Username:

Password:

Altair AstroDIO DehumidifiersAtik CamerasModern AstronomyDavid HindsAPT

Author Topic: Dome Motorisation  (Read 205 times)

0 Members and 1 Guest are viewing this topic.

Offline petevasey

  • Poster God
  • *****
  • Posts: 1645
  • Plover Hill Observatory
    • Peter's Astronomy Pages
Re: Dome Motorisation
« Reply #45 on: 21:46:44, 17 March, 2017 »
This guy gave me an idea with his toothed belt drive.  For a few ┬ús (I already have suitable Aluminium bits for a frame) I can manage 4:1 or slightly better reduction within the diameter of my proposed acorn wheel which I would bolt direct to the larger belt wheel so wouldn't need a particularly strong main shaft.  A bit Heath Robinson although I would make bronze bushes for the main shaft.  Or even go posh with small ball races, but hardly necessary for such a low tech application.  Might be the best solution in the long run.  Even with my 112 RPM motor I'd get down to around 25 RPM loaded.  So should manage 5 rpm or less with PWM and probably plenty of torque.

https://youtu.be/hoxBkrD4xCo

Cheers,

Peter.
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

Offline petevasey

  • Poster God
  • *****
  • Posts: 1645
  • Plover Hill Observatory
    • Peter's Astronomy Pages
Re: Dome Motorisation
« Reply #46 on: Today at 16:43:26 »
Hi, Chris, hope you're still following this thread.

I've been quite busy over the last week or so  ;)   The PWM drive unit works well, still waiting for the interval timer, but that's not required for the main testing. 

I've never lubricated the plain bearing nylon support wheels on my dome, but thought it might reduce the turning load.  And it did indeed by around 40%. So I'm pretty confident my drive unit will do the business.    The toothed belt speed reduction is 72/14 teeth i.e. 5.14:1.  The driven wheels are held on their shaft by stepping the shaft with a nut on top, so although the shaft can rotate in its bushes, it's not actually doing any driving.  What looks like a bush between the driven wheel and the frame is actually a spacer with a very small clearance.  Just there in case the lower shaft collar slips.  The brass bushes for the main shaft are pressed into the frame.  But if they slacken and start to turn in future I'll use grub screws to fix them.

Slightly confusing in the photo, but the acorn wheel and large toothed wheel are bolted together - one of the two bolt heads is directly in front of the shaft nut. The motor mounting plate has a slotted hole for the bolt nearest the main wheel, for belt tensioning, and the hinge holes under the clamping plate are enlarged to enable final adjustments for level and height.

Still experimenting with hole size and spacing in scrap bits of wood to match the acorn wheel.  Once I'm happy with that it's onto the dome itself.  Probably make a jig for the dome drilling - an awful lot of holes to keep correctly positioned.  But I'll only do a few at first to test the system.  Also need a tensioning system to press the wheel against the dome rim.  But I've got a cunning plan for that (see those tapped holes behind the main shaft.)

Almost there!

Cheers,

Peter.
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

Offline chris.bailey

  • Administrator
  • Galactic Poster
  • *****
  • Posts: 8920
    • Rosemount Observatory
Re: Dome Motorisation
« Reply #47 on: Today at 17:29:22 »
Looks very good to me Pete. Does that motor 'feel' as thought its generating enough torque to turn the dome. Hard to judge I know but with one of the little Nema 17 steppers with a similar sort of timing cog on it is hard to stop the turn.

Chris
LX200|ZS70|FSQ85|FLT110|Altair DF250RC|EQ6 Pro(Rowan Belt Mod)|ParamountMX
ATIK383L+/EFW2/OAG|Lodestar|Baader 36mm LRGBHaSIIOIII
Starlight Express SXVRH16/ONAG/FW|Lodestar X2|Baader 2" Filters
Starlight Express SXVRH814/ONAG/FW|LodestarX2|Baader 2" Filters
Lunt LS60PTBF1200|DMK41|Quark Chromo

Offline petevasey

  • Poster God
  • *****
  • Posts: 1645
  • Plover Hill Observatory
    • Peter's Astronomy Pages
Re: Dome Motorisation
« Reply #48 on: Today at 17:46:25 »
Looks very good to me Pete. Does that motor 'feel' as thought its generating enough torque to turn the dome. Hard to judge I know but with one of the little Nema 17 steppers with a similar sort of timing cog on it is hard to stop the turn.

Chris

Hi, Chris, yes, even at a final RPM of around 6 there's more than 10 KG pull on the acorn wheel.  Very promising  ;)

Cheers,

Peter.
GSO RC10 Truss, Meade S5000 127, TMB 105, TS65 Quad, Solarscope SV50, Daystar Quark Chromosphere 'eyepiece' filter, Canon 15x50 IS Binos, various camera lenses.   Gemini G41 mount with Pulsar controller. EQ6 Pro mount, EQ3-2 mount with DS Autostar. Star Adventurer mount, QSI 683wsg, SX AO, Art285 (beta), Canon 350D (modded), Canon 700D, GPCAM2 (colour), GPCAM2 (monochrome), LE Vesta Pro, Toucam.

 

ukbuysellUKAI on FacebookSharpSkyblankSponsorship Opportunity
Powered by SMF 2.0.13 | SMF © 2006, Simple Machines LLC
DarkBreak by DzinerStudio. Theme modified by The UKAI Team

Page created in 0.233 seconds with 32 queries.
TinyPortal © 2005-2012