Re: [ap-gto] Re: 16 ft. Pier Problem


Jun 11, 2002

 


----------------------------

#5062 Jun 11, 2002

Dennis,

Thank you again for your suggestion and very helpful wording of my

pier problem. I have now talked to a very smart mechanical engineer that

works for Jet Propulsion Laboratory. He is now working on the proposed

pier problem. His initial feeling was that I would have too much

movement and oscillations with a 16' length, but that this could be

solved with two cables at right angles to each other exerting tension.

Your note to me got us started off in the right direction, and he is

going to try to get me some actual mathematical results soon. I do feel

good that the problem can be solved with two tension cables.

The techniques and results might also be helpful to anyone else

contemplating a tall permanent pier above their one or two story house.

Thanks Again, Richard Lapides in California







dennis_persyk wrote:

>Hi Richard,

>

>I am not an ME, merely a Physicist. I attempted to calculate the

>deflection of your proposed pier but I am not qualified for that sort

>of work.

>

>It is my intuitive estimate that your proposed pier will be

>unsatisfactory for imaging, and perhaps mildly dissapointing for

>serious visual observing. I feel the deflection and oscillation will

>be noticable I would sincerely urge you to find a local ME or CE-

>perhaps a local college could help - and pose the following questions:

>1) What is the deflection for an end-supported member of length 16

>feet comprising 8-inch schedule 80 pipe? The deflection force is

>applied at the unsupported end and is of the order of a couple of

>pounds. A few tenths -- 0.0001 inch -- are too much for imaging.

>2) What is the frequency of pendulum oscillation for that structure?

>The low-frequency oscillations (less than 200 Hz0 are high amplitude

>and undesirable.

>

>The deflection goes as the inverse cube of the diameter, so one wants

>a large diameter pier.

>

>Please get some professional advice on this -- the experimental

>approach is too risky.

>

>Dennis Persyk

>Hampshire, IL

>

>--- In ap-gto@y..., Richard & Janis Lapides LapidesFamily@e...>

>wrote:

>

>>Monday, June 10, 2002

>>

>>I also don't know if there are any mechanical or design engineers

>>

>out there, but if so, I have dug the hole for my pier at 3.5- 4.0

>ft. by 3.5- 4.0 ft. By 7 feet deep. It is a very big hole!! The

>planned pier will be a 8-5/8" OD steel pipe with 0.5 " wall

>thickness. From the top of the cement to the bottom of the deck will

>be 12 ft. with approx. 4 ft. above the deck for a total height above

>the ground of about 16 ft. with 7 ft. below the ground in concrete

>(about 1/3 of the total length).

>

>> If anyone sees a problem with this design, I would greatly

>>

>appreciate your comments before the cement is poured this next

>Friday...............

>

>> Thanks for your input.

>> Richard Lapides in California

>>

>>

>>

>>chris1011@a... wrote:

>>

>>>I a message dated 6/10/2002 9:24:28 AM Central Daylight Time,

>>>christone@p... writes:

>>>

>>>>I was wondering, in Astronomy Magazine review on the AP900 GTO it

>>>>

>says that this mount can't run to a DC adapter. Is this true?

>

>>>Do you mean run off a wall transformer? If so, please note that

>>>

>wall

>

>>>transformers provide very poorly filtered DC power, and not well

>>>

>regulated

>

>>>either. The voltage can easily dip below 10 volts under load,

>>>

>which can

>

>>>result in motor stalling.

>>>

>>>Roland Christen

>>>

>>

>>

>>[Non-text portions of this message have been removed]

>>

>

>

>To UNSUBSCRIBE, or for general information on the ap-gto list

>see groups.yahoo.com/group/ap-gto

>

>Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/

>

>

>







[Non-text portions of this message have been removed]



----------------------------

#5065 Jun 11, 2002

Richard,



I designed my friends house and observatory with dual

16" square conc. piers, that are 16' high. The piers

are isolated from the ground floor and second floor

slab, and supported on 3' square footings 3' below

grade. In order to reduce the amplitude for given

impact, I interconnected the two piers with a free

floating beam below the second floor slab. Here are

the results from my calculations for my friends piers:



Application of 20 pounds (final force) in .03 seconds,

freq = 9.3hz, Max. Amplitude = 0.00043" with a damping

time of 3 seconds (1/2 Amplitude in 0.5 secs), max.

acceleration=2.3g, using 2% damping which is typ. for

concrete and steel frame construction.



