[greybeard]

If you only have one bearing on the lower angle, why use the angle ?
Would a simple flat perform in the same way, if not better ?
I suspect I'm missing something here, so could you spell it out gently please

Regards
John

Edit Sorry. Thanks to John getting in ahead of me I now realize the angle at the top could be turned upside down to become the alternative arrangement. I thought you were referring to the bottom rail. (chair)

[spalm]

OK OK
I know it looks bad.

(sorry about the incomplete pictures, I only had so much time last night)

How about using three rails? The top one is flat steel on wood with the bearing in full contact. This would be the master fixed parallel rail and take most of the pressure. The other two adjustable rails would be as in the Pics with slight preload so as not to grove the angle and mostly perform the alignment holding.

Steve

[Oldmanandhistoy]

OK OK
I know it looks bad.

(sorry about the incomplete pictures, I only had so much time last night)

How about using three rails? The top one is flat steel on wood with the bearing in full contact. This would be the master fixed parallel rail and take most of the pressure. The other two adjustable rails would be as in the Pics with slight preload so as not to grove the angle and mostly perform the alignment holding.

Steve

Multiple parts and axial loads?

John

[spalm]

Touche

OK two rails. Top one is flat, bottom is inverted V. The top one carries most of the weight. The bottom one is adjusted with preload to keep alignment. This is basically how I have my gantry right now (even without the box across the bottom) except I have the V on top and flat on the bottom.

I see very little axial load (axial load is like a lazy Susan).

Steve

[Oldmanandhistoy]

Touche

OK two rails. Top one is flat, bottom is inverted V. The top one carries most of the weight. The bottom one is adjusted with preload to keep alignment. This is basically how I have my gantry right now (even without the box across the bottom) except I have the V on top and flat on the bottom.

I see very little axial load (axial load is like a lazy Susan).

Steve

Axial loads will come from side pressure on the rail I would have thought?

Whats a lazy Susan?

John

[spalm]

Sorry, a lazy Susan is that tray that sits in the middle of a table and can spin around so everyone may reach the food.

Yes you are right, sideways pressure is axial. I have been told in a situation like this about 80% of the pressure will be radial and about 20% axial (or less). That is why the real V-bearings are angular contact with angle set up for about this amount of distribution.

Someone who knows this stuff is going to cream me

Steve

[Kipper]

Sorry, a lazy Susan is that tray that sits in the middle of a table and can spin around so everyone may reach the food.

Yes you are right, sideways pressure is axial. I have been told in a situation like this about 80% of the pressure will be radial and about 20% axial (or less). That is why the real V-bearings are angular contact with angle set up for about this amount of distribution.

Someone who knows this stuff is going to cream me

Steve

45° is still 45° so the bearing is running (internally) on 45% of it's normal race area (maybe I'll be creamed soon ) I thought/assumed that the "bought in" V rollers used ordinary radial bearings and a machined outer? I did however know what a lazy Susan is....It's my sister in law :yes:

[Kipper]

I have turned into a V-bearing convert for a medium cost (non-eBay) solution. I can understand trying to keep costs down for other builds, but that seems to come with either added complexity or allowing more flex into the system. There will be no prefect model coming out of this discussion, but rather several good ones that will meet a builder’s pocketbook and ability to build it.

How about a homemade V solution? I know that the rails are too soft and this is a naughty thing to do to bearings, but I really feel that the simplicity and adjustability of such a design should be pursued, and you can not get much cheaper or easier to build. It will hold a truck from moving in any direction except the one you want and has fully supported rails.

It requires two rails. One of the rails is fixed and parallel to the direction that you want to move. The other rail is loose (oversized holes) until preload is applied and then tightened down. Preload is accomplished by spreading the rails apart with removable spreader bolt thingies.

1/2” angle iron is used either pointing up with two bearings for an outside V, or pointing down with one bearing for an inside V. I used a V-router bit to do the bevel on the wood to hold it. The angle is attached with a dab of glue or double sticky tape. This small size of angle allows the use of nuts to hold the bearings without touching the angle and allows the truck to be closely attached to the rails.

