WHEN: Most Friday evenings. TIME: 7:15pm.

11 June 2008

Economy board template scan

Defeated by the funnies of scanning, it steadfastly refuses scanning as a graphic (maybe the shine?). The scale is haywire but have something half workable after photostating. The print should measure 39mm mid point to mid point of the large 8mm holes.

The notes:

1.Masking tape the metal part of the PC board.
2.Plan your cut so the top right hand corner is used in each case. Minimises the number of cuts and is cost efficient as four boards come out one 150mm by 150mm board.
3.By all means add a bit more meat to the top but otherwise cut exactly on the line or even inside, it is such an exact fit in the case. The bottom left hand “tongue” can be lopped off if wanted, I left that there so the template outline can be used for other trigger combinations.
4.The original board locks in to the case, if there is wobble then one screw in the region of the brake stop (or the brake stop bolt itself) can fix the board to the left hand case – no others needed.
5.Eight mm for the main holes, 2.5mm for all the trigger related bolts and 2mm for the top two holes holding the wiper pad.
6.Use two RC servo mounting eyelets as the ideal spacer to bring the wiper pad up to the height of the wiper.
7.Score the two lines through the metal to break the contact surface in to brake (red) / throttle (black) / full (white).
8.Remove some of the board metal surface around the left hand wiper pad screw, under no circumstances should the “brake band” on the wiper pad be live, only the brake stop, as there is no dead band facility on the wiper pad.
9.A small part of the case top will have to been removed to all the resistors to peek out the top..

Assemble, fit pots to the case and connect up and ready to race.

Reference item 7. If one wanted to use a stock economy mechanism without stops, then the first band after brake is left dead and the brakes connected to the brake band. One then only has an 11 band controller for the throttle portion.

09 June 2008

Parma economy template for template ;-)

Costa was looking for an economy base template, along with Janet and John instructions, and myself keen to oblige whilst building Gordon’s controller, only to find I was out of fibreboard and had to resort to the reversed off-cut in the pictures, to form a “template for a template” when new board is obtained this week. It only needs 6 mm along the top edge for the final product, which has been trimmed to minimise cost and also revert back to mounting the two potentiometers in the case, a much prettier solution than the “all hang out” approach I took with Phil’s economy.

It also serves as a test for ultimate in simplicity, building the whole project with 2.5 mm nuts and bolts, a size at least easily available locally. The final product ended up such a perfect fit that it does not even need a bolt to hold it to the left hand case. The blow by blow, after the board is cut out with Dremel and drill:

1. Leave the existing brass tube in the trigger and simply Dremel out a notch at the bottom, including the brass tube, to allow just enough room for the anti wobble nut, which locks the 2.5 mm trigger bearing bolt to the base board.
2. Take two flaps off old braid holders and super glue one each to the front and rear of the trigger, where the trigger will contact the stops. Dead easy although I went a bit further with some nice K&S thin shim sheet from Denkit – cuts with a pair of scissors.
3. Fit the trigger bolt and any wobble nut and slip the trigger on. The tube top normally just a teeny bit longer than the width of the trigger.
4. Very carefully wind on two 2.5 nuts to lock each other and allow the barest of slop up and down. I have used two nuts on my favourite controller for ages with no problems but by all means use a 2.5 mm Nylock nut instead if you wish.
5. The trick is that the trigger should only miss the base board by 0.5mm if you spin it, so careful with the notching in 1 and fine tune with thin washers if needed. Much more than a 0.8 mm gap and it will foul the case.
6. Bolt in the three 2.5 bolts for the stops and spring.
7. Now the part that requires some care – removing all the inside case pimples in the left case that would foul the board, along with opening both case sides in the trigger bolt area, so that the bolt and nuts just clear. I started with side cutters, followed by a Dremel with a 3mm drill bit for the trigger area and Dremel disk for completely cleaning off the pimple areas.

Erlo will quickly tell you that the 2.5mm bolt is a slop fit in the trigger tube but actually not much more than the standard economy frame and much less than the Ninco conversions from the old days. I would guess the spring pressure one way and the wiper pressure at 90 degrees actually keep things quite workable – time will tell.

The last step on the final template will be the two holes for mounting the wiper pad and obtaining the right size drill for the two large holes, my Dremel effort is ok but not that neat.

Lance also has some fancy Professor trigger bearing kits if one wanted to open the trigger hole and go for glory.

04 June 2008

Bridge Rectifier Controller circuit

The blog is the ideal place for storing useful technical info so I don't phone three people on a Saturday night for the diode polarity in a diode throttle and still assemble it backward (the silver band to the slow side, by the way ;-).

The circuit below is the popular Newcastle Full Throttle bridge rectifier version and, whilst simple, it is easily forgotten and a new project is shortly underway. In this case, it will feature six instead of five bridge rectifiers previously used for metal cars, with the two closest to full being switchable per the drawing, thus offering six sensitivity settings and usable from lead Scalex (6) right through to the hotter old fashioned specials (5).
A spare bridge rectifier was then used for the brake, similarly wired with the red brake cable going to switch "off" centre tap, neg (-) to the brake band plus one switch "on", and pos (+) to the other "on" switch position. Redundant by current use as way overkill and a better spread is obtained by potentiometer or rotary switch with 1amp diodes.