Counter Weight Extension bar (and related maths!)

[daz]

I want (need) to extend my counter weight bar a bit, cos I think when I get the newt, canon 350 and other gubbins on it, I won't be able to balance properly.

Now, I *think* I understand that I can reduce the weight, but move it further away from the centre of gravity, then it will balance and will actually reduce the strain on the motors (because it's all balance correctly with reduced counter weight).

Could someone confirm my thoughts / creaking memory?

If this is correct, I remember seeing a website that showed how to calculate the weights and distances involved. Does anyone else remember this site, if so, where might it be?? :?

Finally (one for Arthur) - could Ambermile make such an extension bar??

Cheers

[GazOC]

I posted a link for Ant about 9 months ago....

[GazOC]

http://www.robincasady.com/Astro/WeightCalc.html

[daz]

That is the very one!

Cheers Gaz

[GazOC]

Looks like he's saying more weight closer in is the way to go.

[daz]

Indeed. But I know I've read the opposite somewhere ..... hmmm!

[Kaptain Klevtsov]

If you do fast slewing, you want the heavy close in type, if you want stability you want a lighter mass further out. It's called polar inertia and can best be described by an analogy.

If you have a ladder and a big box that weights the same as the ladder, you can begin and end the turning of the box more easily than you can with the ladder.

Big weight close in:-

Pros - low polar moment = easier on the motors etc. for goto slewing

easier to walk round without knocking it

Cons - more weight involved = more total load on the bearings

heavier to move about

more wobbly because of low polar moment

Smaller weight further out is just the opposite of the above.

Captain Chaos

[daz]

Excellent stuff CC.

Appears you were right Gaz - more weight furthe in.

Righto