Speaking of Snowblowers - This is Cool!

[MolaKule]

I have a New Poulan 2-stage snowblower.

I was blowing the snow tonight which was dry and very powdery.

The metal chute which directs the snow is sitting on a plastic turret fitting, so it is insulated.

While throwing snow I noticed a bright blue spark, about a half inch long, sparking between the outside of the metal chute and a close proximity peice of metal, a bracket. It only happened while snow was moving up the chute.

What the heck? Spark plug wire loose or what?

No, plug wire ok, not loose, not shorting.

Throw more snow, more bright blue sparks between the metal chute and adjacent bracket. Auger ok, everything working as it should, no binding no mechanical problem...Engine running great.

OK, this is too good for a physicist or mechanic to NOT investigate.

Anyone have a theory?

I have a theory but wanted to see if anyone else has observed this or has a theory as well.

Mola

 

[hate2work]

Probably static electricity, produced by the powder snow moving across the plastic turret.

 

[Joseph_S37]

Originally Posted By: hate2work

Probably static electricity, produced by the powder snow moving across the plastic turret.


This was my thought exactly, since you specifically added that it was dry snow

 

[MrMeeks]

This can only be an arc caused by high voltage leakage from the ignition.Have a look at the ignition coil and check for a missing ground wire/connection. That blue spark is high energy a yellow or red spark is low energy.a static discharge should not be blue.

 

[Shannow]

Given the amount of static that's generated from half a tonne of steam a second moving over my turbine blades, my guess is definitely on static

 

[Shannow]

Originally Posted By: MrMeeks
a static discharge should not be blue.

http://www.machinerylubrication.com/Read/998/varnish-formation

 

[JTK]

A weird one indeed. I'm still thinking some type of ignition leak, where maybe the arc of snow contacting the ground is acting as a ground? Then again, you'd think the engine would sputter while this was happening.

Joel

 

[Johnny]

This could only happen in Iowa. Let your wife blow the snow while you take video of this for us all to see.

 

[edhackett]

Come on over to my lab. I'll set you up with an 6 inch long, bright blue static discharge that will knock you across the room. That's just from alternating liquid and hydrogen bubbles flowing through a 1/8 inch Teflon tubing, the charge accumulating on a 5 gallon polyethylene carboy.

Ed

 

[MolaKule]

It has to be charge accumulation on the chute since the ignition is protected and it is running well, and it only occurs when snow is coming up the chute. No snow, no discharge.

I will try and get a picture of it next time.

I had a non-insulated vertical ham antenna in which a raindrop or snowflake would cause a "pop" or snap in the receiver until I placed a static discharge trap in line.

I knew from meteorology that raindrops and snowflakes carried charges but this was down right spectacular. And moving charges constitute a current as well. I calculated about a 75kV potential must be present to do this.

We have an environmental testing lab in which we routinely discharge HV to the avionics cabinets and wiring. It's really wild to watch with the lights out.

 

[Samilcar]

I was reading about the "Children's Blizzard" of 1888, and came across this tidbit:

"That blizzard was so intense, that surface friction with the strong wind and snow created so much static electricity, that stove pipes/chimneys were electrified in the storm creating sparks and glowing in the atmosphere. This phenomenon is generally referred to as St. Elmo’s Fire and creates hissing and sparking sounds. This of course, created fear and anxiety for many settlers that had never experienced such an event."

The snow during this blizzard was of the dry, powdery type.

 

[engineerscott]

Yeah, static build-up can definitely create sparks with enough energy to make a blue discharge. I've seen medium sized Van de Graaf generators make ~6 inch blue sparks and they are based on friction generated static charge.

I think you've hit the nail on the head in associating it with very dry powdery snow. I've heard of helicopters generating some fairly spectacular discharges when flying through dry powdery snow.

 

[AaronDaMan]

This definitely isn't a static build-up guys. Here's the problem and the solution:

I have a Poulan 2-stage snow blower and had the exact same problem – a half in long blue spark arching between the metal shute and the main part of the snow blower. It only sparked when the auger was activated, and sparked continuously. I took the panel off the left side (unscrewed 6 bolts near the throttle lever to remove panel). Once inside I looked around and found a black wire that had rubbed itself raw against a sharp piece of molded sheet metal that was attached to the engine. Alas this was passing the current into engine frame and snow blower body. I re-insulated this section of wire with some heat proof tape and it solved the problem. Hopefully this will help someone else in the future with the same problem.

Note to self: don’t every buy a Poulan again – these things are cheap and poorly made. I had used my blower for less that 3 hours before it started spewing blue sparks.

 

[MolaKule]

Quote:
It only sparked when the auger was activated, and sparked continuously.


Did it spark continously or ONLY when the Auger was activated?

That wasn't my situation.


