Best Linear rail mounting set up

[j2sip]

Please help me choose which of these mounting positions is better. This is for a woodrouting 1200mm x 900mm x 120mm CNC.

36"(900mm) length
20mm THK Linear rails and trucks
1/2"-8 4 start Roton Acme screw
(1) 425 oz-in HobbyCNC Motors(3NM)
Luc's THB6064AH driver http://www.ecomorder.com/techref/ecomprice.asp?p=416074
44v Power supply

12789
6"(150mm) Channel bar which allows the rails to be mounted at a good 112mm apart. Very heavy. The gantry will weigh close to 80lbs(37kg). Which brings me to another question - will the above single(stepper)/drive combo move this heavy gantry reasonably?

12790
This is a 4"(100mm) channel bar with the rails positioned as shown. If I mount them(rails) like in the 6" channel bar, a mere 56mm separates them. 10 to 12lbs lighter that the first.

Thank you in advance for your answers.

Jordan

[j2sip]

12830
This is my design if it helps. The 36kg gantry is my main concern but joescnc2006 over at the other forum has run his 35kg gantry with 1.2nm motors and 1/2" 10 acme screws.

Thanks!

[JAZZCNC]

Both setups would work perfectly fine as these rails are designed to work in both those positions carrying much more load, 36Kg is nothing, these rails won't even know they are carrying 36Kg.

[j2sip]

Both setups would work perfectly fine as these rails are designed to work in both those positions carrying much more load, 36Kg is nothing, these rails won't even know they are carrying 36Kg.

Thank you so much for the reply. Good to know they're more than enough for the job. But one of my concern now is can the combination of screw/motor/driver drive that heavy gantry? I believe 5mm is the equivalent lead of the acme screw.

[JAZZCNC]

Thank you so much for the reply. Good to know they're more than enough for the job. But one of my concern now is can the combination of screw/motor/driver drive that heavy gantry? I believe 5mm is the equivalent lead of the acme screw.

Don't worry 36Kg isn't heavy at all for a gantry and those motors will move it no problem. If the screw is 8 turns per inch The lead of the screw is 3.175mm but you have 4 starts so that is 3.175 x 4 =12.7mm or 1/2" pitch. This is a nice pitch for a wood router and will give rapids in the region of 10Mtr/min. (390in/min) or above.
You'll rarely cut at this speed so will have more than enough torque when cutting.

[j2sip]

Don't worry 36Kg isn't heavy at all for a gantry and those motors will move it no problem. If the screw is 8 turns per inch The lead of the screw is 3.175mm but you have 4 starts so that is 3.175 x 4 =12.7mm or 1/2" pitch. This is a nice pitch for a wood router and will give rapids in the region of 10Mtr/min. (390in/min) or above.
You'll rarely cut at this speed so will have more than enough torque when cutting.

Haha looks like I messed up the conversion. My old cnc moves that fast but with 2 gantry motors and a lightweight gantry. This http://www.elab.ph/forum/index.php?topic=35151.100. Sorry mostly in our language. Cheap used linear rails started popping out in the local market so I thought of another upgrade. Well, thank you so much for your input. I'll post pictures as soon as I commence building again.

Jordan