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200k
10-15-2015, 07:07 PM
The short version: You physically can’t do it.

NEW IMPORTANT EDIT 10/16/15: The short version: You CAN do it but you have to modify the LHR jig and fool the software. See entry #14 for detail on how it’s done! Of course you can read all the other entries before that to gain all the pithy comments, witty remarks, and wise advice that led up to it.

Back to the original post....

The long version: (with explanation, trial, and alternate ways of doing approximately the same of thing)

When I first saw the LHR rotary jig I thought, “What a great thing to carve PVC pipe on!” Schedule 40 PVC pipe is about ¼” thick, it is not brittle and though it will get pliable with heat, it will not melt easily and form the malignant little plastic balls like polycarbonate (Lexan) does that cripple the machine when they get thrown off the spindle by centrifugal force into assorted critical parts. A polycarbonate carve also looks like it was done with a soldering iron (don’t ask me how I know all this). Anyway, since the machine has a 5” max height for the Z axis and the jig has a max carve height of 4 ¼”, I thought 4” PVC would be a great medium. I thought about it for several months and then I went to the CW Conference 2014 and blown away when I saw Michael’s Mona Lisa carved in 3” PVC. I asked him why he didn’t use 4” and he reminded me (I already knew it, but I just didn’t think about it) that 4” PVC is actually 4 ½” outside diameter just like 3” PVC has an outside diameter of 3 ½”. Since the jig and software only take a maximum of 4 ¼” diameter, this pretty much ruled out 4” PVC as a medium.

But sometimes things get stuck on your mind and I kept thinking about how to jury rig or shoehorn in a 4 ½” diameter rotary project. I looked at all the jigs that people have made and posted on the Forum and had several in depth PMs with Dan Bergerud on how to fool the machine into letting the jig do it without the machine knowing it was doing it. We did come up with a way to fool the software – I say “we” but I really mean Dan thought of it and I agreed to it. So I made some end plugs for 4” PVC using Designer (it carves in 7-8 minutes) and rigged up a 7” long piece of 4” PVC in the rotary jig. (1st JPG). I put it in the machine, cranked it down, and checked things. The bottom of the cylinder was clear (2nd JPG) but the top of the cylinder was pressed on the bottom of the Z truck. (see 3rd JPG) I couldn’t tell if the crank/head pressure was greater on the rollers or the PVC cylinder/z-truck but I know it was at working pressure. I could manually traverse the z-truck but it embossed a groove in the PVC. (4th JPG)
Hmmmmmmm, this would not work. There’s no way the jig would rotate the PVC while the z-truck was dragging across it, not to mention the stress on the z-truck motor and gearing. It just won’t work. There is physically not enough room to put a 4 ½” tube, or cylinder in the Rotary Jig and have the CW machine carve it.

So… Ways of doing something like carving 4” PVC without actually doing it:


Carve 3” PVC. It works. We know it and plenty of us have done very nice things with it. The diameter is smaller so the curvature is tighter but if you limit your carve to about 1/3 the diameter the picture won’t get too much cylindrical distortion.
Carve 4” PVC – but first you have to cut and remove a strip .0785398” wide along the length of the tube and then cement the sides together again (and then get the whole thing ROUND again). This produces a tubing outside diameter of 4 ¼” which is within the limits of the machine.
Carve your lithopane on Corian and then use thermoforming (heat molding) to form an arc or circle if it has a large enough diameter. According to this PDF document: http://www2.dupont.com/Surfaces/en_US/assets/pdf/fabmanual/Ch16-ThermoformingCorian.pdf the minimum inside radius for thermoforming 6mm (¼”) thick Corian is 1” so a 4” inside diameter should be a “piece of cake”. Yeah, right. I’ve done thermoforming and it’s not really hard but it ain’t easy either. (last JPG) It took me several tries to get one right.
Design an entirely new rotary jig that moves that last ½” below the 4 ½” cylinder to up above it instead, i.e. shifts the axis down enough to clear the z-truck.* Of course the rotary software won’t work because it is calibrated on the current axis and is limited and to a max of 4 ¼”. So we need a new rotary jig that uses the regular Designer software OR a new rotary jig AND new rotary software!



