[barum]

Steel tube walls are 1,50 mm thick and aluminium 2,00 mm. Distortion not yet noticed, but presure of oposite bears is unequal since product dimensions are with so much variablility. Bad quality. Sanding helped much.

This is for Y axis and here is how (see atachment). This is not exact match for previuos since is nut now moved to other side, but close enouugh. Looks like 3 rails on each side but realy only midle is rail while two other is short parts for orthogonal support and adjustabile fixation. Alu-profile continues down (right) to X axis which is under table. Clasics...

Drawing is in Corel Draw and mainly based on ISO262 and what I learned in highschool. I tryed in 3D studio Max but one screw thread is to complex for modeling on my PIII.




Bojan

[Kipper]

Looks nice :rainfro: I keep having different thoughts on a design to build supported-unsupported I wonder if Martin fancies working out the deflection on hot rolled 75mm sq tube with a 3mm wall? say an 8' span Here's a picture of a supported idea.

[barum]

I building my first machine. So I building it small (unsuported), cheap and easy to disassemble. Later I`ll know what`s bad about it and make it different on upgrade. It`s so tricky to build good one on first attempt. I stucked with three previous versions of linear actuators beacose wanted various complications. My idea now is to involve only cheap parts easy to find and use my simple tools. Exotic parts, maybe later when i can build it with working machine.

[kfong]

Here is mine take on the round pipe alternative. Works well for what I need it to do. Rollerbearing and aluminum angle iron.
http://www.rcgroups.com/forums/showt...41#post7469041

Kin

[technomage]

On the subject of be Bellville washers where and how would these be used?

Do you set rigid bearings on one rail then use the washer to compensate for misalignment on the twin rail?

John

Hi John
thread has moved on since my last post
But here is my take on the use of belleville Washers.

Example washers: From MSC $2.76 US for 10
http://www1.mscdirect.com/CGI/NNSRIT...44904&PMT4NO=0
Description: Belleville Disc Springs - Metric Inside Diameter: 8.2 mm Outside Diameter: 18 mm Thickness: 1 mm Overall Height: 1.4 mm Type: Belleville Material: Carbon Steel - 1074 Package Quantity: 10
Inside Diameter (mm): 8.20mm
Outside Diameter (mm): 18mm
Thickness (mm): 1.00mm
Overall Height (mm): 1.4
Type: Belleville
Material: Carbon Steel - 1074
Package Quantity: 10
Deflection (mm): 0.30
Load @ Deflection (Newtons): 1181
Load @ Flat (Newtons): 1537
Deflection To Flat (mm): 0.400
Big Book Page #: 1229

Let me start by saying where I think they can be of use.
Mainly on Twin Rail systems, by Twin rails I mean 2 Ridgid Rails pretty closely spaced together on each side of the axis and held by a Ridgid Mounting system (metal rail to metal rail with metal no wood involved the spacing and alignment of the "twins" . There may be wood or Mdf involved between the "twins" on one side and the "twins" on the other side of the axis.
My take on the use of belleville washers is with twin rails held rigidly there is 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
My apologies to Barum for butchering his Beautiful Drawing for my example(nice work BTW). The red bellevilles are the most critical IMO with the blue ones being a useful but not critical as you can see just two washers would give you .400mm give(.2mm each half of full deflection) while holding 1181 Newtons of preload (I am an inch worm so I hope my Numbers are right)
Once again I the Main use I see is Twin rail DIY machines
Industrial slides don't need "twin Rails".
I would be very interested in others comments about Master Trolley,Slave Trolley setups
Barry

[Oldmanandhistoy]

Hi John
thread has moved on since my last post
But here is my take on the use of belleville Washers.

Barry

Thank you for your time and trouble. I can see the benefits in a machine constructed in steel or aluminium and possibly in any machine using twin rails if designed to be very rigid.

I need to find the time to look at an alternative to my prototype design pictured on this thread. I will keep these washers in mind.

I would be very interested in others comments about Master Trolley,Slave Trolley setups
Barry

I would also like to hear more on this subject.

The design I prototyped using square tubes (1.5mm wall) has some obvious pitfalls due to the tubes distorting. I am considering adding steel end caps to all the tubes or trying round steel tubes inside the square tubes an already discussed. Why not move to angle iron or similar; well just because the prototype is so simple to construct. (I haven’t as yet looked at an alternative) but I am considering moving over to V bearings.

I do appreciate all the help and ideas given so far but would like to see the collective minds working together to possibly come up with the ultimate alternative to a round rail systems.

Ger21
I like your initial design very much but can see in general the rails would be over complicated for many home builders. I have to say I have the capabilities to make the rail with out problem but I would defiantly use a square steel tube in their place. I have seen no deformation in the square tubes I used for rails and this is with a very high preload. Would be interested to hear your opinions on the rails.

As for recent design ideas posted I would like to be able to comment but am unsuitably qualified to do so. It would be nice if some one who is could step in and we could all learn something.

John

[ger21]

Ger21
I like your initial design very much but can see in general the rails would be over complicated for many home builders. I have to say I have the capabilities to make the rail with out problem but I would defiantly use a square steel tube in their place. I have seen no deformation in the square tubes I used for rails and this is with a very high preload. Would be interested to hear your opinions on the rails.

