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Vibration suppression pads damping time

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#1 Redbetter

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Posted 26 May 2018 - 04:31 AM

I did an enlightening test while checking out a new small OTA on a mount during the afternoon.  I was looking at a light fixture with a 5" Mak on a completely inadequate Twilight Nano mount (I didn't buy this for the mount but was curious as to how bad it would be.)  When making focus adjustment at 173x the damping time was 10.5 seconds after release--completely nuts!  So I put the VSP's under the tripod and...3.5 seconds.  I got the same results in both configurations several times.  It was still long, but the mount became usable with the VSP's. 

 

I then put the same OTA on the Twilight I mount as intended, in the recline position.  The damping time was only 1.5 seconds.   Adding the VSP's cut it to about 0.5 seconds--too rapid to adequately measure, but averaged around 1/3 of non VSP.  I had my son try each configuration and he saw the same when refocusing for his eye.   Not bad for a 23 yr old set of VSP's. 

 

 



#2 ascii

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Posted 26 May 2018 - 08:20 AM

Interesting, I've never tried them and always figured that they were mostly a gimmick.


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#3 williew

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Posted 26 May 2018 - 08:40 AM

I have pads, but they didn't seem to help. After reading your post, I tied them again. Yup! about 7 seconds of vibration reduced to less than 2. My pads have 3 bumps on the bottom which replace the single point of tripod leg contact with the ground to three points under each leg. I'm guessing my rough drive way didn't allow the pads to rest up off the ground on those three bumps. On my smooth garage floor, they worked great. 


Edited by williew, 26 May 2018 - 08:45 AM.


#4 Eddgie

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Posted 26 May 2018 - 09:48 AM

Interesting, I've never tried them and always figured that they were mostly a gimmick.

They work.  I used them for years on a variety of mounts up to a C14 on a CGE and they always reduced dampening time and often the result was quite dramatic .


Edited by Eddgie, 26 May 2018 - 09:49 AM.


#5 rolo

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Posted 26 May 2018 - 09:58 AM

I couldn't do any planetary observing on my deck without them.


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#6 Spikey131

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Posted 26 May 2018 - 11:29 AM

I had my doubts until I tried them.  They do work for me.

 

From reading previous threads on this topic, the degree to which they help probably depends upon your setup.



#7 munirocks

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Posted 26 May 2018 - 02:49 PM

Rubber is famous for its damping properties. Would any rubber feet do a similar job, or do the pads use a special mix? I know there are some exotic materials around now, including some that have a negative poisson's ratio. 



#8 clearwaterdave

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Posted 26 May 2018 - 04:17 PM

20170428_090829.jpg

 

20170428_090829.jpg 9I use crutch pads on my onesky and 8" dob..they make it possible for me to view off my deck without any vibration from my heartbeat or movements. I also made some with two layers of 1/2" camping mat foam that work good for my lighter scopes .



#9 williew

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Posted 26 May 2018 - 05:24 PM

Rubber is famous for its damping properties. Would any rubber feet do a similar job, or do the pads use a special mix? I know there are some exotic materials around now, including some that have a negative poisson's ratio. 

My pads are rock hard. No give to them. Not what I expected, but somehow, they work. I'm guessing it has something to do with those three bumps that are on the bottom of each pad. Also, the tops are concave so the tripod legs tend to center themselves in the middle of each pad. 



#10 Jond105

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Posted 26 May 2018 - 05:43 PM

I couldn't do any planetary observing on my deck without them.


They have worked wonders for me when on my deck as well

#11 Eddgie

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Posted 26 May 2018 - 10:20 PM

Rubber is famous for its damping properties. Would any rubber feet do a similar job, or do the pads use a special mix? I know there are some exotic materials around now, including some that have a negative poisson's ratio. 

 

The materiel used is sorbothane.  

 

The design is simple.  The bottom "puck" has a disk shaped void or cast into it about 2" across and about 1" deep.  Inside of this is a sorbothane cup about 1/4th inch thick on the bottom and sides.  A plastic button made of the same material as the puck shaped bottom piece sits inside the sorbothane cup and the tip of the tripod leg sit on this button.   

 

This design means that the button is completely isolated from the bottom and all sides of the puck. 

 

The dampening of the sorbothan is quite remarkable and it takes compression well.  Even under the 170 lb. load of the C14 and CGE mount, the materiel does not squeeze up at the sides.

 

There are some DYI designs out there and I have tried three of them.  None have come close to having the effectiveness of the factory made types. 

 

That does not mean that someone inclined to do so would have the same outcome, but I just did not think the DYI ones I made worked all that great.

 

If one decided to do it, I would avoid the Neoprene and other materials people have suggested, and just buy sheets of sorbothane.   

