Home made EQ with tracking for big reflectors

[ballaratdragons]

My next door neighbour (retired physics/science professor) has designed a simple EQ mount with tracking for my 12" Dobbie! The chap across the road is an Engineer!! Looks like I might be stepping up in the near future.

If all goes well and the set-up works I will share the plans with all of you.

More news as I progress. :work:

[iceman]

I'll be jealous, you know that don't you!? :) So will Anthony (frogman) :)

Can't wait to see how it pans out!

[[1ponders]]

HeeHeeHee, another one into the fold. :evil: :evil: :camera: :astron: Call Tony in a couple of months. He'll probably have a digital camera or two for sale by then.:P

Good luck with it Ken. You won't know yourself if you manage to get tracking on it.

[ving]

sounds great ken :)

show us stuff when you get it hey! :)

[atalas]

Yes Ken, I want a full detailed report on this project! this is very interesting.


Louie :thumbsup:

[Swane]

:bashcomp: G'day Ken will be very interested to see how it works with the view of making one
Derek :einstein:

[asimov]

Yes indeed! I want to see how it's driven!

[acropolite]

Just as I always suspected, inside every dobber there's a wannabee gotoer. Come over to the dark side Ken....:poke:

[mick pinner]

l agree 100% but we do have technology to contend with.

[Starkler]

Not me ! Push-to does fine for me thanks .
I suspect a lot of gotoers miss a lot of interesting objects just outside the field of view of the object they have punched into their keypad, which you could discover just by panning around.

[beren]

To true , hopefully the meade gotoers relize theres a spiral search function , hit the Goto buttton after arriving at the destination again and the scope goes into a slewing pattern surrounding the desired location......looking forward to developments Ken

[ballaratdragons]

UPDATE!

I caught up with my neighbour today.
Now, I know my next door neighbour is an old fella, and a retired Professor but I didn't realise just how old he is (and getting senile unfortunately).

Here is his plan for a home-made GEM with tracking (i saw the drawings),

Are you ready for it??? :thumbsup:

1. To start with you make a simple GEM out of 1.25" Galvanised water pipe and point it towards the Polar alignment, and set it in a block of concrete.

2. Then you get one of those 'modern Record Players' that has 33 1/3 RPM and mount it about 15 feet from the GEM mount. :ashamed:

3. Make a spindle out of wood and attach it to the place where the records turn around. :scared2:

4. Make an arc of metal to attach to the GEM. (there was stacks of Mathematics attached to this part) :einstein:

5. Connect string to the Arc and tie the other end to the spindle via a 1:2 reduction gear. :eyepop:

6. Make sure the string is long enough to track for about 1 hour. :atom:

And there you have it. My next door neighbours Professorship under question!!! Needless to say I won't be taking his plans across the road to the Engineer.

Funny thing is, in theory it will work. Practically, i doubt it.

What a let-down. As you can imagine I didn't know whether to laugh at his joke or cry at his seriousness. I was really looking forward this project. Looks like I will still be Dobbing into the next century.

Bummer, bummer, bummer!!!!!!!!!!!!!!!!!!!!!!!!!!!!! !!!!!!!!!!!!!!!!!! :bashcomp: :bashcomp: :bashcomp: :bashcomp: :bashcomp:

[Orion]

Ken it's some times people like that :einstein: that come up with geat ideas.(you never know)

[RAJAH235]

Sounds very workable, Ken. Why not give it a go? :P :D L.
I've got a bit of butcher's string here somewhere!

[asimov]

:scared2: :eyepop: :bashcomp: :rofl: I'm with you! [dunno weather to laugh or cry] Your in luck though! I just finished playing with a turn-table today actually! I'ts a VERY modern one too....only 26 yrs old! AND it's a 2 speed! Also I got high quality string...none of that cheap twine! :thumbsup: .....

On a more serious note though...that's a BUMMER MAN! Sorry to hear it. I've made 2 EQ mounts now, for 8 & 12.5" OTAs. I could give you some specs. if you want?

Regards...

[Orion]

Yeh, Ken give it a go!!!!!

[ballaratdragons]

I know Ed, but I was expecting something a bit more realistic than this.

He is a very nice, friendly and extremely intelligent man (this is the one who refuses to connect to the electricity supply or register his cars in case the government finds out where he lives).

I really thought he was going to come up with something great. A 'Modern' record player???? I am laughing about it but also feel like I got kicked in the stomach. I have so many mixed emotions.

I don't want to hurt his feelings either, so I will tell him I am thinking about his second option. His 2nd option was buy an old Grandfather clock, pull out the mechanism, remove the spring and replace it with a heavy weight on a rope. This one does work, as we have a scope at our Observatory which has this system and it is brilliant.

I won't be building that one either unless I can find a very big Grandfather clock very, very cheap! But to be even more realistic, It has to drive a 12" reflector!!!