Perhaps this info may aid your friend at JPL.



Tim



--- Richard & Janis Lapides

LapidesFamily@...> wrote: > Dennis,

> Thank you again for your suggestion and very

> helpful wording of my

> pier problem. I have now talked to a very smart

> mechanical engineer that

> works for Jet Propulsion Laboratory. He is now

> working on the proposed

> pier problem. His initial feeling was that I would

> have too much

> movement and oscillations with a 16' length, but

> that this could be

> solved with two cables at right angles to each other

> exerting tension.

> Your note to me got us started off in the right

> direction, and he is

> going to try to get me some actual mathematical

> results soon. I do feel

> good that the problem can be solved with two tension

> cables.

> The techniques and results might also be helpful

> to anyone else

> contemplating a tall permanent pier above their one

> or two story house.

> Thanks Again, Richard Lapides in California

>

>

>

> dennis_persyk wrote:

>

> >Hi Richard,

> >

> >I am not an ME, merely a Physicist. I attempted to

> calculate the

> >deflection of your proposed pier but I am not

> qualified for that sort

> >of work.

> >

> >It is my intuitive estimate that your proposed pier

> will be

> >unsatisfactory for imaging, and perhaps mildly

> dissapointing for

> >serious visual observing. I feel the deflection and

> oscillation will

> >be noticable I would sincerely urge you to find a

> local ME or CE-

> >perhaps a local college could help - and pose the

> following questions:

> >1) What is the deflection for an end-supported

> member of length 16

> >feet comprising 8-inch schedule 80 pipe? The

> deflection force is

> >applied at the unsupported end and is of the order

> of a couple of

> >pounds. A few tenths -- 0.0001 inch -- are too much

> for imaging.

> >2) What is the frequency of pendulum oscillation

> for that structure?

> >The low-frequency oscillations (less than 200 Hz0

> are high amplitude

> >and undesirable.

> >

> >The deflection goes as the inverse cube of the

> diameter, so one wants

> >a large diameter pier.

> >

> >Please get some professional advice on this -- the

> experimental

> >approach is too risky.

> >

> >Dennis Persyk

> >Hampshire, IL

> >

> >--- In ap-gto@y..., Richard & Janis Lapides

> LapidesFamily@e...>

> >wrote:

> >

> >>Monday, June 10, 2002

> >>

> >>I also don't know if there are any mechanical or

> design engineers

> >>

> >out there, but if so, I have dug the hole for my

> pier at 3.5- 4.0

> >ft. by 3.5- 4.0 ft. By 7 feet deep. It is a very

> big hole!! The

> >planned pier will be a 8-5/8" OD steel pipe with

> 0.5 " wall

> >thickness. From the top of the cement to the

> bottom of the deck will

> >be 12 ft. with approx. 4 ft. above the deck for a

> total height above

> >the ground of about 16 ft. with 7 ft. below the

> ground in concrete

> >(about 1/3 of the total length).

> >

> >> If anyone sees a problem with this design, I

> would greatly

> >>

> >appreciate your comments before the cement is

> poured this next

> >Friday...............

> >

> >> Thanks for your input.

> >> Richard Lapides in California

> >>

> >>

> >>

> >>chris1011@a... wrote:

> >>

> >>>I a message dated 6/10/2002 9:24:28 AM Central

> Daylight Time,

> >>>christone@p... writes:

> >>>

> >>>>I was wondering, in Astronomy Magazine review on

> the AP900 GTO it

> >>>>

> >says that this mount can't run to a DC adapter. Is

> this true?

