home made tugger

[e57]

Glad it worked out, hopefully you made some money and can invest in a factory built tugger. I sure like the Maxis, I have the 3k and a 10K, but I could not figure out how to do a side pull with either one and dug out the old Greenlee. The best investment was the Maxis triggers, very safe to be able to stop the puller for either end of the pull and the will work with any puller.

Jim

And - they have a new safety device - dead man switches on both ends - with communication...

 

[topper]

And - they have a new safety device - dead man switches on both ends - with communication...

That is what the maxis triggers are. They are wireless foot pedals at each end of the pull that both have to be pressed for the tugger to run. Are you talking about something else?

 

[mivey]

The radius of the bend does not change the pulling tension at all.

The radius does change the out (pulling) tension.

A large radius will reduce the sidewall pressure trying to crush the insulation as it is pulled against the side of the sweep.

And that stress causes a higher tension on the out side of the bend.

See also my post here:
http://forums.mikeholt.com/showthread.php?129725-High-Tension-Power-Line-Max-Pull-Angle

 

[macmikeman]

I started my business with a basic plan. Included in that plan was a requirement for a few mandatory items that I would either purchase at startup or not startup at all. One was a top of the line Greenlee tugger set with shives and jackstands. Another was a quality 35 lb jackhammer. Another was a portable threader and jackstand. The big benders came a bit later. I figured back then that I would need to be prepared to tackle big jobs and those items were a definite part of that. Little did I know then that I would eventually end up purposely avoiding the type of jobs where those tools become required..... But anyway they were great investments that paid off many times over and over...

 

[ohmhead]

Homemade tugger

Homemade tugger

Well ive got a few pictures

 

[ohmhead]

Homemade tugger

Homemade tugger

Well

Weve got a few tools over the years home made but today its better to buy it its called insurance people get hurt your in trouble like to see more let me know !

 

[iwire]

The radius does change the out (pulling) tension.

And that stress causes a higher tension on the out side of the bend.

See also my post here:
http://forums.mikeholt.com/showthread.php?129725-High-Tension-Power-Line-Max-Pull-Angle

That seems to contradict the info I find.

Yes the higher sidewall pressure raises the friction but along less length.


http://www.electrician2.com/calculators/ductwirepull.htm


http://ecmweb.com/mag/electric_simple_calculations_cable/

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[mivey]

That seems to contradict the info I find.

I missed the part where the poster said elbows and jumped to a discussion of sheaves. I would think the sidewall pressure in a conduit would probably be the limiting factor.

However, a bend of a small enough radius in conduit would still take energy to deform the cable and that would increase the pulling tension as it would in a pulley. It should act like a pulley with a huge bearing friction.

For those that want to follow the effect of the sheave diameter and the concepts of the energy used bending the cable:

from IEEE Std 524-2003:
9.1 Sheave diameter
It is generally recognized that as sheave diameters are made larger, the following advantages are gained:
a) The radius of bending of the conductor is increased, so the amount of strain and the amount of relative movement between individual wires in the conductor are reduced. This, in turn, reduces the amount of energy required to bend and straighten the conductor as it passes through the travelers. The force and energy required for such bending and straightening retards the passage of the conductor in much the same way as friction in the bearings of the travelers.
b) The bearing pressures between conductor strand layers are reduced, thus reducing potential conductor internal strand damage. This is commonly known as strand notching.
c) The force required to overcome friction in the bearings is reduced because of the greater moment arm for turning.
d) The number of rotations and speed of rotation are reduced, so wear on the bearings and grooves is alleviated.

...

Once the tension required to support the wire in a static condition is known, the next consideration is the amount of tension needed to pull the wire across the supports, which, in this case, are the travelers. The additional tension required here is primarily the work needed to bend the wire, not to overcome the friction on the bearings of the travelers.

If a solid round metal bar is bent around a radius, the metal on the inside of the bend must compress and the metal on the outside of the bend must stretch. It takes a considerable amount of force acting through an appreciable distance to bend such a rigid bar. Force acting through a distance is called work.

Wire rope or cable strand or conductor is made much more flexible than a solid bar by taking round wires and forming them into a helix. The greater flexibility of such a structure is due to the fact that the wire, at any point on the inside of the bend, does not have to compress, nor does it have to stretch on the outside of the bend. Instead, the wire simply slips around the helix so as to adjust for the shortening on the inside and the lengthening on the outside of the bend.

However, these wires are pressed together with considerable pressure. The pressure is due to and is proportional to the tension in the cable (the pull on the cable). Thus, the slipping of the wire around the helix when the cable is bent is accompanied by considerable friction. Therefore, while it takes a great deal less work to bend a cable than it does to bend a solid bar, it still involves an appreciable amount of work. Friction is proportional to the tension in the cable. Thus, the higher the tension, the more work is required to bend the cable around a radius.

