CGEM Project complete

[Explorer 190 MN]

Well finnaly finished tinkering with my mount:

Hardware

Edge 8HD or Skywatchers 190 MN DS PRO

Atik 314L+

TS OAG 9mm

Starlight express Lodestar

DIY Hypertuned CGEM

Celestron GPS

Kendrick Dew shield with built in heater band

Kendrick Heater control

Orion Piller extension

Kendrick astro tent

Logitech wireless gamepad

TS 2" monorail Dual speed focuser (not installed yet)

HP elitebook 2730p Tablet PC 2.3 Ghz 8GB RAM Touch screen, external battery 16h running time

2 x 12v 120 amp marine batteries

Software

Nexromte connected to MaxIm DL

Artimis captue

[x6gas]

Nice!

How do you control the mount using the gamepad? Is that a feature of Maxim?

Also would be great if you could post more info on hypertuning...

[fatwoul]

MN190 with 314L+. Good man. ;-)

[Explorer 190 MN]

Nice!

How do you control the mount using the gamepad? Is that a feature of Maxim?

Also would be great if you could post more info on hypertuning...

I have always thought of nexremote to be a bit dull úntill I read it is possible to control the mount using a Logitech gamepad.

Simplest way to do it is to buy a Logitech game pad as you skip messing with init. file.

Download the lastest nexromte released June 30 2012

Connect the R232 cable to the bottom of the hand controller

Connect the game pad to the computer.

Then Start nextremote

Right click on the Nexromte thingy on the screen select joystick and your of.

No more wrapping myself in cables or pulling things out of alignment

Set the virtual COM port on your on screen handcontroller to what ever COM number that works go into your ASCOM driver and set the COM port to the same number and MaxIm DL, Pem Pro, and what ever else you use will work........ but only one at a time or you need to buy nexhub I dont know if it works with Poth hub or not.

When it comes to the Hypertune Eds DVD are gold lots of little tips

Actually I think the problem lays in the retaining rings on the RA and DEC axes and possibly the worm gear retaining rings. I did see some minor scratches on the the ring gears indicating slight contact but nothing too bad. And if it is true that the retaining rings are too tight then you don´t really need to pull the mount apart to sort this out and the other main problem is definitely the contact between the motor gearbox spur gear and worm gear drive gear I am sure this causes a fair amount of periodic error I plan on changing these out to a belt driven system found some parts here I just need to work out the right sizeshttp://www.hpcgears....lleys_belts.htm and that should definitely take care of backlash there.

As for the backlash in the motor gearbox well I was thinking change out the pins the gears sit on to a better quality round bar that is actually round and not slightly triangular.

There is replacement motors these are cheaper to buy than from Celestron the gearbox is the same ratio but you need to transfer the nylon safety gear from the original and also the Encoder will need to be changed over. When/if I go down this road Ill just change over the gearbox as thats where the problem lays I think. Its because the gears are lose on the mounting pins. I did see some rough spots on these pins which I polished off under an eyeglass. I am guessing these pins are forged on rollers and I am guessing just now and then the odd gearbox gets a bad bit of bar causing loosely fitting gears. I also noticed the gearboxes have that old sticky brown grease in them which I recognize from my old CG5GT (which I had doing 10 min unguided subs at 1000mm fl with 16 kg!! after I tuned it myself) The CGEM motors are the same as the CG5GT advanced series motor.

I have also read it is possible to piggyback mount a motor drive chip on top of the old one to give it the same va va voof as the CGEM DX mount thus increasing motor power and max payload. I dont think my soldering skills are up to the job though. I may try to wangle a DX control board some how depending on price.

As for the Teflon shims (or Teflon bearings as Ed wrongly calls them) well I am not sure of how much gain there is to be had from them apart from them slightly better gear meshing reducing backlash a bit further. Diffrence is Celestron whack in shims at 0.100mm on the inside of the ring gear and most not all CGEMs need 0.05 mm and 0.20 mm on the otherside of the ring gear I cant unfortunately post any pics which have been sent with the kit because copy write laws ect.

I think by reducing friction in the entire drive train gives you the possibility to tighten the worm gear tolerances. I am going to build a thermally heated jacket for my mount as temps dip well past -20 some nights causing things to shrink after long hours.