> >

> >>>Do you mean run off a wall transformer? If so,

> please note that

> >>>

> >wall

> >

> >>>transformers provide very poorly filtered DC

> power, and not well

> >>>

> >regulated

> >

> >>>either. The voltage can easily dip below 10 volts

> under load,

> >>>

> >which can

> >

> >>>result in motor stalling.

> >>>

> >>>Roland Christen

> >>>

> >>

> >>

> >>[Non-text portions of this message have been

> removed]

> >>

> >

> >

> >To UNSUBSCRIBE, or for general information on the

> ap-gto list

> >see groups.yahoo.com/group/ap-gto

> >

> >Your use of Yahoo! Groups is subject to

> docs.yahoo.com/info/terms/

> >

> >

> >

>

>

>

> [Non-text portions of this message have been

> removed]

>

>

> To UNSUBSCRIBE, or for general information on the

> ap-gto list

> see groups.yahoo.com/group/ap-gto

>

> Your use of Yahoo! Groups is subject to

> docs.yahoo.com/info/terms/

>

>









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----------------------------

#5066 Jun 11, 2002

Richard:



Have him consider three cables at 120 degree angles. The problem is

vibration, not just deflection. You may also need dashpots (shock

absorbers) to dissipate any vibrational energy. If you're not

careful, you can end up with a singing pier ;-).



--- In ap-gto@y..., Richard & Janis Lapides LapidesFamily@e...>

wrote: > Dennis,

> Thank you again for your suggestion and very helpful wording of

my > pier problem. I have now talked to a very smart mechanical engineer

that > works for Jet Propulsion Laboratory. He is now working on the

proposed > pier problem. His initial feeling was that I would have too much

> movement and oscillations with a 16' length, but that this could be

> solved with two cables at right angles to each other exerting

tension. > Your note to me got us started off in the right direction, and he

is > going to try to get me some actual mathematical results soon. I do

feel > good that the problem can be solved with two tension cables.

> The techniques and results might also be helpful to anyone

else > contemplating a tall permanent pier above their one or two story

house. > Thanks Again, Richard Lapides in California

>

>

>

> dennis_persyk wrote:

>

> >Hi Richard,

> >

> >I am not an ME, merely a Physicist. I attempted to calculate the

> >deflection of your proposed pier but I am not qualified for that

sort > >of work.

> >

> >It is my intuitive estimate that your proposed pier will be

> >unsatisfactory for imaging, and perhaps mildly dissapointing for

> >serious visual observing. I feel the deflection and oscillation

will > >be noticable I would sincerely urge you to find a local ME or CE-

> >perhaps a local college could help - and pose the following

questions: > >1) What is the deflection for an end-supported member of length 16

> >feet comprising 8-inch schedule 80 pipe? The deflection force is

> >applied at the unsupported end and is of the order of a couple of

> >pounds. A few tenths -- 0.0001 inch -- are too much for imaging.

> >2) What is the frequency of pendulum oscillation for that

structure? > >The low-frequency oscillations (less than 200 Hz0 are high

amplitude > >and undesirable.

> >

> >The deflection goes as the inverse cube of the diameter, so one

wants > >a large diameter pier.

> >

> >Please get some professional advice on this -- the experimental

> >approach is too risky.

> >

> >Dennis Persyk

> >Hampshire, IL

> >

> >--- In ap-gto@y..., Richard & Janis Lapides LapidesFamily@e...>

> >wrote:

> >

> >>Monday, June 10, 2002

> >>

> >>I also don't know if there are any mechanical or design engineers

> >>

> >out there, but if so, I have dug the hole for my pier at 3.5-

4.0 > >ft. by 3.5- 4.0 ft. By 7 feet deep. It is a very big hole!!

The > >planned pier will be a 8-5/8" OD steel pipe with 0.5 " wall

> >thickness. From the top of the cement to the bottom of the deck

will > >be 12 ft. with approx. 4 ft. above the deck for a total height

above > >the ground of about 16 ft. with 7 ft. below the ground in

concrete > >(about 1/3 of the total length).

> >

> >> If anyone sees a problem with this design, I would greatly

> >>

> >appreciate your comments before the cement is poured this next

> >Friday...............