I realize a couple of these suggestions are not only beyond the abilities of most of us users, but are beyond credibility itself. Since the CW is already an amazingly versatile machine – particularly as compared to others in its price range, I don’t feel this restriction is any great cross to bear. I feel confident I can justifiably reconcile to my family, friends, and indeed, the world, that my life’s accomplishments will not be diminished if I never carve a lithopane from 4” PVC tubing. I hope you all can find this peace too. ;-)



*OTOH, I have a new design in mind that just may be able to pull this off… no bets – more thinking and designing required. But I have other projects that need to be done first so don’t hold your breath.

bergerud
10-15-2015, 07:44 PM
I still believe it can be done. You are almost there.

How about this: Add 1/8" thick rails along the tops of the rotary jig plates. This will raise the head an extra 1/8". This kills two birds with one stone. It stops the truck from hitting the pipe and it raises the touch point of the bit by the 1/8" which is required to carve the 4.5" pipe.

200k
10-15-2015, 08:48 PM
Nope. You ain't got the picture. The part of the z-truck that contacts the cylinder is the part that ONLY moves laterally. It's the part that the bearings are screwed into. Now that I say that I realize that I have been calling it the z-truck when in fact it is the Y-truck - the part that moves side to side, not the Z-truck that moves up and down.

Sorry about that. My bad. I was looking at the z-truck and it is actually below the rails part of the y-truck (that the z-truck rides on) that contacts the cylinder. Look at the third photo again and you'll see what I am talking about. If not, let me know and I'll take a more detailed photo.

bergerud
10-15-2015, 08:54 PM
All the parts except the jig and dowel go up when the head goes up. If you lay spacers on top of the jig plates. The head will not come down as far. The head, the rollers, the y carriage will all be up 1/8" higher.

Try it. Tape two 1/8" strips of wood to the tops of the jig and clamp it in.

200k
10-15-2015, 09:06 PM
MAN! you are Johnny-on-the-spot. I posted my message and then suddenly realized what you actually said was right and I had misunderstood. But before I got a chance to post an EDIT, you already posted a response! In any case, below is my edit of my above response, the first part of which I entirely deleted because you were right. This "quick reply" option can really catch you! Hopefully I have this one right.
-------------------------------------------------------------------

Hmmm. it's worth a try. I can see what you are talking about. I must be slipping. I used to see that mechanical stuff before anyone else. Hell, I used to imagine that stuff in my head and then draw it out.

OTOH I got the vernacular wrong. I was looking at the z-truck but it is actually below the rails part of the y-truck (that the z-truck rides on) that contacts the cylinder. So the problem is contact with the Y-truck not Z-truck.

It's late now and I have two MD appointments tomorrow so I won't be able to follow up with the shims until late tomorrow afternoon... unless my wife have more tasks for me. But it just may work after all and I'll keep at it until we know for sure. Thanks again.

I'm glad you're on our side.

bergerud
10-15-2015, 09:13 PM
Sorry, I just want to see this work!

SteveNelson46
10-16-2015, 12:12 PM
If you have a lathe you can use 4" schedule 80 PVC pipe and turn off .125". This will make the outside diameter 4.25" with a wall thickness of .212". After a little sanding while still in the lathe there should be enough wall thickness left for carving and bit clearance. I've never tried it but it sounds like it would work.

bergerud
10-16-2015, 12:15 PM
This is going to work! But, could you not get 1/8" thick wall pipe which would have a OD of 4.25?

SteveNelson46
10-16-2015, 12:27 PM
This is going to work! But, could you not get 1/8" thick wall pipe which would have a OD of 4.25?

Standard wall thickness for schedule 40 PVC pipe is .237" and .337" for schedule 80. Both have an outside diameter of 4.5". There might be drain or vent pipe that is different but generally, nonstandard pipe sizes would have to be custom ordered.

200k
10-16-2015, 06:38 PM
The downside of using Schedule 80 is that the only Schedule 80 I've seen comes in a dark gray color. That's not optimum for use in carving cylindrical lithopanes.

DianMayfield
10-16-2015, 06:53 PM
78304Oh, the choices you might have :)

Just to brighten everyone's day!

DocWheeler
10-16-2015, 08:12 PM
It would seem that the places on the Z-truck that touch the PVC could be ground off without damaging the machine.
The need to change the touch-point would be addressed differently.

bergerud
10-16-2015, 08:28 PM
There is no need. It is an easy matter to make the jig plates 1/8" higher. Tape on some strips of wood (use some silver tape) and the machine would not know the difference. After putting some thought into this, I think it should not be difficult to carve 4.5" diameter stock. I have, however, not actually done it and may be speaking too soon!

