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Brace Layout Question and Answers

Started by Jim_Rogers, June 22, 2004, 01:51:34 PM

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Roger Nair

What is simpler lengths of 3, 4 and 5 and angles expressed as 4/3 slope or a computer program that does not work directly with the bedrock 3-4-5 triangle that spits out fractional answers to whole number solutions.  TRy this, draw the post and beam with half inch deep housings at 3 and 4 foot brace legs.  Then draw a line from the intersection of the shoulder and cheek of the housing from post to beam.  Then draw a line from the surface to shoulder intersection from post to beam.  The two lines are not parallel.  The line from shoulder-cheek intersection represents the true brace length (5') and true slope (4/3).  The method I advocate uses the basic root measurements and accounts for the deviation of the surface of the brace to the layout line and avoids the consequences of a computer program that very few will ever buy or use.
An optimist believes this is the best of all possible worlds, the pessimist fears that the optimist is correct.--James Branch Cabell

Jim_Rogers

I agree with you. The lines are not parallel. I agree with you that this is a program that the average home user will never buy.

My point was that I was trying to show carpenter how it could be done easily with standard methods that I taught him when we were together face to face.

It really doesn't matter if the leg is off by 1/8" or the diagonal off by 1/16" if the angles are right and it looks good, and it is easy to cut and assemble.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Roger Nair

The importance of the two lines not being parallel is that the surface of the brace will not meet the surfaces of the beam and post in an even manner.  I'm just trying to get closer to a more idealized relationship while remaining simple in scheme.  In the effort to remain simple, normally I specify regular plan and elevation dimensions mostly to the half inch and slopes to whole number ratios.  When I must calculate diagonal lengths and sloping lengths, I rely on a scientific calculator working to .0001" to avoid rounding errors in stringed calculations and converting results to fractional values only at the end.  All my layout is by sharp tools.  I testify that I get reasonable results with less fuss, I follow a discipline of striking lines into wood without tic marks or pencil lines.  I confirm all computer calcs on a scratch pad.  Over forty five years ago as a curious helper, I asked the carpenter I was working for who seemed to pull details out of the air "How do you know that all this is going to go together?"  Earl replied, "It's going to work because I say it's going to work."  Sharp attention, sharp attitude and sharp tools is what will carry a job, those must be made by the carpenter, to rely on a computer that wants to defy the Pythagorean Theorem is not helpful, in a general information format.  Remember the questioner who asked how to deal with 3-4-5 braces that seem to have oddities in layout. 

Sorry, I think I'll rant-rave all the way to the grave.
An optimist believes this is the best of all possible worlds, the pessimist fears that the optimist is correct.--James Branch Cabell

Jim_Rogers

How many times must I tell you that I agree with you.

I'm happy your methods work for you.
My method may not even work for me. I have not tried it, yet.
I may never try it.

I was just trying to help carpenter to understand that it could be possible to layout a brace that looks close to a 3-4-5 brace layout without being exactly 3-4-5 with a method that may work.

You can say all you want that it doesn't work. And I'll agree with you again.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Mad Professor

I'm sure you can layout 3 4 5 braces using a compass/divider but the layout is going to be more tedious than a 1 1  root 2 braces. 

The sides of the triangle can be measured exactly using turns of a unit circle (compass/divider) and connecting the sides on the brace tie and post, squares the post and tie. 

Laying out the brace mortices and tennons with a divider is going to take some thought.............I'll work on it


Rougespear

In my travels through the literature, I see housing depths for 36" braces ranging from 1/2" to 1".  What's the normal/typical/conventional housing depth for 4x6 braces?
Custom built Cook's-style hydraulic bandmill.

Jim_Rogers

That will depend on the general frame rules of the frame.
Those should be established up front to tell you what each joint should be/have for a housing.

In Jack's book, he used 1" as he didn't know where in the country or the world that frame would be cut and erected. So to cover all the bases he said 1" but we never do that we just use 1/2"

The 14' x 16' screen porch frame we're working on was drawn as a free standing pavilion and the designer (not me) made all the housings 3/4". Worst mistake ever. There is no 3/4" slot on any "big Al" the old one or the new one. We had to add a 1/4" shim to get to use the "new Al". What a nightmare.