> >

> >> Thanks for your input.

> >> Richard Lapides in California

> >>

> >>

> >>

> >>chris1011@a... wrote:

> >>

> >>>I a message dated 6/10/2002 9:24:28 AM Central Daylight Time,

> >>>christone@p... writes:

> >>>

> >>>>I was wondering, in Astronomy Magazine review on the AP900 GTO

it > >>>>

> >says that this mount can't run to a DC adapter. Is this true?

> >

> >>>Do you mean run off a wall transformer? If so, please note that

> >>>

> >wall

> >

> >>>transformers provide very poorly filtered DC power, and not well

> >>>

> >regulated

> >

> >>>either. The voltage can easily dip below 10 volts under load,

> >>>

> >which can

> >

> >>>result in motor stalling.

> >>>

> >>>Roland Christen

> >>>

> >>

> >>

> >>[Non-text portions of this message have been removed]

> >>

> >

> >

> >To UNSUBSCRIBE, or for general information on the ap-gto list

> >see groups.yahoo.com/group/ap-gto

> >

> >Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/ > >

> >

> >

>

>

>

> [Non-text portions of this message have been removed]



----------------------------

#5067 Jun 11, 2002

Have you ruled out the more seemingly simple solution of a ~ 24" sonotube

with rebar and concrete? This would likely offer the most stable and damped

solution for probably the least cost.



Ludwig



-----Original Message-----

From: art_schneiderman [mailto:art@...]

Sent: Tuesday, June 11, 2002 2:54 PM

To: ap-gto@yahoogroups.com

Subject: [ap-gto] Re: 16 ft. Pier Problem





Richard:



Have him consider three cables at 120 degree angles. The problem is

vibration, not just deflection. You may also need dashpots (shock

absorbers) to dissipate any vibrational energy. If you're not

careful, you can end up with a singing pier ;-).



--- In ap-gto@y..., Richard & Janis Lapides LapidesFamily@e...>

wrote: > Dennis,

> Thank you again for your suggestion and very helpful wording of

my > pier problem. I have now talked to a very smart mechanical engineer

that > works for Jet Propulsion Laboratory. He is now working on the

proposed > pier problem. His initial feeling was that I would have too much

> movement and oscillations with a 16' length, but that this could be

> solved with two cables at right angles to each other exerting

tension. > Your note to me got us started off in the right direction, and he

is > going to try to get me some actual mathematical results soon. I do

feel > good that the problem can be solved with two tension cables.

> The techniques and results might also be helpful to anyone

else > contemplating a tall permanent pier above their one or two story

house. > Thanks Again, Richard Lapides in California

>

>

>

> dennis_persyk wrote:

>

> >Hi Richard,

> >

> >I am not an ME, merely a Physicist. I attempted to calculate the

> >deflection of your proposed pier but I am not qualified for that

sort > >of work.

> >

> >It is my intuitive estimate that your proposed pier will be

> >unsatisfactory for imaging, and perhaps mildly dissapointing for

> >serious visual observing. I feel the deflection and oscillation

will > >be noticable I would sincerely urge you to find a local ME or CE-

> >perhaps a local college could help - and pose the following

questions: > >1) What is the deflection for an end-supported member of length 16

> >feet comprising 8-inch schedule 80 pipe? The deflection force is

> >applied at the unsupported end and is of the order of a couple of

> >pounds. A few tenths -- 0.0001 inch -- are too much for imaging.

> >2) What is the frequency of pendulum oscillation for that

structure? > >The low-frequency oscillations (less than 200 Hz0 are high

amplitude > >and undesirable.

> >

> >The deflection goes as the inverse cube of the diameter, so one

wants > >a large diameter pier.

> >

> >Please get some professional advice on this -- the experimental

> >approach is too risky.

> >

> >Dennis Persyk

> >Hampshire, IL

> >

> >--- In ap-gto@y..., Richard & Janis Lapides LapidesFamily@e...>

> >wrote:

> >

> >>Monday, June 10, 2002

> >>

> >>I also don't know if there are any mechanical or design engineers

> >>

> >out there, but if so, I have dug the hole for my pier at 3.5-

4.0 > >ft. by 3.5- 4.0 ft. By 7 feet deep. It is a very big hole!!

