Boom construction
 

I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so the
first hole is in perfect alignment with the last hole .. take for
example a 20 foot pipe , or tubing . If we had a 20 foot layout table
fine , clamp pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot layout
table . Maybe I am being to critical

Boom construction
 

JB MacDonald wrote:
I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so the
first hole is in perfect alignment with the last hole .. take for
example a 20 foot pipe , or tubing . If we had a 20 foot layout table
fine , clamp pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot layout
table . Maybe I am being to critical

Two methods I have use:

1) "Chalk line", available at any hardware store. Stretch line tight
down the center of the top of the boom (as viewed from above) snap!

2) Lay a 20 ft board, which is 1/2 dia of boom, next to boom and scribe
line down the top of the board on the boom.

I am sure there are other ways ...

JS

Boom construction
 

JB MacDonald wrote:
I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so the
first hole is in perfect alignment with the last hole .. take for
example a 20 foot pipe , or tubing . If we had a 20 foot layout table
fine , clamp pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot
layout table . Maybe I am being to critical

Forget the scribed line - what you really need is for all the holes
through the boom to be parallel. A spirit level clamped at 90deg to the
boom will achieve that.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Boom construction
 

snip


Forget the scribed line - snip.




--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)http://www.ifwtech.co.uk/g3sek




What is so aweful about a scribed line that leads you give an
instruction to' forget it' ?
I've never seen a 'spirit level' being used in a tool room for
accuracy nor could I specify from what you said as to why it should be
used from now on instead of conventional means.

Boom construction
 

On 18 Apr 2007 14:17:27 -0700, art wrote:

I've never seen a 'spirit level' being used in a tool room for
accuracy nor could I specify from what you said as to why it should be
used from now on instead of conventional means.

Well, I guess you haven't had much experience in the tool room.
Otherwise you would have been aware of how precession levels used to
set up machinery. They are used often. How do you think those long bed
lathes are adjusted so they are straight, level and parallel? Yes, my
poor misinformed person they use precession levels.

Danny, K6MHE

Boom construction
 

"JB MacDonald" wrote in message
. ..
I know how to find the center of a pipe, using a vee block, but my question
is how do you scribe a line from one end to the other , so the first hole
is in perfect alignment with the last hole .. take for example a 20 foot
pipe , or tubing . If we had a 20 foot layout table fine , clamp pipe down
and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot layout
table . Maybe I am being to critical

Use a Loooong v block, a piece of angle or channel iron/aluminum.

Boom construction
 

JB MacDonald wrote:

I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so the
first hole is in perfect alignment with the last hole .. take for
example a 20 foot pipe , or tubing . If we had a 20 foot layout table
fine , clamp pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot layout
table . Maybe I am being to critical

Assuming you have a drill press or drill guide that allows vertical
drilling, and assuming that you have at least a few feet of table, there
is a solution, for VHF and up anyway.

Take a small piece of plate or board and mount a rod the same diameter
as the holes you are drilling vertically from it. The accuracy here is
going to set your ultimate result. If you are off 1 degree and use the
device as a reference 10 times during the drilling, you will have a 10
degree twist, although there is a simple way to reduce that error.

Drill your first hole. Now use the device and the new hole to hold the
boom in place and slide along your table to position your drill at the
next hole. Move the device to the latest hole drilled as you run out of
table. To reduce errors from imperfect vertical on the device, rotate
it 180 degrees between each move.

I have used this method to drill 39 element holes for a 31 foot 432 beam
with almost perfect results on an 8 foot table and just a drill guide,
not a drill press. It can be used across boom diameter boundaries,
which it was in this case, with a bit of care.

tom
K0TAR

Boom construction
 

On Apr 18, 2:17 pm, art wrote:
snip

Forget the scribed line - snip.

--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)http://www.ifwtech.co.uk/g3sek

What is so aweful about a scribed line that leads you give an
instruction to' forget it' ?
I've never seen a 'spirit level' being used in a tool room for
accuracy nor could I specify from what you said as to why it should be
used from now on instead of conventional means.

That's funny. My dad was a machinist before me and I still have one
of these in the tool chest he left me. (In the original box no less)

http://catalog.starrett.com/catalog/...sp?GroupID=487

Boom construction
 

On 18 Apr, 17:09, Danny Richardson wrote:
On 18 Apr 2007 14:17:27 -0700, art wrote:

I've never seen a 'spirit level' being used in a tool room for
accuracy nor could I specify from what you said as to why it should be
used from now on instead of conventional means.

