[joecnc2006]

Please feel free to submit any redesign as you see fit and maybe together we can thrash out the best possible design. Would I be right to presume the basic Idea is worth pursuing?

John

Sure it is worth pursuing or atleast discusion will sharpen our minds.

On one note, I was tring to find small triangle tubing around 1" on all three sides, this would certainly resolve some of the issues discused. but running out of time so went with what i had.

Design would go as follows: something like 80/20, steel beams for mail support with the trianle tubes bolted to that top and bottom, just like my design above except replacement of the pipe rails with triangle rails, Then use the double bearings on that, and just like above the top bearings are fixed and the lower bearings will provide the adjustment, preload.

what do you think?

Joe

[Oldmanandhistoy]

I respectively disagree with splitting the middle bars apart. It will take four wrenches to adjust this thing. You will have to hold the other three nuts stationary while adjusting any of them unless you could pin or pinch the threaded rod to keep it from turning. (No?)

My plan was to tighten slacken the eight bolts that fix the carriage to the gantry side to make necessary adjustments. So lets say you want to add pre load to the top rail vertically. I would slacken the two top fixing bolts only and tighten the nuts at the top the carriage which would allow me independent adjustment to the top rail. To add pre load to the bottom rail only I would slacken the two bottom fixing bolts only and tighten the bottom two nuts on the carriage and retighten the fixing bolts. Did that make sense?

John

[Oldmanandhistoy]

The main reason to go to twin rails IMHO is to spread the pivot points of the gantry and keep it from racking front to back. The middle bearings offer nothing if this is well carried out.

Your points is very likely correct. Probably in my ignorance I was thinking the more bearings used (up to a certain point) the better this would be allowing the bearing to share the load. I take it this is faulty thinking?

John

[Kipper]

First point to consider is the fact I have little experience with metals working. Secondly I am as far from being a mechanical engineer as you can get.
I very much appreciate the input of fellow members especially the more qualified members who can guide me in the right direction. Without the required skill I do my best and fine that if I do I often get the help needed. If you guys completely redesigned the original idea and I ended up with the best possible solution then I will be a very happy chap indeed. I guarantee I will never be insulted by any constructive suggestion. To any one who has/is putting forward suggestions I would like to say thank you your time and input is very much appreciated

Disclaimer over

Please feel free to submit any redesign as you see fit and maybe together we can thrash out the best possible design. Would I be right to presume the basic Idea is worth pursuing?

John

I think so! and here is my opine/opinion on preloading....I want/need constant alignment allowing for discrepancies in the tubing I intend using so I've opted for a "cam" arrangement which applies a great amount of mechanical advantage for very little effort. No adjustment would be necessary as the spring would take care of that. (attached image of my thoughts) Making the cam requires the use of a lathe or some inventive machining/drilling but does anyone have an opinion regarding the cam/preloading arrangement?

[joecnc2006]

I think so! and here is my opine/opinion on preloading....I want/need constant alignment allowing for discrepancies in the tubing I intend using so I've opted for a "cam" arrangement which applies a great amount of mechanical advantage for very little effort. No adjustment would be necessary as the spring would take care of that. (attached image of my thoughts) Making the cam requires the use of a lathe or some inventive machining/drilling but does anyone have an opinion regarding the cam/preloading arrangement?

Use the cam on only one side/bearing to eliminate movement of otherside.

[technomage]

First point to consider is the fact I have little experience with metals working. Secondly I am as far from being a mechanical engineer as you can get.
I very much appreciate the input of fellow members especially the more qualified members who can guide me in the right direction. Without the required skill I do my best and fine that if I do I often get the help needed. If you guys completely redesigned the original idea and I ended up with the best possible solution then I will be a very happy chap indeed. I guarantee I will never be insulted by any constructive suggestion. To any one who has/is putting forward suggestions I would like to say thank you your time and input is very much appreciated

Disclaimer over

Please feel free to submit any redesign as you see fit and maybe together we can thrash out the best possible design. Would I be right to presume the basic Idea is worth pursuing?

John

There is many a mechanical engineer who would not be able to build a machine like you have. l You aquired the skills and knowledge to build it. Its just that the material you are used to working with is wood a mechanical engineer who has only worked with metal might feel the same way about wood. I have no doubt that you will be more comfortable with metal the more you deal with it Once again if stranded on a Island I would much rather depend on your skill and expertize than most of the engineers I have worked with. Keep with it!
here is a quick sheet on belleville washers
http://www.rctek.com/fixings/bellville_washers.html
Barry

[Oldmanandhistoy]

Design would go as follows: something like 80/20, steel beams for mail support with the trianle tubes bolted to that top and bottom, just like my design above except replacement of the pipe rails with triangle rails, Then use the double bearings on that, and just like above the top bearings are fixed and the lower bearings will provide the adjustment, preload.

what do you think?

Joe

Unfortunately I can’t get away from the axial load on the bearings, although a triangular section as you say would be an advantage and improvement over round tube.

John

[Kipper]

Use the cam on only one side/bearing to eliminate movement of otherside.

Mike Hide nailed that one earlier on. Are you still pursuing round tube for your next project? Master and servant rule...extra pressure on the servant of course

[Kipper]

There is many a mechanical engineer who would not be able to build a machine like you have. l You aquired the skills and knowledge to build it. Its just that the material you are used to working with is wood a mechanical engineer who has only worked with metal might feel the same way about wood. I have no doubt that you will be more comfortable with metal the more you deal with it Once again if stranded on a Island I would much rather depend on your skill and expertize than most of the engineers I have worked with. Keep with it!
here is a quick sheet on belleville washers
http://www.rctek.com/fixings/bellville_washers.html
Barry

On a day to day basis I use Belleville washers...I haven't found any use for such apart from the obvious....

