Gantry Concept

[Jkountz]

Well Ive been working for some time on a new gantry design based on V bearings and rails since they seem to be cheaper than linear rails and bearings. If you have ever been over to the Mechmate forums then you know those guys have a very easy and effective way to grind your own v rails. I will be following their example for this build.
What I DONT know is how V bearings support loads side to side. I have attached some pics here of what I have in mind. Everything is all 3/8" thick aluminum construction. If you can see the orientation of the V bearings Im wondering if this will properly support the Z car. Being its aluminum I dont think the overall weight would exceed 20 lbs at the very most, router and all. For those with any experience with V bearings take a look and see what you think.
All comments and suggestions are very much welcome and needed!!

Thanks!!

Jim

[ger21]

Go to http://www.bwc.com/ and download there Dual V catalog. It has radial and axial load ratings for their different size bearings, as well as formulas for calculating the loads.

In post #29 of the thread on the router I'm currently designing, I calculated the loads for a similar design. http://www.cnczone.com/forums/showthread.php?t=45844

Also, your 20lbs is probably low by at least half. Most routers are about 8lbs, your Z axis rails will be about the same, 4 lbs for a stepper... I think you'll be closer to 40 lbs.

[Jkountz]

Gerry you're probably right about the weight calculation, when I posted that I was thinking only of the z-car itself since it will be whats pulling or pushing on the v-bearings. I guess one would have to take into account the entire load though, thanks for pointing that out. Aside from that whats your take on the design? Sink swim??

[ger21]

If you look at my thread, it's a lot like mine. Only mine will be made of wood.

[Jkountz]

Well after reading your post and doing some initial calculations it seems I should be good to go with the load on the v-bearings. I was looking over the machine youre designing, looks great!! Did you look into making your own v track like the Mechmate folks do? Whats your thoughts on that?

[ger21]

I plan on making my own, but not by grinding. My plan is to epoxy some steel square stock into a groove routed into a wood rail. I need to build a prototype to see if it'll be strong enough, though. But I think it'll work. Grinding is too messy for me, but if you get one of those grinder shoes the Mechmate guys use, it appears to work very well.

[arizonavideo]

Originally Posted by ger21 Grinding is too messy for me, but if you get one of those grinder shoes the Mechmate guys use, it appears to work very well.

You do know you are building a milling machine that will produce many pounds of fluffy stuff and strange kinds of dust. If given the chance it will project chips in places you would never think they could go.

[ger21]

You do know you are building a milling machine that will produce many pounds of fluffy stuff and strange kinds of dust. If given the chance it will project chips in places you would never think they could go.

I already have one, and filled two large garbage bags with dust last weekend with it. The dust goes right where I want it to go, in the dust collector. And sawdust is a lot different from metal grinding dust.