The > >planned pier will be a 8-5/8" OD steel pipe with 0.5 " wall

> >thickness. From the top of the cement to the bottom of the deck

will > >be 12 ft. with approx. 4 ft. above the deck for a total height

above > >the ground of about 16 ft. with 7 ft. below the ground in

concrete > >(about 1/3 of the total length).

> >

> >> If anyone sees a problem with this design, I would greatly

> >>

> >appreciate your comments before the cement is poured this next

> >Friday...............

> >

> >> Thanks for your input.

> >> Richard Lapides in California

> >>

> >>

> >>

> >>chris1011@a... wrote:

> >>

> >>>I a message dated 6/10/2002 9:24:28 AM Central Daylight Time,

> >>>christone@p... writes:

> >>>

> >>>>I was wondering, in Astronomy Magazine review on the AP900 GTO

it > >>>>

> >says that this mount can't run to a DC adapter. Is this true?

> >

> >>>Do you mean run off a wall transformer? If so, please note that

> >>>

> >wall

> >

> >>>transformers provide very poorly filtered DC power, and not well

> >>>

> >regulated

> >

> >>>either. The voltage can easily dip below 10 volts under load,

> >>>

> >which can

> >

> >>>result in motor stalling.

> >>>

> >>>Roland Christen

> >>>

> >>

> >>

> >>[Non-text portions of this message have been removed]

> >>

> >

> >

> >To UNSUBSCRIBE, or for general information on the ap-gto list

> >see groups.yahoo.com/group/ap-gto

> >

> >Your use of Yahoo! Groups is subject to

docs.yahoo.com/info/terms/ > >

> >

> >

>

>

>

> [Non-text portions of this message have been removed]





To UNSUBSCRIBE, or for general information on the ap-gto list

see groups.yahoo.com/group/ap-gto



Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/







----------------------------

#5070 Jun 11, 2002

Ludwig,

This was exactly my thought. The damping coeff. of concrete is

much higher than that for steel .But, I would still make provisions for

sreessed cables in case they are needed. You are building what amounts to

one tine of a tuning fork and it needs considerable help to be stable.

Good Luck,

E C Welch.

PS.

Roland does not put stressed rods on his mounts for show.

EC

----- Original Message -----

From: Ludwig Allegra, MD Ludwig@...>

To: ap-gto@yahoogroups.com>

Sent: Tuesday, June 11, 2002 3:02 PM

Subject: RE: [ap-gto] Re: 16 ft. Pier Problem





> Have you ruled out the more seemingly simple solution of a ~ 24"

sonotube

> with rebar and concrete? This would likely offer the most stable and

damped

> solution for probably the least cost.

>

> Ludwig

>

> -----Original Message-----

> From: art_schneiderman [mailto:art@...]

> Sent: Tuesday, June 11, 2002 2:54 PM

> To: ap-gto@yahoogroups.com

> Subject: [ap-gto] Re: 16 ft. Pier Problem

>

>

> Richard:

>

> Have him consider three cables at 120 degree angles. The problem is

> vibration, not just deflection. You may also need dashpots (shock

> absorbers) to dissipate any vibrational energy. If you're not

> careful, you can end up with a singing pier ;-).

>

> --- In ap-gto@y..., Richard & Janis Lapides LapidesFamily@e...>

> wrote:

> > Dennis,

> > Thank you again for your suggestion and very helpful wording of

> my

> > pier problem. I have now talked to a very smart mechanical engineer

> that

> > works for Jet Propulsion Laboratory. He is now working on the

> proposed

> > pier problem. His initial feeling was that I would have too much

> > movement and oscillations with a 16' length, but that this could be

> > solved with two cables at right angles to each other exerting

> tension.

> > Your note to me got us started off in the right direction, and he

> is

> > going to try to get me some actual mathematical results soon. I do

> feel

> > good that the problem can be solved with two tension cables.

