Ideal Blade Tip Speed?

[dfrisk]

GERRY - The parts look-up shows the mule drive for my 982/50C is $56 if I remember right. Mine's starting to fray a bit. Need to get a spare...soon!

KEN - My advice on an all hydro mower, get the highest efficiency pump & motors you can find, carry a L-O-T of oil, BIG alum. tank, and the more steel tubing you can run the better, and maybe look at automotive oil coolers plumbed into the return lines with an elec. fan sucking air thru it.

Years ago I looked at a LAND PRIDE pull type three deck gang mower to pull with one of my Farmall's. Think they made 9, 11, and 14 foot versions. When I was told the "Used one" was $25,000 I became quickly uninterested. Doesn't look like they even make them anymore.

ANYHOW, I did find this useful info for you on Land Pride's site describing their hyd. mower decks for use with skid steer loaders.
http://www.landpride.com/ari/attach/lp/public/specs/326-025s.pdf

 

[kweaver]

Dennis - $25K ! We gave $28K for our 15 foot Bush Hog bat wing AND MF 2675 all new ! ... of course that was around 1983.

Seems the only thing that gets heavier built today is the price tag ............................

 

[dfrisk]

KEN - this was in about '94-'95. The mower was actually kinda neat. Set-up just like a batwing, ran with 540 rpm PTO, and a single 2-way remote controlled mowing height, and raised the three individual 3-blade decks into transport position. The cart had one deck behind, and one on either side. The one I saw and priced had been used by the city to mow parks, school grounds, etc. for two years.

Would have worked a LOT better behind something like a 300/350 International utility tractor w/LPTO & 2-3 remotes.

Thought it was interesting on that spec sheet that all mowers zeroed in so close to that 19,000 ft/min blade tip speed.

Years ago I worked for a couple summers for a local seed corn company rouging seed corn fields and detasseling. (Miserable work, especially in mud!) But they had 6 cutter detasselers. Kinda like the high-boy sprayers common now, and had three pairs of two cutters, hyd. driven blades inside a cut-up section of 55-gal. drum. Had the cutiest little V-4 Ford industrial engine & 4-speed transaxle for power. And I know how much you love Ford's, but these things were water-cooled, and about the size of a Kohler KT17 or Onan engine, had a governor like a farm tractor, held whatever RPM was set, which mostly was WFO. Probably around 90-100 CID, and 50 HP. The hyd. pumps they ran to power the cutters were HUGE.

I'm sure there's a couple sitting around the back lots of seed corn plants in the midwest rusting away that could be bought for scrap price and converted into mowers. I forget the brand they were, seemed like John Blue since they were blue w/Yellow trim. Here's a picture of one, except ours didn't need no stinking cab! How you going to work on your FARMER tan inside a cab?!?!? http://en.wikipedia.org/wiki/Fileetasseling_machine_in_field.jpg

 

[kide]

KentucK:
And I was really high in the barn, too... (putting in a garage door opener...)

All hydraulic decks... Case - Ingersoll - whatever.... used (may still use ) hydraulic motor powered decks.

 

[Ronnie Sellers]

Mornin' Fellas,

The other day there was some discussion on the main board about the cutting quality of various mower decks. It was suggested by some that the Crapsman deck cut very well. So what makes a mowing deck better than another - is it cutting blade design, blade tip speed or what?

I pondering this (as it continues to rain) with my coffee this morning & I decided to try to determine the cutting blade tip speed on my 42" IHC mowing deck. Now those of you way smarter than me please review my (likely) mathematical errors, and if so, PLEASE point it out to me.

Ok, here goes --
Things I assumed:
My 12HP Kohler will be run at the recommended full throttle crankshaft speed of 3600 rpms.

The PTO is directly connected to the crank. The mechanical PTO pulley (driver) is 4 3/8” (4.375") in diameter. So it is also turning at 3600 rpms.

The (driven) pulley on the top, center of the deck is 6 ¼” (6.25”) in diameter.
So: 4.375/ 6.25 = 0.70
3600 x 0.70 = 2520 rpms

Now, the sheave below the top center deck pulley which is being driven is 7-1/8” (7.125”) in diameter. It is turning at the same rpm as the sheave above it, 2520 rpms.

The center pulley drives the two outer blade pulleys, which are only 3” in diameter.
So, the driver pulley is 7.125” @ 2520 rpms.
7.125 / 3.0 = 2.375
2520 x 2.375 = 5980 rpms

Assuming my above math is correct, it's interesting to note that the two outer blades turn at nearly twice the speed of the center blade......

Blade tip speeds:
The center spindle is driven 2520 rpms. The center blade is 22” long, so this is equivalent to a pulley 22” pulley. The circumference is the distance around the imaginary 22" pulley. So, Circumference (C) = Diameter (D) x Pi (3.1416)
C = 22" x 3.1416
C = 69.11”

So, the center 22” blade tip is making a 69.11” trip with every rpm =
69.11" x 2520 RPM = 174,157 inches per minute.
174,157 / 12"/ft =
14,513 feet per minute (FPM).

The two outer blades are 10.75” long or equivalent to a 10.75” pulley.
10.75” x 3.1416 = 33.77” circumference
33.77” x 5980 rpms = 201,944 inches per minute
201,944 / 12 =
16,829 feet per minute (FPM).

