THE TURNOGIVE !

Michel Demey's Descon-13 Entry

Batten down t' hatches: this thin' is nay flyable!

What is it? An automatic device that can cut an ogive from Styrofoam... Arrr! Ya scallywag!

I was t' author o' a first device t' do that manually. Avast! Blimey! It was described in the Apogee newsletter o' August 2002.

It used two identical templates and a hot wire t' make ogives. But this first try had a problem: New templates had t' be made for each size. And I don't like t' make templates. Avast, me proud beauty! Blimey! A new idea had t' be found.

Here it is!: this new model is motorized and automatic. Begad! Begad! Nay very fast, shiver me timbers, but you can let it work and meanwhile read t' last Apogee newsletter... And it is adjustable.

T' little inconvenient is that t' only shape it can make is an ogive. Avast! Blimey!

General view

How it works?

A hot wire saw is mounted on a pivotin' arm that is moved by a first motor coupled t' a threaded rod.
T' Styrofoam bloc is mounted on a rotatin' plate that is powered by a second motor. Aye aye!

T' blue plate be t' base, with five small feet, one at each corner and one in t' center. Avast, me proud beauty! It is a square 600*600 mm made from 9mm thick plywood.
There are three main assemblies:

• T' rotatin' arm with t' hot wire saw is at left. Blimey!
• T' rotatin' support o' t' Styrofoam block is in front. Well, blow me down!
• T' motor for t' arm is behind, with t' threaded rod. Blimey! Aye aye!

T' size o' t' machine

Assembly 1: T' mechanism used t' rotate t' Styrofoam block:

All t' ball bearings used t' build t' machine are found in rollerskates. Ahoy! You can buy them by pack o' 8 in any good sport shop. Ahoy! T' outer diameter o' t' ones I found was 22mm. Aye aye! Inner diameter was just 8mm, ideal for a threaded rod. You guessed: all t' bolds, shiver me timbers, nuts, threaded rod are o' 8mm.

Find your ball bearings, matey, and buy all t' rest with t' inner size o' them. Avast, me proud beauty!

T' stepper motor is o' unipolar type, found in an old matrix printer. Unipolar motors are t' easiest t' drive. Well, blow me down! Blimey! I will describe later t' electronics used t' drive t' machine. Well, blow me down! Blimey! It is intended for unipolar motors only.

How t' know if you have an unipolar motor in your hand? There are 5 or 6 wires.

T' stepper motor is coupled t' t' threaded rod with a small piece of flexible plastic tube. Ahoy! This is also t' easiest way t' do that. Begad! Ya scallywag! Gears or pulleys could be use, shiver me timbers, but believe me, arrr, it is harder.

T' block mechanism is nay fixed t' t' base. Arrr! It can move laterally, t' put the hot wire at t' correct position for t' size you need. Ya scallywag! Begad! It is maintained in place with a screw clamp.

Assembly 2: t' arm.

You can see two little wheels at the movin' end o' t' arm. Arrr! This be t' best, me bucko, but is nay absolutely necessary. Begad! Aye aye! My first version, matey, that worked, me bucko, shiver me timbers, used only two blind nuts that slipped on t' base. Begad!

T' hot wire holder must have a system t' tense t' wire. Blimey! Blimey! Begad! Blimey! Blimey! Blimey! See t' pictures for an example o' how t' do it. Ya scallywag! Blimey! You can find interestin' information about hot wire cutting, matey, shiver me timbers, power supply, etc on t' web.

Assembly 3: t' arm motor box.

Since t' arm end moves, ya bilge rat, t' threaded rod motor holder must be able t' rotate. T' arm motor box has only one ball bearing. Well, blow me down! One bold hold it t' t' base. Arrr! Blimey! Another holds it t' a sort o' bridge that covers it. All this mount is nay glued t' t' base, me hearties, because I was nay sure o' the final position. Avast, me proud beauty! Ahoy! In fact, it will surely be in a different place dependin' of the size o' t' ogive made. Avast, me proud beauty!

Last details

the movin' end o' t' arm I used a simple nut t' drive t' arm. Begad! It would be probably better with a coupler, but a nut works. Avast! It is soldered on t' head o' bolt. Arrr! Ya scallywag! T' whole must rotate. On this detail view appears t' end o' course contact switch, me hearties, that reverses the motion o' t' arm each time it is activated. Avast! Blimey!

the movin' end o' t' rod T' end o' t' rod moves from left t' right. Aye aye! Well, blow me down! I chose t' put a ball bearin' thar also. If not, all t' rod weight will be on t' nut that drives t' arm, arrr, which isn't very good. T' ball bearin' rolls one a little wood block, me hearties, and you must carefully adjust the height o' t' block t' assure that t' rod is perfectly horizontal. Begad! Well, blow me down! Adjust also t' nut o' t' arm t' align t' whole. Ahoy! Avast! T' width o' t' block should surely be adjusted if another size o' ogive is made. Blimey! Don't forget it.

Electronics

Motor driver

Power supply for t' two boards can be done with a 12V battery. Well, blow me down! Aye aye! Keep your adjustable supply for t' wire

How to connect t' motor wires?

1. There are 6 wires, matey, formin' two circuits o' three wires. Aye aye! First identify the two circuits. Avast!
2. Choose one wire and connect it t' your ohmmeter. Arrr!
3. Find three other wires that have no connection with t' one you chose. Begad! Avast, matey, me proud beauty! Mark them: this be t' first circuit. Blimey!
4. ... Avast, me proud beauty! t' three others are from t' second circuit, o' course!
5. For t' first circuit:
   1. Choose one wire and connect it t' your ohmmeter. Avast! Well, blow me down! Blimey!
   2. Check t' resistance with each o' t' remainin' wire. Ahoy!
   3. If it be t' same, t' wire you chose be t' center. Avast, matey, me proud beauty! Mark it. Ya scallywag! Ya scallywag!
   4. If not, choose another one. And repeat until you find t' center. Well, blow me down! Avast, me proud beauty!

Left and right seems t' have no importance. Begad! If you exchange them, shiver me timbers, t' motor turn in t' opposite side.

Build t' circuit on a striped board:

Driver o' t' driver (flip flop)

• rev and turn t' t' driver that controls t' threaded rod motor
• step t' t' driver that controls t' block motor. Arrr!