Build an Image Projector/enlarger From an Over Head Projector.

A warning before you start this. if you follow these directions on converting your overhead projector it will probably no longer work as an overhead projector. But on the major plus side you'll have an inexpensive image inlarger.
 
My main goal with this is for creating artwork stencil paterns and other such things. that and not paying $300 dollars for an enlarger from an art store.

Theres a couple ways you could modify a part so it could be used for both transparency and overhead projector probably of  course. so i might include that

tools/materials
Electric drill
# drill bit
#" philips screw driver
Locking pliers
 4-5ft long 7/8ths square steel tubing   or 3/4 aluminum  edging for plywood if using the original bracket the 4 foot long piece is good  5 foot would be need to attach to frame without the bracket and still be able to shrink the images.
wood
wool blanket.
#" double sided velcro
sewing machine.
overhead projector $20 at goodwill
wire caps
zip ties
  

If the pipe on your projector  is the same as mine you'll need to get a 7/8ths piece of square tubing. This is the first thing you need Do this before you do anything else or you realy are going nowehere fast.
there are a few companies that make the stuff. but i didnt get any response to my inquiries for a single piece of pipe.
3/4" angle iron joined with another piece facing it to form a tube is 7/8ths so i had planed on trying to weld two pieces together. a 7/8ths piece of pine is two soft and frnkly a bit flimsy any way  to take wieght of the head and to hold up to the roollers inside. Also it needs to cut pretty truly to not have the rollers loose there grip.
what I ended up using is this. A piece of aluminum edging 4foot long. Its a channel ment to be put over the edge of a 3/4" piece of plywood. I had intended on uning two of them.sourounding a piece of wood. cut 3/4" - 5/8"  4 feet long.  and to the length of the edging.  I was going to use two piece  cut of the excess and fit them together over the wood. I ended up using one instead. I had some scrap wood cut from a differnt project that fit perfectly so didnt feel like cutting off the exess metal. if I end up haveing problems I'Il go back and do that later
just put the edgin on your cut wood and test the fit on your projector head. Its a little tricky getting it in theres a sliding wedge that likes to fall out and mis algin itslef. you have to push in place and up to have enough room to ge the arm. (yours and the original)  If the fits to tight to roll up and down easily plane the wood thiner or sand to fit (only use a planer if your planer will take of paper thin shavings) be careful if you make low spots it wont grab and you'll have to start all over again. Smooth the wood with some fine sand paper. dont take of much wood your just making a smoother surface here.
once i got the fit righ and snading done i rubed a little parfin wax on the back of the wood to act as a lubricant
 add a screww to at least two points throught the metal into the wood. if you couneter sink the holes for a scwerhead to fit in you"ll have eonugh clearance to get all the way to the top of the. the second spot will have parto the bracket on it so you dont have to worry about the second screw right now. If you want to glue it in i have no problem with other than that i dont know how long the aluminum will hold up against the steel roller and if the glue changes the thicknes you have more work to do thining it out. again.

Open the projector and remove the glass plate.sliding it out. you can save this for later for another project, or keep it around so you can use the projector as a light table for tracing. etc.
Undo the screw on the arm above the lense assembly remove the head. be carefull its got some springs and other parts that can fall out. set it aside.
If i rember this right you need to remove the front of the projector to remove the mirror and the plate its atached to. I started this project up to a year ago??.. Couldnt find a 7/8ths piece of square steel pipe so it all got put on the back burner.As so many things do.
but back to the task at hand.
you'll need your drill. and a bit about an 1/8th inch minimum would be my guess, or a dremel and an appropriate dremel bit if you perfer.
 open the door on the bottom of the projector. Pull the power cord out of your way. Take your locking pliers and unscrew the nut holding the mirror in place.
While the projector is still on its side take your #" philips head screw driver and insert it in the holes on the bottom of the projector and unscrew the two screws holding in the top of the mirror. you should now be able to remove the mirror.the next part for you to remove is the sheet metal the mirror was attached to. To do this you need to take your drill bit and drill and carefully drill out all the rivets that are holding the sheet metal down. once youve done this you have to remove the front of the projector.
next you will need to take the front of the projector off. There are 5 screws holding mine in place.
you should now be able to remove the sheet metal from the projector. if not double check all the rivets are loose.


   This is important because it gives you a place to put your images or objects you want to project.

Now to disengage the safety feature. it has an interanal switch so that in only runs when the lid is down and locked in place. mostly for when the bulbs are being replaced I suspect. that and general opinion is that hot metal and hands dont mix..
remove the five screws form the back,and the screw on top. as well. (im not sure if they were in any way holding the back on but i had a moment of trouble geting the back off so i took them out.
Pull the back off. unclip the wires from there conector and set the back to the side so you can work.
Unscrew the two screw holding in the safety switch box. open it up.  unscrew and or cut thewires leading into it. Strip the ends of the foru wires.   Now pull the power cord out of the machine> detach the gorund wire save the screw thats holding it in. Now on the back panel in the bottm right hand side you should have a nice open spot with nothing behind it. drill a hole big enough for the power cord to go through. Slip the power cord through feeding in its wires first. Tie it into an overhand knot with enough  length to reach the other wires when you reconect it, but not so much that it takes up excesive space in the machine. pull the wire connector from its slot on the insed of the machine. pull the panel apart slightly and feed all the wiresto one side making space on the bottom for you to put your images etc.  

