PVC pipe scanner with 100 degree platen

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Doranwen
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PVC pipe scanner with 100 degree platen

Post by Doranwen »

I decided to start a new thread for the actual build because the old thread was really long and a lot of speculation and ideas. My brother is here and is working on it, and today completed an initial frame for the platen. (See attached photo - from before he added the T brackets.)

He's come up with the following:

- PVC pipe-based but with wood elements (we have some basic carpentry tools available and a barn to work in)
- glass platen
- 100 degree angle
- frame around the outside to hold the glass in

What we're still trying to figure out:

- how to deal with the glass edges (which are very sharp) so they don't damage the books (so far the idea is to take the panes to the glass store just down the road from my house and ask them to smooth out and round the edges that would be pressing against book pages)
- the best way to attach wood to PVC (an adhesive? he's using an alternate method of supporting the frame in front due to the wood frame around the glass, and needs PVC pipe to be supported by blocks of wood)

Fortunately Home Depot is less than 15 minutes away from our house.
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cday
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Re: PVC pipe scanner with 100 degree platen

Post by cday »

Doranwen wrote: 23 Jun 2021, 00:41 I decided to start a new thread for the actual build because the old thread was really long and a lot of speculation and ideas.
Excellent idea... :D

My brother is here and is working on it, and today completed an initial frame for the platen. (See attached photo - from before he added the T brackets.)

He's come up with the following:

- PVC pipe-based but with wood elements (we have some basic carpentry tools available and a barn to work in)
- glass platen
- 100 degree angle
- frame around the outside to hold the glass in

What we're still trying to figure out:

- How to deal with the glass edges (which are very sharp) so they don't damage the books (so far the idea is to take the panes to the glass store just down the road from my house and ask them to smooth out and round the edges that would be pressing against book pages)
Are the two glass sheets free to slide within the frame? If so, from memory of my drawings in the original thread, there are two possible ways in which sheets with a square edge could be positioned relative to each other. If their relative positions are fixed, could you say how they sit relative to each other, and if necessary post a basic sketch.

Given that information dpc who has built scanners with glass platens can no doubt give useful advice.

If needed you could also, of course, consider whether the glass edges could be profiled economically and in your tight time scale, so that they could be positioned to form a 'V' shape which might be easier to smooth to avoid the risk of damage to the pages.

- The best way to attach wood to PVC (an adhesive? He's using an alternate method of supporting the frame in front due to the wood frame around the glass, and needs PVC pipe to be supported by blocks of wood)
It would be easier to comment usefully with more detail of the construction, in general drilling holes and using screws or bolts if that is practical should be sure-fire, otherwise some research online into different adhesives would be useful. Maybe, without checking, an epoxy adhesive?

Glad you're underway at last!
Doranwen
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Re: PVC pipe scanner with 100 degree platen

Post by Doranwen »

Another day, another update. Unfortunately my brother's already gone off to bed - he has much less interest in updating you all than I do - so my attempts to explain his thoughts and whatnot will be something like a computer newbie attempting to explain to one computer geek what another computer geek is doing. Please pardon me if I'm unclear or confusing, lol.

My brother called the glass store, and they can totally smooth out the edges for us, they say, so I'll be taking the panes in to get one edge on each smoothed out nicely.

The PVC/wood combining I was asking about turns out to be the PVC pipes of the bottom frame resting on wood supports, and he's planning on drilling down through the PVC pipe and just screwing them into the wood.

Today the general frame structure with PVC pipes was assembled (no gluing yet, got to get it all assembled and working first). He spent a lot of time in calculations, as the limiting factor here is the space I have to put the scanner in. We are really maximizing that, and he's modifying the counterbalance arm shape (having it curve and go down instead of straight out like in the original design) to have it be as compact as possible while still allowing enough room to easily swing the platen out of the way to turn pages. You can see some of that in the picture.
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dpc
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Re: PVC pipe scanner with 100 degree platen

Post by dpc »

The PVC/wood combining I was asking about turns out to be the PVC pipes of the bottom frame resting on wood supports, and he's planning on drilling down through the PVC pipe and just screwing them into the wood.
That'll work. You could also put an inline PVC 'T' fitting there (with the leg of the T pointing down) with perhaps a short piece of pipe in the T leg to get the right height off the table. Scrap 2x4 is probably cheaper though.

We are really maximizing that, and he's modifying the counterbalance arm shape (having it curve and go down instead of straight out like in the original design) to have it be as compact as possible while still allowing enough room to easily swing the platen out of the way to turn pages.
I'm not sure why you need that downward turn in the piping on the counterbalance side of the arms. The reason why the arms extend behind the pivot point is so that you won't need to add as much weight to counterbalance the weight of the platen. Shortening that length by turning downward decreased the mechanical advantage of the lever so you'll need to hang more weight on that cross member to compensate. BTW, you don't have to use weights for counterbalancing the platen. You can use bungee cords or extension springs.