[ballaratdragons]

John (Asimov),

I would appreciate some specs for an EQ to take a 12". (proper ones LOL) The one I made a thousand years ago was only for a 4.25" reflector and it wobbled horribly.

Gee I feel like a goose!

[Orion]

Oh well, at least he was willing to make it for you and like you say he must be a nice guy. By the way with a "modern" record player can you still play the old LP's some where on the mount? :rofl:

[asimov]

Ummm. [seriously] Have a look at my pics of the mount, to see if this is the way your thinking of going. I think I have some in the for-sale section "wanted, 1RPM motor. Come back & tell me what your thought are..

[ballaratdragons]

Ed,

He wasn't going to MAKE it. Just supply the plans. That's when I thought of the engineer across the road.

John, going to have a look now.

[ballaratdragons]

Yes John,

something like in your pics, but I will also have to solve the drive problem too. I might have to fit a Record player LOL.

The simpler the plans the better for me.

[asimov]

As far as the mount goe's, it's relatively simple, I should mention because I'm in...or was in the steel game, I did it all myself, the steel....I got CHEAP!! & naturally I didn't include my labour in the costing. All up It cost $300 odd. The most expensive parts were the bearings on the RA axis & the main pedestal.. If your paying your mate to make it, it's gonna cost a lot more than that! But thats still cheaper than buying something like this new. Even though my mount is BIG....it's not got a lot of mass. In hind-sight, I would have beefed it up a bit more....only for driving purposes though. It works great as a push-to... I'll explain more in the plans that I send you. Better give me about a week & I'll have some specs for you. I can either submit the plans on here or email...your choice.

[ballaratdragons]

Thanks John,
Email would probably save space in here unless others come in and say put them in here for them too.

[asimov]

I'm in process of tracking down a stepper & controller for this particular radial arm set-up, It's just an idea I saw on the internet, & decided to give it a shot....There's plenty of other ways to drive a scope this big. I'll keep you informed.

[asimov]

Yeah....I'll do it as a 'how-to' DIY for anyone that wants to try it.

[ballaratdragons]

Thanks John. :thumbsup:

[mch62]

Don't know if you have seen my project on the forum, or weather it would suit you as it is not done on the cheap.
But mind you it's 1/4 the price of a commercial mount that has any thing near the weight handling capabilities.
This is a no wobble tronic mount.

It's a friction roller drive EQ fork .
Why??
1/ Because friction drives are about the cheapest drive going especially in large scopes and
2/ A fork is better suited to friction drives than a GEM.
3/ No need for GEM meridian flip

This mount will take up to a 20" f4.5 between the forks but a 16" f5 is my goal. At present it will be home for my 12.5" f6.
Drives discs 660mm dia.
RA shaft 90mm dia ect ect
Mel Bartel servo drive system>>>> will drive virtually any mount with mods.
http://www.bbastrodesigns.com

It's not completed yet but makes a wonderful ride when sitting in the fork :rofl: :rofl: :rofl: :rofl:>>>>that's what the ride is like.

And for those that don't like technology and must push a Newtonian (re Dobinson mount ) the Go-To drive controller has that function called push and track .So you can push the scope to where ever ,re engage the clutches and it will start to track from there and not loose synchronisation with where it was.
Mind you max slew is 6 deg /second + so no real need to push.
Also can run in Alt Az mode (re Dobinson mount) with field rotation , for dobby conversions.

More than happy to discuss it or a scaled down version or friction drives.
So far about $2000 spent for the controller and mount fabrication, most probably another $500 will finish it off plus a cheap computer for the programs.
DIY of coarse except for some of the heavy machining.

You can do it a lot cheaper of coarse but I designed mine with the inevitable aperture fever disease in mind.

Mark

[ballaratdragons]

Thanks Mark.

I have been keeping track of your progress with the fork mount. It looks so BIG. But like you said, it is being made to take BIG scopes.

I doubt that I will ever go over 12". I like my scope and it is big enough for me.

Does the fork really need to be that particular shape? Can it be just a U shape made of steel, aluminium or wood. I like the fact that it can be hand guided like a dobbie or techno-whizzed!

[asimov]

Very nice Mark. I've been toying with the idea of totally re-hashing my design & making a fork mount. At this stage though, I have not got the facilities or the tools to attempt it.

[mch62]

Yes you can make the fork what ever shape you desire and with what ever materials but you do have to remember that for it to be solid and not ring like a tuning fork it needs to be made correctly.
The fork part is made from 19mm ply and in fact is basically 2 single pieces with the sides filled in .
All pieces are of triangular shape to maximise stiffness.
The whole lot is then fiber glassed coated and that is not that hard to do , a bit like paper mache`.
The fibre glass really makes it very stiff.
For a 12" only the whole lot could be scaled down to using 12mm ply and about 2/3 the overall size.
I can pick the fork up by my self so it is not a heavy way of going about it.
making it from steel is going to make it a heavy job to do ones self.
The inside is hollow but will be filled with expanding foam to stop the sound box resonance .
You could use steel or aluminum but that is going to increase costs.
The fork is made from only 2 pieces of 19 x2400x1200 ply plus about $ 120 of resin and fiber glass chopped mat.

