Zdobienie / Decoration

iOptron CEM 25P – RA axle bearings replacement

Zdobienie / Decoration

iOptron CEM 25P – RA axle bearings replacement

Introduction

English is not my natural language. I have put my best effort of my ability, to ensure that the translation of this document is accurate. I certainly did not avoid mistakes, so please, if you have found a mistake, or if you can express the same thought better from my writing, feel free to write to me pointing out what could I improve by giving an example.

This document describes the replacement of a pair of RA axle bearings, for the iOptron CEM25P mount. It certainly does not exhaust the topic, although I tried to include, in this description the most important information, that I was able to gather during my struggles, that I encountered during the replacement process of bearings.

 

Description of the problem: during rotation, bearings liked to “brake” the entire RA axis. The symptom was present permanently especially at the temperature of 25C++

After disassembling the axles and removing both bearings, turning them in hands, there was a slight resistance locally. These were poor quality products or damaged during assembly. Clearly, they had to be replaced with new, appropriate quality products. The method of disassembling the old and assembling new bearings is described below.

ATTENTION! The following steps require some practice, if you do not confident to do it, will be better with assembly to trust someone, who is skilled enough and will not be more difficult for him to perform all the activities described below. Certainly, this description is not error-free, so be aware of it. I do not take any responsibility for any damages caused with use of this document.

 

Necessary tools and some chemicals

New bearings, model: 6907 ZZ EZO, 2 pcs per axis

iOptron CEM25P - bearings
iOptron CEM25P – bearings model: 6907 ZZ EZO
Smar litowy uniwersalny CX80
Multipurpose lithium grease CX80

A set of auxiliary tools:

  • Allen key set,
  • a small toothbrush,
  • pliers,
  • small angled pliers,
  • small wrench,
  • a small art brush,
  • metal hammer
A set of auxiliary tools:
A set of auxiliary tools

 

Disassembly of the components of the RA axis

Take a picture of the assembled mount, just before taking any action, so that after disassembling it into parts, you will know what state you should return to.

iOptron CEM25P
iOptron CEM25P

Remove both caps of the polar finder.

iOptron CEM25P - cap of the polar finder
cap of the polar finder
iOptron CEM25P - cap of the polar finder - back
cap of the polar finder – back

Manually unscrew the eyepiece of the polar finder.

iOptron CEM25P - eyepiece of the polar finder
eyepiece of the polar finder

Remove the DEC body cap using the small angled pliers.

DEC body cap - iOptron CEM25P
DEC body cap
iOptron CEM25P - DEC body cap
Removed DEC body cap

Unscrew the polar finder illuminator using the small angled pliers. Remember to not squeeze much the illuminator housing. Be gentle.

iOptron CEM25P - polar finder illuminator
polar finder illuminator

Remove the two outer bolts connecting the DEC body to the RA axle body, using the right size allen key.

iOptron CEM25P - outer bolts
outer bolts

Remove the top inner screw using the right size allen key.

iOptron CEM25P - top inner screw
top inner screw

Remove the inner bottom bolt, that connects the two bodies using the right size allen key.

iOptron CEM25P - inner bottom bolt
inner bottom bolt

With one hand, grab the DEC body and the other hand, on the RA axle body. Moving from side to side with the DEC body, pull off slowly, until all is removed from the RA sleeve.

iOptron CEM25P - DEC body removed
DEC body removed

Remove the three allen screw head cap, securing the counterbalance bar holder.

iOptron CEM25P - three allen screw head cap
three allen screw head cap

Remove the holder. It fits very tightly, so a little force should be used to remove it.

iOptron CEM25P - older removed
holder removed

Remove the three bolts, securing the RA axle gearwheel cover, using the right size of allen key.

iOptron CEM25P - three bolts of the RA cover
three bolts of the RA cover

By hand, pull the cover off.

iOptron CEM25P - RA cover removed
RA cover removed

Remove the three screws securing the nut, that adjusts the pressure of the gear wheel to the bearing, using an allen key of the right size.

iOptron CEM25P - screws securing the nut
screws securing the nut

Unscrew and remove the nut.