(no gluing yet, got to get it all assembled and working first)
Wise move. Do yourself a favor and once you have everything fitted, mark the joints with a Sharpie so that when you pull them apart you'll know how to rotate the various fittings with glue on them to get them back into the correct orientation so that your framework is square. Also realize that your PVC cement might cover your alignment marks, so either use a long mark that extends past the glue area or just don't put glue on the pipe near the mark (you aren't making a watertight seal anyway). If it were me, I wouldn't even glue every joint. Look at which joints will have the most stress on them and glue those, but make it so that you can break down the pieces so that they will all fit into a box for storage. Sounds like space is a premium in your place.

Thanks for posting your progress. Always good to see how builders progress and work around unique design constraints.
cday
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Re: PVC pipe scanner with 100 degree platen

Post by cday »

Regarding cementing the pipes in place when ready:

The tube I was looking at last was described as being a firm fit into couplings, so you might not even need to glue them. The pipes in your photo look a lighter colour, though, so that might not be so applicable.

And there is also the possibility already mentioned to drill fine holes and insert small screws or bolts or maybe split pins, which would ensure that the design could be modified later if a need arises.

Although the original thread became very long, it might be worth reviewing at least the later parts quickly so as not to miss any potentially useful points.
Doranwen
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Re: PVC pipe scanner with 100 degree platen

Post by Doranwen »

My brother worked mostly on the cradle today, having had some difficulty getting a saw that could do the angled cut (he had to use a neighbor's). The picture below shows the cradle pieces completed, except for the adjusting for book thickness. Not shown is the frame to suspend the light above the scanner, which he also worked on today (I did a bit of sanding this afternoon on it, as it's made of wood).

He's going to use screws as much as possible, and thinks he will only need to cement the back of the rocker arm together. It has to be angled downward due to there simply being no space behind it before hitting the wall (you can see that in the picture in the previous post - there's a matter of only a few inches' wiggle room), so it will have extra weight attached to it. Alternatively, he's considered bungeeing it to a heavier weight below on the desk, which might be the easiest way to keep it in balance.

The current challenge my brother is solving is that the camera mounts he had me order are not as long as the arms in the original design, so he is thinking of ways to extend out for them to connect onto. Otherwise they wouldn't be able to aim correctly at the glass. (He's currently coming up with an idea involving all thread, nuts, wingnuts, washers… I'll see what he comes up with tomorrow!)

He thinks the construction's up to about 60-70% done at this point. (Mostly what's left is a lot of attaching mounts and other little things, and of course spray painting it all "flat" black.) It's exciting!
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dpc
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Re: PVC pipe scanner with 100 degree platen

Post by dpc »

It has to be angled downward due to there simply being no space behind it before hitting the wall (you can see that in the picture in the previous post - there's a matter of only a few inches' wiggle room), so it will have extra weight attached to it.

I still don't understand why the arms need to turn down at all. Why can't the cross member in the back be in the same plane as the arms (i.e. rather than the 90 deg. elbows turning downward, rotate them so they turn inward and then put a straight piece of pipe across the back)? There would still be the same distance from the arm pivot to the back wall.

In any case, why can't you slide the base piping forward on those 2x4 wood block legs and hang some of the frame over the front edge of your platform/desk? That will free up space behind the pivot. You could easily hang 6"-8" off of the front with no teetering issues because of your counterweight in the back.

A possible easy camera mount can be made by adding a PVC 'T' in the middle of each arm (can be off to one side slightly to facilitate the platen pivot screw), then attach a plywood plate with screws over the 'T' and arm. Drill a 1/4" hole in the plate for the camera mounting screw. You may not even need the plywood if your cameras are lightweight. Just drill through the leg of the 'T' (or a short piece of pipe out of the leg of the 'T') to attach your mounts. I can send you a crude sketch if the description above is confusing.

Once you get the cradle assembled, put a book on it, set the platen on top (doesn't need to be attached to arms), then get your camera out and figure out where you need to place it to get a nice tight photo of the page with no pin cushion or barrel distortion, THEN build your mount to place the camera in that location.
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Re: PVC pipe scanner with 100 degree platen

Post by Doranwen »