I will be interested to see if 200k has any problems.

200k
10-16-2015, 10:38 PM
Yes you can do it!

In entry #1 of this thread I related that the LHR jig alone will not physically permit 4 ½” diameter workpiece because it contacts/rubs on the bottom of the Y-truck. The solution was to raise the machine head height and hence the Y-truck. I cut a pair of jig end-plate caps out of ½” Corian and taped them in place. (photo 1) When clamped in the machine, this relieved the problem of contact between the workpiece and the y-truck. (photo 2)

Unfortunately when trying to run a carve the first thing that happened is that a warning showed at the beginning of the carve sequence even before it would measure the board - “Clear Board Sensor”. Hmmmmm. The Corian caps I put on the top of the jig ends came very close (but not touching) to the board sensor where it starts its transit across the Y axis. I guess if the board sensor reads a high enough number even before it starts moving across the board it can’t tell where the board starts and results in the fault message. I took the LCD-display-side Corian cap (left as you face the machine) back to the tablesaw and cut a notch down to the aluminum to give enough clearance from the board sensor so it could start its measuring transit with a zero read. When I put it back in the machine, it worked and I got all the way through all the bit calibrations and started the carve.

Another glitch. It tried to carve the piece about ¼” above the surface – an air carve. OK, so I need to jog the bit to the actual workpiece to gauge the real surface. Another run through the menu and at the point where the bit descends to the left jig plate I hit STOP and then tried to JOG to position it to the workpiece. The menu will not let you do that. It says “hit STOP to jog to position” but when you do it just reverts to “ENTER to continue or STOP to abort”. You never get the chance to press 3 to jog to position. OK, so the machine is calculating the radius of the workpiece from the top of the Corian cap. Since the desired radius of the workpiece is only 1/8” greater than the 4 ¼” entered into the machine, I needed to make a notch in the Corian cap that added only that 1/8” on top of the aluminum – not the entire 5/16”. Back to the tablesaw. I also added a lateral groove to let the bit bypass the Corian cap at the start of its calibration sequence. (photo 3) (photo 4)

With all the Corian cap grooves and notches in place, I tried again. This time it started to carve at the right depth. Success! The results of the first complete carve is shown in photo 5.

There a couple of caveats I need to add. First of all the 4” Schedule 40 PVC I used was foam core not solid – hence the yellowish cast. It’s what I had on hand and this was just an experiment to see if it could be done. I strongly suggest using solid PVC pipe for lithopanes and not the cheaper foam core stuff. The latter doesn’t carve as nicely plus, when illuminated, it is always yellow no matter how blue your source light is. Look at the edge of the tubing and you can see. If it is white throughout then it is solid PVC. If it has smooth white inner and outer veneers and a coarse, softer yellowish core, it is foam core. I’ve found that around here Home Depot carries solid PVC and Lowe’s carries the foam core stuff. I hate that because Lowe’s is 15 miles closer to my house than the nearest HD, but what can ya do?

Second, I stretched the pattern vertically by multiplying the original height by 1.0588235, which is the ratio difference in circumference between 4.25” and 4.5”. I did this because the machine was rotating the cylinder at the rate that was appropriate for each cut using a 4.25” diameter. The same number of arc degrees would be moved but a greater surface length would be covered. Stretching the height of the pattern would keep the length to width ratio equal in the final carve.

Finally, the last photo looks like there is some severe cylindrical distortion in the carve but that is an artifact of my cell phone camera. Cell cameras have a very wide angle lens that gives a mild fisheye effect in everything. The actual carve looks very proportional in real life.

Well that’s about it. I’ll now open the floor for discussion.

Questions?

bergerud
10-17-2015, 12:54 AM
Good job. Nothing like doing it to prove it can be done!

A few notes about the rotary may help. The depth touch is the touch on the top of the drive plate. The machine knows that the axle is 1.75" below that. One cannot touch on the dowel. (That is only when calibrating.) The shim had to be 1/8" thick. The sensor error was because your Corian cap was too wide. The board sensor encountered the edge too close to the keypad. My idea was just to put 1/4" wide, 1/8" thick strips on top of the plates and wrap aluminum tape around them to hold them on. Simply raise the effective height by 1/8". I think if one does that, the machine will operate as normal.