iOptron CEM25P - unscruwed nut
unscruwed nut

Remove the three screws securing the RA axle gearwheel using the right size an allen key.

iOptron CEM25P - three screws securing the RA axle gearwheel
three screws securing the RA axle gearwheel

Remove the gear wheel.

iOptron CEM25P - RA gear wheel removed
RA gear wheel removed

Clean the gear wheel from old grease and possible fine dirt, using a small tooth brush. After collecting dirt, clean the tooth brush with a towel paper.

iOptron CEM25P - Cleaned gear wheel
Cleaned gear wheel

Apply a small amount of grease to the sleeve to slide the bearing off.

iOptron CEM25P - slide the bearing off
slide the bearing off

Grab the body with your hand and gently, with the hammer tap the edge of the sleeve.

iOptron CEM25P - slide the bearing off nr 2
slide the bearing off

When the sleeve comes out of the bearing, the bearing can be removed from the body seat.

iOptron CEM25P - sleeve comes out of the bearing
sleeve comes out of the bearing
sliOptron CEM25P - sleeve has been removed
sleeve has been removed

Inside the body, where the sleeve was, you can see the bearing that needs to be removed. It is placed quite tightly. Use gentle force to remove them. Use the largest size an allen key and a hammer, tapping lightly and evenly the edge of the entire bearing surface to extract the bearing.

iOptron CEM25P - extracting of the bearing
extracting of the bearing

The second bearing has been removed.

iOptron CEM25P - second bearing removed
second bearing removed

The photo shows both bearings that needs to be replaced.

iOptron CEM25P - both bearings to replace
both bearings to replace

 

Assembly of new bearings and RA axle components

Before installing a new bearing, carefully clean the surface mounting points. A paper towel was used for cleaning.

iOptron CEM25P - clean the surface mounting points
clean the surface mounting points

Apply a small amount of grease to the bearing seat.

iOptron CEM25P - grease to the bearing seat
grease to the bearing seat

Use a brush to spread it over the entire surface. This will make it easier to seat the bearing.

iOptron CEM25P - spread it over the entire surface
spread it over the entire surface

Seat the bearing and gently press down on the outer edge of the bearing, to push the bearing into the seat.

iOptron CEM25P - Seat the bearing
Seat the bearing
iOptron CEM25P - bearing has been seated
bearing has been seated

Precisely clean the RA axle sleeve with a paper towel and a cotton cloth or rubber. Make sure that there are no scraps of paper and other particles on the sleeve, that could later make a harder assembly.

iOptron CEM25P - clean the RA axle sleeve with a paper towel
cleaning the RA axle sleeve with a paper towel

Apply a small amount of grease to the sleeve and use a brush to spread it precisely over the entire surface.

iOptron CEM25P - amount of grease to the sleeve
amount of grease to the sleeve

Slide the sleeve into the bearing seated in the mount as shown in the photo. Make sure you are installing the correct side of the sleeve.

iOptron CEM25P - Sliding the sleeve into the bearing
Sliding the sleeve into the bearing

You should tap lightly on the end of the sleeve, so that the whole passes through the bearing.

iOptron CEM25P - tap lightly on the end of the sleeve
tap lightly on the end of the sleeve

Clean the RA Axis worm with a small tooth brush and paper towel. Brush the dirt off with paper piece. This method is quite tedious but brings the intended effect.

Photo before cleaning.

iOptron CEM25P - cleaning worm with a small tooth brush
cleaning worm with a small tooth brush

Photo after cleaning.

iOptron CEM25P - Cleaned axis worm
Cleaned axis worm

Apply a small amount of grease to the seat of the second bearing and use a brush, to spread it over the place, where the bearing will seat.

iOptron CEM25P - amount of grease to the seat of the second bearing
amount of grease to the seat of the second bearing

Install the second new bearing on the RA axle sleeve. Use sufficient force to push the bearing over the shoulder of the sleeve and insert it into the seat.

iOptron CEM25P - Installing the second new bearing
Installing the second new bearing
iOptron CEM25P - Installed second new bearing
Installed second new bearing

Once the bearing is seated in its seat, perform a simple test, to see that the RA axis rotates smoothly. A simple test is shown in the video below.

