Bobcat Deck for my Horse

[Bill D 1,926]

After seeing the @kpinncthread where he modified an Exmark deck for use under a wheel horse, it made me want to try it.  I picked up this 48" Bobcat deck.  So far I have  removed the two outer pulleys and flipped them over so they will drive off the bottom groove of the center pulley.  I can modify the original deck belt tensioner to work with the new belt configuration.  I plan to keep the original pulleys.  They are 6" and the wheel horse deck has 5".  The blades are the same length.  To compensate I plan to run the PTO belt in the smaller outer groove.  Thoughts?  

Debating whether or not to cut the front point on the deck.  This deck had no front baffles like the Exmark deck.  Also thought about welding in a front baffle and hiding anti scalp wheels underneath in the  gap.  Thoughts?  If I chop off the front point how will air flow be affected?  Progress will be slow as this is new territory for me.  Please be patient.  Thanks.

Edited August 9, 2021 by Bill D

[kpinnc 12,087]

That deck looks almost identical to mine!

 

If the deck pulleys are larger than the PTO, the deck pulleys run slower. Using the smaller PTO groove even more so. 

 

I purposely went with smaller deck pulleys (4 inch) to increase the blade tip speed. Then I used the smaller groove because the larger one seemed too fast. 

 

Good luck with the build. I look forward to seeing how you set it up!

Edited August 11, 2021 by kpinnc

[Bill D 1,926]

I started playing with it today.  I got the deck belt tensioner figured out.  I have to space the front mounting bracket up about an inch to clear the center pulleys.  How this is going to affect fitment under the tractor is unclear.  My spindles are different than the Exmark spindles on the  @kpinncbuild.  My deck carriage is different than his as well.  I plan to extend the deck leveling arm and use a gauge wheel setup from a 42" deck.  All plans subject to change.

[kpinnc 12,087]

I think the longer slot on the deck hanger (where the tractor lift arm connects) is going to be a welcome change from the one I used. The slot on my hanger was about half as long, and getting the deck fitted with it was not fun. 

 

Your mock up looks great so far!

[Bill D 1,926]

8 hours ago, kpinnc said:

I think the longer slot on the deck hanger (where the tractor lift arm connects) is going to be a welcome change from the one I used. The slot on my hanger was about half as long, and getting the deck fitted with it was not fun. 

 

Your mock up looks great so far!

Thanks.  Based on pictures I found it looks like your deck hanger originally came off a rear discharge deck.  I wonder what kind of difference that may have made, vs using the deck hanger from a 42" side discharge deck.  It looks like I'm going to be forced to change the pulleys to get proper blade speed for the Gator blades.  Still trying to figure out the gauge wheel setup.

Edited August 11, 2021 by Bill D

[kpinnc 12,087]

1 hour ago, Bill D said:

Based on pictures I found it looks like your deck hanger originally came off a rear discharge deck.  I wonder what kind of difference that may have made, vs using the deck hanger from a 42" side discharge deck.

 

Dang! Good eye there!

 

My hangers available were from a 42 RD and a 48 from a D series. The RD had a longer slot, so I went with that.

 

Can you move that right side double pulley to the middle? Using the smaller drive pulley might get you closer to the RPM you're looking for- without replacing them all. Might be worth a try anyway.

 

 

Edited August 11, 2021 by kpinnc

[ronhatch 406]

Forget the gage wheels and go with a full length roller like Simplicity has. I converted all my decks over to rollers which makes for  smoother mowing and also makes my lawn look like a ball field.

 

[Bill D 1,926]

9 hours ago, kpinnc said:

 

Dang! Good eye there!

 

My hangers available were from a 42 RD and a 48 from a D series. The RD had a longer slot, so I went with that.

 

Can you move that right side double pulley to the middle? Using the smaller drive pulley might get you closer to the RPM you're looking for- without replacing them all. Might be worth a try anyway.

 

 

The right pulley is flipped over.  That's a brake drum for the original blade brake setup.  Gives me an idea though,  I may be able to swap the left and center pulleys and stack a 4 inch pulley on top.  Thanks.

Edited August 11, 2021 by Bill D

[Bill D 1,926]

2 hours ago, ronhatch said:

Forget the gage wheels and go with a full length roller like Simplicity has. I converted all my decks over to rollers which makes for  smoother mowing and also makes my lawn look like a ball field.

 

Do you have a pictures of this mod?  Not a bad idea.

 

[Bill D 1,926]

Does anyone have a blade tip speed calculator formula I could use?  I plan to use 4" pulleys on the deck and the blades are 17" long.  I may run the PTO belt in the outer groove if needed.  Thanks.

[8ntruck 7,016]

Tip speed formula:

 

Blade diameter (in inches) x 3.14 (pi) x RPM = tip speed in inches/minute 

[Handy Don 12,235]

This is a sample of a spreadsheet for calculating what's happening with the mower given the engine speed, the pulley diameters, and the blade lengths. The extra stuff is really just nice wrapping around @8ntruck's basic formula.

 

Yes, I went a little overboard to accommodate having each spindle driven by the deck belt have a different pulley size and blade length.

I used some basic values as a sample to test the formulas.

