Cheap Linear Bearing Holy Grail?

[vacpress]

After reading ynneb's post about his $600s for 12 Wisecarver bearings, i had an idea. this is it:

[vacpress]

The text is to small to read. basically this idea uses regualr roller bearings and a very simple machined part to achieve the capability of the grossly prices wisecarver system. Anyone know why this idea hasnt been explored before? Alot of the people out here have lathes.... this would be a very easy product to make $$$ off of also.. sell it on ebay as "bishop wisecarver alternative"

1 48" rail & 2 shuttles can be built for $50 or less. probably less.

another picture:

[vacpress]

One last iamge - this one only uses 1 bearing, and looks most like the wisecarver. either a good pressfit, or somesort of ocking rings would be required with this design. probably both. Then. im no machinist. Any ideas why this isnt done? Why are wisecarvers so expensive?

[ynneb]

Hey Vac, funny you should post about this. Tonight I was showing a friend the bearings and he said, why didnt I just bolt two bearings together with a washer seperating them. Now I feel sick.

I dont know how the bearings would wear with the force on the side pushing them apart though.

Yes I did think of your idea too, but dont have a lathe to make the wheels. I could have almost bought a lathe at those costs though, and I would have got to keep the lathe. You see this is why the forum is so good, others can learn from others mistakes.

Oh and just remember you are quoting Aussie dollars and not US dollars. US dollars would be about $500 for the same thing. Just been pedantic to make myself not feel so bad. Truthfully I am still happy I didnt pay much more for proper linear bearings though.

EDIT: Your design is better than the bearings I bought, not only because it is cheaper but because the load is spread over two bearings and not one.

[vacpress]

well. to really not feel bad, consider this: there is no way $8 of rollerblade bearings can beat precision made linear components. They may come close for many practical applications. But you have some parts designed for what you want them for: providing movement for a production quality machine. i hope your machine build lives upto the components. they look like they need a very sturdy rail to ride on.

I am about to investigate if their is a potential product idea here. i could sell these things to hobbiests for some reasonable cost. they can make the rail from cheap steel.... hopefully...

dont worry ynneb, you get what you pay for many times - especially with high quality motion components.

[ger21]

Benny, did you buy those direct? From Bishop Wisecarvers online order pages, I can get #2 size wheels for $21.88 each, and 10ft lengths of track for $75 each. 12 wheels would be $262.56. And these can carry loads over 500lb, so there is no need to get the larger, more expensive ones. Just curious why you had to pay so much. Could be the Australia thing, I guess.

[Konstantin]

While vacpress design look nice and makes it feel like it would be easy there are lots of dificulties on actualy making them, the precision is on of them. Also the small problem of a late, archiving exact same dimentions on all linear bearings, hadren the steel. It is way cheaper to buy a precision machined linear guides/bearings than making it oneself (speaking for regular people).

Beny you cannot use radial bearings with axial loads, they will wear way too fast. I didnt knew that bearings are so darn complex until I read a document describing a spingle design, so many variables to consider, the axial and radial loads, speeds, lubrication, temperature.

[pminmo]

I too have had a similar idea, and wished somebody would start offereing the parts. I don't think BWC's rail is unreasonable, it may even be a bargain.

Phil

[HuFlungDung]

I kind of agree with Konstantin. Sometimes, its the details that kill what seems like an otherwise good idea

Running the V wheels on the sharp or unmachined corners of standard flat stock is not going to make a good raceway, because there would be an initial state of high wear on both the soft wheel and on the raceway itself. So right away, we get into having to chamfer both sides of the flat bar, and keep every chamfering cut parallel. This task requires a lot of care and attention to achieve.

Then, eccentric studbolts would be required in both wheels on one side, so that the gap can be properly adjusted. While doing this is not difficult, it is not just a plain old bolt.

As Konstantin said, machining your own V wheel flange is conceivable, it is still expensive and troublesome to do properly. Hardening and then subsequent hard-turning of the wheel would be required. The tolerance for error on the wheel is zero runout. The tolerance for lateral displacement of the V in the wheel flange is also zero, or this will cause tilting of the truck. Just try actually defining the position of a V groove in a cylindrical surface sometime. Its one thing on paper, but a whole different thing on the lathe.

[vacpress]

so evne the guys who make the little motors couldnt use this idea? boohoo. what about cnc lathe on Stainless, would that lower the price?

as for loads.. are the wisecarvers designed to take the load on their axle like that?

what about how wisecarvers are used on the shopbot? no special rail there...

is hardening absolutely needed? can some other combonation of materials be used.. like delrin bearing flanges? or copper? or something? annodized aluminum?

[ger21]

The B-W rollers I listed the price above are rated over 500lbs. for both axial and radial loads. And the rail is hardened.

I just looked at the shopbot site but couldn't really find any info there.

[HuFlungDung]

Stainless is not inherently hard at all. So it is not a "natural" choice for a rail, either.

Anodized aluminum is only hard for .0002" depth, and this is easily scratched because there is nothing hard underneath, backing up the anodized surface.

Using an easily available piece of C1018 cold drawn square stock still makes the best choice for a quick track for a V groove wheel. Its not hard, but its not expensive, and it is accurate, if you are selective about the piece you purchase, to try to make sure it is straight. The larger the cross section, the more likely it will arrive in a straight condition. However, this requires a bit more imagination to devise support blocks for holding square stock in the "diamond configuration". If it is a small machine, likely the bar can simply be mounted and held by a axial bolthole drilled down each end of the rail.