Will this tilt tower design work?

[Scott]

I need a tower that I can put up and down by myself.  I tend to mess with my mills a lot and experiment.  A gin pole will not work well as I would have to lower the tower into the lake. 

I'm thinking of a 20' high stand with a pivot point on top, either a tripod or with 4 legs whichever works better.  The tower is a 50' free standing lattice antenna tower 3' wide at the base.  I haven't even seen the tower but will be picking it up tomorrow, CL freebie.  I would be tempted to add another 10' of height with a 2" pole on top but that might be pushing it. 

My thoughts are to counterbalance the bottom of the tower and crank it up with a winch to a stop on the stand and then bolt it in place.  I will most likely guy wire it also. 

[TomW]

No way that is  sane unless it is extremely overbuilt tower.

several hundred pounds on a 40 foot arm is a lot of stress on the pivot.

I don't get why "no gin pole" because of the lake?

Tom

[Scott]

Here's my site.  With a gin pole I'll have to lower it into the lake.  I can't do it any other way. 

I'm a darn good welder and fabricator and I know I can design and build something strong enough, if the overall idea can work.

[frackers]

Shame its not telescopic - if you take a look at this picture
http://gilks.ath.cx/gallery/v/Wind/DSC02904.JPG.html
it might give you some ideas. This is a 60' 3 section tower on a trailer that tilts over. As its only 20' when down the pivot doesn't need to be too far up and a few garage door springs helps with the counter balance.

Originally this was a 6 section 120' mobile tower and each section gets guys of course. Its raised with two trailer winches - one to get to the vertical, the other to wind up the sections.

It handled 50kg of mill OK at 40'

[SparWeb]

You've come up with the "trebuchet" design, but as the others have pointed out it takes a lot of strength at the pivot.

Alternatives that have to be considered are self supporting truss towers or monopoles that have climbing provisions.  If you've already got a reason not to use them I'm curious to know.

All those options aside, there is a way to tilt down with a vertical gin that stays vertical.  I've seen met towers that do this but scaling up to your WT size may be an even bigger challenge.

[fabricator]

I've seem many pivoting towers like you propose there are several commercial towers built like that, just cant recall the names right now, there were links to one of them here recently, one is built in California I believe.

[Scott]

You've come up with the "trebuchet" design, but as the others have pointed out it takes a lot of strength at the pivot.

Alternatives that have to be considered are self supporting truss towers or monopoles that have climbing provisions.  If you've already got a reason not to use them I'm curious to know.

All those options aside, there is a way to tilt down with a vertical gin that stays vertical.  I've seen met towers that do this but scaling up to your WT size may be an even bigger challenge.

This is what I have now, a 10' high gin pole cemented in the ground (and guyed) and a 30' pole attached to the bottom of it on a hinge.  I have a boat winch that I crank up the 2" pole with.  Works really well and very easy to bring up and down.

I get hit hard with the prevailing winds on the edge of the lake.  30' is tall enough most of the time, but if I could get up another 20' it would open me up to more wind.  Seems the effort for that extra 20' while still being able to crank it up and down myself might be more that it's worth though.  We'll see, I'm picking up the tower tomorrow and my thinking cap will be on for sure.   

[Rover]

Scott, I had a similar problem,

Although only 30 ft, here is my tower. http://fieldlines.com/board/index.php/topic,143204.0.html

[zvizdic]

I use ladder to reach second section of my telescope 30' tower.

I am planing to lover it down in a month and post some pics louvered .

[Scott]

I got the antenna today.  Had to climb up nearly 30' to hook a cable to it to lower it down with a winch.  I'm getting way to old to climb that high on an old rusty freestanding tower.  Then the back window of my truck got broke loading it up.  Then I go to take a ride to my camp to check out that crappy Air 403 and had flat on my car.  Then the Air unit is just sitting there doing nothing in a 20 mph wind.  What a day, time for a beer, or 2 or 3   

[fabricator]

Now your payback is never, broke window, seized up turbine, case of beer (first of many) welcome to the club.

[SparWeb]

I got the antenna today.  Had to climb up nearly 30' to hook a cable to it to lower it down with a winch.  I'm getting way to old to climb that high on an old rusty freestanding tower.  Then the back window of my truck got broke loading it up.  Then I go to take a ride to my camp to check out that crappy Air 403 and had flat on my car.  Then the Air unit is just sitting there doing nothing in a 20 mph wind.  What a day, time for a beer, or 2 or 3   

We've all been there.  Yeah a couple of beers help.  You earned them today.

[zvizdic]

As I promised. 
Lowered machine.
If you lock at a bottom of a yaw bearing I install a vibration insulation which is polyurethane pipe 1/2" wall thickens 9" long.
Hoping to minimize humming noise that is worse in the winter.

[scoraigwind]

No way that is  sane unless it is extremely overbuilt tower.

several hundred pounds on a 40 foot arm is a lot of stress on the pivot.

I don't get why "no gin pole" because of the lake?

Tom

If the tower is not strong enough to take the weight of the turbine then it is probably not strong enough to withstand the wind loading either.  I think the original sketch will work OK, but you will have to deal with a turbine that wants to fall off the tower, and put it together standing on its head, which is not my favourite.

[jacobs]

What you are proposing is very similar to what Aermotor marketed back in the late 1800's. My understanding is their design was a little shaky though.

[Flux]

A friend of mine did one for a small 6ft machine at 50ft, it worked very well and I suspect you could scale it up a bit. Not sure how big a machine I would want to try it on. My friend added ship type rigging on the top tower section to make it rigid enough to hold the turbine weight when horizontal.

The counterbalance for that small machine was about 1/2 a ton but the lower section was only about 10ft rather than 20. Your pivots need to be very strong and again ship type rigging was used to prevent the pivot shaft bending.

When working it is very tame, the thing is self balancing and the only force is the weight on the legs supporting the pivots. Guys are used when up in the usual way.

PLEASE take note of what Scoraigwind said about the machine sliding off the yaw pivot, build it some other way, if it does slide off you will loose the balance condition and end up with a rocket launcher ( we got seriously close to doing it ).

Flux

[kevbo]

... if it does slide off you will loose the balance condition and end up with a rocket launcher ( we got seriously close to doing it ).

Trebuchet: The preferred launch system of Mid evil space programs everywhere!

Actually, the pictures look dang close to what the OP is discribing...might get some construction tips from looking:
http://en.wikipedia.org/wiki/Trebuchet

[jacobs]

See http://gallery.me.com/kenobrock#100070

[vmike]

Here is a link to the text on a Rhon kf-25 fold over tower.  There is a good drawing of the bracing necessary.  This one shows lattice bracing, the version I have has the bracing made from solid steel components.

http://ne1h.com/Rohn25GFoldOverManual.pdf

mike

[Janne]

The basic principle works ok, and is scalable upwards, but the engineering required is tougher than for a "traditional" tilt up tower. I would like to avoid unless necessary.
The machine in the following link is a 10m diameter one, but I don't know how much is the weight of the installed machinery on top. But proves the concept will work on larger designs as well.
http://pics.ww.com/v/Janne/random/tilt_tower.jpg.html