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Discussion Starter · #1 ·
Kinda surprised this topic hasn't come up before with people's propensity to tinker and make things go faster.

  1. Anyone know what the mower blade tip speed is for the 60D at full 2100RPM PTO speed? I can find no specifications for this listed anywhere, and no intel on any forum. I see one post indicating it may be about 16,000fpm from a 3000 series manual. There's one JD page that advertise some other variants of the 7-Iron decks at 18,000fpm, but I don't believe that includes the 60D.

  2. Overdrive pulley suggestions for the 60D? Not sure where to begin since there doesn't seem to be anyone who's done this and talked about it. Seems to me a larger pulley on the gearbox would increase the belt drive speed. Not sure how to calculate how much larger = how much faster. I would like to bring the blade tip speed up closer to 18,000, especially if a simple pulley swap is all it would take.

The benefits of this are rather obvious. Better cut quality in tougher cutting conditions within the limits of available horsepower. Additional benefit is using a lower engine RPM to achieve a similar cut quality in less difficult cutting conditions. If I can run the tractor at 2500-2600 engine rpm and achieve the same blade tip speed I currently get at wide open throttle, that's a significant savings in fuel and noise reduction. When the grass isn't super heavy and tall, this will probably work pretty well.

The gearbox pulley is this: John Deere Gear Case Drive Pulley - AM144674
Code:
AM144674 SPECIFICATIONS
Belt Section  HB
Diameter      5.724 IN
Groove Width  0.563 IN
Angle         34
Bore Size     0.984 IN
Key Width     0.00 IN
Length        0.673 IN
Is there a not-terrible way of locating a pulley matching specs with just a larger diameter?
 

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I’m guessing they have some engineering involved in these decks, if you speed things up I wouldn’t do much. It might over stress something, such as pulley bearings or spindles.
 
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Early 2017 Vintage 1025R TLB (260/H120)
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A few items to consider:
Additional heat at new speeds.
Blades need to be thoroughly balanced (the nail method isn't sufficient).
With a deflector up/off - projectiles from underneath will be even more threatening.
Will fuel usage be lower at a lower RPM with a high load compared to WOT? (Not an expert on Diesels, so not sure here - I know gas engines have a point at which low rpm high power is less fuel efficient and higher rpm high power is better on fuel economy) - Is this potential savings enough to justify the expense?

It's a cool idea - Following to see where this goes!
 
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Mach 1 is 67,520 feet per second. What will happen then?

 

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1025r with Mauser cab.
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I know the zero turn commercial mowers have a maximum blade tip speed of 19,000 fpm, which works out to roughly 210 mph of blade speed. This is set by ANSI (American National Standards Institute) who regulates the maximum speed to 19,000 fpm speed, which by the way is limited to a 60" mower or smaller (actually, the limit is to each blade being 20" in length or less....).

Spinning the blades faster can cause stresses and metal fatigue which can lead to failure when the blades impact "normally encountered obstacles" in the course of mowing. There are a number of factors which go into this including the effect on objects struck by the mower as well as the damage it would do to the mower components and possibly operator or those nearby.

Actually, depending upon the grass being cut, the 19,000 FPM blade speed is too fast and the speed needs to be reduced to achieve the optimal cut.

You have to be a member of ANSI to read the materials, but you can see the table of contents for the Commercial Mower Report without being a member. They get into virtually every standard on the mowers. Here is a screenshot of the page when you search "Lawn Mower Blade Speed" and you can access the PDF to read the table of contents.

Product Font Line Rectangle Screenshot
 

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dunno about the advisability of speeding up the blades....I do get a better cut running higher rpm using the gator g5's under my 60d.....that said, the increase in tip speed is straight math as a percentage of drive pulley change : so change a 7" pulley to an 8" = 8/7 = 1.142 * existing tip speed....14.2% in this case ....15k fpm goes to 17.1k fpm........IF you could get bigger pulley in there & properly tension the belt(s)
 

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Discussion Starter · #8 ·
Mulch kit, so no discharge. But duly noted it does increase the impact forces. However, lots of mowers operate at 18-19k fpm without leaving a trail of death. If the 60D is already operating at 16k, I don't buy that there some increased risk of death and injury going 18k instead. If you're going to be killed by something from the 18k, you'd be just as dead with it at 16k.

As for the mechanical stress, I'm sure that could be an issue. Without knowing the engineering decisions behind it, it's impossible to know what reasons certain specs were selected. It could be engineered to handle it just fine and other factors set the RPM where it is. Or it could be known to explode at 18k.

Also something to consider is lower engine RPM reduces the hydraulic hydrostatic efficiency which could damage transmission parts as opposed to saving fuel
If the transmission gets damaged by running less than wide open throttle, then JD made a huge mistake putting a throttle lever on the machine. I don't believe there is any merit to this concern. People drive around at less than wide open throttle doing work all day every day. It's perfectly fine.
 

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Mulch kit, so no discharge. But duly noted it does increase the impact forces. However, lots of mowers operate at 18-19k fpm without leaving a trail of death. If the 60D is already operating at 16k, I don't buy that there some increased risk of death and injury going 18k instead. If you're going to be killed by something from the 18k, you'd be just as dead with it at 16k.

As for the mechanical stress, I'm sure that could be an issue. Without knowing the engineering decisions behind it, it's impossible to know what reasons certain specs were selected. It could be engineered to handle it just fine and other factors set the RPM where it is. Or it could be known to explode at 18k.


If the transmission gets damaged by running less than wide open throttle, then JD made a huge mistake putting a throttle lever on the machine. I don't believe there is any merit to this concern. People drive around at less than wide open throttle doing work all day every day. It's perfectly fine.
Agreed about RPM. If the lower speeds were an issue....... anyway...

I have begun cutting at 2600 or 2700 engine RPM and have noticed an appreciable fuel savings. What surprised me is the cleanliness of the deck has more to do with the cut than does the engine being at PTO speed. Deck cleanliness is much more important.

john Deere 1025R
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I went through this process for my 455, 60 deck. I recommend buying a cheap laser tachometer. I did and checked my engine rpms then my blade spindle rpms. That way you can calculate the blade tip speed very easily and gets rid of the guesswork. On the 455's (and possibly the 1025's as well) the pto speed is the same and the deck gearbox is exactly the same with all the different decks. Since the smaller decks have shorter blades JD has to achieve roughly the same blade tip speed somehow. Turns out the way they do is is to use slightly different diameter pulleys on the gearbox to belt output for the pulley that runs the belt for the blade deck. I calculated the blade tip speed I would get using the pulley from a 54" deck (which is slightly larger diameter) and it was right where I thought I wanted it so I purchased the pulley for a 54 deck from the auction site and put it on my 60 deck. Did not even have to change the belt, just adjusted it. So that is how to do it at least for my 455. You can easily check it out for your 1025 by looking up the specs for the pulleys on 60 and 54 decks.
So didn't take me long to change back to the original pulley ... not much difference in cut and the deck used noticeably more horsepower than before. Also more vibration. It has been several years and I am still running the original pulley.
 

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Discussion Starter · #11 ·
Omg I have an optical tachometer sitting in my box of drone parts I used to test motor RPM. I will set that up later to test the 60D.
 
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