Pulsar 2.2m Dome Lesvedome Drive

[SnakeyJ]

It's taken nearly three years to get to this point, but I'm finally getting around to automating my dome (a new style Pulsar 2.2m dome), which I brought second hand back in 2017.   To be honest most projects have been held in obeyance with work and my daughters continuing care needs, but 'all work and no play' would be dull and I'm gradually shaking everything out ready for some summer glob hunting and Mars.    As I'm now swinging a 14" meade ACF, there is precious little spare space within the observatory and I generally end up having to crawl around on my knees to avoid the scope and counterweights.   The plan is to automate azimuth only at this stage, so I can retreat indoors and control things remotely.    I might add shutter control in later depending on time and money, but not a priority at this stage.

 

No great invention, but following in the footsteps of giants, I've decided to go for the Lesvedome ascom driver, with a belt, pulley and encoder setup (similar to @Steve 1962 setup

Although my dome is simpler to do, the fibre glass moulding are quite irregular, so I've trued this up by routing the bottom of the lip level and I've steamed/bent some pine strip  which I will skim with the router to get an even surface for mounting the belt.

never enough clamps when you need them!    The sharp eyed may notice that I painted the inside of my dome with underseal to cover the flaking paint - don't repeat my mistake!

 

Still waiting for the relays, some heavy aluminum angle and a few bits from the postie, but have my motor, belt, pully and the Vellerman board ready to go.  I went for the 15mm wide HDT5 belt and pulley from belting online  - this was quite a bit cheaper than T10 and finer pitch, but feels very positive.    I rounded up and went for 6.4m, which should allow a little slack after I've reduced the internal diameter by 5mm or so.

 

Bit of a WIP at the moment, but hope to start assembly over next weekend.

 

 

 

[sloz1664]

That's coming along nicely. Remember to spring load your motor onto the track as there is a fair bit of movement as the dome rotates. I can't believe it's coming up to 3 years since I added the drive motor and it has worked flawlessly.

Btw how are you bonding the HDT5 belt to the pine strip?

 

[SnakeyJ]

28 minutes ago, sloz1664 said:

That's coming along nicely. Remember to spring load your motor onto the track as there is a fair bit of movement as the dome rotates. I can't believe it's coming up to 3 years since I added the drive motor and it has worked flawlessly.

Btw how are you bonding the HDT5 belt to the pine strip?

 

HI Steve,  I'll follow your lead with the Evostik Impact for this.  I used Gorilla glue to fix the pine to the fibre glass, as it has good gap filling properties, but otherwise pretty horrible to work with!

I've got the springs ready, but waiting for some aluminium angle to construct the motor mount.   I might see if there's a good way to mount the encoder closer in for protection, even if it involves a pair of spur gears.

Edited May 31, 2020 by SnakeyJ
missed sentence

[Jkulin]

Hi, your videos are coming up with the following, perhaps it is a permission issue: -

[SnakeyJ]

Minor setback - unfortunately the Gorrilla Glue did not bond well to the fibre glass (probably the underseal), so I decided to bolt the timber ring in place.    It took a few days for the stainless countersunk bolts and bits to arrive and something like 90 fixings for the 6.3m circumference. 

 

 I've filled all the holes and gaps now with car body filler and, once I work out how to mount the router, I will skim the inside of the ring to true it up before fixing the belt.

 

I'm still waiting for the aluminium angle and relays to drive the motor, so probably about as far as I can get this weekend. 

[SnakeyJ]

It's been quite a challenge to find a safe and solid way to mount my router and allow me to round out and true up the timber drive ring.    After several attempts I made up some aluminium foot plates for the base of the router and a clamped frame to allow me to slide it in and out.   Not perfect, but it's taken most of the eccentricity out of the inner ring of the dome. 

 

  

[x6gas]

Great to see this project progress Jake - very envious!

[SnakeyJ]

I had to turn up a shaft to mount the drive pulley and encoder.    Poor quality steel, but a bit of recycled weight lifting bar.   The bit was turning a 10mm to 8mm 10.5 deg internal taper in the end to cover the spline and screw tight to the thread of the windscreen wiper drive shaft.   A little rough and ready, but certainly man enough for the job.

Now to come up with a solid mounting plate to secure this to the curved outer wall of the dome....

[Jkulin]

Sorry Jake, but I still can't see any of your videos, they all have a no entry sign.

[SnakeyJ]

9 hours ago, Jkulin said:

Sorry Jake, but I still can't see any of your videos, they all have a no entry sign.

Hi John, apologies this link is not working, but the link was not my video but a quote showing Steve's (Sloz1664) own of his belt drive in his converted mk1 Pulsar dome.     The link works fine for me, but resolves to an MP4 upload on this site.  https://stargazerslounge.com/uploads/monthly_2020_05/1073342923_DomeRotation.mp4.c74559901b811422d0cdbb2a0cdf16f3.mp4     

[SnakeyJ]

Some progress in the workshop - I've completed the motor mount.

Kit of parts:

Assembled:

 

The springs are old collimation springs from my OO VX 250, I might have to cut them down a little if too stiff - but allow 8mm travel to keep tension on the belt.    I cut some HDPE washers from a milk bottle to reduce the friction on sliding, the bolts are threaded and countersunk in the top part and have 10mm slots milled in bottom bracket - this cost me two 5mm hss end mills, trying to do this in one pass in 6mm aluminium!   The gold washers were inherited, I believe they came from Saunders-Roe/British Hovercraft and were used for rivetting the skirts together.

 

The motor is three wire, with red, black and blue wires (I disconnected the polarity reverse switch under the gear box).  Red to 12v+ / black -ve gives the fastest rotation and blue to 12V+/ black -ve gives a steady half speed and more torque.

Mounting anything to the wall of a dome is a bit of a pain, so I've used copious amounts of Gorilla construction adhesive to glue mounting timbers - I even have a little shelf for the dehumidifier.     

Once this goes off, I'll pack out and mount the motor bracket.   Once I have this in place I can glue in the belt and see how it drives.       I'm stil waiting for the relays, but everything else is ready to go.

 

 

 

 

 

 

Edited June 27, 2020 by SnakeyJ
Photos weren't showing up

[sloz1664]

Unfortunately Jake, I cannot see any of your pics. They also are showing "no entry sign" logo.

 

Steve

[SnakeyJ]

12 minutes ago, sloz1664 said:

Unfortunately Jake, I cannot see any of your pics. They also are showing "no entry sign" logo.

 

Steve

Sorry Steve, the links from Google photos weren't working.   I've uploaded the images to SGL and changed the links.

[SnakeyJ]

Belt and motor installed and we have rotation!

The noise at the end was the power supply falling off the humidifier, which concluded this test - no harm done and already to go once my relays arrive....

 

 

Edited June 29, 2020 by SnakeyJ

[SnakeyJ]

Thankfully the relays arrived today.   I'd been rather taken in by amazon and these had definitely been on the proverbial long slow boat from China, taking five weeks to arrive!  On the plus side it was cheap!

https://www.amazon.co.uk/gp/product/B07BKXTMPL/ref=ppx_yo_dt_b_asin_title_o07_s00?ie=UTF8&psc=1

 

Now I just need to work out the circuit diagram http://www.dppobservatory.net/DomeAutomation/Schematic.pdf and work out how the relays match in.     A bottle of wine and some late night project boarding over the weekend should do the trick....

 

Edited July 2, 2020 by SnakeyJ