This is the start of a new era in rotary lithos. Good one Steve.

200k
10-17-2015, 08:16 AM
In it's most basic form, the only thing you need to do this kind of carve is an addition to the top of each end (front and back) of both jig plates of about 1/4"+ on the outside inch or so - the part that the rollers actually press on, and the addition of 1/8" in the center for the depth touch. I tried all this with the 1/2" dadoed Corian because the jig end plates are only 1/4" thick and it seemed too small to just lay a 1/4" x 1/4" strip on top of the plates, tape them down and then crank the head down hard. It shouldn't move... but if it did, it might do something nasty while the machine is running.

I plan to make something less complicated on the lines of this rather than the Corian strips I used in the experiment for long term use.

bergerud
10-17-2015, 09:01 AM
Here is something you might be interested in. When I was beta testing the CW rotary jig, I made some prototype "add ons". One of these was some braces for the top of the jig. I was worried that the jig might need to be held in place by more than the tabs at the bottom and I was also worried about the small surface area for the rollers on top of the jig plates. Something similar to these, but more easily removable, might be an idea.

200k
10-17-2015, 02:53 PM
I took my results of yesterday and stripped them down to the bare essentials.

What is left is five very small pieces that all can be taped to the LHR jig with blue tape, making easy removal for other projects. I kept the ½” x ½” Corian with a dado of ¼” x 3/16” so the machine head is raised 5/16”. The difference is that instead of covering the entire length of the jig ends, it’s now cut down into two pieces of 1 ¼” long that stay are the ends where the rollers compress. For the middle where the bit touchpoint is raised I simply cut a small piece of 1/8” thick aluminum to length of 1” and a width of ¼” to match the thickness of the jig ends. All these parts are simply taped to the jig with blue tape. (See photos). BTW, the aluminum foil ducting tape is in the photo because that’s what I was going to use to affix the pieces, but I decided that blue tape would be sufficient and much easier to remove.

I haven’t’ tried to carve with this setup yet just because it’s Saturday and my wife has “plans” for my day. I did get to Home Depot and bought some solid 4” PVC so I can do a proper finish carve. I’ll post the results.

Dan, your braces are nice (as is pretty much everything you design) but even though they give a broader surface for the rollers upon which to rest, they don’t raise the head above its normal level. Of course that could easily be changed in a matter of a couple of minutes in Designer. But it looks like you have made them attach to the jig on the threaded rod which would require more time to bolt and unbolt than applying just a bit of tape to my little pieces. That said, I like the idea of a greater surface area contacting the rollers than just a little ½” wide flat piece at each end. To know whether it makes a difference would need further experimentation but unless my little blocks have problems staying in place, I won’t pursue it just now.

Edit# 1: I just realized I will need to file a shallow vertical groove on the side of the aluminum shim for the bit bypass. Not too much, maybe 1/16" deep, because that is the same place the bit checks for board height and I don't want it to miss. The original aluminum end plate already has a groove that is worn in there by the bits themselves and I imagine it can't be good for the bits to have them pushed sideways as it descends in the beginning of the bit check. Easy fix. Two minutes.

sunmiztres
10-19-2015, 06:52 PM
Great job 2000K and thanks for sharing. I just got done buying some 4" PVC to try this out as I am very interested. To me the way it sounds I could just put the 1/4" wide, 1/8" thick strips on top of the plates. Would I need to make the indentation where the bit touches during calibration? I just want to make sure the depth during carving is correct. Again great job.
Bergerud, Couldn't we take your jig and add the 1/8 strips into the design so they lay over the top plate? What do you think?

bergerud
10-19-2015, 08:35 PM
Great job 2000K and thanks for sharing. I just got done buying some 4" PVC to try this out as I am very interested. To me the way it sounds I could just put the 1/4" wide, 1/8" thick strips on top of the plates. Would I need to make the indentation where the bit touches during calibration? I just want to make sure the depth during carving is correct. Again great job.
Bergerud, Couldn't we take your jig and add the 1/8 strips into the design so they lay over the top plate? What do you think?

