[Jimmy Southern]

Hey again Dieguy,

Sorry for the all negatives on that last post. I had a customer to come in and lost my train of thought. Like I said before I really like the square idea. I was going to do pros & cons on the last post. Seems I only got the cons written down. Well here are the pros:

1. Depending on the size of the tube & clearance, we could stack several bearings on the shaft. This would give more surface contact. Thus eleminating tracks being worn in the tube and the need to rotate the round pipe. I really like this part!

2. Ease of alignment. If the tubing has been carefully installed and you have eccentric bolts on the trucks, alignment should be a breeze. No need to shim the bearings to get them dead center of the radius. I really like this also!

3. Strength: I have done a bit of research into the strengths and weaknesses of the round versus square. In this instance the square offers a bit more resistance to flex, but not much.

My conclusion is: If the fit can be made simple enough, this should be the best way to go. One glitch that we have failed to cover though is: this material is not available at most hardware centers.

So I will leave the reccomendations to the rest of the team. I personnally like it but may not suit the hardware plans because of availability.

Let us know, ESPECIALLY those that are in "hard to get" areas.

This is just my opinion though!
Jimmy

[izzlestar]

Hey guys, I'm a long-time lurker. I've been following this thread, its great... the creativity is awsome! Anyways I thought the square tubing was a really cool idea, and I thought of this: using angle iron instead of the square tubing. I drew a quick drawing in rhino to illustrate what I mean. I'ts crude, but It illustrates how simple it makes building the ribs of the torsion box. Thanks -Carl

[spalm]

izzlestar, welcome!

I plan to give the square channel a try. After pushing, pulling, and yanking my small pipe machine, I have noticed two things that I do not like. Although, hey, it’s MDF and pipe, and it ain’t all that bad.

#1) the carriage can roll forward. When I first tested it with a 30 pound weight hanging from the front, I discovered that the carriage was too weak. I rebuilt it with wrap around sides and am very happy with the strength. I was delighted that the bearing adjusters could bring it back into level with or without the weight. I dropped any further testing. I am a harsher critic now and can detect this roll by pulling and pushing on it. I cranked on the bearing adjusters until the motor stalled, and then backed them off a half turn. Pretty much solved the problem, but I am not sure I like that much pressure. So I just bought some 3/4” square channel at Home Depot (small I know, but it is very close to the 1/2” pipe that I am using). I plan to make a box to support it and report back This problem will rear it self more on small pipe, but if we can nail it there……..

#2) the gantry right side can move back and forth while the left is held ridged with the left mounted leadscrew. I have mentioned this before, but I spent some time last night watching it. Increased bearing pressure did not really help, but increased tightness on the two torsion box’s attachment bolts did. So what I plan to try is to move the leadscrew to the bottom center. To do this I need to build a new bottom torsion box, so I plan to make it stronger and increase the length of the top skin so it will fit into dados in the gantry walls. Maybe replace the T-nuts with threaded rod running all the way through. Again, larger boxes will help this problem.

Steve

[DieGuy]

Hey again Dieguy,



My conclusion is: If the fit can be made simple enough, this should be the best way to go. One glitch that we have failed to cover though is: this material is not available at most hardware centers.

So I will leave the reccomendations to the rest of the team. I personnally like it but may not suit the hardware plans because of availability.

Let us know, ESPECIALLY those that are in "hard to get" areas.

This is just my opinion though!
Jimmy

My Home Depot carries Square tubing and Angle iron, but the selection is not great and it is pricey. I know structurqal tubing is not really a hardware store item, it is readily available about anywhere in the world locally.

The angle iron is also a good idea and the 45's should be much easier to cut than a V. My only concern would be the attachment method. With tubing a large enough hole could be drilled in the corner to all the bolt head to be inside the tube ( use socket headed caps screws for this) but some sort of V shape or cone shaped washer would really be required. One might be able to use a flat head screw successfully too.

[spalm]

My plan is to pull the two square channels together with threaded rods outside of the gantry walls. (?)

Steve

[spalm]

I really need to stop posting so much but just had an idea. Build a square sided torsion box (easy). Cut two strips of wood the same thickness and length as the box. Cut two dados down each strip for the angle iron edges to rest in. Glue these strips to the top and bottom of the box. Attach the angle iron with threaded rod on the outside. I doubt you would need center mounting bolts.

Steve

[anoel]

Ok... I've been watching this thread... and wanted to chime in...

I like the whole anlgle iron thing that Izzlestar posted. that looks like a pretty clean way to make the ways for the X and Y axis... and with a good template the ribs would be easier and really stong since the angle could be 1/8" thick.

Are you guys planning to do a single leadscrew blelow the Torsion box? with a part spanning the gantry sides. Just curious... I'm looking at how you are planning to mount motors and such to what you are designing.

(Might want to go ahead and make the torsion box into a vaccum table with some holes in the ribs and a fixture for a vac hose on the rear.)

[Jimmy Southern]

Hey Izzle,

Love the name by the way.

Welcome to the team love the design. This will greatly simplify matters, as far as the square design goes. This an elegant to the point idea.

As to the attachment, if this were an 1 1/2" angle iron piece and you have used the router ro make all the pieces the same, you could simply predrill & countersink the edge of the angle, well clear of the bearings track, and clamp with some epoxy or gorilla glue then screw the angle down. The "belt & suspenders approach"! I like it!

With two bearings per shaft,this thing would be tough!!!! This solves several design problems. Mostly the future wear & sagging problems.

Lets hear some comments guys. What do you think. Just my opinion Though!

Good idea Izzle, Dig deep and keep it coming!

