Calculating kicks and offsets with factory bends

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tld38

Member
Location
Cleveland
Hello all! used a factory 30 deg kick attached a factory 90, and measured. Stub height measured 14 1/2 inch. I needed a 28-1/2 inch kick, so I cut a 14 inch nipple and then measured, (14-1/2+ 14= 28-1/2) my kick ended up at 24 inches to bottom. I,m not sure if I,m doing something wrong here, Can anyone advise me of the math formula I should use when using factory 15,30, deg kicks and factory 90,s sent out to job. I,m just not sure if I am using wrong formula here. Thanks much!
 

Fulthrotl

~Autocorrect is My Worst Enema.~
Hello all! used a factory 30 deg kick attached a factory 90, and measured. Stub height measured 14 1/2 inch. I needed a 28-1/2 inch kick, so I cut a 14 inch nipple and then measured, (14-1/2+ 14= 28-1/2) my kick ended up at 24 inches to bottom. I,m not sure if I,m doing something wrong here, Can anyone advise me of the math formula I should use when using factory 15,30, deg kicks and factory 90,s sent out to job. I,m just not sure if I am using wrong formula here. Thanks much!

lay the stuff out on the floor, and measure what you want to have happen.

most "factory 30's) etc. aren't thirty degrees, so formulas won't help you a lot.
 

iwire

Moderator
Staff member
Location
Massachusetts
I agree with FullT above, I lay stuff like this on a floor, often against a wall or parallel with a line on the floor to use as a straight edge to measure from.
 

tkb

Senior Member
Location
MA
Hello all! used a factory 30 deg kick attached a factory 90, and measured. Stub height measured 14 1/2 inch. I needed a 28-1/2 inch kick, so I cut a 14 inch nipple and then measured, (14-1/2+ 14= 28-1/2) my kick ended up at 24 inches to bottom. I,m not sure if I,m doing something wrong here, Can anyone advise me of the math formula I should use when using factory 15,30, deg kicks and factory 90,s sent out to job. I,m just not sure if I am using wrong formula here. Thanks much!

You simply lengthened the length of the run and didn't tale into consideration the Pythagorean theorem.

To get a rise of 14" your nipple should have been 28". It's the same multiplier as bending at 30°, 2.

Here is a link to a calculator.
http://www.csgnetwork.com/righttricalc.html

I agree that factory bends are not very accurate.
 

tkb

Senior Member
Location
MA
Not as far as degrees of bend or the location of the bend in the length of pipe so you get a different measurement on each side of the 90.

I have seen many factory 90°s that have been open or closed.
The straight legs are always different from each manufacturer.
I have never checked the accuracy of other bends.
I am sure they are about as accurate as the 90° bends.

For the most part the angles are close but not perfect.
 

tld38

Member
Location
Cleveland
Factory kick calculations

Factory kick calculations

I,m sorry if I did not clarify this. I had a 30deg kick sent out to job along with a factory 90. I attached the factory 90 to the kick, then i leveled and measured the 90. I came up with 14-1/2 inches to bottom of the 90 deg stub. I needed a 28-1/2 inch kicked 90. So I simply did the math and decided to cut a nipple at 14 inches long, thinking that that would give me the 28-1/2 that I needed. So is it correct that I should have cut a nipple at 28 inches to get the desired 90 deg kick at 28-1/2 inches? Thanks much to all!
 

iwire

Moderator
Staff member
Location
Massachusetts
I have seen many factory 90°s that have been open or closed.
The straight legs are always different from each manufacturer.
I have never checked the accuracy of other bends.
I am sure they are about as accurate as the 90° bends.

I was building electric rooms at a CES job using a lot of 2" sweeps and I was having a hard time making it look good. I learned the straight legs of the 90s were different lengths on the same 90 depending on which way you held it.
 

tkb

Senior Member
Location
MA
I was building electric rooms at a CES job using a lot of 2" sweeps and I was having a hard time making it look good. I learned the straight legs of the 90s were different lengths on the same 90 depending on which way you held it.

Excellent quality control. :lol:
 

tkb

Senior Member
Location
MA
I,m sorry if I did not clarify this. I had a 30deg kick sent out to job along with a factory 90. I attached the factory 90 to the kick, then i leveled and measured the 90. I came up with 14-1/2 inches to bottom of the 90 deg stub. I needed a 28-1/2 inch kicked 90. So I simply did the math and decided to cut a nipple at 14 inches long, thinking that that would give me the 28-1/2 that I needed. So is it correct that I should have cut a nipple at 28 inches to get the desired 90 deg kick at 28-1/2 inches? Thanks much to all!

You were clear, and wrong with your calculations. You only lengthened the conduit and did not take the angle into account.

Draw it out on the floor to see where you went wrong, or scale it down and draw it on paper.
 

Cow

Senior Member
Location
Eastern Oregon
Occupation
Electrician
I learned the straight legs of the 90s were different lengths on the same 90 depending on which way you held it.