I think that is right. 1/8" strips taped to the tops of the plates should be good. The strips do two things: raise the head to give clearance under the y truck and raise the bit touch point. The touch point has to be 1/8" higher because that is how much larger the radius of the 4" pipe is. (4.5-4.25)/2.

The machine will carve thinking it is carving a 4.25" diameter. This will result in the pattern being stretched by 4.5/4.25 = 1.06 in the x. (The pattern which is sized in Designer to wrap around the circumference of a 4.25" diameter will be stretched when it is fit around the circumference of the 4.5" diameter pipe.) To compensate for that, one could stretch the y of the pattern in Designer by the same amount. That way, the pattern will end up one to one again. (It is, however, only a 6% difference and maybe it does not matter too much.)

Maybe 200k will chime in with some tips since he is the one who has done it.

200k
10-19-2015, 09:01 PM
Great job 200K and thanks for sharing. I just got done buying some 4" PVC to try this out as I am very interested. To me the way it sounds I could just put the 1/4" wide, 1/8" thick strips on top of the plates. Would I need to make the indentation where the bit touches during calibration? I just want to make sure the depth during carving is correct. Again great job.
Bergerud, Couldn't we take your jig and add the 1/8 strips into the design so they lay over the top plate? What do you think?

I had trouble with the board sensor stalling when I used 1/2" wide Corian strips. The 1/4" wide strips should pass muster. Make sure the outside edge of the middle piece is flush so the bit can bypass the jig on the first descent or you will get a z-stall. I even have a small groove to permit the carving(tapered) bit to slide down next to it.

Just be sure the Y-truck is not contacting the PVC workpiece. My Corian pieces raise the machine head 5/16" to prevent this but it's got a little overkill built in. You might get away with only 1/8" extra height, but I'm sure 1/4" would certainly work. Maybe double up the thickness at the ends? Just make sure you have only 1/8" extra height in the middle where the bit touchpoint is to calibrate the workpiece height.

I'm amazed how simple the solution turned out to be after going through a slew of false starts and dead ends in getting there.

200k

mtylerfl
10-20-2015, 06:10 PM
Wow! I just ran across this thread after returning from a week at sea. It is an absolute joy to watch/read the thought process you and Dan are working through. Kudos to you both and congratulations for making the CW Rotary Jig that much more fun and useful. I am totally impressed. Thank you!

200k
10-22-2015, 07:38 PM
Thank you very much Michael. Praise coming from such a creative guy as you is high praise indeed. I can truthfully say that I wouldn't have been able to accomplish it without Dan's input and encouragement. But that's what the Forum is all about, right?

I am constantly amazed at the amount of knowledge imparted and the marvelous projects that people post on this forum. This is the first time I actually feel I've contributed something besides an "Attaboy!", not that those are unworthy or unwarranted. Appreciation for those who accomplish artistic and skilled projects is vital encouragement to keep the creative juices going. Frankly I don't see how you manage to come up with a new, original project every month. I may be good at copying creativity, but muchos kudos to you for the Real Deal.

gbmoore3
11-05-2015, 08:20 PM
Fantastic solution. I ran into that problem and gave up and went to a smaller diameter. Now I can try that diameter again.
Thanks,
George

sunmiztres
11-05-2015, 10:12 PM
I added a 1/8 strip on the rails and had no problem carving the 4" PVC without a machine error but I am having a problem getting the depth correct. It is carving much deeper then it should. I ran 2 tests and both of the tests it is carving about 3/16" to deep. On the 2nd carving I readjusted the depth settings to .090 and it almost carved through as well. Te 4" PVC has a diameter of 4.5". Is there a special depth setting needed when using the 4" PVC? I did not think so since we added the 1/8 strip but I was thinking maybe I need to add a 1/4" strip along the top of the rotary rails. Any suggestions? Thank you

bergerud
11-05-2015, 11:09 PM
That sounds strange. If the dowel in Designer was 4.25" and the strip added 1/8" to the touch height, it should have carved the right depth on 4.5". Give everything a double check. Was the dowel in Designer 4.25"?

sunmiztres
11-06-2015, 08:09 AM
That sounds strange. If the dowel in Designer was 4.25" and the strip added 1/8" to the touch height, it should have carved the right depth on 4.5". Give everything a double check. Was the dowel in Designer 4.25"?.

