how to constrain end of one beam to center of another beam

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ericg
Posts: 25
Joined: Tue Jul 15, 2014 1:18 am

how to constrain end of one beam to center of another beam

Post by ericg »

Hi,
I'm trying to learn A2+ by assembling a simple bed/bench type of frame, consisting of 2 long lengths of 4x2 and 3 short 4x2 spreaders. The 2 end spreaders are easy to constrain to the ends of the long lengths but I cannot seem to constrain the middle spreader to the center of the long beams (I have 1 dof to fix)

Hope that makes sense
Eric

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OS: Debian GNU/Linux 11 (bullseye) (KDE/plasma)
Word size of FreeCAD: 64-bit
Version: 0.20.29177 (Git) AppImage
Build type: Release
Branch: (HEAD detached at 0.20)
Hash: 68e337670e227889217652ddac593c93b5e8dc94
Python 3.9.13, Qt 5.12.9, Coin 4.0.0, Vtk 9.1.0, OCC 7.5.3
Locale: English/Australia (en_AU)
Installed mods: 
  * A2plus 0.4.56a
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Bench_Assembly.FCStd
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dan-miel
Posts: 391
Joined: Thu Sep 13, 2018 12:29 am
Location: Spokane WA. USA

Re: how to constrain end of one beam to center of another beam

Post by dan-miel »

ericg wrote: Tue Jul 12, 2022 12:14 pm I cannot seem to constrain the middle spreader to the center of the long beams
Greetings ericg,
Unfortunately, I know of no way to add rectangular parts to the center line of anther rectangular part in A2plus. I normally divide the length of the long beam in two, then minus the width of the center beam. In your case 1960 /2 = 980 – 25 = 955. I use the plane coincident between the end of the long beam and the edge of the center beam, then enter the 955 dimension in the Offset box.
I know this is not the most convenient solution because if you change the length of the bench you need to change the 955 dimension but it is the only one I’ve found. If anyone has a better solution, please post.
Dan Miel
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Bench_Assembly with center.FCStd
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Syres
Veteran
Posts: 2893
Joined: Thu Aug 09, 2018 11:14 am

Re: how to constrain end of one beam to center of another beam

Post by Syres »

dan-miel wrote: Wed Jul 13, 2022 8:24 pm In your case 1960 /2 = 980 – 25 = 955.
I know this is not the most convenient solution because if you change the length of the bench you need to change the 955 dimension but it is the only one I’ve found. If anyone has a better solution, please post.
Dan Miel
Is TopoNaming stopping the use of expressions, as shown below?

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(b_Front_Beam_001_.Shape.Edge10.Length/2) - (b_Side_Beam_001_.Shape.Edge6.Length/2)
I'm aware that if Use experimental topological naming wasn't ticked at time of importing of the objects then it won't work afterwards, so a new file would have to be created and importing to repeated.
ericg
Posts: 25
Joined: Tue Jul 15, 2014 1:18 am

Re: how to constrain end of one beam to center of another beam

Post by ericg »

Thanks for the replies,
Don't think any of this is going to help as I have several woodwork designs that are not simple edge to edge boxes, one of whic is a router table whre the top overhangs all sides and I really don't want to be fiddling with offsets,
Cheers
Eric
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