EQ8 users Video

[libraryman]

Hi, i have uploaded a video of an EQ8 dec axis being dismantled!

The reason for dismantling it was that it suffered from excess Dec axis Backlash.

Prior to the strip down, this measured a range from 1.8 secs to 2.5 secs...too much for imaging at high declinations, after reassembly; several checks last night under clear skies showed a reduction to 330ms for the dec axis and 440ms for the Ra axis which was adjusted at the same time...

NB: disclaimer....if  the strip down video is followed carefully and reassembled with care; the results that we achieved are possible..however it is your responsibility if it goes wrong.

the mount is not easy to dismantle, good Allen keys are needed and and a clean working environment with room and time to spare..

whilst we had the mount disassembled we took the opportunity to change the worm bearings on both axis...very similar to changing the EQ6 worm bearings so fairly easy to do that part..

It appears that for this mount, factory assembly was poor...and this was the main reason for the poor performance, however one we changed one aspect of the way we put it together, i.e. the top bearing on the main shaft was not tight enough !!!...the fit was a clearance fit that possibly allowed some radial movement of the worm wheel, in order to address this; we anodised the bearing journal to provide a Transition fit for the inner race..the lower bearing was left as a clearance fit...

if anyone needs further advice PM me...

also worth noting is that the initiative for this video was provided by Tony Owens who recently posted some information on the EQ8 Yahoo site..

further credits to the owner of this mount Mathew Foyle who provided the mount for dismantling..

 

follow this link for the video..

 

[libraryman]

[hughgilhespie]

Hi Ray,

Excellent video!! Looking forward to Part 2!!

Regards, Hugh

[libraryman]

Hey Hugh, how have you got on with your eq8 set up, not heard from you for a while

Ray

[ollypenrice]

Great video. I've a couple of questions...

When you say you measured the dec backlash to be in a range of 1.8 to 2.5 secs do you mean in arcseconds? Or maybe time seconds of delay in responding to a reversal command from the guider?

Also was the variabiltiy associated with the position of the wheel in ralation to the worm? If so, isn't there a likelihood of your being unable to lose the 0.7secs of difference between best and worst?

Olly

[libraryman]

Hi Olly...thanks for your comment...our measurement of the backlash is based upon how PhD assistant reports it.....I.e. Time to take up the backlash..

phd will send pulses of say....50 ms so for back lash of 2000 ms it take a considerable time  to reverse the backlash.

this is what you experienced with your mount! And PhD will not tolerate 2000 ms....as a compensation factor.

however it will compensate for 300ms and in terms of physical movement; 300ms is very difficult to detect....2000ms is easily noted.

i take your point about the position of the worm wheel, however..when measured we found little evidence of eccentricity in the worm wheel so we did not consider this to be a significant contributor to the backlash.

it important to note that any measure of backlash has to be completed under specific conditions I.e. Without any imbalance wich would potentially hide it.

So...the measurements were taken with neutral balance, repeated at Dec zero and at the zenith or near as damit.....

several repeats showed similar figures, confirming as best we can that the improvement was consistent...in addition a measurement of the pe showed a smoother wave form after renewing the RA worm bearings and guiding appeared to show an improvement consistent  with the other measures!

Having said all that; I'm always cautious about these things and more tests will hopefully back up the current info...

 

Regards Ray

 

[libraryman]

Just another point Olly, we have said that eccentricity of the worm wheel was not a factor..

however lots of mounts appear to show variability of backlash around the wheel.   We feel that this is due to the clearance fit of the top bearing and the way the clutch operates on the wheel bearing boss.

once the clearance fit was reduced to provide a tight transition fit, that movement was eliminated and the variability also eliminated!

 

Ray

[tony210]

Hi Ray - great  dismantle but unclear how you have remedied any short comings? - more info would be very welcome - thanks Tony

[libraryman]

Hi Tony...well, we did not expect the results that came out..when you consider how bad it appeared. 

so the first thing i did was to anodise the top bearing journal....this i estimated would add 10 to 15 microns to the diameter, i was cautious not to add too much....but that's average thickness for home anodising! and its quite tough as well..

