how to build a manual rotator

recently in another thread, a subscriber showed some interest in building a manual pipe rotator for welding... This type of rotator is one that works
horizontally, rather than a turntable style rotator.
Id like to offer my experiences and ask others to share theirs....
Ive used a few types of rotators, from small simple manual up to medium-largish automatic rotators used for welding 45 tonne water ballast rollers.
The manual types also have some variation in size and type, but they share some common elements. All the ones i have used had two sets of two wheels... sometimes each set of two wheels were on their own individual mounts so they can be spaced apart as fas as necessary, and sometimes mounted on a common frame. The common frame type seems a bit more stable, but the individual frames are more adaptable to different lengths of pipe.
In terms of wheels, there seem two styles; those that use the wheels as an earth, and those that dont. The ones that use the wheels as the earth obviously have steel wheels, and they vary from the simple being just a wheel oxy cut out of some steel and suspended on a bit of rod. the rod quite often drops into a slot, or several slots, allowing the wheels to be easily replaced, or the spacing between the wheels changed for larger diameters of pipework. the more complex types have a threaded adjuster to space the wheels apart and use something similar to a bearing as the wheel. I find that the type which uses the wheel as the earth suffers from arcing out sometimes, so when using them i still try to clamp the earth lead to the pipe. there is a technique to this.
The ones that dont use the wheel as the earth can use any type of wheel... plastic, rubber, etc etc... you could use old skateboard wheels, or wheels off anything. these wheels do roll very nicely and smoothly compared to steel wheels, but have the downside of melting very easily... you have to be careful.
To attach the earth clamp in a usable manner, i usually attach the earth lead to the inside of the end im not welding, then wind the lead a couple of times around the pipe *opposite to the direction i will be rolling*. This means that as i roll, the lead will be unwinding off the pipe.
rather than trying to rotate smoothly and keep the gun still with a manual roller, i start at about 11:00, weld over through 12, 1, 2 and as i get to about 3:00, i rotate the pipe with my free hand fairly sharply, then continue in this way. I usually only need to do 3 or sometimes 4 rotations to fully weld pipe.
This tenchnique is really not so useful on small diameter pipes, for anything under about 3" in diameter, i just do two runs, starting at 12:00 and running straight around to 6:00, then a second run the same on the other side. keeping the gun/electrode parallel to the face of the pipe is my strategy for getting a consistent and neet weld. most people who have trouble doing positional welding also have trouble controlling their gun angle.
I find the rotator most useful for doing flange work on large pipe; read 12" plus. Most drawings call for this pipework to be welded in a single run, and even if you rotate slowly, you can do a really neat job if it. the inside of the flange also usually needs to be welded to the pipe, creating a double seal, but i usually get an apprentice to do the rotating while i weld the face. for the inside, i start at about 3:00 (or 9:00 is welding left to right) and head for 6. as i get there, i ask the apprentice to rotate... its not hard to keep the gun/electrode on target if he rotates slowly. the final result is a very consistent bead, and you'd have to be *really* looking closely to find the point i rotated at.
Shaun
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Thank you Schaun! Interesting and innovative tips. I started sketching my rotator. The idea of changeable different size of wheelsets is good but I think I try to use skating board wheels which you mentioned. My need is to make posts with a "shoulder" in between. So there is two size of pipes in one post. Dimensions of the pipes vary. Do you have any ideas how to center the smaller pipe just in the middle of the bigger one easily and fast?
I was drafting kind of X-shaped mekanism to regulate the position of the rollers but I'm not so sure about the stability of the system when rotating bigger pipes.
Here is some examples of the posts I use.
http://www.webbisivu.com/Somatgallery.aspx
With best greetings: Jukkis
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nice looking work! Doing work like this efficiently really depends on your volume and your resources.... Im assuming most of the work you do is for the government, and relatively small runs, 2 or 3 units at a time? Do you have a large shop space? Do you have large benches?
There are two ways you could go depending on volume and resources... if you have limited resources and small volumes, id be inclined to just carry on however you are going (using levels, or spacers on benches?). If your volume is higher, or you have plenty of space, i'd be inclined to go with 4 sets of rollers, two at the smaller diameter pipe, and 2 at the larger diameter pipe, to keep everything nice and level. If it was done well and accurately, it would give a very fast and consistent way of getting it all centered and done well. This would only work if you are using the same diameters of pipe all the time.
you would really need to have a good surface to use as a datum to set all this up. to tale it a step further, you might use bolts to adjust the relative heights of all the rollers. this could be a good flexible setup for you, I'd use slotted areas for the wheels so you can quickly pull them out and put them in the next slot if you need to. Then adjusting the heights would let you get different centers etc and keep it all dead level.
an intermediary solution might be using stands to mount the sets of rollers on if you dont have enough bench/floor space. you could move them away, and they could have threaded adjusters on them too. The problem with this of course is that there would be more stup time, and the slightest bump would put you out of line again.
Shaun
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Thanks!
shop
Im working alone in my small shop at this moment. I have no private customers (too expensive and heavy design). All my work goes to the government or to local public areas, towns, cemetarys.... The runs are small, yes, from 1 to about 30 pieces. My work was before to desig outdoor furniture. Now I started manufacturig them too. Been doing this now about 5 years.
Untill now I have made my posts so as you thought, using spacers and levels on benches. It works OK. Maybe I dont really necessary need a special rolling tool to veld the small number of posts I need to make from time to time. I have been trying to study how to make fast velding jigs for small runs. My problem seems to be that i dont have a really good surface. I have a old 1500x 2500x 30mm thick steel block as veldig table. Unfortunately it is not even. I think the first thing is to make a good velding table, ideal would be to have a slot system and grid too as you and other men here have mentioned earlies.
My dream table is this... http://www.demmeler.com/eindex.html Also http://www.bluco.com/welding.php
"The Demmeler system is based on a five-sided high-tensile-strength steel table with a grid of accurately located 28-mm bores on 100-mm centers, a pattern of grid lines across the top, and a scale etched on all four edges to aid setups. Flatness of the table is 0.10 mm overall and the bores are located ฑ0.030 -mm hole-to-hole and ฑ0.05 mm overall. System angles and blocks can be attached to the sides of the table to act as outriggers for parts that are larger than the table surface."
This table is very expensive, but I think I try to use some ideas from it and make a new veldingtable myself. Seems to be that in order to do rapid prototyping, an even surface is number one, slots number two, grid number three.
I save your message for later use. Thank you for your good advice.
Jukkis