Yep. We run a fair amount of rigid and the factory 90's we get can vary in length by about 1/2-3/4" sometimes. As long as you know about it, you can sometimes use it to your advantage when you need one just a little shorter or a little longer.

Long radius fiberglass sweeps seem to have the worst quality control I've seen. I expect 88, 90, 92 etc, but I've had some that probably weren't even 80 degrees. I save those for the ones that stay underground, and find the better ones for the stubups.
 

kwired

Electron manager
Location
NE Nebraska
I,m sorry if I did not clarify this. I had a 30deg kick sent out to job along with a factory 90. I attached the factory 90 to the kick, then i leveled and measured the 90. I came up with 14-1/2 inches to bottom of the 90 deg stub. I needed a 28-1/2 inch kicked 90. So I simply did the math and decided to cut a nipple at 14 inches long, thinking that that would give me the 28-1/2 that I needed. So is it correct that I should have cut a nipple at 28 inches to get the desired 90 deg kick at 28-1/2 inches? Thanks much to all!
If you were bending a single piece to fit there with 30 degree bends you would have double the offset distance between centers of the bends, but if you have pre-bent elbow fittings you need to deduct the length from center of bend to the end of the elbow fittings, what is left over is how long your nipple needs to be. With possible compensation for variances at coulings - RMC for example doesn't usually butt up to the piece on other side of coupling as close as EMT does.
 

tld38

Member
Location
Cleveland
Factory kick calculations

Factory kick calculations

I added a 14 inch nipplebetween the factory 30 deg kick, and the factory 90, I did not change the angle, it would still be at a 30 deg angle, so assuming that adding the 14 inch nipple to an existing kicked 90, measuring 14-1/2 inches to bottom of 90, would give me a 28-1/2 inch kick is incorrect? So I should just transpose this on the floor or wall, and figure it out from there, meaning that there is no formula to work here? Again, at the start, I simply connected the factory 30, and attached it to the factory 90, and I measured 14-1/2 inches to the bottom of 90 when it was level. Thanks
 

ADub

Senior Member
Location
Midwest
Occupation
Estimator/Project Manager
You need 57 inches from the center of the of the 90 to the center of the 30° bend.


Sent from my iPad using Tapatalk
 

tld38

Member
Location
Cleveland
Factory kick calculations

Factory kick calculations

I see, so if I put two factory 30 deg kicks together, and measure the offset to be 4 inches, then I need to deduct the centers of bend from each kick to the end of fitting. So in the above example, with an offset of 4 inches, the center to center on the kicks should be 8 inches, cosecant of 30 being two, which is my hypotenuse. So if I want a 12 inch offset, I would have to cut a 16 inch nipple. But again, my problem was with the kicked 90. I,m just not sure how to do the math correctly for making a kicked 90 with a factory 30,a nd factory 90, other than laying it out on the floor or wall as I am being told. Thank for everyones help here.
 

kwired

Electron manager
Location
NE Nebraska
I added a 14 inch nipplebetween the factory 30 deg kick, and the factory 90, I did not change the angle, it would still be at a 30 deg angle, so assuming that adding the 14 inch nipple to an existing kicked 90, measuring 14-1/2 inches to bottom of 90, would give me a 28-1/2 inch kick is incorrect? So I should just transpose this on the floor or wall, and figure it out from there, meaning that there is no formula to work here? Again, at the start, I simply connected the factory 30, and attached it to the factory 90, and I measured 14-1/2 inches to the bottom of 90 when it was level. Thanks
There is a formula, just not sure what shape your raceway is trying to end up at.

What is a "kicked 90"?

If you draw a right triangle to correspond to your bend(s) the trigonometric functions to find missing lengths or angles will work.

Laying out on the floor is often just as or even easier though.
 

ADub

Senior Member
Location
Midwest
Occupation
Estimator/Project Manager
I see, so if I put two factory 30 deg kicks together, and measure the offset to be 4 inches, then I need to deduct the centers of bend from each kick to the end of fitting. So in the above example, with an offset of 4 inches, the center to center on the kicks should be 8 inches, cosecant of 30 being two, which is my hypotenuse. So if I want a 12 inch offset, I would have to cut a 16 inch nipple. But again, my problem was with the kicked 90. I,m just not sure how to do the math correctly for making a kicked 90 with a factory 30,a nd factory 90, other than laying it out on the floor or wall as I am being told. Thank for everyones help here.

I don't know exactly what you're asking but I know what you need, a 28.5" kicked 90 with a 30° kick. To achieve that all you need to know is you need 57" between the center of the 90 and the center of the kick, this fact doesn't change regardless of pipe size or the sloppiness of your factory elbows.


Sent from my iPad using Tapatalk
 

tld38

Member
Location
Cleveland
Factory kick calculations

Factory kick calculations

Thanks everyone, I kind of thought the distance from the center of the 90 to the center of the kick would have to be 57 inches. I will verify this on the job. I just need to deduct the center of kick to the end of kick, and also deduct the center of 90 to the end of 90, and make up the difference with a nipple. Thanks
 
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