slowing an electric motors rpm down but still retain torque! Like in . drill type 1 is late model and plastic and has variable rpm capability acomplished by depressing the trigger less or more etc. At low/slow rpm you can grab the drill chuck with your mit and stop the drill. Drill type 2 belonged to your oldman who in turn scored it off his oldman. It too has variable speed governed from the go trigger but if you tried to grab this bad boy - you'd break your wrist if you held on. Whats the go there! Both looked to be of similar size. I am conducting an initial look/see to determine the most cost effective way to spin a wheel rim between the rpm range of say . 0.5 - 5 rpm. Advice . suggestions. Unbeatabull . you know about this sorta stuff (electric motors) aye!
trader_84,
Dec 3, 8:07am
Further to the above . the electric motor/drill/whatever will be driving through a reduction gearbox. Around a 30:1. I intend to experiment yada yada.
m16d,
Dec 3, 9:09am
If you only want half a rpm, you could use a hamster.
beno,
Dec 3, 9:17am
Its called pulse width modulation PWM and is commonly used on modern cars. Basically you turn the motor on and off quickly. you can make the timer yoursef. have a look on youtube
intrade,
Dec 3, 9:50am
what do you need this for ! i got some motors with variable speed they are heavy duty small gearbox to just rotate a pulley with potentio meter wired for variable speed.
splinter67,
Dec 3, 9:56am
At a guess he is widening wheels and needs to weld them but dose not want to weld them on his new lathe
trader_84,
Dec 3, 11:24am
Yep, what splinta said. I want to cobble up something that will spin a rim at welding speed. A mate suggested a sewing machine motor and also a MIG Welder wire feed motor as being possible candidates. I'm trying to get an initial understanding of electric motors because I don't really have a good grasp of what makes them tick and . wonder why Variable Speed Drive/Controller thingies are so expensive on TM.
the-lada-dude,
Dec 3, 11:41am
you can use a light dimmer switch, but there are draw backs to this idea. one is not over loading the dimmer unit, two is it may be unwise to use it on induction motors = overheating of the motor, dimmer maybe ok on motors with brushes,you will be far better off using a small reduction g/box at say 25:1 and use old bicycle sprockets and chain. and use the dimmer as a fine tunei have some lada rims to modify, you can practise on those, OK !
intrade,
Dec 3, 11:45am
i just started it the slowest it will go is 45 secounds for 1 rotation and fastest is lets see. 2 secoundsfor 1 rotation at full speed
the-lada-dude,
Dec 3, 12:02pm
Ahhh, i just realised what you need sonny jim, is a thingy called a stepper motor. they come in different sizes,cheap as chips ( in fact they use them in all sorts of throw away stuff, like photo copiers I think ) and the control units are simple electronics. MRFIXIT will sort u out
bitsy_boffin,
Dec 3, 12:45pm
Variable speed controllers (Variable Frequency Drives) are used to control (mostly) 3-phase AC motors,probably not what you want there.
PWM (Pulse Width Modulation) would be typically used for a DC motor, where by the power is literally switched on and off at high frequency, the ratio of "on" time to "off" time determines how much power you're giving the motor (eg if it's off 50% of the time, you're giving 50% of the power, if it's off for 90% of the time, it's only getting 10% power, as long as you switch it on-off fast enough, it all smooths out to human perception (and the motor's perception for that matter)).But at such slow speeds as you need I don't know how well it would work. might be ok.A 555 timer a-stable circuit (google it) with the output driving a fairly high current mosfet's base, with the source and drain connected between the drill battery negative terminal (assuming battery drill here) and the drill's negative input would allow you to test it anyway.
A stepper is another idea, but, if it's a one-off job, well, you'd have to make a microprocessor control system for it - a stepper has several inputs which need to be fired in the correct sequence, each firing causes a "step" which is a small amount of rotation (say a degree or so), between each step the coils for the previous step are still active and holding motor's position, they can give high torque with high precision, but not necessarily high speed relatively speaking.
Of course, some sort of gear/belt/wheel reduction setup would probably be best, run the drill at a good speed, reduce it to lower speed.But you might have to have quite a few stages of reduction I suspect, drills are quite fast, and you want quite slow.
trader_84,
Dec 3, 1:04pm
Thanks for this boffin. Yep the need for reducing/reduction. I have a small-ish 30:1 reduction gearbox and can score a flex plate or two with matching starter motor wheels. I have seen one in a welding shop in town that they made based on a wiper motor fitted with a small diameter V pully. This drove a larger V pully that was mounted on a shaft. Mounted on this same shaft was a starter motor gear. This inturn drove a flex plate. The flex plate was attached to a lathe chuck and they just held the work to be welded in the chuck and went at it. Hanging off the wiper motor was this box thingy. This is where my lack of electrical nouse and understanding puts me behind the 8-ball. The box thingy had the On/Off switch plus a dial that made the wiper motor speed up and slow down. Oh yeah . plus even though it was a 12V wiper motor . it still was plugged into the wall and ran off (I guess) 240 house current. The whole lot was mounted in a frame and seemed to work well. I talked to the guy that built it (it was built in house) and he said he had to f**k around heaps to get the right speeds. But yes - I want one.
elect70,
Dec 3, 1:53pm
Simplest i& cheapest s DC motorlike windscreen wiper motor&vaiable resistancegivespeed from 0 to full
the-lada-dude,
Dec 3, 2:02pm
work out the speed you want the wheel to turn, then estimate the electric drill speed at medium revs in low gear this will give you the overall gear ratio u needsay the wheel has to turn at 1 revolution in 3 minutes and your drill is running at about 150 rpm then the ratio is 450 :1 but thats the overall ratio, which can be made up of reduction box of 30:1 and another reduction of 15:1 ( maybe the flexi plate/ pinion idea )
jmma,
Dec 3, 2:03pm
The old cake mixer can go slow (o:
splinter67,
Dec 3, 2:05pm
Thats not a nice thing to say about the mrs
mrfxit,
Dec 3, 2:37pm
This guy^^ ^ that has 1 already .Mmmmm talk to him again & see if he will let you "time" the revolutions of his jig. Pop a rim in it/ set it up for the ideal welding speed/ mark a spot & start the drive AND a stop watch at the same time. That will give you a "real time" suitable final drive revolution bench mark to work from. Sometimes you need to start at the end to find the beginning
mrfxit,
Dec 3, 2:38pm
LOL . Love it .
aredwood,
Dec 3, 8:35pm
My idea, start with a windscreen wiper motor. join on a starter motor pinion gear, get an old (but still working diff), lock it, weld a flex plate to the input shaft. Bolt down the diff and wiper motor to something solid so the gears mesh. Then bolt your wheel to the diff. Use resistors to vary the voltage going into the wiper motor or try powering it off a battery charger with a 6V or 12V switch on it and trying the slow speed and fast speed wires on the wiper motor.
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