 

https://www.ebay.com...9EAAOSwDlxU3TYd


Edited by Eddgie, 26 May 2018 - 10:22 PM.

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#12 Karl Fabian

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Posted 26 May 2018 - 11:01 PM

I have pads and while they seem to work on hard surfaces like a deck or cement, a grass-sod soft soil surface provides not only better local seeing but acts as an effective vibration dampener ...especially with a tripod with spiked-pointed tips. The pads are not useful on the grass in my experience, and cement, asphalt  is not the ideal location due to heat radiation occurring for hours after sundown especially during the warm summer. 



#13 Redbetter

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Posted 27 May 2018 - 02:49 AM

I have pads and while they seem to work on hard surfaces like a deck or cement, a grass-sod soft soil surface provides not only better local seeing but acts as an effective vibration dampener ...especially with a tripod with spiked-pointed tips. The pads are not useful on the grass in my experience, and cement, asphalt  is not the ideal location due to heat radiation occurring for hours after sundown especially during the warm summer. 

About the pointy spiked tips...those defeat the vibration damping offered by grass as they will transmit to the less pliable ground.  So perhaps the soil is soft enough that it is serving as an effective damper, but it is unlikely to be as effective as VSP's, they are better material for the job.

 

As I have said about VSP's in other discussions:  I have used them for 23 years on all types of surfaces, and they just work.  They work well enough in the grass in the backyards I have had that I rarely set up without them, and most often end up going inside after them when I do.  This has been true in harder soil and on loamier soil. 

 

Case in point...tonight I set up the SCT late in the grass after already having set up a small Mak and a refractor, both with pads.  In the SCT without the VSP's the amplitude and time to settle after vibration were annoying.  There was a breeze too, and that wasn't helping.  Damping time after releasing the focuser knob was 3+ seconds.  So I took the VSP's out from under the better mounted refractor and put them under the SCT.  Big improvement, damping time was a little over 1.5 seconds.  Breeze no longer mattered.    

 

My guess is that most who don't find them useful are already using a mount more than adequate for the conditions and load.   If damping time is a second or less I really don't need them.  I would rather have a lighter, less expensive, and more portable mount and use VSP's. 



#14 Karl Fabian

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Posted 27 May 2018 - 10:11 AM

Your points are well taken. The mounts I am using are stable enough that the difference with or without the pads is not enough to notice  especially on the grass. On a wooden deck it would of course be an entirely different story.



#15 Paul G

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Posted 27 May 2018 - 12:31 PM

The materiel used is sorbothane.  

 

 

This. Rubber can make vibrations worse.



#16 Jeff Lee

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Posted 27 May 2018 - 12:46 PM

Only use mine when not on dirt. They make a world of difference with my SLT on concrete or the deck.



#17 Mitrovarr

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Posted 27 May 2018 - 02:22 PM

I like VSPs. I think the amount of improvement you get varies based on the surface type and the inadequacy of the mount, but it's always an improvement. I do think the improvement gets smaller the larger the scope/mount gets, though.



#18 Eddgie

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Posted 27 May 2018 - 03:15 PM

This. Rubber can make vibrations worse.

Not only does it not have the dampening of sorbothane, but it also has much different compressability characteristics.

 

It is likely that any rubber that was soft enough to have some dampening would just squeeze out the sides of the cup and might not have the necessary dampening characterisics. Any rubber that was hard enough to avoid squish would probably be too stiff to have dampening. 

 

One of the designs I got off of the web used neoprene in a plywood sandwich.  This of course compressed so badly that I would have had to make the pads about 8' across to be able to stand the weight of the C14.   The "store bought" vibration suppression pads lasted 10 years before failure. 

 

I am quite sure that the way business works is that if they could have made it work using a less expensive material like rubber, they would have. My own efforts let a painful path to the recognition that the VSPs one can buy are really about the best you can do. 


Edited by Eddgie, 27 May 2018 - 03:16 PM.


#19 williew

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Posted 28 May 2018 - 06:01 AM

OK. Now I'm looking for a second set of pads. Prices range from 22$ to over 60$. The cheap ones I have now work good. Can't help but think the more expensive ones would work better. Or maybe last longer as Eddgie #18 mentioned.



#20 Paul G

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Posted 28 May 2018 - 11:19 AM

Not only does it not have the dampening of sorbothane, but it also has much different compressability characteristics.

 

It is likely that any rubber that was soft enough to have some dampening would just squeeze out the sides of the cup and might not have the necessary dampening characterisics. Any rubber that was hard enough to avoid squish would probably be too stiff to have dampening.

 

One of the designs I got off of the web used neoprene in a plywood sandwich.  This of course compressed so badly that I would have had to make the pads about 8' across to be able to stand the weight of the C14.   The "store bought" vibration suppression pads lasted 10 years before failure. 

