Calculating gate hinge offset ?

[digga]

hi  i was after  some help.  i have to  put up a lot of gates ( both metal & wooden ) and sometimes come up against the age old problem of gates having to rise up a slope as they open but be close to the ground when shut   i know how to achieve this by offseting the bottome hinge.

 \what im after the help with is how to calculate the offset was thinking of maybe doing something on excel to calculate for different width gates and amount of rise needed i done  a bit of a search before posting and come across the self rising gate hinge thread  .

 where i see a reply from john b  said

Distance to offset centres of the hinge pins can be calculated by measuring the vertical distance between the hinge points and multiplying this size by the rise required, the result being divided by the length of the gate

so wanting to check i have this right before messing up anything expensive    i measure the verticle distance between the pins

( must confess been hanging gates for a while and didnt think this measument would make much difference but  here  to learn )

 then  mutiply that by the rise needed and divide that by lengh of  gate  is this including  the eyes  on the gate  so  you  measure it from  the centre  so you have  the mark for your pin location  on the post ?

many thanks

david

 

[bigfootnampa]

Basically this is a simple right triangle problem.  By bringing the top pivot for the gate downhill or moving the bottom pivot uphill (or a combination of the two) you create a line perpendicular to the slope when the gate is opened.  If you lay this out on paper so that a triangle proportional to your gates dimensions has the bottom parallel to the slope the offset from vertical between the pivot points will be the needed offset to make the proper rise in the gates swing.  If you move the pivots closer together vertically, less offset will be needed to make the proper slope in the swing.  I hope this helps you to "see" what John is describing mathematically.  

[digga]

 thank  you  for  taking  the time to reply  its  coming a bit clearer  now as i said  here to  learn  and theres such a lot of valuable knowledge  here  wanted  to  ask a few  questions  even  though some may seem stupid and get  it right.  before  messing up   and still  might  see if i can  do something on excel  to  calculate  offset  for those  gates  where  the   verticle  positions of pivot   is  allready  fixed  on  pre supplied  gates

[Jack Evers]

I would think Exel a bit of overkill, but that's me. It's just a proportion The width of the gate (W) is to the Rise in the gate ® as the spread of the hinges - center to center (S) is to the offset (O). As Bigfoot says, you need the line between hinges perpendicular to the ground.

R/W = O/S or O = R*S/W.'

[pkrankow]

Draw a picture, keep it simple. Everything is similar triangles. The offset of the hinge creates a triangle that has the same angles as the rise of the gate. The rise of the gate is an imaginary triangle underneath the gate panel.

Phil

[doc]

The only issue is that the full rise of the gate only occurs at a 90* opening of the gate. At any point between this position on either side of 90 it is less. That is why offsetting hinges can be used to make a self closing gate or door, or one that will also stay open if moved past 90 degrees from the closed position.

[digga]

thanks  everyone for  the help

[John B]

Seems that is sorted for you then. All points seem to have been covered.

 

 

Great to see somebody using references already been covered without just asking. Well done and Thank you.

[digga]

 yes thanks again  for everyones  help

[LEW PARKER]

I built an offset hinge point for our driveway’s double gate. The gates opens inward. Facing toward the street, the bottom of the right hand gate must rise to clear an upslope in the driveway. Next to the right hand gate post, I installed another post to hold the bottom hinge J-bolt. This takes a lot of the strain off of an angled hinge that otherwise would be attached to the main post. The bottom right of the gate holds the tube that hold the J-bolt pivot. That tube is welded to the threaded shaft of another J-bolt, with the J cut off. That shaft is attached to the bottom right of the gate, in a threaded tube welded to the gate at a right angle. With the extra lengths of threaded shafts, I was able to adjust the gate to parallel the ground when closed, and adjust the necessary rise to clear the slope when open. This sounds complicated without an image.  I’ll try to post a photo. (Nope, didn’t work.)

 

[TWISTEDWILLOW]

Howdy from eastern Oklahoma and welcome to the forum LEW!

there’s a button at the bottom of your post that allows you to add photos,

where bouts you from? What kinda smithin you do?