Home made EQ with tracking for big reflectors

[ballaratdragons (Ken)]

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 (Ken)]

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 (John)]

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 (Ken)]

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

[asimov (John)]

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 (John)]

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

[ballaratdragons (Ken)]

Thanks John.

[mch62 (Mark)]

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 >>>>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 (Ken)]

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 (John)]

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 (Mark)]

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

Mark

[Starkler (Geoff)]

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 (Ken)]

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 (Mark)]

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 (Ken)]

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 (John)]

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

[mch62 (Mark)]

Originally Posted by 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

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 (Mark)]

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 (Ken)]

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!