bishbosh Posted May 15, 2011 Author Share Posted May 15, 2011 Nice find nightrain! Wouldn't mind seeing how that cylinder goes together. Anyone care to buy one to find out...? OK, so I have progressed a bit, mainly due to acquiring this: which came with 20 end mills (including several unused Dormers :D) and this vice: so, for the price I paid for it all, the machine itself was almost free!! I have added a rotary table with chuck which transforms the mill enabling shapes like this to be formed very easily: That is the (now trial piece ) cylinder for the steering. I have also made the end cap (also a trial ) Hopefully next time I'll tighten the chuck enough and drill the right size holes for the end cap bolts! (drilled them as clearance holes instead of ready to be tapped M3.... oops!) Still, it is all good practice. It was extremely satisfying to drill the six bolt holes and get the drill to drop straight into the first hole at the end of the cycle Only downside is the mill is imperial and I have no concept of what a thousandth of an inch is so I created a conversion chart and stuck it to the wall. I am now lusting after a 3 axis DRO kit but I'll have to save my pennies for a bit first as they seem to command a fair price. Quote Link to comment Share on other sites More sharing options...
Night Train Posted May 15, 2011 Share Posted May 15, 2011 Nice find nightrain! Wouldn't mind seeing how that cylinder goes together. Anyone care to buy one to find out...? I'm wondering about dropping hints at the girlfriend but her birthday is in a few weeks and mine is months away. The pressing thing is finding someone to make a white gold (not plated) jubiliee clip as a ring for her. Her idea to have one, but I want to surprise her. You need to start putting a 20p next to your work to get an idea of scale. Quote Link to comment Share on other sites More sharing options...
simonr Posted May 16, 2011 Share Posted May 16, 2011 Only downside is the mill is imperial and I have no concept of what a thousandth of an inch is so I created a conversion chart and stuck it to the wall. 40 thou to a mm is close enough - no wall chart needed! Si Quote Link to comment Share on other sites More sharing options...
A Twig Posted May 17, 2011 Share Posted May 17, 2011 So let me get this straight before I start properly thinking about it all. Is it: 1) You want a system which will activate a motor in one direction or the other. Once the input controlling it is released you effectively want it do do the exact opposite and return the wheels to center? Or: 2) You want the turns to be proportionate to how far forward or backward the lever is operated, and then do the reverse. e.g. pushing the controller lever half forward does 2 revs, all the way does 4 revs, irrelevant of how long you hold it at that position, then upon release it self-centers? Cheers Quote Link to comment Share on other sites More sharing options...
bishbosh Posted May 17, 2011 Author Share Posted May 17, 2011 Mr Twig - My aspiration is the second one, but at the moment I have kind of shelved the fancy idea and am going to try a couple of large servos first. Of course, don't let me stop you designing away! Quote Link to comment Share on other sites More sharing options...
simonr Posted May 18, 2011 Share Posted May 18, 2011 There is another solution - which I don't think has been considered yet. Fabricate a mechanism using a big motor, hydraulics, whatever to move the wheels. Connect a flexible Beldon cable (like a bicycle brake cable) between the axle & wheel so the cable is pulled in & out as the steering moves. Connect the other end of the flexible cable to a block which can slide side to side in response to the steering movement. This can be inside the cab, somewhere dry. On the block, mount two micro-switches with a small gap between the switch operating levers. Connect one switch to run the motor in one direction and the other to run it in the opposite direction. Simple electrical connection - no electronics. Mount a little RC servo to the body such that the servo's arm sits between the micro switch operating levers. When the RC servo moves one way, it closes one switch. The motor moves the steering which pulls the beldon cable and moves the sliding block & micro-switches in the direction the RC Servo moved. When it has moved far enough, the microswitch has moved out of the way of the servo arm, switches off, motor stops and leaves the wheels pointing in a direction proportional to the movement of the RC Servo. If the steering 'chatters' back & forth, increase the gap between the microswitch operating levers. This is essentially how direct drive electric power steering works on a car. The nice thing about it is you can make most of the bits yourself. You could use a window-winder motor to move the wheels as they are low geared and have a lot of grunt. You could even dispense with the hydraulics and use a flexible control cable direct from the motor to the wheel. Then mount the microswitches directly on the big motor. If this isn't very clear - let me know & I'll draw it! Si Quote Link to comment Share on other sites More sharing options...
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