Another day of progress - you can see most of the scanner put together - the PVC pipe frame, the wooden light frame, etc. The platen was removed to do some work on it to make it less likely to "catch" as it settles back onto the cradle. You can see the light attached to the frame he built, which has slots (made with a table saw) so it can be raised and lowered as desired, fastened with wingnuts. (The frame is also adjustable forward and backwards as it is independent of the PVC pipe. I have it pretty much centered over the cradle though.)
dpc wrote: 25 Jun 2021, 10:36 I still don't understand why the arms need to turn down at all. Why can't the cross member in the back be in the same plane as the arms (i.e. rather than the 90 deg. elbows turning downward, rotate them so they turn inward and then put a straight piece of pipe across the back)? There would still be the same distance from the arm pivot to the back wall.
My brother says it started because he was trying to offer more places to tie weights onto, and then morphed into being much easier to have less distance from the arm to where it rests on the block he's using to connect with bungee cords. You can see the block in the picture below with the weights inside it. The idea is now that the block won't move (so it won't scrape the wall) but it's only got one bungee cord that will be wrapped around the rocker arm so the tension isn't too strong. The platen's resting state when attached to the rocker arm is on the cradle, so the effort will be to lift it for page turning, but it should settle back down pretty easily. Since I'll likely be standing to operate this (I'm medium height), I thought it would be easier to lift up towards me than to be constantly pushing something down (and hoping I keep it pressed steady enough while taking pictures). Better that the pictures happen while it's resting solidly on the book, and that lifting it off is where the effort happens.
dpc wrote: 25 Jun 2021, 10:36 In any case, why can't you slide the base piping forward on those 2x4 wood block legs and hang some of the frame over the front edge of your platform/desk? That will free up space behind the pivot. You could easily hang 6"-8" off of the front with no teetering issues because of your counterweight in the back.
Mainly because the entire space in this corner of the room is limited. Anything hanging far off the edges will limit walking and maneuvering. He has modified the pipe to hang down a tiny bit in front, but much more would make it far more likely to bump into it too much.
dpc wrote: 25 Jun 2021, 10:36
A possible easy camera mount can be made by adding a PVC 'T' in the middle of each arm (can be off to one side slightly to facilitate the platen pivot screw), then attach a plywood plate with screws over the 'T' and arm. Drill a 1/4" hole in the plate for the camera mounting screw. You may not even need the plywood if your cameras are lightweight. Just drill through the leg of the 'T' (or a short piece of pipe out of the leg of the 'T') to attach your mounts. I can send you a crude sketch if the description above is confusing.
I was going to show him this, but he wasn't accessible for much of the afternoon and I missed catching him this evening. I think he's figured out a solution, though. He's even figured out how to hook a "handle" onto the left side of the rocker arm to make it far easier to lift and move the platen (not completed in the picture though because he bought the wrong size part at Home Depot and will be returning that Sunday morning to get the right one), because with a few of the design modifications he had to make due to space constraints, it doesn't maneuver quite as easily as the one in the original video does. (Having to attach the platen via the T-brackets on the outside of the rocker arms was a major factor, I think. Inside would've been better, but there simply wasn't the space to do that with a platen as large as mine, and I needed the large size because I plan on scanning in quite a few larger-sized books. So he deliberately chose the order to work on the various parts because this would affect that and so on.) One modification made on my insistence was turning the pipe downward once it gets past the supports, so it's not in the way when reaching down to turn pages. With the really large books, I won't be able to lift the platen high enough to get it very much out of the way for page turning, so it may slow me down some. We'll see…
dpc wrote: 25 Jun 2021, 10:36 Once you get the cradle assembled, put a book on it, set the platen on top (doesn't need to be attached to arms), then get your camera out and figure out where you need to place it to get a nice tight photo of the page with no pin cushion or barrel distortion, THEN build your mount to place the camera in that location.
He's found ways to adjust the cameras and all that, I just can't ask him about it right now. He was working too much on it today to look at this thread when I remembered to check it, lol.

He won't be building on the scanner tomorrow but will be back to it on Sunday. I think that's when he's going to have me finish sanding the support blocks in the front and the counterbalance black in the back, and he mentioned possibly spray painting a bunch of it as early as Sunday afternoon…
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Doranwen
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Re: PVC pipe scanner with 100 degree platen

Post by Doranwen »

Today I did some spray painting, and we did much of the final assembly. The drawer liner is still on its way and won't arrive till long after my brother has returned to his home (in another state), and I still have to spray paint the cradle and the PVC pipe parts themselves, as you can see in the picture.

However, we have a major issue: the light definitely reflects, and it was impossible to get it NOT to. The platen angle being 100° definitely did not fix that. I'm wondering whether I need to see if the glass store has non-reflective glass and if that will help… My brother had the idea of turning the light *upward* instead of down, and affixing some sort of diffuser above to reflect it around and down, such as photography studios do. (Then comes the question - which diffuser? There are so many types sold out there…)
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dpc
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Re: PVC pipe scanner with 100 degree platen

Post by dpc »

The 100 deg. platen angle prevents the image of the adjacent platen pane from being reflected into the shot, not the light. In order to prevent the light from reflecting off of the platen you have to raise the height of the light over the platen and/or decrease your cameras' viewing angle by moving the cameras farther away from the surface of the platen. Decreasing the width of the light also helps (i.e. rotate the light 90 deg from what is in your photos).

Calculating the minimum camera and light distances from the platen is a rather straightforward trig problem. If you tell me the size of the largest page your scanner is designed to scan, the platen angle (100 deg.?), and the dimensions of your light source, I can tell you how far the light and cameras need to be mounted away so that the light isn't reflected when photographing that page size. Obviously the larger the page surface, the greater chance you'll see a reflection.

Regarding painting a scanner, you don't need to worry about any parts of your scanner that are beyond the platen glass. They can't reflect off the glass and show up in your shot. Any painting you do on those parts only benefits aesthetics.
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