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bwschulz
03-31-2008, 06:42 AM
I'd like to thank everyone for the large number of great suggestions I
received.
Here's the promised summary:

Original Message-

I'll need to obtain many more small (about 8-10mm) retroreflective
markers soon, and with the prices vendors charge for them I'd like to
look into finding alternative suppliers or making my own. Please let me
know if you can help me with any of the following questions:
-Suppliers of pre-made markers other than Vicon and B & L Engineering.
Have you worked with a company that was preferable for some reason?
-Suppliers for small diameter (8-10mm) spheres. Any kind of rigid
plastic or even aluminum should be fine, but I don't think that we can
drill and tap holes in spheres that small of anything harder.
-Suppliers of high-quality retroreflective films to cover markers with.
-I'm very interested in using retroreflective paint instead of film, but
old posts in the archives indicate that the paint (if it's still even
available), when properly applied is only about 10% as effective as the
film. I don't think that this level of performance would be acceptable
for my application. If you have any experience using any kind of
retroreflective paint, I'd like to know how well it's worked in your
application compared to the films. I'd also like to know where you got
it.

Thanks for any help you can offer- I'll summarize and post all
responses.


Responses-

Hi Brian,

My experience is primarily with Vicon's 25 mm markers and larger, but I
used with great success the 3M reflective tape both to repair existing
markers and to make new custom markers. It's expensive, but one roll
will last for a very long time. For the markers, I have used a variety
of materials to make my own, but it depends on what kind of activity you
are studying. For heavy activity, I had success with rubber bouncing
balls and plastic golf balls and things of that nature, but for lighter
activity styrofoam balls found in any craft store should work well and
come in a greater variety of sizes. Marbles could also work, but you
might have to have a drill press to devise a means of attaching them.
It really does depend on the activity you are studying and how you want
to affix the markers to your subjects, so if you have more info I might
be able to come up with some better ideas. Hope any of this was
helpful.

Cheers,
Tiffany

Tiffany Zachry
Moss Rehabilitation Research Institute


Brian:

I think you can go to a craft store and get small styrofoam spheres. I
believe that 3M makes reflective tape to cover the spheres with.

Patrick Sparto


Brian,

There have been several discussions on the BIOMCH-L listserv about this.
Search the archive (URL is at the bottom of your previous message) for
"reflect" or "marker" or something like that. I remember there were some
detailed instructions, I think, from several researchers for making your
own inexpensive markers, as well as pitfalls and helpful tips about
getting the supplies and about reflective paint.

We used 3M reflective tape, cut into small strips to cover the wooden
spheres. It has worked very well. As I recall, a roll of the tape is
pretty expensive ($200?), and they didn't sell it in any lesser amounts.
We've made about 100 reflectors and only used about two meters of the
roll.

Other than the wooden spheres from a crafts store, I don't have any
other ideas. Sorry.

Bruce Etnyre, Ph.D., P.T.
Kinesiology Department
Professor
Rice University


Dear Dr. Schulz,

Try Motion Lab Systems for 3M retroreflective tape:
Mr. Edmund Cramp,
eac@motion-labs.com

Plastic Spheres (Nylon):
http://www.spheretecinc.com/products/plastics/

Best regards from Brazil,
Wagner de Godoy


Hi Brian,

Small Parts Inc has the balls (spherically speaking) -
http://www.smallparts.com

Motion Lab Systems can supply the 3M coating materials - and I can talk
you through some short-cuts in actually coating the balls. It's not as
hard as you might think.

Retroreflective paint does work but is significantly less reflective
than the film ... I think Qualysis used the paint at one time.

We always carry a stock of 1" tape and have some 3" wide tape too. We
can order other sizes but we have to order by the roll so it's not
really economic unless you need a LOT of tape. The 1" tape is $5.75 per
yard.

Regards,
Edmund Cramp - eac@motion-labs.com
Motion Lab Systems, Inc. - http://www.motion-labs.com
15045 Old Hammond Highway, Baton Rouge, LA 70816 USA
Tel: 1.225.272.7364 (Central Time Zone, GMT-6)
Fax: 1.225.272.7336


An alternative pre-made marker supplier is:

www.mocapsolutions.com
Kevin Krohn
kevin@mocapsolutions.com

-Jeremy Determan



Good morning.

