memphis, TN
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#45 clearly beat #7 and usually beat #35; they didn't have samples of the #90 so I can't say.
I do like the colors of the passage series--they would all go well on a wooden scope. Night Passage is a great name.
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Ross Sackett
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11 scopes currently on the flight line from 4.25 to 18"; 5 pairs of astronomical binocs 35-80mm. My wife suggests that with just one pair of eyes, this might be excessive.
See my scope pix at http://www.flickr.com/photos/8315630@N04/
Carpe noctem!
Amateur astronomer = A mature moon-starer
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Houdini
sage
Reged: 07/13/07
Posts: 392
Loc: Europe
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Hi Ross,
Can you show us a close-up picture of the #45 "facet" surface texture?
Thanks,
Robert
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16" f/4.9 motorized alt-az, 25" f/5 Dobson, 43" f/4 alt-az in construction
Mirror Edge Support Calculator
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Gordon Rayner
professor emeritus
Reged: 03/24/07
Posts: 506
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Let us not forget the novel work in England by Martin Lewis, which appeared in two Sky and Telescope articles,October of '99 and Oct. 2003, in which he showed superior reduction of unstick velocity , first with teflon sheet as used in printing T-shirts, and later with PFA .
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RossSackett
sage
Reged: 08/17/07
Posts: 338
Loc: Memphis, TN
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Here's an attempt to photograph the surface with a little digital microscope. Each division of the scale is 1 mm.
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Ross Sackett
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11 scopes currently on the flight line from 4.25 to 18"; 5 pairs of astronomical binocs 35-80mm. My wife suggests that with just one pair of eyes, this might be excessive.
See my scope pix at http://www.flickr.com/photos/8315630@N04/
Carpe noctem!
Amateur astronomer = A mature moon-starer
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RossSackett
sage
Reged: 08/17/07
Posts: 338
Loc: Memphis, TN
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Gordon,
I read on another forum that at least with the teflon sheet there were wear issues and a rather limited service life. Have you seen anything recently on how they hold up? (And what is PFA?)
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Ross Sackett
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11 scopes currently on the flight line from 4.25 to 18"; 5 pairs of astronomical binocs 35-80mm. My wife suggests that with just one pair of eyes, this might be excessive.
See my scope pix at http://www.flickr.com/photos/8315630@N04/
Carpe noctem!
Amateur astronomer = A mature moon-starer
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RossSackett
sage
Reged: 08/17/07
Posts: 338
Loc: Memphis, TN
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Gordon,
Sorry, I was just being lazy. According to the DuPont website PFA is a teflon-like thermoplastic available in a wide variety of shapes, from pellet to film to sheet. McMaster-Carr sells it in rod and film form (0.005" max, which might be a bit fragile for our uses). Kinda pricy compared to the usual PTFE.
Ross
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Ross Sackett
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11 scopes currently on the flight line from 4.25 to 18"; 5 pairs of astronomical binocs 35-80mm. My wife suggests that with just one pair of eyes, this might be excessive.
See my scope pix at http://www.flickr.com/photos/8315630@N04/
Carpe noctem!
Amateur astronomer = A mature moon-starer
Edited by RossSackett (08/08/08 03:59 PM)
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Houdini
sage
Reged: 07/13/07
Posts: 392
Loc: Europe
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Thanks, Ross!
If each mark is a mm, the bumps are quite small compared to some other laminates that have been used for dob bearings.
Be careful with the interpretation of your test results.
There are two aspects to friction: the static friction (how much force is require to start moving?) and the dynamic friction (how much force is required to keep moving?). For most material combinations the dynamic friction is smaller than the static friction and it will be difficult to stop the movement once it has started. In other words, you'll "overshoot" - making it tough to move the telescope by small distances.
Your tests are based only on the static friction, so you may well end up with a telescope that moves very easily but is hard to stop.
Ebony Star on teflon is an excellent combination providing low static friction and well matched dynamic friction (if the contact pressure is around 15 psi or 1 kg/cm²).
If I recall correctly, PFA on teflon gives larger static friction than Ebony Star on teflon, but produces even better control of small movements.
Robert
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16" f/4.9 motorized alt-az, 25" f/5 Dobson, 43" f/4 alt-az in construction
Mirror Edge Support Calculator
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RossSackett
sage
Reged: 08/17/07
Posts: 338
Loc: Memphis, TN
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Robert,
Yes, the little bumps are spaced only about 0.5 mm apart. There is also a larger-scale texture--irregular areas about 2 mm across that are bump free.
