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Darren_T
10-10-2003, 06:42 PM
I've been fiddling with some sketches of ideas for using the roller blade bearings in a slightly different way. I didn't want to have to machine any parts other than what I could accomplish with my woodshop tablesaw, bandsaw, and drill press.

Here is a sketch of what I came up with. Anyone see any problems with this design. It's just a sketch slightly to scale but not perfect by any means. It's just for concept.

I imagine the stock to be sheet aluminum either 3/8" or 1/2". The drawing shows 1/2". The top bearings are mounted at 45 degrees and the bottom bearing is on a sort of swing arm that is tensioned with two through bolts.

http://thomaswoodcraft.com/bearings.gif

HuFlungDung
10-10-2003, 06:58 PM
Hi Darren,

I like it pretty well actually. All the wheels should touch no matter what (within reason :) ) You should also be able to nicely regulate the preload of the trolley so it will roll just right.

Go for it.

deft
10-10-2003, 07:06 PM
I've been thinking about the same problem.

I like your through bolt tightening system.

I think you would need to use 1/2" thick stock.

Cutting the miters on a table saw doesn't sound like fun...

if and when I get around to making a machine I'm probably going to use a variation of this method (see link)


http://members.shaw.ca/axxus/m1.htm

The hardest part would be drilling the holes 60 degrees apart and finding the right channel... The slots in the tube aren't critical so they could be drilled out and then filed...

Darren_T
10-10-2003, 07:09 PM
Oooohhh. I like that Deft. It looks quite a bit easier than my plan too. I'll probably have to give both a try :)

Darren

sol
10-10-2003, 11:21 PM
Good!... getting about putting pencil to paper; it is a start! My experience with a similar prototype that I made (and dismantled) was...having the tensioning bearing in the center between the other bearing-sets allowed a fair amount of rocking of the axis. When the bottom bearing was tightened to the rail enough to remove all of the play the bearings were loaded too tightly to roll smoothly. I then put the bearings all in the same plane or cross section and everything tightened up nicely. The result has been an X axis that rolls very smoothly with virtually no slop...all made on the cheap. Enclosed is an image of the bearing set I welded up and yeah, it is not of aluminum but I thought the cam tensioning system (a rod threaded off-center into the head of a bolt) was worth the show and tell. Oh yeah... and I left the bottom, rather than a side, open so that gravity was my friend when it came to loading the whole rig onto the rails.

Hope this helps!
Sol

ehiebert
10-11-2003, 01:40 AM
I'm just curious why everyone is choosing the more complicated moving gantry designs over the moving table designs? Is space saving worth that much extra effort??



Eldon.

High Seas
10-11-2003, 07:12 AM
I was wondering the same thing! Don't suppose its always been that way? :stickpoke

I expect the trade off (excepting floorspace) comes when gantry weight exceeds project weight! Is that why most vertical mills have moving tables? Or because they evolved from a drill-press approach? I don't know - I'm new to all this!

The gantrys I've seen, all have large endplates designed to elminate any "wiggle" :banana: as the gantry moves along the x axis. And, at least one member of the 'zone added cross members to his gantry to elminate wiggle along the y-axis.

Earlier a reference to a cnc router offered on ebay showed an approach, between moving table and gantry. The gantry moves but the rails for the x aixs are more or less "in-plane" with the y axis on the gantry. That seems like it could elminate some potential for "wiggle" - and still conserve floor space.

I'm trying out a similar plan in mine - I'll let you know how it goes.
:cheers: Jim

ger21
10-11-2003, 08:20 AM
Mines 5ft long, with 4 ft of travel, so yes, saving space is very important.

Gerry

ger21
10-11-2003, 08:25 AM
Take a look at my design here

http://cnczone.com/showthread.php?s=&threadid=1356

It can all be done with a table saw and drill press and is very strong and smooth rolling. I built a wall mounted panel saw with the same basic design which has been working great for the last 8 years.

Gerry

tekno
08-09-2004, 07:56 PM
Take a look at my design here

http://cnczone.com/showthread.php?s=&threadid=1356

It can all be done with a table saw and drill press and is very strong and smooth rolling. I built a wall mounted panel saw with the same basic design which has been working great for the last 8 years.

Gerry

was doing a search and found this tread.. would like to see more but we have a :stickpoke link error. can someone help me out?

jeffs555
08-10-2004, 03:27 AM
http://cnczone.com/forums/showthread.php?s=&threadid=1356

I have found that on a lot of the old links you have to add the /forums/ between cnczone.com and showthread.

wjbzone
08-10-2004, 07:12 AM
I stayed with the fixed table because I did not want to limit myself on the workpiece length or weight. I've worked on the end of some long boards where I had to support the opposite end off the table.
Bill

mvaughn
08-10-2004, 11:30 AM
was doing a search and found this tread.. would like to see more but we have a :stickpoke link error. can someone help me out?