Well, I guess you haven't had much experience in the tool room.
Otherwise you would have been aware of how precession levels used to
set up machinery. They are used often. How do you think those long bed
lathes are adjusted so they are straight, level and parallel? Yes, my
poor misinformed person they use precession levels.

Danny, K6MHE

Danny,
don't be silly, you obviously have not spent a lot of time in a tool
room.
A tool room machine is not in any way used as a reference level. What
is used as a reference level is the machine slide with reference to
the cutting plane. An installation of a machine is subject to settling
but it does not affect the accuracy of the product.
Use of a spirit level over the use of a straight piece of angle as a
reference plane is rather stupid and impracticable.

Boom construction
 

"Jimmie D" wrote in message
...

"JB MacDonald" wrote in message
. ..
I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so the
first hole is in perfect alignment with the last hole .. take for example
a 20 foot pipe , or tubing . If we had a 20 foot layout table fine , clamp
pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot layout
table . Maybe I am being to critical

Use a Loooong v block, a piece of angle or channel iron/aluminum.

OR use a couple of short one with a drill press. The last time I did this I
used a v bolck to dril a hole through the end of the boom the placed a 3 ft
piece of all thread through the boom and hung a 20lb weight on the other
end of the all thread. Gravity will now keep things in a straight line.

Boom construction
 

On 18 Apr, 19:27, Wes wrote:
On Apr 18, 2:17 pm, art wrote:

snip

Forget the scribed line - snip.

--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)http://www.ifwtech.co.uk/g3sek

What is so aweful about a scribed line that leads you give an
instruction to' forget it' ?
I've never seen a 'spirit level' being used in a tool room for
accuracy nor could I specify from what you said as to why it should be
used from now on instead of conventional means.

That's funny. My dad was a machinist before me and I still have one
of these in the tool chest he left me. (In the original box no less)

http://catalog.starrett.com/catalog/...sp?GroupID=487

It got me wondering about the advisability of buying stuff from the
west coast where the tool room machines are tested every day for
settlement for an final accuracy of plus or minus ten.
By the time they finish that review the day will be over only to start
all over again the next day.Can you imagine using a spirit level to
check for accuracy after milling a surface?
Art

Boom construction
 

"JB MacDonald" wrote in message
. ..
I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so the
first hole is in perfect alignment with the last hole .. take for
example a 20 foot pipe , or tubing . If we had a 20 foot layout table
fine , clamp pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot layout
table . Maybe I am being to critical

Take two pipes and tape them together. Run a fat marker down the groove
between them.

Use the second pipe to make another antenna and give it to me.

73
Your pal, Sal

Boom construction
 

Ian White GM3SEK wrote in
:

Forget the scribed line - what you really need is for all the holes
through the boom to be parallel. A spirit level clamped at 90deg to the
boom will achieve that.

I have tried that, and it works fine... so long as the drill stand is
fixed.

The other thing that I use that works well is a rod which I clamp to the
round stock (it is actually part of a device for hanging camping lamps
from a tent pole) and I visually line the rod up with the drill while
adjusting the angle and tightening the vice in a drill stand. The
advantage of this is that I can see the rod at the end of even 6 metres
of boom from the drill, whereas I cant see a level at great distance and
need to walk back and forwards making small adjustments.

Another variation is to drill the first hole exactly the size of some rod
(I use some 1/8" brass or stainless which I usually have on hand), fit a
short length of rod and tape it in place, then proceed as above. Then, if
necessary, drill the first hole out to the final size.

We don't usually drill the holes for an interference fit, but rather a
small clearance, so you should expect to need to align the elements after
assembly.

Owen

Boom construction
 

On Wed, 18 Apr 2007 14:20:21 -0400, JB MacDonald
wrote:

I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so the
first hole is in perfect alignment with the last hole .. take for
example a 20 foot pipe , or tubing . If we had a 20 foot layout table
fine , clamp pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot layout
table . Maybe I am being to critical

I responded to this in email, but here it is for the group.

If you are using a vee block, you can place a level on the vee block
and hold it level on top of one end of the pipe. Then move to the
other end and do the same thing. Assuming you haven't moved the pipe,
you should get the holes aligned.

I just recognized you are drilling holes for elements. the above idea
or the chalkline should do you well.

Another idea would be, if you are using a drill press or a drill with
a level on it....

create your vee block to lay the pipe in to drill it. Drill the first
hole and at one end support, use a dowel or peg to hold the pipe hole
vertical. As you move the pipe along, the end support will keep the
pipe in the same position so the drill press matches all the holes.

