Equatorial Platform Drive Parts

Aprid · #1 14-06-2006, 02:28 PM

G'day I am a total newbie and Having purchased an 8 inch dob early this year and become tired of nudging it along i decided to build an equatorial platfom all is going well the actual platform is assembled and working fine I have the electronic side of it sorted out , but am wondering if anyone else has been down this route and knows of "one stop shop" where the other mechanical drive componets could be purchased eg. threaded rod, bearings for the rod ,pulley and belt to suit, gear reduction parts etc. rather than hunting around for individual components.

I love this site there is a wealth of information here.

ving (David) · #2 14-06-2006, 02:41 PM

hiya aprid

welcome aboard

jaycar?

joe_smith · #3 14-06-2006, 04:13 PM

what electronics did you use? sound like a good idea. what plans did you use?
dont know of a place to get it all from in one hit, someone should know.

mick pinner · #4 14-06-2006, 06:36 PM

hi Aprid, most places are pretty specialised now so a one stop shop is pretty rare, try Ferntree Gully bolts 766 Burwood H'Way for threaded rod and mounting plates etc, Bayswater Bearings Barry St Bayswater will have the bearings and probably the reduction gears you need, for anything and everything else try Petes Bargain Centre Maroondah H'Way Ringwood.
Best of luck, any other info PM me.

Aprid · #5 15-06-2006, 02:27 AM

Thank for the info I suppose I wont get too leg weary travelling around Bayswater and Ferntree Gully. The plans were from Yahoo groups equatorial platforms by Warren Peters includes a nice Excel file for all the dimensions. I'll just see how I go with simple pulse width modulated speed control kit from jaycar with a 12v motor I had lying around. I suppose a stepper motor would have been a better choice but I'm just trying to keep it simple.
Thanks for the info and your interest.

DavidH · #6 15-06-2006, 09:55 PM

Hi Aprid,

I am building an eq platform too. 2 sector cylindrical version. Using stepper motor and Atmel controller for electronics. Tried a wire drive for a start, but ended up with too much friction for the motor to cope with, so went back to a threaded rod drive. The rod came from the local hardware store, sold in about 900mm lengths. For bearings, I went to the local recyclers at the tip, and purchase a set of used inline skates for $4. These had 4 wheels per skate and 2 bearings per wheel, so had plenty of bearings to play around with. Just be careful as not all skates have decent bearings.

At present am playing with some limit switches and a handpad to give me some control over the drive.

Regards,
David.

Starkler (Geoff) · #7 15-06-2006, 10:50 PM

Remember that if you use a stepper motor that each discrete step should translate to 1 arc second or less at the telescope. This translates to 15 steps/sec or greater for a shake free view at high magnifications.

DavidH · #8 16-06-2006, 11:24 AM

Quote:

Originally Posted by Starkler

Remember that if you use a stepper motor that each discrete step should translate to 1 arc second or less at the telescope. This translates to 15 steps/sec or greater for a shake free view at high magnifications.

Thanks Geoff,

Your post has caused me to recheck my calcs, since the threaded rod drive is slightly different to my original planned wire drive. Turns out about right with a 650mm radius south sector, and a 200 step motor in half step mode. Do not want to go much below 1 arcsec/step as I intend resetting the mount by running the motor backwards rather than by mechanically disconnecting from the drive. Having a smaller step size will reduce the speed of the reset. Yet to be seen if this actually works, of course, but its all good fun.

Regards,
David.

Aprid · #9 16-06-2006, 02:07 PM

Thanks I must have got ripped off I paid $5 for a pair of roller blades at the local opp shop but anyway after a bit of googling I think I may have come up with what I was looking for at www.smallparts.com.au gears,pulleys belts etc, so if I do a bit of maths at the weekend I should be able to simply order the req'd components and come up pretty close to the req'd R.P.M. and it "should" just slip together . Scavenging is good but the problem is with the different shaft and bore sizes that you would eventually finish up with which I was hoping to overcome, as you said its all good fun and if it works it's greatl and if it doesn't back to the drawing board.

Thanks
Aprid.

ashley.gale · #10 23-06-2006, 11:47 AM

Hi Aprid,
You were in a similar situation to what I am now, but I have salvaged some stepper motors and no idea about the electronics. Does anyone know how to connect a stepper motor to my computer?

Regards
Ashley

DavidH · #11 23-06-2006, 02:07 PM

Hi Ashley,

Jaycar.com.au sell a couple of pc driven or standalone stepper drivers (Cat Nos AA0352 and KV3594.) Another good place to start learning about steppers and telescopes is Mel Bartels website www.bbastrodesigns.com.

Have Fun,
David.

Aprid · #12 08-07-2006, 12:22 PM

Well the parts I ordered finally arrived the drive mechanics were easily assembled and the platform tracks well enough for visual use.Obviously I've done a bit of overkill with the platforms size and weight in an effort to keep it steady, the next project will be to bulid another but to trim down the size to make it more portable and perhaps use a stepper drive instead of a DC motor which does distract with its constant whining. Anyway it's nice to be able to concentrate on viewing without having to nudge the scope along.