Thanks,
Jimmy

P.S. I love out of the box thinking!

[spalm]

One of the problems that had bothered me about using angle iron was having to go to larger bearings or a new hold down style for the aluminum angle to keep the two angles from rubbing. Here is one possible hold down solution. I drilled a hole sideways through the angle and inserted a small bolt that passes through an eyebolt. This eyebolt then can be used as the hold down bolt. The angle pieces seem to have enough radius on the corners to keep them apart.

Steve

[mikeschn]

Steve,

That's looking good. Can you show me a photo of that mounted?

Mike...

P.S. I've always like this concept too. I wonder what it would take to make it work...

[spalm]

Mike, like this?

I always wanted to play with V-bearings. Someone on the zone found a cheap supplier for them in China, but you had to buy a hundred. Would not be hard to use up that many if we group purchased. I don't remember the name, going to go look.

anoel, like I was trying to point out in post #203 part 2, I believe we should drive the X screw in the center. This would call for a bar across the bottom of the gantry. My recomodation is that this is another really strong torsion box that is firmly attached to the gantry sides.

Steve

[mvaughn]

I don't want to shoot down this idea especially on the z axis, but lets see if we can brainstorm a simple way to make it work. Maybe some simple geometric way of laying out the pockets so they can be cut, by hand, to make a template to route the pockets for the corner of the square. But we must end up with as close to perfect of a pocket as possible without a mill.

Let the Ideas Fly!
Jimmy

You could make all the parts for the torsion box without the notches for the square tubing. Fully assemble the torsion box and afterwards use the edge of the torsion box as a fence and route out the notches for the tubing. This would be an easy way to make sure all the notches align well.

#1) the carriage can roll forward. When I first tested it with a 30 pound weight hanging from the front, I discovered that the carriage was too weak. I rebuilt it with wrap around sides and am very happy with the strength. I was delighted that the bearing adjusters could bring it back into level with or without the weight. I dropped any further testing. I am a harsher critic now and can detect this roll by pulling and pushing on it. I cranked on the bearing adjusters until the motor stalled, and then backed them off a half turn. Pretty much solved the problem, but I am not sure I like that much pressure. So I just bought some 3/4” square channel at Home Depot (small I know, but it is very close to the 1/2” pipe that I am using). I plan to make a box to support it and report back This problem will rear it self more on small pipe, but if we can nail it there……..

Steve

I'm not sure that the round tubing is solely responsible for this. Similarily, I'm not sure that square tubing will correct this.

I think that a major weak point in this system is the way the skate bearings are mounted. The bolts that are used as axles on each bearing is only mounted on one end, which allows for the axle to deflect. Tightening the bearings down preloads them but allso applies more friction.

Does anyone have any ideas on how to make the bearings resistant to deflection?



.

[izzlestar]

Hey guys, I was grinding away on this idea tonight: turn the angle iron around, so that the bearings ride inside the X axis... Hard to explain, but I drew it up in rhino again. The torsion box would be more complex... or perhaps you could build 3 of them. One for each side and the middle box. The thing about this design is that you could solve the problem of the leadscrew having to run on one side of the gantry... this way you could run it straight through the middle. The gantry could also be a torsion box design. Just an idea! -Carl

[junme]

re angle mount
been playing with this seems to work on paper

[mikeschn]

There's really not much to the z axis, if I follow thru with the adjustable pipe idea. Just box it in, and add another bearing shuttle.

Here's what materialized on my screen this morning!

Mike...

[mikeschn]

Hey guys, I was grinding away on this idea tonight: turn the angle iron around, so that the bearings ride inside the X axis...

Carl,

Can you send me that parasolid...

mykes (at) comcast (dot) net

Thanks,

Mike...

[ger21]

Does anyone have any ideas on how to make the bearings resistant to deflection?

I used 1/4" thick 6061-T6 aluminum angle. The bearings don't deflect at all, even under a LOT of pressure.

[DieGuy]

I used 1/4" thick 6061-T6 aluminum angle. The bearings don't deflect at all, even under a LOT of pressure.

I suspect using steel angle there would help as well.

[DieGuy]

You could make all the parts for the torsion box without the notches for the square tubing. Fully assemble the torsion box and afterwards use the edge of the torsion box as a fence and route out the notches for the tubing. This would be an easy way to make sure all the notches align well.

I'm not sure that the round tubing is solely responsible for this. Similarily, I'm not sure that square tubing will correct this.

I think that a major weak point in this system is the way the skate bearings are mounted. The bolts that are used as axles on each bearing is only mounted on one end, which allows for the axle to deflect. Tightening the bearings down preloads them but allso applies more friction.

Does anyone have any ideas on how to make the bearings resistant to deflection?

Well one way would be to increase the bearing diameter to say an OD of 1.5 inches and get it move away from the corner of the angle iron. The Ebay source for skate bearings (VXD I think) has sealed electric motor bearings in this range and bulk quantites. Then support the axle on both ends with a piece of 2" square tubing mounted to the bearing support angle. Drilled it for the axle and notched it allow the bearing to "stick out" of the side of the tubing. That should eliminate any axle flex.

[spalm]

As far as axel flex goes, I do not think this was what was contributing to the roll that I noticed. I was using small pipe and this allowed the use of a single nut as the bearing spacer. The total axel length was therefore just 1 inch. The use of angle as the rail will also allow the use of such short axels. Using thicker aluminum or steel as the bearing holder is probably a good move. I think what I was seeing was either caused by the tilt on a round pipe problem or it was the four point bearing adjuster flexing.

Steve