 

I am quite sure that the way business works is that if they could have made it work using a less expensive material like rubber, they would have. My own efforts let a painful path to the recognition that the VSPs one can buy are really about the best you can do. 

The problem with rubber, and anything else other than sorbothane, is its damping coefficient. Rubber firm enough to hold its shape takes the force well but "gives it back" quickly, making vibrations worse. Back when seats in helicopters were mounted on a solid metal frame there were many serious injuries to occupants when the copter came down hard in its normal landing position. My father was an FAA crash investigator at the time. The first thing that was tried (sorbothane didn't exist) was to isolate the chair frame from the copter frame with rubber inserts to absorb the force of impact. The injuries worsened dramatically. The first solution that worked was to have the bottom of the seat frame terminate in metal plugs that fit tightly into metal pipes coming up from the copter frame. These pipes were scored longitudinally so when the seat was forced down the metal plugs would be shoved down the inside of the pipes, causing the pipes to open up at the scores like a banana peel, absorbing the energy without any give back. Injuries dropped to a fraction of what they were with the solid frame. It was a use once, then throw away solution but it did what needed to be done until more elegant designs and materials were developed.

 

People who mistake price for value wind up spending more in the long run. The ~$50 I spent on my Celestron VSP's was money well spent.


Edited by Paul G, 28 May 2018 - 11:21 AM.


#21 howardcano

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Posted 28 May 2018 - 01:11 PM

We used similar stuff, EAR foam, for racing go-kart seat padding.  It made for a smoother ride and improved the handling since it served as a shock absorber ("spring damper" for our European cousins).

 

I've never used these pucks on a tripod, but after reading this thread, I'm curious to try them.  I see the Celestron version.  Are there other brands?



#22 Redbetter

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Posted 28 May 2018 - 07:09 PM

OK. Now I'm looking for a second set of pads. Prices range from 22$ to over 60$. The cheap ones I have now work good. Can't help but think the more expensive ones would work better. Or maybe last longer as Eddgie #18 mentioned.

 

When I picked up the second set of pads last year it was the Astro-tech version from Astronomics.  These appear to be nearly identical to my ancient Celestron VSP's.  I assume that they use the same material and the thicknesses appear to be essentially the same when I remove the central puck.  I have only used the new pads a few times though. 

 

I have not tried to measure relative damping times on the same set up.  Age might have some impact as well.  Do they deteriorate or age like a fine wine. 



#23 williew

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Posted 30 May 2018 - 06:14 AM

When I picked up the second set of pads last year it was the Astro-tech version from Astronomics.  These appear to be nearly identical to my ancient Celestron VSP's.  I assume that they use the same material and the thicknesses appear to be essentially the same when I remove the central puck.  I have only used the new pads a few times though. 

 

I have not tried to measure relative damping times on the same set up.  Age might have some impact as well.  Do they deteriorate or age like a fine wine. 

I guess I'm going to go with the Celestron pads. No way to judge beforehand if they're worth the extra money. Time will tell.



#24 gnowellsct

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Posted 30 May 2018 - 11:20 PM

Wow.  I would never use these on grass.  Asphalt a definite maybe.  I was very interested in VSPs and had some during my CG5 extruded aluminum days.  Once I had a super polaris tripod with wooden legs, I was done with VSPs.  One issue was that on asphalt they tended to slide--just enough that polar alignment could be lost as you swung a scope around, for example.  I can't see why one would want them on grass.

 

Once I went on to G11 HD tripod, Berlebach, and ATS pier I was even more done.    If I observed on asphalt or concrete a lot I might get the Losmandy VSPs but not so much because vibration has been an issue as to give the tripod legs a little protection from the asphalt.  But I stopped worrying about it.  I've used some of this gear for 20 years.  Not too worried if the cosmetics aren't perfect on my HD tripod when I croak.  

 

Greg N



#25 Redbetter

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Posted 31 May 2018 - 02:04 AM

I can't see why one would want them on grass.

 

Because they work on grass.  They work a lot better than the grass does for damping.  Now maybe if you have sorbothane grass (or thick tundra grass--that is like walking on mattresses), but I haven't found grass or the ground beneath it to be particularly effective where I have observed: Southeast, Midwest, East Texas, California or Oregon.   And in Hawaii on the big island there was very little grass.  I was observing in the strongest winds I have ever observed in, with an undermounted 8" SCT, and those little pucks made it possible.  I couldn't walk away from the scope unless I had my wife holding onto the tripod to prevent a gust from blowing the assembly over.   

 

The only time I have had them move that I can recall is when I (or someone else) bumped into the tripod. 




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