We hope to have our new website up soon. In the meantime, I've attached
is
a price list & pictures for all MoCap Solution's new custom items. On
the new list are all the items that we plan on keeping in stock for same
day customer shipments.

Please let me know if there are OTHER parts that you have a large
quantity/ substantial need for and we will be more than happy to quote
them individually.

MoCap Solutions highly engineered markers are injection molded from
space age Liquid Silicone Rubber (LSR), an extremely durable yet
flexible material. This allows the markers to fit against the human form
comfortably yet remain intact during even the harshest motion capture
sessions.

MoCap Solution's new Z Suits, E-Z patches and Skinz Patches are awesome
new designs and are made of very high quality materials.

The new Z Suit is made of a new high quality 4 x 4 stretch breathable
poly pro material. The 4 x 4 material is very cool and comfortable for
the actor and also very durable for marker application & removal.

The new E-Z patches are to be used with our 14 & 19mm markers when
attaching them to Motion Capture suits. The small tab at each end of the
E-Z patch makes it allot easier to remove than patches of the past. They
can be made in black, red, blue, green and yellow to make it easier to
identify the actors who are wearing the different colors.

The new Skinz Patches are also to be used with our 14mm or 19mm marker
(made without Velcro backing) directly on the capture subjects skin.
Peel the self adhesive backing off of the skinz patch and place over the
entire marker base. The patches are made from the same breathable fabric
as band-aids.
They hold the marker firmly in place, don't fall off from perspiration
and can be easily removed after the capture session.

Please let me know if you have any other questions or feed back
regarding any items on the price list.

Thank you!

Sincerely,

Kevin Krohn
Business Development Manager
714-272-2960



United States Plastic Corp. (www.usplastic.com) sells spheres as small
as 3/8".
**Thin** coats of Sphere Brite (http://www.usreflector.com/Welcome.html)
retroreflective spray paint have worked well in our applications. One
$30 can has covered 100 markers so far and isn't empty yet.

Doug Powell
University of Texas Permian Basin


Dear Brian,

I faced the same problem some time ago in Germany.
Finally y bought plastic (PVC) spheres originally made for bearings in
washmachines or any other "watered" application. So the supplier was a
bearing manufacturer. The spheres were quite cheap.
I had no luck with paint (did not try it physically but searched a lot
and talked to many people).
Finally I used retroreflective film from Scotch 3M.
Depending on how many markers you need, as they are small it will
probably be enough to get some samples. Recently vendors here in Spain,
were I'm now, provided me with some free samples. Not all suitable, but
some of them. I think I could easily make about 20 markers from the
samples I got.

By the way, if you're going to build them yourself, the best way I found
to do that is to cut tiny "daisies" (8 petals) out of the reflecting
tape.

Hope this helped a bit.

Good luck and have fun doing handicrafts,

Gaspar Morey


Hi Brian,

We have been very happy with the markers we get from 3X3 designs here in
Vancouver. Norma makes markers for the animation industry and is very
good at making what you want. We recently purchased 50 9.5 mm markers
with a .8 cm base and 50 12.5 cm markers with a 1.2 cm base for a very
reasonable price. I noticed on her price list she makes markers as
small as 4mm up to 25mm. Here is her contact info.

3X3 DESIGNS LTD.
http://www.3x3.bc.ca
T:(604) 777-2555
F:(604) 777-2508

Regards, Alec
__________________________________________________ ___
Alec Black
Director, Shriners Gait Lab
Sunny Hill Health Centre for Children
3644 Slocan St.
Vancouver, B.C.
V5M 3E8
Canada


Hello Brian,

Please ask BTS Bioengineering:
http://www.bts.it/eng/default.htm

They make and offer this kind of markers. Maybe they can help.

Best
Alex
_________________________________
Alex Czarowicz | VP Sales & Marketing
Organic Motion, Inc.


Brian,

We made up our own markers with reflective tape wrapped around stryofoam
balls that we purchased from a handicrafts store. We then used small
screws to attach the balls to a small plastic "platform" which could
have two sided tape attach the balls to the subject. It worked fairly
well for several years until eventually the screws pulled out. As the
whole set up cost approximately $15 for 20 reflective markers we thought
it worked well. At that price replacing them more often is still much
cheaper than buying premade ones. I don't recall if we had any markers
as small as you are planning on.