 

Input Values
3300	Engine RPM (A1)
5	PTO Belt - Engine Pulley Diameter (A2)
4	PTO Belt - Deck Pulley Diameter (center top) (A3)
5	Deck Belt - Deck Pulley Diameter (center bottom) (A4)
15	Center Blade Length (A5)
4	Deck Belt - Deck Pulley Diameter (left side) (A6)
14	Left Blade Length (A7)
4	Deck Belt - Deck Pulley Diameter (right side) (A8)
14	Right Blade Length (A9)
Results		Formulas
4,125	Center Blade RPM (A12)	A1 x A2 ÷ A3
16,199	Center Blade Tip Speed (feet per minute) (A13)	A12 x 3.14 x A5 ÷ 12
5,156	Left Blade RPM (A14)	A4 ÷ A6 x A12
18,899	Left Blade Tip Speed (feet per minute) (A15)	A14 x 3.14 x A7 ÷ 12
5,156	Right Blade RPM (A16)	A4 ÷ A8 x A12
18,899	Right Blade Tip Speed (feet per minute) (A17)	A16 x 3.14 x A9 ÷ 12
	Replace the variable A1, A2, A3, etc. with its corresponding input value in each formula to do the calculation

 

Edited August 14, 2021 by Handy Don

[8ntruck 7,016]

 @Handy Don - check your units on the tip speed.  I think your mean feet pre minute, not feet per second.

 

16199 feet per second is 11,044 mph!  This would be one loud mower with a tip speed of about mach 15.  

 

16199 feet per minute is 184 mph.

[Handy Don 12,235]

5 minutes ago, 8ntruck said:

 @Handy Don - check your units on the tip speed.  I think your mean feet pre minute, not feet per second.

 

16199 feet per second is 11,044 mph!  This would be one loud mower with a tip speed of about mach 15.  

 

16199 feet per minute is 184 mph.

Could I do the whole lawn in 1 second flat?

Yep, wrong units. Thanks. Fixed now.

 

[kpinnc 12,087]

You're safe to 21,000 fpm. Typical zero turn commercial mowers average around 18,000 fpm. Brings all new importance to the deflector guard IMO.

 

4 inch pulleys on my deck mod running the small groove of the PTO is around 15,000 fpm. That of course is calculated at 3600 rpm on the engine, and I haven't run it that hard yet. So long as your engine has the torque to maintain the load of the deck in high grass, around 3k on the engine is plenty.

 

That's still around 12,000 fpm. For reference, the clippings get thrown about 12-15 feet. It's an entirely different mowing experience from what you may be used to. 

 

Just don't mow up close to things on the discharge side. 

Edited August 14, 2021 by kpinnc

[Bill D 1,926]

I made a little progress today.  I cut everything off the the top of the deck that I don't need.  I got most of the steel pieces cut to fabricate the mounts and gauge wheel parts.  I removed all the spindles.  At least one may need a rebuild.  I'm using a gauge wheel bar from a 48" deck.  It will be modified to work on this application.  The height adjuster will be mounted on top of the deck and connected to the gauge wheel bar with a rod and heim joints.  At least that's the plan for now.

Edited August 15, 2021 by Bill D

[kpinnc 12,087]

That's looking great! I like how you spaced those brackets over where the baffles meet the outer shell. Should be the strongest spot on the back of the deck!

[Bill D 1,926]

48 minutes ago, kpinnc said:

That's looking great! I like how you spaced those brackets over where the baffles meet the outer shell. Should be the strongest spot on the back of the deck!

Thanks.  I am on concerned that once the gauge wheels are on the deck, it will be very hard to get under the tractor without removing a wheel.  Time will tell.  I've also thought about adding two more supports next to the rear anti scalp wheels due to the weight of the deck.

[Handy Don 12,235]

1 hour ago, Bill D said:

Thanks.  I am on concerned that once the gauge wheels are on the deck, it will be very hard to get under the tractor without removing a wheel.  Time will tell.  I've also thought about adding two more supports next to the rear anti scalp wheels due to the weight of the deck.

With a deck that sturdy, maybe look at the old JD system of driving over the deck to get it underneath!

[Bill D 1,926]

More progress today.  I made the height adjuster out of a broken lift bar.  Everything is still being mocked up.  I discovered that I will not be able to use 8" front wheels on my tractor with this deck as they will rub the deck, unless I cut the deck...

[Handy Don 12,235]

20 minutes ago, Bill D said:

More progress today.  I made the height adjuster out of a broken lift bar.  Everything is still being mocked up.  I discovered that I will not be able to use 8" front wheels on my tractor with this deck as they will rub the deck, unless I cut the deck...

 

 

520 swept front axle upgrade?

 

One other thought...

On the recent WH decks the fore-aft leveling and the height adjustment rely on the parallel geometry built into the lift frame. Its cool that you are using that for you project, but your fabricated attachments will have to maintain it. 

Edited August 15, 2021 by Handy Don

[Bill D 1,926]

3 minutes ago, Handy Don said:

520 swept front axle upgrade?

No.  I don't have the money for that right now.

[Handy Don 12,235]

Duplicate post. Apologies.

Edited August 15, 2021 by Handy Don

[8ntruck 7,016]

8 hours ago, Handy Don said:

With a deck that sturdy, maybe look at the old JD system of driving over the deck to get it underneath!

I was having that exact thought today as I was changing from my SD deck to my RD deck.

 

[Horse Newbie 7,075]

On 8/11/2021 at 5:29 PM, ronhatch said:

Forget the gage wheels and go with a full length roller like Simplicity has. I converted all my decks over to rollers which makes for  smoother mowing and also makes my lawn look like a ball field.

 

How about a pic or two ?