Good luck. Let us know what method you use.

Buck
N4PGW



--
73 for now
Buck, N4PGW
www.lumpuckeroo.com

Boom construction
 

art wrote:
snip


Forget the scribed line - snip.

73 from Ian GM3SEK 'In Practice' columnist for RadCom
(RSGB)http://www.ifwtech.co.uk/g3sek


What is so aweful about a scribed line that leads you give an
instruction to' forget it' ?
I've never seen a 'spirit level' being used in a tool room for
accuracy nor could I specify from what you said as to why it should be
used from now on instead of conventional means.


You expect a reply to that? "Forget" it!


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Boom construction
 

On 19 Apr, 05:37, Ian White GM3SEK wrote:
art wrote:
snip

Forget the scribed line - snip.

73 from Ian GM3SEK 'In Practice' columnist for RadCom
(RSGB)http://www.ifwtech.co.uk/g3sek

What is so aweful about a scribed line that leads you give an
instruction to' forget it' ?
I've never seen a 'spirit level' being used in a tool room for
accuracy nor could I specify from what you said as to why it should be
used from now on instead of conventional means.

You expect a reply to that? "Forget" it!

--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)http://www.ifwtech.co.uk/g3sek

Ian I remember now from the old days. Engineers came in to the tool
room with a slide rule in their hands and the shop inspector had a
spirit level. I must have had a senior moment
Ofcourse they may even have had a plumb line int their pockets for the
bigger jobs.

Boom construction
 

On 18 Apr 2007 19:30:01 -0700, art wrote:

On 18 Apr, 17:09, Danny Richardson wrote:
On 18 Apr 2007 14:17:27 -0700, art wrote:

I've never seen a 'spirit level' being used in a tool room for
accuracy nor could I specify from what you said as to why it should be
used from now on instead of conventional means.

Well, I guess you haven't had much experience in the tool room.
Otherwise you would have been aware of how precession levels used to
set up machinery. They are used often. How do you think those long bed
lathes are adjusted so they are straight, level and parallel? Yes, my
poor misinformed person they use precession levels.

Danny, K6MHE

Danny,
don't be silly, you obviously have not spent a lot of time in a tool
room.

Only forty years plus. In that time I've moved and/or installed many
lathes, mills, planners, surface plates and etc... Each time using a
precession level. Just as I had been taught by a master millwright
back in my apprentice days.

A tool room machine is not in any way used as a reference level. What
is used as a reference level is the machine slide with reference to
the cutting plane. An installation of a machine is subject to settling
but it does not affect the accuracy of the product.

Yea sure a twisted lathe bed does accurate work....BS

I see your knowledge of shop practices is exceeded only by your
knowledge of antenna theory.

Danny, K6MHE

Boom construction
 

"art" wrote in message
oups.com...
On 18 Apr, 17:09, Danny Richardson wrote:
On 18 Apr 2007 14:17:27 -0700, art wrote:

I've never seen a 'spirit level' being used in a tool room for
accuracy nor could I specify from what you said as to why it should be
used from now on instead of conventional means.

Well, I guess you haven't had much experience in the tool room.
Otherwise you would have been aware of how precession levels used to
set up machinery. They are used often. How do you think those long bed
lathes are adjusted so they are straight, level and parallel? Yes, my
poor misinformed person they use precession levels.

Danny, K6MHE

Danny,
don't be silly, you obviously have not spent a lot of time in a tool
room.
A tool room machine is not in any way used as a reference level. What
is used as a reference level is the machine slide with reference to
the cutting plane. An installation of a machine is subject to settling
but it does not affect the accuracy of the product.
Use of a spirit level over the use of a straight piece of angle as a
reference plane is rather stupid and impracticable.


What a pompous jerk. You have finally stooped so low to try to make your
ownself sound intelligent as to insult others.

Boom construction
 

On Wed, 18 Apr 2007 22:26:02 -0700, "Sal M. Onella"
wrote:


"JB MacDonald" wrote in message
...
I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so the
first hole is in perfect alignment with the last hole .. take for
example a 20 foot pipe , or tubing . If we had a 20 foot layout table
fine , clamp pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot layout
table . Maybe I am being to critical

Take two pipes and tape them together. Run a fat marker down the groove
between them.

Use the second pipe to make another antenna and give it to me.

73
Your pal, Sal

The best answer yet! No special tools involved...
The problem encountered using a level is that you first have to learn
to use a level.