Sometimes housing, like at the post where the tie beam sits, need to be 1" for a larger shelf for the tie beam to sit on.

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Roger Nair

In a strict sense, for square rule. the depth of the  gain relates to the variation in raw timber dimension, however in the practical realm of well sawn stock 1/2 is fairly common.  You just need to survey the stocks min. and max. dimensions  Remember you are not reducing the stock by a constant rather you are correcting the stock at the joint to a common dimension.
An optimist believes this is the best of all possible worlds, the pessimist fears that the optimist is correct.--James Branch Cabell

Jim_Rogers

Yes, I agree with Roger, you're not cutting it a 1/2" under your cutting it to the inside timber. So when we're working with 8x8, the layout is 7 1/2".

Some students would get mad at me when I corrected them and said "where not making housing 1/2 inch".

We're making the timber 7 1/2". As the timber could be bigger or smaller than 8" and that would mean that the housing would be more or less than 1/2".

You really need to think of it as making it 7 1/2". Of course this is when they are all rough sawn timbers.
With planed on all four sides timbers that are true then you can say the housing is 1/2".

Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

Rougespear

Thanks Jim and Roger.  I asked because I was unsure if the housing was for a bearing ledge (i.e. a necessity for structural reasons), or just a convention of square rule framing - I realize now it is the latter.  Thanks for the clarification.  In hindsight, I assume the "bearing" aspect of the problem is addressed by the bearing nose of the brace.  Understood!

I will be the sawyer and will make sure that my 1/2" square rule (perfect timber within) will account for the max variation in timber dimensions.

Cheers!
Custom built Cook's-style hydraulic bandmill.

klpauba

Not to belabor the point, but ...

How about a 30-60-90 degree brace layout instead of a 3-4-5 layout?  I think the program that Jim uses was adjusting the legs of the 3-4-5 triangle so the measurement of the angles were in whole degrees.  This makes sense to me since it would be difficult to layout fractional angles.

Using a 30-60-90 triangle is not that far off of a 3-4-5 (36.87-53.13-90 degree) triangle and has the same advantage as the 45-45-90 degree triangle in that two of the three lengths can be easily calculated (and can be whole numbers) while the remaining is a fractional dimension.  In the 30-60-90 triangle, if the hypotenuse is x, the shorter leg is x/2 and the longer leg is x*sqrt(3)/2.

Maybe the program Jim uses would dimension out this type of brace perfectly since the angles would remain whole numbers (unless he is unable to enter the length of the hypotenuse and shorter leg to force the calculation of the longer leg).

Now, whether the 30-60-90 brace provides adequate reaction to the racking forces in a frame, I cannot answer.

Roger Nair

Klpauba, I have no issue with your math, but as a retired lifelong carpenter, I would ask what are the tools of your kit?  If you don't have an alpha square with quadrant or the Orem super square, then it would be better to solve angles by using slope ratios regulated with the common framing square.  A carpenter can frame a building to a high standard without knowing the degree of arc of many significant angles, it's all worked out with slope ratios of right triangles.  If I need to solve framing problems with angles of arc, I use a calculator that handles trig and roots and convert solutions to slope, so I still use the framing square as the regulating tool.  Good luck.

P.S.  I like to take what seems like the most direct path and that is a matter of tools and habit. 
An optimist believes this is the best of all possible worlds, the pessimist fears that the optimist is correct.--James Branch Cabell

klpauba

Quote from: Roger Nair on September 06, 2016, 11:22:40 AM
Klpauba, I have no issue with your math, but as a retired lifelong carpenter, I would ask what are the tools of your kit?  If you don't have an alpha square with quadrant or the Orem super square, then it would be better to solve angles by using slope ratios regulated with the common framing square.
<snip>

No angles involved here.  As I mentioned, a hypotenuse of x and the smaller leg of the triangle is x/2.  Only a framing square is required to lay it out.  It could also be done with only a compass and a straight edge but most of us aren't that primitive.