Good point about balancing the two kinds of friction. I evaluated the difference between static and dynamic friction by seeing how small a movement I could produce with the laminate-teflon sandwich. I was able to produce much smaller jumps using the #45 texture than with the other textures: about 1/2 mm with the #45, and about 1 mm with anything else. With the SailKote I got the jumps with #45 down to about 0.25 mm. There is some subjectivity here because the magniture of the jumps were dependent on the force squeezing the materials together, but I had the definite impression that the #45 had smoother motion.
I am not trying to convince anyone that the #45 is superior in a telescope, just that it looks promising. That said, the old Ebony Star was still better than any of the laminates I tested--untreated, I could get movements down to about 0.1 mm.
By the way, virgin teflon-on-teflon did worse in this test than teflon on any of the laminates, both in terms of ease of movement and magnitude of the jumps.
Ross
Edited by RossSackett (08/08/08 07:10 PM)
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Houdini
sage
Reged: 07/13/07
Posts: 392
Loc: Europe
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Great, that makes #45 a really interesting candidate.
I sure wish we could obtain all these Wilsonart laminates here in Europe...
Robert
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16" f/4.9 motorized alt-az, 25" f/5 Dobson, 43" f/4 alt-az in construction
Mirror Edge Support Calculator
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Moki
super member
Reged: 11/06/05
Posts: 349
Loc: Dallas, GA
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Good info. Always good to have laminate bearing surface alternatives.
I also found an alternative to ES in a Formica brand 909-42 "Sparkle Finish" (black, but it comes in several colors). It also has very small bumps and is somewhat shiny, definitely not matt. I've used it on several scopes against teflon and I can't tell any subjective difference as far as stiction/friction compared to the scope I have with ES bearing surfaces.
When I get time, I want to try the "Sailkote" treatment and see how that works on the Formica.
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"In questions of science, the authority of a thousand is not worth the humble reasoning of a single individual." Galileo
12.5" F5.3 Dob on EQ platform
8" F7 planetary Dob / EQ Platform
Current ATM projects:
Xtal-Controlled EQ platform motor drive
8" F6 Dob for club
Motorized focus for planetary
10" F6 Ultralight PushTo
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Joe Cipriano
Entropy Personified
Reged: 09/03/05
Posts: 3830
Loc: Uh... anyone have a GPS?
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Quote:
Very Cool of you to do the test and publish your results!
This is the sort of info that needs a "sticky", so me and others don't have to try to search for it when we need to remember/find for the first time this info.
Thanks!
Kerry
Done. This thread now has a link in the "Best of ATM" thread. Good information here (kudos to Ross for the field work...  ), and I don't want it getting lost.
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In the Land of Eternal Light Pollution & Great Pizza (Chicago)
SN-6, ED80, WO 66SD
Meade 208xt, SBIG ST-4
D70 (modified)
CGE (way modified)
A Wife who understands (unmodified)
Some other stuff...
I may not have gone where I intended to go, but I think I have ended up where I needed to be.
Douglas Adams
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RossSackett
sage
Reged: 08/17/07
Posts: 338
Loc: Memphis, TN
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Quote:
I also found an alternative to EbonyStar in a Formica brand 909-42 "Sparkle Finish" (black, but it comes in several colors). It also has very small bumps and is somewhat shiny, definitely not matt. I've used it on several scopes against teflon and I can't tell any subjective difference as far as stiction/friction compared to the scope I have with ES bearing surfaces.
Moki,
I went to Lowe's this morning and found some samples of Formica sparkle finish laminate. My experiences were just as you say--it has excellent characteristics. There was no systematic difference between sparkle and Wilsonart #45 either in static friction or jump distance--totally a toss-up. For me the choice would be price and local availability. It wasn't quite as nice as old Ebony Star, but since you say you can't feel the difference I am very encouraged that the small differences in test results don't reveal any real degradation in performance. Thanks for the tip-off!
Ross
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Ross Sackett
---------------------
11 scopes currently on the flight line from 4.25 to 18"; 5 pairs of astronomical binocs 35-80mm. My wife suggests that with just one pair of eyes, this might be excessive.
See my scope pix at http://www.flickr.com/photos/8315630@N04/
Carpe noctem!
Amateur astronomer = A mature moon-starer
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RossSackett
sage
Reged: 08/17/07
Posts: 338
Loc: Memphis, TN
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Quote:
I'm particularly curious how ...#90 Crystal – Premium...performed.
