dc motor speed control

The electric spout turner on my snowblower is blowing fuses...again.
I'm thinking of moving way on up in motor power and using heavy wire
from the battery and a reversing relay http://www.surpluscenter.com/item.asp?item=5-1720&catname=electric
http://www.surpluscenter.com/item.asp?catname=electric&item-3169-12
I can see this will slam the spout around - too fast. Also got way more torque than needed. OK for you EE types, what's an inexpensive way to slow it down. I've wore myself out looking for 10 rpm high torque motors - maybe somebody else knows where to look.
Karl
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On 02/13/2011 01:03 PM, Karl Townsend wrote:

I am not familiar with the way that the motor drives the spout on a snow blower, but I am picturing a roller chain sprocket or a ring gear around the outside of the spout. Could you do the speed reduction mechanically by changing the driving sprocket or gear size? If that is not possible, I can't think of a good cheap way to do it that would not reduce the torque so much to make it useless. A servo approach seems the most obvious but fails the cheap test. You might try putting something in series with the motor like an electric stove element or water heater element, but anything that heats has the undesired feature of increasing in resistance as the current requirement increases.
Mechanical limit switches on the spout and living with the fastest spout in town might be the cheapest option. The limit switches should control a relay in order to keep them a manageable (and cheap) size.
BobH from sunny Tucson
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wrote: . OK for you EE types, what's an inexpensive

Try looking at http://www.herbach.com/ They have a number of DC gearhead motors. Most may be too small for you, but worth taking a look.
Dan
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Karl Townsend wrote:

PWM DC motor drive.
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Karl Townsend wrote:

Looks perfect, assuming it's guaranteed to operate at your battery voltage.
I can vouch for PWM DC motor control - you can maintain full torque down to zero RPM - with a permanent magnet DC motor (which I'm ass-u-me-ing you have), the torque is proportional to the current. (not too sure about a series-wound, or "universal" motor, but I'm guessing it still applies.) I've designed and built a PWM motor speed controller, and it's pretty awesome to watch it maintain full torque at any RPM. This was only a 1.5 amp motor, but the same principle applies; buying one that somebody else has designed, built, and tested is obviously better than trying to klooge up something on your own, unless you're on a learning mission. :-)
Cheers! Rich
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How about using a car or better yet a truck windshield wiper motor with it's speed control? If the travel of the arm would not be enough for your requirements you could tap into it's rotary motion at the gearbox. Engineman

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On Sun, 13 Feb 2011 12:18:33 -0800 (PST), engineman

The output of virtually ALL wiper motors is totally rotary.
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Rich Grise wrote:

Fincor makes some dc motor controllers
John
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On Sun, 13 Feb 2011 10:39:35 -0600, Karl Townsend

Might the 1.5-second soft start feature drive you nuts? Looks good otherwise.
This one doesn't have the soft-start feature: http://www.electronickits.com/kit/complete/motor/CKMX068.htm
With two IRF1404 MOSFET's, this one should be about indestructable. Those parts are capable of a couple hundred amps each for as long as the heatsink can keep up.
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On Mon, 14 Feb 2011 02:19:54 -0600, Don Foreman

Thanks Don This one would be a better choice.
Karl
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On Mon, 14 Feb 2011 06:36:43 -0600, Karl Townsend wrote:

From google for MX068, I see that one reseller gets $30 more and one (electricsumo) gets $15 less than in the link above.
--
jiw

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wrote:

The reason the fuses are blowing is that the spout is too hard to turn. Maybe there is a geared speed reduction that is out of lube, or something like that. Might be worth taking a look before putting in a lot of effort to change out the motor.
Dan
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On Sun, 13 Feb 2011 13:00:44 -0800 (PST), " snipped-for-privacy@krl.org"

Duh. No shit. Works great when dry and lubed. Go out in -20 temp. and 40 wind snowstorm and it breaks. I've basically got the above mentioned wiper motor. I'm tired of fuzting with it. Give me more power Scotty.
I will shear pin it, but it needs to be able to crush ice on the gears.
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On 02/13/2011 05:03 AM, Karl Townsend wrote:

Gearmotor. DC motors tend to be fast, relatively low torque devices. A DC motor that was slow & high-torque would be a weird, huge, inefficient pancake.
--

Tim Wescott
Wescott Design Services
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I would personally look into why it happens, fixing the original problem may be the easiest approach.
i

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On Mon, 14 Feb 2011 08:12:09 -0600, Ignoramus9135

The problem is ice in the gears causing the gearmotor to overtorque and beak. This is the third time in 15 years. After looking at costs, I'm just buying a fourth small gearmotor for $60. It will last untill somebody else uses my blower again. ( I loan my unit out while I'm gone in return for keeping my driveway open) I know how to prevent it from breaking. Others don't.
Karl
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wrote:

There was a thread on using wax on snow shovels recently. May not help, but I do not see how it would hurt.
Anyway to put a shield to prevent snow from getting on the gears? Without seeing your set up, I am probably suggesting ideas that are worthless.
Dan
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On 02/14/2011 10:24 AM, Karl Townsend wrote:

You mentioned a shear pin...
Next time, instead of blowing the five gallons of gas onto your fuel dump, maybe you should sprinkle it on the road and light it off.
--

Tim Wescott
Wescott Design Services
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On Mon, 14 Feb 2011 12:24:50 -0600, Karl Townsend

Why not document the trick and pass it out with the machine during your vacation, Karl? A "You break it, you pay for it" clause is certainly optional, too.
Alternatively, take a $60 deposit for the duration.
-- Experience is a good teacher, but she send in terrific bills. -- Minna Thomas Antrim
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