How to calculate a rolling 90 offset

[comsparky]

I'm not sure what you guys call it, but I call it a rolling 90 offset. Im starting with a 90 then a 30 to get me 11.25 of rise. I could always use a coupling to fix it but I prefer not to. There are plenty of rolling offset calculations when using 45s. I can't find one for 90s.
I usually just bend it up by hand and make adjustments on smaller pipe. In this case I'm working with 3" emt. So adjustments are not easy and I'd rather not waste $70 lengths of pipe if I dont have to.
Anyone have any tips?

Thanks

 

[darekelec]

Get an app ‘conduit bend’ for couple of bucks . It does Calc for you

 

[Tulsa Electrician]

Would not be a back to back 90
Sounds more like a kick 90 since your using a 30 with the 90

 

[comsparky]

Yes some call it a kick 90

 

[comsparky]

Get an app ‘conduit bend’ for couple of bucks . It does Calc for you

They do roll 90s ?
Maybe the one I have isn't very good

 

[tburdick]

I'm not sure what you guys call it, but I call it a rolling 90 offset. Im starting with a 90 then a 30 to get me 11.25 of rise. I could always use a coupling to fix it but I prefer not to. There are plenty of rolling offset calculations when using 45s. I can't find one for 90s.
I usually just bend it up by hand and make adjustments on smaller pipe. In this case I'm working with 3" emt. So adjustments are not easy and I'd rather not waste $70 lengths of pipe if I dont have to.
Anyone have any tips?

Thanks

for 11 1/4" kicked 90*

measure back 22 1/2" from back of 90* for center of bend for 30* kick.

 

[comsparky]

for 11 1/4" kicked 90*

measure back 22 1/2" from back of 90* for center of bend for 30* kick.

Did you plug that into a calculator or app ? If so which one. Thanks

 

[darekelec]

They do roll 90s ?
Maybe the one I have isn't very good

App does everything

 

[TwoBlocked]

The tough part is determining where to put the hook when using a power bender so you get the the desired kick, and shrink, (and gain? ... ) at 30 degrees.

 

[Tulsa Electrician]

I would start with the 881 instructions.
I doubt you can bend what you want as there is not enough leg coming off the 90.

You will need to use something like 15 degrees when there is a 90 in front of the kick.
The chart says for 12" kick (H) you mark Y ( back of 90) at 31.66.

 

[Tulsa Electrician]

Here's a tip, once you place it in the bender and level the 90 measure from bottom of floor to the bottom of the pipe. Then bend to that number plus 11.5 inches. Then dial in for spring back. If you have to do more than one when you get what you want place your angle finder on the bend after spring back and you can use that moving forward to aid the bending.

You can use the chart for most bends. You can also use a calculation to aid in lay out then use the helpful tip.

In your case you have a 90 kick. So the number has to be greater than the 90.
Minium stub is 24 so your number has to be greater than 24. You can see 30 will not work or will 22.5.

What I do is use.
Multiplayer for angle 15= 3.86
11.5 x 3.86= 44.39 from back of 90.
Then subtract for mark. For center of bend
I use 16.5 ( Radius) x 15 (degrees) x .01745 (π÷180) + 3.5 ( pipe diameter) + 3 (pipe saddle)= 11.81
44.39 - 11.81= 32.58 for the end of saddle mark from back of 90. Then use the tip.
Then I know this bend can be done.

 

[comsparky]

Here's a tip, once you place it in the bender and level the 90 measure from bottom of floor to the bottom of the pipe. Then bend to that number plus 11.5 inches. Then dial in for spring back. If you have to do more than one when you get what you want place your angle finder on the bend after spring back and you can use that moving forward to aid the bending.

You can use the chart for most bends. You can also use a calculation to aid in lay out then use the helpful tip.

In your case you have a 90 kick. So the number has to be greater than the 90.
Minium stub is 24 so your number has to be greater than 24. You can see 30 will not work or will 22.5.

What I do is use.
Multiplayer for angle 15= 3.86
11.5 x 3.86= 44.39 from back of 90.
Then subtract for mark. For center of bend
I use 16.5 ( Radius) x 15 (degrees) x .01745 (π÷180) + 3.5 ( pipe diameter) + 3 (pipe saddle)= 11.81
44.39 - 11.81= 32.58 for the end of saddle mark from back of 90. Then use the tip.
Then I know this bend can be done.

Thanks for the tips. I'm getting back to this job on Thursday. I'll be able to wrap my head around all the measurements once I'm onsite standing over the bender and looking at the obstructions Thanks again.