Gregg,
I found some of that at Lowe's, too. It turns out that #90 is the new (gritty) Ebony Star finish. In the test, it fared poorly against the emerging winners #45 Facet and Sparkle.
That said, it turns out that #90 is what I used in my recent Moonsilver IV and "Nemo" scopes. I wet sanded it with very fine automotive finish abrasive paper (Meguiar 0000 if I remember correctly) and hit it with SailKote. It is well-behaved on the scopes with little noticable stiction or springback, though admittedly not quire as buttery smooth as I would have loved. Unlike old Ebony Star, I didn't get that great feeling that the scope was just OOZING in the direction I wanted.
Ross
Edited by RossSackett (08/09/08 03:37 PM)
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Jeff Morgan
Carpal Tunnel
Reged: 09/28/03
Posts: 1531
Loc: Prescott, AZ
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Quote:
Let us not forget the novel work in England by Martin Lewis, which appeared in two Sky and Telescope articles,October of '99 and Oct. 2003, in which he showed superior reduction of unstick velocity , first with teflon sheet as used in printing T-shirts, and later with PFA .
When that 2003 article came it sounded like Dobsonian nirvana. Naturally, I ordered a 6" square sheet of PFA within minutes of reading the article. It was installed on a 10" f/6 Dob, but the scope was subsequently stolen and I never had the chance to really put it through its paces. What little I did see was mixed, and I posted something to that effect at the time.
A couple of weeks ago another CN member was data-mining for PFA and pm'd me about it. It renewed my curiosity, since I still had the material out in the garage somewhere. Towards the tail end of my last observing session I replaced the Telfon altitude pads on my 12.5 f/6 with rough-cut PFA pads. Izar was conveniently low in the west, so I could isolate the altitude movement of the scope. Differences with Teflon were subtle. I think I may have ever so slightly preferred Teflon. Given it was the end of my session and I was very fatigued, I probably once again did not give the material a fair (or thorough) trial. Another factor to consider was that I tend towards larger alt bearings in my scopes (12-3/4" radius on the 12.5") to accommodate a wide range of eyepiece weights. One byproduct of this is that I already have fine control with Teflon.
So, I think that PFA may have something to offer people that are looking for improvement. Particularly if your scope has smaller bearings and rebuilding is not an option. It appears to be a serviceable substitute, there is no risk that it will "not work". Compared to Telfon it is pricey, but on an absolute scale not too bad at all (at least compared to the Ethos I just ordered). I think I payed $50 delivered for mine.
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Jeff Morgan
Prescott, AZ
Wile E. Coyote School of Telescope Making
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veebs2
sage
Reged: 03/13/07
Posts: 206
Loc: DeKalb, IL
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Has anyone tried the WilsonArt #45 or Formica "Sparkle" laminaes in any project yet? If so, thoughts?
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Paul
Zhumell 10" (My Mistress - name given by my wife)
Hyperions - 5mm, 13mm and 24mm
Stratus - 8mm and 17mm
Howie Glatter 2"-1 1/4" Holograpic w/ Barlow
Lumicon OIII Filter
Telrad
DeKalb, IL
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DSalters
sage
Reged: 03/03/07
Posts: 438
Loc: High Ridge, MO (St. Louis)
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I am confused about the choice of Ebony Star. As far as I knew, the texture was the determining factor. Why does the color pattern get so much attention when it is the texture that matters?
When I ordered my supply of Ebony Star five or so years ago, multiple patterns were available with the same texture...with this in mind, I would guess that the color never did matter, but was mearly a preference, correct?
Daniel
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6" f/8 Bushnell Voyager Dob. Rebuild
10" f/5 Highe Dob. variant
(UNDER CONSTRUCTION: 5" f/5, 8" f/6, 13" f/4.6)
Baader Hyperions--Primary Eyepieces
"The sun has one kind of splendor, the moon another and the stars another; and star differs from star in splendor." -1 Corinthians 15:41
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veebs2
sage
Reged: 03/13/07
Posts: 206
Loc: DeKalb, IL
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It is my understanding also that the color does not make a difference. The important part is the texture (WilsonArt #50). I think Ebony Star was simply used for its astronomical reference.
The reason many are looking for a new laminate is that WilsonArt stopped producing the #50 texture. Correct?
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Paul
Zhumell 10" (My Mistress - name given by my wife)
Hyperions - 5mm, 13mm and 24mm
Stratus - 8mm and 17mm
Howie Glatter 2"-1 1/4" Holograpic w/ Barlow
Lumicon OIII Filter
Telrad
DeKalb, IL
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