A new scanner design using plastic tubing

[davidlandin]

Thanks very much for your important corrections! What appears to have happened is that I've drawn up dimensions for two sizes of scanner, and some of the pages for one size have got mixed with pages from the other size scanner. BAD NEWS

I am about to post revised and corrected images and sizes on the Instructables site. You will also note that there has been a modification at the rear of the scanner. I've added a D-shaped loop of tubing at the back. This to stop the tendency of the base frame to tip backwards when the cameras or platen are not attached.

If you have started making the scanner framework, follow this sequence -

1. the main thing is to work the dimensions starting with the width between the hanging Ts on the platen.
2. Work from this width to the width of the counterbalance frame.
3. Then go from the width of the counterbalance frame to the width of the counterbalance support.
4. Then go from the width of the counterbalance support to the width of the base frame.

Thanks again

David Landin

[jkn]

Hi David

Thanks very much for your important corrections! What appears to have happened is that I've drawn up dimensions for two sizes of scanner, and some of the pages for one size have got mixed with pages from the other size scanner. BAD NEWS

No problem, glad the info was useful. I will keep an eye out for the modified instructable.

I am pretty 'handy' in general and expect to be able to make a few tweaks etc. myself, but you are right that it will be best to work outwards from the platen. FWIW I am thinking of having a larger platen angle than you (100 degrees instead of 90) so that will make a difference as well.

BTW, I am curious if there is any great art to drilling out the Tee-pieces for allow the tube to slide on? For 21.5mm 'overflow waste' tube I have a 20mm flat drill, but clearly using that will involve a bit of 'scraping' around the inside of the tee. I also windered about using a slightly smaller diamer tube and some sandpaper... would be interested in your experience of this.

FWIW I plan to use Canon a1400 cameras and a modified lighting arrangement, with four Cree emitters, maybe on a 'gantry' mounted on the top of the counterbalance support (where you have the sliding tee-piece currently. I am wondering if this setup, with a couple of metal 'arms' coming forwards, might result in a bit of light 'bounce; we shall see.

Cheers
Jon N

[jkn]

Oh, one other thing - I haven't yet seen the change with the D-loop, but something that occured to me re. weights and balancing:

Considering the (fairly small) weight of the cameras, platen etc. I was expecting the necessary weight at the back to be somewhat less than the 2x 0.5kg (ie around 2lbs) you have suggested. In any case, I was reminded of a scheme that I believe hot-air ballooninst used to use. They lowered a heavy rope out of the basket as they were sinking. As the rope hits the ground and starts to coil up, the 'effective' weight of <ballon + basket + weight of remaining unsupported rope> is lessened,
so that the basket slows down nicely, until it is exactly at rest...

So my idea was, instead of fixing weights to the rear of the counterbalance, instead attach a length of chain to each corner. Wtih a chain of 'suitable weight' (*) you should then be able to achieve a nice dynamically balanced system.

(*) This might well not be feasible, considering the weight required and the small height available. But I thought it was worth throwing out the idea anyway.

HTH
Jon N

[davidlandin]

Hi Jon
The new Instructable revised version is now up on the Instructables site
http://www.instructables.com/id/Book-Sc ... ges-an-h/.
Let me know if you spot any other errors please. I feel bad about the errors you found, but really glad you pointed them out!

FWIW I am thinking of having a larger platen angle than you (100 degrees instead of 90) so that will make a difference as well.

The problem with "unusual" angles is how to hold the acrylic accurately at that angle. With 90 degrees it is easy of course, as there are lots of 90 degree fixings. I'll be interested to see how your plan works out.

BTW, I am curious if there is any great art to drilling out the Tee-pieces for allow the tube to slide on? For 21.5mm 'overflow waste' tube I have a 20mm flat drill, but clearly using that will involve a bit of 'scraping' around the inside of the tee. I also windered about using a slightly smaller diamer tube and some sandpaper... would be interested in your experience of this.