All the wiring in my unit is neatly tucked inside the case with no abrasions, no contact, and no close proximity wiring. The engine ran too well for it to be an ignition related problem.

And of course it only happens when the Auger/impeller is activated cause this is the only time snow is going up the chute. The Auger/impeller is activated by a mechanical linkage and has nothing to do with the ignition system.

And, this never occurs with wet snow and when blowing snow in high humidity.

Quote:
Alas this was passing the current into engine frame and snow blower body


Then you should have had ignition and rough running engine problems, since this wire come from the magneto and when grounded kills the engine.

Quote:
these things are cheap and poorly made.


I guess beauty is in the eyes of the beholder since my opinion is that it is well engineered and well built.

 

[Rick in PA]

From what you describe: static electricity. I'm surprised nobody used the fancy word triboelectrification, i.e. rubbing stuff together to separate electric charges. The snow flowing over the metal chute will charge it. The chute has a capacitance with respect to the machine frame (I'd guestimate some tens of pF). The charge keeps building until POW it snaps over (with a half inch spark gap (I'd guestemate on the order of 20 kV). After it arcs over the charge should be substantially (but not completely) removed. Then the cycle repeats itself. BAP BAP BAP... The arc frequency should be relatively proportional the volume of snow flowing through the chute.

This is definitely a cool problem. Surprisingly, water is NOT conductive, it's the polar contaminates (e.g. trace salts) that render water conductive. One of the more interesting work related things I've seen is Teflon being extruded into a distiled water cooling bath emerging from the cooling bath with a full electrostatic charge. Snow is basically crystallized distilled water, I never thought about it, but snow should be insulative, and that would be why the snow could 1. deposit charge on the metal chute and 2. not form a charge leakage path over the plastic.

The manufacturer should probably use a carbon loaded (or electrically conductive) plastic. That would eliminate the problem. It probably just never occurred to them they could have a static problem.

You could add a flexible ground lead between the chute and machine frame to eliminate the problem (but something tells me that wouldn't be practical, the chute probably moves too much).

As a side note, sometimes I get a repetitive discharge to my hands when I'm operating a gas powered push vac I have during the summer. Same principal, debris flowing through the vac charges it, the plastic handle lets the voltage build-up a bit, then it discharges through me, pop pop pop, to ground.

Anyway, that's my take on the problem.

 

[Turk]

Originally Posted By: Rick in PA
From what you describe: static electricity. I'm surprised nobody used the fancy word triboelectrification, i.e. rubbing stuff together to separate electric charges. The snow flowing over the metal chute will charge it. The chute has a capacitance with respect to the machine frame (I'd guestimate some tens of pF). The charge keeps building until POW it snaps over (with a half inch spark gap (I'd guestemate on the order of 20 kV). After it arcs over the charge should be substantially (but not completely) removed. Then the cycle repeats itself. BAP BAP BAP... The arc frequency should be relatively proportional the volume of snow flowing through the chute.

This is definitely a cool problem. Surprisingly, water is NOT conductive, it's the polar contaminates (e.g. trace salts) that render water conductive. One of the more interesting work related things I've seen is Teflon being extruded into a distiled water cooling bath emerging from the cooling bath with a full electrostatic charge. Snow is basically crystallized distilled water, I never thought about it, but snow should be insulative, and that would be why the snow could 1. deposit charge on the metal chute and 2. not form a charge leakage path over the plastic.

The manufacturer should probably use a carbon loaded (or electrically conductive) plastic. That would eliminate the problem. It probably just never occurred to them they could have a static problem.

You could add a flexible ground lead between the chute and machine frame to eliminate the problem (but something tells me that wouldn't be practical, the chute probably moves too much).

As a side note, sometimes I get a repetitive discharge to my hands when I'm operating a gas powered push vac I have during the summer. Same principal, debris flowing through the vac charges it, the plastic handle lets the voltage build-up a bit, then it discharges through me, pop pop pop, to ground.

Anyway, that's my take on the problem.


Good one! I know that arena too, but not as well as you...

Get & spray some Staticide and see if it goes away.

 

[eljefino]

I had a McCullough string trimmer bought new that the first summer I used it, the spark plug boot leaked enough electricity to zap my elbow down my arm to my trigger finger.

Stupid me, I was sweating at the time.

I guess putting a guard over the engine was too much for them.

 

[MolaKule]

I thought about writing Poulan and letting them know about this discharge and that my pacemaker skips a beat or that my muscles twitch when this happens.

If it appears the paint is being burnt I will use one of those narrow braided grounding straps to make the chute the same potential as the frame.

 

[Rick in PA]

Originally Posted By: tpitcher


Good one! I know that arena too, but not as well as you...

Get & spray some Staticide and see if it goes away.


Staticide's a good suggestion. Static Guard is a readily available anti-static spray. It could take a couple of applications over time to get enough build-up but it should work. Good thought.