Outdoor Power Equipment (Lawn Mowers, Snow Blowers, Chain Saws and more) Discussions

Look carefully at the picture below. Notice the little black bands on the auger shaft between the blades? Also notice there are no bars on the end supporting the blades?

Apparently MTD decided at some time, I'm not sure when, to use individual auger blades. Each blade mounts on its on section of the shaft and is held by its on shear pin. Now it gets fun.

On the 28" there are 4 auger blades and they are separated from each other. On the 26" the edges are right next to each other. On the 24" they overlap. The 30" have 6 auger blades and they really overlap.

Now say one section snags a rock or other obstruction and jams. It shear pin breaks; so far all is good. On the 28" that is fine. On the 30", as the remaining blades turn the one or two adjoining blades overlap the edge of the fixed bladed and continue turning, the blades grinding into each other, the paint grinding away, until the other shear pins also break.

How long has MTD been doing this? Is this an accurate description or did I miss something?  I tried it the store, removing the shear pin, and the blades definitely run hard into each other.

First, augers move pretty slow, there isn't a lot of energy from the auger to disipate. On the 28" with 2 blades per side the blades are independant. On the 30" the overlap; if one locks and breaks its sheer pin the the blade will run into it and also sheer. That is after it grinds into the first. Then the third into the second. The 26" the edges just barely overlap; within production tolerances one way or another. The 24" overlaps. But the 30" is the worst.

The augers themselves end up pretty solid. Don't open centers work better?

It is less expensive to build. One part covers all the augers, left and right, for all their snow blowers.

Looking at those augers --they are stamped (and heat treated for hardness I imagine). The concave of the thin solid auger gives it strength... If it was open center it would allow snow (very little) to work through... If they were open, they would have to be much thicker to have the same strength... Friiy

friiy wrote:
This is exactly the same thing I was thinking.   I used to work on a project in the automotive industry, contacts and bus bars that were designed symmetrical and able to be scaled up depending on customer requirements.  Flexible and saves a lot of money on tooling.

Another thing I notice that these stamped auger parts are fairly lightweight for their strength.  Lightweight is good because the supporting pieces, ie auger shafts, bearings/bushings can be lighter duty/cheaper as well, and it all propagates throughout the machine. 

DavidNJ wrote:
When I was looking at these units some time ago, I did notice the overlapped blades too.  I couldn't see how they deal with it from slapping to the next blade when the shear pin breaks.

These stamped auger blades seems to have a lot more surface area than a standard helical auger.  Because of this, the auger speed can be reduced and achieve the same performance.  There's more options to shape the stamped blades to fine tune the performance.  A lot of opportunities for designer to get creative here.

It is hard to say open center auger or stamped blades augers perform better, probably dependent on the snow condition.  But with either design, the goal is to compact the snow slightly so that it has some "critical mass" so it can move easily through the impeller and chute, but not too much compaction that is too thick and heavy to be ejected.  Maybe that's why the stamped auger blade moves slower, it already has more surface area.  That's my theory and I'm sticking to that unless someone comes up with something better.  :)

Why do you think they are designed to create compaction? Wouldn't the impeller would do that. The augers are slow moving, they break up the snow with their serrated edges, then move it to the center.

A solid auger can cause the snow to compaction between the auger revolutions jaming the auger.

Ariens, the B&S brands (Simiplicity, Snapper, Deere), Toro, and my older MTD have open centers. The Wisconsin Engineering SF1330 has an open center and serrated edge on both sides. Husqvarna has pictures both ways for the same model; I have no idea what they are currently do.

I think some compaction is good.  Light powdery snow could use some compaction, otherwise, they just swirl around.

Yeah... just rolls around like a snow globe..

Friiy

When there is sufficient mass it will compact from the shovel effect of the scoop.