Four point saddle.

[kda3310]

I can bend a four point saddle by bending one offset then turning the bender 180 degrees and then bend the other off set. However, I want to know how to bend a 4-point saddle without turning my bender 180 degrees. For example if I wanted to start my 4-point saddle at the very end of the pipe being my first bend how do I continue without turning the bender 180 degrees. I am trying to bend a three-quarter inch rigid conduit. My obstacle is 5 inches away 2 inches high and 10 inches long. I have seen this done but do not know how to do it myself or how to calculate where to make the marks.

 

[Dennis Alwon]

A lot of couplings....

 

[Dennis Alwon]

Since I never did one I will quote from this pdf that I have.. I think it is from HatVideo.com

4 Point Saddle
Picture an Offset that goes straight, then up, then levels off. Now, picture it continuing straight a little bit, then going back down to the original level, and going straight again. This is a 4 Point Saddle. To make a 4 Point Saddle you need to have two measurements; the Depth of the obstacle, and the Width of the obstacle. In the video we used a Depth of 8," and a width of 16."
Since the width is 16," the center of the 4 Point Saddle will be 8" from the edge of the obstacle. However, you do not want the 4 Point Saddle to be tightly wedged into place. What you need to do is to allow a little bit extra to clear the obstacle. In the video we used 2" on each side. After marking a center point, make a mark on both sides 10" away from the center. Think of these marks being necessary to clear Width of the obstacle. Now, you need to make your marks to allow you to clear the Depth of the obstacle. These are the same as making an Offset.
The formula for the distance between the marks is:
Depth X Multiplier = Distance between marks.
.
8" X 2 = 16"
On each side of the pipe, you will make a mark 16" away from the mark that is 10" from the center mark. Make your bends using the STAR mark on the bender. In the video, we made four bends of 30 degrees each. A 4 Point Saddle has four bends. Think of it as the pipe Offsetting up, the Offsetting back down.

 

[kda3310]

Yes and this is how I know how to bend a 4-point saddle. However, they show you to turn the bender away from your closest end to start the bending. I want to turn my bender towards my closest end to gain the precious few inches I need to put this in a tight spot.

 

[Smart $]

FWIW, if it is only 5" to your obstruction (D_OBS), you are SOL.

Regardless, this is the same as bending two offsets in succession, but you will need a couple more "numbers" to do it if you want to place the first offset so its second bend ends exactly at the obstruction (or a specific clearance distance before the obstruction).

You need to determine the shrink of one offset. Shrink is approximately (offset)×(1 – cos[bend angle]). This is how much closer the far end of the conduit will be to the near end after the offset is bent.

Next, you need to determine how much conduit is used in one bend (D_BEND): ([bend angle]/180°)(pi)(r), where "r" is the bend radius.

Then determine the distance to the start of the second bend...

D_OBS + Shrink – D_BEND
​

You can put your bend mark here if you are using a hand bender. If you are using a powered bender, you will have to adjust accordingly for where you put the bend mark with respect to the start of the bend. On Greenlee 555 it is IIRC about 3" towards the near end of conduit.

Subtract your offset bend to bend distance, and place bend mark for the start of first bend.

Bend conduit.

Measure 10" from end of second bend*, place bend mark for third bend (adjusted if need be for power bender). Add bend to bend distance and place bend mark for fourth bend.

Bend conduit.


*Note that...

D_OBS + Shrink​

...should be the end of your second bend.... and you can use this to measure and place bend marks for bends 3 and 4 before bending bends 1 and 2.

 

[packersparky]

I can bend a four point saddle by bending one offset then turning the bender 180 degrees and then bend the other off set. However, I want to know how to bend a 4-point saddle without turning my bender 180 degrees. For example if I wanted to start my 4-point saddle at the very end of the pipe being my first bend how do I continue without turning the bender 180 degrees. I am trying to bend a three-quarter inch rigid conduit. My obstacle is 5 inches away 2 inches high and 10 inches long. I have seen this done but do not know how to do it myself or how to calculate where to make the marks.

Figure out where the center of your bends are with the angles you use the most (60°, 30 °, 22.5°, etc.). Put a mark with a sharpie on your bender where the center of the bends are and use the center marks instead of the arrow. You won't have to reverse the pipe when you use the center marks.

 

[kwired]

Figure out where the center of your bends are with the angles you use the most (60°, 30 °, 22.5°, etc.). Put a mark with a sharpie on your bender where the center of the bends are and use the center marks instead of the arrow. You won't have to reverse the pipe when you use the center marks.

You still need to factor in shrink to know where to place the first offset.

Most hand benders have a mark for center of a 45 deg bend, the other angles you kind of have to figure out on your own where center is.