simple test

Apply a small amount of grease to the sleeve, just above the bearing, where the RA axis worm gear will be installed.

iOptron CEM25P -small amount of grease to the sleeve
small amount of grease to the sleeve

Cover the RA axis worm with a little grease and a brush.

iOptron CEM25P - grease and a brush
grease and a brush

Install the RA axis worm wheel gear.

iOptron CEM25P - Installed RA axis worm wheel gear
Installed RA axis worm wheel gear

Install the black nut that adjusts the pressure force of the gear wheel. Screw it gently. The RA axle body should rotate around the sleeve very lightly and freely, without any noticeable resistance.

iOptron CEM25P - Installed black nut
Installed black nut

Use three hexagon socket screws to lock the nut. When tightening screws, resistance may occur as you twist the body around its axis. IMPORTANT: tighten the screws (lightly!), so that there is no resistance when turning the body around the sleeve axis.

iOptron CEM25P - three hexagon socket screws to lock the nut
three hexagon socket screws to lock the nut

Screw in the three allen locks and lock the sleeve. There may be unexpected resistance when rotating the body around the sleeve axis. IMPORTANT: Tighten the allen screws until there is no resistance.

iOptron CEM25P - three allen locks
three allen locks

Install the RA axis worm wheel gear cover and fasten with three allen screws.

iOptron CEM25P - axis worm wheel gear cover
axis worm wheel gear cover

Install the counter balance bar holder and lock it with the three allen screws.

iOptron CEM25P - counter balance bar holder locking
counter balance bar holder locking

Put on the polar scope and lock it in place, by carefully tightening the two allen screws.

iOptron CEM25P - polar scope locks
polar scope locks

Screw in the polar finder lens.

iOptron CEM25P - polar finder lens
polar finder lens

Remember to adjust the scope to the chosen, distant point, preferably a star.

iOptron CEM25P - adjusting the polar scope
adjusting the polar scope

EXAMPLE: a window corner on the opposite building was selected for this purpose. The photo of the polar target was taken with a phone, that is not perfectly aligned with the polar finder. Hence, the view of the shape of view is some what elliptical.

iOptron CEM25P - window corner on the opposite building
window corner on the opposite building

Apply a thin layer of grease to the RA axle sleeve.

iOptron CEM25P - thin layer of grease
thin layer of grease

Insert the shorter screw into the other half of the body, on the inner part using the small angled pliers.

iOptron CEM25P - shorter screw into the other half of the body
shorter screw into the other half of the body

Put on the other half of the mount, in such a way that the screw inside, reach the appropriate hole. Grip the screw with a wrench and lightly screw it into the body.

iOptron CEM25P - screwing other half of the mount
screwing other half of the mount

Use the right size of allen key, to screw the second inner screw onto the body.

iOptron CEM25P - screw the second inner screw
screw the second inner screw

Screw the mount with the two, longer screws using the right size of allen key.

iOptron CEM25P - two, longer screws
two, longer screws

Attach the polar finder illuminator by hand or using small pliers.

iOptron CEM25P - polar finder illuminator
polar finder illuminator

Attach the cover by hand or with a pair of pliers.

iOptron CEM25P - polar cover cap
polar cover cap

 

Test to verify the appropriate of the bearings replacement

Attach the mount to the tripod. Attach the counter balance bar to balance the mount in the RA axis. Unlock the RA axis in such a way, that the mount starts to slowly rotate itself. This operation is shown in the video below.

If the mount rotates freely in both directions, without any noticeable resistance, it can be assumed that the replacement of the bearings was successful.

Put the astronomical equipment on the assembly as you usually do. Start the mount and use the controller to make a few full turns in both directions. If during the rotation of the mount in the RA axis, there were no unexpected sounds of friction, scraping and the mount, did not stop unexpectedly, it can be said that the operation of replacing the bearings (in my opinion) was a completed with success.

Of course, the best and final test will be, going out into the field with full equipment and testing the equipment during beautiful night with stars.

 

Version: 0.7

Date: 06.11.2021

Corrector: Aleksandra Kosmala

Author: Dariusz Krzempek

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