Reconditioning mowing deck

[clueless 2,976]

How do you know what rpms your running, do you have a tach? Doubt you were running 4,000, these engines are designed to run at 3,600 rpms at wide open throttle. If you running more than that then back it down. If your on a level surface the deck should be level right to left, an 1/8 to a 1/4 inch lower in the front than the back. Until you get it adjusted close to how it supposed to be you are going to have some form of cutting issue, maybe not much but some. 

[porschpow 7]

I was going by the tachometer on the dash board. It looks like around 4k is the "redline". So, than that case, I can stay around the 3600 rpm's. I guess the deck is level left to right. I don't even know how you would adjust the left to right.

Is there a proper (go to) way to adjust the front to back?  DO you measure the blade? The deck?...?

[cleat 5,909]

To level the deck then put the blades facing front to rear then measure the front edge of the most forward blade and the rear edge of the most rearward blade to the floor.

You must be on a nice level surface for this.

I like to check this at the normal height that I cut at.

I then rotate both blades 180 degrees and recheck just in case a blade is bent.

 

To check side to side then repeat above except place the blades sideways.

To level side to side I would think you would need to twist the main shaft that the wheels bolt to (never had to do this on a Wheel Horse deck).

 

The 44" deck on my 17-44 can be levelled side to side and front to back but my regular 42, 48, and 60" decks have no easy way to adjust side to side.

 

I bought one of these to measure cut height.

 

Cleat

 

[clueless 2,976]

If you have a John Deere dealer near you they usually carry one of those cutting height measuring devices in Cleats post, just yellow not blue. I think it's the best way to take the guessing out of adjusting any riding mower deck. It will tell you if your deck is level, your blades are level front and back, left to right, if your deck is warped, a blade is bent, a spindle is longer than the other. You can get them online cheap. If you do your own deck work, get one .

[lynnmor 7,303]

I bought one of the blue height gages shown above.  The base of it was so warped that you could get any reading you want.  I put screws in the four corners of the base to calibrate it.

 

RPM should be adjusted at the governor so that the maximum is 3600 RPM.  If you can throttle up above that, adjustment is necessary.  Cheap hand held tachometers can be bought for under $20 online.

[gwest_ca-(File Mod) 11,039]

3 hours ago, porschpow said:

 

19,200 feet per minute??? How does that convert to RPM?

 

A 48" deck uses a blade that is 16-1/16" tip to tip which is 1.3385 feet long.

One revolution of the blade tip = diameter times pi or 1.3385 feet x 3.141592 = 4.205 feet of travel.

Maximum 19,200 feet per minute divided by 4.205 feet in one revolution of travel equals maximum 4,566 rpm of the spindle.

 

A common walk-behind mower with a 21" blade running at 3,492 rpm gives the maximum 19,200 feet per minute.

A common walk-behind mower with a 20" blade running at 3,667 rpm gives the maximum 19,200 feet per minute.

 

Garry

[Sarge 3,463]

If your deck is leaving unmowed strips - it's usually from the deck being partially plugged or just trying to mow too fast. Clean deck and keeping the ground speed to where the deck is discharging in a smooth flow is key - do not allow it to discharge in "chunks", the result is a crappy looking job. For places that have gotten out of control - I make 1-2 passes at transport height, then start at the top of the deck's range and run a cross pattern 90* to the last mowing to chew the clippings up as much as possible. There will become a point that it's too much and the clippings must be removed - I picked up a tow behind blower/vac last year and that really helps in the spring growth spurt here. I have two large areas that will grow like crazy regardless of the summer weather - one is a natural drainage ditch that carries it's own water just below the surface, it always needs to be mowed at least once a week despite some long-term droughts we've had, hence the addition of the vac unit.

 

I'd love to see some averages of blade rpm across various models of WH decks - while there is a maximum, I'm certain most models (especially older) are far less than that.

Has anyone ever actually measured the effective rpm of the spindles while running?

 

Sarge

[stumplifter 9]

Spindle drawing posted in the pinned Some Drawings thread.

[cleat 5,909]

Just for grins I checked the speed of my 48" deck on a 520HC.

 

With engine at 3600, deck turns 3700 according to my hand held tack.

 

Since the 48" deck has 16" blades that works out to a tip speed of 15,498.5 ft/min.

 

I guess that is why it is so quiet compared to the newer mowers.

 

Cuts just fine at that speed and the blades need to be sharpened.

[oliver2-44 9,725]

On my 42” SD deck I went from the original 6” wheels to 7-1/2” wheels to get a little more height.  Works good!