Question About Opening In Deck @Spindles
 

2003 Z-Force 44 3-high lift blades.
I'm curious if this opening behind my spindles. Is it by design or to fit another type of spindle?
Once in a blue moon a sweet gum tree pod will escape here and take a trip around a pulley courtesy the belt.

Thanks

http://alcphoto.net/mower/new_deck.jpg

Those let the air come up through to create better vacuum.

Really. I'm skeptical. Convince me.

I don't know if that is what the MTD Engineers were thinking, but as a HVAC/R Technician, sounds plausible to me.

Same here... At some point a deck can only move so much air. I think of a fan with the back side of the guard covered. Can't move much air that way. Maybe they figured out that allowing some air in through there made it possible to create more air flow.

The air needs to flow out the discharge. If it flows up out the top of the deck, it would spit grass out up there too.

My thinking was it is pulling air in from those holes.... Like a venturi
Think maybe Dale meant down through not up

That's one way to look at it.

Since the wing on the blades pushes air upwards, creating a vacuum below them.... I'm not sure how that would work, or help. You want the air to flow through the grass and under the edges of the deck. If air is introduced from above, it would cancel the vacuum affect below. That would kind of defeat the purpose, would it not? Am I the only person who thinks this stuff through? Come on. Both you guys are smart guys.

I have thought it through some.
First thing I thought of is air in the deck needs to moves in two directions. Vertically, and horizontally. The wings of the blades are on the outer most part. The hole we are looking at is close to the shaft. Think of a tornado. The outer part spins and pushes away like crazy yet its the inner part that becomes a vacuum.

I had a deck similar to that in the way that there were openings. I never had to clean them out. They always seemed to remain open. I never thought much of it honestly till this question came up. But now I sort of feel like they must pull air in.

Edit. Small holes would not "cancel" the vacuum I don't think. It would change the draft certainly tho.

One final thought on this.
I think this has been a good constructive conversation and would like to bow out before it turns for the worse. So my final thought is this. I'm guessing the engineer that designed this has more knowledge of how this should work than any of us here. I doubt that the holes were meant to just get get clogged up with grass and do nothing. I also looked at some spindles from some othe high vac decks and saw that there were openings where they mounted to the decks also. There's definitely some reason for this design and I think it has everything to do with vacuum

all of the ones I have mowed with do push grass up through those holes [especially dry grass] that's why the top of the deck is always covered with grass . if the pulley gaurds are in place they're usually plugged solid from not being cleaned out

Ok. so air is pushing up from there. Do you use with mulching cover on or side discharge open? I am actually reading one of the patents right now for this design.. Its a long read tho lol.

Hmmmmmm...... so air isn't sucked in from the top through those holes. Who would have thought that? :bigthink:

How about someone who has this type of deck hold a piece of paper near the opening while running the mower. The deflection of the paper will indicate air flow direction.

Seems that is the case in this situation.. I never mulched with mine and those vents stayed clear. With the mulching cover in place I assume there would have to be air pushing out. I didnt think of the mulching cover until I started looking at the patent docs this morning.

Jon, Perhaps I was thinking of this backwards. Do you think with a mulching cover in place that those vents may be necessary to create the vacuum? In other words, If the deck was sealed shut would it create as much flow as it would with out some sort of vent like the ones in question? Does the deck work as efficiently once those holes become plugged up?