Thank you Jase,

Gotchya re. power lines.

I'm sorry I wasnt clear, its the J pipe on its own (only), the longest I would go is the longest J pipe available, 39". The J pipe base is 6x7", fascia is MAYBE max 6" wide - which wont quite do it!

But the series of bolt holes, are 4, 5, & 6" apart (c/c)

I was thinking of building it up from under the fascia (at the soffit) by marrying a 2x4"...but I'm not sure it will be strong enough on a short length (I'm used to doing the carpentry though). First, I need to verify how solid the fascia is.

Its a very light HD4400, going on the end of the J pipe, the antenna's 2 U-clamps are at the bottom of the antenna spine (leaving about 30" between the antenna bottom and the roof surface....

Tower isn't an option here, sorry!

Another, simplest option, is to put a wall stand-off (RCA) bracket on the fascia, and a roof/attic (rotates to correct angle) mount on the lower roof, then put a 10 ft mast pipe from the lower roof to above the upper roof....but I cant persuade him that the roof mount wont cause leaks! since there is no significant pressure on the bottom, I would just lag it to the roof sheating and cover with tar.

here are the 2 units:

http://www.digitalhome.ca/forum/picture.php?albumid=913&pictureid=4915

http://www.digitalhome.ca/forum/picture.php?albumid=913&pictureid=4914

RE: The Tilt Tower Hinge Point.

Re: My earlier posts in this Thread.

My Posts #1647 and #1649 earlier on PG 110 of this Thread.

Here's a picture of what I came up with / what I have constructed so far.

I had some spare time between Christmas and New Years and worked a little more on those Hinge Point parts.

http://www.digitalhome.ca/forum/picture.php?albumid=458&pictureid=5045

Some Details and Measurements:

3x - 4x4 light duty Post Spikes (green paint) - purchased last year, found on sale at a RONA Hardware store for a pretty good price. Only around 6 bucks each. 32" overall length. 3 5/8" square I.D.

3x - Overtubes (Salvaged Scrap - used commercial Fence Top Tube - galvanized)
Each are cut to 24" long. O.D. 1.665" I.D. 1.365" That gives a wall thickness of approx .150". Pretty strong. The tower bottom tubes have to fit inside these with just a little bit of clearance.

5" from one end, 3/8" holes are drilled at proper angles to match the Tower.
(Two are at a 30 degree angle from the hinge holes. The third one, not the hinge point, is at 90 degrees / square to the 7/16" bolt hole below.)

1" from the other end, 7/16" holes are drilled for the "hinge point bolts".

3x - 7/16 x 5" Hinge Bolts & Nuts. Mine are Grade 8 straight steel. But these should be Galvanized or Stainless ... so they don't rust. I may change these.
When tilting the tower, the third one will have to be undone and removed each time. (approx 5/8" were cut off the thread ends, and resulting sharp corners of thread ends then filed / chamfered - they stuck out a little too long)

6x Short pieces of EMT, approx 15/16" long - Electrical Conduit tube as spacers on the hinge bolts - to keep overtubes centered in the post spikes at the hinge points. Cut square as possible and finish filed / deburred nicely.

3x - 3/8 Bolt and nut - to attach base of tower to overtubes. Mine are stainless that I had left over from another project. Should be at least galvanized and at least Grade 8 strength.

The 7/16" holes in the green 4x4 Post Spikes are strategically drilled a little off center in the square so the Over Tubes will hinge with clearance, and placed where they will give good strength.

Some wide slots had to be cut out of one side of TWO of the Post Spikes squares to allow two of the Over Tubes to hinge one way. That was done by hand with a hack saw and the curved cut at the bottom of the slot was done with a very handy and useful blade called a Tungsten Carbide Rod Saw Blade - which fits into a standard hacksaw and allows you to cut curves and some very hard materials in all directions.

I needed to make sure the over tubes would "hinge" just a little more than 90 degrees ...

By the way ... a Drill Press, and a sturdy bench with a vise in the workshop helped immensely to construct these parts. Various files to hand finish and de-burr the parts and get rid of all the sharp edges.

It's been an on-going / evolving design and construction of these parts.


How I will mount the Post Spikes in the ground is a matter yet to be determined.

Two ideas are:

1. Just pound down into the earth, and tie/bolt the square base of the three of them together with some sort of brackets or angle irons, somehow, so they combine their strength grip in the earth. (not sure if this will be safe enough - will have to see / think about that )

or

2. Dig deep hole in earth, pour gravel base in, pack gravel, make triangular form, assemble everything and support the tower base, and the set the bottom of post spikes in a triangular concrete base.
(this method, for sure, should be VERY safe and secure).

Of course ... the tower will be raised a few feet out of the ground after I dig it out (which I have done before). So I will gain a few feet height with this hinge mount thing.

Hopefully this spring or summer ... when I have time, some long weekend, and when the ground thaws out.

We have a brick chimney that is 6.5 ft tall above the roof and in good condition. The prefered mast location on the roof beside the chimney is 12.5 ft AGL.