I used a 22mm flat drill, and it worked well. I think you'd be better buying a 22 mm bit if you haven't got one, because even doing it by drilling out took me quite a few minutes, and I reckon with sanding you would be really struggling.

FWIW I plan to use Canon a1400 cameras and a modified lighting arrangement, with four Cree emitters, maybe on a 'gantry' mounted on the top of the counterbalance support (where you have the sliding tee-piece currently. I am wondering if this setup, with a couple of metal 'arms' coming forwards, might result in a bit of light 'bounce; we shall see.

I have found that mounting the light vertically over the gutter seems to be the best position. And I have had some problems with reflections, mainly (rather surprisingly) from off the black tubes, which are shiny even though they are dark in colour. I think this problem will best be handled by lightly sandpapering the tubes.

Please let me know how you get on. If you have questions as you go along just ask, but I will be away for 3 weeks starting next week, and I don't know if I will have broadband where I'm going. So you might have to wait for answers . . . . And you might be finished by the time I get back!


David Landin

[jkn]

Hi David

The new Instructable revised version is now up on the Instructables site
http://www.instructables.com/id/Book-Sc ... ages-an-h/.
Let me know if you spot any other errors please. I feel bad about the errors you found, but really glad you pointed them out!

No problem, I'll take a look.

Regarding the platen angle of 100degrees (say), I have a couple of plans:

• use small metal brackets, as some have done, and bend them out slightly to the desired angle
• Saw 'slots' made in some thin wood sheet at the correct angle, and fit/glue the sheets into those. I had using Balsa wood in mind. This would be a bit similar to how Daniel did/does it, on the early scanners at least, with triangular 'infills' of wood.This would also mean you could support the platen sheets higher up, I don't want them to 'flap around' too much ...

BTW, you are right about the postage costs of acrylic sheets in the UK being exhorbitant! Annoyingly my local plastics supplier doesn't sell the anti-reflective stuff ...

Thank for the note re. using a 22mm flat drill. They are very cheap (less than 1UKP) at Screwfix/Toolstation, but I will probably experiment first. I have a proper pillar drill which might make using the 20mm bit to 'scratch out' the tee piece easier for me...

Thanks for the comments about lighting. My 'gantry' arrangement would attempt to keep the lights over the two sides of the plante. And yes, I had thought about lightly sanding the tubing to keep reflections down, seems a much easier plan than painting it. Steel wool is what I would probably use.

I probably won't finish this in the next three weeks ... I have most of the parts but I'm the kind of guy who also has a lot of projects on at the same time! I also want to get the SW and electronics fairly well sorted at the same time. I'll definitely keep you and others updated with my progress.

Regards, Jon N

[davidlandin]

Regarding the platen angle of 100degrees (say), I have a couple of plans . . .

Hi Jon

One other factor that comes to mind if you decide on a wider 100 degree platen, and that is that you will also need to make your book supports to hold a 100 degree open book. I wonder if you have thought about that?

The advantages with a 90 degree angle include: ready made 90 degree fixings for the platen, and ready made 90 degree angle bracket book supports that, when inverted, hold the book at a 45 degree angle. Also from a book preservation point of view, librarians prefer minimal opening to prevent damage to the spine of the book. So in general they would prefer 90 degrees to 100 degrees - or much worse from their point of view - a flattened book! I'm working with books that do require careful handling, so 90 degrees is good for my needs..

If you do decide to go for the wider angle, I'll be interested to hear how you tackle the construction problems!

David Landin

[jkn]

Hi David

One other factor that comes to mind if you decide on a wider 100 degree platen, and that is that you will also need to make your book supports to hold a 100 degree open book. I wonder if you have thought about that?

Yes of course - but that's easy. You use the same 90 degree brackets as before, but mount them a little distance away from the edge of the book supports. The distance can easily be worked out with 'trig'; I have done it once casually, will go through my notes again to be sure before cutting & drilling.

In the main I am scanning some of my own books prior to disposal; my leaning towards a figure of 100 degrees is purely based on readings elsewhere in this forum, and I'm not fixed on this yet. Nice HB books with sewn signatures etc. are nicest, of course...