Here is a very rough discription you really want to have the DVDs at hand because there is little tricks required that can only be shown.

Tools:

1.5mm Allen key (go get some good T-Handel type allen key)

2.5mm Allen Key

5 mm Allen key

C clip remover ( a good quality one)

Pump grips

Old spanner which you will need to grind down. ( There is a tool in the kit)

Plain screw driver

Philips screw driver

A vice

Digital vernier gauge (Not a micrometer as its called in the DVD, Micrometer is a different beast)

Plastic mallet

Wooden blocks

Fine plastic brush (in the kit)

De-greaser

Wet and dry sand paper from a bit coarse to really fine (in the kit)

Metal polish (in the kit)

Synthetic superlube you want something that will work at low temperatures preferably with Teflon base or better (also in the kit)

Leaving the mount head on the tripod

1. Take off your OTA saddle lay it to the side and replace the three screws in the top of the DEC axes

2. Remove the Polar finder scope

3. Remove Polar finder scope cover

4. Remove the little silver spur gear inspection screws and messure the distance from the housing to the spur gear write it down! insert screws again so you dont lose them.

5. Look to where the counter weight bar attaches to the mount you will see a small hole there turn the DEC axes and you will see 3 grub screws 1.5mm allen screws I think it was. Slacken these off a good bit dont need to remove them

6. Use your C clip remover to unscrew the DEC retaining ring almost until it is off.

7. Loosen the DEC worm gear adjustment screw

8. remove the DEC worm gear housing holding bolts

9. Place your hand over the DEC taper bearing and gently pull the DEC axes up, if its stuck just gently tap it with plastic bearing hammer. Now when the DEC axes comes up a bit the tapper bearing will fall out to keep you hand over it (infact place a towel or something soft under the mount to cushion the fall of parts just in case)

10. Place the DEC assembly aside watch for plastic spacers and where they come from.

11. Where your Polar finder scope sits under that plastic cap is your RA retaining ring and this is the same as the DEC retainer but 4 allen screw to slacken off. I took my mount head of the tripod went to the shed and with two wooden blocks gently held the retaining ring in the vice and turned to housing to losen this of then back into the house back on the tripod and continued to un-screw the retaining ring here agian place your hand over the tapper bearing and gently pull the RA housing out. Put it aside.

Ok now to DEC again here is the fun part

Carefully lift the ring gear assembly up out and off the DEC shaft do this with care and do it gently if it get even just a little bit stuck STOP! look to see which side is higher than the other and gently press it down failing that just tap it down gently until it sits in place again and start over I was lucky mine came strait off the first time. If there is a bearing left in the top of the DEC housing gently but firmly tap the end of the DEC shaft down ward onto your wooden block I used my hand at first but that get sore after a while

Now you have almost disassembled you DEC assembly.

DEC worm gear housing

Ed says to remove both plastic caps and retaining rings not necessary.

Look closely at the plastic caps and you´ll see a little indent a dart or even a little screw driver and prise off the plastic cap be careful under here you´ll find the

DEC worm gear retaining ring.

You´ll need to remove this with you C clip remover to screw this out to uncover the

Bearing retaining ring, this is where you need your ground down spanner Ill attach a youtube link where this is explained later in my post.

Losen the the two spur gear grub screws

If the worm gear doesn´t come out clean/easily check the grub screws are lose enough failing that find a suitable long punch and very gently tap out your worm gear please be very carefull with it you really don´t want to damage that, really don´t don´t fret to much its stainless and the housing is cast alu.

Congrats !! DEC dismantled.

Now clean all parts do not try to dry fot any part or they will get seriously stuck trust me..

Polish your ring gear by holding it loosely in one hand with your wet and dry and just twist it to try to fine slip it down. Don´t go mad! and then change to a finer grade with water and finally polish it up. Now take little superlube and smearer just a tiny amout all the way round the ring gear.

Check your DEC housing for blemished and paint in my case make sure it is clean and very carefully/slowly place your ring gear in there if there is even a hit that it might be sticking STOP gently pull it out or it will get stuck very stuck.