Using an mclapp M4 w/ large curved reflector (1x2" welded-wire 40"t x 36"w) and a CM9510 rotator: (Pictures: #1-front (http://m4antenna.eastmasonvilleweather.com/pictures/9-5x9%20M4%20front.JPG), #2-bottom (http://m4antenna.eastmasonvilleweather.com/pictures/9-5x9%20M4%20bottom.JPG), #3-front (http://m4antenna.eastmasonvilleweather.com/pictures/9-5x9%202x2%204%20bay%20front.JPG))

I'm considering a 10' mast (3.5' above chimney) and a 5' rotator mast for the 40" tall M4. Total height above chimney = 8.5'. Total height AGL would be 27.5'

1.) Which chimney mount brackets are recommended?

2.) What is the maximum length of mast (diameter & type?) that can extend above our chimney w/o requiring guy wires and successfully withstand severe thunderstorms or ice & wind?

3.) Can a short telescopic pole such as a CM1620, CM1820 (http://www.channelmasterstore.com/TV_Antenna_Mast_p/cm-1820.htm) or Rohn H20 (http://www.rohnnet.com/rohn-telescoping-masts) be used for this application w/o guy wires if the pole is intentionally not fully extended so there is significant overlap?

Thank you

mrvanwinkles: 1. Just pound down into the earth,

If I understand your post correctly, the top of your triangle will face your house and only that leg will be releasable to allow the tower to be lowered away from the house on the other two legs? (Stand on the roof with a rope?)

I have NEVER seen anyone be able to pound one of those Post Spikes into any exact location they wanted them. Close, yes, exact, NO! I highly recommend your option #2 and even then I would also recommend you do a dry fit before you pour any concrete (or even pour concrete with tower in place) because otherwise you will be faced with the problem of trying to get the tower to sit vertically on an immovable base. I doubt you would want to end up having your tower attached to your eave while resting only on one leg at the bottom.

My 2¢ worth, good luck! And thanks for the tip about the Tungsten Carbide Rod Saw Blade, I had forgotten about them.

is it OK to use 2 wall stand-off brackets on a 3 ft high chimney to hold up a 1.25" diam. EMT mast pipe ?

It might be okay, but my question is why not use proper chimney mounts? Which wall mount were you planning on using? Wall mounts are typically long to extend past the eaves, which usually isn't necessary on a chimney.

Thank you Roger,


The chimeny is NOT brick, I'd prefer not to squeeze the cladding with straps. The chimney is 2x2x3ft (height past roof).

Another idea is to attach a pipe down the side of the chimney box (not supported by any roof).

The wall brackets are standard stand-offs, 2.75" out, fastner holes 6.5" apart.

My original idea was to run a 10ft pipe from the lower to the upper roof (red line), but I dont think its high enough to clear the chimney top.

http://www.digitalhome.ca/forum/picture.php?albumid=913&pictureid=5197

In that case, you should be able to use a short (3" or 4") wall mount such as a CM-9025 (http://www.channelmaster.com/TV_Antenna_Wall_Mount_Channel_Master_CM_9025_s/74.htm), CM-9023 (http://www.channelmaster.com/TV_Antenna_Wall_Mount_Channel_Master_CM_9023_s/75.htm) or CM-3079 (http://www.channelmaster.com/TV_Antenna_Wall_Mount_Channel_Master_CM_3079_s/79.htm) (not sure the difference between the last two). Just make sure the lag bolts hit something solid (more than just plywood).

One other thing, I noticed the forum sponsor says the brackets should be at least 20% of the mast length apart. This seems too close together to me. I would think 1/3 (33%) would be a better ratio, but it really depends on the size (wind load) of antenna being installed.

yes, I wanted to use them, but the chimney being about 36" high, puts the brackets at about 30" separation (if I want the pipe resting on the upper roof where the chimney first goes thru the roof), leaving about 90" above the top bracket unsupported

I think the upper bracket force in that case is about 3-4 x the wind force on the antenna !

balm,

Thinking more about it, IMHO, your best bets would be to either go with your original idea and run a mast from the lower to upper roof. I am not sure how far apart they are at the peek of the upper roof, but it looks like you should be able to handle at least a 15 foot mast, which should be long enough to clear the chimney. I would use a swivel mount (such as the CM-3078 (http://www.channelmaster.com/TV_Antenna_Roof_or_Attic_Mount_Channel_Master_CM_3078_s/80.htm)) at the bottom, to attach it to the lower roof and a 3" wall bracket at the peak of the upper roof.

The other idea of running a mast down the side of the chimney box, down to the ground is also a good one. I read somewhere that you can get away with only one mounting bracket (at the top) this way by burying the mast about 1.5 to 2 feet, but I would be tempted to put a bracket every 10 feet (at each joint) plus one at the top of the chimney box to ensure the mast doesn't buckle. I would also make sure the mast is sitting on something solid that won't sink into the ground (a paving stone or cinder block might work well).

I would use a swivel mount (such as the CM-3078) at the bottom, to attach it to the lower roof and a 3" wall bracket at the peak of the upper roof.

yes, this is what im doing, but the chimney including the upper metal pipe is about 5 ft above roof, thus to avoid the chimney blocking the signal, I need to go at least 2 ft above the pipe with bottom of antenna. Add another 3 ft to go to top clamp of CM4228HD. So thats at least 10 ft above the roof.