IMO the square steel tube spreads the bearing mounts farther apart than I'd like. With the clipped corners on my rail design everything is more compact.

[Oldmanandhistoy]

IMO the square steel tube spreads the bearing mounts farther apart than I'd like. With the clipped corners on my rail design everything is more compact.

The one in my original pic is 1-3/4" x 2".

If this is the size of rail you will be using; a 1” square steel tube would actually make the design more compact without the need to clip the corners. That’s if I am seeing things right?
The only thing would be that the gantry side would need moving further away from the rail; but maybe not with a larger bearing on the bottom of the rail as you suggested. This would only be minimal (without actually drawing it up) so what you loose one way you gain even more the other.

John

[Kipper]

My thought is that unless you can attain extreme accuracy master/slave is the way to go (now I see where you would use the Belleville washers :cheers: ) Keep the ideas coming :yay:

[greybeard]

It's been often said that a major problem with running bearings along a round pipe is the narrow line of contact.

The advantage of going over to a box section tube could also be met by running along both faces and edge of a flat bar.
What I have in mind is to use a square edged bar of the same thickness as the bearing is wide, as any thicker would not add to spreading the load.
The assembly would be duplicated for the opposite side.
Like the first post, the bar (or bars, if two were needed) could be supported by a laminated wood structure, and otherwise follow the same ideas.


Any thoughts ?

John

[Kipper]

Looks good :thumbsup: What type of flat bar and how would it be preloaded/kept inline. It seems to be a consensus on a squared (sp) idea! I played around with your drawing a little. I think it's worth trying as it looks cheap and easy! :cheers:

[barum]

That`s the spirit.

I uploaded my last design to photo gallery,
http://www.cnczone.com/gallery/showp...0/ppuser/53018

Also, I want to show you my old idea (see attachment). It works but look sily. And thread is easy to break where deformed.

Do anyone know how to calc thicknes needed to keep distorsion under 1mm for tube say 1m long for given stress forces? What`s the math?
I`ve found some resources but this is not my area.

See why wood is bad idea, especialy plywood:
http://www.engineeringtoolbox.com/mo...ity-d_946.html



Gretings,
Bojan

[Kipper]

Take a look Here Bojan

I have to say I don't like the bent threaded rod idea

[ger21]

See why wood is bad idea, especialy plywood:

I doubt these guys would agree with that. http://www.vandamwoodcraft.com/
Some of those most stunning woodworking you'll see anwhere. Plenty strong, too. Spend some time in the galleries and you'll be impressed.

[ger21]

If this is the size of rail you will be using; a 1” square steel tube would actually make the design more compact without the need to clip the corners. That’s if I am seeing things right?

If I mount the bearings to the aluminum angle, you can't get it as close to square tubing because the corners interfere. Imo, you'd need to use a bigger tube. I've looked at square tubing in the past, and couldn't come up with anything I liked.

[martinw]

I've looked at square tubing in the past, and couldn't come up with anything I liked.

Dear All,

I think, IMVVVHO, the real problem is to find a square section that is dimensionally accurate. It could be that the accuracy of the stuff that comes out of the steel mill is the really weak link. If it is, surfaces will need to be milled true. That will not be cheap.

OK, you order 20 feet of steel, and it is delivered to you...

How careful was the guy who put it on the rig.... it could have easily bent it if the section wasn't that strong.

I guess it is a question of optimism and hope.

Best wishes

Martin

[greybeard]

Several years ago I bought "bright square edged" steel from the local steel stockholder, and it was good enough for me to build 24" slides for a small sliding saw bench without any finishing.
It was about 30mm x 5mm and I'm hoping it is still available. As soon as I can get some, and the spec, I'll post the info here.
John

[greybeard]

This morning I called in to the nearest engineering shop who quoted £20/500mm of 25mm x 5mm bright square edged flat. They sounded quite convincing when they explained that the price of steel had increased by 400% in the last 2 years.

However, even that %, plus inflation, wouldn't account for the difference in what I remember, so this pm I phoned the steel stockholder that I bought from originally, in the next town.
He would have to get it in for me as they don't hold it in stock, only plain rolled mild steel flat at £5 per 6 metre lengths.
And the price? £12 for 6 metres collected, tax included, no extra for the special order.
The spec is +/- 0.05mm on the thickness, so that will do me just fine as I'm only planning on wood working for the present.
Obviously I'm going to double check, especially on that spec.

I would use it in a vertical orientation, bolted and shimmed if necessary to a table structure, probably with two lengths either side, one above the other.

I might try with just one, depending on the section I finish up with, as he was happy for me to browse through his current stock and see what else was available to order. Sounds to be still as helpful as I remember them.

John

[spalm]

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

[Oldmanandhistoy]

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

The inside V with one bearing looks to be the most promising to me; doubling the contact area of the bearing and removing the axial load (but not if the rail arrangement is as you have them in the picture . Even with the doubling of the contact area you are still looking at a very small area. Something has to wear quickly and you would end up with an uneven rail in no time. I don’t think it is possible to use standard bearing to emulate a V bearing rail system.

Just my opinion for what it is worth,

John