There is a very important point every one seems to be missing. "In a well
designed plow
you do not need to exert much fown force if any!" (I do realize we aren't
aiming for perfection, but a little design time can save much effort later)
Normally the problem is keeping the plow from digging too deep.
Take a look at a *real* plow as is used in farming, or look at one of the
Nitrogen (Amonia) applicators, or for that matter, on of the units the power
company uses to bury gas line and power cable (not the rotary ones)
There are several very important points (no pun intended).
First, the point itself, is deeply curved with a flat bottom. It should
pretty much come to a point at the front. That is a relatively sharp point
with the angle between the flat bottom and the upper being on the order of
about 20 to 30 degrees and then curve up past vertical.
The idea is to have a steep enough angle compined with the attach point that
when the nose touches the ground it *wants* to dig in. You should have to
create some method of limiting the depth. If you don't the design needs a
bit of modification. EXCEPT for very hard and dry clay (or stone) you
should never need to add weight to hold it down, or to get penetration..
Think of attaching a very large fish hook to the hitch so that with the
point touching the surface it is pointing down at an angle. Moving forward
should cause it to dig in. This is the basic starting point for the tool we
want to build.
Basically the proper point angle combined with the correct support point
should create a plow that will WANT to go right out of sight (and beyond the
ability to pull it forward) unless some method is created to prevent it from
doing so. Usually there is a brace that goes from the frame behind the pivot
point to a rear portion of the plow which is used to adjust the angle and
hold it rigid. Also the angle from the hitch is important. The height of
the pull point of the plow (hitch) should be level when the plow depth is
only slightly deeper than the desired depth. Any deeper and the plow will
want to raise. Shallower and it will naturally want to dig deeper. Again,
look at how a field plow point and suspension are designed. Were it not for
the base of the plow (foot next to the moleboard) and the adjustments to the
angle from the support point they would just keep digging deeper until the
tractor could no longer pull it.
When the power company ran the gas line into my shop they used a similar
device. Just a big steel hook with a pipe welded on the back with the
bottom just above the base of the plow and facing rearward.
>Nope, I think Wendell has it right - three-point hitches usually don't have
the ability to impart >down force. The implements do it, usually by sheer
mass or, in the case of plows, by down-
They don't need the mass except to be able to pull the thing unless the
initial insertion is into very hard soil..
>vector forces imparted by the shape of the blade(s). If you have some
accessory implement,
That is the key!
It is also relatively simple IF you have the cutting torch, or better yet...
a Plasma torch of sufficient size to cut the steel point to shape and of
course a very good grinder for shaping and sharpening the point. If need be
you can have a welding shop cut the material for you.
The point, in this case, needs to be as wide or a tad wider than the largest
cable to be buried, so it could be any where from a 1/4 inch to a full inch
thick. There is no real point in going larger as no yard equipment would be
able to pull it. A point made from one inch thick steel plate will be
massive even if not all that large. It also needs to be hardened, or the
first stone will reshape it.
Long point life in this kind of application is probably not going to be a
factor, but longer than the first stone should be a consideration.
Remember too, it takes a lot of power and traction to pull a one inch wide
blade through the soil even if it is only digging 3 inches deep.
If the tractor only has minimal traction the results to the sod can really
ruin your wife's disposition. The idea is to *neatly* bury radials or
coax<:-)) Even a one inch wide plow trace should be invisible, or nearly
so, after no more than a week has passed.
>like a three-point-hitch-mounted backhoe, that's a whole 'nother story...
Even with the backhoe, mass is not often necessary except in very hard soil.
The bucket is rotated to an angle so when it is set on the ground, further
rotation causes the points (followed by the bucket) to dig in. OTOH I've
seen the whole back end of the tractor lifted right off the ground on
occasion <:-)) Then again, it was busting up concrete.
Backing up a bit... The shape of the plow used to bury cable can be drawn as
two half circles which gives the front and rear of the plow similar, or
identical curves. It can be made so the front and rear are identical with
the exception that the front of the plow needs to be sharp at least for the
area that will be in the ground. You weld a pipe or conduit on the back side
so the bottom of the conduit is flush with the bottom surface of the plow.
"Bell" the input opening so it won't scrape the wire or coax jacket.
Thinking back a good many years, building modified version of a single
bottom plow on a small scale and using the "blade" for burying the cable
instead of the actual plow bottom should work quite well. You really
shouldn't need the power to raise and lower it though. <:-))
Good Luck all,
Roger Halstead (K8RI, EN73 & ARRL Life Member)
N833R, World's Oldest Debonair (S# CD-2)
www.rogerhalstead.com
geo - n4ua
> -----Original Message-----
> From: Jim Lux [mailto:jimlux@earthlink.net]
> Sent: Monday, April 12, 2004 2:04 PM
> To: Wendell Wyly - W5FL; N8DCJ@YAHOO.COM; towertalk@contesting.com
> Subject: RE: [TowerTalk] Using riding mower to run radials (2nd Try)
>
>
> At 12:05 PM 4/12/2004 -0500, Wendell Wyly - W5FL wrote:
> >Unfortunately, almost ALL 3 point hitches DO NOT apply any downward
> >pressure - only upward pressure. This is true on nearly all
> tractors.
> >
> >-----
>
> On riding mowers perhaps, but on the run of the mill Ford and Kubota
> tractors I've used, you can exert substantial downforce. You
> need some
> downforce, or how are you going to do plowing and grading
> type operations.
> I've managed to lift the back wheels off the ground with a
> Gannon on the
> hitch.. The three point hitches I've used also have the
> ability to move
> the two top points relative to each other, which can be used to, for
> example, set the blade angle. Soemtimes it's hydraulic,
> sometimes, it's a
> threaded rod/rigid turnbuckle kind of arrangement.
>
> Jim, W6RMK
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers",
> "Wireless Weather Stations", and lot's more. Call Toll Free,
> 1-800-333-9041 with any questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
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and ask for Sherman, W2FLA.
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