CAD Hooptee - Back from time warp

[johnbyrne]

Seems the original thread was lost in the crash.  Thus, here it is again.  The attached PDF files include the plans and a full sized scale pointer sheet that needs to be printed on legal sized paper.   

How to print the Scale/pointer full size
1.  Open PDF
2.  Got to file and then page setup
3.  Choose legal and click ok
4.  Got to file and then print
5.  Under page scaling choose 'NONE"
6.  Insert legal paper in your printer and print away

 

[johnbyrne]

Here are a few pics for your viewing pleasure.  First is an original (the original perhaps).  The next few show the beta unit. 

I ran out of 1/8" play (grrrr) so I used Plexiglass for the front.  It was thicker than 1/8" (3/16" I think) so I couldn't use the standard 3/4" wide backer.  What I did was simply measure back from the front such that the middle of slot A was at 1" and went from there. 

I left the base square.  The plans show it like the original but obviously it can be made square.  The base is 3/4" "sandy" ply from Home Depot and the 1/4" pieces are hard wood from again Home Depot.  Found these in the molding section by the wood dowels.  I added the cross brace as an after thought and it does help keep the prop down but isn't really needed. 

Back light the scale to see the gap between the prop and scale.  The last picture shows an APC 10x4 in slot D.  Pretty close.  I have an 11x5 APC that measures about 4.5 all the way down.  The first 2 slots (A and B) are pretty much useless due to the prop shape and the tip on an APC is almost impossible too.  The middle is pretty easy though. 

The prop mount is made like the original as circled on the plans.  I turned some hard balsa on my dremel.  Drilled a hole, inserted 4-40 blind nut (can be seen in the picture), screwed bolt through and chucked it.  While spinning I sanded it to shape.  SUPER easy.  The Cone can be threaded down onto the prop given the blind nut is still there so this works out pretty good.  The pointer is made of 1/16" ply and I think this may work better than the 1/8" on the plans.  It doesn't seem to need the bevel where it touches the prop.  I mounted the pointer with a wood screw.  The counter sunk type head removes all slop from the pointer hole as you tighten it down yet still moves nice.  It also stays where you put it.  Seems perfect but time will tell. 

[johnbyrne]

The writing in the slots was not easy and looks bad.  Thus, I made tabs on the scale/pointer sheet that you can cut out and glue in the slots for a more professional look.  When I get time I'll add them to this one to cover up my poor writing. 

I mounted the plexiglass first using counter sunk holes and wood screws.  I then glued the scale to the front.  Then the hole for the pointer was carefully drilled.  I say careful because it must be in the right place but also because the hole is pretty close to the surface of the base wood.  It was suppose to have the 1/4" by 3/4" piece above it but this one doesn't.  There is enough wood there but you don't want to drill at an angle or you could come throught the top of the base. 

The scale is glued on using 3M spray adhesive.  It is not the 77 type but the lower numbered (and cheaper one).  I think it is 45 but I'm not sure off the top of my head.  I plan on putting some of that clear contact plastic over the front to protect the scale but have not done it yet.

[johnbyrne]

Yet one more thing

Prop mount - I did installed a 4-40 blind nut on the bottom of the 1/8" plate (what prop sits on) and then glued the 1/4" piece onto it (what rides in the slots).  The blind nut sticks out slightly on either side give it is wider than 1/4"  and as such hits the top of the rails.  Thus, the mount would not sit all the way down onto the rails causing a "rock".  I had to slightly bevel the edges of all the rails for the prop mount to sit flush.  Hope I explained that where you can understand.  Let me know if not and I'll add some pictures.