The Homemade USB Gearbox

 

shortly after i started playing Test Drive Unlimited, i felt the need to get a good wheel with a clutch pedal and an H shifter... only to find that here where i live (Sao Paulo), a G25 comes out at about 1500 bucks (nasty import taxes here... dont get me started) -- about 700 US dollars

so if i couldnt buy it, i decided i would have to make one myself

after a few days (read weeks) of work, heres the final result:

(sorry about the low quality pics, this was taken by a mobile camera)

the concept behind this is simple: a USB mini keyboard does all the interfacing with the pc (you can see it's circuit board screwed to the front panel) and the gears are engaged by pressing one of the keys... the keys are then mapped in TDU... the big thing here is HOW those keys are pressed

this is the rear side of the gearbox (the side that faces the pc)
i'm not sure if you can make out the details from the shot, but in there is where it all happens

i extracted the main axis mount from an old joystick (brand unknown) which was exactly what i needed, a well machined moving part that can move in 2 axis (this is important to notice, precision parts are VERY hard to make... it's very difficult to make precision parts if you dont have precision tools)
the problem was that this part had long been separated from its parent joystick, which was nowhere to be found, so i had to build a U shaped support bracket, which would hold the mount in place and would be screwed down to the baseplate (too many parts already? dont worry i'll get there)

ok very good then... i had my center pivot point, and best of all, i didnt have to make it (that means it wont break down on me :p )... now i needed a proper gearstick...
altough you can buy real car gearheads out there, i found something here at home that suited the need perfectly... a kick drum stick from my band´s drum set, i'm sure they won't miss it.

the shaft fit perfectly inside the axis mount and i only had to cut it's lenght and make a small dent to lock it in the mount with a screw. that was some really hard metal! i took a lot of sawing ti get trhough it (and it made nice sparks too)

ok so now i had a perfectly working stick that moved around left-right and front-back as well... cool, but thats not a gearbox yet

now i needed to make a frame that would surround the gearstick-mount-bracket-device-thing and support all the other necessary parts

this i had to make from scratch... you can see it in the pictures as the metal corners that hold the whole thing in place... it consists of 4 L shaped metal columns and some metal strips riveted together to make the edges of a box, i then attached a wooden bottom to be my baseplate (now we're getting there :) )

the wood i use is mostly MDF, which is good to work with since it doesn't have fibers that it can crack along while sawing or sanding, the metal parts are mostly tin (i believe) and aluminum, which are easy enough to saw and bend (it's not a good idea to work with metals that are too hard for you to bend, saw or drill with your power tools) ...the wires came from a long net cable... these are good because they have 8 different color wires inside, plus the wires are a single copper strand, not a bunch of little annoying whiskers

ok so where was i? i had my frame ready, attached to a baseplate... i then screwed in the gearstick right down the baseplate centerline, and drilled some holes on the frame for the springs. (the springs were also taken from the unknown brand joystick)

now that's one of the reasons why i chose to make a frame instead of building everything inside a closed box, imagine how hard it would have been to try attaching spring to a box you can't see out the sides...
the springs link the frame to the axis mount and force the gearstick to return to center unless a gear is engaged, this happens because the springs are more extended when the gearstick is centered, creating the sitting-on-a-piramid effect... so when you push the stick forward or backward, the springs will tend to hold that position until you push it back out.

ok, now this was starting to look like something, but it was missing the most important bit... so far this is nothing but a stick in a cage, with some springs attached, now i needed to make that H shaped hole piece that separates the gear legs

i used a table saw to cut out this double H shaped hole on a single piece of MDF, first i drilled a small hole through the piece, then i detached the saw bit from the table saw... passed it trough the hole and then attached the bit back into the table saw... and did the same in reverse to get the piece out after cutting

to ensure this piece was as precise as possible (remember what i said about making precision parts?) i first drew it out in Corel Draw, making sure the dimensions were accurate, then i printed it out, and carbon-copied it onto the wood... its a lo-tech method, but it works for a semi-precise cut as this... i used a file later to shave off the imperfections, as using a table saw requires a pretty steady hand, a technique i haven't quite mastered yet

after that was ready, i attached it onto the top of the frame... this is where it becomes obvious why the gearstick must NEVER be glued onto the axis mount... how are you going to get that thick gearhead THROUGH the H shaped hole if it doesnt disconnect?

in fact, nothing in this build in glued... all parts are screwed on... this solves 2 problems: one that you dont need to deal with sticky messy glue, second i dont have any patience for watching glue dry... oh and never mind the adhesive tape :P it's just there holding that tangled mess of wires

ok now we have a decent mechanical gearbox that doesnt really do anything more than a paperweight... now i needed to make this thing go USB and tell TDU what gear i want to drive on...

i got this USB mini-keyboard that i promptly dismantled down to the circuit board... the circuitry works like a TV remote control or a calculator, the trails are split just below each key and a small metal thing is pressed down when you press a button, closing the circuit, and sending a keypress signal to the computer.
after understanding the somewhat complex circuit layout, wires were soldered down to the board, 2 for each button, creating parallel paths from where the circuits could also be closed.

this was the complicated part, because the circuit trails are VERY fragile and anything going wrong in this part, will render your electronics worthless...
i didnt trust myself to do this, so i called in the help from a friend of mine that has more experience in soldering on circuit boards... it's best to call for help before you mess up the single most important (and expensive) part of your project ;)

after the soldering was done, i attached the little switches by the side of each gear leg... this is a microswitch that is engaged by depressing a lever on its top so it worked perfectly for this aplication...
i needed to go out and buy these switches... you can find them in electronics stores... i did try making metal contacts myself that were pushed together by the gearstick as it hit the end of the gear leg... that didnt work at all... the contacts kept getting bended and wouldn't make contact, making me have to fix them all the time....
so i bought these switches, and screwed them under the top plate (the double H holed plate on top of the whole contraption)... you can see where they go on the picture
the little lever on the switch is positioned sideways under the top plate and works like a little gate that the gearstick pushes open when you engage a gear, the fact that they're not positioned on the ends of the gear legs lets ou push in the gears as hard as you want, since you won't be putting any extra pressure on the fragile switches.

after soldering the wires from the circuit board onto the switches, i had a prefectly functional USB gearbox!!!

hooray!, but what good is a stick shift if you can't clutch? now i needed to make myself a pedal...

the pedal would work the same way as the gears --by pressing on a switch that closes another circuit on the circuit board and sends a keypress to the computer...

so i built this little pedal using thick MDF plates, some more springs from that joystick, and yet another switch

to connect it to the pc, i used an RCA cable (the kind you find connecting your dvd to your TV set) to link it to the gearbox... i had previously left 2 wires hanging out unconnected in the gearbox waiting for the pedal to get built

i also needed to buy RCA female jacks, since these things can't be made, and the cable needs to be of decent quality so it won't short out and give unwanted keypresses all the time.

Oh, and that's not metal on the pedal base plate... it's just chrome spray paint ;)

after all was said and done, i had myself a little geabox-clutch pedal set ready to use on my pc... the only thing that was missing was a steering wheel :P

ironic, isn't it? after all this time building a gearbox, i was still playing TDU on the keyboard :p

well, i decided to literally not reinvent the wheel and went out and bought myself a pretty decent conventional wheel for 150 bucks (approx. 70USD)

and here's how it all turned out:

(yes i have a triple head 2 go )

adding up all expenses --the USB keyboard, the switches, RCA jacks and the wheel, i didnt spend much over 200 bucks on this (approx. 90 USD) and given the fact that a G25 came out for 1500, i think this was a pretty sweet deal :D

Cheers

HarvesteR