The Worm Wheel bearing was a tad tighter than the taper roller inner race on the shaft but still a clearance fit. once the anodising was complete and i felt happy with the thickness gained, i put the shaft into the freezer overnight.

the bearings were cleaned and smeared with TF2 Lithium grease not too much, just enough!...the wheel was cleaned and air blown too remove residue and anything else that might have been on it.

The worm wheel, its attendant shim and the top inner race were fitted to the cold shaft, of course they fell on, after an hour warm up and stabilisation, i tested the fit of the bearing and wheel, it was just right in my opinion and crucially stayed put when inverted!

that was it for the Main shaft...the dec worm bearings were replaced with SKF ABEC 1 bearings since these we already had, we could have purchased the ABEC 5  quality but clearly at this time it was not necessary..

we used a sparing amount of red thread lock to the worm bearing housing and fitted them along with the cleaned worm.

on assembly of the main shaft, we preloaded the taper roller bearings to just ensure that end float and subsequent settling of the race would still leave a smooth running condition..

the loading of the worm bearings was just enough to remove the end float. 

other that that, the only other thing we did was to ensure that the worm lay parallel to the worm wheel, relying on the worm block back plate to ensure correct axial positioning of the worm relative to the wheel!...no reason to doubt that it is correct!

Greased the worm wheel with TF2...we wanted to use Aeroshell 64..but it was on back order and didn't arrive in time..

however we did take some considerable time to ensure backlash was minimal and consistent around 360 degs of the wheel.

That's it...careful assembly of the rest and it homed straight away, ......after.........a panic attack because Matt inadvertently put a slew speed of 2 in the hand set...thinking it was 9....but it was in hindsight the correct thing to do..

It sounded a lot smoother, ran like a dream and performed perfectly...

 

Ray

[tony210]

Thanks Ray- doesn't sound too easy as home anodising is something I have no experience of and you say you have replaced the DEC worm

 bearings - still I guess you have very clearly proved that you can  adjust the mount positively if you have the ability -best wishes Tony

[ollypenrice]

Thanks for your excellent and detailed additions to the video here, Ray. I think a lot of people will be glad to read that the Dec eccentricity does not necessarily come from a very obscure source.

I'm left wondering, as ever, how much more it would cost to make the thing more carefully in the first place and whether we wouldn't all rather pay that extra.

Olly

[libraryman]

This is fundamentally; the difference between low cost manufacturing and high end!    

When you are producing a product in medium numbers as is the EQ8, I suppose saving costs allows them to undermine to opposition (China is so good at this)

even the screws / set pins are missing essential washers..and cheese is used instead of a decent corrosion resistant material.

But, it also has to be acknowledged that though it is built down to a price, it does (at least in this example) appear to have the very important bits well made...

of course owners will have their own judgment and rightly so, dependant on their experiences and cost value.

As one owner pointed out recently....it has through mount cabling ability subject to modification.....(again built down to a price and abandoned)

It has base quality bearings and lack of attention to detail during assembly..all things that can be improved post sale ...if...the owner has sufficient skill?

so ultimately the question is.......is this a good mount, worth the money??

ill leave it there ?

[tony210]

Absolutely Ray-I wonder if mounts will be similar on disassembly or vary ?- I suppose one would guess some worse and some better - a lot of different reports out there but disappointing what eventually you have revealed in terms of apparent short cuts- a great tempter for careful adjustment for owners though and thanks for sharing - still not sure if  I want to embark on this myself but great video for us EQ8 owners - thanks Tony

[libraryman]

Yes it's a fair point Tony, my intuition tells me that there may be minor differences but it will be in the undoing of those infernal bolts with lock thread on them...good tools will be your friend here!

the anodising (most likely required) is another issue, I could offer to assist here but it's not my intention to profit from it. However if you need advice pm me!