I hope to build a couple versions of this thing and do some stress testing soon.

Steve

I don't like it :shrug: It just seems wrong.

[ger21]

I have turned into a V-bearing convert for a medium cost (non-eBay) solution. I can understand trying to keep costs down for other builds, but that seems to come with either added complexity or allowing more flex into the system. There will be no prefect model coming out of this discussion, but rather several good ones that will meet a builder’s pocketbook and ability to build it.

Here's a machine I linked to back in post #26.
http://www.cnczone.com/forums/showthread.php?t=33124


16 V rollers + 8 eccentric bushing = $216

It's a lot easier to build, and it's a proven design. Not sure how well the steel angle will hold up, but it's really cheap. Minimal hardware required, cost of which can really add up fast, too. Especially on some of the designs I've seen posted in this thread.

Actually, this design is cheaper than the Z-axis on my current machine, which I really like and planned on using again. Linear shafts and ball bushings.


Looks like this may be the way to go, provided the angle holds up.

[spalm]

Gerry, I hear ya.
I was just trying to find some way to do it on the cheap and thought I would inject a new approach. I kind of knew it was not going to be an easy sell.

I really like his machine. I wish I had run on the edge instead of the end of the angle iron. Seems like stainless might help a lot. I just found 3/4” stainless for $11 for 4 feet at:
http://www.speedymetals.com/pc-1690-...d-pickled.aspx

Funny you mentioned your Z. I just received another set of V-bearings today in the mail and two 1 foot sections of the real rail for the rebuild of my Z. I could not come up with a cheaper solution. I do not like how I am running brass bushings on shafts. They have a lot of slop. So I will post when I get going on it.

Steve

[Jason Marsha]

This is not a V-bearing idea but it seems to work pretty well.


Jason

[barum]

This is not a V-bearing idea but it seems to work pretty well.

Jason

Looks like ultimative X axis but maybe too heavy for upper axes. I have similar solution and used "Square Hollow Sections" instead of full metal.

Did you noticed ...

... spots where critical distances exist with no "give" you either have to err on the loose side or take a chance on jamming or racking...

Bojan

[tiwanacote]

What about TURCITE? Do any one know about this plastic used for linear guides???

[Oldmanandhistoy]

What about TURCITE? Do any one know about this plastic used for linear guides???

More information.

http://www.aetnaplastics.com/ws-turcite.htm

http://www.professionalplastics.com/...nt/Turcite.pdf

John

[barum]

Turcite... interesting! Looks like teflon for mouse pads.

[greybeard]

John - do you happen to know if that Turcite is available in UK ?

other John

[Oldmanandhistoy]

John - do you happen to know if that Turcite is available in UK ?

other John

Hi John,

I just googled for the information; It is aka Symalit® if you do a UK google you should get a few hits that may lead to a supplier.
Looks interesting I have had a quick look here http://www.symalit.com/Fluoroplastic...h/idsym021.htm but have not investigated if it is available in small quantities. I would like to have more time myself to find out if this would make a good linear slide. If you find a supplier and investigate this further could you post here?

John

[greybeard]

Will do.
I also wondered if those small blue discs sold as furniture glides were a similar/same material?

other John

1st hit - www.goodfellow.com with a stockist in Cambridge.
More info when I get it.

[barum]

I just found many other plastics for bearing and wear:

http://www.professionalplastics.com/...r/19/sesent/00

they have sales support in UK.

[thkoutsidthebox]

Im not sure that two flat pieces of plastic rubbing against each other, no matter how well they slide initially, will give enough allowance for dust and grit over time. Even if they can initially slide over the dust, or push it ahead of them, I think eventually they will become ground down rough and no longer be flat smooth surfaces....just a thought...
Perhaps a flat metal piece and a flat sliding plastic piece, the plastic piece being sacrificial and replacable after intervals of one or two months depending upon machine useage.