It would of course be possible to cater for both 90 and 100 degree platens if I make the frame for the wider one; you'd have to have a new platen and pair of book supports I guess.

Oh, in case anyone else is making a similar scanner with UK/metric tubing etc.; I can report that 18mm 'wardrobe rail' tubing is an exact fit inside the 21.5mm waste overflow pipe; it could have been made to fit. This sort of tubing (usually chromed) is reasonably easy to buy in DIY shops etc.

Cheers, Jon N

[davidlandin]

Yes of course - but that's easy. You use the same 90 degree brackets as before, but mount them a little distance away from the edge of the book supports. The distance can easily be worked out with 'trig'; I have done it once casually, will go through my notes again to be sure before cutting & drilling.

Mmmm Hmmm clever and ingenious. All the best ideas are simple and obvious - after someone else has discovered them! Well done!

It would of course be possible to cater for both 90 and 100 degree platens if I make the frame for the wider one; you'd have to have a new platen and pair of book supports I guess.

If you are screwing the platen sides together then you could just use different angle brackets (90 or 100 degree)

Also you could have two sets of holes for the 2 different angled book support positions . If you drilled with countersink holes from the upper side and used countersink bolts with wing nuts underneath. You could have two sets of holes - one for the 90 and the other for the 100 degree positions

Oh, in case anyone else is making a similar scanner with UK/metric tubing etc.; I can report that 18mm 'wardrobe rail' tubing is an exact fit inside the 21.5mm waste overflow pipe; it could have been made to fit. This sort of tubing (usually chromed) is reasonably easy to buy in DIY shops etc.

This sounds a very good find, because it will be a bit more rigid than the cheapo steel tube I used. Since its original use is for hanging clothes it must be strong enough to take bit of weight, so ideal for reinforcing the tubes.

Very good!

David Landin

[dtic]

A 100 degree bracket can be had with this method: take a regular 90 degree L bracket, screw one leg of it onto something sturdy (like a workbench), screw a piece of wood on the inside of the other leg of the bracket, slowly pull the wood to bend the bracket until it expands to 100 degrees.

[jkn]

Hi David

Yes of course - but that's easy. You use the same 90 degree brackets as before, but mount them a little distance away from the edge of the book supports. The distance can easily be worked out with 'trig'; I have done it once casually, will go through my notes again to be sure before cutting & drilling.

Mmmm Hmmm clever and ingenious. All the best ideas are simple and obvious - after someone else has discovered them! Well done!



Here's the trigonometry in case it's of use to anyone.
If: L is the length of one side of the bracket
and: phi is the desired total angle of the platen:
and: D is the distance away from the edge of the board support to screw the bracket;

Then
D = L*(tan(phi/2) -1)

as an example: if L = 9cm and phi = 100 degrees, then

D = 9*(tan(50) - 1), or 1.7cm.

As dtic suggests you can also simply bend the brackets; I'd match to an angle drawn with a CAD package or Postscript, and printed out on paper.

If you are screwing the platen sides together then you could just use different angle brackets (90 or 100 degree)

Yes ... although I had in mind gluing the sides together myself. Not sure that this is necessary

Also you could have two sets of holes for the 2 different angled book support positions . If you drilled with countersink holes from the upper side and used countersink bolts with wing nuts underneath. You could have two sets of holes - one for the 90 and the other for the 100 degree positions

Indeed.

Oh, in case anyone else is making a similar scanner with UK/metric tubing etc.; I can report that 18mm 'wardrobe rail' tubing is an exact fit inside the 21.5mm waste overflow pipe; it could have been made to fit. This sort of tubing (usually chromed) is reasonably easy to buy in DIY shops etc.

This sounds a very good find, because it will be a bit more rigid than the cheapo steel tube I used. Since its original use is for hanging clothes it must be strong enough to take bit of weight, so ideal for reinforcing the tubes.

Correction - the rail is actually 19mm diameter, not 18mm (I measured it with e non-plastic vernier )

Cheers
jon N