Help with gantry design

[robe_uk]

Hi all,
I am thinking about my next router build which i plan to loosely base on the joe hybrid, although i have been able to obtain supported linear rails cheaply(read free )
I have attached a picture of the two possible ways i could mount them to the gantry, please have a look and feel free to give your option on the pros and cons of each.

Thanks
Rob

ps: just thought what about mount the top rail on top and the bottom rail on the side, like combine the two methods?

[rlwoodjr]

Originally Posted by robe_uk Hi all, I am thinking about my next router build which i plan to loosely base on the joe hybrid, although i have been able to obtain supported linear rails cheaply(read free ) I have attached a picture of the two possible ways i could mount them to the gantry, please have a look and feel free to give your option on the pros and cons of each. Thanks Rob ps: just thought what about mount the top rail on top and the bottom rail on the side, like combine the two methods?

#1 would be my vote. Further apart will give less force in the 'A' moment (rotation around the x axis) and it is closer to the gantry which is less 'B' moment (rotation around the y axis).

[AccurateCalibra]

Originally Posted by rlwoodjr #1 would be my vote. Further apart will give less force in the 'A' moment (rotation around the x axis) and it is closer to the gantry which is less 'B' moment (rotation around the y axis).

X2

[mkc2]

Have just upgraded to linear guides, I think this is what your after.
Hope this helps.

Cheers
Michael

[robe_uk]

Thanks for the replies,

Michael, thats a nice clean setup you have.

I would like to use aluminium extrusion for the gantry but I have yet to find reasonably priced parts here in the UK, but i guess its all relative to what am willing to pay, (on the run up to christmas not much)
I have thought about making up a gantry using 18mm mdf to form a sort of box section. I've had a go on google sketchup (just downloaded this morning) to give an idea of my thoughts, what is not shown is any internal webs i might add.
Not sure how strong it would be in regards to flex/twist.
The span is 80cm and the router will have twin leadscrews on the x-axis so no racking, still have to come up with the gantry side supports.

Again comments welcome.

Thanks rob

[CarveOne]

If it is glued together with yellow carpenters glue (aliphatic resin glue, such as Titebond, Elmers, etc) and screws, and you install a few close fitting rectangular blocks inside, I doubt that you will have any serious twisting or bending problems.

Beats trying to build it with "Unobtainium extrusions".

CarveOne

[johnmac]

I built mine like mkc2. It gets the rails farther apart for more stability without making the gantry look big and heavy.

John