Randall L. Jensen, PhD, FACSM, CSCS
Professor of Sport & Execise Science
Dept. HPER
Northern Michigan University
Marquette, MI 49855 USA


Hi,
I've always made my own markers, 20 mm ones for human applications and 6
mm ones for cats.

I used wooden beads for the 20 mm markers. You can buy the beads at arts
and crafts stores like Michaels. The are pre-drilled and you can tap the
hole if you want. Sure the hole goes all the way through, so the top
will be a bit flattened. If you really want you can probably fill the
wholes on one side, but I just taped them over with the reflective film.
The reflective tape to use is 3M Scotchlite 7610 or 8850, it's self
adhesive and super reflective and flexible enough to conform to the
balls (I believe I used the 8850 in Belgium and the 7610 in the US, both
look similar).
I use a method that covers 1 ball with 3 pieces of tape: 2 rounds and 1
rectangular strip.
I use a round chisel (a leather tool that you can buy in tool shops) to
cut rounds out of the tape.
Then I make 6 radial cuts with a straight chisel (you can stack 3 or 4
together), leaving the center part uncut.
Apply 1 round to each pole of the ball while overlapping the flaps of
tape nicely at the equator. Finnish off with a band around the equator.

Cheapest markers ever...all it takes is the 3M tape and a bit of work,
but with practice you can probably make a marker in 3 minutes !

Good luck !
Dirk

Dirk Everaert, PhD, PT
Research Associate
University of Alberta
Centre for Neuroscience
513 Heritage Medical Research Centre
Edmonton, Alberta T6G 2S2




Ok, I was thinking about your scenario more over lunch, and I may have
some ideas that could work for you. One is slightly unorthodox, the
other very unorthodox but possibly a perfect solution. First, at any
craft store like Michael's you can get wooden, glass, and plastic beads
in various shapes, and they all already have a hole in them that could
be used to attach to your threaded rods (they wouldn't screw in, but you
could use glue or something else less permanent like a soft putty). The
other idea is a little out there, but it could work quite well if you
can find a place that will let you order in bulk. The end cap of
certain body jewelry such as tongue rings is about the size that you're
looking for, and the best part of them for your situation is that they
come pre-threaded because they are made to screw onto the end of a rod.
They also come in different gauges, so you should be able to find the
size that is appropriate for the rods that are attached to your shoes.
I actually wish I had thought of this a long time ago because it is a
very neat solution to a problem we've all dealth with when doing motion
capture. However, I think either solution should accomplish what you're
trying to do and shouldn't be too costly, either. I hope this helps,
and thanks for asking the question - it was nice to relive the days when
I got to do fun stuff like mocap and EMG.

I found a website for you that sells body jewelry wholesale. It looks
like you can get the little acrylic ones for about $0.25 - $0.75 a
piece, and you can buy as few as one. I know from experience that that
price rivals the cost of the beads, but what you would want to do is
take one of your rods into a piercing store and ask them if they can
tell you what gauge it is so you can order the right size. The beads
will probably work well, too, but the down side is that the holes don't
come in different sizes and they're not threaded. You'll have to let me
know which way you decide to go and how it works out.

http://www.monstersteel.com/Translucent-UV-Acrylic-Ball-Tongue-Barbell-n
id-189.html

Cheers,
Tiffany

Tiffany Zachry
Moss Rehabilitation Research Institute


Brian,

I've used retroreflective markers from BTS
(http://www.bts.it/eng/default.htm) several years ago. They are
generally 10mm in diameter. But they've also got some really tiny ones
for finger movement. Their website has 3-20mm markers listed. I am not
sure how much they cost now. But they worked well before.

Hope it helps.

Gang Yang

Biodynamics Laboratory
The Ohio State University
Columbus, OH 43210


Brian,

I am not sure about the films, we always had it available in the Lab
(UNSW), so I never had to look for them, but as for the spherical
markers I used to get them done by a fitter machinist. Any CNC fitter
could actually machine any size and material marker for you.

hope this helps a bit

cheers

Raul Landeo


The most cost effective way is to make them yourself. We had our interns
spend a day or two making 50 markers. All you need is 3M reflective tape
(they sell them by the roll) and sphere or cube beads that can be bought
at any crafts store (ie, Michaels). And you also need either vinyl
padding or rubber mats for the base.

Arnel Aguinaldo, MA, ATC
Director, Center for Human Performance
3020 Childrens Way 5054
San Diego, CA 92123