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On Fri, 9 Mar 2007 12:53:51 +0200, "JP Sipponen"

If you are familiar with the grid material used in catwalks, this material, properly scrounged and secured to a solid framework, makes very good welding tables. And very inexpensively.
Not expanded metal, but the catwalk made up of long runs of usually 3/16"x 1" strips about 1" apart all welded to cross members every 12" or so.
C-clamps drop between the runs easily and several Ive seen, the owners made up a toggle bolt arrangement out of all-thread and tapped 3/4" strips on one end, drilled strips on the other with simple nuts to tighten things up with.
Gunner
"Liberalism is a philosophy of consolation for Western civilization as it commits suicide" - James Burnham
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Floor Gratings as a velding table? Yes... interesting idea, there is the grid and the slots! Im just wondering how even the surface is. V-blocks for example need very flat surface. http://www.bluco.com/welding/catalogd28/vblocks.html
Jukkis
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On Fri, 9 Mar 2007 21:59:14 +0200, "JP Sipponen"

They are quite flat when properly supported. Ive never measured one..but a bunch of outlaw funny cars, sand rails and other home brewed motor vehicles come off floor grating welding benches in my area.
Gunner
"Liberalism is a philosophy of consolation for Western civilization as it commits suicide" - James Burnham
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for
Seems to be that the welded gratings are a bit too uneven as a quality velding table. Unfortunately. Great idea anyway if if you dont need much accuracy.
http://www.gratingpacific.com/manufacturing__installation.htm
Jukkis
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On Sun, 11 Mar 2007 21:42:40 +0200, "JP Sipponen"

If you are referring to the longitudnal bow..the only thing there that has anything to do with flatness..you do realize I mentioned "when properly supported" do you not?
Gunner
Never worry about theory as long as the machinery does what it's supposed to do. Robert A. Heinlein
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Yes... I like the idea. But unfortunately the possible longitudinal bow, 1/200 of length, is a bit too much. Also cross bar location is not accurate enough to be used as a positioning aid. Seems to be that the only possibility is to buy a thick steel plate and drill rows of holes with CNC drill.
Jukkis
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On Mon, 12 Mar 2007 10:43:57 +0200, "JP Sipponen"

When properly fastened down...there is no bow. And yes, grid dimensions they quote "worst case" may be off a smidge.
Now if you are welding within small thousands..I can see your point. Most welding however is within fractions of an inch and is checked with squares and so forth before final welds are made, after tacking, even on the big flat ground welding tables. They are made for production of large quantities of weldments, and fixturing is most often used.
Shrug..the more accurate the large weldment, the more it costs to do. If you are small production or hobbiest..it hardly pays to buy the very big and very expensive tables, or positioning plates.
But..you know what you need, or you think you need, so good luck.
Gunner
Never worry about theory as long as the machinery does what it's supposed to do. Robert A. Heinlein
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Gunner Asch wrote:

Heres the welding table of my (welding related) dreams! http://www.bluco.com/welding.php
Nice!!! No I have no idea how much. Lots, I bet!
I was looking at knocking off something like this on a smaller scale for home use, but it's WAY down the list. Way down.
Cheers Trevor Jones
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