Try this link

http://www.cnczone.com/forums/showthread.php?t=1356

charleyy
08-14-2004, 08:53 PM
CNC-sters -

in my googling of roller blade bearing sets, i ran across quite a range of them, from a dollar or so a piece, to sets of 4 or 8 for 30-40-50 bucks... (to be used for john conrad kleinbauer's 7th sojourn design (modified)...)

being a rank newbie, i don't know if the cheapest (roughest?) set of bearings is just as good as the most expensive ABEC 7, zirconium oxide super duper bearings, *for the purposes* of a hobby cnc machine intended to machine wood...

i wouldn't mind splurging on the more expensive and/or 'ceramic' bearings, *if* i thought they would make a significant difference for my application...

opinions regarding the level of quality needed would be appreciated...

thanks, charley
charleyy@alltel.net

eof

gtrdude
08-14-2004, 10:15 PM
Hi there, great idea with the 3 bearing design. I've been thinking about a 3 bearing roller setup myself but you beat me to it! Hopefully you've saved me some work :)

My question here is what are people using as slides with the roller bearing design? I am building a setup that is 850mm long. I've been thinking of using stainless tube that you buy from the hardware store for hanging your towels on in the bathroom. These should be very smooth and straight, and pretty cheap. The only thing I wonder about is if it is rigid enough. It would need to be able to withstand a reasonable amount of force to prevent error. Especially in the middle of its run.

Another possibility is that to increase the rigiditiy you could insert some thick threaded rod inside the tube if it was the correct fit with a bolt on either end.

Is this a stupid idea? Am I on the wrong track? Give me your thoughts!

Paul

ger21
08-15-2004, 10:06 AM
CNC-sters -

in my googling of roller blade bearing sets, i ran across quite a range of them, from a dollar or so a piece, to sets of 4 or 8 for 30-40-50 bucks... (to be used for john conrad kleinbauer's 7th sojourn design (modified)...)

being a rank newbie, i don't know if the cheapest (roughest?) set of bearings is just as good as the most expensive ABEC 7, zirconium oxide super duper bearings, *for the purposes* of a hobby cnc machine intended to machine wood...

i wouldn't mind splurging on the more expensive and/or 'ceramic' bearings, *if* i thought they would make a significant difference for my application...

opinions regarding the level of quality needed would be appreciated...

thanks, charley
charleyy@alltel.net

eof

You can get ABEC 7 bearings on Ebay for very reasonable prices. Don't buy any until you check there.

jeffs555
08-16-2004, 02:41 AM
Paul,
Putting a threaded rod in the center of a tube won't increase the rigidity much. If the tube isn't rigid enough, then going up in diameter will be more effective than using a solid rod. For example, a steel tube of 1-1/8" diameter with 1/8"walls is more rigid than a 1" diameter solid steel rod. Here is an easy to use freeware program that will calculate the deflection given the rod size and load.
http://www.pcworlddownload.com/business/project-management/BeamBoy.htm


Jeff

gtrdude
08-16-2004, 02:59 AM
Paul,
Putting a threaded rod in the center of a tube won't increase the rigidity much. If the tube isn't rigid enough, then going up in diameter will be more effective than using a solid rod. For example, a steel tube of 1-1/8" diameter with 1/8"walls is more rigid than a 1" diameter solid steel rod. Here is an easy to use freeware program that will calculate the deflection given the rod size and load.
http://www.pcworlddownload.com/business/project-management/BeamBoy.htm


Jeff

That's great information Jeff! Thanks for the response. I'll try the software.

sol
09-04-2004, 10:21 PM
...the 3 bearing design. I've been thinking about a 3 bearing roller setup myself ....
... what are people using as slides with the roller bearing design? .... I've been thinking of using stainless tube that you buy from the hardware store .... should be very smooth and straight, and pretty cheap. The only thing I wonder about is if it is rigid enough. ..... Especially in the middle of its run.

Give me your thoughts!

Paul

Regarding cheap track and bearings:
Here is another version of a bearing set that I made; this time out of aluminum so no welding is required. Their tension is easily adjustable and they're durable. Also they are open on the bottom which allows for the pipe track to be supported. Details have been posted in other threads and are also on my website...
The pipe support is a piece of channel; the pipe is bolted through the channel to the primary support. Seems to work well enough; especially considering the price....