dc motor speed control

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

On Feb 13, 8:03=A0am, Karl Townsend wrote: . OK for you EE types, what's an inexpensive

Try looking at

Dan

PWM DC motor drive.

like this one?

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

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.

=20 Dan

The output of virtually ALL wiper motors is totally rotary.

Duh. No s*it. Works great when dry and lubed. Go out in -20 temp. and

I will shear pin it, but it needs to be able to crush ice on the gears.

Fincor makes some dc motor controllers

John

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.

Might the 1.5-second soft start feature drive you nuts? Looks good otherwise.

This one doesn't have the soft-start feature:

Thanks Don This one would be a better choice.

Karl

I would personally look into why it happens, fixing the original problem may be the easiest approach.

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

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

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

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.

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

Letting other people use your stuff is the surest way imaginable of seeing to it that your stuff gets trashed. I've lent out tools and various items, and they came back broken in ways that I never could have imagined they could have got broken in the first place!

Good Luck! Rich