I have gone about it as basically as possible and as cheap without compromising stability and only have basic tooling like routers ,circular saw, drill and hand tools .
I had to buy some of theses but factored that into the cost advantage over a commercial mount.
The whole thing is not going to cost that much more than a SSEQ6 and i know for a fact that an EQ6 won't handle my scope.

The steel wedge and shafts are away at the moment getting the motors fitted and drive and support rollers made.

At the moment i am in the process of redesigning my secondary cage so it rotates and allows viewing from all angles depending on scope orientation . Again only a router is required and is made from ply rings and aluminum sheet plus a bit of resin splashed here and there.

Any one want a heap of saw dust , routers are great for creating it and I got heaps :D

Mark

[Starkler]

Ken, maybe a "split ring" design ? It would certainly be easier to add a friction drive to.

http://www.focuser.com/atm/spltring/spltring.html

http://home.fuse.net/astronomy/Reflectors.html

[ballaratdragons]

Geoff,

It looks like an interesting project but GS dob bearings are about a third the way up the OTA. These split ring designs are for truss dobs with the bearings at the bottom of the OTA. I can't think of a way to adapt the mount to take a GS.

[mch62]

Do the bearings detatch from the OTA ??
They may be far enough up to miss the inner race of the split ring.

Might be a better choice for a light top ended truss tube??

There a good alternative for friction drive .

I did consider this in my mount but as the conical mirror is lighter than a normal mirror it throws the balance out and hence mine balances about half way.
Better suited to a fork or GEM in my case.

Here are some pics I used in my design search over the years.

Mark

[ballaratdragons]

Mark,

The bearings will unscrew and can be moved anywhere but they are perfectly balanced where they are.

I like the look of the units (fork) in pics 1 & 2.

I also found this drawing for a simple GEM but I don't know how I would make it track!

http://home.fuse.net/astronomy/pipemount.jpg

[cristian abarca]

Hi John

I'm in the process of making a 250 mm telescope and I would be very interested to see how you made yours as I want to make an EQ mount for mine as well

Regards Cristian

[asimov]

Cristian. If you can wait about 2 weeks, I'm in process of doing the plans up & displaying it in this forum.

[mch62]

OK , the thing to remember with the smaller size mount is you will have to most probably use gear and worms and this is going to cost ya big $

This when i looked into it you would have to import them from the US or UK.

To import a 12" worm and wheel set was in the order of $1200-1500 each then you have to add controllers.
A smaller size say 9" gear for a 12"only scope will lessen the price.

This is why I went friction roller drive.
It does not require many $ to get a large steel disc machined.

You don't have to use steel , even ply with a SS band will do and this is what I am using for the DEC disc to cut down weight.

The thing for a friction roller drive to work with minimal slippage is you need the drive disc to be as large as possible .

This also helps in the final over all reductions required.
I have read at least 1.5-2x the size of the scope is normal.

So you would need 450mm drive disc for a 12" scope but will depend on variables.

There are ways of over coming this but then things get more complacated.
There was an article in S&S and S&T a year or so back about a guy who built a GEM using 18" ?? friction discs and a rubber belt traction drive .
This seamed a bit complicated for me.

This is why the split ring design is better suited to a friction drive due to the large ring for the drive to act on.

You can see this is why a friction drive is not really suited to GEM's --a bit hard to fit a large drive disc on a GEM with out it hitting the pier..

A largish fork is also better suited as well.

I was never able to find any one in Australia that makes large acurate low PE worm and wheel gears .

So the choices are narrowed to DIY or pay $12000 for a mount and why I didn't consider a GEM.

Here are some more smaller designs to study.
some made from ply and others from steel or aluminium , but all semi portable.
Also a Dob driver.




Mark

[mch62]

P.S. note the yellow mount how there is only one pillow block bearing for the RA at the bottom.
The drive disc is cradled and rides on a driven roller and a second free running support roller and this acts as the second bearing with the weight of the scope giving the need force to stop slippage.
The fork attaches directly to the drive disc with tension supports to stop the disc from warping.
Mine is based on this but bigger.
Not sure if you need portability but this would be possible.
The whole fork assemble will just lift off and slid out from the bottom bearing.

Mark

[ballaratdragons]

Thanks Mark.

They all seem so complicated and huge. Especially when you can buy a Mount with computerised tracking & GoTo and it is all inside a tiny box!

[cristian abarca]

John I can wait for as long s it takes as I still have about 6 weeks before I get my mirror aluminised. Thanks for sharing your ideas.

Regards Cristian