I used to work on a high speed laser printer that was on the 33rd.
floor of a building. Some of the adjustments required the use of a
machinists level. Usually the bubble would wander around a bit. On a
windy day it was down right eerie...

John Ferrell W8CCW
"Life is easier if you learn to
plow around the stumps"

Boom construction
 

On 19 Apr, 10:58, "Jimmie D" wrote:
"art" wrote in message

oups.com...





On 18 Apr, 17:09, Danny Richardson wrote:
On 18 Apr 2007 14:17:27 -0700, art wrote:

I've never seen a 'spirit level' being used in a tool room for
accuracy nor could I specify from what you said as to why it should be
used from now on instead of conventional means.

Well, I guess you haven't had much experience in the tool room.
Otherwise you would have been aware of how precession levels used to
set up machinery. They are used often. How do you think those long bed
lathes are adjusted so they are straight, level and parallel? Yes, my
poor misinformed person they use precession levels.

Danny, K6MHE

Danny,
don't be silly, you obviously have not spent a lot of time in a tool
room.
A tool room machine is not in any way used as a reference level. What
is used as a reference level is the machine slide with reference to
the cutting plane. An installation of a machine is subject to settling
but it does not affect the accuracy of the product.
Use of a spirit level over the use of a straight piece of angle as a
reference plane is rather stupid and impracticable.

What a pompous jerk. You have finally stooped so low to try to make your
ownself sound intelligent as to insult others.- Hide quoted text -

- Show quoted text -

No, he insulted every body elses intelligence.Actually your idea
regarding the piece of angle
as a reference guide for the scribe seemed to be the most practicable.
As yet I have not found the tolerance range for a spirit level whether
it be angular or otherwise. As for insults to ones intelligence I get
them all the time from idiots who do not have the knoweledge to even
understand the subject let alone give proof of errors stated that they
are trying to challenge.
Look around you Jimmy, here we are in the company of antenna experts,
lots of them. Simple questions are posed by newbies and each expert
writes something different such that an answer is never arrived at.
There is not one expert here that can give a single response that can
satisfy all posters which really gives meaning to don't just ask one
expert, ask a dozen experts and then punt. I often get comments that
my statements are not clear
but check out some of the threads that have over 100 or 200 responses,
obviously I am not the only one that is not clear in my writings. Just
imagine all the insults floating around on things imaginary or things
that are virtual or even simple things such a SWR and then some body
suggests to a newbie that he throw all his measuring instruments,
scribers, micrometers but keep only ,yes only, the spirit level when
dealing with the building of antennas ! Maybe it is time to give up my
subscription to RADCOM if this is what I have been paying for. Jimmie
you are one of many that hang apon my tail with the pretense of being
an expert and sooner or later you will look back on this thread
wondering how I could have been so dumb to follow the other naysayers
when I see so much use of Gaussian antennas being made. Some asked for
mathematical proof and when they got it from an indepedent source they
are so much in denial that they keep on digging a hole for themselves
but cannot come up with anything that faults the mathematics and thus
resort to silly talk or flowery language that just shows up as a bunch
of weeds. Jimmie give me something of substance we can talk about to
separate us from multi posters who seem to be doing their utmost in
talking about other things other than antennas and opting for
theoretical talk that emboldens those to post likewise in coat tail
fashion.
Art..........See you at Dayton, I'll be on the look out

Boom construction
 

To reduce errors from imperfect vertical on the device, rotate
it 180 degrees between each move.


^ Best advice ^

Boom construction
 

art wrote:
Just imagine all the insults floating around on things imaginary or
things that are virtual or even simple things such a SWR and then some
body suggests to a newbie that he throw all his measuring instruments,
scribers, micrometers but keep only ,yes only, the spirit level when
dealing with the building of antennas !

You took 4 words of mine, stripped off all the context and common-sense,
and then made up your own fantasy about it.

Fortunately everybody else can see that.


--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

Boom construction
 

On 19 Apr, 15:11, Ian White GM3SEK wrote:
art wrote:
Just imagine all the insults floating around on things imaginary or
things that are virtual or even simple things such a SWR and then some
body suggests to a newbie that he throw all his measuring instruments,
scribers, micrometers but keep only ,yes only, the spirit level when
dealing with the building of antennas !

You took 4 words of mine, stripped off all the context and common-sense,
and then made up your own fantasy about it.

Fortunately everybody else can see that.