I appreciate and welcome the dialog!

Roger Nair

Your posts seem to be going in different directions.


"How about a 30-60-90 degree brace layout instead of a 3-4-5 layout?  I think the program that Jim uses was adjusting the legs of the 3-4-5 triangle so the measurement of the angles were in whole degrees.  This makes sense to me since it would be difficult to layout fractional angles."

and

"No angles involved here.  As I mentioned, a hypotenuse of x and the smaller leg of the triangle is x/2.  Only a framing square is required to lay it out.  It could also be done with only a compass and a straight edge but most of us aren't that primitive."

So how do you layout the angles on the brace ends?   



An optimist believes this is the best of all possible worlds, the pessimist fears that the optimist is correct.--James Branch Cabell

klpauba

Not two different directions ... two different subjects.

The first was describing why Jim's program didn't allow a 3-4-5 layout because it seems to force whole degrees.  I offered an alternative where you can layout another right triangle that has a special property where the length of the small leg is one half of the length of the hypotenuse.  It just happens that the triangle with this property is a 30-60-90 degree triangle but there is no need to lay it out using the angles.



It might be hard to see but the dimensions of the hypotenuse given in the image above are 6" and the short legs are 3".  The hypotenuse is coincident with the layout line (offset from the edge of the brace in the same manner used when laying out a 45 degree brace).

Roger Nair

That is, to me, a new method of angle layout, I will put that into my bag of tricks.
An optimist believes this is the best of all possible worlds, the pessimist fears that the optimist is correct.--James Branch Cabell

klpauba

Roger,

As you mentioned in the discussion with Carpenter (Reply #43-44), using a 3/8 layout line for non-45 degree braces is not ideal.  Assuming the brace will have the smaller leg oriented on the tie beam, an offset of 7/16" is necessary on the end that will go into the post. This will mate closely with a pocket depth of 1/2".  If the layout line offset on the other end (at the beam) is also 7/16", the bearing surface will protrude the same amount (1/2") from that brace pocket.  Your method of fashioning a trammel would allow the protrusion to be eliminated.

Another alternative to the trammel would be to calculate the offset on the beam end of the brace based on the chosen brace length.  For example, a 36" brace (measured on a reference line) would have the post-side offset at 7/16" (at the 0" mark) and a beam-side offset of 1/4" (at the 36" mark).  The layout dimensions for this brace are then: 36" hypotenuse, 18" (36"/2) shorter leg and 31+3/16" longer leg.

I recently cut a mailbox post based on Jim Roger's drawing (at his workshop in Nebraska just last week).  I hope to make another one but with the 30-60-90 brace -- I think that looks a bit more refined.

klpauba

For completeness (and for anyone using more primitive methods for laying out joints), this link describes a method to get a 30 degree (or 60 degree) angle using just a straight edge and compass, have a look at http://www-gap.dcs.st-and.ac.uk/~history/HistTopics/Trisecting_an_angle.html (the description is in the third paragraph).  To make the right angle shown in the drawing, use the method described at http://whistleralley.com/construction/c1.htm.

Please note that the method given will trisect a 90 degree angle only -- but is what would be needed for the 30-60-90 degree layout.

Roger Nair

For those who might want to layout a plan or pattern board, I suggest bisecting an equilateral triangle.  That should get you there  quickly without much accumulated error, four lines and five sweeps.
An optimist believes this is the best of all possible worlds, the pessimist fears that the optimist is correct.--James Branch Cabell

Carpenter

I did make 3/4/5 braces for a pergola that I built this spring.  It was actually quite simple.  I laid out a few on scrap 2x6s before cutting any joinery. 