If I only have about 3-4 ft between roofs, & a 13-14 ft pipe, Im not sure thats strong enough. I calculate 3/14=21% using bracket spacing.

Unfortunately the channels are received in the direcetion with antenna facing that chimney...

Mapmaker, post # 1724

I have NEVER seen anyone be able to pound one of those Post Spikes into any exact location they wanted them.

Yes, you are exactly correct - this is one of my main installation concerns.

I expect to have some "difficulties" with this.

My my "no concrete" idea goes something like this:

I will have to dig a partial hole to get the tower out and up ...
(done that before ... )

I will be left with three alignment holes deeper down in the earth where the buried tower tips were pulled out. I will deepen these a little if necessary as pilot holes - by tapping down some solid steel rod & removing it.

Then I will carefully tap down bottom tips of the Post spikes into those three pilot holes - aligning them best I can.

Should be able to tap the post spikes back and forth sideways (or up and down) a little for adjustment at the top (with a short cut off piece of 4x4 inserted).

They will not be completely pounded in ... not full length of spike ... with this method - and so, should be more easily "adjusted".

Get tower base inserted and assembled - now it's aligned for sure ...same exact position as before.

Back fill hole with earth around post spikes with earth from earlier DIG. Tamp down earth solid. Wet earth a little and tamp down earth solid again all around. It'll settle solid with time.

[ The concrete solution would definitely have all assembled in place and staked solid in perfect position before pouring concrete ]

Important point:
This is a BRACKET tower with a strong BRACKET high up on the peak of a 2 storey house. So base pins support mostly a vertical up and down load / get a large leverage on sideways loads. Should be no problem with three post spikes like that ...

But I would prefer to do this, in this case, without needing a concrete base.
(for a few reasons)

This BRACKET tower should "FLOAT" solid and secure enough in the EARTH alone, with the downward weight of the tower ... I am hoping ... and settle nice and secure in position over time.
[Just like it did before - with just the tower base alone, buried a couple feet.]

Lowering was done last time with a long, strong rope from the ground ... looped through the bracket at the roof peak, and tied to the tower. Undo the U-bolts on the bracket ... feed rope in slowly ...as it tilts down.

I have a strong pulley with bearings assembly ... and am thinking about a steel cable and hand winch / crank maybe.

The tower is planned to tilt away from the side of the house at a shallow bit of an angle.

Call me crazy ... but I think this will work .

balm, If it is only 3-4 feet between roofs then you are probably correct. I would then recommend the other option of running it down the chimney box to the ground.

I did this quick chimney mount for under $10. A piece of 1-1/2 ABS drain pipe, and 2 clamps for chain link fencing. Fastened with 2 TapCon screws to the bricks. Nice :D

Click to view larger image...
http://img223.imagevenue.com/loc717/th_428283998_IMG_0358a_122_717lo.jpg (http://img223.imagevenue.com/img.php?image=428283998_IMG_0358a_122_717lo.jpg) http://img284.imagevenue.com/loc233/th_942828686_IMG_0358b_122_233lo.jpg (http://img284.imagevenue.com/img.php?image=942828686_IMG_0358b_122_233lo.jpg)

Techno_Dweeb, my only concern with bolting to the bricks is the wind force could work the the bricks loose. That is why most chimney kits use straps to wrap around the chimney to distribute the forces across multiple bricks and hold things together. Having said that, your mast is short so the forces should be reasonably small.

Also, PVC pipe isn't the strongest material in the world (I would normally recommend galvanized steel), but once again the mast is short so it should be okay.

Disclaimer: Notice I used the words should in both cases. I haven't done the math to confirm that it is okay so treat my post as a warning of potential failure, not an acceptance of your install.

Thanks for the tips. It is fairly sturdy in the wind. I wouldn't try a tall mast with this arrangement, but I did not need any more height so it worked out great. I get solid signal levels on all channels!
:cool:

It appears to me from the photo that only two bolts hold the installation (one bottom and another at top). If this is the case, I don't recommend such an install.

Eventually wind load and weight from snow and ice on the antenna will work forces on the bolts. This will eventually wear down the brick in the bolt holes, allowing moisture into the brick. And once it freezes, the brick will fail.

You generally want at least 2 bolts per mount to cancel out such forces.

Otherwise, your install looks good and clean.

the antenna will work forces on the bolts
Exactly, when there will be ice on the antenna and wind from behind it, there will be some lever effect.

The antenna and the u-bolt should be centered on that ABS drain pipe or even placed near the bottom bolt.
.

how long a mast pipe can i use in a 3 ft tripod, to hold a CM4228HD, or how high above the top of the tri-pod can the mast be (1.25" dia. EMT mast) ?

thanks

The rule of thumb is 1/3 of the mast must be between the top and bottom mounts, so if the 3 ft of the mast is "inside" the tripod, then that means you can use a 9 ft mast (6ft above tripod). You should be able to round that up to a 10 mast ft without any problems though as it is just a rule of thumb.