The whole point of this fine sanding of the ring gear is to be able to put it in and out of hte housing with out it getting stuck I spent some time on this and was able to get it to spin very freely with out grease. I dry fitted mine right of the bat and almost got it stuck once.

Clean of and worm gear and spur gear only with soft cloth and soft plastic bush I used a business card to clean the worst out and a microfiber cloth and de-greaser for cleaning motocross airfilters poisonous stuff but works good not ever to be pured down toilets or drains or near any water it is poisonous!!

Ok time to replace bearing if you like to the ceramic ones tap em out press in the new ones just a tiny bit of grease there on the out side of the bearing back in with your worm gear and on with your spur gear tighten up grub screws on spur gear now worm gear retaining ring look to see when it meets the bearing. Spin the worm gear with your finger until it spins just right, use your head you´ll know when it is tight enough a dab of thread lock glue and now check the spur gear distance which you wrote down earlier. Now lube up your worm gear.

In with your plastic shims or telfon if you bought them

Same procedure for RA and then put it all back together

When you tighten up your retaining rings use commen sence I just made mine hand tight and tightened the grub screws checked for play. I think by only releasing the pressure on this retaining rings would make loads of difference.

Don´t tighten the worm gear housing screw too much just nip them. Adjust the RA and DEC backlash with adjustment screws until just a little bit of play is felt.

Best way to fine adjust backlash there is by ear go back and forth until it sounds smooth all the way from left to right tighten up worm gear housing screws and re-check for free running from side to side, do not try to make this adjustment with un-balanced mount you will damage the gearbox.

After its all together again place the mount on it side and remove the motor control board pull the plugs out and now loosen the motor allen screws place mount back on tripod balance it with OTA ect plug plug in the motorboard again, remove the spur gear inspection screws by using the direction keys look foe backlash between the gears this can be adjusted by moving the motors up and down carefully with a big screw driver and run the motors and listen there is a very fine balance here between too much and too little. You will hear the diffrence.

This is just a very rough guide and I assume no responsibility if it all goes pair shape.

The heart of the hypertune kit is the DVD that follows with the kit although Ed drops stuff calls it by the wrong name and forgets things its a good guide.

I would just slacken of the retaining rings a bit first and and tighten them to see if that helps if not pull it apart. I am glad I went all the way with mine.

Good luck!!

Here is what I found wrong with my mount

1. Lose OTA saddle. (apparently this is common) (=BACKLASH)

2. Paint spots inside RA ring gear housing and also blemishes in the housing. (=FRICTION)

3. Both RA and DEC ring gear slightly over sized. (=FRICTION)

4. Stiff worm shaft bearings due to incorrectly adjusted retaining rings. (=FRICTION)

5. Incorrectly adjusted RA and DEC retianing rings. (=FRICTION)

6. Incorrectly adjusted DEC motor spur gear. (BACKLASH)

7. Alt adjustment Handel moulded on adjustment bolt out of line. (CAN BE USED AT GREATER THAN LAT 60)

8. Alz. Pin on tripod lose. (= EASY TO UPSET POLAR ALIGNMENT)

9. Incorrectly adjusted spacing for correct worm gear to ring gear meshing. (BACKLASH)

10. Incorrectly set DEC marker (causing first alignment star to be out I field of view.)

11. Incorrectly set spirit level on mount.

12. Holding pins in the motor gearbox out of true and grease thick like glue. (FRICTION AND LOSS OF MAX CAPACITY)

Youtube link

[x6gas]

Many thanks!

[Explorer 190 MN]

I am sure this will become a popular post...... the only post of its kind on the CGEM

[x6gas]

Just want to say thanks again for posting the information in this thread Explorer 190MN. Armed with this, the information in your Hypertune thread http://www.astro-baby.com/EQ6%20rebuild%20guide/EQ6%20Strip%20Down%20Home.htm and the information on Astro Baby's website on the EQ6 / Orion Atlas http://www.astro-baby.com/EQ6%20rebuild%20guide/EQ6%20Strip%20Down%20Home.htm I've just finished a strip down and rebuild. I yet to test it under the stars but my initial impression is that it is much improved.

Cheers!