[ivojnob]

What ever your gantry sides are made of, they look like a weak point. Are you using hardwood? Whatever it is, it need to be thicker than the 3/4" it appears to be. Especially where the top carriage is bolted to it.

Thanks for the feedback. Yeah, that's the part that I'm struggling with. The way the pinion has to line up with the rack means I have a particular thickness I can use to join the upper and lower carriages if the R&P drive is going to mount to the outside as shown in the pictures. In this case it's 5/8", so I can either do hardwood, plywood or MDF. I want to thicken the gantry sides above the top carriage as much as possible (like I've shown, but maybe all the way to the inside edge of the top carriage) and bolt the thickened gantry sides to the top of the carriage in addition to the side. I could do 5/8" aluminum for the sides if I have to. I wonder though if that would be stiffer than having the sides be 2-1/2" thick from the top of the carriage to the bottom of the main gantry beam. I still haven't thought much about the connection between the gantry sides and beam.

I was originally thinking of doing something like this older screenshot I made, but I read a comment that said it's better to have the gantry overhang the sides so that the carriage bearings aren't pulled out of line with the 1/4" rails...

[ivojnob]

This picture is a better shot of what I was planning for the gantry sides, although the gantry was just slapped together at this stage.

Notice how the sides have been thickened above the top carriage and extend to the front of the carriage. I still have concerns about the 5/8" thick piece that connects the upper and lower carriages especially with the cutout that I have to make to accommodate the R&P belt drive. If there's any merit at all to this design, maybe I need to consider extending the part between the two carriages further forward so that the hole for the belt drive is in the middle of the part (i.e. the wood is closed at the front instead of the open "birds mouth" that I've shown here)

[SPEEDRE]

May I suggest, that you over build the gantry support beam and laminate it from 5/8 th's AAA baltic birch plywood, with 3/4 in maple substrate. And the side members that connect the beam to the linear unit be wider on those members as, this, is the weakest point of the whole unit. I believe this will help eliminate all the annoying flex and slop of this design.

[ivojnob]

May I suggest, that you over build the gantry support beam and laminate it from 5/8 th's AAA baltic birch plywood, with 3/4 in maple substrate. And the side members that connect the beam to the linear unit be wider on those members as, this, is the weakest point of the whole unit. I believe this will help eliminate all the annoying flex and slop of this design.

Not sure I follow. Are you suggesting I make the gantry support beam out of laminations of wood all going in the same direction as opposed to building it like a long, thin box?