> > The techniques and results might also be helpful to anyone

> else

> > contemplating a tall permanent pier above their one or two story

> house.

> > Thanks Again, Richard Lapides in California

> >

> >

> >

> > dennis_persyk wrote:

> >

> > >Hi Richard,

> > >

> > >I am not an ME, merely a Physicist. I attempted to calculate the

> > >deflection of your proposed pier but I am not qualified for that

> sort

> > >of work.

> > >

> > >It is my intuitive estimate that your proposed pier will be

> > >unsatisfactory for imaging, and perhaps mildly dissapointing for

> > >serious visual observing. I feel the deflection and oscillation

> will

> > >be noticable I would sincerely urge you to find a local ME or CE-

> > >perhaps a local college could help - and pose the following

> questions:

> > >1) What is the deflection for an end-supported member of length 16

> > >feet comprising 8-inch schedule 80 pipe? The deflection force is

> > >applied at the unsupported end and is of the order of a couple of

> > >pounds. A few tenths -- 0.0001 inch -- are too much for imaging.

> > >2) What is the frequency of pendulum oscillation for that

> structure?

> > >The low-frequency oscillations (less than 200 Hz0 are high

> amplitude

> > >and undesirable.

> > >

> > >The deflection goes as the inverse cube of the diameter, so one

> wants

> > >a large diameter pier.

> > >

> > >Please get some professional advice on this -- the experimental

> > >approach is too risky.

> > >

> > >Dennis Persyk

> > >Hampshire, IL

> > >

> > >--- In ap-gto@y..., Richard & Janis Lapides LapidesFamily@e...>

> > >wrote:

> > >

> > >>Monday, June 10, 2002

> > >>

> > >>I also don't know if there are any mechanical or design engineers

> > >>

> > >out there, but if so, I have dug the hole for my pier at 3.5-

> 4.0

> > >ft. by 3.5- 4.0 ft. By 7 feet deep. It is a very big hole!!

> The

> > >planned pier will be a 8-5/8" OD steel pipe with 0.5 " wall

> > >thickness. From the top of the cement to the bottom of the deck

> will

> > >be 12 ft. with approx. 4 ft. above the deck for a total height

> above

> > >the ground of about 16 ft. with 7 ft. below the ground in

> concrete

> > >(about 1/3 of the total length).

> > >

> > >> If anyone sees a problem with this design, I would greatly

> > >>

> > >appreciate your comments before the cement is poured this next

> > >Friday...............

> > >

> > >> Thanks for your input.

> > >> Richard Lapides in California

> > >>

> > >>

> > >>

> > >>chris1011@a... wrote:

> > >>

> > >>>I a message dated 6/10/2002 9:24:28 AM Central Daylight Time,

> > >>>christone@p... writes:

> > >>>

> > >>>>I was wondering, in Astronomy Magazine review on the AP900 GTO

> it

> > >>>>

> > >says that this mount can't run to a DC adapter. Is this true?

> > >

> > >>>Do you mean run off a wall transformer? If so, please note that

> > >>>

> > >wall

> > >

> > >>>transformers provide very poorly filtered DC power, and not well

> > >>>

> > >regulated

> > >

> > >>>either. The voltage can easily dip below 10 volts under load,

> > >>>

> > >which can

> > >

> > >>>result in motor stalling.

> > >>>

> > >>>Roland Christen

> > >>>

> > >>

> > >>

> > >>[Non-text portions of this message have been removed]

> > >>

> > >

> > >

> > >To UNSUBSCRIBE, or for general information on the ap-gto list

> > >see groups.yahoo.com/group/ap-gto

> > >

> > >Your use of Yahoo! Groups is subject to

> docs.yahoo.com/info/terms/

> > >

> > >

> > >

> >

> >

> >

> > [Non-text portions of this message have been removed]

>

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gto

>

> Your use of Yahoo! Groups is subject to docs.yahoo.com/info/terms/

>

>

> To UNSUBSCRIBE, or for general information on the ap-gto list

> see groups.yahoo.com/group/ap-gto

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>






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