Ray

[tony210]

Thanks Ray - best wishes Tony

[T Inglish]

Great video Ray, thank you for your time and effort.  Could you list the size of the Dec taper bearings if you still have that information.  I would like to source these locally.  I have owned my EQ8 for about two years and during this hot summer in Arizona I plan on doing some work on it.  I owned an EQ6 for 10 years and spent quite a bit of time modifying it.  I enjoy working on them as much as using them.  Always fun and satisfying to make improvements.  For the money I think the mount is worth it but as you say some things need attention.  Thanks again

Tim

[libraryman]

Hi Tim...the taper roller bearings are 32011.... The worm bearings are 608-2....

please post any improvement noted or indeed otherwise 

Regards Ray

[libraryman]

Matt Foyle has made a list of the EQ8 screws that could be exchanged for stainless if anyone else carries out the strip down following the video..

Matt and I have now completed a second strip down and rebuild of my mount...some observations are worth noting!

1. The fit of the bearings on the Dec shaft was slightly better, however I have followed the same anodising procedure just to tighten the fit though it was not strictly nessasary in my case but anodising adds hardness and eliminates any potential for galvanic corrosion.

2. The wireing is shrink coated not flat ribbon in the later mounts, my RA worm indexer cable was so short, I had to disconnect the board fron the cover in order to refit it!

3. A different grease was used on mine, a clear white grease as opposed to a red Unknown grease in Matts...

I have used https://www.amazon.co.uk/Finish-Line-Extreme-Fluoro-Syringe/dp/B006WH67JS/ref=sr_1_1?ie=UTF8&qid=1465634481&sr=8-1&keywords=finish+line+extreme+fluoro

no other differences of note...

 

Ray

 

 

EQ8 Fastner List 2016
Description	Thread	Length	Type	Quantity
DEC Saddle Retainers	M6	12mm	Socket Head Cap Screw	1	off
DEC Saddle Retainers	M6	16mm	Socket Head Cap Screw	2	off
DEC Encoder Cover	M3	10mm	Socket Head Dome Screw	6	off
DEC Worm Block Cover	M3	10mm	Socket Head Dome Screw	4	off
DEC Motor Cover	M3	10mm	Socket Head Dome Screw	1	off
DEC Motor Cover	M4	30mm	Cross Head Dome Screw	2	off
DEC Worm Adjuster Blanking Plug	M8	6mm	Grub Screw	3	off
DEC Worm Block Retainers	M5	15mm	Socket Head Cap Screw	4	off
DEC Worm Block Adjusters	M5	28mm	Stainless Socket Head Cap Screw	2	off
DEC Worm Block End Frame	M5	20mm	Socket Head Cap Screw	3	off
DEC Worm Block End Plate	M5	10mm	Socket Head C/Sink Screw	3	off
DEC Worm Block End Plate	M5	15mm	Socket Head Cap Screw	2	off
DEC Worm Cover Plate	M4	8mm	Cross Head Dome Screw	4	off
DEC Worm Adjuster Block	M5	15mm	Socket Head Cap Screw	2	off
DEC Worm Adjuster Block	M5	20mm	Socket Head Cap Screw	2	off
DEC Puck Retainers	M6	15mm	Socket Head Cap Screw	4	off
DEC Clutch Lever	M5	10mm	Socket Head Cap Screw	1	off
DEC Puck Side Retainers	M5	10mm	Socket Head C/Sink Screw	3	off
DEC Indexer "L"bracket	M4	10mm	Socket Head Cap Screw	2	off
DEC Indexer Cover	M5	15mm	Socket Head Cap Screw	2	off
Counter weight Threaded Boss	M6	16mm	Stainless Socket Head Cap Screw	4	off
Power Board Cover	M3	10mm	Socket Head Dome Screw	6	off
DEC Wiring Cover	M3	10mm	Socket Head Dome Screw	2	off
RA Motor Cover	M3	10mm	Socket Head Dome Screw	3	off
RA Worm Block Cover	M3	10mm	Socket Head Dome Screw	3	off
RA Worm Block Cover	M3	10mm	Socket Head Cap Screw	1	off
RA Encoder Block	M3	10mm	Socket Head Dome Screw	2	off
RA Stepper Adjustment Block Retainers	M5	20mm	Socket Head Cap Screw + Washers	3	off
RA Lower Inder Cover	M3	10mm	Socket Head Dome Screw	4	off