Basically, don't worry about the 3/8" layout line.  I use stair buttons and I had them set on the 9" and the 12" mark.  (Here's a little tip, when you use stair buttons don't set the buttons on the mark, set the buttons where the edge of the wood is on the mark, it will be a little different depending on the buttons you are using and the angle).  So, once I had established that, I had both angles already on the framing square.  I wanted a half inch nose off of the reference face.  So I could put the framing square on the timber and draw the nose, (the bearing surface of the brace).  Without moving the framing square I would put a tick mark at the 1/2" mark from the edge of the timber,  then I could slide the framing square to where it matched the tick mark and mark my shoulder cut.  Then I would slide the framing square back the other way until the 3" line matched up with my shoulder cut and that would be my end cut, if I want a 3" tenon on the brace.  (I intended to make a you tube video of this, it might sound confusing but is really quite simple).  To get the length, just measure down the timber and where the half inch nose of the other end of the brace corresponds with your measurement you can lay out the nose of the other end of the brace, and make a tick mark.  Slide the framing square to where it corresponds with that tick mark and mark your shoulder.  And, by this point you've probably already figured out how to get a 3" tenon without taking out the tape measure.  For the length, trammel points as per Roger Nair's suggestion would be best.  I had pretty good results with a tape measure.  You could also step it off with the framing square.


     

klpauba

Thanks for the procedure, Carpenter!  It's great to close the loop on the 3-4-5 layout.  I would probably prefer this layout over the 30-60-90 since it's closer to the 45 degree layout with about the same effort.  This is yet another example on how the experience of cutting joints (like yours) trumps intellectual exercises (like mine).

Ljohnsaw

Quote from: Carpenter on September 07, 2016, 11:03:12 PM
I did make 3/4/5 braces for a pergola that I built this spring.  It was actually quite simple.  I laid out a few on scrap 2x6s before cutting any joinery. 

Basically, don't worry about the 3/8" layout line.  I use stair buttons and I had them set on the 9" and the 12" mark.  (Here's a little tip, when you use stair buttons don't set the buttons on the mark, set the buttons where the edge of the wood is on the mark, it will be a little different depending on the buttons you are using and the angle).  So, once I had established that, I had both angles already on the framing square.  I wanted a half inch nose off of the reference face.  So I could put the framing square on the timber and draw the nose, (the bearing surface of the brace).  Without moving the framing square I would put a tick mark at the 1/2" mark from the edge of the timber,  then I could slide the framing square to where it matched the tick mark and mark my shoulder cut.  Then I would slide the framing square back the other way until the 3" line matched up with my shoulder cut and that would be my end cut, if I want a 3" tenon on the brace.  (I intended to make a you tube video of this, it might sound confusing but is really quite simple).  To get the length, just measure down the timber and where the half inch nose of the other end of the brace corresponds with your measurement you can lay out the nose of the other end of the brace, and make a tick mark.  Slide the framing square to where it corresponds with that tick mark and mark your shoulder.  And, by this point you've probably already figured out how to get a 3" tenon without taking out the tape measure.  For the length, trammel points as per Roger Nair's suggestion would be best.  I had pretty good results with a tape measure.  You could also step it off with the framing square.
Please do, I have a LOT of braces to make...

 
John Sawicky

Just North-East of Sacramento...

SkyTrak 9038, Ford 545D FEL, Davis Little Monster backhoe, Case 16+4 Trencher, Home Built 42" capacity/36" cut Bandmill up to 54' long - using it all to build a timber frame cabin.

ziggy

Bumping an oldie but a goodie here... 

Any tips for laying out brace mortises to be flush with the inside face (which is opposite the reference face) of posts and beams? I'm thinking a brace with a single shoulder. I'd like the braces to be to the inside of timbers to be able to install screen (in a frame) flush with the outside of the timbers. Any thoughts on that? 

Oh, square rule and irregular timbers, not mill rule. 

Jim_Rogers

Using the measurements from the adjacent face you should be able to create the joint on the inside face. You'll need to be consistent with your offsets. What I mean is if your timbers are over sized by an eight of an inch your mortise location maybe offset from the inside face by 1/8 of an inch.

When we did this frame:


 
The braces were to the inside, for the same reason, and it came out ok.
good luck
Jim Rogers
Whatever you do, have fun doing it!
Woodmizer 1994 LT30HDG24 with 6' Bed Extension

ziggy

Ok nice, I try to avoid measuring off the non-reference face for obvious reasons. Will just have to be careful like you said. Thanks!


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