[Oldmanandhistoy]

There is many a mechanical engineer who would not be able to build a machine like you have. l You aquired the skills and knowledge to build it. Its just that the material you are used to working with is wood a mechanical engineer who has only worked with metal might feel the same way about wood. I have no doubt that you will be more comfortable with metal the more you deal with it Once again if stranded on a Island I would much rather depend on your skill and expertize than most of the engineers I have worked with. Keep with it!
here is a quick sheet on belleville washers
http://www.rctek.com/fixings/bellville_washers.html
Barry

I appreciate your comments and thank you for the link I will study it. I have to be honest I have heard of Bellville washers but have never really had the time to investigate.

John

[technomage]

Your points is very likely correct. Probably in my ignorance I was thinking the more bearings used (up to a certain point) the better this would be allowing the bearing to share the load. I take it this is faulty thinking?

John

I think Joe and others have proved that even with a small contact area of a circle on a circle those little skate bearings will carry a pretty good load.
If they have full width contact it should be much greater.
I have been wrestling with how many is to many bearing maybe Ger or one of the other uber posters may be able to shed some light on when a bearing is just a hinderance not a help.

[Oldmanandhistoy]

Mike Hide nailed that one earlier on. Are you still pursuing round tube for your next project? Master and servant rule...extra pressure on the servant of course

I personally think all designs have their own merits. I built two machines myself using round tube systems. It is an easily implemented system which obviously works well in a diy machine for cutting timber and plastics. I do think it is time for it to move over for a system like ger21’s system pictured in post #1.

As can be seen by my own design and indeed your idea of using springs they very quickly become more complex and for the beginner it would be a sharp learning curve which could prevent them from pursuing the hobby. I still think ger21’s original design post #1 (with the addition of square tube rails imho) is excellent and should stop there for a basic machine. It is a clean and easily obtainable system for the average builder. In fact I think I own him an apology for polluting his thread with more advanced and complex systems which should have been in a separate thread called something like “advanced diy linear rail systems”.

John

[Oldmanandhistoy]

I have been wrestling with how many is to many bearing maybe Ger or one of the other uber posters may be able to shed some light on when a bearing is just a hinderance not a help.

I personally think that more than two sets on any given side of a rail is to many but would also be interested in other members opinions.

John

[Oldmanandhistoy]

It was just a bad idea keep reading please

John

[technomage]

I personally think all designs have their own merits. I built two machines myself using round tube systems. It is an easily implemented system which obviously works well in a diy machine for cutting timber and plastics. I do think it is time for it to move over for a system like ger21’s system pictured in post #1.

As can be seen by my own design and indeed your idea of using springs they very quickly become more complex and for the beginner it would be a sharp learning curve which could prevent them from pursuing the hobby. I still think ger21’s original design post #1 (with the addition of square tube rails imho) is excellent and should stop there for a basic machine. It is a clean and easily obtainable system for the average builder. In fact I think I own him an apology for polluting his thread with more advanced and complex systems which should have been in a separate thread call something like “advanced diy linear rail systems”.


John

While looking at Ger's post #1 looks like a full width contact at each end on each plane and no "extra" bearings in the middle.

[mike hide]

I was just thinking after looking at your prelim design...Maybe some spacers would prevent the tube from crushing? Oh and sorry for cutting your fingers off I moved the tubes farther apart and placed the adjusting nuts to the outside of the tube too....Have you experienced any binding with the rigid adjusters? Myself I have nothing to show until I decide which direction to go next (It wont be round tube ) Waiting for the stockholders to send a full product catalogue to work so I can pick and choose. :cheers:

.

To be honest I do not think the web thickness in the picture is capable of sustaining any reasonable preload level and secondly the cantilever loading of the bearing bolts . Take a look at the top square section in the picture .

Perhaps square section tubing with heavier webs is available bearing in mind that the square tubing has to sustain fairly high torque levels ..... Perhaps a better solution might be to use unequal angle irons .

[Oldmanandhistoy]

.

To be honest I do not think the web thickness in the picture is capable of sustaining any reasonable preload level and secondly the cantilever loading of the bearing bolts . Take a look at the top square section in the picture .

Perhaps square section tubing with heavier webs is available bearing in mind that the square tubing has to sustain fairly high torque levels ..... Perhaps a better solution might be to use unequal angle irons .

Point taken thank you.

What do you think about the number and arrangement of bearings?

[Oldmanandhistoy]

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

[ger21]

You mentioned in an earlier post that you would use all thread across the bottom of your gantry to add preload to your X axis rails. Does this imply you would not uses a torsion box across the bottom of your gantry?

I'm not a fan of the bottom torsion box. The only reason for it imo is to hold the nut for a center leadscrew. Which I'm also not a fan of.

My router uses the all thread across the bottom, and even on round pipe, I don't see any benefit to the bottom torsion box. It will however help to stiffen weak gantry sides that may have a tendency to flex a bit.

I've read most of the posts here, but haven't had any time to reply. Don't worry about the hijack, remember, I can kick you guys out whenever I want.

[Oldmanandhistoy]

I'm not a fan of the bottom torsion box. The only reason for it imo is to hold the nut for a center leadscrew. Which I'm also not a fan of.

My router uses the all thread across the bottom, and even on round pipe, I don't see any benefit to the bottom torsion box. It will however help to stiffen weak gantry sides that may have a tendency to flex a bit.

Thanks for the reply. Do you have a link to your machine please?

I've read most of the posts here, but haven't had any time to reply. Don't worry about the hijack, remember, I can kick you guys out whenever I want.

I think I may keep my head down for a little while now

Or maybe not(wedge)

John