So, again, assuming my above math is correct, then we've determined that my 42" IHC deck cuts grass with spindle speeds of 2600 to 6000 rpms and produce blade tip speeds of 14K to 17K FPM.

First off, is my math correct?

Secondly, I KNOW modern mowing decks have a higher blade tip speed. Does anyone know just how fast do they go?

Does anyone know what the blade tip speed of a Crapsman deck is? If not, if someone would provide some engine rpm and sheave diameter measurements here, we'd be able to calculate them for discussions sake.....

Thanks for any and all input, opinions, & discussion!
Ryan Wilke View attachment 5271

Good afternoon Ryan.
I have a 1973 I H CC with a 38 inch 3 blade mower deck that I'm trying to speed up the blades .
The deck blades just doesn't turn fast enough like the newer style mowers.
How could I get the blades spinning faster without redesigning the deck ,lol
Center blade is 20 inch long and the 2 outer blades are 10 inch .

Center double pulled with the top pulley smaller than the bottom .
Any information would be greatly appreciated.
Thanks Ronnie.

 

[mgwin]

Ronnie,
How did you find a 13 year old thread? Look at the date of the previous post above yours.
As far as speeding up the deck, I don't think you need to. They were not designed to turn like today's mowers.
I had an old Snapper riding mower that would mow anything. It had something like a 30 inch deck, and turned slow compared to today's mowers. It made a beautiful cut though. Almost looked like a push mower had mown the yard.
If you haven't already, sharpening the blades will help a lot with your cut.

 

[-CӞ]

Ronnie,
How did you find a 13 year old thread? Look at the date of the previous post above yours.
As far as speeding up the deck, I don't think you need to. They were not designed to turn like today's mowers.
I had an old Snapper riding mower that would mow anything. It had something like a 30 inch deck, and turned slow compared to today's mowers. It made a beautiful cut though. Almost looked like a push mower had mown the yard.
If you haven't already, sharpening the blades will help a lot with your cut.

+ relatively slow ground speed and a reasonably elevated deck… for some reason old mowers were designed with a few “scalp it” deck height settings, before turf science caught up with “cut it high” guidance for hardier turf & better moisture management.

 

[Ronnie Sellers]

Ronnie,
How did you find a 13 year old thread? Look at the date of the previous post above yours.
As far as speeding up the deck, I don't think you need to. They were not designed to turn like today's mowers.
I had an old Snapper riding mower that would mow anything. It had something like a 30 inch deck, and turned slow compared to today's mowers. It made a beautiful cut though. Almost looked like a push mower had mown the yard.
If you haven't already, sharpening the blades will help a lot with your cut.

I was just looking through the post and found this one
My deck does a good job of mowing but was think if the blades were spinning faster it wouldn't pull the engine down as fast with that momentum.
I know there use to be a speed up pulley for the later model Cubs but haven't run across one for the smaller 38 inch .
I've actually thought about mounting a small flywheel on the top of the center pulley. But haven't venture out that far yet.
Thanks for the reply.

 

[mgwin]

The engine shouldn't bog down while mowing unless it is tall grass. Wondering if you may have other issues. If you took the deck pulley belt off of the deck, you could check each spindle for bad bearings.
You could also try greasing the spindles and see if that helps. Also check underneath and make sure there is nothing wrapped around the spindles. I had to clean kudzu strands out from around my weed eater head yesterday.

 

[Ronnie Sellers]

The engine shouldn't bog down while mowing unless it is tall grass. Wondering if you may have other issues. If you took the deck pulley belt off of the deck, you could check each spindle for bad bearings.
You could also try greasing the spindles and see if that helps. Also check underneath and make sure there is nothing wrapped around the spindles. I had to clean kudzu strands out from around my weed eater head yesterday.

Yes sir I keep the spindles greased the blades sharp and the underside of the deck gets cleaned after each mowing.
I have a model 86 cub cadet I actually delivered to the folks that purchased it new in 1974 when i worked for an International Harvester Dealer and in 1994 was traded in and I purchased it .
I rebuilt the engine with all new parts and actually found a old stock new crankshaft for the K181 Kohler.
The cub has been taken care from the original owner and I've done the same .
The little 8 hp engine has 1100 hrs on it as I speak and doesn't use any oil between the 50 hr services.
I just tuned her up last month with new points , condenser , coil , plug and a new external resister that saves the points from burning out to quickly.
The speed up pulley was just something I wanted to try .

 

[tkhoffman]

Ronnie,
How did you find a 13 year old thread? Look at the date of the previous post above yours.
As far as speeding up the deck, I don't think you need to. They were not designed to turn like today's mowers.
I had an old Snapper riding mower that would mow anything. It had something like a 30 inch deck, and turned slow compared to today's mowers. It made a beautiful cut though. Almost looked like a push mower had mown the yard.
If you haven't already, sharpening the blades will help a lot with your cut.

AND make sure the blades are facing the correct way. Soo many times people accidently put blades on upside-down.

 

[rjruchti]

Ground speed has a lot to do with the quality of cut. Forget those stupid JD commercials. Don't try and mow your lawn like a golf green. 2" is short enough. Add that to what several other have mentioned and you will probably get along just fine. Good luck.

 

[mgwin]

Unless you have golf course grass, it don't need to be that low. Around here, regular grass is mown around 3" to help keep it from burning up in the summer heat. When it gets hot, I usually raise mine up to 3-1/2" or 3-3/4."
Takes a lot of time and money to have a lush lawn. I do not have either.