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jathames
05-27-2008, 07:59 PM
Is it a big deal how many ft. lbs the clutch is rated on the ztr's?? I was noticing the scag tiger cub is 250 lbs... the toro 175 and the exmark 200... just wondering??:confused:

bohiaa
05-27-2008, 09:27 PM
Dont know for sure But I too would like to see some lab results on this issue,

I would think it would be an issue if ya had helpers like mine who " NO MATTER HOW MANY TIMES I TELL HIM " enguage and dis. at full and some times idle,

Thanks for posting

mag360
05-28-2008, 01:22 AM
It's nice to have the extra strength in a component that is a real hassle to change out.

Richard Martin
05-28-2008, 04:39 AM
It's just the clamping force. The friction material is usually the same. In other words...

If it takes 5,000 cycles to wear out a Warner 175 pound clutch it will also take 5,000 cycles to wear out a Warner 250 pound clutch too.

JimQ
05-28-2008, 10:32 AM
Not necessarily true...

The 175 lb clutch will slip and take longer to engage/brake than the 250 lb clutch.

Bigger clutch equals less slip. That equals less friction material wear.

Light clutches give an nice smooth feel when you engage the blades because they slip. Heavy clutches generally pull the engine down more when the blades are engaged but last longer.

Q

Richard Martin
05-28-2008, 04:02 PM
So which does "Q" prefer?

JimQ
05-28-2008, 05:32 PM
I'll take a heavy clutch on mine. In the same conditions, they last longer.

Also, engage/dis-engage at 1/2 throttle, or as low an RPM as you can without the engine bucking/dying. It really does extend clutch life.

Q

bohiaa
05-28-2008, 05:35 PM
It's just the clamping force. The friction material is usually the same. In other words...

If it takes 5,000 cycles to wear out a Warner 175 pound clutch it will also take 5,000 cycles to wear out a Warner 250 pound clutch too.

Pls forgive me.... But what do you mean by cycles ?

surely Not 5,000 time enguage/dis ?

JimQ
05-28-2008, 05:57 PM
Yep. 1 cycle = 1 engagement & 1 dis-engagement.

5000 cycles isn't much. Our test requirements for a clutch range from about 16,000 for a consumer application clutch to as much as 90,000 for a commercial unit. This is at WOT with a simulated load on the blades.

Q

Richard Martin
05-29-2008, 11:12 AM
5000 cycles isn't much. Our test requirements for a clutch range from about 16,000 for a consumer application clutch to as much as 90,000 for a commercial unit. This is at WOT with a simulated load on the blades.

Q

Then this begs the question....

Why are there so many clutch failures long before either of those numbers in so many cases? I have a buddy of mine with a pair of Exmark Lazer Z's (I have a Dixie, it's not an issue) and he is putting clutches in at an average of 1,500 hours. Even at the 16,000 cycle number he would have to be cycling every 5.5 minutes. I can assure you that he is not. Every 15 minutes to 45 minutes is more the case. And they do attempt to keep the RPM's down when cycling.

And at the 90,000 cycle mark he would have to cycle at under a minute.

Even if you were to cycle ever 15 minutes the clutch should still last 22,500 hours. Huh?

lawnspecialties
05-29-2008, 11:24 AM
I admit, I feel very fotunate to have only had one clutch failure in my entire LCO business life.

One thing I really like on my Gravelys is the ability to engage the blades at idle speed. My Hustlers couldn't start them at anything less than half-throttle but my hp:decksize ration wasn't as big either.

JimQ
05-29-2008, 11:38 AM
Don't forget about the bearings in the clutch. More often, it's bearing failures than worn out friction material. It's also dependent on the operating environment, sand/dust, heat from the engine, How is it stored in the off-season, does it sit out in the rain, etc, etc...

We use a 40sec cycle time. 30sec engaged, 10sec dis-engaged. That equals 1000hrs run time. It's only an accelerated wear lab test. You're right, I don't know too many guys who cycle their blades that often.

Q

Richard Martin
05-29-2008, 01:43 PM
Don't forget about the bearings in the clutch. More often, it's bearing failures than worn out friction material. It's also dependent on the operating environment, sand/dust, heat from the engine, How is it stored in the off-season, does it sit out in the rain, etc, etc...

Q

Don't get me wrong. I'm not trying to give you a hard time, just trying to figure this out.

Since we do know that the clutch will fail due to other reasons long before the friction material wears out, even on a homeowner type clutch, then what difference does a stronger clutch make?

