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Making counterweights

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#1 John Fitzgerald

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Posted 17 March 2019 - 10:08 AM

Who has made their own counterweights?  Purchased CWs are expensive to buy and ship.  How did you go about it? Materials?  How did it work?

 

I recently made one using 4" sch 40 PVC fittings, pipe caps, and 1.25" ID aluminum tubing.  It is filled with lead sinkers and steel BB shot.  injected with "Rock Hard" putty to prevent rattling and lock everything together.  PVC is double walled and tapped where bolt goes through, plus there is a wing nut anchored inside.  It weighs 14.75 pounds and cost me about $40 for everything.  Works very well.  Painted with a primer, then with Rustoleum "hammer finish" paint.  I put a nylon tip on the securing bolt to prevent CW shaft marring.

 

I posted this on "what did you work on today" week before last, but wanted to follow up with a thread of its own.

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Edited by John Fitzgerald, 17 March 2019 - 10:10 AM.

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#2 Mark326

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Posted 17 March 2019 - 10:22 AM

Here is mine, design based on a DIY CW thread found here on CN.  Total cost <$20, works well.  Reconfigurable in 2.5lb increments based on currently mounted equipment.
 
Counter weight project 2
Mount CW project

 


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#3 b.bill.p

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Posted 17 March 2019 - 11:09 AM

I found my Dad’s weight lifting gear and used a couple of the iron weights.  First I cleaned up the center hole, steel brushed the layer of rust off the surface then sprayed it with 5 coats of gray wrinkle finish cabinet paint.  It looks fantastic.  Then I 3D printed some tapered retainer collars to snug the weight up on the balance bar.   Cost, $4.00 for the paint.



#4 mark77

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Posted 17 March 2019 - 12:31 PM

I have made several using round steel  slugs I purchased from ebay and then finishing them in a lathe. Steel is available on ebay in all different diameters and lengths.  Sometimes even with the right hole diameter.



#5 R Botero

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Posted 18 March 2019 - 03:08 AM

I recently made 3 for my AP900GTO mount. Used 316 stainless steel billets. Bored and finished them on the lathe. I epoxied a brass sleeve on the larger one (14lbs) to avoid marring the counterweight shaft (1.875”). Drilled and tapped holes for hex brass tipped screws to mount them on the shaft also. It took me a week to finish these working at night after work. These were my first counterweights. I have made a number of adaptors/couplers on the lathe but never something as large/heavy.
Materials were not cheap but either buying them locally or importing them (I’m in the UK) would have been prohibitively expensive.
Will try and post some pictures later.
Roberto

#6 R Botero

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Posted 18 March 2019 - 03:19 AM

Here they are mounted. The middle one is an original!

 

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#7 Kunama

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Posted 18 March 2019 - 04:18 AM

I made a counterweight today for my secondary mirror ....... 56mm diameter, 600gram brass c/w with 3/8" UNC threaded hole and stainless locknut holding it in place...

(the wide-angle lens makes it look much bigger than it really is)

 

The secondary is a 4" 1/12th wave on a thick substrate and in an Astrosystems holder so it exerts quite a bit of torque below 45º elevations.

Though this torque previously only moved the laser spot a tiny amount, the installation of the counterweight on the other end of the threaded rod has nulled that movement.

 

(The counterweight is also needed as I have decided against the installation of an optical finderscope for which I made a 500gram allowance in the build)

 

(NB. The final coat of flat black is yet to be applied ! )

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Edited by Kunama, 18 March 2019 - 04:21 AM.

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#8 Kunama

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Posted 18 March 2019 - 05:14 AM

I recently made 3 for my AP900GTO mount. Used 316 stainless steel billets. Bored and finished them on the lathe. I epoxied a brass sleeve on the larger one (14lbs) to avoid marring the counterweight shaft (1.875”). Drilled and tapped holes for hex brass tipped screws to mount them on the shaft also. It took me a week to finish these working at night after work. These were my first counterweights. I have made a number of adaptors/couplers on the lathe but never something as large/heavy.
Materials were not cheap but either buying them locally or importing them (I’m in the UK) would have been prohibitively expensive.
Will try and post some pictures later.
Roberto

Great work Rob, I think my lathe would start to cry if I locked a 304 or 316 billet into its chuck bawling.gif bawling.gif bawling.gif


Edited by Kunama, 18 March 2019 - 05:15 AM.


#9 R Botero

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Posted 18 March 2019 - 05:45 AM

Great work Rob, I think my lathe would start to cry if I locked a 304 or 316 billet into its chuck bawling.gif bawling.gif bawling.gif

LOL...not the lathe crying but me after the third one was made! Boring them was not that difficult but threading the holes for the locking screws was the most difficult bit as I had to hold the counterweights perpendicularly to their main axis in the (4-jaw) chuck ...since I don’t have a milling machine!!!

Roberto

Edited by R Botero, 18 March 2019 - 05:46 AM.

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#10 PrestonE

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Posted 18 March 2019 - 08:48 AM

John, another option is casting a lead weight with a steel or SS insert for the shaft to ride upon..I have been casting lead in my Kinetic Sculptures as it

is about 1.3 times heavier than steel and I need the higher density for balance...limited amount of space.

 

It is easy to melt and cast...just be sure to wear an Inorgainc Chemical filter on your mask and have a fan blowing any fumes

away when pouring the lead...

 

But, the weights come out wonderful...and you do not have to deal with expensive SS that needs to be machined...

 

Just a thought.

 

Best Regards,

 

Preston



#11 John Fitzgerald

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Posted 18 March 2019 - 01:05 PM

I've cast about a 6 pound lead weight before.   I melted it outside on a 1500 watt hot plate and cast iron lead pot. Tapped it for the bolt, then coated it with smooth gray epoxy. 

 

I think making PVC pipe enclosed lead weights using shot or sinkers is easier.   Cut the holes with a hole saw, put in the sleeve and bolt with a wingnut, then fill with lead buckshot/sinkers and pour in a little soupy glue or plaster to lock it together, cap off, wait, and done except for paint, if wanted.  With black ABS sewer fittings, painting probably wouldn't be necessary.




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