Youll be using a straight piece for your arm for this projector.  so you have to reposition the bracket. Now if you dont want to use/reuse the bracket thats fine. you can even improve your enlargemnt potetnial if you atach the arm differntly anyway. The basic thing here is to put the arm up on the machine and with a straight edge mark on the side panel where the arm should now go
You can see from my ruller its about 5-1/2" from the edge. 
Remove the cover on the bracket that holds the arm in place. take the arm off. be careful if you havent remove your lense assembly.You dont want to damage it.
Undo the bolts holding the main part of the bracket from the inside. the back of the projector should still be off. an set off to the side at this point.
and remove the caryying strap. at this time also.
The bottom hole on this one is about 2-1/4" up   and the top hole is about 1-1/4 down it looks like. The little spec next to the ruler is  center punch mark for drilling the hole.
the holes should be drilled about a 1/2" over from where the edge of the arm is going to sit. the hole size should be at least big enough for the bolts to slide through. you dont want to much lateral wiggle. so if the holes youve drilled dont line up verticaly with brackets holes open this up with a  dremel or round file enough so that they fit but not allow to much wiggle.
reatach the bracket.
 Be careful not to damage any of the wires when drilling.
Once your brackets atatched undo the old orange support clip from the outstide. slip a small zip tie through tht two holes and tie down the wires that are loose inside. this is just to keep things cleanish.

it wont help you to repositon it as I found out. The original arm is offset the straight are sticks up off the machine when its down. I took the time to repostion my supporth thing retatch it offset the holes to keep it in the same basic alignment etc. so im including the 2 pictures i ive got of it any way. so Basicaly dont do this.  the secon pictue is the measur of the offset of the holes have.
but if you want to use the support which im going to repostion again at some point for myself any way. You need to take a boad or some similar thing and attach it to the body of the projector and have enough overhand to support the arm when its down.
this might however interfer with the Shroud later. im not sure. since i havent made either yet,

I dont have any pics of what i did here so. this image will suffice. 
The second hole up on the support arm is the one you want to make on your new support arm. the hole needs to be as big as the tube thats going to go throught it which is sittin above the arm in the pic. theres 4 thin washers dont lose em.
remove the shee metal pyrmaid thing of the supprot arm. put it on your new. I dont think this is necessary but i did it any way.
assemble the arm and attach to the bracket make sure it works.

you should have pulled your wires through the side of the frame when you disconected the safety switc. You should be looking at the insied and it should look like the first pic i hav here.
With a pair of wire caps. conect the wires from the power cord together. Black to black white to white. retach the ground wire to where it was before.
run a zip tie through the opening the wire conector went throught and bind the wires to it. the Picture with the screw driver show them bound with the zip tie this is how it looks like from the outside.  this should give enough clearance on the inside  to reinsert the light assembly/back of the projector.
Last Pic is of the inside wires zip tied to the machine with the holes from the orange suport

slide the Head onto the support arm.  lift it up. turn on the machine and deicde wether your shrininking or enlarging .
for shirinking raise the head all the way up and a foot or fwo from your surface. this will give you 2-3 times reduction you can see it on the door at about 2 inches.
 for enlarging to maxximum all the  way down and 20 or so feet away from your surface. which is around 20 times magnification. 6" inch screw driver was 10ft  long  on my wall.
adjust up and down for clarity.
this gets hot so be careful with your hands and be careful with what you put inside. the screwdriver was nice and toasty when it came out.
so thin plastics might distort?and warp? and othere things may brought to point of ingnition. so a word of caution.
my camera doesnt take low light pictrues all that well an it looked a bit better in person but, heres an old ninja turtle of mine hes missing his arms from all his battles with the shreder and was it the foot? who names a ninja clan the foot?

Alright so i mentioned a shroud earliar. I havent done this as of yet so I'll just explain the thinking. take a wool blanket.cut it into 3 to 4 triangular stirps or straght with the last foot or so taperd so as to fit around the body of the prajector and atach to the head.  rember you realy dont want to block the ventilation.
 Atach some adhesive backed velcro to the head of the projector. and sew or attach it to the wool shroud. this will make your image brighter and have less unwanted light from the  projector on your surface your projecting onto.
wool is naturaly fire retardnt and pretty opage so its a good choice. dont use something like a plastic tarp it can melt and burn and the thins stuff will be really bright still most likely. lose lose.

An Idont think i went into it. but for the support arm without the bracket.  a piece of wood the same thicknes that bracket is or as wide as needed for the base of the projector head to slip by the side of the machine all the way to its maximum depth. and drill a couple holes where you feel is appropriate through your suport arm and the projector body and atach the arm.You may feel or find that you need to make an angle cut on a piece of wood to fit the angled undercut on the side of the machine for  full support.
Id try to leave this movable or removable. as transporting anything thats 5 feet long and breakable is complicate.

And to modify this further to still use as a transparency projector you would have to cut the sheet metal the mirror attaches to in such a way that it can sliped in and out  with out binding on the edges. that or atach the mirror to some that will achieve the same end goal.

 thats about it for now i think.