I tore my Reetz Hackerspace scanner down this morning, sanded all the pieces, painted them black, and reassembled this afternoon. It seemed like a good opportunity to jot down some notes that might help others and also to create a rudimentary fastener list.
If and when you take things apart before spraying the individual parts black, Iâ€™d like to suggest that you break all the edges with 100 grit sandpaper. The trick is to just swipe all the sharp edges of the plywood once or twice. It rounds them over just a snit so no one will hurt themselves or catch a splinter.
As for glue, I donâ€™t think the project needs it. I made one exception: where the front lifting arm attaches to the side arms left and right, I used some liquid nail adhesive. Iâ€™d seen the shock cords put some torque on this joint and watched it begin to open up during trials. Liquid nail is one of those caulk adhesive sorts of things thatâ€™s gap filling to the max and wonâ€™t crack. I suspect that regular glue or caulk would work just fine here, but it does make sense to glue this one area. The rest of the machine is complex enough that I might want to take it apart, so I simply bolted and/or screwed it together.
1/4 X 20 Carriage bolts. I used 20 @ 2 inches, 4 at 2.5 inches, and 2 @ 3 inches. The longer ones give the shock cords and pulleys an area to clip or bolt to. Carriage bolts are quite cheap. Their thin heads donâ€™t take up much space in confined areas and you donâ€™t need to hold the head with a wrench while driving the nut. Most folks despise carriage bolts but I think they have their place and this seemed like one.
At least 40 washers for above. You need less than that but if youâ€™re like me some will remain lost forever underneath the tool box...You need these guys everywhere, put one between every nut and bare wood. You also need a bunch for the moveable joints.
An aside. About those joints. Hereâ€™s a crude sort of section of a typical joint that may help to explain whatâ€™s going on. It took me awhile to figure it out for no particular reason. Maybe this will help.
At least 40 nuts, 1/4 X 20. Here again are a couple of extra. I built my machine also using a number of locknuts, the type with the nylon inserts. Iâ€™m thinking this made life harder.
Turns out that the force required to drive one of those nylon locknuts will easily strip a carriage bolt head in plywood if youâ€™re not extra careful. If I build the machine again Iâ€™ll just use all regular nuts and a small tube of lock tight - the type that allows for disassembly.
Six 1/4 X 20 connecting nuts. I used these to cover the threads of the longer carriage bolts wherever the threads might get bunged up from shock cord hookage. Hereâ€™s a picture of my arrangement.
About those shock cords. Be a bit careful when hooking and unhooking them. Itâ€™s easy to let go of the wrong end. I suspect that just a few different shock cords will be needed and Iâ€™m thinking Iâ€™ll close their hook ends with pliers. To put one on, you would just then unscrew the wingnut, pull off the washer (yeah, thereâ€™s an extra nut in the picture, sorry) slide the shock cord eye on, then reassemble. I can just see kids messing with one of these machines unattended, playing with the shock cords, and the next thing you know...
Iâ€™ve made a couple interactive displays for a local museum and am always surprised at the creative uses some people find for parts of them...
I used eight of those sexy black allen head 1/4 X 20 bolts: Four at 2 inches to attach the top unit to the bottom, two at 1 inch for the camera mounts, and two at 1.5 inches for my trigger axles. Yours may need to be longer. I narrowed my trigger housings for fun.
Four number 10 pan head sheet metal screws at 1 inch to serve as axles for the book carriage ball bearing wheels.
Youâ€™ll probably need a foot long section of 1/4 X 20 threaded rod for however you decide to fabricate a handle. I think Gary used a section of PVC pipe, threaded rod, and wooden washers. I used some bike tubing at 22.5 mm, the threaded rod and a couple of washers I made.
A small assortment of number eight flathead woodscrews. I use the type requiring a square drive. I used four at 1.25 inches to attach the base crossmember to either side, six at 1.5 inches to assemble the top light box, four at 1.25 inches for the camera cross members, and four at 2 inches for the lower cross members. Youâ€™ll probably need a few others.
Hereâ€™s how I put the top section of the scanner together. It consists of two â€œplatesâ€ held together by two types of cross member. The upper cross members hold the cameras, whilst the lower ones are simply structural members. In all cases, I screwed through the side of the plywood â€œplateâ€ and into each crossmember, making sure I drilled a clearance hole through the plate first. The camera crossmembers are easy, come down from the top here:
The lower crossmembers are a bit trickier, but here I suspect youâ€™ll find the best approach is from the inside with a longer screw, like this:
If you should split the endgrain of the plywood crossmember, donâ€™t worry. Youâ€™ve just created a slick woodworking joint called wedged tenon. Put a little glue on a sliver of wood and jamb it in, shoot a little black spray paint on and no one will ever know. Theyâ€™ll think itâ€™s just another plywood veneer....
I used a number of other fasteners for attaching lights, etc. but these are going to vary for each build. I haven't mentioned a few wingnuts for joints that come apart more frequently, also a few fender washers, but I hope you get the drift.