@uncle_bob:
1) I suspect it will be stiff enough. I am considering doubling up the plate as a backup plan. However, the top and bottom plates will probably give me the rigidity I need and the mid plate only needs to register the screws in the xy direction.
2) The shoulders do get zeroed against the top plate. (I am probably close to my limit of squeezing out more build volume in the z direction. The drop plate was more for leveling and just had the side benefit of adding to the volume.)
3) Good idea. I also am considering the making the nut holder for the top reach over the side to hold it in place. That way I only have to turn the bottom one. However, those wingnuts don't cause any clearance issues. :-) You would think that they do but I check and double checked.
4) I am at my near optimum. (I use the whole length of the screws.) The only way I can get more range at this point is to bring the screws closer together and redesign the hub so that the hot end can come within 25mm of the screws. This will shorten the arms which in turn will give us more z height. I did a quick run through on that design direction and if I change the screw spacing from 300mm to 250mm it will shorten the arms to 150mm. It will also add 50mm in the z direction of the build column and will reduce the footprint to a 350mm circle. To give you a feel for the size, it will just barely cover a 8.5"x11" piece of paper.
So, I will change the wingnuts on the top to something that just holds the bolt and hooks onto the side. I will also experiment with decreasing the screw spacing. I haven't done so yet because I have been reusing GUS Simpson's hub but it might be time to diverge.
Note: I also looked at changing my columns from 2" PVC (2.375" in real life) to 1.5" PVC (1.9" in real life) and I only shaved off 30mm from my footprint. To me I don't think it is worth that change.
1) I suspect it will be stiff enough. I am considering doubling up the plate as a backup plan. However, the top and bottom plates will probably give me the rigidity I need and the mid plate only needs to register the screws in the xy direction.
2) The shoulders do get zeroed against the top plate. (I am probably close to my limit of squeezing out more build volume in the z direction. The drop plate was more for leveling and just had the side benefit of adding to the volume.)
3) Good idea. I also am considering the making the nut holder for the top reach over the side to hold it in place. That way I only have to turn the bottom one. However, those wingnuts don't cause any clearance issues. :-) You would think that they do but I check and double checked.
4) I am at my near optimum. (I use the whole length of the screws.) The only way I can get more range at this point is to bring the screws closer together and redesign the hub so that the hot end can come within 25mm of the screws. This will shorten the arms which in turn will give us more z height. I did a quick run through on that design direction and if I change the screw spacing from 300mm to 250mm it will shorten the arms to 150mm. It will also add 50mm in the z direction of the build column and will reduce the footprint to a 350mm circle. To give you a feel for the size, it will just barely cover a 8.5"x11" piece of paper.
So, I will change the wingnuts on the top to something that just holds the bolt and hooks onto the side. I will also experiment with decreasing the screw spacing. I haven't done so yet because I have been reusing GUS Simpson's hub but it might be time to diverge.
Note: I also looked at changing my columns from 2" PVC (2.375" in real life) to 1.5" PVC (1.9" in real life) and I only shaved off 30mm from my footprint. To me I don't think it is worth that change.