EbonyStar Laminate Round Bearing Kits
This EbonyStar laminate (Formica) has a textured surface that works
very well with PTFE to provide a low friction bearing surface. Round
doughnuts are for Dobsonian azimuth bearings, to be used with PTFE
on the mating surface, providing smooth slewing and durability. All
sizes have 1.25" width, 0.045" thick, dark grey and white mottled
color. Adheres with contact cement.
Each of the round bearings come with three PTFE pads, 1 inch square
and 1/8" thick, which attach with contact cement and supplied stainless
steel wood screws. Other pad thicknesses are available, select below.
The round bearings normally adhere to the underside of the Dob rocker
box, and the pads and retainers go on the ground board. Assembly is
required, you will need contact cement or a similar adhesive, sand
paper to smooth any rough laminate edges, and a drill and screwdriver
to attach the PTFE pads.
Please measure the diameter of your Dob base to determine the right
size ring. Also, disassemble the ground board from the rocker box to
ensure there are no protruding fasteners that will interfere with the
installation of the ring, which is the case on some Orion XTi's. The
next smaller diameter ring may be needed. Installation instructions
Click on images to enlarge:
Prices include shipping in the USA!
10" Synta Dob Installation with 21" OD Bearing
Click image to enlarge:
Remove OTA from base and separate the ground board from the rocker
box. (This is a good time to clean off all the crud!) Position and center
the bearing ring on the rocker box and mark the outside position with
masking tape in three places. Use a high quality contact cement and
follow the manufacturers instructions for use and cleanup. (3M "Super 77"
is a great spray contact cement.) Be prepared for some mess! Contact
cement can be hard to remove from your scope, fingers, eyebrows, etc.
Prepare the ring by lightly sanding any rough edges. The goal is to remove
any roughness that will chew into the PTFE pads. Small chips and uglies
on the edges of the laminate won't affect operation.
Lightly coat the back of the ring with contact cement, press it in place
on the bottom of the rocker box to transfer cement to the box base, and
quickly remove it. Let the cement dry a bit, per the manufacturers
instructions. Position the ring carefully when adhering it using the
masking tape locators you put on. Once the cement grabs it is difficult
to remove the parts without damaging something! Press the ring to the
base to adhere it completely.
On the rocker box base, remove the three plastic glides. You may have to
pry them off with a screwdriver if they are stapled in place. The glides
are probably positioned opposite the ground board feet, where the new
pads will go. Make sure the staple holes don't stick up.
Measure the distance from the center hole to the center of the ring on the
rocker box base, and position the three pads on the ground board so the
center of the pads is the same distance from the center hole as center of
the ring on the rocker box. Mark the pad locations.
Use a 3/32" drill bit to drill pilot holes for the three pad screws, being
careful to only drill 1/2" deep. Now use contact cement to glue the pads
to the ground board and install the screws, and let all the cement dry per
the instructions. The pads and ring surfaces must be clean of contact cement!
Excess cement on the boards can be picked off when it drys a bit. Solvents
can be used but they may affect the board coatings. Nobody will see a bit of
excess cement between the two boards, but I didn't say that.
The combined thickness of the round bearings and pads may be different
than the thickness of the original glides, so the center axle and bushings
may need to be adjusted. Azimuth slewing should now be smooth and not
sticky. It's a good idea to periodically disassemble and clean the base.
It has been suggested that we are passing EbonyStar 4552-90 off as 4552-50.
We sell only Wilsonart 4552-50 and have plenty in stock! (Click to enlarge)
EbonyStar Strips are Here!