At 09:46 AM 7/9/2005, isp@bnjcomp.com wrote:
>Jim,
>
>I can not argue with much at all regarding your statements. Except the
>engineering costs at 20 hours @ $100 per hour would be abotu 45% the cost of
>the tower.
Of the purchase price of your used tower, yes. Not of the total job cost
for installation of a new tower. You're going to pay a fair chunk to dig
that hole (or spend a lot of your own labor, or call in a friend..), a fair
chunk for the concrete to fill the hole, etc. Here in Thousand Oaks, you'd
wind up paying $600 just for the building permit for the antenna (or maybe
less, if you spend a few hundred dollars on an attorney to do battle with
the city for a waiver).
This is the real problem with used or surplus gear. All the ancillary
stuff is priced reasonably in comparison to the new unit. A service manual
for $50 is perfectly reasonable for a brand new $3000 oscilloscope. It
seems extortionate when you're trying to get one for that Tek 465 you got
for $50 at a ham fest.
Over the past couple years there have been several reasonable estimates of
the "total run out cost" to put up a reasonable tower and antenna, and
they're mostly over $10K, if you fairly count the value of labor and
freebies. In that context, $500-1000 for an engineer is pretty reasonable,
if you have something non-standard.
And, unfortunately, it's real tough to scrounge professional engineering
services for free, mostly because it's a service, not a thing, and the
service tends to keep its value. (Nobody selling surplus P.E. services at
ten cents on the dollar at the hamfest, is there?) You can scrounge the
antenna and tower. You can buy guy cables and fittings at ham fests, or
trade other hams for them. You can trade favors with the backhoe
guy. You're going to have a real hard time finding a P.E. willing to put
their license on the line for free (if for no other reason than their
insurance may not cover them). You could probably work out a suitable trade
of services, but it's going to have to be at the going rate. Say you own a
accounting company. You could probably trade accounting services (at your
standard rate) for engineering services (at the P.E.s going rate). But, it
might well be that you'd be better off selling your accounting services to
someone else, and just paying the cash you get for that to the P.E. If
they're a ham, they'll probably cut you a deal on the fee and rate. Makes
it a more arms length transaction, and there's no icky liability issues to
worry about.
>I will probable have a hard time finding a local engineer that understands
>all that is needed for a tower. Being an electrical engineer myself (NOT
>EIT certified) and taking a few structural classes and with todays computer
>programs I really can't understand why it would take anyone 10-20 hours to
>spit out specs.
It shouldn't be too hard to find a civil engineer to do your work. Check
the state registry for ones in your area, and call them up. They'll refer
you to someone who knows this kind of thing, and does the appropriate sized
job. Obviously, you're not going to be hiring Bechtel or Parsons for this.
While grinding out the calculations doesn't take too long, there's a fair
amount of tedious other stuff that has to get done. Checking the specs
against the local codes. Doing the calculations required by your local
jurisdiction. Actually preparing the report in the format required by your
local folks. It all adds up.
You've said you're going to have a bunch of antennas hanging on this tower.
You (or the engineer) will need to figure out all those antennas, what
their wind loading is, does it meet with the manufacturer's specs (or the
recalculated specs if you're not building it box-stock). I could see it
taking an hour just to describe all the antennas and where they will be,
much less do all the required calculations.
You see, you can't just go to the engineer and say. "I need calculations
for a pier pad with the following loads at the following places." They're
going to want more detail, because their license is going to be hanging on
it. If it were in the context of a bigger project under the supervision of
some other engineer, that might work, because they would trust that the guy
doing the other loads calculations had done it right. Likewise if you're
doing a fairly standard installation.. they would trust (but probably
check) the manufacturer's provided loads data.
If you can find someone who does lots of towers and footings, it could well
be a 3-4 hour job. Collect the data, run the calcs, print the standard
report for the area.
> You obviously do this and I don't so your knowledge
>defintly superseeds mine and I bow down to your experience. That being
>said here is my thought of tower analysis?
>
>1. I get a soil boring and have it examined by our local founddation soil
>sample people.
>2. I send that to engineer which plugs in numbers of soil. Takes tower
>structure and plugs that in.
>3. engineer plugs in numbers for piers.
>4. computer spits outs numbers for various wind loads.
>5. If too small wind load engineer "beefs" up piers and goes to step 3.
>
>Now if I took that to someone who has done towers in past they will have
>most of this done and all they really will have to do it change the soil
>numbers. That would cut time drastically. Yes thier experience level will
>proable be double that of the $100/hour engineer but they will solve it in
>just a few hours and cost less.
Pretty much as you described. It's usually better to find someone who's
done it before, and pay them more, than to pay less per hour for someone
who's going to do all the calcs from first principles.
But even for the almost trivial cases, the hours add up pretty quick. It
takes surprisingly long to track down specs for things. Say the engineer
doesn't happen to have the tower mfr docs in front of him, or the concrete
supplier you want to use isn't the one he's worked with in the past. I
have to find the phone number for the company, give them call, ask for the
specs, someone has to send them, he has to wait to get them, etc.
Some (perhaps most) engineers will be happy to let you do the tedious leg
work part, so that you can give them a complete "ready to calculate"
package of data, but you'll need to work with them to find out what they
need. Likewise, every structural engineer I've worked with has had
definite ways they like to build certain things. One likes square tubing,
and knows the data for those and how the design will work out. Another
builds everything with structural pipe. Some like bolted joints, others
like welding. It all depends.
>Again I appreciate your insight and remarks and wish not to take away from
>them from above.
>
>terry
Happy to explain. We all get so used to the engineering costs being buried
in the purchase price and spread over many units, so you don't really
appreciate how much work and tedium goes into it, and how much money a
tower manufacturer has invested in what they DO provide. It's only when
you are buying a one-off that it starts to be a bit surprising.
It's like that old story about the plumber charging $1000 to come in and
tap the boiler with a hammer. $1 for the hammer tap, $999 for knowing
where to tap that particular boiler. But if you had 10,000 boilers, it's
only $1.10 per boiler.
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and ask for Sherman, W2FLA.
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