--

73 from Ian GM3SEK 'In Practice' columnist for RadCom (RSGB)http://www.ifwtech.co.uk/g3sek

They remember!
Throw the scribe away and use a spirit level !
You can always pull the posting if you are now feeling embarrased.
Or you can make light of it and put it in RADCOM as an example of
common practice in ham radio in the U.K. like making it look like it
was really a joke all the time.

Boom construction
 

Ian White GM3SEK wrote:

art wrote:

Just imagine all the insults floating around on things imaginary or
things that are virtual or even simple things such a SWR and then some
body suggests to a newbie that he throw all his measuring instruments,
scribers, micrometers but keep only ,yes only, the spirit level when
dealing with the building of antennas !


You took 4 words of mine, stripped off all the context and common-sense,
and then made up your own fantasy about it.

Fortunately everybody else can see that.



As you know Ian, we are all too familiar with Art's style. His problem
is, he hasn't figured out that he is someone that will always be
ignored. He just keeps it coming. And I just keep laughing.

73
tom
K0TAR

Boom construction
 

On Apr 19, 11:48 am, art wrote:

As yet I have not found the tolerance range for a spirit level whether
it be angular or otherwise.


If you would simply follow the link that I provided earlier, you could
read:

"The 6" through 18" (150-450 mm) main level vials have graduations
that are approximately 80-90 seconds or .005" per foot (0.42 mm per
meter). There are five, six, or seven lines on each side of the
bubble, depending on the base length.


As for insults to ones intelligence I get
them all the time from idiots who do not have the knoweledge to even
understand the subject let alone give proof of errors stated that they
are trying to challenge.

Perhaps it is because you write with such a lack of clarity that no
one can figure out what your points are.


Look around you Jimmy, here we are in the company of antenna experts,
lots of them. Simple questions are posed by newbies and each expert
writes something different such that an answer is never arrived at.

In the case at hand, several people offered different methods of
work. That you fail to agree with them does not make them invalid;
actually now that I think about it, I think the converse is true.

There is not one expert here that can give a single response that can
satisfy all posters ...

Well, as long as you're one who needs to be satisfied, that will never
happen.

Rest of bafflegab snipped as a service to the readership.

Wes N7WS

Boom construction
 

Wes wrote in news:1177032145.364625.286810
@d57g2000hsg.googlegroups.com:

"The 6" through 18" (150-450 mm) main level vials have graduations
that are approximately 80-90 seconds or .005" per foot (0.42 mm per
meter). There are five, six, or seven lines on each side of the
bubble, depending on the base length.

Wes, I agree, that is entirely practical. As far as bubble technology goes,
senstivity easily exceeds that, IIRC the plate bubble sensitivity on
theodolites is commonly around 20" (seconds) per 2mm run. By reversing such
a bubble and splitting the difference, it should be possible to achieve an
error well under 0.1mm/m slope.

Realistically, most bubbles for engineering workshop use would be more
accurate than the drilling process, so they are a quite adequate means of
registering the work.

I have used them with success, but prefer an indicator that I can see
clearly while tightening the vice.

Owen

Boom construction
 

Tnx for the reply The chalk line, securing one end and guessing at the
other , a little off on the other end ( guess)at center of pipe at
best could through line off. 2. Great idea but you have to have a
perfect flat level surface to start with.great idea for small lengths
though. JB

John Smith I wrote:
JB MacDonald wrote:
I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so
the first hole is in perfect alignment with the last hole .. take for
example a 20 foot pipe , or tubing . If we had a 20 foot layout table
fine , clamp pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot
layout table . Maybe I am being to critical

Two methods I have use:

1) "Chalk line", available at any hardware store. Stretch line tight
down the center of the top of the boom (as viewed from above) snap!

2) Lay a 20 ft board, which is 1/2 dia of boom, next to boom and scribe
line down the top of the board on the boom.

I am sure there are other ways ...

JS

Boom construction
 

Great Idea! I Just have to extend my table on the right side, keeping
my perfectly aligned Vee block clamped down . Now it sounds simple . Tnx JB

Tom Ring wrote:
JB MacDonald wrote:

I know how to find the center of a pipe, using a vee block, but my
question is how do you scribe a line from one end to the other , so
the first hole is in perfect alignment with the last hole .. take for
example a 20 foot pipe , or tubing . If we had a 20 foot layout table
fine , clamp pipe down and use a height gauge to scrib a line the length
of the pipe. if you do not have a line you could get a twist(miss
alignment) but what can a person due that does not have a 20 foot
layout table . Maybe I am being to critical

Assuming you have a drill press or drill guide that allows vertical
drilling, and assuming that you have at least a few feet of table, there
is a solution, for VHF and up anyway.