And...

What good is a lab test of these clutches when it is obvious that "in the field" use is showing completely different results?

This kinda harkens back to Exmark's factory testing of the Metro 26 that failed so miserably in real use or the problems that Stihl suffered with the BR600.

JimQ
05-29-2008, 02:58 PM
Since we do know that the clutch will fail due to other reasons long before the friction material wears out, even on a homeowner type clutch, then what difference does a stronger clutch make?

The first step it to decide what the minimum expected service life is for that component. That generally comes from the Product Managment team and derived from field feedback and warrenty data. Because the clutch is concidered a "wear item", our minimum expected service life for a commercial clutch is 1000hrs. Let's just say around 1/2 of the design life for the whole machine.

The requirements for every application are different. Use too light of a clutch and you will have friction material issues. The trick then is to find the least expensive clutch (generally lightest) that will meet the minimum expected service life.

Like just about every component on a Z, it's a balance between performance/durability and cost. This industry is so cost competitive. Nearly every Z manufacturer uses the same base components from the same suppliers. If manufacturer "A" put on a clutch that cost $100 more than the one on Manufacturer "B"'s machine, that might translate to a $300 difference in the sale price of the machine. Some end-users might recognize the value of the larger clutch and be happy to pay the difference. Others, the larger majority would not.

While the value of a larger clutch might seem obvious to most here, We have to remember, we're all enthusiasts. The rest are consumers who look at a Z as a commodity.

What good is a lab test of these clutches when it is obvious that "in the field" use is showing completely different results?

While I agree with your statement. I don't think it applies to this discussion. We have established a relativly close corolation to actual life in the field. I mentioned our minimum expected service life was 1000 hours for a clutch. You mentioned your buddy was replacing clutches at 1500 hours. That's a sucess in my book. It surpassed the minimum expected service life by 50% but not several hundred percent. That's good cost consience engineering. (BTW... not saying I work for eXmark)

I would love to see a manufacturer offer a "Super Duty" machine. The technology is out there, it's just expensive.

Take care,

Q

bohiaa
05-29-2008, 05:09 PM
thanks for the info Jim

TLS
05-29-2008, 06:36 PM
I would love to see a manufacturer offer a "Super Duty" machine. The technology is out there, it's just expensive.

Take care,

Q

So would I!!!

You guys were on to something with that monstrous deck you were fabricating last season!


As far as clutches go....I've only lost one that wasn't due to bearing failure. That was on my F-935. After several weeks of starting it up and putting it out by the street to sell, the internal pressure plate disintegrated and parts flew all over!

All my other failures were due to bearing wear. I have a post with pics of the clutch from my Lazer if you'd like to search. I popped the dust covers on the bearings and it was all powdery inside!

Richard Martin
05-30-2008, 04:49 AM
So what is needed then isn't stronger clutches. It's a clutch with greasable bearings.

But...

Overgreasing a clutch can be just as bad. If you get too much grease on the friction material it will render it useless.

But...

You could always set up the mower with an automatic greasing system like some heavy equipment has thereby eliminating any over or under greasing.

jathames
05-30-2008, 08:23 AM
so the question remains it is something you should consider when purchasing your ztr....

JimQ
05-30-2008, 09:53 AM
so the question remains it is something you should consider when purchasing your ztr....


I probably wouldn't put at the top of my list of things to consider when selecting a Z, but it would be on there somewhere. All other things being equal, go with a bigger clutch.

Strictly from a machine point of view - (not taking into consideration dealer support, cost, etc)

It's hard to decide which Z is best based on a spec sheet alone. Everyone uses the same components. Look at how the components are used.

Look at the hydro system. Most of the OEM's use the same components, Hydro-Gear pumps and Parker wheel motors (with a few exceptions.) Basic component specs won't tell the whole story. The important thing is how the OEM chooses to utilize those components. Is there:
Adequate cooling
Well designed oil reservoir/reservoirs with a large oil volume
Filtration
Appropriately size plumbing, (bigger is better)
Reliable plumbing/fittings.

Look at sub-system drives - Hydro drive and deck drive.
Spring loaded idlers with bearing pivot and large hardware. (or reliable slider - Hustler)
Long springs for consistent belt tension.
Quality name brand bearings with proper shielding
Large diameter idlers (slower bearing speed = longer life)
Low mis-alignment angle on deck belt. (or drive shaft)

Does it look like it's easy to maintain? If it's not, you probably won't.