 

[kda3310]

I found a video of someone doing the bend how I am taking about doing it. Just need to adapt it to an Ideal Bender.

https://www.google.com/url?sa=t&sou...F6fOYJEPE7qrib5YA&sig2=DuuHP2u6ek8KyXhJ7WCpmQ

 

[kwired]

I found a video of someone doing the bend how I am taking about doing it. Just need to adapt it to an Ideal Bender.

https://www.google.com/url?sa=t&sou...F6fOYJEPE7qrib5YA&sig2=DuuHP2u6ek8KyXhJ7WCpmQ

That did not tell you anything on how to determine where in the length of finished run the saddle ends up at, or how long of a saddle may be needed. If you place first two marks and last two marks equal distance apart and make same degree of bends on all bends you will have an equal offset on each end.

All he did was make two 3 inch offsets and coincidentally had put six inches between marks 2 and 3, but that doesn't mean it will saddle a 6 inch wide obstruction either.

 

[Dennis Alwon]

You still need to factor in shrink to know where to place the first offset.

Most hand benders have a mark for center of a 45 deg bend, the other angles you kind of have to figure out on your own where center is.

Don't know if this helps either but it is a 4 pt saddle with shrinkage-- I guess they are bending conduit underwater....

4 Point Saddle With Shrinkage
The 4 Point Saddle made from a fixed point is made like a regular 4 Point Saddle with the addition of one more calculation. That is, you must consider the Shrinkage. This extra calculation means that you need to make one more measurement. That will be from the fixed point to the center of the obstacle. In the video this distance was 36." The same obstacle is used, so the width (16") and depth (8") are the same. If a 30 degree angle is used, how much Shrinkage is there?
Shrinkage for a 30 degree bend is 1/4" per inch of depth.


1/4" Shrinkage per inch of depth X 8" depth = 2" of Shrinkage.
36" + 2" Shrinkage makes the "true center" of the bend at 38."
Measurements will be made from the "true center." Now, the rest of this bend is just like the 4 Point Saddle that you made earlier. The width is 16." Half of this is 8," and 2" more will be added so that the pipe is not so tight on the obstacle. Next, you make the marks as though you were making an Offset.
The formula for the distance between the marks is:
Depth X Multiplier = Distance between marks.


8" X 2 = 16." Once again, on each side of the pipe, you will make a mark 16" away from the mark that is 10" from the "true center" mark. Make your bends using the STAR mark on the bender. Next, make the four bends of 30 degrees each.
Take a few minutes and see if you can calculate the same bend using a 22 degree angle. Remember the following measurements:
The distance from the fixed point to the center of the obstacle is 36."
The width of the obstacle is 16," and again it will be cleared by 2" on each side.
The depth of the obstacle is 8."
Shrinkage for a 22 degree bend is 3/16" per inch of depth.
3/16" Shrinkage per inch of depth X 8 depth " = 1-1/2" of Shrinkage.
36" + 1-1/2" Shrinkage makes the "true center" of the bend at 37-1/2."
Measurements will be made from the "true center." Now, the rest of this bend is just like the 4 Point Saddle that you made earlier. The width is 16." Half of this is 8," and 2" more will be added so that the pipe is not so tight on the obstacle. Next, you make the marks as though you were making an Offset.
The formula for the distance between the marks is:
Depth X Multiplier = Distance between marks.


8" X 2.6 = 20.8", just a bit more than 20-3/4."
Once again, on each side of the pipe, you will make a mark 20-3/4" away from the mark that is 10" from the "true center" mark. Using the STAR mark on the bender, make the four bends of 22 degrees each. Is this the answer that you came up with?
One more time, take a few minutes and calculate the measurements to make a 4 Point Saddle with Shrinkage in the same situation using 45 degree angles.
Shrinkage for a 45 degree bend is 3/8" per inch of depth.
3/8" Shrinkage per inch of depth X 8" depth = 3" of Shrinkage.
36" + 3" Shrinkage makes the "true center" of the bend at 39."
Measurements will be made from the "true center." Now, the rest of this bend is just like the 4 Point Saddle that you made earlier. The width is 16." Half of this is 8," and 2" more will be added so that the pipe is not so tight on the obstacle. Next, you make the marks as though you were making an Offset.
The formula for the distance between the marks is:


Depth X Multiplier = Distance between marks.
8" X 1.41 = 11.28," which is just a tiny bit bigger than 11-1/4."
Once again, on each side of the pipe, you will make a mark 11-1/4" away from the mark that is 10" from the "true center" mark. Using the STAR mark on the bender, make the four bends of 45 degrees each. Is this the answer that you came up with?

 

[ADub]

If you use the center of bend method you can bend saddles all the way at the end of the pipe without ever flipping your bender. Works great for chicago and 555s too


Sent from my iPhone using Tapatalk

 

[Smart $]

... Shrink is approximately (offset)×(1 – cos[bend angle]). ....

Correction:
(offset)×(1/cos[bend angle]-1)

Shrink per inch of offset for common bend angles:
22.5° 0.082"
30° 0.155"
45° 0.414"
60° 1.000"