Take a small piece of plate or board and mount a rod the same diameter
as the holes you are drilling vertically from it. The accuracy here is
going to set your ultimate result. If you are off 1 degree and use the
device as a reference 10 times during the drilling, you will have a 10
degree twist, although there is a simple way to reduce that error.

Drill your first hole. Now use the device and the new hole to hold the
boom in place and slide along your table to position your drill at the
next hole. Move the device to the latest hole drilled as you run out of
table. To reduce errors from imperfect vertical on the device, rotate
it 180 degrees between each move.

I have used this method to drill 39 element holes for a 31 foot 432 beam
with almost perfect results on an 8 foot table and just a drill guide,
not a drill press. It can be used across boom diameter boundaries,
which it was in this case, with a bit of care.

tom
K0TAR

Boom construction
 

Tom Ring wrote in
:

....
the next hole. Move the device to the latest hole drilled as you run
out of table. To reduce errors from imperfect vertical on the device,

This violates an important technique of minimising measurement and layout
error, determine a datum such that you can lay everything off from that
datum, and then do just that.

the next hole. Move the device to the latest hole drilled as you run
out of table. To reduce errors from imperfect vertical on the device,
rotate it 180 degrees between each move.

This is a technique to compensate for moving the datum.

I am not saying it won't work, and I can see that you have done it to reduce
the size of accurate table needed to register the device.

Owen

Boom construction
 

Owen Duffy wrote:

Tom Ring wrote in
:

...

the next hole. Move the device to the latest hole drilled as you run
out of table. To reduce errors from imperfect vertical on the device,


This violates an important technique of minimising measurement and layout
error, determine a datum such that you can lay everything off from that
datum, and then do just that.


the next hole. Move the device to the latest hole drilled as you run
out of table. To reduce errors from imperfect vertical on the device,
rotate it 180 degrees between each move.


This is a technique to compensate for moving the datum.

I am not saying it won't work, and I can see that you have done it to reduce
the size of accurate table needed to register the device.

Owen

And yet is does work. For 39 holes in my case.

I didn't say it was highly accurate, but that by following what I did,
that it would work well enough for a long boom UHF beam DESPITE that
fact. It's also cheap and easy. Unfortunately, many of us cannot
afford the best, but need still need good results. This is one way.

If I could afford equipment like you describe, I would certainly have it
and use it, but I can't. My guess is that most of the people here are
closer to my end of the spectrum than yours. Yet another unfortunate fact.

73,
tom
K0TAR

Boom construction
 

Owen Duffy wrote:


This is a technique to compensate for moving the datum.

I am not saying it won't work, and I can see that you have done it to reduce
the size of accurate table needed to register the device.

Owen

And the best thing about those holes is that the antenna they resulted
in set the all time gain record for a homebrew 432 yagi at Central
States. :)

tom
K0TAR

Boom construction
 

Tom Ring wrote in
:

If I could afford equipment like you describe, I would certainly have
it and use it, but I can't. My guess is that most of the people here
are closer to my end of the spectrum than yours. Yet another
unfortunate fact.


Tom, I don't understand the reference to expensive equipment, the system I
described of placing a short close fitting rod in the first hole and
visually aligning the rod with the drill for each additional hole is very
low cost and adequately accurant.

Owen

Boom construction
 

Owen Duffy wrote:


Tom, I don't understand the reference to expensive equipment, the system I
described of placing a short close fitting rod in the first hole and
visually aligning the rod with the drill for each additional hole is very
low cost and adequately accurant.

Owen

Owen

I was refering to another of your posts -

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

Wes, I agree, that is entirely practical. As far as bubble technology goes,
senstivity easily exceeds that, IIRC the plate bubble sensitivity on
theodolites is commonly around 20" (seconds) per 2mm run. By reversing such
a bubble and splitting the difference, it should be possible to achieve an
error well under 0.1mm/m slope.

Realistically, most bubbles for engineering workshop use would be more
accurate than the drilling process, so they are a quite adequate means of
registering the work.

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

As has been described and documented in the last few months (not here,
but in science journals), emails, and their equivalent, are sometimes
the most misunderstood things in the history of human communication.
The problem is even worse in a newsgroup, because the threads are huge,
and replies sometimes reference posts not in the current sequence, and
people receive items out of time order and often delayed.

tom
K0TAR