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Thanks,
Aprid

joe_smith · #13 08-07-2006, 03:40 PM

looks good Aprid, glad you sorted it all out mate. I built the jcar stepper kit I might have a go building one. Get ready for the million questions

You should be able to put a web cam in to get some AVI's. your on your way now

netwolf · #14 09-07-2006, 12:37 AM

Hi Aprid,

Good job there, this is on my wish list of things to get. I could manage the electronics but the wood and metal work is out of my bag of tallents.
Would you be able to advise what the all up cost and time was to build the platform?

Regards

Aprid · #15 09-07-2006, 11:18 AM

Hi Netwolf

As to the time it took it was a couple hours each weekend over a few weeks my woodworking skills go back to year 10 which I have not used much in the past 35 years so if I could do dit anyone could, but I do have access to a CNC equiped sheetmetal workshop where the Aluminium brackets to hold the North & South bearings at the correct angle plus brackets for the rod and motor were folded at zero cost. The total cost abut $20 for some 12mm craftwood at Bunnings which was too thin for the project and had to be braced underneath with some timber scraps I had lying around, the dc gearhead motor and controller I've had sitting around for a couple of years another project that didn't get off the gound, I suppose it cost about $50 back then, the threaded rod a couple of bearings 2 pulleys and a belt came to $80 at smallparts.com.au and some $5 skate wheels. Now that I see how it works if I was to build another I would go for a welded aluminuim frame for the baseboard and groundboard, and would substitute the DC motor whith a stepper motor for accuracy and silence.

Thanks
Aprid

netwolf · #16 09-07-2006, 11:48 PM

Yeah i did some machine shop back in highschool, but the only thing i learned was that i really was no good at it. U may even recall me i am the one who kept geting shouted at by the teacher for doing something wrong. Like i dont know not tying my appron, and using the plastics buffing machine. And hmm having the whole class and the teacher stare at me after the teacher hit the emergency stop and wondering why. And then noticing the nice neck tie apron inches from stranagling me... oh school days werent the fun..

I have spent quite some time on the eq platforms group and have a good understanding of the physics and electronics. But the wood/metal work is what stops me. I can probabaly manage some rough sketches, and then get someone to make them up.

How is your platform peformaing at high magnifications.

Regards

Aprid · #17 10-07-2006, 02:54 AM

IT seems O.K managed to hold Jupiter pretty much centered for about 15 ~ 20 minutes at 200X just levelled and pointed South with a compass no further allignment done. There didn't seem to be any vibration from the drive but wind is a bit of problem it was a bit unsteady, possibly caused by too soft a compound in the skate wheels plus the pin attaching the base board to the threaded rod is a tad loose. Just a few minor things to look at, all in all I am happy with it at this stage. For us mere males who can only concentrate on one thing at a time, looking through an eyepiece and nudging a scope along when up is down and down is up is a very complex operation and anything that can simplify that is a good thing.

Thanks
Aprid

Hosaka Kiyoshi · #18 20-07-2006, 11:02 PM

Hi,Every member,
I'm a newby for this forum who live in Japan and an EQP builder. I'm now building one with threaded rod and a rack(like a worm wheel and a gear). I purchased two same threaded rods 10mm in dia., and I have flatened one with a disk grinder to be able to be bent along the R of the north sector.
To turn another rod as a worm gear, I made a driver for a stepper motor according to a circuit on a website.
http://web.telia.com/~u41105032/Stepper/Stepper.htm
This circuit is really great. A threaded rod can be turned directly by a stepper(without reduction gears) 1-2 rev. per minuite silently and vibration free.This circuit has a great function that rewinds automatically in a minuite or two when reaching to tracking end.

Regards,
Hosaka Kiyoshi

alistairsam · #19 13-12-2009, 01:10 AM

hi everyone,
i just got myself an 8" Dob mounted F6, and am about to start off on the two sector eq platform. i came across the excel sheet for the calculations, but had a few doubts. could someone please help with plans or diagrams for the platform.
variables in the sheet are height of c.o.g, base size, and then A and B. how do we calculate A and B.
i'm in melbourne, so how do we apply lat 38deg. 38 deg from azimuth or horizon. reason i ask is some eq mounts have 90 deg markings at azimuth, some have at horizon which is a bit strange.
i wanted to get started with the platform first and then get to the electronics. woodwork is not a problem.
i was planning on using small bearings and transfer bearings as per the original plans.
but some diagrams and plans for australia would help.
thanks

Starkler (Geoff) · #20 13-12-2009, 12:51 PM

Quote:

Originally Posted by alistairsam

variables in the sheet are height of c.o.g, base size, and then A and B. how do we calculate A and B.
i'm in melbourne, so how do we apply lat 38deg. 38 deg from azimuth or horizon.

You need the virtual axis of your platform to point to the SCP, which is 38 degrees up from the horizon. Any star atlas program can verify this for you.