[Hezz]

Looks good, how did you get the putty flat. Did you lap it with that surface plate?

It looks like you have a nice roll around steel stand for it. Maybe you should consider making the upper gantry and side beams out of steel and then fill them with cement. It will be much stiffer and very well damped.

Overall the project is looking good.

[Chazaxl]

Looks good, how did you get the putty flat. Did you lap it with that surface plate?

It looks like you have a nice roll around steel stand for it. Maybe you should consider making the upper gantry and side beams out of steel and then fill them with cement. It will be much stiffer and very well damped.

Overall the project is looking good.

No, the flatness is created by pouring the DWH epoxy and then lowering a reference surface onto it like a mold. Once its lifted, it 'copies' the shape. So in my case I used a large 'block' of metal which is flat as my reference. Ill find more pics of this.

Ye, the stand was a must, not only for levelling but the bottom structure is around 750kg, so not easy to handle.

I was thinking of that, easier than making another concrete structure but in the same breath, I dont want to cut corners on the design either.

Does anyone have a view on steel with concrete filled in versus a thick concrete structure?

Thanks for the comments.

[Hezz]

No, the flatness is created by pouring the DWH epoxy and then lowering a reference surface onto it like a mold. Once its lifted, it 'copies' the shape. So in my case I used a large 'block' of metal which is flat as my reference. Ill find more pics of this.

Ye, the stand was a must, not only for levelling but the bottom structure is around 750kg, so not easy to handle.

I was thinking of that, easier than making another concrete structure but in the same breath, I dont want to cut corners on the design either.

Does anyone have a view on steel with concrete filled in versus a thick concrete structure?

Thanks for the comments.

I was thinking about heavy steel members filled with the high performance concrete. Not small tubes. 6-8mm sheet steel fabricated and internally braced to the shape that you had designed. Basically, my idea was to make the mold out of reinforced steel and It would out perform the concrete unless the concrete was made at least four times bigger or so. If it's steel reinforced in the center it's even better. It is so strong and stiff they use it for earthquake reinforcement on concrete bridges. Of course, this is your project and only you know what your budget and fabrication capabilities are. I don't mean to tell you what to do. The problem as I see it is that concrete does not flex very well without failure. And you will have to make your mold very precise to get the gantry just the right width to bolt it to the base. If there is a gap and you tighten it it may well crack and fail. There just isn't much room for manufacturing error in your design. But with a monolithic steel mold weldment you would have just a little flexibility and a good surface for lapping or grinding to get flat way mounts and

Actually, I'm kind of the opinion that real heavy mass on the upper part of the gantry is not a good thing. For the base it's a good thing because it's a very rigid box type of structure, but the gantry is not and is prone to all kinds of vibration and resonance. And once this happens the mass is not in your favor. Once the gantry starts to vibrate the mass is a big problem. Stiffness and dampening and low to moderate mass I think are the most important features of a structure that is prone to vibration and resonance. The ideal gantry might be a structure that is steel skin on the outside and heavily braced with cement or EG fill near the bottom of the vertical uprights that attach to the base. But as you go up it might be better to have more bracing and a light weight sticky expanding foam or a EG constrained layer damped structure that limits the mass.

Just my two cents. I'm looking forward to what you are going to cook up for this project.

[Chazaxl]

I was thinking about heavy steel members filled with the high performance concrete. Not small tubes. 6-8mm sheet steel fabricated and internally braced to the shape that you had designed. Basically, my idea was to make the mold out of reinforced steel and It would out perform the concrete unless the concrete was made at least four times bigger or so. If it's steel reinforced in the center it's even better. It is so strong and stiff they use it for earthquake reinforcement on concrete bridges. Of course, this is your project and only you know what your budget and fabrication capabilities are. I don't mean to tell you what to do. The problem as I see it is that concrete does not flex very well without failure. And you will have to make your mold very precise to get the gantry just the right width to bolt it to the base. If there is a gap and you tighten it it may well crack and fail. There just isn't much room for manufacturing error in your design. But with a monolithic steel mold weldment you would have just a little flexibility and a good surface for lapping or grinding to get flat way mounts and

Actually, I'm kind of the opinion that real heavy mass on the upper part of the gantry is not a good thing. For the base it's a good thing because it's a very rigid box type of structure, but the gantry is not and is prone to all kinds of vibration and resonance. And once this happens the mass is not in your favor. Once the gantry starts to vibrate the mass is a big problem. Stiffness and dampening and low to moderate mass I think are the most important features of a structure that is prone to vibration and resonance. The ideal gantry might be a structure that is steel skin on the outside and heavily braced with cement or EG fill near the bottom of the vertical uprights that attach to the base. But as you go up it might be better to have more bracing and a light weight sticky expanding foam or a EG constrained layer damped structure that limits the mass.

Just my two cents. I'm looking forward to what you are going to cook up for this project.

Thanks. Appreciate the comments / input.

I am a bit limited with respect to doing 'big' steel type of work. I dont have the ability to cut and move large plates easily. That said, food for thought. The concrete gantry would be placed in place and then 'bonded' with epoxy to make up the gap to ensure that I do not 'flex' anything when using rods / bolts. I have some 100 x 100 x 5 lengths left over from the build of the metal frame, not sure if there is any benefit in trying to create an 'A' Frame (side view) from it.

[Hezz]

Thanks. Appreciate the comments / input.

I am a bit limited with respect to doing 'big' steel type of work. I dont have the ability to cut and move large plates easily. That said, food for thought. The concrete gantry would be placed in place and then 'bonded' with epoxy to make up the gap to ensure that I do not 'flex' anything when using rods / bolts. I have some 100 x 100 x 5 lengths left over from the build of the metal frame, not sure if there is any benefit in trying to create an 'A' Frame (side view) from it.

I think that there is a great benefit in building the side frames and gantry out of steel and then filling them with your concrete mix. Although I would fill the gantry with lots of bracing and expanding foam instead. If you make a kind of A-frame out of the 100 x 100 mm tubes with the thickest steel plate in the middle that you can work with you can make a system that will be a lot easier to align and be even stronger than you first intended. It can also be made to bolt to the base instead of being permenantly glued so it can be shimmed and moved forward and back and up and down a little bit.

I'll make of quick mockup to showl you the idea. But of course it is only for your consideration.

[danande]

No, the flatness is created by pouring the DWH epoxy and then lowering a reference surface onto it like a mold. Once its lifted, it 'copies' the shape. So in my case I used a large 'block' of metal which is flat as my reference. Ill find more pics of this.
Thanks for the comments.

What did you use?
Show me

[Chazaxl]

What did you use?
Show me

Sorry, been busy.

Place epoxy, (ignore the paper towel, the consistency was too liquid, but we created a dam for the epoxy). Then lower a reference surface (the 400 kg block used), let it dry, lift. The surface is not smooth (it copies the structure that leaves an imprint) but its flat.