Yes the dowel was set to 4.25". On the 2nd test to avoid carve through I set the depth of the picture and lettering very shallow but still had carve through on the picture. Most of the right hand side of the picture carved through. I am including the MPC in case you can find anything wrong. Thank you

bergerud
11-06-2015, 09:00 AM
The mpc looks ok. The machine does not actually touch the dowel to find the surface as it does for boards. The machine knows the touch point is 1.75" above the jig axle. If you were carving a 4.25" dowel, the machine would expect the dowel surface to be 2.125" - 1.75" = 0.375" above the touch spot. Using the 4.5" pipe and raising the touch spot by 1/8" gives the same difference. Maybe you could check that the pipe surface really is 3/8" above the touch point.

Use the z sensor data. Put the bit on the pipe and turn on the machine. Now look at the z sensor data (0 - 7 -down arrow a few). It will read 0.000. Move the truck over and touch on the top of the 1/8" shim. The z sensor should read 0.375. (This assumes, of course, that the pipe is centered and really is 4.5" in diameter.)

sunmiztres
11-06-2015, 10:00 AM
The mpc looks ok. The machine does not actually touch the dowel to find the surface as it does for boards. The machine knows the touch point is 1.75" above the jig axle. If you were carving a 4.25" dowel, the machine would expect the dowel surface to be 2.125" - 1.75" = 0.375" above the touch spot. Using the 4.5" pipe and raising the touch spot by 1/8" gives the same difference. Maybe you could check that the pipe surface really is 3/8" above the touch point.

Use the z sensor data. Put the bit on the pipe and turn on the machine. Now look at the z sensor data (0 - 7 -down arrow a few). It will read 0.000. Move the truck over and touch on the top of the 1/8" shim. The z sensor should read 0.375. (This assumes, of course, that the pipe is centered and really is 4.5" in diameter.)

I just finished doing what you said and I got all kinds of readings. First I put the bit on the middle of the pipe and it was 0. I moved it to the left rail and got the reading of .359 and then moved it to the right rail and got the reading of .369. I then turned the machine off and tried again but this time I put the bit on the edges of the pipe rather then the middle. Bit on right side of pipe and got the readings left rail .388, right rail .430. Bit on left side of pipe and got the reading .469 right rail and .446 left rail.
The end caps on the pipe are the ones that have a hole right in the center so I believe the pipe is centered correctly. What info is this telling you other then it is messed up :) Is there anything I can do to fix this?
Thanks

bergerud
11-06-2015, 11:17 AM
I do not think there is anything easy you can do to level the jig in the y direction. There is no adjustment built into the jig design. As for the other measurements, you will have to look more closely at the pipe itself and how well it is held in the jig.

aokweld101
11-07-2015, 07:38 AM
I had a problem of the same sort, I was using a drain plug with a hole in the center and wasn't centered right with the the pipe, make your end pieces, Dan showed me this and helped a lot I was trying to find the magical depth numbers and I went through 20' of pipe trying to do so.

sunmiztres
11-09-2015, 09:00 AM
I had a problem of the same sort, I was using a drain plug with a hole in the center and wasn't centered right with the the pipe, make your end pieces, Dan showed me this and helped a lot I was trying to find the magical depth numbers and I went through 20' of pipe trying to do so.

Thank you so much. I will give it a try. :)

bergerud
11-09-2015, 09:23 AM
As an experiment I just cut a pipe holder out of MDF. I wanted to see just how true it would spin. I mounted it on the rotary jig and it was not as good as I would have liked. (I have the belt off so I could spin it.) I think that this is a problem. We have to design better way to hold these pipes. I think the holder needs a fool proof centering feature. Something like a recess which fits over the drive wheel or a snug fit pin in the center. (Maybe we can also use the rotary jig itself to make it.)

sunmiztres
11-11-2015, 06:55 PM
As an experiment I just cut a pipe holder out of MDF. I wanted to see just how true it would spin. I mounted it on the rotary jig and it was not as good as I would have liked. (I have the belt off so I could spin it.) I think that this is a problem. We have to design better way to hold these pipes. I think the holder needs a fool proof centering feature. Something like a recess which fits over the drive wheel or a snug fit pin in the center. (Maybe we can also use the rotary jig itself to make it.)


That sounds great if we could come up with something to make it more reliable. How off was your readings when you used the pipe carrier 2?