At each point of support, as the cable or conductor is being pulled, the cable or conductor must bend to the sheave radius of the traveler at the entering side and then must be straightened out again at the leaving side. Thus, an appreciable amount of work (or resistance to pull) is developed at each sheave. The amount of work (resistance to pull) is proportional to the tension and is inversely proportional to the diameter of the sheave because it obviously takes more to bend around a smaller arc than around a larger arc.
...

Many variables will affect the assumed 98% efficiency of the travelers. Should very small sheaves be used, the efficiency of the travelers will be much less. On the other hand, cases of large sheaves, over 20 times conductor diameter at bottom of groove, have resulted in efficiency of over 99%. This is important as it must be considered in the selection of pulling and tensioning equipment and pulling lines.

As for saying the bend radius does not increase the tension in general:
Nothing wrong with simplifying assumptions, but they do not negate the mechanics. To say that the bend radius has no effect on the pulling tension without some clarifying assumptions could lead to misconceptions.

From your source: "The radius of bend does not effect the pulling tension." That depends on the assumptions used for the minimum bending radius used during pulls. It would be more correct to say that the effect is a small percentage if the pulling guidelines are followed. In fact, that assumption might not always hold true as evidenced by one of the article references:

From Southwire's Power Cable Installation Guide
Rollers and Sheaves:
...
it is essential for heavier cables to include the force required to bend the cable around the sheave. A 200-pound adder per bend should be used for a three-conductor 500 kcmil copper conductor armored cable.

This comes from IEEE Std 576-2000:

IEEE Std 576-2000
10.3.5 Tension at bends in cable tray
Unlike cables pulled around bends in conduit or duct, bends around free turning sheaves are not treated as tension multipliers. A multiplying effect does not occur since the surface of the sheave(s) turns with the cable. The coefficient of friction, f, for a free turning, well-lubricated sheave is assumed to approach zero. Therefore, e^(fa) is essentially unity.

Although no multiplying effect is assumed at bends in tray installations, an increase in tension is sometimes necessary to account for the force required to bend the cable around the sheave.

This tension adder is usually necessary for heavy, less flexible cable. Experience has indicated that a 667 to 889 newtons (150 to 200 pounds) adder is typical for a 3/C, rated 15 kV, 500 kcmil copper conductor, metallic sheathed cable.

For longer pulls having several bends, this adder could become significant especially with respect to sidewall pressure limitations.

NOTE?The above is based on the use of multi-roller sheave where the coefficient of friction is approaching zero. If this is not the case, then the tension adder for a bend will be a multiplier as used for calculating tension of a conduit bend.

 

[Electron_Sam78]

By the looks of the rig - you could have easily pulled it by hand. Since the wood and the few screws in it would have self-desctructed otherwise.

A safety tip mentioned earlier in the thread about nylon rope eluded you though - if this were a pull worthy of - or in need of a tugger - that rope would have snapped up and gone for the place to do the most damage - like your eyes....

We (three guys) pulled the first few feet by hand and it would not have been an easy pull. We would have needed a couple more guys and a few hours of pulling time. I have to disagree and say it was worthy of a tugger. Maybe not a heavy duty one I'll give you that but I'm glad we had the powered pull on this. As far as the nylon rope goes I'm not sure exactly which one has the spring to it. This was a 3/8" poly rope that didn't seem to have any stretch to it.

Glad it worked out, hopefully you made some money and can invest in a factory built tugger. I sure like the Maxis, I have the 3k and a 10K, but I could not figure out how to do a side pull with either one and dug out the old Greenlee. The best investment was the Maxis triggers, very safe to be able to stop the puller for either end of the pull and the will work with any puller.

Jim

I made money regardless. I'm not an EC any more just a regular employee. This job was just part of the daily grind. We had our budget blown on the wire and conduit. I had to find the pull rope in the shop. We usually do direct burial circuits and are not setup for long or heavy conduit pulls.

 

[ohmhead]

I have used a power vice (a Ridgid 300) and a 2" piece of RMC many times.

Roger

We used a floor mounted power vice to feed meaning turn the spools on roller jack stands 2 inch rigid thur all spools 1/2 in all thread rods one nut one washer thur rigid conduit between each spool attached to spools with a inventive attachment to spool one man feeds one man pulls with tugger .

Its called working together alot and a good radios on site thats what we did years ago before we made enough cash to buy a Greenlee wire feeder .

Roger this brings back old times but iam glad they make these today!

Lots of fun lots of work but it worked

 

[M4gery]

No, I did spend some time trying to find it on Google but it may have been as far back as 85 - 90.


What I remember is that a new young worker for the power company was in a man hole feeding cables and lost both arms. If I recall correctly he had lived.

I know a young apprentice that lost his hand. He was feeding 500's into a 4" pipe and wasn't paying enough attention. The nose got stuck in the pipe somewhere, the tugger stretched the rope and then the nose came loose and the recoil of the stretched rope pulled the conductors in a quick jolt. I've seen that happen many times, but in this instance the apprentices hand was too close to the pipe and got caught between the conductors and pulled it right in.