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  1. #21
    Looks good Eddy Only thing I'd change is to add another support for the bed.

    Be careful when welding the diagonals where they meet in the centre, don't weld both at same time has you'll be putting a lot of heat in one spot.

  2. #22
    Yeah, I was thinking it look fine but might as well add another vertical piece in the center of the 100x50 box section on both sides. The diagonals are already supporting it well though, so if adding a support to the center you could possibly make the diagonals shorter if it ends up more convenient when it comes to ordering the steel.

  3. #23
    Quote Originally Posted by Jonathan View Post
    Yeah, I was thinking it look fine but might as well add another vertical piece in the center of the 100x50 box section on both sides. The diagonals are already supporting it well though, so if adding a support to the center you could possibly make the diagonals shorter if it ends up more convenient when it comes to ordering the steel.
    Think it might benefit from a combination of both, centre vertical and shorter diagonals along with more bed supports. The diagonals would then fall in-line and support the extra bed supports and the vertical would support centre.
    The shorter diagnols would then make it so you could add shelf if needed and not impede so much.?

    Out of both suggestions the extra bed supports is the one I'd deem most beneficial.!

  4. Thanks for the feedback.
    At first I had a centre vertical but after reading about the roof trusses where forces are pressing down from the top it is redundant for all practical purposes, force are directed down the diagonals into the legs, of course this only applies if the diagonals are within a particular angle to vertical which in my case they are. The mantra for the trusses was to create triangles, which I'm sure we all know about.
    I'll have another look at a centre vertical and two shorter diagonals and see what it looks like, I'm trying to keep material to a minimum although as with a workbench it's best to have a bit of weight about it.
    Now I look at it again I can see the bed needs more support so I'll add two more intermediate cross members.

    The welding plan is to tack it all round then do like bolting a cylinder head down by jumping around apposing joints to fully weld them, hopefully this will prevent too much heat build up in one area.

    Edit: new options added, what's the verdict on best option ? ( just measured and there's less material in Option 2 )

    Option 1 - side diagonals only + extra bed cross members

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    Option 2 - centre vertical, smaller diagonals moved to meet new bed cross members + extra bed cross members

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    Last edited by EddyCurrent; 21-10-2013 at 09:41 AM.

  5. #25
    For me, option 1 looks better since the triangulation supports the point where the top rails attach. If you want to save material you could go for smaller section tube for the triangulation pieces and the bottom rails since there should be little or no bending moment there. If you want more stiffness you could triangulate each bed rail the same way you have done at the ends.

  6. Thanks, Yes I think you are correct about using smaller section for some parts but I already have the material shown and I'm only wanting to save material to keep the weight down rather than cost.
    It's probably fair to say either option would be fine so I'll see if anyone else is kind enough to give their judgment first.

  7. #27
    Hi Eddy,

    for sure you know from the other threads already my preference is not for that type of design, i like 80x80 and 100x100 x 3mm, but your design looks ok for the job intended.

    However just some points from design and strength point of view. Forget about the 1m more or less for a moment, as this profile is not so costly or heavy.

    The main principles should be: simple, all parts under equal load , no parts that transmit the flex from above to the same place bellow, divide and conquer/strengthen :-) / and no parts that serve only one purpose, so:

    -look at drawing 1 and 2 . The bar at the lower part that is in the middle of the rectangular. I don't like it. If there were 2 of them , they would keep the table from twist. Now that is only one in the middle, it just holds both long sides at same distance. Not only that but transmits the flex from above in the same place bellow. And separates only in 2 the long sides.
    i would put 2 of them or none, instead solder 4 diagonals in such a way that the long and the short sides are separated each in 3 equal pieces, or somewhere near it

    -diagonals on the sides on 1, separate the upper rail support only in 2 pieces, and on drawing 2, they separate the upper rail support onto 3 pieces but not equal and also are soldered very high on the legs.

    that leads me to the next
    -the middle side support in drawing 2 does exactly what should not be done, transmit the flex from the middle on the exactly same place bellow.

    Solutions? Think in arcs. Like the door of a stone house or castle or so. 1 short horizontal bar each from one side, soldered 15cm below the rail supports directly to the previously suggested diagonals position will strengthen the arc, permit the diagonals to go lower at their low ends, and that combined with the removal of the middle vertical bar and replacing the bottom middle bar with diagonals will make everything stronger, resistant to twist and most importantly remove any push from the lower rectangular replacing it with pull, which in fact is way stronger. Or no horizontal bars , the rails supports are double and look quite strong in vertical direction...You can pull a lot but push very little :-)

    Just an idea how my thoughts go, there are other ways to do it also. It would work like this and like that, though there is quite a satisfaction achieving some perfect shape!

    PS. Lowering the diagonals on the sides will achieve the following. Now if pressure is applied from above in the middle, the diagonals push the legs in the middle and try to bend them. If slightly lowered their end, they will start pulling the lower part long sides and remove the push from the legs.
    Last edited by Boyan Silyavski; 21-10-2013 at 02:29 PM.

  8. Quote Originally Posted by silyavski View Post
    instead solder 4 diagonals in such a way that the long and the short sides are separated each in 3 equal pieces, or somewhere near it
    Quote Originally Posted by silyavski View Post
    Solutions? Think in arcs. Like the door of a stone house or castle or so. 1 short horizontal bar each from one side, soldered 15cm below the rail supports directly to the previously suggested diagonals position will strengthen the arc, permit the diagonals to go lower at their low ends, and that combined with the removal of the middle vertical bar and replacing the bottom middle bar with diagonals will make everything stronger, resistant to twist and most importantly remove any push from the lower rectangular replacing it with pull, which in fact is way stronger. Or no horizontal bars , the rails supports are double and look quite strong in vertical direction...You can pull a lot but push very little :-)
    silyavski, I knew you could not resist to comment on a frame design

    I got the first part but I'm sorry I did not fully understand how to draw everything you said in the second part, but here is some of it

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  9. #29
    Quote Originally Posted by EddyCurrent View Post
    silyavski, I knew you could not resist to comment on a frame design

    I got the first part but I'm sorry I did not fully understand how to draw everything you said in the second part, but here is some of it

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    It was irresistible

    Sorry about my English.

    I meant what you did to the sides to do it at the base square and remove the middle piece / the plane at the bottom, the bottom horizontal rectangular plane i am talking/

    At the long side planes which you changed, remove the lower 2 diagonals and solder there what you call gussets instead /yellow/. And now that the 2 remaining diagonals are ok at their upper ends, make them longer below to go and touch to 20cm up, measured from the bottom of the legs. Dont move their upper ends

    Make same at your short side vertical planes/ the face of the machine and the back/ and there you have it. Here you should shorten more the diagonals and make them touch 20cm from bottom or even higher.

  10. Don't be sorry for your English it's fine, it's not easy to explain this thing exactly.

    I think this is how you mean

    Option 3

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    So for anyone else there are now 3 options, this one and two in post #24

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