And don't forget the deck. How does it cut in your conditions? The best deck in one location and grass type may not be the best in yours.

I'm sure I've left out a few things out, but the point is -
Most Z's are good machines that utilize quality components. but it's the way those common components are assembled that separate the great machines from the good ones.

Q

JimQ
05-30-2008, 10:01 AM
So what is needed then isn't stronger clutches. It's a clutch with greasable bearings.

But...

Overgreasing a clutch can be just as bad. If you get too much grease on the friction material it will render it useless.

But...

You could always set up the mower with an automatic greasing system like some heavy equipment has thereby eliminating any over or under greasing.

OR, how about a manual engagement system. Pretty low tech, but they're reliable. Would a manual blade engagement be the way to go or is that too much of a PIA now that we're all used to the convenience of pulling the big red button to make the blades spin?


Q

JimQ
05-30-2008, 10:07 AM
So would I!!!

You guys were on to something with that monstrous deck you were fabricating last season!

Hey TLS.

There have been several improvments and changes since then, but just yesterday, I mowed with something that you would recognize as related! I love this job!

Q

Richard Martin
05-30-2008, 12:58 PM
OR, how about a manual engagement system. Pretty low tech, but they're reliable. Would a manual blade engagement be the way to go or is that too much of a PIA now that we're all used to the convenience of pulling the big red button to make the blades spin?


Q

It's not a problem for me. I use a Dixie and the only improvement I could see them making to the system they have is to actually use bearings instead of bushings on the triangle plate. I haven't worn either of the two I've had out but Dixie has had some problems with them sticking. But then I guess if you won't grease a bushing you won't grease a bearing either.

TLS
05-30-2008, 10:31 PM
I love this job!

Q

I love your job! :cool2:

ed2hess
05-31-2008, 06:37 PM
Jim...would it be possible to replace a bearing on those clutches? My failures were all bearing....obviously you would have to catch it way before it gets to the fail point. Never had a failure on 6 Scags with heavy use, so maybe torque is important but I am guessing they have a bigger bearing than the lower torque units. Bet higher torque would help those guys that run doubles with high lift.

JimQ
06-02-2008, 11:06 AM
They stake those bearings in there pretty good. I think it would be tough to get them out without damaging the clutch.

Q


110562

110563

Richard Martin
06-02-2008, 02:47 PM
It sounds like they need to start using cir-clips instead. The only reason I can see to make the bearings non servicable is to sell more clutch assemblies. Kinda like those "permanently" greased spindle bearings some manufacturers sell.

There's only 2 things you need to remember about greasable spindle bearings.

1: You gotta do it at the recommended intervals and

2: This is probably more important than number 1. You can switch brands of grease but don't switch grease bases. I just switched from Sta-Plex grease to NAPA grease. Both are extreme pressure greases but most importantly, they're both lithium based.

JimQ
06-02-2008, 03:32 PM
There's only 2 things you need to remember about greasable spindle bearings.

1: You gotta do it at the recommended intervals and

2: This is probably more important than number 1. You can switch brands of grease but don't switch grease bases. I just switched from Sta-Plex grease to NAPA grease. Both are extreme pressure greases but most importantly, they're both lithium based.


Good advise. Everything leaves here with a Lithium Complex based grease.

There is a big difference in performance between different grease types.

Here's a good reference. http://www.bobistheoilguy.com/GREASE/index.htm

Q

cybervision
06-03-2008, 09:53 AM
Belt slippage could very well be the biggest cause of clutch failure there is. The amount of heat generated from a slipping belt is very high. The slippage does not even have to be that great to cause a problem. As the horsepower keeps going up so does the cutting loads. The decks are expected to handle more and more cutting and sometimes pushed to the point they are bogging down. Add in the fact that the drive belt is often running with water or wet grass on them this really increases the slippage factor. When the grease gets too hot it melts and tiny amounts start getting by the seals. Eventually there is not enough left in the bearings. This happens with High Temp Grease as well.

This relates closely to air-conditioning in our automobiles. Back in the days of V-belts auto mechanics were seeing a big correlation between compressor clutch failures and old worn out belts. Cars that came in with bad belts soon came back with blown clutches.

Belt maintenance is very critical. Make sure your belts are in good shape and the tensioners are free and working correctly. Change the $20 belt more frequently it is less than a new clutch. Cut your usual time in half or change every year. These belts are not working under ideal conditions and as they start getting older they loose gripping power.